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Sample records for particle reinforced polymers

  1. Nano polypeptide particles reinforced polymer composite fibers.

    PubMed

    Li, Jiashen; Li, Yi; Zhang, Jing; Li, Gang; Liu, Xuan; Li, Zhi; Liu, Xuqing; Han, Yanxia; Zhao, Zheng

    2015-02-25

    Because of the intensified competition of land resources for growing food and natural textile fibers, there is an urgent need to reuse and recycle the consumed/wasted natural fibers as regenerated green materials. Although polypeptide was extracted from wool by alkaline hydrolysis, the size of the polypeptide fragments could be reduced to nanoscale. The wool polypeptide particles were fragile and could be crushed down to nano size again and dispersed evenly among polymer matrix under melt extrusion condition. The nano polypeptide particles could reinforce antiultraviolet capability, moisture regain, and mechanical properties of the polymer-polypeptide composite fibers.

  2. Assessment of microcapsule—catalyst particles healing system in high performance fibre reinforced polymer composite

    NASA Astrophysics Data System (ADS)

    Bolimowski, P. A.; Wass, D. F.; Bond, I. P.

    2016-08-01

    Autonomous self-healing in carbon fibre reinforced polymer (CFRP) is demonstrated using epoxy resin filled microcapsules and a solid-state catalyst. Microcapsules filled with oligomeric epoxy resin (20-450 μm) and particles of Sc(OTf)3 are embedded in an interleave region of a unidirectional CFRP laminate and tested under mode I loading. Double cantilever beam (DCB) test specimens containing variable concentrations of microcapsules and catalyst were prepared, tested and compared to those healed by manual injection with corresponding healing resin formulation. The healing efficiency was evaluated by comparing the maximum peak load recorded on load-displacement curves for pristine and healed specimens. A 44% maximum recovery was observed for specimens containing 10 wt% of solid phase catalyst and 11 wt% of epoxy microcapsules. However, a significant (80%) decrease in initial strain energy release rate (G IC) was observed for specimens with the embedded healing chemistries.

  3. Carbon Nanofiber Reinforced Polymers

    DTIC Science & Technology

    2006-01-01

    2006 2. REPORT TYPE 3. DATES COVERED 00-00-2006 to 00-00-2006 4. TITLE AND SUBTITLE Carbon Nanofiber Reinforced Polymers 5a. CONTRACT NUMBER 5b...REVIEW Carbon Nanofiber Reinforced Polymers J.N. Baucom, A. Rohatgi, W.R. Pogue III, and J.P. Thomas Materials Science and Technology Division...of mass-produced and inexpensive, discontinuous carbon nanofibers to create a percolated fiber network within a polymeric matrix that will result in

  4. Self reinforcing polymer composites

    SciTech Connect

    Kenig, S.

    1993-12-31

    In the advent of liquid crystalline polymers (LCPs), self reinforcing polymer composites comprising a polymer matrix and an LCP reinforcement, have become a reality. The so called self reinforcement is due to the LCPs orientability characteristics resulting from their rigid molecular backbone and anisotropy structure in the fluid state. Orientation development takes place during melt processing of the LCP composite blends where shear as well as elongational flows occur prior to consolidation to the solid state. By proper flow control anisotropy develops and in-situ composites are obtained. Polymer composites comprising self-reinforcement by LCPs during processing induced flow, were analyzed and studied with respect to their orientation development and resultant mechanical properties. The analysis commenced with the hydrodynamics of immiscible fluids in shear and elongational flows. Based on the analysis, orientation and morphology development in capillary extrusion was studied, using a variety of thermoplastic polymer matrices like amorphous and crystalline polyamides, polycarbonate and polyester in conjunction of a naphthalene based thermotropic LCP. Based on the flow-morphology relationship the amorphous polyamide/LCP composite was further investigated as it exhibited enhanced properties. Laminated composites based on LCP/amorphous polyamide were developed composed of unidirectional extruded and drawn sheets that were subsequently compression molded. Unidirectional, +45/{minus}45 and quasi-isotropic laminates were prepared and analyzed as to their microstructure and mechanical properties.

  5. Finite element analysis of the effect of an interphase on toughening of a particle reinforced polymer composite

    PubMed Central

    Wang, Wenhai; Sadeghipour, Keya; Baran, George

    2008-01-01

    A numerical method was used to study the interaction between a crack and the filler phase in a particle-reinforced polymer composite. The simulation was achieved by implementing a progressive damage-and-failure material model and element-removal technique through finite element analysis, providing a framework for the quantitative prediction of the deformation and fracture response of the composite. The effect of an interphase on composite toughness was also studied. Results show that a thin and high strength interphase results in efficient stress transfer between particle and matrix and causes the crack to deflect and propagate within the matrix. Alternatively, a thick and low strength interphase results in crack propagation within the interphase layer, and crack blunting. Further analysis of the effect of volume fraction and particle-particle interactions on fracture toughness as well as prediction of the fracture toughness can also be achieved within this framework. PMID:19492012

  6. Spatial Gradients in Particle Reinforced Polymers Characterized by X-Ray Attenuation and Laser Confocal Microscopy

    SciTech Connect

    LAGASSE,ROBERT R.; THOMPSON,KYLE R.

    2000-06-12

    The goal of this work is to develop techniques for measuring gradients in particle concentration within filled polymers, such as encapsulant. A high concentration of filler particles is added to such materials to tailor physical properties such as thermal expansion coefficient. Sedimentation and flow-induced migration of particles can produce concentration gradients that are most severe near material boundaries. Therefore, techniques for measuring local particle concentration should be accurate near boundaries. Particle gradients in an alumina-filled epoxy resin are measured with a spatial resolution of 0.2 mm using an x-ray beam attenuation technique, but an artifact related to the finite diameter of the beam reduces accuracy near the specimen's edge. Local particle concentration near an edge can be measured more reliably using microscopy coupled with image analysis. This is illustrated by measuring concentration profiles of glass particles having 40 {micro}m median diameter using images acquired by a confocal laser fluorescence microscope. The mean of the measured profiles of volume fraction agrees to better than 3% with the expected value, and the shape of the profiles agrees qualitatively with simple theory for sedimentation of monodisperse particles. Extending this microscopy technique to smaller, micron-scale filler particles used in encapsulant for microelectronic devices is illustrated by measuring the local concentration of an epoxy resin containing 0.41 volume fraction of silica.

  7. Micromechanical analysis of a hybrid composite—effect of boron carbide particles on the elastic properties of basalt fiber reinforced polymer composite

    NASA Astrophysics Data System (ADS)

    Krishna Golla, Sai; Prasanthi, P.

    2016-11-01

    A fiber reinforced polymer (FRP) composite is an important material for structural application. The diversified application of FRP composites has become the center of attention for interdisciplinary research. However, improvements in the mechanical properties of this class of materials are still under research for different applications. The reinforcement of inorganic particles in a composite improves its structural properties due to their high stiffness. The present research work is focused on the prediction of the mechanical properties of the hybrid composites where continuous fibers are reinforced in a micro boron carbide particle mixed polypropylene matrix. The effectiveness of the addition of 30 wt. % of boron carbide (B4C) particle contributions regarding the longitudinal and transverse properties of the basalt fiber reinforced polymer composite at various fiber volume fractions is examined by finite element analysis (FEA). The experimental approach is the best way to determine the properties of the composite but it is expensive and time-consuming. Therefore, the finite element method (FEM) and analytical methods are the viable methods for the determination of the composite properties. The FEM results were obtained by adopting a micromechanics approach with the support of FEM. Assuming a uniform distribution of reinforcement and considering one unit-cell of the whole array, the properties of the composite materials are determined. The predicted elastic properties from FEA are compared with the analytical results. The results suggest that B4C particles are a good reinforcement for the enhancement of the transverse properties of basalt fiber reinforced polypropylene.

  8. Reinforcing Silk Scaffolds with Silk Particles

    PubMed Central

    Rajkhowa, Rangam; Gil, Eun Seok; Kluge, Jonathan; Numata, Keiji; Wang, Lijing; Kaplan, David L.

    2014-01-01

    Silk fibroin is a useful protein polymer for biomaterials and tissue engineering. In this work, porogen leached scaffolds prepared from aqueous and HFIP silk solutions were reinforced through the addition of silk particles. This led to about 40 times increase in the specific compressive modulus and the yield strength of HFIP-based scaffolds. This increase in mechanical properties resulted from the high interfacial cohesion between the silk matrix and the reinforcing silk particles, due to partial solubility of the silk particles in HFIP. The porosity of scaffolds was reduced from ≈90% (control) to ≈75% for the HFIP systems containing 200% particle reinforcement, while maintaining pore interconnectivity. The presence of the particles slowed the enzymatic degradation of silk scaffolds. PMID:20166230

  9. Process for preparing polymer reinforced silica aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Capadona, Lynn A. (Inventor)

    2011-01-01

    Process for preparing polymer-reinforced silica aerogels which comprises a one-pot reaction of at least one alkoxy silane in the presence of effective amounts of a polymer precursor to obtain a silica reaction product, the reaction product is gelled and subsequently subjected to conditions that promotes polymerization of the precursor and then supercritically dried to obtain the polymer-reinforced monolithic silica aerogels.

  10. Nanoscale Reinforced, Polymer Derived Ceramic Matrix Coatings

    SciTech Connect

    Rajendra Bordia

    2009-07-31

    The goal of this project was to explore and develop a novel class of nanoscale reinforced ceramic coatings for high temperature (600-1000 C) corrosion protection of metallic components in a coal-fired environment. It was focused on developing coatings that are easy to process and low cost. The approach was to use high-yield preceramic polymers loaded with nano-size fillers. The complex interplay of the particles in the polymer, their role in controlling shrinkage and phase evolution during thermal treatment, resulting densification and microstructural evolution, mechanical properties and effectiveness as corrosion protection coatings were investigated. Fe-and Ni-based alloys currently used in coal-fired environments do not possess the requisite corrosion and oxidation resistance for next generation of advanced power systems. One example of this is the power plants that use ultra supercritical steam as the working fluid. The increase in thermal efficiency of the plant and decrease in pollutant emissions are only possible by changing the properties of steam from supercritical to ultra supercritical. However, the conditions, 650 C and 34.5 MPa, are too severe and result in higher rate of corrosion due to higher metal temperatures. Coating the metallic components with ceramics that are resistant to corrosion, oxidation and erosion, is an economical and immediate solution to this problem. Good high temperature corrosion protection ceramic coatings for metallic structures must have a set of properties that are difficult to achieve using established processing techniques. The required properties include ease of coating complex shapes, low processing temperatures, thermal expansion match with metallic structures and good mechanical and chemical properties. Nanoscale reinforced composite coatings in which the matrix is derived from preceramic polymers have the potential to meet these requirements. The research was focused on developing suitable material systems and

  11. Modified glass fibre reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Cao, Yumei

    A high ratio of strength to density and relatively low-cost are some of the significant features of glass fibre reinforced polymer composites (GFRPCs) that made them one of the most rapidly developed materials in recent years. They are widely used as the material of construction in the areas of aerospace, marine and everyday life, such as airplane, helicopter, boat, canoe, fishing rod, racket, etc. Traditionally, researchers tried to raise the mechanical properties and keep a high strength/weight ratio using all or some of the following methods: increasing the volume fraction of the fibre; using different polymeric matrix material; or changing the curing conditions. In recent years, some new techniques and processing methods were developed to further improve the mechanical properties of glass fibre (GF) reinforced polymer composite. For example, by modifying the surface condition of the GF, both the interface strength between the GF and the polymer matrix and the shear strength of the final composite can be significantly increased. Also, by prestressing the fibre during the curing process of the composite, the tensile, flexural and the impact properties of the composite can be greatly improved. In this research project, a new method of preparing GFRPCs, which combined several traditional and modern techniques together, was developed. This new method includes modification of the surface of the GF with silica particles, application of different levels of prestressing on the GF during the curing process, and the change of the fibre volume fraction and curing conditions in different sets of experiments. The results of the new processing were tested by the three-point bend test, the short beam shear test and the impact test to determine the new set of properties so formed in the composite material. Scanning electronic microscopy (SEM) was used to study the fracture surface of the new materials after the mechanical tests were performed. By taking advantages of the

  12. Molecular and nanoscale reinforcement of polymers

    NASA Astrophysics Data System (ADS)

    Zerda, Adam S.

    The reinforcement of polymers using additives of dimensions below one micrometer is presented: those acting at the molecular and nanometer scales. This thesis will describe new additives and morphologies exhibiting high levels of mechanical reinforcement. It is the focus of this work to chronicle the range of physical and material properties that are altered upon inclusion of these modifiers. Additionally, this thesis will establish how these physical-property changes affect the mechanical behavior of the resulting composite. In the area of molecular reinforcement, a new class of additive, the organophosphate, is shown here to enhance modulus and yield strength in epoxy polymers once cured. Initially, the effect on the physical and thermal properties of the polymer system is investigated as a function of additive molecular weight, solubility, and concentration. The altered properties include T g, density, thermal stability and initial epoxy viscosity. The mechanical properties of the modified epoxy are demonstrated to be a result of the physical changes made to the matrix polymer through the addition of the organophosphorous additive. By increasing the density of the polymer and reducing or eliminating sub-Tg relaxations, the modulus and yield strength of the polymer can be greatly enhanced. These property changes are investigated in a variety of epoxy polymer systems in order to elucidate the effects of both the additive and polymer chemical structure on final mechanical properties. Polymer modification using nanometer-scale additives and modifiers has been the focus of intense study recently. Heretofore, these studies have focused on the exfoliated, or delaminated, clay morphology to impart the property enhancements, effectively isolating the particulates within the matrix. This thesis focuses on polymer modification at the nanometer scale such that the added clays interact and positively change the composite fracture toughness. By introducing this clay

  13. Microscopic mechanism of reinforcement and conductivity in polymer nanocomposite materials

    NASA Astrophysics Data System (ADS)

    Chang, Tae-Eun

    Modification of polymers by adding various nano-particles is an important method to obtain effective enhancement of materials properties. Within this class of materials, carbon nanotubes (CNT) are among the most studied materials for polymer reinforcement due to their extraordinary mechanical properties, superior thermal and electronic properties, and high aspect ratio. However, to unlock the potential of CNTs for applications, CNTs must be well dispersed in a polymer matrix and the microscopic mechanism of polymer reinforcement by CNTs must be understood. In this study, single-wall carbon nanotube (SWNT) composites with polypropylene (PP)-SWNT and polystyrene (PS)-SWNT were prepared and analyzed. Microscopic study of the mechanism of reinforcement and conductivity by SWNT included Raman spectroscopy, wide-angle X-ray diffraction (WAXD) and dielectric measurement. For PP-SWNT composites, tensile tests show a three times increase in the Young's modulus with addition of only 1 wt% SWNT, and much diminished increase of modulus with further increase in SWNT concentration. For PS-SWNT composites, well-dispersed SWNT/PS composite has been produced, using initial annealing of SWNT and optimum sonication conditions. The studies on the tangential mode in the Raman spectra and TEM indicated well-dispersed SWNTs in a PS matrix. We show that conductivity appears in composites already at very low concentrations, hinting at the formation of a 'percolative' network even below 0.5% of SWNT. The Raman studies for both composites show good transfer of the applied stress from the polymer matrices to SWNTs. However, no significant improvement of mechanical property is observed for PS-SWNT composites. The reason for only a slight increase of mechanical property remains unknown.

  14. Investigation of nanoscale reinforcement into textile polymers

    NASA Astrophysics Data System (ADS)

    Khan, Mujibur Rahman

    A dual inclusion strategy for textile polymers has been investigated to increase elastic energy storage capacity of fibers used in high velocity impact applications. Commercial fibers such as Spectra and Dyneema are made from ultra high molecular weight polyethylene (UHMWPE). Dynamic elastic energy of these fibers is still low therefore limiting their wholesale application without a secondary metallic or ceramic component. The idea in this investigation is to develop methodologies so that the elastic energy of polyethylene based fibers can be increased by several folds. This would allow manufacturing of an all-fabric system for high impact applications. The dual inclusion consists of a polymer phase and a nanoscale inorganic phase to polyethylene. The polymer phase was nylon-6 and the inorganic phase was carbon nanotubes (CNTs). Nylon-6 was blended as a minor phase into UHMWPE and was chosen because of its large fracture strain -- almost one order higher than that of UHMWPE. On the other hand, CNTs with their very high strength, modulus, and aspect ratio, contributed to sharing of load and sliding of polymer interfaces as they aligned during extrusion and strain hardening processes. A solution spinning process was developed to produce UHMWPE filaments reinforced with CNTs and nylon-6. The procedure involved dispersing of CNTs into paraffin oil through sonication followed by dissolving polymers into paraffin-CNT solution using a homogenizer. The admixture was fed into a single screw extruder for melt mixing and extrusion through an orifice. The extrudate was rinsed via a hexane bath, stabilized through a heater, and then drawn into a filament winder with controlled stretching. In the next step, the as produced filaments were strain-hardened through repeated loading unloading cycles under tension. Neat and reinforced filaments were characterized through DSC (Differential Scanning Calorimetry), XRD (X-ray Diffraction), Raman Spectroscopy, SEM (Scanning Electron

  15. Synthesis of Reinforced Polyacrylate and Polyepoxide Polymers

    NASA Astrophysics Data System (ADS)

    Salmi, Aicha; Meziani, Amina; Zahouily, Khalid; Benfarhi, Said

    Nanocomposite polymers have drawn increased attention over the two last decades because of their distinct characteristics in particular superior mechanical and barrier properties. In this paper we present our results on the synthesis and the biodegradability of nanocomposite materials, made of silicate platelets (montmorillonite and beidellite) dispersed in a crosslinked polyurethane -acrylate and polyepoxide matrix. The compatibility polymer-clay has been optimized by surface modification of clay. The treatment of clay was confirmed by FTIR spectroscopy and X-ray diffraction. The nanocomposite materials were synthetized by photoinduced polymerization (UV lamp and solar UV). The study of curing kinetics obtained show that the addition of organophilic clay has little effect on the conversion of acrylates while in the epoxyde, the effect is more pronounced because a some of the protons generated by the photo-initiator is neutralized by the negative charges dispersed onto clay surface. The polymer nanocomposites obtained are transparent, slightly or insoluble in organic solvents. Moreover we have demonstrated that the polyurethane -acrylate is biodegradable and the intimate association of the reinforcement and the organic matrix at the molecular level decrease this biodegradability.

  16. Strengthening of dental adhesives via particle reinforcement.

    PubMed

    Belli, Renan; Kreppel, Stefan; Petschelt, Anselm; Hornberger, Helga; Boccaccini, Aldo R; Lohbauer, Ulrich

    2014-09-01

    The bond between methacrylic polymer adhesives and dental restoratives is not perfect and may fail either in the short or in the long term. This study aims to evaluate the effects of particle incorporation in a self-etch model adhesive on mechanical and physical properties that are relevant during application and service. Filled adhesives containing 5, 10, 15 or 25wt% glass fillers were compared to their unfilled counterpart in terms of water sorption and solubility; viscosity and dynamic viscosity during polymerization were recorded using rheological measurements and compared to FTIR analysis of the real-time degree of cure. Elastic modulus and ultimate tensile strength measurements were performed in uniaxial tension; the energy to fracture was used to calculate the fracture toughness of the adhesives. Finally, the experimental adhesives were applied on dentin substrate to test the bond strength using the microtensile test. Results showed that the incorporation of 5-10wt% nanofiller to self-etching dental adhesives is efficient in accelerating the polymerization reaction and increasing the degree of cure without compromising the film viscosity for good wettability or water sorption and solubility. Fillers increased the elastic modulus, tensile strength and fracture toughness to a plateau between 5 and 15wt% filler concentration, and despite the tendency to form agglomerations, active crack pinning/deflection toughening mechanisms have been observed. The bond strength between resin composite and dentin was also improved when adhesives with up to 10wt% fillers were used, with no additional improvements with further packing. The use of fillers to reinforce dental adhesives may therefore be of great practical benefit by improving curing and mechanical properties.

  17. Interphase and particle dispersion correlations in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan

    Particle dispersion in polymer matrices is a major parameter governing the mechanical performance of polymer nanocomposites. Controlling particle dispersion and understanding aging of composites under large shear and temperature variations determine the processing conditions and lifetime of composites which are very important for diverse applications in biomedicine, highly reinforced materials and more importantly for the polymer composites with adaptive mechanical responses. This thesis investigates the role of interphase layers between particles and polymer matrices in two bulk systems where particle dispersion is altered upon deformation in repulsive composites, and good-dispersion of particles is retained after multiple oscillatory shearing and aging cycles in attractive composites. We demonstrate that chain desorption and re-adsorption processes in attractive composites under shear can effectively enhance the bulk microscopic mechanical properties, and long chains of adsorbed layers lead to a denser entangled interphase layer. We further designed experiments where particles are physically adsorbed with bimodal lengths of homopolymer chains to underpin the entanglement effect in interphases. Bimodal adsorbed chains are shown to improve the interfacial strength and used to modulate the elastic properties of composites without changing the particle loading, dispersion state or polymer conformation. Finally, the role of dynamic asymmetry (different mobilities in polymer blends) and chemical heterogeneity in the interphase layer are explored in systems of poly(methyl methacrylate) adsorbed silica nanoparticles dispersed in poly(ethylene oxide) matrix. Such nanocomposites are shown to exhibit unique thermal-stiffening behavior at temperatures above glass transitions of both polymers. These interesting findings suggest that the mobility of the surface-bound polymer is essential for reinforcement in polymer nanocomposites, contrary to existing glassy layer theories

  18. Synthesis And Characterization Of Reduced Size Ferrite Reinforced Polymer Composites

    SciTech Connect

    Borah, Subasit; Bhattacharyya, Nidhi S.

    2008-04-24

    Small sized Co{sub 1-x}Ni{sub x}Fe{sub 2}O{sub 4} ferrite particles are synthesized by chemical route. The precursor materials are annealed at 400, 600 and 800 C. The crystallographic structure and phases of the samples are characterized by X-ray diffraction (XRD). The annealed ferrite samples crystallized into cubic spinel structure. Transmission Electron Microscopy (TEM) micrographs show that the average particle size of the samples are <20 nm. Particulate magneto-polymer composite materials are fabricated by reinforcing low density polyethylene (LDPE) matrix with the ferrite samples. The B-H loop study conducted at 10 kHz on the toroid shaped composite samples shows reduction in magnetic losses with decrease in size of the filler sample. Magnetic losses are detrimental for applications of ferrite at high powers. The reduction in magnetic loss shows a possible application of Co-Ni ferrites at high microwave power levels.

  19. Investigating Filler Reinforcement and Nonlinear Viscoelastic Behavior in Polymer Composites

    NASA Astrophysics Data System (ADS)

    Zhu, Zhiyong; Wang, Shi-Qing; von Meerwall, Ernst

    2004-03-01

    Solid fillers have been known to enhance the linear viscoelastic responses of polymer melts and elastomers. Nonlinear viscoelastic behavior of such systems is closely related to the reinforcement of the linear viscoelascity. Understanding such phenomena as the Payne effect (where the storage modulus is measured to decrease in oscillatory shear with the amplitude of the oscillation and with time for a fixed amplitude) requires a better understanding of the filler reinforcement mechanism. Recent publications, from two different groups (a) (b) prompted our present study. Using monodisperse 1,4-polybutadiene melts as the matrix and nano-silicon oxide particles of 15 nm diameter as the fillers, we carried out a variety of viscoelastic and NMR-spin-echo diffusion measurements to elucidate the important role of the filler-filler networking in controlling the observed linear and nonlinear behavior at temperatures over 100 degrees above the glass transition temperature of PBD. (a)S.S. Sternstein and A. Zhu, Macromolecules 35, 7262 (2002); Composites Sci. and Techn. 63, 1113 (2003). This work claims that the reinforcement arises primarily from the entrapped chain entanglement due to chain adsorption on filler surfaces instead of the filler-filler networking. (b) H. Montes, F. Lequeux and J. Berriot, Macromolecules, 36, 8107 (2003). This work advocates that a glassy layer formed around each filler is responsible for the enhanced linear viscoelascity and for the observed nonlinear viscoelastic behavior such as the Payne effect.

  20. Reinforced polypropylene composites: effects of chemical compositions and particle size.

    PubMed

    Ashori, Alireza; Nourbakhsh, Amir

    2010-04-01

    In this work, the effects of wood species, particle sizes and hot-water treatment on some physical and mechanical properties of wood-plastic composites were studied. Composites of thermoplastic reinforced with oak (Quercus castaneifolia) and pine (Pinus eldarica) wood were prepared. Polypropylene (PP) and maleic anhydride grafted polypropylene (MAPP) were used as the polymer matrix and coupling agent, respectively. The results showed that pine fiber had significant effect on the mechanical properties considered in this study. This effect is explained by the higher fiber length and aspect ratio of pine compared to the oak fiber. The hot-water treated (extractive-free) samples, in both wood species, improved the tensile, flexural and impact properties, but increased the water absorption for 24h. This work clearly showed that lignocellulosic materials in both forms of fiber and flour could be effectively used as reinforcing elements in PP matrix. Furthermore, extractives have marked effects on the mechanical and physical properties.

  1. Effective reinforcement in carbon nanotube-polymer composites.

    PubMed

    Wang, W; Ciselli, P; Kuznetsov, E; Peijs, T; Barber, A H

    2008-05-13

    Carbon nanotubes have mechanical properties that are far in excess of conventional fibrous materials used in engineering polymer composites. Effective reinforcement of polymers using carbon nanotubes is difficult due to poor dispersion and alignment of the nanotubes along the same axis as the applied force during composite loading. This paper reviews the mechanical properties of carbon nanotubes and their polymer composites to highlight how many previously prepared composites do not effectively use the excellent mechanical behaviour of the reinforcement. Nanomechanical tests using atomic force microscopy are carried out on simple uniaxially aligned carbon nanotube-reinforced polyvinyl alcohol (PVA) fibres prepared using electrospinning processes. Dispersion of the carbon nanotubes within the polymer is achieved using a surfactant. Young's modulus of these simple composites is shown to approach theoretically predicted values, indicating that the carbon nanotubes are effective reinforcements. However, the use of dispersant is also shown to lower Young's modulus of the electrospun PVA fibres.

  2. Structural Behavior of Concrete Beams Reinforced with Basalt Fiber Reinforced Polymer (BFRP) Bars

    NASA Astrophysics Data System (ADS)

    Ovitigala, Thilan

    The main challenge for civil engineers is to provide sustainable, environmentally friendly and financially feasible structures to the society. Finding new materials such as fiber reinforced polymer (FRP) material that can fulfill the above requirements is a must. FRP material was expensive and it was limited to niche markets such as space shuttles and air industry in the 1960s. Over the time, it became cheaper and spread to other industries such as sporting goods in the 1980-1990, and then towards the infrastructure industry. Design and construction guidelines are available for carbon fiber reinforced polymer (CFRP), aramid fiber reinforced polymer (AFRP) and glass fiber reinforced polymer (GFRP) and they are currently used in structural applications. Since FRP is linear elastic brittle material, design guidelines for the steel reinforcement are not valid for FRP materials. Corrosion of steel reinforcement affects the durability of the concrete structures. FRP reinforcement is identified as an alternative to steel reinforcement in corrosive environments. Although basalt fiber reinforced polymer (BFRP) has many advantages over other FRP materials, but limited studies have been done. These studies didn't include larger BFRP bar diameters that are mostly used in practice. Therefore, larger beam sizes with larger BFRP reinforcement bar diameters are needed to investigate the flexural and shear behavior of BFRP reinforced concrete beams. Also, shear behavior of BFRP reinforced concrete beams was not yet studied. Experimental testing of mechanical properties and bond strength of BFRP bars and flexural and shear behavior of BFRP reinforced concrete beams are needed to include BFRP reinforcement bars in the design codes. This study mainly focuses on the use of BFRP bars as internal reinforcement. The test results of the mechanical properties of BFRP reinforcement bars, the bond strength of BFRP reinforcement bars, and the flexural and shear behavior of concrete beams

  3. Peptide Nanotube Reinforced Polymers: A System for Tunable, Composite Materials

    DTIC Science & Technology

    2015-11-30

    their potential application in reinforcing polymeric materials. The proposal was framed in the context of stabilizing load-bearing resorbable biomedical...be many applications where customizing polymer -filler interactions would be of utmost importance. 3) Summary of most important results The...mechanical reinforcement of polymeric materials used in the fabrication of implantable medical devices. Our results show that the high aspect ratio

  4. Reinforcement effect of soy protein and carbohydrates in polymer composites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The modulus of soft polymer material can be increased by filler reinforcement. A review of using soy protein and carbohydrates as alternative renewable reinforcement material is presented here. Dry soy protein and carbohydrates are rigid and can form strong filler networks through hydrogen-bonding...

  5. In situ reinforced polymers using low molecular weight compounds

    NASA Astrophysics Data System (ADS)

    Yordem, Onur Sinan

    2011-12-01

    The primary objective of this research is to generate reinforcing domains in situ during the processing of polymers by using phase separation techniques. Low molecular weight compounds were mixed with polymers where the process viscosity is reduced at process temperatures and mechanical properties are improved once the material system is cooled or reacted. Thermally induced phase separation and thermotropic phase transformation of low molar mass compounds were used in isotactic polypropylene (iPP) and poly(ether ether ketone) (PEEK) resins. Reaction induced phase separation was utilized in thermosets to generate anisotropic reinforcements. A new strategy to increase fracture toughness of materials was introduced. Simultaneously, enhancement in stiffness and reduction in process viscosity were also attained. Materials with improved rheological and mechanical properties were prepared by using thermotropic phase transformations of metal soaps in polymers (calcium stearate/iPP). Morphology and thermal properties were studied using WAXS, DSC and SEM. Mechanical and rheological investigation showed significant reduction in process viscosity and substantial improvement in fracture toughness were attained. Effects of molecular architecture of metal soaps were investigated in PEEK (calcium stearate/PEEK and sodium stearate/PEEK). The selected compounds reduced the process viscosity due to the high temperature co-continuous morphology of metal soaps. Unlike the iPP system that incorporates spherical particles, interaction between PEEK and metal soaps resulted in two discrete and co-continuous phases of PEEK and the metal stearates. DMA and melt rheology exhibited that sodium stearate/PEEK composites are stiffer. Effective moduli of secondary metal stearate phase were calculated using different composite theories, which suggested bicontinuous morphology to the metal soaps in PEEK. Use of low molecular weight crystallizable solvents was investigated in reactive systems

  6. Solid particle erosion of polymers and composites

    NASA Astrophysics Data System (ADS)

    Friedrich, K.; Almajid, A. A.

    2014-05-01

    After a general introduction to the subject of solid particle erosion of polymers and composites, the presentation focusses more specifically on the behavior of unidirectional carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites under such loadings, using different impact conditions and erodents. The data were analyzed on the basis of a newly defined specific erosive wear rate, allowing a better comparison of erosion data achieved under various testing conditions. Characteristic wear mechanisms of the CF/PEEK composites consisted of fiber fracture, matrix cutting and plastic matrix deformation, the relative contribution of which depended on the impingement angles and the CF orientation. The highest wear rates were measured for impingement angles between 45 and 60°. Using abrasion resistant neat polymer films (in this case PEEK or thermoplastic polyurethane (TPU) ones) on the surface of a harder substrate (e.g. a CF/PEEK composite plate) resulted in much lower specific erosive wear rates. The use of such polymeric films can be considered as a possible method to protect composite surfaces from damage caused by minor impacts and erosion. In fact, they are nowadays already successfully applied as protections for wind energy rotor blades.

  7. Mechanical reinforcement and segmental dynamics of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Gong, Shushan

    The addition of nanofiller into a polymer matrix will dramatically change the physical properties of polymer. The introduction of nanofiller makes the polymer more applicable in many industries, such as automobile tires, coatings, semiconductors, and packaging. The altered properties are not the simple combination of the characters from the two components. The interactions in polymer nanocomposites play an important role in determining the physical properties. This dissertation focuses on the mechanical properties of polymer nanocomposites (silica/poly-2-vinylpyridine) above their glass transition temperature Tg, as a model for automobile tires, which utilize small silica particles in crosslinked rubber far above Tg. We also investigate the impacts of the interaction between particle filler and polymer matrix on the altered mechanical properties. Dielectric relaxation spectroscopy (DRS) is used to study the glassy bound polymer layers formed around the particles. The results show evidence of the existence of immobilized polymer layers at the surface of each nanoparticle. At the same time, the thickness of the immobilized polymer layers is quantified and formed to be around 2 nm. Then we consider particles with glassy bound polymer layers are bridged together (either rubbery bridge or glassy bridge) by polymer chains and form small clusters. Clusters finally percolate to form a particle-polymer network as loading fraction increases. Rheology is used to study the network formation, and to predict the boundary of rubbery bridge and glassy bridge regimes. The distance between particles determines the type of polymer bridging. The particle spacing larger than Kuhn length makes flexible (rubbery) bridge with rheology described by a flexible Rouse model for percolation. When the spacing is shorter than the Kuhn length (~ 1nm), stiffer bridge forms instead, which is called glassy bridge. The mechanical differences between rubbery bridge and glassy bridge, and the effect of

  8. Polymer concrete reinforced with recycled-tire fibers: Mechanical properties

    NASA Astrophysics Data System (ADS)

    Martínez-Cruz, E.; Martínez-Barrera, G.; Martínez-López, M.

    2013-06-01

    Polymer Concrete was reinforced with recycled-tire fibers in order to improve the compressive and flexural strength. Polymer concrete specimens were prepared with 70% of silicious sand, 30% of polyester resin and various fiber concentrations (0.3, 0.6, 0.9 and 1.2 vol%). The results show increment of 50% in average of the compressive and flexural strength as well as on the deformation when adding 1.2 vol% of recycled-fibers.

  9. Entanglement network in nanoparticle reinforced polymers.

    PubMed

    Riggleman, Robert A; Toepperwein, Gregory; Papakonstantopoulos, George J; Barrat, Jean-Louis; de Pablo, Juan J

    2009-06-28

    Polymer nanocomposites have been widely studied in efforts to engineer materials with mechanical properties superior to those of the pure polymer, but the molecular origins of the sought-after improved properties have remained elusive. An ideal polymer nanocomposite model has been conceived in which the nanoparticles are dispersed throughout the polymeric matrix. A detailed examination of topological constraints (or entanglements) in a nanocomposite glass provides new insights into the molecular origin of the improved properties in polymer nanocomposites by revealing that the nanoparticles impart significant enhancements to the entanglement network. Nanoparticles are found to serve as entanglement attractors, particularly at large deformations, altering the topological constraint network that arises in the composite material.

  10. Comparison of mechanical and tribotechnical properties of UHMWPE reinforced with basalt fibers and particles

    NASA Astrophysics Data System (ADS)

    Panin, S. V.; Kornienko, L. A.; Alexenko, V. O.; Qitao, Huang; Ivanova, L. R.

    2016-11-01

    Mechanical and tribotechnical properties of UHMWPE composites reinforced with basalt fibers and particles under dry sliding friction and abrasion were investigated. It is shown that adding of the basalt particles provides higher wear resistance under the dry sliding friction while at abrasion filling by the basalt fibers is more efficient since the wear resistance of the reinforced UHMWPE composites is by 3.7 times higher in contrast with the neat polymer. Wear mechanisms of the polymeric UHMWPE composites under various types of wear are discussed.

  11. CO2-Laser Cutting Fiber Reinforced Polymers

    NASA Astrophysics Data System (ADS)

    Mueller, R.; Nuss, Rudolf; Geiger, Manfred

    1989-10-01

    Guided by experimental investigations laser cutting of glass fiber reinforced reactive injection moulded (RRIM)-polyurethanes which are used e.g. in car industry for bumpers, spoilers, and further components is described. A Comparison with other cutting techniques as there are water jet cutting, milling, punching, sawing, cutting with conventional knife and with ultrasonic excited knife is given. Parameters which mainly influence cutting results e.g. laser power, cutting speed, gas nature and pressure will be discussed. The problematic nature in characterising micro and macro geometry of laser cut edges of fiber reinforced plastic (FRP) is explained. The topography of cut edges is described and several characteristic values are introduced to specify the obtained working quality. The surface roughness of laser cut edges is measured by both, an optical and a mechanical sensor and their reliabilities are compared.

  12. Polymer blends with biodegradable components and reinforcements

    NASA Astrophysics Data System (ADS)

    Sartore, Luciana; Di Landro, Luca

    2014-05-01

    Polymeric blends based on ethylene vinyl acetate rubbers filled with high mol. wt. carboxymethyl cellulose were investigated in view of possible employment as biodegradable materials. The effect of vinyl acetate content and of addition of transesterification agent to increase interaction between EVA and cellulosic components was considered. Blends reinforced with cellulose microfibers in different amounts were also characterized in their mechanical, rheological and thermal behavior.

  13. Flexural retrofitting of reinforced concrete structures using Green Natural Fiber Reinforced Polymer plates

    NASA Astrophysics Data System (ADS)

    Cervantes, Ignacio

    An experimental study will be carried out to determine the suitability of Green Natural Fiber Reinforced Polymer plates (GNFRP) manufactured with hemp fibers, with the purpose of using them as structural materials for the flexural strengthening of reinforced concrete (RC) beams. Four identical RC beams, 96 inches long, are tested for the investigation, three control beams and one test beam. The first three beams are used as references; one unreinforced, one with one layer of Carbon Fiber Reinforced Polymer (CFRP), one with two layers of CFRP, and one with n layers of the proposed, environmental-friendly, GNFRP plates. The goal is to determine the number of GNFRP layers needed to match the strength reached with one layer of CFRP and once matched, assess if the system is less expensive than CFRP strengthening, if this is the case, this strengthening system could be an alternative to the currently used, expensive CFRP systems.

  14. Multi-functional particle assemblies in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Jiao, Yang

    Self-assembly into ordered and equilibrium configurations underlie the microphase separation of block copolymers, protein folding and anisotropic aggregation of functionalized nanoparticles. In this project, we explored the assembly of polymer-grafted magnetic nanoparticles in solution and bulk states to combine various properties, such as ionic conductivity, mechanical reinforcement and responsiveness to external flows, within the same sample. The multi-functionality of iron oxide nanoparticles in polymer media is achieved using bottom-up approaches. Starting from the particle core synthesis, many layers of functionalities are added on magnetite (Fe3O4) nanoparticles by i) grafting polystyrene chains at different densities, lengths and elasticity; by ii) functionalizing particles with ionomers; and by iii) attaching charged diblock copolymers onto particles. In these three complex systems, particle nanostructures are investigated to explain the role of interactions between particle-particle, polymer-particle and polymer-polymer. We found that polystyrene-grafted Fe3O4 nanoparticles can form strings, spherical clusters and dispersed structures in polymer matrices by tuning the polymer graft density and grafted chain length. This structural transition has been explained through chain interactions and short-range dipolar interactions. We showed that chain conformation (radius of gyration) interestingly is not influenced within different dispersion states. Small-angle x-ray and neutron scattering results reveal that matrix chains do not govern the formation of strings, but have a significant impact on the size and internal structure of aggregated particles. Our findings showed that spherical aggregates of nanoparticles with low polymer graft densities are similar to interpenetrating networks in which free matrix chains bridge the fractals of particles and control the cluster density. Further, the mechanical properties of these different composite structures under

  15. Polymer-Particle Nanocomposites: Size and Dispersion Effects

    NASA Astrophysics Data System (ADS)

    Moll, Joseph

    Polymer-particle nanocomposites are used in industrial processes to enhance a broad range of material properties (e.g. mechanical, optical, electrical and gas permeability properties). This dissertation will focus on explanation and quantification of mechanical property improvements upon the addition of nanoparticles to polymeric materials. Nanoparticles, as enhancers of mechanical properties, are ubiquitous in synthetic and natural materials (e.g. automobile tires, packaging, bone), however, to date, there is no thorough understanding of the mechanism of their action. In this dissertation, silica (SiO2) nanoparticles, both bare and grafted with polystyrene (PS), are studied in polymeric matrices. Several variables of interest are considered, including particle dispersion state, particle size, length and density of grafted polymer chains, and volume fraction of SiO2. Polymer grafted nanoparticles behave akin to block copolymers, and this is critically leveraged to systematically vary nanoparticle dispersion and examine its role on the mechanical reinforcement in polymer based nanocomposites in the melt state. Rheology unequivocally shows that reinforcement is maximized by the formation of a transient, but long-lived, percolating polymer-particle network with the particles serving as the network junctions. The effects of dispersion and weight fraction of filler on nanocomposite mechanical properties are also studied in a bare particle system. Due to the interest in directional properties for many different materials, different means of inducing directional ordering of particle structures are also studied. Using a combination of electron microscopy and x-ray scattering, it is shown that shearing anisotropic NP assemblies (sheets or strings) causes them to orient, one in front of the other, into macroscopic two-dimensional structures along the flow direction. In contrast, no such flow-induced ordering occurs for well dispersed NPs or spherical NP aggregates! This work

  16. Polymer surface treatment with particle beams

    DOEpatents

    Stinnett, Regan W.; VanDevender, J. Pace

    1999-01-01

    A polymer surface and near surface treatment process produced by irradiation with high energy particle beams. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications.

  17. Polymer surface treatment with particle beams

    DOEpatents

    Stinnett, R.W.; VanDevender, J.P.

    1999-05-04

    A polymer surface and near surface treatment process produced by irradiation with high energy particle beams is disclosed. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications. 16 figs.

  18. Constitutive Modeling of Nanotube-Reinforced Polymer Composite Systems

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Harik, Vasyl M.; Wise, Kristopher E.; Gates, Thomas S.

    2004-01-01

    In this study, a technique has been proposed for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Since the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties of the SWNT/polymer composites can no longer be determined through traditional micromechanical approaches that are formulated using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber retains the local molecular structure and bonding information and serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube sizes and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyethylene composite systems, one with continuous and aligned SWNT and the other with discontinuous and randomly aligned nanotubes.

  19. Constitutive Modeling of Nanotube-Reinforced Polymer Composite Systems

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Harik, Vasyl M.; Wise, Kristopher E.; Gates, Thomas S.

    2001-01-01

    In this study, a technique has been proposed for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Since the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties of the SWNT/polymer composites can no longer be determined through traditional micromechanical approaches that are formulated using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber retains the local molecular structure and bonding information and serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube sizes and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyethylene composite systems, one with continuous and aligned SWNT and the other with discontinuous and randomly aligned nanotubes.

  20. CO2 Laser Cutting of Glass Fiber Reinforce Polymer Composite

    NASA Astrophysics Data System (ADS)

    Fatimah, S.; Ishak, M.; Aqida, S. N.

    2012-09-01

    The lamination, matrix properties, fiber orientation, and relative volume fraction of matrix of polymer structure make this polymer hard to process. The cutting of polymer composite using CO2 laser could involve in producing penetration energy in the process. Identification of the dominant factors that significantly affect the cut quality is important. The objective of this experiment is to evaluate the CO2 spot size of beam cutting for Glass Fiber Reinforce Polymer Composite (GFRP). The focal length selected 9.5mm which gave smallest focus spot size according to the cutting requirements. The effect of the focal length on the cut quality was investigated by monitoring the surface profile and focus spot size. The beam parameter has great effect on both the focused spot size and surface quality.

  1. Rolling contact fatigue of various unfilled and fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Almajid, Abdulhakim; Friedrich, Klaus

    2012-07-01

    The wear behavior of Polyamide 6 (PA6), Polyoxymethylene (POM), Polyetheretherketone (PEEK), and Polyparaphenylene (PPP) materials under rolling contact was investigated. The ball on plate principle, i.e. a steel ball (as counterpart) rolls on a polymer plate specimen in rotational or linear motion, was used. The results are shown for different stress parameters which vary by load (50 N up to 300 N) and testing time (up to 50 hours). Differences in surface fatigue mechanisms were illustrated by microscopic methods. The best performance was found for PEEK. All the neat polymers were superior to any reinforced versions of them.

  2. Infinite Coordination Polymer Nano- and Micro-Particles

    DTIC Science & Technology

    2015-06-12

    SECURITY CLASSIFICATION OF: Infinite coordination polymer (ICP) particles and metal- organic frameworks (MOFs) are attractive materials for a diverse...Coordination Polymer Nano- and Micro- Particles Report Title Infinite coordination polymer (ICP) particles and metal- organic frameworks (MOFs) are...Abstract Infinite coordination polymer (ICP) particles and metal- organic frameworks (MOFs) are attractive materials for a diverse array of

  3. Rate dependent constitutive models for fiber reinforced polymer composites

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.

    1990-01-01

    A literature survey was conducted to assess the state-of-the-art in rate dependent constitutive models for continuous fiber reinforced polymer matrix composite (PMC) materials. Several recent models which include formulations for describing plasticity, viscoelasticity, viscoplasticity, and rate-dependent phenomenon such as creep and stress relaxation are outlined and compared. When appropriate, these comparisons include brief descriptions of the mathematical formulations, the test procedures required for generating material constants, and details of available data comparing test results to analytical predictions.

  4. Functionalization of Natural Graphite for Use as Reinforcement in Polymer Nanocomposites.

    PubMed

    Araujo, Rafael; Marques, Maria F V; Jonas, Renato; Grafova, Iryna; Grafov, Andriy

    2015-08-01

    Graphite is a naturally abundant material that has been used as reinforcing filler to produce polymeric nanocomposites for various applications including automotive, aerospace and electric-electronic. The objective of this study was to develop methodologies of graphite nanosheets preparation and for incorporation into polymer matrices. By means of different chemical and physical treatments, natural graphite was modified and subsequently characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetry (TGA) and the particle size determination. The results obtained clearly show that after the treatments employed, polar chemical groups were inserted on the natural graphite surface. Nanosized graphite particles of high aspect ratio were obtained.

  5. Constitutive Modeling of Nanotube-Reinforced Polymer Composites

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Gates, T. S.; Wise, K. E.; Park, C.; Siochi, E. J.; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties can no longer be determined through traditional micromechanical approaches that are formulated by using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube lengths, concentrations, and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyimide composite systems.

  6. Constitutive Modeling of Nanotube-Reinforced Polymer Composites

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Gates, T. S.; Wise, K. E.

    2002-01-01

    In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties can no longer be determined through traditional micromechanical approaches that are formulated by using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube shapes, sizes, concentrations, and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/LaRC-SI (with a PmPV interface) composite systems, one with aligned SWNTs and the other with three-dimensionally randomly oriented SWNTs. The Young's modulus and shear modulus have been calculated for the two systems for various nanotube lengths and volume fractions.

  7. Filler-polymer bonding and its role in elastomer reinforcement

    SciTech Connect

    Xu, Ping, Mark, J.E.

    1993-12-31

    Iron oxide particles were blended into samples of cis-1,4-polybutadiene and polyisobutylene, and both the unfilled polymers and the resulting polymer-filler mixture were cured with benzoyl peroxide. The filled networks were cloudy, but strips extracted using a toluene-hydrochloric acid mixture became as clear as the unfilled networks, suggesting removal of the filler particles. Equilibrium swelling and stress-strain measurements in elongation were carried out the unfilled elastomer and on the filled ones, both before and after extraction. There were no significant differences between the stress-strain isotherms and degrees of equilibrium swelling of the unfilled networks and the corresponding properties of the previously-filled networks after the filler particles were removed. This suggests that for these systems, the bonding between the filler particles and the polymer chains is physical rather than chemical.

  8. Investigation of rectangular concrete columns reinforced or prestressed with fiber reinforced polymer (FRP) bars or tendons

    NASA Astrophysics Data System (ADS)

    Choo, Ching Chiaw

    Fiber reinforced polymer (FRP) composites have been increasingly used in concrete construction. This research focused on the behavior of concrete columns reinforced with FRP bars, or prestressed with FRP tendons. The methodology was based the ultimate strength approach where stress and strain compatibility conditions and material constitutive laws were applied. Axial strength-moment (P-M) interaction relations of reinforced or prestressed concrete columns with FRP, a linearly-elastic material, were examined. The analytical results identified the possibility of premature compression and/or brittle-tension failure occurring in FRP reinforced and prestressed concrete columns where sudden and explosive type failures were expected. These failures were related to the rupture of FRP rebars or tendons in compression and/or in tension prior to concrete reaching its ultimate strain and strength. The study also concluded that brittle-tension failure was more likely to occur due to the low ultimate tensile strain of FRP bars or tendons as compared to steel. In addition, the failures were more prevalent when long term effects such as creep and shrinkage of concrete, and creep rupture of FRP were considered. Barring FRP failure, concrete columns reinforced with FRP, in some instances, gained significant moment resistance. As expected the strength interaction of slender steel or FRP reinforced concrete columns were dependent more on column length rather than material differences between steel and FRP. Current ACI minimum reinforcement ratio for steel (rhomin) reinforced concrete columns may not be adequate for use in FRP reinforced concrete columns. Design aids were developed in this study to determine the minimum reinforcement ratio (rhof,min) required for rectangular reinforced concrete columns by averting brittle-tension failure to a failure controlled by concrete crushing which in nature was a less catastrophic and more gradual type failure. The proposed method using rhof

  9. Flexural strengthening of Reinforced Concrete (RC) Beams Retrofitted with Corrugated Glass Fiber Reinforced Polymer (GFRP) Laminates

    NASA Astrophysics Data System (ADS)

    Aravind, N.; Samanta, Amiya K.; Roy, Dilip Kr. Singha; Thanikal, Joseph V.

    2015-01-01

    Strengthening the structural members of old buildings using advanced materials is a contemporary research in the field of repairs and rehabilitation. Many researchers used plain Glass Fiber Reinforced Polymer (GFRP) sheets for strengthening Reinforced Concrete (RC) beams. In this research work, rectangular corrugated GFRP laminates were used for strengthening RC beams to achieve higher flexural strength and load carrying capacity. Type and dimensions of corrugated profile were selected based on preliminary study using ANSYS software. A total of twenty one beams were tested to study the load carrying capacity of control specimens and beams strengthened with plain sheets and corrugated laminates using epoxy resin. This paper presents the experimental and theoretical study on flexural strengthening of Reinforced Concrete (RC) beams using corrugated GFRP laminates and the results are compared. Mathematical models were developed based on the experimental data and then the models were validated.

  10. New generation fiber reinforced polymer composites incorporating carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Soliman, Eslam

    The last five decades observed an increasing use of fiber reinforced polymer (FRP) composites as alternative construction materials for aerospace and infrastructure. The high specific strength of FRP attracted its use as non-corrosive reinforcement. However, FRP materials were characterized with a relatively low ductility and low shear strength compared with steel reinforcement. On the other hand, carbon nanotubes (CNTs) have been introduced in the last decade as a material with minimal defect that is capable of increasing the mechanical properties of polymer matrices. This dissertation reports experimental investigations on the use of multi-walled carbon nanotubes (MWCNTs) to produce a new generation of FRP composites. The experiments showed significant improvements in the flexure properties of the nanocomposite when functionalized MWCNTs were used. In addition, MWCNTs were used to produce FRP composites in order to examine static, dynamic, and creep behavior. The MWCNTs improved the off-axis tension, off-axis flexure, FRP lap shear joint responses. In addition, they reduced the creep of FRP-concrete interface, enhanced the fracture toughness, and altered the impact resistance significantly. In general, the MWCNTs are found to affect the behaviour of the FRP composites when matrix failure dominates the behaviour. The improvement in the mechanical response with the addition of low contents of MWCNTs would benefit many industrial and military applications such as strengthening structures using FRP composites, composite pipelines, aircrafts, and armoured vehicles.

  11. State-of-Practice on the Dynamic Response of Structures Strengthened with Fiber Reinforced Polymers (FRPs)

    DTIC Science & Technology

    2015-07-01

    ER D C/ G SL S R- 15 -2 State-of-Practice on the Dynamic Response of Structures Strengthened with Fiber Reinforced Polymers (FRPs) G...Reinforced Polymers (FRPs) Robert D. Moser, C. Kennan Crane, Brian H. Green Geotechnical and Structures Laboratory U.S. Army Engineer Research and...unlimited. Prepared for U.S. Army Corps of Engineers Washington, DC 20314-1000 ERDC/GSL SR-15-2 ii Abstract Fiber Reinforced Polymers (FRPs) are

  12. Tungsten disulfide nanotubes reinforced biodegradable polymers for bone tissue engineering.

    PubMed

    Lalwani, Gaurav; Henslee, Allan M; Farshid, Behzad; Parmar, Priyanka; Lin, Liangjun; Qin, Yi-Xian; Kasper, F Kurtis; Mikos, Antonios G; Sitharaman, Balaji

    2013-09-01

    In this study, we have investigated the efficacy of inorganic nanotubes as reinforcing agents to improve the mechanical properties of poly(propylene fumarate) (PPF) composites as a function of nanomaterial loading concentration (0.01-0.2 wt.%). Tungsten disulfide nanotubes (WSNTs) were used as reinforcing agents in the experimental group. Single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs) were used as positive controls, and crosslinked PPF composites were used as the baseline control. Mechanical testing (compression and three-point bending) shows a significant enhancement (up to 28-190%) in the mechanical properties (compressive modulus, compressive yield strength, flexural modulus and flexural yield strength) of WSNT-reinforced PPF nanocomposites compared to the baseline control. In comparison to the positive controls, significant improvements in the mechanical properties of WSNT nanocomposites were also observed at various concentrations. In general, the inorganic nanotubes (WSNTs) showed mechanical reinforcement better than (up to 127%) or equivalent to that of carbon nanotubes (SWCNTs and MWCNTs). Sol fraction analysis showed significant increases in the crosslinking density of PPF in the presence of WSNTs (0.01-0.2 wt.%). Transmission electron microscopy (TEM) analysis on thin sections of crosslinked nanocomposites showed the presence of WSNTs as individual nanotubes in the PPF matrix, whereas SWCNTs and MWCNTs existed as micron-sized aggregates. The trend in the surface area of nanostructures obtained by Brunauer-Emmett-Teller (BET) surface area analysis was SWCNTs>MWCNTs>WSNTs. The BET surface area analysis, TEM analysis and sol fraction analysis results taken together suggest that chemical composition (inorganic vs. carbon nanomaterials), the presence of functional groups (such as sulfide and oxysulfide) and individual dispersion of the nanomaterials in the polymer matrix (absence of aggregation of the reinforcing agent) are the key parameters

  13. Studies on natural fiber reinforced polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Kapatel, P. M.; Machchhar, A. D.; Kapatel, Y. A.

    2016-05-01

    Natural fiber reinforced composites show increasing importance in day to days applications because of their low cost, lightweight, easy availability, non-toxicity, biodegradability and environment friendly nature. But these fibers are hydrophilic in nature. Thus they have very low reactivity and poor compatibility with polymers. To overcome these limitations chemical modifications of the fibers have been carried out. Therefore, in the present work jute fibers have chemically modified by treating with sodium hydroxide (NaOH) solutions. These treated jute fibers have been used to fabricate jute fiber reinforced epoxy composites. Mechanical properties like tensile strength, flexural strength and impact strength have been found out. Alkali treated composites show better properties compare to untreated composites.

  14. Interface Characterization in Fiber-Reinforced Polymer-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Naya, F.; Molina-Aldareguía, J. M.; Lopes, C. S.; González, C.; LLorca, J.

    2017-01-01

    A novel methodology is presented and applied to measure the shear interface strength of fiber-reinforced polymers. The strategy is based in fiber push-in tests carried out on the central fiber of highly-packed fiber clusters with hexagonal symmetry, and it is supported by a detailed finite element analysis of the push-in test to account for the influence of hygrothermal residual stresses, fiber constraint and fiber anisotropy on the interface strength. Examples of application are presented to determine the shear interface strength in carbon and glass fiber composites reinforced with either thermoset or thermoplastic matrices. In addition, the influence of the environment (either dry or wet conditions) on the interface strength in C/epoxy composites is demonstrated.

  15. Defect depth measurement of carbon fiber reinforced polymers by thermography

    NASA Astrophysics Data System (ADS)

    Chen, Terry Y.; Chen, Jian-Lun

    2016-01-01

    Carbon fiber reinforced polymers has been widely used in all kind of the industries. However the internal defects can result in the change of material or mechanical properties, and cause safety problem. In this study, step-heating thermography is employed to measure the time series temperature distribution of composite plate. The principle of heat conduction in a flat plate with defect inside is introduced. A temperature separation criterion to determine the depth of defect inside the specimen is obtained experimentally. Applying this criterion to CFRP specimens with embedded defects, the depth of embedded defect in CFRP can be determined quite well from the time series thermograms obtained experimentally.

  16. Optimization of Al Matrix Reinforced with B4C Particles

    NASA Astrophysics Data System (ADS)

    Shabani, Mohsen Ostad; Mazahery, Ali

    2013-02-01

    In the current study, abrasive wear resistance and mechanical properties of A356 composite reinforced with B4C particulates were investigated. A center particle swarm optimization algorithm (CenterPSO) is proposed to predict the optimal process conditions in fabrication of aluminum matrix composites. Unlike other ordinary particles, the center particle has no explicit velocity and is set to the center of the swarm at every iteration. Other aspects of the center particle are the same as that of the ordinary particle, such as fitness evaluation and competition for the best particle of the swarm. Because the center of the swarm is a promising position, the center particle generally gets good fitness value. More importantly, due to frequent appearance as the best particle of swarm, it often attracts other particles and guides the search direction of the whole swarm.

  17. Reinforcement of bacterial cellulose aerogels with biocompatible polymers

    PubMed Central

    Pircher, N.; Veigel, S.; Aigner, N.; Nedelec, J.M.; Rosenau, T.; Liebner, F.

    2014-01-01

    Bacterial cellulose (BC) aerogels, which are fragile, ultra-lightweight, open-porous and transversally isotropic materials, have been reinforced with the biocompatible polymers polylactic acid (PLA), polycaprolactone (PCL), cellulose acetate (CA), and poly(methyl methacrylate) (PMMA), respectively, at varying BC/polymer ratios. Supercritical carbon dioxide anti-solvent precipitation and simultaneous extraction of the anti-solvent using scCO2 have been used as core techniques for incorporating the secondary polymer into the BC matrix and to convert the formed composite organogels into aerogels. Uniaxial compression tests revealed a considerable enhancement of the mechanical properties as compared to BC aerogels. Nitrogen sorption experiments at 77 K and scanning electron micrographs confirmed the preservation (or even enhancement) of the surface-area-to-volume ratio for most of the samples. The formation of an open-porous, interpenetrating network of the second polymer has been demonstrated by treatment of BC/PMMA hybrid aerogels with EMIM acetate, which exclusively extracted cellulose, leaving behind self-supporting organogels. PMID:25037381

  18. Adhesion between thermoplastic polymer particles and carbon and glass fibers

    SciTech Connect

    Colton, J.S.

    1996-12-31

    High performance composites consist of polymer matrices reinforced with continuous fibers. Polymer powders can be coated and fused onto the fibers by various techniques to produce these composites. One such technique consists of spreading the fibers with an air banding jet, and then running the fibers through a fluidized bed of the powder. The fluidizing air is typically charged, imparting a charge to the powder particles. The fibers are grounded which leads to an attraction between the particles and the fibers. The particle-coated fibers then go through a tunnel oven, sintering the particles onto the fibers, leaving a flexible {open_quotes}tow-preg{close_quotes} which can then be processed into a preform for manufacture into a final part. To develop an initial understanding of the powder coating process, the adhesion of uncharged particles and fibers was studied. Contact mechanics predicts that the adhesion force between uncharged particles depends on the mutual (or equivalent) radius of curvature between the contacting objects, as well as their surface energies. For the materials of interest, the Derjaguin approximation is appropriate and is applied. PEEK (poly ether ether ketone) and PET (poly ethylene terephthalate) particles, cryogenically ground to nominal diameters of 10 to 100 {mu}m were brought into contact with themselves, with E-glass fibers (nominal diameter of 20 {mu}m), carbon fibers (nominal diameter of 8 {mu}m), and glass microscope slides using an AFM. Adhesion forces were measured and compared to predictions using Derjaguin`s approximation. SEM micrographs were used to determine the scale of the radii of curvature of contacting sites.

  19. Electroacoustics of Particles Dispersed in Polymer Gel

    SciTech Connect

    Bhosale, Prasad S.; Chun, Jaehun; Berg, John C.

    2011-06-27

    This study examines the acoustic electrophoresis of particles dispersed in polymer hydrogels, with the particle size either less than or greater than the gel mesh size. When the particles are smaller than the gel mesh size, their acoustic vibration is resisted by only the background water medium, and the measured dynamic electrophoretic mobility, μd (obtained in terms of colloid vibration current, CVI), is the same as in water. For the case of particles larger than the gel mesh size, μd is decreased due to trapping, and the net decrease depends on the viscoelastic properties of the gel. The gel mesh size was varied by varying its crosslink density, the latter being characterized as the storage modulus, G’. The dependence of mobility on G’, for systems of a given particle size, and on particle size, for gels of a given G’, are investigated. The measured mobility remains constant as G’ is increased (i.e., mesh size is decreased) up to a value of approximately 300 Pa, beyond which it decreases. In the second set of measurements, the trapped particle size was increased in a gel medium of constant mesh size, with G’ approximately 100 Pa. In this case, the measured μd is found to be effectively constant over the particle size range studied (14-120 nm), i.e., it is independent of the degree of trapping as expressed by the ratio of the particle size to the mesh size.

  20. Nondestructive testing of externally reinforced structures for seismic retrofitting using flax fiber reinforced polymer (FFRP) composites

    NASA Astrophysics Data System (ADS)

    Ibarra-Castanedo, C.; Sfarra, S.; Paoletti, D.; Bendada, A.; Maldague, X.

    2013-05-01

    Natural fibers constitute an interesting alternative to synthetic fibers, e.g. glass and carbon, for the production of composites due to their environmental and economic advantages. The strength of natural fiber composites is on average lower compared to their synthetic counterparts. Nevertheless, natural fibers such as flax, among other bast fibers (jute, kenaf, ramie and hemp), are serious candidates for seismic retrofitting applications given that their mechanical properties are more suitable for dynamic loads. Strengthening of structures is performed by impregnating flax fiber reinforced polymers (FFRP) fabrics with epoxy resin and applying them to the component of interest, increasing in this way the load and deformation capacities of the building, while preserving its stiffness and dynamic properties. The reinforced areas are however prompt to debonding if the fabrics are not mounted properly. Nondestructive testing is therefore required to verify that the fabric is uniformly installed and that there are no air gaps or foreign materials that could instigate debonding. In this work, the use of active infrared thermography was investigated for the assessment of (1) a laboratory specimen reinforced with FFRP and containing several artificial defects; and (2) an actual FFRP retrofitted masonry wall in the Faculty of Engineering of the University of L'Aquila (Italy) that was seriously affected by the 2009 earthquake. Thermographic data was processed by advanced signal processing techniques, and post-processed by computing the watershed lines to locate suspected areas. Results coming from the academic specimen were compared to digital speckle photography and holographic interferometry images.

  1. Particle size and particle-particle interactions on tensile properties and reinforcement of corn flour particles in natural rubber

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Renewable corn flour has a significant reinforcement effect in natural rubber. The corn flour was hydrolyzed and microfluidized to reduce its particle size. Greater than 90% of the hydrolyzed corn flour had an average size of ~300 nm, a reduction of 33 times compared to unhydrolyzed corn flour. Comp...

  2. Behaviour of fibre reinforced polymer confined reinforced concrete columns under fire condition

    NASA Astrophysics Data System (ADS)

    Chowdhury, Ershad Ullah

    In recent years, fibre reinforced polymer (FRP) materials have demonstrated enormous potential as materials for repairing and retrofitting concrete bridges that have deteriorated from factors such as electro-chemical corrosion and increased load requirements. However, concerns associated with fire remain an obstacle to applications of FRP materials in buildings and parking garages due to FRP's sensitivity to high temperatures as compared with other structural materials and to limited knowledge on their thermal and mechanical behaviour in fire. This thesis presents results from an ongoing study on the fire performance of FRP materials, fire insulation materials and systems, and FRP wrapped reinforced concrete columns. The overall goal of the study is to understand the fire behaviour of FRP materials and FRP strengthened concrete columns and ultimately, provide rational fire safety design recommendations and guidelines for FRP strengthened concrete columns. A combined experimental and numerical investigation was conducted to achieve the goals of this research study. The experimental work consisted of both small-scale FRP material testing at elevated temperatures and full-scale fire tests on FRP strengthened columns. A numerical model was developed to simulate the behaviour of unwrapped reinforced concrete and FRP strengthened reinforced concrete square or rectangular columns in fire. After validating the numerical model against test data available in literature, it was determined that the numerical model can be used to analyze the behaviour of concrete axial compressive members in fire. Results from this study also demonstrated that although FRP materials experience considerable loss of their mechanical and bond properties at temperatures somewhat below the glass transition temperature of the resin matrix, externally-bonded FRP can be used in strengthening concrete structural members in buildings, if appropriate supplemental fire protection system is provided over

  3. A self-sensing fiber reinforced polymer composite using mechanophore-based smart polymer

    NASA Astrophysics Data System (ADS)

    Zou, Jin; Liu, Yingtao; Chattopadhyay, Aditi; Dai, Lenore

    2015-04-01

    Polymer matrix composites (PMCs) are ubiquitous in engineering applications due to their superior mechanical properties at low weight. However, they are susceptible to damage due to their low interlaminar mechanical properties and poor heat and charge transport in the transverse direction to the laminate. Moreover, methods to inspect and ensure the reliability of composites are expensive and labor intensive. Recently, mechanophore-based smart polymer has attracted significant attention, especially for self-sensing of matrix damage in PMCs. A cyclobutane-based self-sensing approach using 1,1,1-tris (cinnamoyloxymethyl) ethane (TCE) and poly (vinyl cinnamate) (PVCi) has been studied in this paper. The self-sensing function was investigated at both the polymer level and composite laminate level. Fluorescence emissions were observed on PMC specimens subjected to low cycle fatigue load, indicating the presence of matrix cracks. Results are presented for graphite fiber reinforced composites.

  4. Durability Studies on Confined Concrete using Fiber Reinforced Polymer

    NASA Astrophysics Data System (ADS)

    Ponmalar, V.; Gettu, R.

    2014-06-01

    In this study, 24 concrete cylinders with a notch at the centre were prepared. Among them six cylinders were wrapped using single and double layers of fiber reinforced polymer; six cylinders were coated with epoxy resin; the remaining cylinders were used as a control. The cylinders were exposed to wet and dry cycling and acid (3 % H2SO4) solution for the period of 120 days. Two different concrete strengths M30 and M50 were considered for the study. It is found that the strength, ductility and failure mode of wrapped cylinders depend on number of layers and the nature of exposure conditions. It was noticed that the damage due to wet and dry cycling and acid attack was severe in control specimen than the epoxy coated and wrapped cylinders.

  5. Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection.

    PubMed

    Luo, Dong; Ibrahim, Zainah; Ma, Jianxun; Ismail, Zubaidah; Iseley, David Thomas

    2016-12-16

    In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM) system in civil engineering.

  6. Flexural analysis of palm fiber reinforced hybrid polymer matrix composite

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Raghav, Dasarath; Santhosh Kiran, R.; Mahesh, Bhargav; Kumar, Krishna

    2015-07-01

    Uncertainty in availability of fossil fuels in the future and global warming increased the need for more environment friendly materials. In this work, an attempt is made to fabricate a hybrid polymer matrix composite. The blend is a mixture of General Purpose Resin and Cashew Nut Shell Liquid, a natural resin extracted from cashew plant. Palm fiber, which has high strength, is used as reinforcement material. The fiber is treated with alkali (NaOH) solution to increase its strength and adhesiveness. Parametric study of flexure strength is carried out by varying alkali concentration, duration of alkali treatment and fiber volume. Taguchi L9 Orthogonal array is followed in the design of experiments procedure for simplification. With the help of ANOVA technique, regression equations are obtained which gives the level of influence of each parameter on the flexure strength of the composite.

  7. Objective Surface Evaluation of Fiber Reinforced Polymer Composites

    NASA Astrophysics Data System (ADS)

    Palmer, Stuart; Hall, Wayne

    2013-08-01

    The mechanical properties of advanced composites are essential for their structural performance, but the surface finish on exterior composite panels is of critical importance for customer satisfaction. This paper describes the application of wavelet texture analysis (WTA) to the task of automatically classifying the surface finish properties of two fiber reinforced polymer (FRP) composite construction types (clear resin and gel-coat) into three quality grades. Samples were imaged and wavelet multi-scale decomposition was used to create a visual texture representation of the sample, capturing image features at different scales and orientations. Principal components analysis was used to reduce the dimensionality of the texture feature vector, permitting successful classification of the samples using only the first principal component. This work extends and further validates the feasibility of this approach as the basis for automated non-contact classification of composite surface finish using image analysis.

  8. Nano-Fiber Reinforced Enhancements in Composite Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2009-01-01

    Nano-fibers are used to reinforce polymer matrices to enhance the matrix dependent properties that are subsequently used in conventional structural composites. A quasi isotropic configuration is used in arranging like nano-fibers through the thickness to ascertain equiaxial enhanced matrix behavior. The nano-fiber volume ratios are used to obtain the enhanced matrix strength properties for 0.01,0.03, and 0.05 nano-fiber volume rates. These enhanced nano-fiber matrices are used with conventional fiber volume ratios of 0.3 and 0.5 to obtain the composite properties. Results show that nano-fiber enhanced matrices of higher than 0.3 nano-fiber volume ratio are degrading the composite properties.

  9. Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection

    PubMed Central

    Luo, Dong; Ibrahim, Zainah; Ma, Jianxun; Ismail, Zubaidah; Iseley, David Thomas

    2016-01-01

    In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM) system in civil engineering. PMID:27999245

  10. Integral equation study of particle confinement effects in a polymer/particle mixture

    SciTech Connect

    Henderson, D; Trokhymchuk, A; Kalyuzhnyi, Y; Gee, R; Lacevic, N

    2007-05-09

    Integral equation theory techniques are applied to evaluate the structuring of the polymer when large solid particles are embedded into a bulk polymer melt. The formalism presented here is applied to obtain an insight into the filler particle aggregation tendency. We find that with the employed polymer-particle interaction model it is very unlikely that the particles will aggregate. We believe that in such a system aggregation and clustering can occur when the filler particles are dressed by tightly bound polymer layers.

  11. On Healable Polymers and Fiber-Reinforced Composites

    NASA Astrophysics Data System (ADS)

    Nielsen, Christian Eric

    Polymeric materials capable of healing damage would be valuable in structural applications where access for repair is limited. Approaches to creating such materials are reviewed, with the present work focusing on polymers with thermally reversible covalent cross-links. These special cross-links are Diels-Alder (DA) adducts, which can be separated and re-formed, enabling healing of mechanical damage at the molecular level. Several DA-based polymers, including 2MEP4FS, are mechanically and thermally characterized. The polymerization reaction of 2MEP4FS is modeled and the number of established DA adducts is associated with the glass transition temperature of the polymer. The models are applied to concentric cylinder rotational measurements of 2MEP4FS prepolymer at room and elevated temperatures to describe the viscosity as a function of time, temperature, and conversion. Mechanical damage including cracks and scratches are imparted in cured polymer samples and subsequently healed. Damage due to high temperature thermal degradation is observed to not be reversible. The ability to repair damage without flowing polymer chains makes DA-based healable polymers particularly well-suited for crack healing. The double cleavage drilled compression (DCDC) fracture test is investigated as a useful method of creating and incrementally growing cracks in a sample. The effect of sample geometry on the fracture behavior is experimentally and computationally studied. Computational and empirical models are developed to estimate critical stress intensity factors from DCDC results. Glass and carbon fiber-reinforced composites are fabricated with 2MEP4FS as the matrix material. A prepreg process is developed that uses temperature to control the polymerization rate of the monomers and produce homogeneous prepolymer for integration with a layer of unidirectional fiber. Multiple prepreg layers are laminated to form multi-layered cross-ply healable composites, which are characterized in

  12. Polymer-Reinforced, Non-Brittle, Lightweight Cryogenic Insulation

    NASA Technical Reports Server (NTRS)

    Hess, David M.

    2013-01-01

    The primary application for cryogenic insulating foams will be fuel tank applications for fueling systems. It is crucial for this insulation to be incorporated into systems that survive vacuum and terrestrial environments. It is hypothesized that by forming an open-cell silica-reinforced polymer structure, the foam structures will exhibit the necessary strength to maintain shape. This will, in turn, maintain the insulating capabilities of the foam insulation. Besides mechanical stability in the form of crush resistance, it is important for these insulating materials to exhibit water penetration resistance. Hydrocarbon-terminated foam surfaces were implemented to impart hydrophobic functionality that apparently limits moisture penetration through the foam. During the freezing process, water accumulates on the surfaces of the foams. However, when hydrocarbon-terminated surfaces are present, water apparently beads and forms crystals, leading to less apparent accumulation. The object of this work is to develop inexpensive structural cryogenic insulation foam that has increased impact resistance for launch and ground-based cryogenic systems. Two parallel approaches will be pursued: a silica-polymer co-foaming technique and a post foam coating technique. Insulation characteristics, flexibility, and water uptake can be fine-tuned through the manipulation of the polyurethane foam scaffold. Silicate coatings for polyurethane foams and aerogel-impregnated polyurethane foams have been developed and tested. A highly porous aerogel-like material may be fabricated using a co-foam and coated foam techniques, and can insulate at liquid temperatures using the composite foam

  13. Flexural strength,water sorption and solubility of a methylmethacrylate-free denture base polymer reinforced with glass fibre reinforcement.

    PubMed

    Mutluay, M M; Tezvergil-Mutluay, A; Vallittu, P; Lassila, L

    2013-12-01

    A methylmethacrylate-free denture base polymer (Eclipse) in comparison to a conventional denture base polymer (Palapress vario) was evaluated after water saturation and Stick glass fibre reinforcement. The data were analysed with ANOVA at a = 0.05. Water-storage caused a decrease in the flexural strength and stiffness of the materials (p > 0.05). Conventional denture base material with fibre reinforcement gave highest flexural strength (201.1 MPa) compared to fibre reinforced Eclipse (79.1 MPa) (p < 0.05). Water sorption after 76 days was 2.08% (Palapress vario) and 1.55% (Eclipse). Fibre-reinforcement of methylmethacrylate-free material was not as successful as conventional denture base and needs to be further optimized.

  14. A review on the cords & plies reinforcement of elastomeric polymer matrix

    NASA Astrophysics Data System (ADS)

    Mahmood, S. S.; Husin, H.; Mat-Shayuti, M. S.; Hassan, Z.

    2016-06-01

    Steel, polyester, nylon and rayon are the main materials of cords & plies that have been reinforced in the natural rubber to produce quality tyres but there is few research reported on cord and plies reinforcement in silicone rubber. Taking the innovation of tyres as inspiration, this review's first objective is to compile the comprehensive studies about the cords & plies reinforcement in elastomeric polymer matrix. The second objective is to gather information about silicone rubber that has a high potential as a matrix phase for cords and plies reinforcement. All the tests and findings are gathered and compiled in sections namely processing preparation, curing, physical and mechanical properties, and adhesion between cords-polymer.

  15. Tensile properties of glass/natural jute fibre-reinforced polymer bars for concrete reinforcement

    NASA Astrophysics Data System (ADS)

    Han, J. W.; Lee, S. K.; Kim, K. W.; Park, C. G.

    2015-12-01

    The tensile performance of glass/natural jute fibre-reinforced polymer (FRP) bar, intended for concrete reinforcement was evaluated as a function of volume fraction of natural jute fibre. Natural jute fibre, mixed at a ratio of 7:3 with vinyl ester, was surface-treated with a silane coupling agent and used to replaced glass fibre in the composite in volume fractions of 0%, 30%, 50%, 70%, and 100%. The tensile load-displacement curve showed nearly linear elastic behaviour up to 50% natural jute fibre, but was partially nonlinear at a proportion of 70%. However, the glass/natural jute FRP bars prepared using 100% natural jute fibre showed linear elastic behaviour. Tensile strength decreased as the natural jute fibre volume fraction increased because the tensile strength of natural jute fibre is much lower than that of glass fibre (about 1:8.65). The degree of reduction was not proportional to the natural jute fibre volume fraction due to the low density of natural jute fibre (1/2 that of glass fibre). Thus, as the mix proportion of natural jute fibre increased, the amount (wt%) and number of fibres used also increased.

  16. Aramid nanofiber-functionalized graphene nanosheets for polymer reinforcement

    NASA Astrophysics Data System (ADS)

    Fan, Jinchen; Shi, Zixing; Zhang, Lu; Wang, Jialiang; Yin, Jie

    2012-10-01

    Aramid macroscale fibers, also called Kevlar fibers, exhibit extremely high mechanical performance. Previous studies have demonstrated that bulk aramid macroscale fibers can be effectively split into aramid nanofibers (ANFs) by dissolution in dimethylsulfoxide (DMSO) in the presence of potassium hydroxide (KOH). In this paper, we first introduced the ANFs into the structure of graphene nanosheets through non-covalent functionalization through π-π stacking interactions. Aramid nanofiber-functionalized graphene sheets (ANFGS) were successfully obtained by adding the graphene oxide (GO)/DMSO dispersion into the ANFs/DMSO solution followed by reduction with hydrazine hydrate. The ANFGS, with ANFs absorbed on the surface of the graphene nanosheets, can be easily exfoliated and dispersed in N-methyl-2-pyrrolidone (NMP). Through a combination of these two ultra-strong materials, ANFs and graphene nanosheets (GS), the resultant ANFGS can act as novel nanofillers for polymer reinforcement. We used the ANFGS as an additive for reinforcing the mechanical properties of poly(methyl methacrylate) (PMMA). With a loading of 0.7 wt% of the ANFGS, the tensile strength and Young's modulus of the ANFGS/PMMA composite film approached 63.2 MPa and 3.42 GPa, which are increases of ~84.5% and ~70.6%, respectively. The thermal stabilities of ANFGS/PMMA composite films were improved by the addition of ANFGS. Additionally, the transparencies of the ANFGS/PMMA composite films have a degree of UV-shielding due to the ultraviolet light absorption of the ANFs in the ANFGS.Aramid macroscale fibers, also called Kevlar fibers, exhibit extremely high mechanical performance. Previous studies have demonstrated that bulk aramid macroscale fibers can be effectively split into aramid nanofibers (ANFs) by dissolution in dimethylsulfoxide (DMSO) in the presence of potassium hydroxide (KOH). In this paper, we first introduced the ANFs into the structure of graphene nanosheets through non

  17. 3D Finite Element Analysis of Particle-Reinforced Aluminum

    NASA Technical Reports Server (NTRS)

    Shen, H.; Lissenden, C. J.

    2002-01-01

    Deformation in particle-reinforced aluminum has been simulated using three distinct types of finite element model: a three-dimensional repeating unit cell, a three-dimensional multi-particle model, and two-dimensional multi-particle models. The repeating unit cell model represents a fictitious periodic cubic array of particles. The 3D multi-particle (3D-MP) model represents randomly placed and oriented particles. The 2D generalized plane strain multi-particle models were obtained from planar sections through the 3D-MP model. These models were used to study the tensile macroscopic stress-strain response and the associated stress and strain distributions in an elastoplastic matrix. The results indicate that the 2D model having a particle area fraction equal to the particle representative volume fraction of the 3D models predicted the same macroscopic stress-strain response as the 3D models. However, there are fluctuations in the particle area fraction in a representative volume element. As expected, predictions from 2D models having different particle area fractions do not agree with predictions from 3D models. More importantly, it was found that the microscopic stress and strain distributions from the 2D models do not agree with those from the 3D-MP model. Specifically, the plastic strain distribution predicted by the 2D model is banded along lines inclined at 45 deg from the loading axis while the 3D model prediction is not. Additionally, the triaxial stress and maximum principal stress distributions predicted by 2D and 3D models do not agree. Thus, it appears necessary to use a multi-particle 3D model to accurately predict material responses that depend on local effects, such as strain-to-failure, fracture toughness, and fatigue life.

  18. Aramid nanofiber-functionalized graphene nanosheets for polymer reinforcement.

    PubMed

    Fan, Jinchen; Shi, Zixing; Zhang, Lu; Wang, Jialiang; Yin, Jie

    2012-11-21

    Aramid macroscale fibers, also called Kevlar fibers, exhibit extremely high mechanical performance. Previous studies have demonstrated that bulk aramid macroscale fibers can be effectively split into aramid nanofibers (ANFs) by dissolution in dimethylsulfoxide (DMSO) in the presence of potassium hydroxide (KOH). In this paper, we first introduced the ANFs into the structure of graphene nanosheets through non-covalent functionalization through π-π stacking interactions. Aramid nanofiber-functionalized graphene sheets (ANFGS) were successfully obtained by adding the graphene oxide (GO)/DMSO dispersion into the ANFs/DMSO solution followed by reduction with hydrazine hydrate. The ANFGS, with ANFs absorbed on the surface of the graphene nanosheets, can be easily exfoliated and dispersed in N-methyl-2-pyrrolidone (NMP). Through a combination of these two ultra-strong materials, ANFs and graphene nanosheets (GS), the resultant ANFGS can act as novel nanofillers for polymer reinforcement. We used the ANFGS as an additive for reinforcing the mechanical properties of poly(methyl methacrylate) (PMMA). With a loading of 0.7 wt% of the ANFGS, the tensile strength and Young's modulus of the ANFGS/PMMA composite film approached 63.2 MPa and 3.42 GPa, which are increases of ∼84.5% and ∼70.6%, respectively. The thermal stabilities of ANFGS/PMMA composite films were improved by the addition of ANFGS. Additionally, the transparencies of the ANFGS/PMMA composite films have a degree of UV-shielding due to the ultraviolet light absorption of the ANFs in the ANFGS.

  19. Solidification of particle-reinforced metal-matrix composites

    NASA Astrophysics Data System (ADS)

    Hanumanth, G. S.; Irons, G. A.

    1996-08-01

    The solidification behavior of ceramic particle-reinforced metal-matrix composites (MMCs) is different from that of the bare matrix, not only because of the presence of the ceramic particles, but also due to their redistribution in the melt that results in nonhomogeneous thermophysical properties. The MMCs comprised of 10-to 15-μm SiC particles of varying volume fractions, dispersed uniformly in a modified aluminum A356 alloy by the melt stirring technique, were solidified unidirectionally in a thermocouple-instrumented cylindrical steel mold. The cooling rates were continually monitored by measuring temperatures at different depths in the melt, and the solidified MMCs were sectioned into disks and chemically analyzed for SiC volume fraction. The results point out that the cooling rate increased with increasing volume fraction of SiC particles. A small increase in the bulk SiC volume fraction of the cast MMC was observed due to particle settling during solidification. A one-dimensional enthalpy model of MMC solidification was formulated, wherein particle settling occurring in the solidifying matrix was coupled to the enthalpy equation by means of the Richardson-Zaki hindered settling correlation. A comparative study of simulations with experiments suggested that the thermal response of SiC particles used in this study was similar to that of single crystals, and their presence increased the effective thermal conductivity of the composite.

  20. Nondestructive Evaluation of Advanced Fiber Reinforced Polymer Matrix Composites: A Technology Assessment

    NASA Technical Reports Server (NTRS)

    Yolken, H. Thomas; Matzkanin, George A.

    2009-01-01

    Because of their increasing utilization in structural applications, the nondestructive evaluation (NDE) of advanced fiber reinforced polymer composites continues to receive considerable research and development attention. Due to the heterogeneous nature of composites, the form of defects is often very different from a metal and fracture mechanisms are more complex. The purpose of this report is to provide an overview and technology assessment of the current state-of-the-art with respect to NDE of advanced fiber reinforced polymer composites.

  1. Life Cycle Assessment of Carbon Fiber-Reinforced Polymer Composites

    SciTech Connect

    Das, Sujit

    2011-01-01

    Carbon fiber-reinforced polymer matrix composites is gaining momentum with the pressure to lightweight vehicles, however energy-intensity and cost remain some of the major barriers before this material could be used in large-scale automotive applications. A representative automotive part, i.e., a 30.8 kg steel floor pan having a 17% weight reduction potential with stringent cash performance requirements has been considered for the life cycle energy and emissions analysis based on the latest developments occurring in the precursor type (conventional textile-based PAN vs. renewable-based lignin), part manufacturing (conventional SMC vs. P4) and fiber recycling technologies. Carbon fiber production is estimated to be about 14 times more energy-intensive than conventional steel production, however life cycle primary energy use is estimated to be quite similar to the conventional part, i.e., 18,500 MJ/part, especially when considering the uncertainty in LCI data that exists from using numerous sources in the literature. Lignin P4 technology offers the most life cycle energy and CO2 emissions benefits compared to a conventional stamped steel technology. With a 20% reduction in energy use in the lignin conversion to carbon fiber and free availability of lignin as a by-product of ethanol and wood production, a 30% reduction in life cycle energy use could be obtained. A similar level of life cycle energy savings could also be obtained with a higher part weight reduction potential of 43%.

  2. Thermal diffusivity measurements on porous carbon fiber reinforced polymer tubes

    NASA Astrophysics Data System (ADS)

    Gruber, Jürgen; Gresslehner, Karl Heinz; Mayr, Günther; Hendorfer, Günther

    2017-02-01

    This work presents the application of methods for the determination of the thermal diffusivity well suited for flat bodies adapted to cylindrical bodies. Green's functions were used to get the temperature time history for small and large times, for the approach of intersecting these two straight lines. To verify the theoretical considerations noise free data are generated by finite element simulations. Furthermore effects of inhomogeneous excitation and the anisotropic heat conduction of carbon fiber reinforced polymers were taken into account in these numerical simulations. It could be shown that the intersection of the two straight lines is suitable for the determination of the thermal diffusivity, although the results have to be corrected depending on the ratio of the cylinders inner and outer radii. Inhomogeneous excitation affects the results of this approach as it lead to multidimensional heat flux. However, based on the numerical simulations a range of the azimuthal angle exists, where the thermal diffusivity is nearly independent of the angle. The method to determine the thermal diffusivity for curved geometries by the well suited Thermographic Signal Reconstruction method and taking into account deviations from the slab by a single correction factor has great advantages from an industrial point of view, just like an easy implementation into evaluation software and the Thermographic Signal Reconstruction methods rather short processing time.

  3. Reinforced poly(propylene oxide): a very soft and extensible dielectric electroactive polymer

    NASA Astrophysics Data System (ADS)

    Goswami, K.; Galantini, F.; Mazurek, P.; Daugaard, A. E.; Gallone, G.; Skov, A. L.

    2013-11-01

    Poly(propylene oxide) (PPO), a novel soft elastomeric material, and its composites were investigated as a new dielectric electroactive polymer (EAP). The PPO networks were obtained from thiol-ene chemistry by photochemical crosslinking of α,ω-diallyl PPO with a tetra-functional thiol. The elastomer was reinforced with hexamethylenedisilazane treated fumed silica to improve the mechanical properties of PPO. The mechanical properties of PPO and composites thereof were investigated by shear rheology and stress-strain measurements. It was found that incorporation of silica particles improved the stability of the otherwise mechanically weak pure PPO network. Dielectric spectroscopy revealed high relative dielectric permittivity of PPO at 103 Hz of 5.6. The relative permittivity was decreased slightly upon addition of fillers, but remained higher than the commonly used acrylic EAP material VHB4910. The electromechanical actuation performance of both PPO and its composites showed properties as good as VHB4910 and a lower viscous loss.

  4. Shock compression behavior of a S2-glass fiber reinforced polymer composite

    NASA Astrophysics Data System (ADS)

    Tsai, Liren; Yuan, Fuping; Prakash, Vikas; Dandekar, Dattatraya P.

    2009-05-01

    Synthetic heterogeneous material systems, e.g., layered composite materials with organic matrices reinforced by glass fibers (GRP), are attractive materials for a variety of lightweight armor applications. However, while the dynamic response of homogeneous materials, such as, metals and ceramics, has been well documented, the ballistic response of heterogeneous material systems is poorly understood. In the present study, in an attempt to better understand the shock-induced compression response of GRPs, a series of plate impact experiments were conducted on a S2-glas fiber reinforced polymer composite comprising S2-glass woven roving in a Cycom 4102 polyester resin matrix. The plate-impact experiments were conducted using an 82.5 mm bore single-stage gas-gun at the Case Western Reserve University. The history of the shock-induced free-surface particle velocity at the rear surface of the target plate was monitored using the multibeam VALYN™ VISAR system. The results of the experiments indicate the absence of an elastic front in the shock-induced free-surface particle velocity profile in the GRP. Moreover, in the low impact velocity range, relatively weak late-time oscillations are observed in the particle velocity profiles. Increasing the amplitude of the shock-induced compression resulted in a decrease in the rise-time of the shock wave front. The critical shock stress amplitude at which a clear shock-front is seen to develop during the shock loading was determined to be between 1.5 and 2.0 GPa. The results of the experiments are used to obtain the equation of state of the GRP in the stress range 0.04-20 GPa. Moreover, the Hugoniot curve (Hugoniot stress versus Hugoniot strain) was calculated using the Rankine-Hugoniot relationships; the departure of the Hugoniot stress versus the particle velocity curve from linearity allowed the estimation of the Hugoniot elastic limit of the GRP to be about 1.6 GPa.

  5. Exposure Assessment of a High-energy Tensile Test With Large Carbon Fiber Reinforced Polymer Cables.

    PubMed

    Schlagenhauf, Lukas; Kuo, Yu-Ying; Michel, Silvain; Terrasi, Giovanni; Wang, Jing

    2015-01-01

    This study investigated the particle and fiber release from two carbon fiber reinforced polymer cables that underwent high-energy tensile tests until rupture. The failing event was the source of a large amount of dust whereof a part was suspected to be containing possibly respirable fibers that could cause adverse health effects. The released fibers were suspected to migrate through small openings to the experiment control room and also to an adjacent machine hall where workers were active. To investigate the fiber release and exposure risk of the affected workers, the generated particles were measured with aerosol devices to obtain the particle size and particle concentrations. Furthermore, particles were collected on filter samples to investigate the particle shape and the fiber concentration. Three situations were monitored for the control room and the machine hall: the background concentrations, the impact of the cable failure, and the venting of the exposed rooms afterward. The results showed four important findings: The cable failure caused the release of respirable fibers with diameters below 3 μm and an average length of 13.9 μm; the released particles did migrate to the control room and to the machine hall; the measured peak fiber concentration of 0.76 fibers/cm(3) and the overall fiber concentration of 0.07 fibers/cm(3) in the control room were below the Permissible Exposure Limit (PEL) for fibers without indication of carcinogenicity; and the venting of the rooms was fast and effective. Even though respirable fibers were released, the low fiber concentration and effective venting indicated that the suspected health risks from the experiment on the affected workers was low. However, the effect of long-term exposure is not known therefore additional control measures are recommended.

  6. Structure-processing-property relationships for polymer interphases in fiber reinforced composite materials

    SciTech Connect

    Drzal, L.T.

    1995-12-31

    When polymer matrix composite materials are fabricated, polymers are processed to surround each reinforcing element while they are fluid and then they solidify in intimate contact with the reinforcement surface. For thermoset matrices, chemisorption of constituents, segregation of components. and processing constraints all can influence the resulting structure of the polymer in its solidified state. For thermoplastic matrices, segregation by molecular weight, morphological changes resulting from crystallization or additive segregation can also control the final matrix structure. In addition the surface of the fibers is coated with chemical agents that can also interact with the polymer. Examples will be given to illustrate the effect of the structure of this polymer interphase on adhesion. It will be shown that in some cases if the resulting polymer structure is known, adhesion and composite properties can be predicted.

  7. Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites

    SciTech Connect

    Cheng, Shiwang; Bocharova, Vera; Belianinov, Alex; Xiong, Shaomin; Kisliuk, Alexander; Somnath, Suhas; Holt, Adam P.; Ovchinnikova, Olga S.; Jesse, Stephen; Martin, Halie J.; Etampawala, Thusitha N.; Dadmun, Mark D.; Sokolov, Alexei P.

    2016-05-20

    The mechanical reinforcement of polymer nanocomposites (PNCs) above the glass transition temperature, Tg, has been extensively researched. However, not much is known about the origin of this effect below Tg. In this paper, we unravel the mechanism of PNC reinforcement within the glassy state by directly probing nanoscale mechanical properties with atomic force microscopy and macroscopic properties with Brillouin light scattering. Our results unambiguously show that the "glassy" Young's modulus in the interfacial polymer layer of PNCs is two-times higher than in the bulk polymer, which results in significant reinforcement below Tg. We ascribe this phenomenon to a high stretching of the chains within the interfacial layer. Since the interfacial chain packing is essentially temperature independent, these findings provide a new insight into the mechanical reinforcement of PNCs also above Tg.

  8. Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites

    DOE PAGES

    Cheng, Shiwang; Bocharova, Vera; Belianinov, Alex; ...

    2016-05-20

    The mechanical reinforcement of polymer nanocomposites (PNCs) above the glass transition temperature, Tg, has been extensively researched. However, not much is known about the origin of this effect below Tg. In this paper, we unravel the mechanism of PNC reinforcement within the glassy state by directly probing nanoscale mechanical properties with atomic force microscopy and macroscopic properties with Brillouin light scattering. Our results unambiguously show that the "glassy" Young's modulus in the interfacial polymer layer of PNCs is two-times higher than in the bulk polymer, which results in significant reinforcement below Tg. We ascribe this phenomenon to a high stretchingmore » of the chains within the interfacial layer. Since the interfacial chain packing is essentially temperature independent, these findings provide a new insight into the mechanical reinforcement of PNCs also above Tg.« less

  9. Macroscopic response of particle-reinforced elastomers subjected to prescribed torques or rotations on the particles

    NASA Astrophysics Data System (ADS)

    Siboni, Morteza H.; Ponte Castañeda, Pedro

    2016-06-01

    Particle-reinforced rubbers are composite materials consisting of randomly distributed, stiff fibers/particles in a soft elastomeric material. Since the particles are stiff compared to the embedding rubber, their deformation can be ignored for all practical purposes. However, due to the softness of the rubber, they can undergo rigid body translations and rotations. Constitutive models accounting for the effect of such particle motions on the macroscopic response under prescribed deformations on the boundary have been developed recently. But, in some applications (e.g., magneto-active elastomers), the particles may experience additional torques as a consequence of an externally applied (magnetic) field, which, in turn, can affect the overall rotation of the particles in the rubber, and therefore also the macroscopic response of the composite. This paper is concerned with the development of constitutive models for particle-reinforced elastomers, which are designed to account for externally applied torques on the internally distributed particles, in addition to the externally applied deformation on the boundary of the composite. For this purpose, we propose a new variational framework involving suitably prescribed eigenstresses on the particles. For simplicity, the framework is applied to an elastomer reinforced by aligned, rigid, cylindrical fibers of elliptical cross section, which can undergo finite rotations in the context of a finite-deformation, plane strain problem for the composite. In particular, expressions are derived for the average in-plane rotation of the fibers as a function of the torques that are applied on them, both under vanishing and prescribed strain on the boundary. The results of this work will make possible the development of improved constitutive models for magneto-active elastomers, and other types of smart composite materials that are susceptible to externally applied torques.

  10. Performance of reinforced polymer ablators exposed to a solid rocket motor exhaust. Technical report

    SciTech Connect

    Boyer, C.; Burgess, T.; Bowen, J.; Deloach, K.; Talmy, I.

    1992-10-01

    Summarized in this report is the effort by the Naval Surface Warfare Center Dahlgren Division (NSWCDD) and FMC Corporation (a launcher manufacturer) to identify new high performance ablators suitable for use on Navy guided missile launchers (GML) and ships' structures. The goal is to reduce ablator erosion by 25 to 50 percent compared to that of the existing ablators such as MXBE350 (rubbermodified phenolic containing glass fiber reinforcement). This reduction in erosion would significantly increase the number of new missiles with higher-thrust, longer burn rocket motors that can be launched prior to ablator refurbishment. In fact, there are a number of new Navy missiles being considered for development and introduction into existing GML: e.g., the Antisatellite Missile (ASM) and the Theater High-Altitude Area Defense (THAAD) Missile. The U.S. Navy experimentally evaluated the eight best fiber-reinforced, polymer composites from a possible field of 25 off-the-shelf ablators previously screened by FMC Corporation. They were tested by the Navy in highly aluminized solid rocket motor exhaust plumes to determine their ability to resist erosion and to insulate.... Ablator, Guided Missile Launchers, Erosion, Tactical missiles, Convective heating, Solid rocket motors, Aluminum oxide particles.

  11. Health monitoring of precast bridge deck panels reinforced with glass fiber reinforced polymer bars

    NASA Astrophysics Data System (ADS)

    Ries, James Mcdaniel

    The Beaver Creek Bridge on US highway 6 is the pilot project for Glass Fiber Reinforced Polymer (GFRP) bridge decks and posttensioned bridge decks in the state of Utah. The bridge was built in 2009, using accelerated bridge construction practices, including the use of precast prestressed girders, as well as precast decking. The westbound bridge decking was composed of 12 precast panels each measuring 41'-5" long, 6'-10" wide, and 9¼" thick, and weighing approximately 33 kips. At the time, these panels were the longest GFRP panels in the United States. The Utah Department of Transportation has decided to evaluate GFRP reinforcing bars as an alternative to steel rebar in this bridge deck. The hope is to increase the lifespan of bridge decks to match the service life of the entire bridge. Due to the nature of the GFRP bars, the panels were lifted at four points using straps instead of imbedded anchors. During the four-point lifting, the panels exhibited small deflections and strains; furthermore, no cracks larger than hairline cracks were found in the panels after lifting. The Beaver Creek Bridge deck is the first precast deck in the state of Utah to be posttensioned in the direction of traffic. Posttensioning bridge decks is expected to become the norm in the state of Utah. The posttensioning resulted in increased continuity between panels. In order to quantify the expected performance of the bridge during its service life, a truck load test was performed. The truck load test was comprised of a static and dynamic test. During the truck load test, the bridge experienced deflections in the panels which were 93% below design values. Girder deflections were also small. The use of GFRP bars has the potential to extend the life of bridge decks exposed to deicing salts from 45 years to 100 years, while only requiring an increased capital cost in the bridge of 8%. Furthermore, the use of GFRP bars in conjunction with accelerated building practices has the potential to

  12. Particle-Based Geometric and Mechanical Modelling of Woven Technical Textiles and Reinforcements for Composites

    NASA Astrophysics Data System (ADS)

    Samadi, Reza

    Technical textiles are increasingly being engineered and used in challenging applications, in areas such as safety, biomedical devices, architecture and others, where they must meet stringent demands including excellent and predictable load bearing capabilities. They also form the bases for one of the most widespread group of composite materials, fibre reinforced polymer-matrix composites (PMCs), which comprise materials made of stiff and strong fibres generally available in textile form and selected for their structural potential, combined with a polymer matrix that gives parts their shape. Manufacturing processes for PMCs and technical textiles, as well as parts and advanced textile structures must be engineered, ideally through simulation, and therefore diverse properties of the textiles, textile reinforcements and PMC materials must be available for predictive simulation. Knowing the detailed geometry of technical textiles is essential to predicting accurately the processing and performance properties of textiles and PMC parts. In turn, the geometry taken by a textile or a reinforcement textile is linked in an intricate manner to its constitutive behaviour. This thesis proposes, investigates and validates a general numerical tool for the integrated and comprehensive analysis of textile geometry and constitutive behaviour as required toward engineering applications featuring technical textiles and textile reinforcements. The tool shall be general with regards to the textiles modelled and the loading cases applied. Specifically, the work aims at fulfilling the following objectives: 1) developing and implementing dedicated simulation software for modelling textiles subjected to various load cases; 2) providing, through simulation, geometric descriptions for different textiles subjected to different load cases namely compaction, relaxation and shear; 3) predicting the constitutive behaviour of the textiles undergoing said load cases; 4) identifying parameters

  13. Polymer-Particle Pressure-Sensitive Paint with High Photostability

    PubMed Central

    Matsuda, Yu; Uchida, Kenta; Egami, Yasuhiro; Yamaguchi, Hiroki; Niimi, Tomohide

    2016-01-01

    We propose a novel fast-responding and paintable pressure-sensitive paint (PSP) based on polymer particles, i.e. polymer-particle (pp-)PSP. As a fast-responding PSP, polymer-ceramic (PC-)PSP is widely studied. Since PC-PSP generally consists of titanium (IV) oxide (TiO2) particles, a large reduction in the luminescent intensity will occur due to the photocatalytic action of TiO2. We propose the usage of polymer particles instead of TiO2 particles to prevent the reduction in the luminescent intensity. Here, we fabricate pp-PSP based on the polystyrene particle with a diameter of 1 μm, and investigate the pressure- and temperature-sensitives, the response time, and the photostability. The performances of pp-PSP are compared with those of PC-PSP, indicating the high photostability with the other characteristics comparable to PC-PSP. PMID:27092511

  14. Sedimentation of Colloidal Particles through a Polymer Solution

    NASA Astrophysics Data System (ADS)

    Tong, Penger; Ye, Xi; Ackerson, Bruce J.

    1997-03-01

    We report recent sedimentation measurements of colloidal particles through a polymer solution. The colloidal particles used were sterically stabilized CaCO3 suspended in decane and the polymer was hydrogenated polyisoprene. Our previous light and neutron scattering measurements have shown that the polymer chains do not adsorb onto the colloidal surfaces. Using a commercial ultracentrifuge, we measured the sedimentation rate of the colloidal particles, from which the microscopic viscosity experienced by the particles was obtained at different polymer concentration C_p. The experiment reveals that at low colloid concentration φ_c, the particles feel the single-chain viscosity when their size Rh is smaller than the correlation length ξ of the polymer solution. The particles experience the macroscopic viscosity of the polymer solution when Rh >> ξ. The transition for the particles to feel the macroscopic viscosity is well described by a switch function f_c(C_p)=exp[-(C_0/C_p)^α], which can be written as a function of R_h/ξ. It is found that f_c(C_p) is independent of the polymer molecular weight. As φc increases, the colloidal particles feel more and more depletion attraction and their settling velocity increases with increasing C_p.

  15. Design guidelines for steel-reinforced polymer concrete using resins based on recycled PET

    SciTech Connect

    Rebeiz, K.S.; Fowler, D.W.

    1996-10-01

    Very little research has been done on the structural behavior of steel-reinforced polymer concrete (PC). In all the previous studies, it was generally assumed that the structural behavior of reinforced PC is similar to the structural behavior of reinforced portland cement concrete because both are composite materials consisting of a binder and inorganic aggregates. However, the design equations developed for steel-reinforced portland cement concrete yield very conservative results when applied to reinforced PC. The objective of this paper is to recommend simple, yet effective design guidelines in shear and flexure for steel-reinforced PC. The recommended design procedures are mostly based on test results performed on PC beams using resins based on recycled poly(ethyleneterephthalate), PET, plastic waste (the PET waste is mainly recovered from used beverage bottles). Previous studies have shown that polyester resins based on recycled PET can produce very good quality PC at a potentially lower cost.

  16. Self-reinforced composites of bioabsorbable polymer and bioactive glass with different bioactive glass contents. Part II: In vitro degradation.

    PubMed

    Niemelä, Tiiu; Niiranen, Henna; Kellomäki, Minna

    2008-01-01

    The in vitro degradation behavior of self-reinforced bioactive glass-containing composites was investigated comparatively with plain self-reinforced matrix polymer. The materials used were spherical bioactive glass 13-93 particles, with a particle size distribution of 50-125 microm, as a filler material and bioabsorbable poly-L,DL-lactide 70/30 as a matrix material. The composites containing 0, 20, 30, 40 and 50 wt.% of bioactive glass were manufactured using twin-screw extruder followed by self-reinforcing. The samples studied were characterized determining the changes in mechanical properties, thermal properties, molecular weight, mass loss and water absorption in phosphate-buffered saline at 37 degrees C for up to 104 weeks. The results showed that the bioactive glass addition modified the degradation kinetics and material morphology of the matrix material. It was concluded that the optimal bioactive glass content depends on the applications of the composites. The results of this study could be used as a guideline when estimating the best filler content of other self-reinforced osteoconductive filler containing composites which are manufactured in a similar way.

  17. Evaluation of post-fire strength of concrete flexural members reinforced with glass fiber reinforced polymer (GFRP) bars

    NASA Astrophysics Data System (ADS)

    Ellis, Devon S.

    Owing to their corrosion resistance and superior strength to weight ratio, there has been, over the past two decades, increased interest in the use of fiber-reinforced polymer (FRP) reinforcing bars in reinforced concrete structural members. The mechanical behavior of FRP reinforcement differs from that of steel reinforcement. For example, FRP reinforcement exhibit a linear stress-strain behavior until the bar ruptures and the strength, stiffness and bond properties of FRP reinforcement are affected more adversely by elevated temperatures. All structures are subject to the risk of damage by fire and fires continue to be a significant cause of damage to structures. Many structures do not collapse after being exposed to fire. The safety of the structure for any future use is dependent on the ability to accurately estimate the post-fire load capacity of the structure. Assuming that the changes, due to fire exposure, in the mechanical behavior of the GFRP reinforcing bar and concrete, and the bond between the reinforcing bar and the concrete are understood, an analytical procedure for estimating the post-fire strength of GFRP reinforced concrete flexural elements can be developed. This thesis investigates the changes in: a) tensile properties and bond of GFRP bars; and b) the flexural behavior of GFRP reinforced concrete beams flexural after being exposed to elevated temperatures up to 400°C and cooled to ambient temperature. To this end, twelve tensile tests, twelve pullout bond tests and ten four-point beam tests were performed. The data from the tests were used to formulate analytical procedures for evaluating the post-fire strength of GFRP reinforced concrete beams. The procedure produced conservative results when compared with the experimental data. In general, the residual tensile strength and modulus of elasticity of GFRP bars decrease as the exposure temperature increases. The loss in properties is however, smaller than that observed by other researchers when

  18. Development of wind turbine towers using fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Ungkurapinan, Nibong

    With an ongoing trend in the wind turbine market, the size of wind turbines has been increasing continuously. Larger wind turbines imply an increase in size, weight, and loads acting on the wind turbine tower. This requires towers to be stronger and stiffer, and consequently leads to bigger tower diameters. Because of their size and weight, transportation and erection require heavy equipment that makes the use of such towers prohibitive in remote communities. To tackle this problem, a research program was initiated at the University of Manitoba to develop the technology required for the fabrication of wind turbine towers constructed of fiber reinforced polymers (FRP) for use in remote communities in Canada. The research program was carried out in stages. During the first stage, a feasibility study and an analytical investigation on various shapes of FRP towers were conducted. The concept of a multi-cellular composite tower was examined in great detail and the finite element results showed that such a tower could result in almost 45 percent reduction in weight. In the second stage of this research program, a robotic filament winding machine was designed and constructed in the Composites Laboratory of the University of Manitoba. It was used to fabricate the multi-cell tower specimens for testing. The third stage of the research program involved the experimental investigation, which was carried out in three phases. In the first phase, two single cell specimens were tested to failure under lateral loading. The specimens were 8 ft (2.44 m) long. The second phase involved the testing of two single cells loaded in compression. The third phase of the experimental investigation involved the testing of two eight-cell jointed tower specimens. The specimens were octagonal and tapered, with a diameter of 21.4 in (543 mm) at the base and 17.4 in (441 mm) at the top. They were 16 ft (4.88 m) in height and tested as cantilever under static loading. Local buckling was the dominant

  19. Particle-Directed Assembly of Semiflexible Polymer Chains

    NASA Astrophysics Data System (ADS)

    McGovern, Michael; Dorfman, Kevin; Morse, David

    We use molecular dynamics simulations to investigate several models of semiflexible polymers that exhibit an attractive interaction with spherical particles. The organization of semiflexible polymer chains through attractive interactions with spherical particles occurs in several important processes in nature, such as the winding of DNA around histones and counter-ion condensation of charged polymers. The process is also of technological interest in the packaging of DNA for delivery to cells. In this presentation, we will present data on both the phase behavior and the kinetics of self-assembly as a function of the stiffness of the polymers, the attractive potential between the monomers and the particles, and the relative size of the monomers and particles. Our simulations suggest a transition between globular and rod-like aggregates that changes from a gradual to a sudden transition depending on particle size, and that rod formation is a slow, nucleation dependent process.

  20. Low-Cost Nanocellulose-Reinforced High-Temperature Polymer Composites for Additive Manufacturing

    SciTech Connect

    Ozcan, Soydan; Tekinalp, Halil L.; Love, Lonnie J.; Kunc, Vlastimil; Nelson, Kim

    2016-07-13

    ORNL worked with American Process Inc. to demonstrate the potential use of bio-based BioPlus® lignin-coated cellulose nanofibrils (L-CNF) as a reinforcing agent in the development of polymer feedstock suitable for additive manufacturing. L-CNF-reinforced polylactic acid (PLA) testing coupons were prepared and up to 69% increase in tensile strength and 133% increase in elastic modulus were demonstrated.

  1. Carbon-Fiber Reinforced Plastic Passive Composite Damper by Use of Piezoelectric Polymer/Ceramic

    NASA Astrophysics Data System (ADS)

    Tanimoto, Toshio

    2002-11-01

    In this study, the passive damping of carbon-fiber reinforced plastic (CFRP) cantilever beams is examined using (1) interleaving of viscoelastic thermoplastic films, (2) piezoelectric polymer (PVDF) film interlayers and (3) surface-bonded piezoelectric ceramics. Introducing polyethylene-based film interlayers between composite plies resulted in a significant increase in the vibration loss factor. It is also shown that the vibration damping of CFRP laminates can be improved passively by means of PVDF film interlayers and resistively shunted, surface-bonded piezoelectric ceramic, PbZrO3-PbTiO3 (PZT) sheets. This paper also discusses the enhanced vibration damping of CFRP laminates with dispersed PZT particle interlayers. All these damping methods, interleaving of thermoplastic films, interlayers of PVDF films or dispersed PZT particles between composite plies, and resistively shunted, surface-bonded PZT sheets, can be jointly used to improve the damping of CFRP laminates/structures. The use of CFRP beams in combination with several damping concepts discussed here is promising for application in structures where light weight and improved vibration damping are desired.

  2. Neutron scattering as a probe of liquid crystal polymer-reinforced composite materials

    SciTech Connect

    Hjelm, R.P.; Douglas, E.P.; Benicewicz, B.C.; Langlois, D.A.

    1995-12-31

    This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This research project sought to obtain nanoscale and molecular level information on the mechanism of reinforcement in liquid crystal polymer (LCP)-reinforced composites, to realize molecular-reinforced LCP composites, and to test the validity of the concept of molecular reinforcement. Small-angle neutron scattering was used to study the structures in the ternary phase diagram of LCP with liquid crystal thermosets and solvent on length scales ranging from 1-100 nm. The goal of the scattering measurements is to understand the phase morphology and degree of segregation of the reinforcing and matrix components. This information helps elucidate the physics of self assembly in these systems. This work provides an experimental basis for a microengineering approach to composites of vastly improved properties.

  3. Influence of cyclic freeze-thaw on the parameters of the electric response to the pulse mechanical excitation of concrete reinforced by glass fibre reinforced polymer bars

    NASA Astrophysics Data System (ADS)

    Fursa, T. V.; Petrov, M. V.; Korzenok, I. N.

    2016-02-01

    Studies of the influence of cyclic freeze-thaw on the parameters of electric response from samples of concrete reinforced by glass fibre reinforced polymer (GFRP) bars were conducted. It is found that an increase in the number of freeze-thaw cycles increases the attenuation coefficient of energy of electric responses and moves the centre of gravity of spectrum to the low-frequency area. The results can be used to develop a method of nondestructive testing of reinforced concrete.

  4. Elastic behavior of CNT-reinforced polymer composites with discontinuities in CNT configurations

    NASA Astrophysics Data System (ADS)

    Kumar, Puneet; Srinivas, J., Dr.

    2017-02-01

    A numerical study has been made towards the effective elastic properties estimation of carbon nanotubes and carbon nanotube reinforced composite using finite element modelling (FEM). First, the elastic properties of Carbon nanotube (CNT) were predicted by considering that carbon atoms as nodes and carbon-carbon bonds as beam elements with linear and isotropic behaviour. It was observed that elastic properties of CNT predicted by FE analysis were in good agreement with previous data. Carbon atom vacancy defects were also included to investigate the adverse effect on elastic modulus of SWCNTs. To explore the macroscopic elastic behaviour of CNT in a finite densely packed polymer resin, a representative volume element (RVE) was selected instead of whole composite material in which the polymer resin was modelled as continuum material while CNT as an equivalent long fibre. FE results of RVE manifest that the CNT volume fraction and waviness have significant effect on elastic modulus of CNT reinforced polymer composite. An analytical formulation in terms of elastic properties and waviness ratio was also introduced in this study for waviness analysis. Moreover, the elastic properties of wavy CNT reinforced composite was compared with analytical outcomes. We extended present RVE model to incorporate the effects of CNTs agglomeration on the elastic behaviour of CNT-reinforced polymer composites. It was observed that anticipated elastic results not only depended on the volume fraction of CNTs, but also on the CNTs geometry, waviness and agglomeration.

  5. Preparation and characterization of glass fibers - polymers (epoxy) bars (GFRP) reinforced concrete for structural applications

    NASA Astrophysics Data System (ADS)

    Alkjk, Saeed; Jabra, Rafee; Alkhater, Salem

    2016-06-01

    The paper presents some of the results from a large experimental program undertaken at the Department of Civil Engineering of Damascus University. The project aims to study the ability to reinforce and strengthen the concrete by bars from Epoxy polymer reinforced with glass fibers (GFRP) and compared with reinforce concrete by steel bars in terms of mechanical properties. Five diameters of GFRP bars, and steel bars (4mm, 6mm, 8mm, 10mm, 12mm) tested on tensile strength tests. The test shown that GFRP bars need tensile strength more than steel bars. The concrete beams measuring (15cm wide × 15cm deep × and 70cm long) reinforced by GFRP with 0.5 vol.% ratio, then the concrete beams reinforced by steel with 0.89 vol.% ratio. The concrete beams tested on deflection test. The test shown that beams which reinforced by GFRP has higher deflection resistance, than beams which reinforced by steel. Which give more advantage to reinforced concrete by GFRP.

  6. Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

    NASA Technical Reports Server (NTRS)

    Cox, Sarah B.; Lui, Donovan; Gou, Jihua

    2014-01-01

    The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, which allows a shape to be formed prior to the cure, and is then pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Basalt fibers are used for the reinforcement in the composite system. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material.

  7. Quantum dot-containing polymer particles with thermosensitive fluorescence

    NASA Astrophysics Data System (ADS)

    Generalova, Alla N.; Oleinikov, Vladimir A.; Sukhanova, Alyona; Artemyev, Mikhail V.; Zubov, Vitaly P.; Nabiev, Igor

    2012-10-01

    In the past decades, increasing attention has been paid to the preparation of "smart" functionalized polymer particles reversibly responding to slight environmental changes, such as variations in temperature, pH, and ionic strength. The composite polymer particles consisting of a solid poly(acrolein-co-styrene) core and a poly(N-vinylcaprolactam) (PVCL) polymer shell doped with CdSe/ZnS semiconductor quantum dots (QDs) were prepared. The thermosensitive response of the composite particles was observed as a decrease in their hydrodynamic diameter upon heating above the lower critical solution temperature of the thermosensitive PVCL polymer used as a shell. Embedding QDs in the PVCL shell makes it possible to obtain particles whose fluorescence is sensitive to temperature changes. The temperature-dependent fluorescence of particles was determined by reversible variation of the distances between QDs in the PVCL shell as a result of temperature-driven conformational changes in this polymer. In addition, these particles can be used as carriers of biomolecule (e.g., bovine serum albumin, BSA) characterized by reversibly temperature-dependent fluorescence, which can serve as the basis for optical detection methods in bioassays, such as the measurement of local temperature in nanovolumes, biosensing, etc.

  8. Coating of uniform inorganic particles with polymers, I

    SciTech Connect

    Oyama, H.T.; Sprycha, R.; Xie, Yuming; Partch, R.E.; Matijevic, E. . Center for Advanced Materials Processing)

    1993-10-15

    Uniform spherical silica particles have been first coated with aluminum hydrous oxide and then with poly(divinylbenzene). To produce the outer shell, the inorganic cores were pretreated with a vinyl coupling agent, then divinylbenzene, and an initiator in hot mineral spirits. The thickness of the alumina or polymer layers could be controlled by adjusting the experimental parameters. The same procedure was used to coat irregularly shaped commercial alumina particles. The charge of the so prepared particles was determined by potentiometric titrations, which showed that the polymer coating was permeable to the reactants. Thus, the titration curves were determined by the properties of the cores.

  9. Evaluation of tensile strength of hybrid fiber (jute/gongura) reinforced hybrid polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Vijay, Kumar V.; Chandan, Byral R.; Prabaharan, G. P.; Raghav, Dasarath

    2015-07-01

    The polymer matrix composites attract many industrial applications due to its light weight, less cost and easy for manufacturing. In this paper, an attempt is made to prepare and study of the tensile strength of hybrid (two natural) fibers reinforced hybrid (Natural + Synthetic) polymer matrix composites. The samples were prepared with hybrid reinforcement consists of two different fibers such as jute and Gongura and hybrid polymer consists of polyester and cashew nut shell resins. The hybrid composites tensile strength is evaluated to study the influence of various fiber parameters on mechanical strength. The parameters considered here are the duration of fiber treatment, the concentration of alkali in fiber treatment and nature of fiber content in the composites.

  10. Polymer reinforcement using liquid-exfoliated boron nitride nanosheets

    NASA Astrophysics Data System (ADS)

    Khan, Umar; May, Peter; O'Neill, Arlene; Bell, Alan P.; Boussac, Elodie; Martin, Arnaud; Semple, James; Coleman, Jonathan N.

    2012-12-01

    We have exfoliated hexagonal boron nitride by ultrasonication in solutions of polyvinylalcohol in water. The resultant nanosheets are sterically stabilised by adsorbed polymer chains. Centrifugation-based size-selection was used to give dispersions of nanosheets with aspect ratio (length/thickness) of ~1400. Such dispersions can be used to produce polyvinylalcohol-BN composite films. Helium ion microscopy of fracture surfaces shows the nanosheets to be well dispersed and the composites to fail by pull-out. We find both modulus, Y, and strength, σB, of these composites to increase linearly with volume fraction, Vf, up to Vf ~ 0.1 vol% BN before falling off. The rates of increase are extremely high; dY/dVf = 670 GPa and dσB/dVf = 47 GPa. The former value matches theory based on continuum mechanics while the latter value is consistent with remarkably high polymer-filler interfacial strength. However, because the mechanical properties increase over such a narrow volume fraction range, the maximum values of both modulus and strength are only ~40% higher than the pure polymer. This phenomenon has also been observed for graphene-filled composites and represents a serious hurdle to the production of high performance polymer-nanosheet composites.We have exfoliated hexagonal boron nitride by ultrasonication in solutions of polyvinylalcohol in water. The resultant nanosheets are sterically stabilised by adsorbed polymer chains. Centrifugation-based size-selection was used to give dispersions of nanosheets with aspect ratio (length/thickness) of ~1400. Such dispersions can be used to produce polyvinylalcohol-BN composite films. Helium ion microscopy of fracture surfaces shows the nanosheets to be well dispersed and the composites to fail by pull-out. We find both modulus, Y, and strength, σB, of these composites to increase linearly with volume fraction, Vf, up to Vf ~ 0.1 vol% BN before falling off. The rates of increase are extremely high; dY/dVf = 670 GPa and d

  11. Electron beam irradiation in natural fibres reinforced polymers (NFRP)

    NASA Astrophysics Data System (ADS)

    Kechaou, B.; Salvia, M.; Fakhfakh, Z.; Juvé, D.; Boufi, S.; Kallel, A.; Tréheux, D.

    2008-11-01

    This study focuses on the electric charge motion in unsatured polyester and epoxy composites reinforced by natural fibres of Alfa type, treated by different coupling agents. The electric charging phenomenon is studied by scanning electron microscopy mirror effect (SEMME) coupled with the induced current method (ICM). Previously, using the same approach, glass fibre reinforced epoxy (GFRE) was studied to correlate mechanical [B. Kchaou, C. Turki, M. Salvia, Z. Fakhfakh, D. Tréheux, Composites Science and Technology 64 (2004) 1467], or tribological [B. Kchaou, C. Turki, M. Salvia, Z. Fakhfakh, D. Tréheux, Dielectric and friction behaviour of unidirectionalglass fibre reinforced epoxy (GFRE), Wear, 265 (2008) 763.] properties and dielectric properties. It was shown that the dielectric properties of the fibre-matrix interfaces play a significant role in the optimization of the composite. This result seems to be the same for natural fibre composites: the fibre-matrix interfaces allow a diffusion of the electric charges which can delocalize the polarization energy and consequently delay the damage of the composite. However, a non-suited sizing can lead to a new trapping of electric charges along these same interfaces with, as a consequence, a localization of the polarisation energy. The optimum composite is obtained for one sizing which helps, at the same time, to have a strong fibre-matrix adhesion and an easy flow of the electric charges along the interface.

  12. Assessment of mechanical behavior of PLA composites reinforced with Mg micro-particles through depth-sensing indentations analysis.

    PubMed

    Cifuentes, S C; Frutos, E; Benavente, R; Lorenzo, V; González-Carrasco, J L

    2017-01-01

    This work deals with the mechanical characterization by depth-sensing indentation (DSI) of PLLA and PLDA composites reinforced with micro-particles of Mg (up to 15wt%), which is a challenging task since the indented volume must provide information of the bulk composite, i.e. contain enough reinforcement particles. The composites were fabricated by combining hot extrusion and compression moulding. Physico-chemical characterization by TGA and DSC indicates that Mg anticipates the thermal degradation of the polymers but does not compromise their stability during processing. Especial emphasis is devoted to determine the effect of strain rate and Mg content on mechanical behavior, thus important information about the visco-elastic behavior and time-dependent response of the composites is obtained. Relevant for the intended application is that Mg addition increases the elastic modulus and hardness of the polymeric matrices and induces a higher resistance to flow. The elastic modulus obtained by DSI experiments shows good agreement with that obtained by uniaxial compression tests. The results indicate that DSI experiments are a reliable method to calculate the modulus of polymeric composites reinforced with micro-particles. Taking into consideration the mechanical properties results, PLA/Mg composite could be used as substitute for biodegradable monolithic polymeric implants already in the market for orthopedics (freeform meshes, mini plates, screws, pins, …), craniomaxillofacial, or spine.

  13. Polymer reinforcement using liquid-exfoliated boron nitride nanosheets.

    PubMed

    Khan, Umar; May, Peter; O'Neill, Arlene; Bell, Alan P; Boussac, Elodie; Martin, Arnaud; Semple, James; Coleman, Jonathan N

    2013-01-21

    We have exfoliated hexagonal boron nitride by ultrasonication in solutions of polyvinylalcohol in water. The resultant nanosheets are sterically stabilised by adsorbed polymer chains. Centrifugation-based size-selection was used to give dispersions of nanosheets with aspect ratio (length/thickness) of ∼1400. Such dispersions can be used to produce polyvinylalcohol-BN composite films. Helium ion microscopy of fracture surfaces shows the nanosheets to be well dispersed and the composites to fail by pull-out. We find both modulus, Y, and strength, σ(B), of these composites to increase linearly with volume fraction, V(f), up to V(f)∼ 0.1 vol% BN before falling off. The rates of increase are extremely high; dY/dV(f) = 670 GPa and dσ(B)/dV(f) = 47 GPa. The former value matches theory based on continuum mechanics while the latter value is consistent with remarkably high polymer-filler interfacial strength. However, because the mechanical properties increase over such a narrow volume fraction range, the maximum values of both modulus and strength are only ∼40% higher than the pure polymer. This phenomenon has also been observed for graphene-filled composites and represents a serious hurdle to the production of high performance polymer-nanosheet composites.

  14. Study of polymer particles suspensions for electrophoretic deposition.

    PubMed

    De Riccardis, M Federica; Martina, Virginia; Carbone, Daniela

    2013-02-14

    Recently a great interest has been expressed in electrophoretic deposition (EPD) of polymers, both as particles and as chains. It is generally accepted that also for polymer particles, the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory is valid, therefore, in principle, polymer suspensions suitable for EPD could be easily obtained by dispersing polymer particles in an aqueous or nonaqueous medium. Nevertheless, this work demonstrated that in order to obtain good quality deposits based on poly(ether ether ketone) (PEEK) and poly(tetrafluoroethylene) (PTFE), some additives have to be used. In the case of PEEK, a dispersant providing citrate anions was successfully used, whereas for PTFE a steric suspension stabilization was reached by adding polyvinylpyrrolidone (PVP). In such a way, codeposition of PEEK and PTFE was achieved. The efficiency of the EPD process was demonstrated by means of differential scanning calorimetry (DSC) measurements. A thermal program consisting of heat/cool/heat cycles at a low rate was used in order to evaluate the crystalline amount of each polymer in the deposits. In order to explain the obtained results, it needed to also consider the dimension and structural characteristic of the polymer particles.

  15. Assembling and properties of the polymer-particle nanostructured materials

    NASA Astrophysics Data System (ADS)

    Sheparovych, Roman

    Complementary properties of the soft and hard matter explain its common encounter in many natural and manmade applications. A combination of flexible organic macromolecules and hard mineral clusters results in new materials far advantageous than its constituents alone. In this work we study assembling of colloidal nanocrystals and polymers into complex nanostructures. Magnetism, surface wettability and adhesion comprise properties of interest for the obtained nanocomposites. Applying a magnetic field induces a reversible 1D ordering of the magnetically susceptible particles. This property was employed in the fabrication of the permanent chains of magnetite nanocrystals (d=15nm). In the assembling process the aligned particles were bound together using polyelectrolyte macromolecules. The basics of the binding process involved an electrostatic interaction between the positively charged polyelectrolyte and the negative surface of the particles (aqueous environment). Adsorption of the polymer molecules onto several adjacent particles in the aligned 1D aggregate results in the formation of the permanent particulate chains. Positive charges of the adsorbed polyelectrolyte molecules stabilize the dispersion of the obtained nanostructures in water. Magnetization measurements revealed that superparamagnetic nanoparticles, being assembled into 1D ordered structures, attain magnetic coercivity. This effect originates from the magnetostatic interaction between the neighboring magnetite nanocrystals. The preferable dipole alignment of the assembled nanoparticles is directed along the chain axis. Another system studied in this project includes polymer-particle responsive surface coatings. Tethered polymer chains and particles bearing different functionalities change surface properties upon restructuring of the composite layer. When the environment favors polymer swelling (good solvent), the polymer chains segregate to the surface and cover the particles. In the opposite case

  16. Fibre Reinforced Polymers (FRP) as Reinforcement for Concrete According to German Approvals

    NASA Astrophysics Data System (ADS)

    Alex, R.

    2015-11-01

    This article demonstrates the possibility of the application of joint principles to develop test programs for national approval or European Technical Assessments of FRP reinforcement for concrete. The limits of different systems are shown, which until now have been approved in Germany.

  17. Molecular simulation study of role of polymer-particle interactions in the strain-dependent viscoelasticity of elastomers (Payne effect)

    NASA Astrophysics Data System (ADS)

    Chen, Yulong; Li, Ziwei; Wen, Shipeng; Yang, Qingyuan; Zhang, Liqun; Zhong, Chongli; Liu, Li

    2014-09-01

    The strain-amplitude dependence of viscoelastic behavior of model crosslinked elastomers containing various concentrations of spherical nanoparticles (NPs) was studied by non-equilibrium molecular dynamics simulation. All the filler NPs were in monodispersed state and the interactions between these particles were purely repulsive. The polymer-particle interactions were attractive and their interaction energies were tuned in a broad range. Through the computational study, many important features of the behavior of particle-reinforced elastomers observed in experiments, including the Payne effect, were successfully reproduced. It was shown that the magnitude of the Payne effect was found to depend on the polymer-particle interaction and the filler loading. By examining the microstructures of the simulation systems and their evolution during oscillatory shear, four different mechanisms for the role of the polymer-particle interactions in the Payne effect were revealed that consist of the debonding of polymer chains from NP surfaces, the breakage of polymer-shell-bridged NP network, the rearrangement of the NPs in the network into different layers and the shear-induced yielding of the rigid polymer shell in-between neighboring NPs.

  18. Electroless nickel plating on polymer particles.

    PubMed

    Fujii, Syuji; Hamasaki, Hiroyuki; Takeoka, Hiroaki; Tsuruoka, Takaaki; Akamatsu, Kensuke; Nakamura, Yoshinobu

    2014-09-15

    Near-monodisperse, micrometer-sized polypyrrole-palladium (PPy-Pd) nanocomposite-coated polystyrene (PS) particles have been coated with Ni overlayers by electroless plating in aqueous media. Good control of the Ni loading was achieved for 1.0 μm diameter PPy-Pd nanocomposite-coated PS particles and particles of up to 20 μm in diameter could also be efficiently coated with the Ni. Laser diffraction particle size analysis studies of dilute aqueous suspensions indicated that an additional water-soluble colloidal stabilizer, poly(N-vinyl pyrrolidone), in the electroless plating reaction media was crucial to obtain colloidally stable Ni-coated composite particles. Elemental microanalysis indicated that the Ni loading could be controlled between 61 and 78 wt% for the 1.0 μm-sized particles. Scanning/transmission electron microscopy studies revealed that the particle surface had a flaked morphology after Ni coating. Spherical capsules were obtained after extraction of the PS component from the Ni-coated composite particles, which indicated that the shell became rigid after Ni coating. X-ray diffraction confirmed the production of elemental Ni and X-ray photoelectron spectroscopy studies indicated the existence of elemental Ni on the surface of the composite particles.

  19. Resorbable continuous-fibre reinforced polymers for osteosynthesis.

    PubMed

    Dauner, M; Planck, H; Caramaro, L; Missirlis, Y; Panagiotopoulos, E

    1998-03-01

    Four institutes from three countries in the European Union have collaborated under the BRITE-EURAM framework programme for the development of processing technologies for resorbable osteosynthesis devices. The devices should be continuous-fibre reinforced, and the technology should offer the possibility of orienting the fibres in the main trajectories. Poly-L-lactide and poly-L-DL-lactides have been synthesized for reinforcement fibres and matrix material, respectively. Melt-spun P-L-LA fibres of a strength of 800 MPa have been embedded in an amorphous P-L-DL-LA 70 : 30 matrix by compression moulding. Ethyleneoxide sterilized samples have been tested in vitro and in vivo. A satisfying bending modulus has been reached (6 GPa). Yet with 50% strength retention after ten weeks, fast degradation occurred that could be related to residual monomers. By this fast degradation 70% resorption after one year could be observed in the non-functional animal studies in rabbits. There was only a mild inflammatory reaction, which confirmed the good biocompatibility of the materials even during the resorption period. Further effort has to concentrate on the reduction of initial monomer content. The great advantage of the processing method to orient fibres in the device will be utilized in prototype samples, e.g. an osteosynthesis plate with fixation holes.

  20. Development of a 3D polymer reinforced calcium phosphate cement scaffold for cranial bone tissue engineering

    NASA Astrophysics Data System (ADS)

    Alge, Daniel L.

    The repair of critical-sized cranial bone defects represents an important clinical challenge. The limitations of autografts and alloplastic materials make a bone tissue engineering strategy desirable, but success depends on the development of an appropriate scaffold. Key scaffold properties include biocompatibility, osteoconductivity, sufficient strength to maintain its structure, and resorbability. Furthermore, amenability to rapid prototyping fabrication methods is desirable, as these approaches offer precise control over scaffold architecture and have the potential for customization. While calcium phosphate cements meet many of these criteria due to their composition and their injectability, which can be leveraged for scaffold fabrication via indirect casting, their mechanical properties are a major limitation. Thus, the overall goal of this work was to develop a 3D polymer reinforced calcium phosphate cement scaffold for use in cranial bone tissue engineering. Dicalcium phosphate dihydrate (DCPD) setting cements are of particular interest because of their excellent resorbability. We demonstrated for the first time that DCPD cement can be prepared from monocalcium phosphate monohydrate (MCPM)/hydroxyapatite (HA) mixtures. However, subsequent characterization revealed that MCPM/HA cements rapidly convert to HA during degradation, which is undesirable and led us to choose a more conventional formulation for scaffold fabrication. In addition, we developed a novel method for calcium phosphate cement reinforcement that is based on infiltrating a pre-set cement structure with a polymer, and then crosslinking the polymer in situ. Unlike prior methods of cement reinforcement, this method can be applied to the reinforcement of 3D scaffolds fabricated by indirect casting. Using our novel method, composites of poly(propylene fumarate) (PPF) reinforced DCPD were prepared and demonstrated as excellent candidate scaffold materials, as they had increased strength and ductility

  1. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermo-oxidative stability of PMR-15 polymer matrix composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers that were studied included graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber-sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  2. Smoothed dissipative particle dynamics model for polymer molecules in suspension

    NASA Astrophysics Data System (ADS)

    Litvinov, Sergey; Ellero, Marco; Hu, Xiangyu; Adams, Nikolaus A.

    2008-06-01

    We present a model for a polymer molecule in solution based on smoothed dissipative particle dynamics (SDPD) [Español and Revenga, Phys. Rev. E 67, 026705 (2003)]. This method is a thermodynamically consistent version of smoothed particle hydrodynamics able to discretize the Navier-Stokes equations and, at the same time, to incorporate thermal fluctuations according to the fluctuation-dissipation theorem. Within the framework of the method developed for mesoscopic multiphase flows by Hu and Adams [J. Comput. Phys. 213, 844 (2006)], we introduce additional finitely extendable nonlinear elastic interactions between particles that represent the beads of a polymer chain. In order to assess the accuracy of the technique, we analyze the static and dynamic conformational properties of the modeled polymer molecule in solution. Extensive tests of the method for the two-dimensional (2D) case are performed, showing good agreement with the analytical theory. Finally, the effect of confinement on the conformational properties of the polymer molecule is investigated by considering a 2D microchannel with gap H varying between 1 and 10μm , of the same order as the polymer gyration radius. Several SDPD simulations are performed for different chain lengths corresponding to N=20-100 beads, giving a universal behavior of the gyration radius RG and polymer stretch X as functions of the channel gap when normalized properly.

  3. Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles

    NASA Astrophysics Data System (ADS)

    Shin, Jaeoh; Cherstvy, Andrey G.; Kim, Won Kyu; Metzler, Ralf

    2015-11-01

    We study the dynamics of polymer chains in a bath of self-propelled particles (SPP) by extensive Langevin dynamics simulations in a two-dimensional model system. Specifically, we analyse the polymer looping properties versus the SPP activity and investigate how the presence of the active particles alters the chain conformational statistics. We find that SPPs tend to extend flexible polymer chains, while they rather compactify stiffer semiflexible polymers, in agreement with previous results. Here we show that higher activities of SPPs yield a higher effective temperature of the bath and thus facilitate the looping kinetics of a passive polymer chain. We explicitly compute the looping probability and looping time in a wide range of the model parameters. We also analyse the motion of a monomeric tracer particle and the polymer’s centre of mass in the presence of the active particles in terms of the time averaged mean squared displacement, revealing a giant diffusivity enhancement for the polymer chain via SPP pooling. Our results are applicable to rationalising the dimensions and looping kinetics of biopolymers at constantly fluctuating and often actively driven conditions inside biological cells or in suspensions of active colloidal particles or bacteria cells.

  4. Microscopic theory of polymer-mediated interactions between spherical particles

    SciTech Connect

    Chatterjee, A.P.; Schweizer, K.S.

    1998-12-01

    We develop an analytic integral equation theory for treating polymer-induced effects on the structure and thermodynamics of dilute suspensions of hard spheres. Results are presented for the potential of mean force, free energy of insertion per particle into a polymer solution, and the second virial coefficient between spheres. The theory makes predictions for all size ratios between the spheres and the polymer coil dimension. Based on the Percus{endash}Yevick (PY) closure, the attractive polymer-induced depletion interaction is predicted to be too weak under athermal conditions to induce a negative value for the second virial coefficient, B{sub 2}{sup cc}, between spheres in the colloidal limit when the spheres are much larger than the coil size. A nonmonotonic dependence of the second virial coefficient on polymer concentration occurs for small enough particles, with the largest polymer-mediated attractions and most negative B{sub 2}{sup cc} occurring near the dilute{endash}semidilute crossover concentration. Predictions for the polymer-mediated force between spheres are compared to the results of computer simulations and scaling theory. {copyright} {ital 1998 American Institute of Physics.}

  5. Silicone-containing aqueous polymer dispersions with hybrid particle structure.

    PubMed

    Kozakiewicz, Janusz; Ofat, Izabela; Trzaskowska, Joanna

    2015-09-01

    In this paper the synthesis, characterization and application of silicone-containing aqueous polymer dispersions (APD) with hybrid particle structure are reviewed based on available literature data. Advantages of synthesis of dispersions with hybrid particle structure over blending of individual dispersions are pointed out. Three main processes leading to silicone-containing hybrid APD are identified and described in detail: (1) emulsion polymerization of organic unsaturated monomers in aqueous dispersions of silicone polymers or copolymers, (2) emulsion copolymerization of unsaturated organic monomers with alkoxysilanes or polysiloxanes with unsaturated functionality and (3) emulsion polymerization of alkoxysilanes (in particular with unsaturated functionality) and/or cyclic siloxanes in organic polymer dispersions. The effect of various factors on the properties of such hybrid APD and films as well as on hybrid particles composition and morphology is presented. It is shown that core-shell morphology where silicones constitute either the core or the shell is predominant in hybrid particles. Main applications of silicone-containing hybrid APD and related hybrid particles are reviewed including (1) coatings which show specific surface properties such as enhanced water repellency or antisoiling or antigraffiti properties due to migration of silicone to the surface, and (2) impact modifiers for thermoplastics and thermosets. Other processes in which silicone-containing particles with hybrid structure can be obtained (miniemulsion polymerization, polymerization in non-aqueous media, hybridization of organic polymer and polysiloxane, emulsion polymerization of silicone monomers in silicone polymer dispersions and physical methods) are also discussed. Prospects for further developments in the area of silicone-containing hybrid APD and related hybrid particles are presented.

  6. Magnetic particle dispersion in polymer solution

    NASA Astrophysics Data System (ADS)

    Jeon, Kwang Seoung

    Magnetic particle dispersions were prepared in order to observe the effect of particle surface properties, concentration and functional group of binder, milling time, and solvent on dispersion properties. Rheology and transverse susceptibility measurements were used to characterize the dispersion quality of the magnetic paints macroscopically and microscopically, respectively. In this study, by applying the acid-base concept, methods to optimize magnetic dispersions were established. Initially, interaction between acid-base sites on particles and binder was investigated by poisoning the sites with chemicals, then quantifying each type of adsorption (hydrogen and chemical adsorption) using thermogravimetric analysis. With this fundamental information, effects of typical dispersion parameters were investigated. The acid base interaction between binder solution and particles was related to the magnetic and rheological properties of magnetic inks. The results have significant implications for high density particulate media where dispersion will become increasingly important.

  7. Mussel-inspired catecholamine polymers as new sizing agents for fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Lee, Wonoh; Lee, Jea Uk; Byun, Joon-Hyung

    2015-04-01

    Mussel-inspired catecholamine polymers (polydopamine and polynorepinephrine) were coated on the surface of carbon and glass fibers in order to increase the interfacial shear strength between fibers and polymer matrix, and consequently the interlaminar shear strength of fiber-reinforced composites. By utilizing adhesive characteristic of the catecholamine polymer, fiber-reinforced composites can become mechanically stronger than conventional composites. Since the catecholamine polymer is easily constructed on the surface by the simultaneous polymerization of its monomer under a weak basic circumstance, it can be readily coated on micro-fibers by a simple dipping process without any complex chemical treatments. Also, catecholamines can increase the surface free energy of micro-fibers and therefore, can give better wettability to epoxy resin. Therefore, catecholamine polymers can be used as versatile and effective surface modifiers for both carbon and glass fibers. Here, catecholamine-coated carbon and glass fibers exhibited higher interfacial shear strength (37 and 27% increases, respectively) and their plain woven composites showed improved interlaminar shear strength (13 and 9% increases, respectively) compared to non-coated fibers and composites.

  8. Bisphenyl-Polymer/Carbon-Fiber-Reinforced Composite Compared to Titanium Alloy Bone Implant

    PubMed Central

    Petersen, Richard C.

    2014-01-01

    Aerospace/aeronautical thermoset bisphenyl-polymer/carbon-fiber-reinforced composites are considered as new advanced materials to replace metal bone implants. In addition to well-recognized nonpolar chemistry with related bisphenol-polymer estrogenic factors, carbon-fiber-reinforced composites can offer densities and electrical conductivity/resistivity properties close to bone with strengths much higher than metals on a per-weight basis. In vivo bone-marrow tests with Sprague-Dawley rats revealed far-reaching significant osseoconductivity increases from bisphenyl-polymer/carbon-fiber composites when compared to state-of-the-art titanium-6-4 alloy controls. Midtibial percent bone area measured from the implant surface increased when comparing the titanium alloy to the polymer composite from 10.5% to 41.6% at 0.8 mm, P < 10−4, and 19.3% to 77.7% at 0.1 mm, P < 10−8. Carbon-fiber fragments planned to occur in the test designs, instead of producing an inflammation, stimulated bone formation and increased bone integration to the implant. In addition, low-thermal polymer processing allows incorporation of minerals and pharmaceuticals for future major tissue-engineering potential. PMID:25553057

  9. Preparation of magnetic polymer particles with nanoparticles of Fe(0).

    PubMed

    Buendía, S; Cabañas, G; Alvarez-Lucio, G; Montiel-Sánchez, H; Navarro-Clemente, M E; Corea, M

    2011-02-01

    Iron nanoparticles (Fe(0)), were encapsulated into polymethyl methacrylate (PMMA), by means of emulsion polymerization techniques in a semicontinuous process. The final average diameter of the composite particle was calculated until three times of average particle of iron particles and were stabilized with a non-ionic surfactant. They were then characterized by scanning electron microscopy and dynamic light scattering. Their magnetic properties were determined by parallel field vibrating-sample magnetometry method. The results indicated that the magnetic properties are a function of polymer concentration in the nanocomposite particle.

  10. Tuning particle biodegradation through polymer-peptide blend composition.

    PubMed

    Gunawan, Sylvia T; Kempe, Kristian; Such, Georgina K; Cui, Jiwei; Liang, Kang; Richardson, Joseph J; Johnston, Angus P R; Caruso, Frank

    2014-12-08

    We report the preparation of polymer-peptide blend replica particles via the mesoporous silica (MS) templated assembly of poly(ethylene glycol)-block-poly(2-diisopropylaminoethyl methacrylate-co-2-(2-(2-(prop-2-ynyloxy)ethoxy)ethoxy)ethyl methacrylate) (PEG45-b-P(DPA55-co-PgTEGMA4)) and poly(l-histidine) (PHis). PEG45-b-P(DPA55-co-PgTEGMA4) was synthesized by atom transfer radical polymerization (ATRP), and was coinfiltrated with PHis into poly(methacrylic acid) (PMA)-coated MS particles assembled from different peptide-to-polymer ratios (1:1, 1:5, 1:10, or 1:15). Subsequent removal of the sacrificial templates and PMA resulted in monodisperse, colloidally stable, noncovalently cross-linked polymer-peptide blend replica particles that were stabilized by a combination of hydrophobic interactions between the PDPA and the PHis, hydrogen bonding between the PEG and PHis backbone, and π-π stacking of the imidazole rings of PHis side chains at physiological pH (pH ∼ 7.4). The synergistic charge-switchable properties of PDPA and PHis, and the enzymatic degradability of PHis, make these particles responsive to pH and enzymes. In vitro studies, in simulated endosomal conditions and inside cells, demonstrated that particle degradation kinetics could be engineered (from 2 to 8 h inside dendritic cells) based on simple adjustment of the peptide-to-polymer ratio used.

  11. Role of Polymer Segment-Particle Surface Interactions in Controlling Nanoparticle Dispersions in Concentrated Polymer Solutions

    SciTech Connect

    Kim, So Youn; Zukoski, Charles F.

    2014-09-24

    The microstructure of particles suspended in concentrated polymer solutions is examined with small-angle X-ray scattering and small-angle neutron scattering. Of interest are changes to long wavelength particle density fluctuations in ternary mixtures of silica nanoparticles suspended in concentrated solutions of poly(ethylene glycol). The results are understood in terms of application of the pseudo-two-component polymer reference interaction site model (PRISM) theory modified to account for solvent addition via effective contact strength of interfacial attraction, εpc, in an implicit manner. The combined experimental-theoretical study emphasizes the complex interactions between solvent, polymer, and particle surface that control particle miscibility but also demonstrate that these factors can all be understood in terms of variations of εpc.

  12. Environmental Durability of Materials and Bonded Joints Involving Fiber Reinforced Polymers and Concerte

    NASA Astrophysics Data System (ADS)

    Gavari, Mahdi Mansouri; rad, A. Yazdi; Gavari, Mohsen Mansouri

    2008-08-01

    This paper describes the research work undertaken to evaluate the performance of materials and bonded joints involving Fibre Reinforced Polymers (FRPs) and concrete. Experimental variables ncluded polymer composite materials, test methods and environmental test conditions. Tensile and flexural tests were carried out to determine short term and long term environmental durability of composite materials. Single lap shear, a modified wedge cleavage and pull-off adhesion tests were used to study the performance of bonded joints. It is shown the tensile strength of composite materials can be affected after exposure to hot/humid conditions. The performance of stressed single lap joints was also affected by hot/humid conditions.

  13. Thermo-mechanical characterization of siliconized E-glass fiber/hematite particles reinforced epoxy resin hybrid composite

    NASA Astrophysics Data System (ADS)

    V. R., Arun prakash; Rajadurai, A.

    2016-10-01

    In this present work hybrid polymer (epoxy) matrix composite has been strengthened with surface modified E-glass fiber and iron(III) oxide particles with varying size. The particle sizes of 200 nm and <100 nm has been prepared by high energy ball milling and sol-gel methods respectively. To enhance better dispersion of particles and improve adhesion of fibers and fillers with epoxy matrix surface modification process has been done on both fiber and filler by an amino functional silane 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized iron(III) oxide particles were characterized by XRD and FTIR spectroscopy analysis. Fixed quantity of surface treated 15 vol% E-glass fiber was laid along with 0.5 and 1.0 vol% of iron(III) oxide particles into the matrix to fabricate hybrid composites. The composites were cured by an aliphatic hardener Triethylenetetramine (TETA). Effectiveness of surface modified particles and fibers addition into the resin matrix were revealed by mechanical testing like tensile testing, flexural testing, impact testing, inter laminar shear strength and hardness. Thermal behavior of composites was evaluated by TGA, DSC and thermal conductivity (Lee's disc). The scanning electron microscopy was employed to found shape and size of iron(III) oxide particles adhesion quality of fiber with epoxy matrix. Good dispersion of fillers in matrix was achieved with surface modifier APTMS. Tensile, flexural, impact and inter laminar shear strength of composites was improved by reinforcing surface modified fiber and filler. Thermal stability of epoxy resin was improved when surface modified fiber was reinforced along with hard hematite particles. Thermal conductivity of epoxy increased with increase of hematite content in epoxy matrix.

  14. Ti particle-reinforced surface layers in Al: Effect of particle size on microstructure, hardness and wear

    SciTech Connect

    Mordyuk, B.N.; Silberschmidt, V.V.; Prokopenko, G.I.; Nesterenko, Yu.V.; Iefimov, M.O.

    2010-11-15

    Two types of Ti particles are used in an ultrasonic impact peening (UIP) process to modify sub-surface layers of cp aluminium atomized, with an average size of approx. 20 {mu}m and milled (0.3-0.5 {mu}m). They are introduced into a zone of severe plastic deformation induced by UIP. The effect of Ti particles of different sizes on microstructure, phase composition, microhardness and wear resistance of sub-surface composite layers in aluminium is studied in this paper. The formed layers of a composite reinforced with smaller particles have a highly misoriented fine-grain microstructure of its matrix with a mean grain size of 200-400 nm, while reinforcement with larger particles results in relatively large Al grains (1-2 {mu}m). XRD, SEM, EDX and TEM studies confirm significantly higher particle/matrix bonding in the former case due to formation of a Ti{sub 3}Al interlayer around Ti particles with rough surface caused by milling. Different microstructures determine hardness and wear resistance of reinforced aluminium layers: while higher magnitudes of microhardness are observed for both composites (when compared with those of annealed and UIP-treated aluminium), the wear resistance is improved only in the case of reinforcement with small particles.

  15. Behavior of Concrete Beams with Peel-Plied Aramid-Fiber-Reinforced Polymer Plates

    NASA Astrophysics Data System (ADS)

    Hong, Sungnam; Park, Sun-Kyu

    2016-03-01

    The effect of fiber-reinforced polymer (FRP) plates, to which a peel-ply was fastened to increase their bonding area, on the behavior of strengthened concrete beams was investigated. A total of six concrete beams were tested. For the FRP plates, aramid-fiber-reinforced polymer (AFRP) ones were used. The test variables included their surface treatment (smooth and deformed), the depth of removal of concrete cover (0 and 10 mm), and the number of the plates. Each beam was tested in four-point bending under displacement control up to failure. Based on the experimental results obtained, the effect of the peel-plied AFRP plates on the flexural behavior of the concrete beams was evaluated.

  16. Experimental research on continuous basalt fiber and basalt-fibers-reinforced polymers

    NASA Astrophysics Data System (ADS)

    Zhang, Xueyi; Zou, Guangping; Shen, Zhiqiang

    2008-11-01

    The interest for continuous basalt fibers and reinforced polymers has recently grown because of its low price and rich natural resource. Basalt fiber was one type of high performance inorganic fibers which were made from natural basalt by the method of melt extraction. This paper discusses basic mechanical properties of basalt fiber. The other work in this paper was to conduct tensile testing of continuous basalt fiber-reinforced polymer rod. Tensile strength and stress-strain curve were obtained in this testing. The strength of rod was fairly equal to rod of E-glass fibers and weaker than rod of carbon fibers. Surface of crack of rod was studied. An investigation of fracture mechanism between matrix and fiber was analyzed by SEM (Scanning electron microscopy) method. A poor adhesion between the matrix and fibers was also shown for composites analyzing SEM photos. The promising tensile properties of the presented basalt fibers composites have shown their great potential as alternative classical composites.

  17. Selective recognition of neodymium (III) using ion imprinted polymer particles.

    PubMed

    Krishna, Paramesamangalam Gopi; Gladis, Joseph Mary; Rao, Talasila Prasada; Naidu, Gurijala Ramakrishna

    2005-01-01

    Neodymium (III) ion-imprinted polymer (IIP) materials were prepared by the copolymerization of neodymium (III)-5,7-dichloroquinoline-8-ol-4-vinylpyridine ternary complex with styrene(monomer), divinyl benzene (crosslinking monomer) in the presence of 2,2'-azobisisobutyronitrile (initiator). The synthesis was carried out in 2-methoxy ethanol medium (porogen) and the resultant material was filtered, washed, dried and powdered to form unleached IIP particles. The imprint ion was removed by stirring the above particles with 50% (v/v) HCl for 6 h to obtain leached IIP particles with cavities in the polymer particles. Control polymer (CP) particles were similarly prepared without imprint ion, i.e. neodymium (III). CP, unleached and leached IIP particles were characterized by TLC, IR, microanalysis, XRD and UV-visible spectrophotometric studies. The preconcentration of 5-150 microg of neodymium (III) ions present in 500 ml of solution was possible with as little as 40 mg of neodymium (III) IIP particles in the pH range 7.5-8.0 with a detection limit of 50 ng/l. Five replicate determinations of 25 microg of neodymium (III) present in 500 ml of solution gave a mean absorbance of 0.120 with a relative standard deviation of 2.65%. The imprinting effect of IIP particles was noticed in all preconcentration and selectivity studies when compared with CP particles. Furthermore, the selectivity coefficients of neodymium (III) IIP particles were much higher compared with the reported separation factors for the best liquid-liquid extractants, viz. di-2-ethylhexyl phosphoric acid and 2-ethylhexyl-ethylhexyl phosphonate. Kinetic and isotherm studies during rebinding of neodymium (III) onto IIP particles were also carried out.

  18. A Fully Contained Resin Infusion Process for Fiber-Reinforced Polymer Composite Fabrication and Repair

    DTIC Science & Technology

    2013-01-01

    Assisted Resin Transfer Molding ( VARTM ) process is applicable for fiber-reinforced polymer (FRP) composite fabrication and repair. However, VARTM in...scenario is a fully enclosed VARTM system that limits the need for laboratory or manufacturing equipment. The Bladder-Bag VARTM (BBVARTM) technique...composite fabrication, VARTM , composite repair, in-field repair 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER

  19. The reflectivity of carbon fiber reinforced polymer short circuit illuminated by guided microwaves

    NASA Astrophysics Data System (ADS)

    Bojovschi, A.; Scott, J.; Ghorbani, K.

    2013-09-01

    An investigation of the interaction between guided electromagnetic waves and carbon fibre reinforced polymer waveguide short circuits is presented. To determine the electromagnetic response of the composite waveguide short circuit, its anisotropic characteristics are considered. The reflection coefficients of the short circuit, at the reference plane, are about 0.98 over the whole 8 GHz to 12 GHz band. The results indicate the viability of carbon fiber based short circuits for lightweight waveguides.

  20. Interlaminar damage of carbon fiber reinforced polymer composite laminate under continuous wave laser irradiation

    NASA Astrophysics Data System (ADS)

    Liu, Yan-Chi; Wu, Chen-Wu; Huang, Yi-Hui; Song, Hong-Wei; Huang, Chen-Guang

    2017-01-01

    The interlaminar damages were investigated on the carbon fiber reinforced polymer (CFRP) composite laminate under laser irradiation. Firstly, the laminated T700/BA9916 composites were exposed to continuous wave laser irradiation. Then, the interface cracking patterns of such composite laminates were examined by optical microscopy and scanning electron microscopy. Finally, the Finite Element Analysis (FEA) was performed to compute the interface stress of the laminates under laser irradiation. And the effects of the laser parameters on the interlaminar damage were discussed.

  1. Investigation of Creep Rupture Phenomenon in Glass Fibre Reinforced Polymer (GFRP) Stirrups

    NASA Astrophysics Data System (ADS)

    Johal, Kanwardeep Singh

    Glass Fibre-Reinforced Polymer (GFRP) bars offer a feasible alternative to typical steel reinforcement in concrete structures where there are concerns of corrosion or magnetic interference. In order to design safe structures for a service life of 50 to 100 years, the long-term material properties of GFRP must be understood. Thirty GFRP stirrups of three types were tested under sustained loading to investigate creep rupture and modulus degradation behaviour. The time to failure under varying sustained loads was used to extrapolate the safe design load for typical service lives. It was found that shear critical beams with shear reinforcement designed in accordance with CSA-S806 and ACI-440 provisions may be at risk of premature failure under sustained design loads. Analysis was based on finite element modelling and previously tested beams. Additionally, no moduli degradation was observed in this study. A cumulative weakening model was developed to potentially take into account fatigue loading.

  2. Mechanical characterization and structural analysis of recycled fiber-reinforced-polymer resin-transfer-molded beams

    NASA Astrophysics Data System (ADS)

    Tan, Eugene Wie Loon

    1999-09-01

    The present investigation was focussed on the mechanical characterization and structural analysis of resin-transfer-molded beams containing recycled fiber-reinforced polymers. The beams were structurally reinforced with continuous unidirectional glass fibers. The reinforcing filler materials consisted entirely of recycled fiber-reinforced polymer wastes (trim and overspray). The principal resin was a 100-percent dicyclo-pentadiene unsaturated polyester specially formulated with very low viscosity for resin transfer molding. Variations of the resin transfer molding technique were employed to produce specimens for material characterization. The basic materials that constituted the structural beams, continuous-glass-fiber-reinforced, recycled-trim-filled and recycled-overspray-filled unsaturated polyesters, were fully characterized in axial and transverse compression and tension, and inplane and interlaminar shear, to ascertain their strengths, ultimate strains, elastic moduli and Poisson's ratios. Experimentally determined mechanical properties of the recycled-trim-filled and recycled-overspray-filled materials from the present investigation were superior to those of unsaturated polyester polymer concretes and Portland cement concretes. Mechanical testing and finite element analyses of flexure (1 x 1 x 20 in) and beam (2 x 4 x 40 in) specimens were conducted. These structurally-reinforced specimens were tested and analyzed in four-point, third-point flexure to determine their ultimate loads, maximum fiber stresses and mid-span deflections. The experimentally determined load capacities of these specimens were compared to those of equivalent steel-reinforced Portland cement concrete beams computed using reinforced concrete theory. Mechanics of materials beam theory was utilized to predict the ultimate loads and mid-span deflections of the flexure and beam specimens. However, these predictions proved to be severely inadequate. Finite element (fracture propagation

  3. Physicochemical Properties of 'Particle Brush'-Based Materials: Using Polymer Graft Modification to Tailor Particle Interactions

    NASA Astrophysics Data System (ADS)

    Schmitt, Michael D.

    The advent of surface-initiated controlled radical polymerization techniques has allowed a new class of hybrid polymer-grafted nanoparticles, known as eparticle brushes,f to be realized. By grafting polymers from the surface, interactions between particles can be tuned using the precise control over graft architecture (i.e. chain length, dispersity, particle size, and grafting density) afforded by controlled radical polymerizations. Previously, a transition from particle-like to polymer-like interactions in small particles with increasing graft length has been observed. In the limit of long graft lengths, the polymer chains impart new interactions between particles, such as entanglements. These results outline a rich, but largely unexplored parameter space. The present thesis further elucidates the extent to which polymer graft modification facilitates new interaction types between particles and the dependence of those interactions on chain conformation. Specifically, the mechanical properties, processability, phase separation, and vibrational modes of particle brushes are examined. A dependence of the mechanical properties of particle brush assemblies on particle size is accurately captured by accounting for differences in chain conformation between particles of different sizes using a simple scaling model. Further tailoring of mechanical characteristics in weak particle brush assemblies can be achieved using appropriate homopolymer additives to form two-component systems. Improved mechanical properties are accompanied by a significant enhancement in particle processability that allows application of previously unusable processing methods. Considering more complex systems, mesoscale phase separation of nanoparticles is demonstrated for the first time by blending of particle brushes with different graft polymers. Polymer graft modification is seen to not only strengthen and introduce new interactions, but also tune particle properties. Vibrational modes of

  4. Reinforcing polymer composites with epoxide-grafted carbon nanotubes.

    PubMed

    Wang, Shiren; Liang, Richard; Wang, Ben; Zhang, Chuck

    2008-02-27

    An in situ functionalization method was used to graft epoxide onto single-walled carbon nanotubes (SWNTs) and improve the integration of SWNTs into epoxy polymer. The characterization results of Raman, FT-IR and transmission electron microscopy (TEM) validated the successful functionalization with epoxide. These functionalized SWNTs were used to fabricate nanocomposites, resulting in uniform dispersion and strong interfacial bonding. The mechanical test demonstrated that, with only 1 wt% loading of functionalized SWNTs, the tensile strength of nanocomposites was improved by 40%, and Young's modulus by 60%.These results suggested that efficient load transfer has been achieved through epoxide-grafting. This investigation provided an efficient way to improve the interfacial bonding of multifunctional high-performance nanocomposites for lightweight structure material applications.

  5. Bioinspired design and assembly of platelet reinforced polymer films.

    PubMed

    Bonderer, Lorenz J; Studart, André R; Gauckler, Ludwig J

    2008-02-22

    Although strong and stiff human-made composites have long been developed, the microstructure of today's most advanced composites has yet to achieve the order and sophisticated hierarchy of hybrid materials built up by living organisms in nature. Clay-based nanocomposites with layered structure can reach notable stiffness and strength, but these properties are usually not accompanied by the ductility and flaw tolerance found in the structures generated by natural hybrid materials. By using principles found in natural composites, we showed that layered hybrid films combining high tensile strength and ductile behavior can be obtained through the bottom-up colloidal assembly of strong submicrometer-thick ceramic platelets within a ductile polymer matrix.

  6. Effect of fiber reinforcements on thermo-oxidative stability and mechanical properties of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1991-01-01

    A number of studies have investigated the thermo-oxidative behavior of polymer matrix composites. Two significant observations have been made from these research efforts: (1) fiber reinforcement has a significant effect on composite thermal stability; and (2) geometric effects must be considered when evaluating thermal aging data. A compilation of some results from these studies is presented, and this information shows the influence of the reinforcement fibers on the oxidative degradation of various polymer matrix composites. The polyimide PMR-15 was the matrix material that was used in these studies. The control composite material was reinforced with Celion 6000 graphite fiber. T-40R graphite fibers, along with some very stable ceramic fibers were selected as reinforcing fibers because of their high thermal stability. The ceramic fibers were Nicalon (silicon carbide) and Nextel 312 (alumina-silica-boron oxide). The mechanical properties of the two graphite fiber composites were significantly different, probably owing to variations in interfacial bonding between the fibers and the polyimide matrix. The Celion 6000/PMR-15 bond is very tight but the T-40/PMR-15 bond is less tight. Three oxidation mechanisms were observed: (1) the preferential oxidation of the Celion 6000 fiber ends at cut surfaces, leaving a surface of matrix material with holes where the fiber ends were originally situated; (2) preferential oxidation of the composite matrix; and (3) interfacial degradation by oxidation. The latter two mechanisms were also observed on fiber end cut surfaces. The fiber and interface attacks appeared to initiate interfiber cracking along these surfaces.

  7. Manufacturing Energy Intensity and Opportunity Analysis for Fiber-Reinforced Polymer Composites and Other Lightweight Materials

    SciTech Connect

    Liddell, Heather; Brueske, Sabine; Carpenter, Alberta; Cresko, Joseph

    2016-09-22

    With their high strength-to-weight ratios, fiber-reinforced polymer (FRP) composites are important materials for lightweighting in structural applications; however, manufacturing challenges such as low process throughput and poor quality control can lead to high costs and variable performance, limiting their use in commercial applications. One of the most significant challenges for advanced composite materials is their high manufacturing energy intensity. This study explored the energy intensities of two lightweight FRP composite materials (glass- and carbon-fiber-reinforced polymers), with three lightweight metals (aluminum, magnesium, and titanium) and structural steel (as a reference material) included for comparison. Energy consumption for current typical and state-of-the-art manufacturing processes were estimated for each material, deconstructing manufacturing process energy use by sub-process and manufacturing pathway in order to better understand the most energy intensive steps. Energy saving opportunities were identified and quantified for each production step based on a review of applied R&D technologies currently under development in order to estimate the practical minimum energy intensity. Results demonstrate that while carbon fiber reinforced polymer (CFRP) composites have the highest current manufacturing energy intensity of all materials considered, the large differences between current typical and state-of-the-art energy intensity levels (the 'current opportunity') and between state-of-the-art and practical minimum energy intensity levels (the 'R&D opportunity') suggest that large-scale energy savings are within reach.

  8. Sensing uniaxial tensile damage in fiber-reinforced polymer composites using electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Lestari, Wahyu; Pinto, Brian; La Saponara, Valeria; Yasui, Jennifer; Loh, Kenneth J.

    2016-08-01

    This work describes the application of electrical resistance tomography (ERT) in sensing damage in fiber-reinforced polymer composites under uniaxial quasi-static tension. Damage is manifested as numerous matrix cracks which are distributed across the composite volume and which eventually coalesce into intralayer cracks. Hence, tensile damage is distributed throughout the volume, and could be more significant outside the sensor area. In this work, tensile damage of unidirectional glass fiber-reinforced polymer composites (GFRP) and plain weave carbon fiber-reinforced polymer composites (CFRP) is sensed by utilizing a spray-on nanocomposite sensor, which is then instrumented by boundary electrodes. The resistance change distribution within the sensor area is reconstructed from a series of boundary voltage measurements, and ERT is implemented using a maximum a posteriori approach and assumptions on the type of noise in the reconstruction. Results show that this technique has promise in tracking uniaxial damage in composites. The different fiber architectures (unidirectional GFRP, plain weave CFRP) give distinct features in the ERT, which are consistent with the physical behavior of the tested samples.

  9. Rotational diffusion in polymer nanocomposites as probed by anisotropic particles

    NASA Astrophysics Data System (ADS)

    Clarke, Laura

    2014-03-01

    Metal nanoparticles strongly absorb specific wavelengths of light with no (or only a very weak) radiative relaxation by which to release this energy. As a result, the absorbed energy is efficiently converted to local heat (a photothermal effect). With an effective cross-section of up to 10 times its physical size, each particle acts as a ``super-sized'' absorber even when embedded within a transparent material environment such as a polymer, resulting in dramatic heating originating at the particles. Thus, with spatially-uniform illumination, one can metaphorically reach inside a polymer nanocomposite and apply heat to pre-selected subsets (e.g., causing them to dramatically change properties due to actuation, cross-linking, crystallization, or chemical reaction) without heating the sample surface or strongly affecting the remainder of the material. By utilizing optically-accessible additives including the particles themselves, the thermal gradient from the particle outward can be experimentally determined. In particular, rotational diffusion of anisotropic particles can be used to measure the temperature at the nanoparticle, which is the warmest point in a polymeric film or nanofiber under photothermal heating. Conversely, the same technique can be utilized to measure polymer dynamics in nanocomposites in the immediate vicinity of the particle. Funding: National Science Foundation CMMI-1069108.

  10. Electrostatic Charging of Polymers by Particle Impact at Low Pressures

    NASA Technical Reports Server (NTRS)

    Calle, Carlos I.; Mantovani, J. G.; Buhler, C. R.; Hogue, M. D.; Nowicki, A. W.; Groop, E. E.; Thompson, Karen (Technical Monitor)

    2001-01-01

    Studies of the electrostatic interaction between micrometer-sized particles and polymer surfaces are of great interest to NASA's planetary exploration program. The unmanned landing missions to Mars planned for this decade as well as the possible manned missions that might take place during the second decade of this century require a better understanding of the electrostatic response of the materials used in landing crafts and equipment when exposed to wind-blown dust or to surface dust and sand particles. We report on preliminary experiments designed to measure the electrostatic charge developed on five polymer surfaces as they are impacted simultaneously by Mars simulant particles less than 5 micrometers in diameter moving at 20 m/s. Experiments were performed in a CO2 atmosphere at 10 mbars of pressure using a particle delivery method that propels the particles with contact. Experiments were also performed in dry air at atmospheric pressures using a pressurized particle delivery system. The five polymer surfaces, commonly used in space applications, were chosen so that they span the triboelectric series.

  11. Correlation effects in dilute particle-polymer mixtures

    SciTech Connect

    Chatterjee, A.P.; Schweizer, K.S.

    1998-12-01

    The influence of chain connectivity and polymer excluded volume correlations on macromolecule-induced depletion interactions between spherical particles in the athermal limit is analyzed based on integral equation methods. Results for the sphere{endash}sphere second virial coefficient (B{sub 2}{sup cc}) and polymer-induced potential of mean force derived within the Percus{endash}Yevick (PY) and hypernetted chain (HNC) closure approximations for the polymer reference interaction site model (PRISM) are compared with those from prior theories for the depletion interaction which employ simplified models for macromolecules and/or ignore intermolecular packing effects. Distinctive differences are often found depending on system parameters, which are interpreted in terms of many-body correlation effects or nonathermal solvent quality. Comparisons with scaling and field-theoretic approaches in the dilute polymer limit, and limitations of the PY closure, are briefly addressed. {copyright} {ital 1998 American Institute of Physics.}

  12. Effect of fabric structure and polymer matrix on flexural strength, interlaminar shear stress, and energy dissipation of glass fiber-reinforced polymer composites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report the effect of glass fiber structure and the epoxy polymer system on the flexural strength, interlaminar shear stress (ILSS), and energy absorption properties of glass fiber-reinforced polymer (GFRP) composites. Four different GFRP composites were fabricated from two glass fiber textiles of...

  13. Dry particle coating of polymer particles for tailor-made product properties

    SciTech Connect

    Blümel, C. Schmidt, J. Dielesen, A. Sachs, M. Winzer, B. Peukert, W. Wirth, K.-E.

    2014-05-15

    Disperse polymer powders with tailor-made particle properties are of increasing interest in industrial applications such as Selective Laser Beam Melting processes (SLM). This study focuses on dry particle coating processes to improve the conductivity of the insulating polymer powder in order to assemble conductive devices. Therefore PP particles were coated with Carbon Black nanoparticles in a dry particle coating process. This process was investigated in dependence of process time and mass fraction of Carbon Black. The conductivity of the functionalized powders was measured by impedance spectroscopy. It was found that there is a dependence of process time, respectively coating ratio and conductivity. The powder shows higher conductivities with increasing number of guest particles per host particle surface area, i.e. there is a correlation between surface functionalization density and conductivity. The assembled composite particles open new possibilities for processing distinct polymers such as PP in SLM process. The fundamentals of the dry particle coating process of PP host particles with Carbon Black guest particles as well as the influence on the electrical conductivity will be discussed.

  14. Comparison of flexural strength between fiber-reinforced polymer and high-impact strength resin.

    PubMed

    Vojvodic, Denis; Matejicek, Franjo; Loncar, Ante; Zabarovic, Domagoj; Komar, Dragutin; Mehulic, Ketij

    2008-10-01

    Fractures of polymer material are one of the most frequent reasons for the repair of removable dental prostheses. Therefore, there is a constant endeavor to strengthen them, and polymer materials with high resistance to fracture are being developed. The aim of this study was to determine the flexural strength of polymer materials and their reinforcements and thus give preference to their clinical use. Specimens with dimensions 18 x 10 x 3 mm were tested after polymerization, immersion in water at a temperature 37 degrees C for 28 days, and thermocycling by using the "short-beam" method to determine the flexural strength. Microscopic examination was performed to determine the quality of bonding between the glass fibers and matrix. Common polymer materials (control group) demonstrated the lowest flexural strength, although, when reinforced with fibers they showed higher flexural strength, matching that of the tested high-impact strength resin. Thermocycled specimens had the highest flexural strength, whereas there was no difference (p > 0.05) between specimens tested after polymerization and immersion in water.

  15. Multi-Scale CNT-Based Reinforcing Polymer Matrix Composites for Lightweight Structures

    NASA Technical Reports Server (NTRS)

    Eberly, Daniel; Ou, Runqing; Karcz, Adam; Skandan, Ganesh; Mather, Patrick; Rodriguez, Erika

    2013-01-01

    Reinforcing critical areas in carbon polymer matrix composites (PMCs), also known as fiber reinforced composites (FRCs), is advantageous for structural durability. Since carbon nanotubes (CNTs) have extremely high tensile strength, they can be used as a functional additive to enhance the mechanical properties of FRCs. However, CNTs are not readily dispersible in the polymer matrix, which leads to lower than theoretically predicted improvement in mechanical, thermal, and electrical properties of CNT composites. The inability to align CNTs in a polymer matrix is also a known issue. The feasibility of incorporating aligned CNTs into an FRC was demonstrated using a novel, yet commercially viable nanofiber approach, termed NRMs (nanofiber-reinforcing mats). The NRM concept of reinforcement allows for a convenient and safe means of incorporating CNTs into FRC structural components specifically where they are needed during the fabrication process. NRMs, fabricated through a novel and scalable process, were incorporated into FRC test panels using layup and vacuum bagging techniques, where alternating layers of the NRM and carbon prepreg were used to form the reinforced FRC structure. Control FRC test panel coupons were also fabricated in the same manner, but comprised of only carbon prepreg. The FRC coupons were machined to size and tested for flexural, tensile, and compression properties. This effort demonstrated that FRC structures can be fabricated using the NRM concept, with an increased average load at break during flexural testing versus that of the control. The NASA applications for the developed technologies are for lightweight structures for in-space and launch vehicles. In addition, the developed technologies would find use in NASA aerospace applications such as rockets, aircraft, aircraft/spacecraft propulsion systems, and supporting facilities. The reinforcing aspect of the technology will allow for more efficient joining of fiber composite parts, thus offering

  16. A testing platform for durability studies of polymers and fiber-reinforced polymer composites under concurrent hygrothermo-mechanical stimuli.

    PubMed

    Gomez, Antonio; Pires, Robert; Yambao, Alyssa; La Saponara, Valeria

    2014-12-11

    The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

  17. A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

    PubMed Central

    Gomez, Antonio; Pires, Robert; Yambao, Alyssa; La Saponara, Valeria

    2014-01-01

    The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus. PMID:25548950

  18. Biological and physicochemical properties of carbon-graphite fibre-reinforced polymers intended for implant suprastructures.

    PubMed

    Segerström, Susanna; Sandborgh-Englund, Gunilla; Ruyter, Eystein I

    2011-06-01

    The aim of this study was to determine water sorption, water solubility, dimensional change caused by water storage, residual monomers, and possible cytotoxic effects of heat-polymerized carbon-graphite fibre-reinforced composites with different fibre loadings based on methyl methacrylate/poly(methyl methacrylate) (MMA/PMMA) and the copolymer poly (vinyl chloride-co-vinyl acetate). Two different resin systems were used. Resin A contained ethylene glycol dimethacrylate (EGDMA) and 1,4-butanediol dimethacrylate (1,4-BDMA); the cross-linker in Resin B was diethylene glycol dimethacrylate (DEGDMA). The resin mixtures were reinforced with 24, 36 and 47 wt% surface-treated carbon-graphite fibres. In addition, polymer B was reinforced with 58 wt% fibres. Water sorption was equal to or below 3.34±1.18 wt%, except for the 58 wt% fibre loading of polymer B (5.27±1.22 wt%). Water solubility was below 0.36±0.015 wt%, except for polymer B with 47 and 58 wt% fibres. For all composites, the volumetric increase was below 0.01±0.005 vol%. Residual MMA monomer was equal to or below 0.68±0.05 wt% for the fibre composites. The filter diffusion test and the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay demonstrated no cytotoxicity for the carbon-graphite fibre-reinforced composites, and residual cross-linking agents and vinyl chloride were not detectable by high-performance liquid chromatography (HPLC) analysis.

  19. Entanglement effect in polymer melts by Dissipative Particle Dynamics (DPD)

    NASA Astrophysics Data System (ADS)

    Khani, Shaghayegh; Maia, Joao

    2015-03-01

    Dissipative Particle Dynamics (DPD) is a mesoscale simulation method that has shown a very good potential in modeling different soft matter systems from colloidal suspensions to highly entangled polymers. Like any other simulation technique DPD is associated with some deficiencies, for instance in the case of entangled polymers soft repulsions used in DPD allow particle overlap which may result in topology violations that prevent the correct capturing of the entanglement effect. Therefore, in the present work in order to properly reproduce the dynamics and viscoelastic properties of polymers the soft repulsions between the particles are substituted with a repulsive potential between non-adjacent bonds of different FENE chains. Also, DPD is a coarse-grained simulation method that can be used to model time and length scales longer than atomistic models; however, due to the existence of an upper level limit for the level of coarse graining this method is not applicable for the whole mesoscopic range. Thus, this work represents a new approach for tuning the level of coarse-graining by adjusting the simulation parameters. The ability of the method in capturing the entanglement effects is validated by simulating dynamic and viscoelastic properties of polymers.

  20. Aluminum Alloys Reinforced by Nano-Particles Dispersion

    DTIC Science & Technology

    2010-03-01

    Jose Martin Herrera Ramirez Collaborator M. Sc. Ivanovich Estrada Guel Collaborator Eng. Wilber Antiinez Flores Collaborator Students: 1. Raul...Lucero, I. Estrada-Guel, D.C. Mendoza-Ruiz, M. Jose " Yacaman, Mechanical and Microstructural Characterization of Aluminum Reinforced with Carbon...9. Santos Beltran, V. Gallegos Orozco, F. Alvarado Hernandez, S. Haro Rodriguez, A. Lopez Ibarra and R. Martinez Sanchez. Synthesis and

  1. Effect of microstructure of nano- and micro-particle filled polymer composites on their tribo-mechanical performance

    NASA Astrophysics Data System (ADS)

    Devaprakasam, D.; Hatton, P. V.; Möbus, G.; Inkson, B. J.

    2008-08-01

    In this work we have investigated the influence of nanoscale and microscale structure on the tribo-mechanical performance and failure mechanisms of two biocompatible dental polymer composites, with different reinforcing particulates, using advanced microscopy techniques. Nano- and micro structural analysis reveals the shape, size and distribution of the particles in the composites. In the microparticle filled polymer composite (microcomposite), the particles are of irregular shape with sharp edges with non-uniform distribution in the matrix. However, in the nanoparticle filled composites (nanocomposite), filler particles are spherical in shape with uniform distribution in the matrix. From nanoindentation measurements, hardness and reduced modulus of the microcomposite were found to be heterogeneous. However, the hardness and reduced modulus of the nanocomposite were found to be homogeneous. The nanocomposite shows better tribo-mechanical performance compared to that of the microcomposite.

  2. Studies on Effective Elastic Properties of CNT/Nano-Clay Reinforced Polymer Hybrid Composite

    NASA Astrophysics Data System (ADS)

    Thakur, Arvind Kumar; Kumar, Puneet; Srinivas, J.

    2016-02-01

    This paper presents a computational approach to predict elastic propertiesof hybrid nanocomposite material prepared by adding nano-clayplatelets to conventional CNT-reinforced epoxy system. In comparison to polymers alone/single-fiber reinforced polymers, if an additional fiber is added to the composite structure, it was found a drastic improvement in resultant properties. In this regard, effective elastic moduli of a hybrid nano composite are determined by using finite element (FE) model with square representative volume element (RVE). Continuum mechanics based homogenization of the nano-filler reinforced composite is considered for evaluating the volumetric average of the stresses and the strains under different periodic boundary conditions.A three phase Halpin-Tsai approach is selected to obtain the analytical result based on micromechanical modeling. The effect of the volume fractions of CNTs and nano-clay platelets on the mechanical behavior is studied. Two different RVEs of nano-clay platelets were used to investigate the influence of nano-filler geometry on composite properties. The combination of high aspect ratio of CNTs and larger surface area of clay platelets contribute to the stiffening effect of the hybrid samples. Results of analysis are validated with Halpin-Tsai empirical formulae.

  3. Acoustic emission monitoring of concrete columns and beams strengthened with fiber reinforced polymer sheets

    NASA Astrophysics Data System (ADS)

    Ma, Gao; Li, Hui; Zhou, Wensong; Xian, Guijun

    2012-04-01

    Acoustic emission (AE) technique is an effective method in the nondestructive testing (NDT) field of civil engineering. During the last two decades, Fiber reinforced polymer (FRP) has been widely used in repairing and strengthening concrete structures. The damage state of FRP strengthened concrete structures has become an important issue during the service period of the structure and it is a meaningful work to use AE technique as a nondestructive method to assess its damage state. The present study reports AE monitoring results of axial compression tests carried on basalt fiber reinforced polymer (BFRP) confined concrete columns and three-point-bending tests carried on BFRP reinforced concrete beams. AE parameters analysis was firstly utilized to give preliminary results of the concrete fracture process of these specimens. It was found that cumulative AE events can reflect the fracture development trend of both BFRP confined concrete columns and BFRP strengthened concrete beams and AE events had an abrupt increase at the point of BFRP breakage. Then the fracture process of BFRP confined concrete columns and BFRP strengthened concrete beams was studied through RA value-average frequency analysis. The RA value-average frequency tendencies of BFRP confined concrete were found different from that of BFRP strengthened concrete beams. The variation tendency of concrete crack patterns during the loading process was revealed.

  4. Dynamic Effects in Elastothermodynamic Damping of Hollow Particle Reinforced Metal-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Srivastava, Sunil Kumar; Mishra, Bhanu Kumar

    2016-06-01

    The Metal-Matrix Composites (MMCs) containing hollow spherical reinforcements are under active development for the applications such as space structures, submarine hulls etc. where weight is of critical importance. When these materials are subjected to a time varying strain field, energy is dissipated because of the thermoelastic effect (Elastothermodynamic Damping or ETD). The quasi-static ETD analysis for the MMCs containing hollow spherical particles has been reported in literature. The entropic approach, which is better suited for composite materials with perfect or imperfect interfaces, is used for the analysis. In the present work, the effect of inertia forces is carried out on ETD of hollow particle-reinforced MMCs. For given particle volume fractions (V p ), the inertia forces are found to be more significant at higher value of thermal parameter (Ω T1) (alternatively, frequency of vibration if reinforcement radius is fixed), large cavity volume fraction (V h ) and low value of the parameter B1.

  5. Alignment of carbon nanotubes and reinforcing effects in nylon-6 polymer composite fibers

    NASA Astrophysics Data System (ADS)

    Rangari, Vijaya K.; Yousuf, Mohammed; Jeelani, Shaik; Pulikkathara, Merlyn X.; Khabashesku, Valery N.

    2008-06-01

    Alignment of pristine carbon nanotubes (P-CNTs) and fluorinated carbon nanotubes (F-CNTs) in nylon-6 polymer composite fibers (PCFs) has been achieved using a single-screw extrusion method. CNTs have been used as filler reinforcements to enhance the mechanical and thermal properties of nylon-6 composite fibers. The composites were fabricated by dry mixing nylon-6 polymer powder with the CNTs as the first step, then followed by the melt extrusion process of fiber materials in a single-screw extruder. The extruded fibers were stretched to their maxima and stabilized using a godet set-up. Finally, fibers were wound on a Wayne filament winder machine and tested for their tensile and thermal properties. The tests have shown a remarkable change in mechanical and thermal properties of nylon-6 polymer fibers with the addition of 0.5 wt% F-CNTs and 1.0 wt% of P-CNTs. To draw a comparison between the improvements achieved, the same process has been repeated with neat nylon-6 polymer. As a result, tensile strength has been increased by 230% for PCFs made with 0.5% F-CNTs and 1% P-CNTs as additives. These fibers have been further characterized by DSC, Raman spectroscopy and SEM which confirm the alignment of CNTs and interfacial bonding to nylon-6 polymer matrix.

  6. Alignment of carbon nanotubes and reinforcing effects in nylon-6 polymer composite fibers.

    PubMed

    Rangari, Vijaya K; Yousuf, Mohammed; Jeelani, Shaik; Pulikkathara, Merlyn X; Khabashesku, Valery N

    2008-06-18

    Alignment of pristine carbon nanotubes (P-CNTs) and fluorinated carbon nanotubes (F-CNTs) in nylon-6 polymer composite fibers (PCFs) has been achieved using a single-screw extrusion method. CNTs have been used as filler reinforcements to enhance the mechanical and thermal properties of nylon-6 composite fibers. The composites were fabricated by dry mixing nylon-6 polymer powder with the CNTs as the first step, then followed by the melt extrusion process of fiber materials in a single-screw extruder. The extruded fibers were stretched to their maxima and stabilized using a godet set-up. Finally, fibers were wound on a Wayne filament winder machine and tested for their tensile and thermal properties. The tests have shown a remarkable change in mechanical and thermal properties of nylon-6 polymer fibers with the addition of 0.5 wt% F-CNTs and 1.0 wt% of P-CNTs. To draw a comparison between the improvements achieved, the same process has been repeated with neat nylon-6 polymer. As a result, tensile strength has been increased by 230% for PCFs made with 0.5% F-CNTs and 1% P-CNTs as additives. These fibers have been further characterized by DSC, Raman spectroscopy and SEM which confirm the alignment of CNTs and interfacial bonding to nylon-6 polymer matrix.

  7. Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

    NASA Technical Reports Server (NTRS)

    Cox, Sarah B.; Lui, Donovan; Gou, Jihua

    2014-01-01

    The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Polysiloxanes contain a silicon oxycarbide backbone when pyrolized up to 1000C. Polycarbosilane, an organosilicon polymer, contain a silicon-carbon backbone; around 1200C, beta-SiC begins to crystallize. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Basalt is a naturally occurring material found in volcanic rock. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. Thermal and mechanical testing includes oxyacetylene torch testing and three point bend testing.

  8. Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

    NASA Technical Reports Server (NTRS)

    Cox, Sarah B.; Lui, Donovan; Wang, Xin; Gou, Jihua

    2014-01-01

    The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Polysiloxanes contain a silicon oxycarbide backbone when pyrolized up to 1000 deg C. Polycarbosilane, an organosilicon polymer, contain a silicon-carbon backbone; around 1200 deg C, Beta-SiC begins to crystallize. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Basalt is a naturally occurring material found in volcanic rock. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. Thermal and mechanical testing includes oxyacetylene torch testing and three point bend testing.

  9. Processing and Material Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics.

    NASA Technical Reports Server (NTRS)

    Cox, Sarah B.

    2014-01-01

    The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.

  10. Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

    NASA Technical Reports Server (NTRS)

    Cox, Sarah; Lui, Donovan; Gou, Jihua

    2014-01-01

    The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed, to be cured, and be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Polysiloxanes contain a silicon oxycarbide backbone when pyrolized up to 1000degC. Polycarbosilane, an organosilicon polymer, contain a silicon-carbon backbone; around 1200degC, -SiC begins to crystallize. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Basalt is a naturally occurring material found in volcanic rock. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. Testing for this included thermal and mechanical testing per ASTM standard tests.

  11. Composite material reinforced with atomized quasicrystalline particles and method of making same

    DOEpatents

    Biner, S.B.; Sordelet, D.J.; Lograsso, B.K.; Anderson, I.E.

    1998-12-22

    A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quasicrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked composite exhibits substantially improved yield strength, tensile strength, Young`s modulus (stiffness). 3 figs.

  12. Composite material reinforced with atomized quasicrystalline particles and method of making same

    DOEpatents

    Biner, Suleyman B.; Sordelet, Daniel J.; Lograsso, Barbara K.; Anderson, Iver E.

    1998-12-22

    A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quaiscrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked compositehibits substantially improved yield strength, tensile strength, Young's modulus (stiffness).

  13. Exfoliated graphite oxide decorated by PDMAEMA chains and polymer particles.

    PubMed

    Yang, Yongfang; Wang, Jie; Zhang, Jian; Liu, Jinchuan; Yang, Xinglin; Zhao, Hanying

    2009-10-06

    Exfoliated graphite oxide (GO) sheets with hydroxyl groups and amine groups on the surface were prepared by modification of graphite. Atom transfer radical polymerization (ATRP) initiator molecules were grafted onto the GO sheets by reactions of 2-bromo-2-methylpropionyl bromide with hydroxyl groups and amine groups. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) chains on the surface of GO sheets were synthesized by in-situ ATRP. X-ray photoelectron spectroscopy, thermogravimetric analysis, and transmission electron microscopy (TEM) results all demonstrated that polymer chains were successfully produced. After grafting of PDMAEMA, the dispersity of GO sheets in solvents was improved significantly. Poly(ethylene glycol dimethacrylate-co-methacrylic acid) particles were deposited on GO sheets via hydrogen bonding between MAA units on polymer particles and amine groups of PDMAEMA. TEM and scanning electron microscopy were used to characterize the structure of the nanocomposites.

  14. Investigation of Polymer Resin/Fiber Compatibility in Natural Fiber Reinforced Composite Automotive Materials

    SciTech Connect

    Fifield, Leonard S.; Huang, Cheng; Simmons, Kevin L.

    2010-01-01

    Natural fibers represent a lower density and potentially lower cost alternative to glass fibers for reinforcement of polymers in automotive composites. The high specific modulus and strength of bast fibers make them an attractive option to replace glass not only in non-structural automotive components, but also in semi-structural and structural components. Significant barriers to insertion of bast fibers in the fiber reinforced automotive composite market include the high moisture uptake of this lignocellulosic material relative to glass and the weak inherent interface between natural fibers and automotive resins. This work seeks to improve the moisture uptake and resin interfacing properties of natural fibers through improved fundamental understanding of fiber physiochemical architecture and development of tailored fiber surface modification strategies.

  15. Characteristics of fatigue life and damage accumulation of short fiber-reinforced polymer composites

    SciTech Connect

    Yokobori, A.T. Jr.; Takeda, Hidetoshi; Adachi, Takeshi; Ha, J.C.; Yokobori, Takeo

    1996-12-31

    The relation between fatigue life and damage accumulation of fiber-reinforced polymer composite (FRP) is not yet clarified. For practical use of FRP, it is necessary to relate the fatigue life to the mechanism of damage accumulation. Damage formation is controlled by the mechanical behavior of the interface between the matrix and fiber. The authors used short glass fiber-reinforced polycarbonate composite in the experiments. By using an in situ (real time) observational fatigue testing machine, they investigated the relationship between fatigue life and damage accumulation. From these results, the fatigue life of this material was found to be dominated by damage accumulation which results from microfracture at the interface between the matrix and fiber. This microfracture is controlled by a cycle-dependent mechanism.

  16. Smart fiber-reinforced polymer rods featuring improved ductility and health monitoring capabilities

    NASA Astrophysics Data System (ADS)

    Belarbi, Abdeldjelil; Watkins, Steve E.; Chandrashekhara, K.; Corra, Josh; Konz, Bethany

    2001-06-01

    The strain-measuring capability of fiber optic strain gages in fiber-reinforced polymer (FRP) rebars was investigated for failure-inducing loads. Fiber optic interferometric sensors were embedded in a pultruded carbon fiber core and then another layer of carbon fibers were filament wound around the core to form a shell. Pultrusion and filament winding techniques protect the fiber optic strain gages from the concrete environment while providing a secure bond to the core and additional ductility to the overall FRP rebar. Tests of coupon FRP rebar and of FRP-rebar-reinforced concrete beams show that the fiber optic strain gages can read internal strain through failure and can duplicate data from conventional linear variable differential transformers and electrical resistance strain gages. Also, the shell of the FRP rebar inside the concrete beams failed before the rebar core providing pseudo-ductility.

  17. Evaluation of RC Bridge Piers Retrofitted using Fiber-Reinforced Polymer (FRP)

    SciTech Connect

    Shayanfar, M. A.; Zarrabian, M. S.

    2008-07-08

    For many long years, steel reinforcements have been considered as the only tool for concrete confinements and studied widely, but nowadays application of Fiber Reinforced Polymer (FRP) as an effective alternative is well appreciated. Many bridges have been constructed in the past that are necessary to be retrofitted for resisting against the earthquake motions. The objective of this research is evaluation of nonlinear behavior of RC bridge piers. Eight RC bridge piers have been modeled by ABAQUS software under micromechanical model for homogeneous anisotropic fibers. Also the Bilinear Confinement Model by Nonlinear Transition Zone of Mirmiran has been considered. Then types and angles of fibers and their effects on the final responses were evaluated. Finally, effects of retrofitting are evaluated and some suggestions presented.

  18. Intra-lymph node injection of biodegradable polymer particles.

    PubMed

    Andorko, James I; Tostanoski, Lisa H; Solano, Eduardo; Mukhamedova, Maryam; Jewell, Christopher M

    2014-01-02

    Generation of adaptive immune response relies on efficient drainage or trafficking of antigen to lymph nodes for processing and presentation of these foreign molecules to T and B lymphocytes. Lymph nodes have thus become critical targets for new vaccines and immunotherapies. A recent strategy for targeting these tissues is direct lymph node injection of soluble vaccine components, and clinical trials involving this technique have been promising. Several biomaterial strategies have also been investigated to improve lymph node targeting, for example, tuning particle size for optimal drainage of biomaterial vaccine particles. In this paper we present a new method that combines direct lymph node injection with biodegradable polymer particles that can be laden with antigen, adjuvant, or other vaccine components. In this method polymeric microparticles or nanoparticles are synthesized by a modified double emulsion protocol incorporating lipid stabilizers. Particle properties (e.g. size, cargo loading) are confirmed by laser diffraction and fluorescent microscopy, respectively. Mouse lymph nodes are then identified by peripheral injection of a nontoxic tracer dye that allows visualization of the target injection site and subsequent deposition of polymer particles in lymph nodes. This technique allows direct control over the doses and combinations of biomaterials and vaccine components delivered to lymph nodes and could be harnessed in the development of new biomaterial-based vaccines.

  19. Space environmental effects on LDEF low Earth orbit exposed graphite reinforced polymer matrix composites

    NASA Technical Reports Server (NTRS)

    George, Pete

    1992-01-01

    The Long Duration Exposure Facility (LDEF) was deployed on April 7, 1984 in low earth orbit (LEO) at an altitude of 482 kilometers. On board experiments experienced the harsh LEO environment including atomic oxygen (AO), ultraviolet radiation (UV), and thermal cycling. During the 5.8 year mission, the LDEF orbit decayed to 340 kilometers where significantly higher AO concentrations exist. LDEF was retrieved on January 12, 1990 from this orbit. One experiment on board LDEF was M0003, Space Effects on Spacecraft Materials. As a subset of M0003 nearly 500 samples of polymer, metal, and glass matrix composites were flown as the Advanced Composites Experiment M0003-10. The Advanced Composites Experiment is a joint effort between government and industry with the Aerospace Corporation serving as the experiment integrator. A portion of the graphite reinforced polymer matrix composites were furnished by the Boeing Defense and Space Group, Seattle, Washington. Test results and discussions for the Boeing portion of M0003-10 are presented. Experiment and specimen location on the LDEF are presented along with a quantitative summary of the pertinent exposure conditions. Matrix materials selected for the test were epoxy, polysulfone, and polyimide. These composite materials were selected due to their suitability for high performance structural capability in spacecraft applications. Graphite reinforced polymer matrix composites offer higher strength to weight ratios along with excellent dimensional stability. The Boeing space exposed and corresponding ground control composite specimens were subjected to post flight mechanical, chemical, and physical testing in order to determine any changes in critical properties and performance characteristics. Among the more significant findings are the erosive effect of atomic oxygen on leading edge exposed specimens and microcracking in non-unidirectionally reinforced flight specimens.

  20. Formation of microscopic particles during the degradation of different polymers.

    PubMed

    Lambert, Scott; Wagner, Martin

    2016-10-01

    This study investigated the formation and size distribution of microscopic plastic particles during the degradation of different plastic materials. Particle number concentrations in the size range 30 nm-60 μm were measured by nanoparticle tracking analysis (NTA) and Coulter Counter techniques. Each of the plastics used exhibited a measureable increase in the release of particles into the surrounding solution, with polystyrene (PS) and polylactic acid (PLA) generating the highest particle concentrations. After 112 d, particle concentrations ranged from 2147 particles ml(-1) in the control (C) to 92,465 particles ml(-1) for PS in the 2-60 μm size class; 1.2 × 10(5) particles ml(-1) (C) to 11.6 × 10(6) for PLA in the 0.6-18 μm size class; and 0.2 × 10(8) particles ml(-1) (C) to 6.4 × 10(8) particles ml(-1) for PS in the 30-2000 nm size class (84 d). A classification of samples based on principal component analysis showed a separation between the different plastic types, with PLA clustering individually in each of the three size classes. In addition, particle size distribution models were used to examine more closely the size distribution data generated by NTA. Overall, the results indicate that at the beginning of plastic weathering processes chain scission at the polymer surface causes many very small particles to be released into the surrounding solution and those concentrations may vary between plastic types.

  1. Single-point scratching of 6061 Al alloy reinforced by different ceramic particles

    NASA Astrophysics Data System (ADS)

    Yan, Cheng; Zhang, Liangchi

    1994-11-01

    Aluminium alloys reinforced by ceramic particles have been widely used in aerospace and automotive industries for their high stiffness and wear resistance. However, the machining of such materials is difficult and would usually cause excessive tool wear. The effect of ceramic particles on the cutting mechanisms is also unclear. The purpose of this study is to investigate the cutting mechanisms and the relationship between specific energy of scratching and depth of cut (size effect). The single-point scratch test was carried out on 6061 Al and its composites reinforced by Al2O3 and SiC ceramic particles using a pyramid indenter. The results indicated that the scratch process was composed of rubbing, ploughing, plastic cutting and reinforcement fracture. A simple model was proposed to interpret the apparent size effect. The effect of reinforcement on the specific energy was correlated to the ratio of volume fraction to particle radius. The paper found that for machining MMCs, a larger depth of cut should be used to maintain a lower machining energy, especially for those with a larger ratio of volume fraction to particle radius.

  2. Effects of interface treatment on the fatigue behaviour of shape memory alloy reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Hiremath, S. R.; Harish, K.; Vasireddi, Ramakrishna; Benal, M. M.; Mahapatra, D. R.

    2015-04-01

    Interfacial properties of Shape Memory Alloy (SMA) reinforced polymer matrix composites can be enhanced by improving the interfacial bonding. This paper focuses on studying the interfacial stresses developed in the SMAepoxy interface due to various laser shot penning conditions. Fiber-pull test-setup is designed to understand the role of mechanical bias stress cycling and thermal actuation cycling. Phase transformation is tracked over mechanical and thermal fatigue cycles. A micromechanics based model developed earlier based on shear lag in SMA and energy based consistent homogenization is extended here to incorporate the stress-temperature phase diagram parameters for modeling fatigue.

  3. Microwave detection of delaminations between fiber reinforced polymer (FRP) composite and hardened cement paste

    NASA Astrophysics Data System (ADS)

    Hughes, D.; Kazemi, M.; Marler, K.; Zoughi, R.; Myers, J.; Nanni, A.

    2002-05-01

    Fiber reinforced polymer (FRP) composites are increasingly being used for the rehabilitation of concrete structures. Detection and characterization of delaminations between an FRP composite and a concrete surface are of paramount importance. Consequently, the development of a one sided, non-contact, real time and rapid nondestructive testing (NDT) technique for this purpose is of great interest. Near-field microwave NDT techniques, using open-ended rectangular waveguide probes, have shown great potential for detecting delaminations in layered composite structures such as these. The results of some theoretical and experimental investigations on a specially prepared cement paste specimen are presented here.

  4. A Lamb waves based statistical approach to structural health monitoring of carbon fibre reinforced polymer composites.

    PubMed

    Carboni, Michele; Gianneo, Andrea; Giglio, Marco

    2015-07-01

    This research investigates a Lamb-wave based structural health monitoring approach matching an out-of-phase actuation of a pair of piezoceramic transducers at low frequency. The target is a typical quasi-isotropic carbon fibre reinforced polymer aeronautical laminate subjected to artificial, via Teflon patches, and natural, via suitable low velocity drop weight impact tests, delaminations. The performance and main influencing factors of such an approach are studied through a Design of Experiment statistical method, considering both Pulse Echo and Pitch Catch configurations of PZT sensors. Results show that some factors and their interactions can effectively influence the detection of a delamination-like damage.

  5. Determination of Material Parameters for Microbuckling Analysis of Fiber Reinforced Polymer Matrix Composites

    NASA Astrophysics Data System (ADS)

    Romanowicz, M.

    2015-05-01

    This research focuses on studying the effect of the constitutive law adopted for a matrix material on the compressive response of a unidirectional fiber reinforced polymer matrix composite. To investigate this effect, a periodic unit cell model of a unidirectional composite with an initial fiber waviness and inelastic behavior of the matrix was used. The sensitivity of the compressive strength to the hydrostatic pressure, the flow rule and the fiber misalignment angle were presented. The model was verified against an analytical solution and experimental data. Results of this study indicate that a micromechanical model with correctly identified material parameters provides a useful alternative to theoretical models and experimentation.

  6. Nondestructive Evaluation of Carbon Fiber Reinforced Polymer Composites Using Reflective Terahertz Imaging.

    PubMed

    Zhang, Jin; Li, Wei; Cui, Hong-Liang; Shi, Changcheng; Han, Xiaohui; Ma, Yuting; Chen, Jiandong; Chang, Tianying; Wei, Dongshan; Zhang, Yumin; Zhou, Yufeng

    2016-06-14

    Terahertz (THz) time-domain spectroscopy (TDS) imaging is considered a nondestructive evaluation method for composite materials used for examining various defects of carbon fiber reinforced polymer (CFRP) composites and fire-retardant coatings in the reflective imaging modality. We demonstrate that hidden defects simulated by Teflon artificial inserts are imaged clearly in the perpendicular polarization mode. The THz TDS technique is also used to measure the thickness of thin fire-retardant coatings on CFRP composites with a typical accuracy of about 10 micrometers. In addition, coating debonding is successfully imaged based on the time-delay difference of the time-domain waveforms between closely adhered and debonded sample locations.

  7. Ferroelectret transducers for air-coupled ultrasonic testing of fiber-reinforced polymers

    NASA Astrophysics Data System (ADS)

    Gaal, M.; Döring, J.; Bartusch, J.; Lange, T.; Hillger, W.; Brekow, G.; Kreutzbruck, M.

    2013-01-01

    Ferroelectrets are promising materials for air-coupled ultrasonic transducers. A transducer made of polarized cellular polypropylene, including its electronic interface, was developed and compared with conventional air-coupled probes. Test pieces of fiber-reinforced polymer containing impact flaws and flat-bottom holes were inspected in transmission. The ferroelectret transducers achieved a considerably higher signal-to-noise ratio. The impacts were clearly visible with all transducers, but less noisy with ferroelectret transducers. The flat-bottom holes were better detectable than with a conventional probe with about the same focus size.

  8. Thermographic inspection of bond defects in Fiber Reinforced Polymer applied to masonry structures

    NASA Astrophysics Data System (ADS)

    Masini, N.; Aiello, M. A.; Capozzoli, L.; Vasanelli, E.

    2012-04-01

    Nowadays, externally bonded Fiber Reinforced Polymers (FRP) are extensively used for strengthening and repairing masonry and reinforced concrete existing structures; they have had a rapid spread in the area of rehabilitation for their many advantages over other conventional repair systems, such as lightweight, excellent corrosion and fatigue resistance, high strength, etc. FRP systems applied to masonry or concrete structures are typically installed using a wet-layup technique.The method is susceptible to cause flaws or defects in the bond between the FRP system and the substrate, which may reduce the effectiveness of the reinforcing systems and the correct transfer of load from the structure to the composite. Thus it is of primary importance to detect the presence of defects and to quantify their extension in order to eventually provide correct repair measurements. The IR thermography has been cited by the several guidelines as a good mean to qualitatively evaluate the presence of installation defects and to monitor the reinforcing system with time.The method is non-destructive and does not require contact with the composite or other means except air to detect the reinforcement. Some works in the literature have been published on this topic. Most of the researches aim at using the IR thermography technique to characterize quantitatively the defects in terms of depth, extension and type in order to have an experimental database on defect typology to evaluate the long term performances of the reinforcing system. Nevertheless, most of the works in the literature concerns with FRP applied to concrete structures without considering the case of masonry structures. In the present research artificial bond defects between FRP and the masonry substrate have been reproduced in laboratory and the IR multi temporal thermography technique has been used to detect them. Thermographic analysis has been carried out on two wall samples having limited dimensions (100 x 70 cm) both

  9. Nanomechanics and the viscoelastic behavior of carbon nanotube-reinforced polymers

    NASA Astrophysics Data System (ADS)

    Fisher, Frank Thomas

    Recent experimental results demonstrate that substantial improvements in the mechanical behavior of polymers can be attained using small amounts of carbon nanotubes as a reinforcing phase. While this suggests the potential use of carbon nanotube-reinforced polymers (NRPs) for structural applications, the development of predictive models describing NRP effective behavior will be critical in the development and ultimate employment of such materials. To date many researchers have simply studied the nanoscale behavior of NRPs using techniques developed for traditional composite materials. While such studies can be useful, this dissertation seeks to extend these traditional theories to more accurately model the nanoscale interaction of the NRP constituent phases. Motivated by micrographs showing that embedded nanotubes often exhibit significant curvature within the polymer, in the first section of this dissertation a hybrid finite element-micromechanical model is developed to incorporate nanotube waviness into micromechanical predictions of NRP effective modulus. While also suitable for other types of wavy inclusions, results from this model indicate that moderate nanotube waviness can dramatically decrease the effective modulus of these materials. The second portion of this dissertation investigates the impact of the nanotubes on the overall NRP viscoelastic behavior. Because the nanotubes are on the size scale of the individual polymer chains, nanotubes may alter the viscoelastic response of the NRP in comparison to that of the pure polymer; this behavior is distinctly different from that seen in traditional polymer matrix composites. Dynamic mechanical analysis (DMA) results for each of three modes of viscoelastic behavior (glass transition temperature, relaxation spectrum, and physical aging) are all consistent with the hypothesis of a reduced mobility, non-bulk polymer phase in the vicinity of the embedded nanotubes. These models represent initial efforts to

  10. Durability of carbon fiber reinforced shape memory polymer composites in space

    NASA Astrophysics Data System (ADS)

    Jang, Joon Hyeok; Hong, Seok Bin; Ahn, Yong San; Kim, Jin-Gyun; Nam, Yong-Youn; Lee, Geun Ho; Yu, Woong-Ryeol

    2016-04-01

    Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli. Recently, shape memory polymer composites (SMPCs) have been considered for space structure instead of shape memory alloys due to their deformability, lightweight and large recovery ratio, requiring characterization of their mechanical properties against harsh space environment and further prediction of the durability of SMPCs in space. As such, the durability of carbon fiber reinforced shape memory polymer composites (CF-SMPCs) was investigated using accelerated testing method based on short-term testing of CF-SMPCs in harsh condition. CF-SMPCs were prepared using woven carbon fabrics and a thermoset SMP via vacuum assisted resin transfer molding process. Bending tests with constant strain rate of CF-SMPCs were conducted using universal tensile machine (UTM) and Storage modulus test were conducted using dynamic mechanical thermal analysis (DMTA). Using the results, a master curve based on time-temperature superposition principle was then constructed, through which the mechanical properties of CF-SMPCs at harsh temperature were predicted. CF-SMPCs would be exposed to simulated space environments under ultra-violet radiations at various temperatures. The mechanical properties including flexural and tensile strength and shape memory properties of SMPCs would be measured using UTM before and after such exposures for comparison. Finally, the durability of SMPCs in space would be assessed by developing a degradation model of SMPC.

  11. Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix

    NASA Astrophysics Data System (ADS)

    Porras, R.; Bavykin, D. V.; Zekonyte, J.; Walsh, F. C.; Wood, R. J.

    2016-05-01

    Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the ‘drop-cast’ method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young’s modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young’s modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.

  12. Interfacial effects on dielectric properties of polymer-particle nanocomposites

    NASA Astrophysics Data System (ADS)

    Siddabattuni, Sasidhar Veeranjaneyulu

    Dielectric materials that are capable of efficiently storing large amounts of electrical energy are desirable for many electronic and power devices. Since the electrical energy density in a dielectric material is limited to epsilonVb2/2, where is the dielectric permittivity of the material and Vb is the breakdown strength, increased permittivity and breakdown strength are required for large energy storage density. Interfacial effects can influence the dielectric properties, especially dielectric breakdown resistance in polymer-particle nanocomposites. Several functional organophosphates were used to modify the surface of titania and barium titanate nanofiller particles in order to achieve covalent interface when interacted with polymer and to study the influence the electronic nature of filler surfaces on dielectric properties, in particular the breakdown resistance. Surface modified powders were analyzed by thermogravimetric analysis (TGA) and by X-ray photoelectron spectroscopy (XPS). The dielectric composite films obtained by incorporating surface modified powders in epoxy thermosetting polymer were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), impedance spectroscopy, and dielectric breakdown strength measurements. At 30 vol-% filler concentration, a calculated energy density of ˜8 J/cm3 was observed for titania based composites and ˜8.3 J/cm3 for barium titanate based composites involving electron scavenging interface with minimal dielectric losses compared to pure polymer. Covalent interface composites yielded energy density of ˜7.5 J/cm3 for barium titanate based composites at 30 vol.-%. The data indicate that improved dispersion, breakdown strengths and energy densities resulted when electron-poor functional groups were located at the particle surfaces even compared to covalent interface.

  13. Influence of protein hydrolysis on the mechanical properties of natural rubber composites reinforced with soy protein particles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For natural rubber applications, the reinforcing fillers are used to improve the mechanical properties of the rubber. Soy protein particles have been shown to reinforce natural rubber. The hydrolysis conditions of soy protein are studied to understand its effect on the particle size and size distrib...

  14. Large accumulation of micro-sized synthetic polymer particles in the sea surface microlayer.

    PubMed

    Song, Young Kyoung; Hong, Sang Hee; Jang, Mi; Kang, Jung-Hoon; Kwon, Oh Youn; Han, Gi Myung; Shim, Won Joon

    2014-08-19

    Determining the exact abundance of microplastics on the sea surface can be susceptible to the sampling method used. The sea surface microlayer (SML) can accumulate light plastic particles, but this has not yet been sampled. The abundance of microplastics in the SML was evaluated off the southern coast of Korea. The SML sampling method was then compared to bulk surface water filtering, a hand net (50 μm mesh), and a Manta trawl net (330 μm mesh). The mean abundances were in the order of SML water > hand net > bulk water > Manta trawl net. Fourier transform infrared spectroscopy (FTIR) identified that alkyds and poly(acrylate/styrene) accounted for 81 and 11%, respectively, of the total polymer content of the SML samples. These polymers originated from paints and the fiber-reinforced plastic (FRP) matrix used on ships. Synthetic polymers from ship coatings should be considered to be a source of microplastics. Selecting a suitable sampling method is crucial for evaluating microplastic pollution.

  15. Photocontrolled Cargo Release from Dual Cross-Linked Polymer Particles.

    PubMed

    Tan, Shereen; Cui, Jiwei; Fu, Qiang; Nam, Eunhyung; Ladewig, Katharina; Ren, Jing M; Wong, Edgar H H; Caruso, Frank; Blencowe, Anton; Qiao, Greg G

    2016-03-09

    Burst release of a payload from polymeric particles upon photoirradiation was engineered by altering the cross-linking density. This was achieved via a dual cross-linking concept whereby noncovalent cross-linking was provided by cyclodextrin host-guest interactions, and irreversible covalent cross-linking was mediated by continuous assembly of polymers (CAP). The dual cross-linked particles (DCPs) were efficiently infiltrated (∼80-93%) by the biomacromolecule dextran (molecular weight up to 500 kDa) to provide high loadings (70-75%). Upon short exposure (5 s) to UV light, the noncovalent cross-links were disrupted resulting in increased permeability and burst release of the cargo (50 mol % within 1 s) as visualized by time-lapse fluorescence microscopy. As sunlight contains UV light at low intensities, the particles can potentially be incorporated into systems used in agriculture, environmental control, and food packaging, whereby sunlight could control the release of nutrients and antimicrobial agents.

  16. Nanoscale damping characteristics of boron nitride nanotubes and carbon nanotubes reinforced polymer composites.

    PubMed

    Agrawal, Richa; Nieto, Andy; Chen, Han; Mora, Maria; Agarwal, Arvind

    2013-11-27

    This study compares the damping behavior of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) as reinforcement in PLC, a biodegradable copolymer. The damping behavior of PLC composites reinforced with 2 wt % or 5 wt % nanotube filler is evaluated by nanodynamic mechanical analysis (NanoDMA). The addition of 2 wt % CNT leads to the greatest enhancement in damping (tan δ) behavior. This is attributed to pullout in CNTs because of lower interfacial shear strength with the polymer matrix and a more effective sword-in-sheath mechanism as opposed to BNNTs which have bamboo-like nodes. BNNTs however have a superior distribution in the PLC polymer matrix enabling higher contents of BNNT to further enhance the damping behavior. This is in contrast with CNTs which agglomerate at higher concentrations, thus preventing further improvement at higher concentrations. It is observed that for different compositions, tan δ values show no significant changes over varying dynamic loads or prolonged cycles. This shows the ability of nanotube mechanisms to function at varying strain rates and to survive long cycles.

  17. On complexities of impact simulation of fiber reinforced polymer composites: a simplified modeling framework.

    PubMed

    Alemi-Ardakani, M; Milani, A S; Yannacopoulos, S

    2014-01-01

    Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study.

  18. On Complexities of Impact Simulation of Fiber Reinforced Polymer Composites: A Simplified Modeling Framework

    PubMed Central

    Alemi-Ardakani, M.; Milani, A. S.; Yannacopoulos, S.

    2014-01-01

    Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study. PMID:25431787

  19. Controlled isotropic or anisotropic nanoscale growth of coordination polymers: formation of hybrid coordination polymer particles.

    PubMed

    Lee, Hee Jung; Cho, Yea Jin; Cho, Won; Oh, Moonhyun

    2013-01-22

    The ability to fabricate multicompositional hybrid materials in a precise and controlled manner is one of the primary goals of modern materials science research. In addition, an understanding of the phenomena associated with the systematic growth of one material on another can facilitate the evolution of multifunctional hybrid materials. Here, we demonstrate precise manipulation of the isotropic and/or anisotropic nanoscale growth of various coordination polymers (CPs) to obtain heterocompositional hybrid coordination polymer particles. Chemical composition analyses conducted at every growth step reveal the formation of accurately assembled hybrid nanoscale CPs, and microscopy images are used to examine the morphology of the particles and visualize the hybrid structures. The dissimilar growth behavior, that is, growth in an isotropic or anisotropic fashion, is found to be dependent on the size of the metal ions involved within the CPs.

  20. Dispersion/Aggregation of polymer grafted nanorods in a polymer matrix studied by Dissipative Particle Dynamics

    NASA Astrophysics Data System (ADS)

    Maia, Joao; Khani, Shaghayegh

    2015-03-01

    Nanorods are incorporated into polymer matrices for fabricating composite materials with enhanced physical and mechanical properties.The final macroscopic properties of the composites are directly related to the dispersion and organization of the nanoparticles in the matrix. For instance, a significant improvement in the mechanical properties of the nanorod-polymer composites is observed upon formation of a percolating network. One way of controlling the assembly of nanorods in the polymer medium is adjusting the chemical interactions which is done through grafting polymer chains on the surface of the rods. The recent developments in the computational techniques have paved the road for further understanding of the controlled dispersion and aggregation of nanorods in polymer matrices. In this study, Dissipative Particle Dynamics (DPD) is employed in order to investigate the effect of enthalpic and entopic variables on the phase behavior of the abovementioned nanocomposites. In DPD, the interaction parameter between the components of the systems can be mapped onto the Flory-Huggins χ-parameter via well-known Groot-Warren expression. This works studies the effect of the enthalpic and entropic variables on phase transitions. The main goal is to provide a phase diagram than can be used to guide the experiments in designing new materials.

  1. In-vitro MRI detectability of interbody test spacers made of carbon fibre-reinforced polymers, titanium and titanium-coated carbon fibre-reinforced polymers.

    PubMed

    Ernstberger, Thorsten; Buchhorn, Gottfried; Baums, Mike Herbert; Heidrich, Gabert

    2007-04-01

    The purpose of this study was to investigate how different materials affect the magnetic resonance imaging (MRI) detectability of interbody test spacers (ITS). We evaluated the post-implantation MRI scans with T1 TSE sequences for three different ITS made of titanium, carbon fibre-reinforced polymers (CFRP) and titanium-coated CFRP, respectively. The main target variables were total artefact volume (TAV) and median artefact area (MAA). Additionally, implant volume (IV)/TAV and cross section (CS)/MAA ratio were determined. The t test and Newman-Keuls test for multiple comparisons were used for statistical analysis. TAV and MAA did not differ significantly between CFRP and titanium-coated CFRP, but were approximately twice as high for the titanium ITS (p < 0.001). MRI detectability was optimum for CFRP and titanium-coated CFRP, but was limited at the implant-bone interface of the titanium ITS. The material's susceptibility and the implant's dimensions affected MRI artefacting. Based on TAV, the volume of titanium surface coating in the ITS studied has no influence on susceptibility in MRI scans with T1 TSE sequences.

  2. Dissipative Particle Dynamics modeling of nanorod-polymer composites

    NASA Astrophysics Data System (ADS)

    Khani, Shaghayegh; Maia, Joao

    2014-11-01

    Recent years have seen a plethora of experimental methods for fabricating nanorod-polymer composites with enhanced physical and mechanical properties. The macroscopic properties of the composites are directly related to the dispersion and organization of the nanoparticles in the matrix. For instance, a significant improvement in the properties of the nanorod-polymer composites is observed upon formation of a percolating network. Thus, controlling the structure of the nanoparticles in the matrix will advance the technology in the field. One way of doing this is by adjusting the chemical interactions which is done through grafting polymer chains on the surface of the rods. Although the enthalpic interactions play the major role in such systems other entropic variables such as the dimension of the rods, density of grafting and etc. may influence the final morphology of the system. The recent developments in the computational techniques have paved the road for further understanding of the controlled assembly of nanorods in polymer matrices. In this study, Dissipative Particle Dynamics (DPD) is employed in order to investigate the effect of enthalpic and entopic variables on the phase behavior of the nanorod-polymer composites. DPD is a coarse-grained mesoscale method which has been found very promising in simulating multi component systems. The interaction parameter between the components of the systems can be mapped onto the Flory-Huggins χ-parameter via well-known Groot-Warren expression. The main goal of this work is to provide a phase diagram that can be used to guide the experiments in designing new materials.

  3. Novel hybrid columns made of ultra-high performance concrete and fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Zohrevand, Pedram

    The application of advanced materials in infrastructure has grown rapidly in recent years mainly because of their potential to ease the construction, extend the service life, and improve the performance of structures. Ultra-high performance concrete (UHPC) is one such material considered as a novel alternative to conventional concrete. The material microstructure in UHPC is optimized to significantly improve its material properties including compressive and tensile strength, modulus of elasticity, durability, and damage tolerance. Fiber-reinforced polymer (FRP) composite is another novel construction material with excellent properties such as high strength-to-weight and stiffness-to-weight ratios and good corrosion resistance. Considering the exceptional properties of UHPC and FRP, many advantages can result from the combined application of these two advanced materials, which is the subject of this research. The confinement behavior of UHPC was studied for the first time in this research. The stress-strain behavior of a series of UHPC-filled fiber-reinforced polymer (FRP) tubes with different fiber types and thicknesses were tested under uniaxial compression. The FRP confinement was shown to significantly enhance both the ultimate strength and strain of UHPC. It was also shown that existing confinement models are incapable of predicting the behavior of FRP-confined UHPC. Therefore, new stress-strain models for FRP-confined UHPC were developed through an analytical study. In the other part of this research, a novel steel-free UHPC-filled FRP tube (UHPCFFT) column system was developed and its cyclic behavior was studied. The proposed steel-free UHPCFFT column showed much higher strength and stiffness, with a reasonable ductility, as compared to its conventional reinforced concrete (RC) counterpart. Using the results of the first phase of column tests, a second series of UHPCFFT columns were made and studied under pseudo-static loading to study the effect of column

  4. Organoclay particles as reinforcing agents in polysaccharide films.

    PubMed

    Viota, J L; Lopez-Viota, M; Saake, B; Stana-Kleinschek, K; Delgado, A V

    2010-07-01

    In this work an investigation is described on the use of organically modified montmorillonite clay particles as stabilizers of bioplastic films based on xylan. With the aim of facilitating the incorporation of the nanoparticles to the films, the former were treated with a non-ionic surfactant, inulin. In order to evaluate the possible role of electrostatic interactions in the formation of montmorillonite/xylan complexes, an exhaustive electrokinetic characterization of the modified montmorillonite was carried out. Because montmorillonite has been modified by adsorption of the cationic surfactant DSDMAC, the electrophoretic mobility of montmorillonite in the absence of inulin is positive in a wide range of concentration of NaCl and CaCl(2). On the contrary, addition of KBr provokes a charge inversion when the salt concentration is around 0.05 M, suggesting adsorption of Br(-) ions. In the presence of inulin, the positive electrophoretic mobility decreases with the concentration of this surfactant, and this can be explained by assuming that inulin adsorption is accompanied by simultaneous DSDMAC desorption, eventually producing charge inversion, particularly in the presence of bromide ions. A thorough characterization of the wettability of the xylan films demonstrated that it is dominated by acid-base interactions and that incorporation of inulin-coated montmorillonite leads to a considerable reduction of the hydrophilic character of the films.

  5. Effect of Particle Size on Wear of Particulate Reinforced Aluminum Alloy Composites at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Kumar, Suresh; Pandey, Ratandeep; Panwar, Ranvir Singh; Pandey, O. P.

    2013-11-01

    The present paper describes the effect of particle size on operative wear mechanism in particle reinforced aluminum alloy composites at elevated temperatures. Two composites containing zircon sand particles of 20-32 μm and 106-125 μm were fabricated by stir casting process. The dry sliding wear tests of the developed composites were performed at low and high loads with variation in temperatures from 50 to 300 °C. The transition in wear mode from mild-to-severe was observed with variation in temperature and load. The wear at 200 °C presented entirely different wear behavior from the one at 250 °C. The wear rate of fine size reinforced composite at 200 °C at higher load was substantially lower than that of coarse size reinforced composite. Examination of wear tracks and debris revealed that delamination occurs after run in wear mode followed by formation of smaller size wear debris, transfer of materials from the counter surfaces and mixing of these materials on the contact surfaces. The volume loss was observed to increase with increase in load and temperature. Composite containing bigger size particles exhibit higher loss under similar conditions.

  6. Damage characterization for particles filled semi-crystalline polymer

    NASA Astrophysics Data System (ADS)

    Lauro, Franck; Balieu, Romain; Bennani, Bruno; Haugou, Gregory; Bourel, Benjamin; Chaari, Fahmi; Matsumoto, Tsukatada; Mottola, Ernesto

    2015-09-01

    Damage evolution and characterization in semi-crystalline polymer filled with particles under various loadings is still a challenge. A specific damage characterization method using Digital Image Correlation is proposed for a wide range of strain rates considering tensile tests with hydraulic jacks as well as Hopkinson's bars. This damage measurement is obtained by using and adapting the SEE method [1] which was developed to characterize the behaviour laws at constant strain rates of polymeric materials in dynamic. To validate the characterization process, various damage measurement techniques are used under quasi-static conditions before to apply the procedure in dynamic. So, the well-known damage characterization by loss of stiffness technique under quasi-static loading is applied to a polypropylene. In addition, an in-situ tensile test, carried out in a microtomograph, is used to observe the cavitation phenomenon in real time. A good correlation is obtained between all these techniques and consequently the proposed technique is supposed suitable for measuring the ductile damage observed in semi-crystalline polymers under dynamic loading. By applying it to the semi-crystalline polymer at moderate and high speed loadings, the damage evolution is measured and it is observed that the damage evolution is not strain rate dependent but the failure strain on the contrary is strain rate dependent.

  7. In situ compatibilizer-reinforced interface between a flexible polymer (a functionalized polypropylene) and a rodlike polymer (a thermotropic liquid crystalline polymer).

    PubMed

    Seo, Yongsok; Ninh, Tran Hai; Hong, Soon Man; Kim, Sehyun; Kang, Tae Jin; Kim, Hansung; Kim, Jinyeol

    2006-03-28

    We present an investigation of the interfacial reinforcement between a flexible folded-chain polymer (functionalized polypropylene-maleic anhydride-grafted polypropylene, MAPP) and a rodlike polymer (a themotropic liquid crystalline polymer, TCLP - poly(ester amide)). Fracture toughness was measured using an asymmetric double-cantilever beam test (ADCB). High fracture toughness at the bonding temperature of 200 degrees C indicates that a chemical reaction has occurred at the interface to provide a strong interaction between MAPP and TLCP. Despite the higher modulus of TLCP, the fracture was propagated in the TLCP phase because of inherent TLCP domain structure. An analysis on the locus of failure revealed that at constant bonding temperature the fracture toughness between MAPP and TLCP was influenced not only by the bonding temperature but also by the bonding time. The fracture toughness increased with the bonding temperature until 200 degrees C was reached and then decreased at higher bonding temperature. The fracture toughness increased with annealing time until it reached a plateau value. We ascribe the dependence of the fracture toughness on the bonding time to the progressive occurrence of two different failure mechanisms, adhesive failure and cohesive failure. The adhesive strength increased with bonding temperature whereas the cohesive strength decreased because of weaker adhesion between TLCP crystalline domains. The dependence of fracture toughness on bonding time was explained in terms of the TLCP crystalline domain structure.

  8. A complex reinforced polymer interposer with ordered Ni grid and SiC nano-whiskers polyimide composite based on micromachining technology

    NASA Astrophysics Data System (ADS)

    Liu, Yanmei; Sun, Yunna; Wang, Yan; Ding, Guifu; Sun, Bin; Zhao, Xiaolin

    2017-01-01

    A complex reinforced polymer interposer comprised with conductive Ni cylinders, ordered Ni grid and SiC nano-whiskers/Polyimide (PI) composite was proposed. The conductive Ni cylinders distributing in the middle of each Ni grid unite designed as the supporting structure were used as electric connecting component for the interposer and were insulated by the SiC nano-whiskers/PI composite. The comprehensive properties of the complex reinforced polymer interposer were improved by a complex reinforced mechanism: the improved thermal conductivity and mechanical strength by the Ni supporting structure and the reduced metal/polymer interfacial mismatch due to the SiC nano-whiskers/PI composite with the optimized mixture ratio. The above complex reinforced polymer interposer and a traditional reinforced polymer interposer only with Ni grid were fabricated using micro-machining technology for comparative analysis. The comprehensive properties of these two polymer interposers were analyzed respectively. Compared with the traditional design, the comprehensive properties of the proposed complex reinforced polymer interposer were improved further, such as, 21.3% increase for the Young modulus, 10.1% decrease for the coefficient of thermal expansion (CTE) and 54.9% increase for the thermal conductivity. Such complex reinforced mechanism based on the metal ordered grid and random nano-whiskers has potential to expand the applications of the polymer interposer. [Figure not available: see fulltext.

  9. Optimized process parameters for fabricating metal particles reinforced 5083 Al composite by friction stir processing

    PubMed Central

    Bauri, Ranjit; Yadav, Devinder; Shyam Kumar, C.N.; Janaki Ram, G.D.

    2015-01-01

    Metal matrix composites (MMCs) exhibit improved strength but suffer from low ductility. Metal particles reinforcement can be an alternative to retain the ductility in MMCs (Bauri and Yadav, 2010; Thakur and Gupta, 2007) [1,2]. However, processing such composites by conventional routes is difficult. The data presented here relates to friction stir processing (FSP) that was used to process metal particles reinforced aluminum matrix composites. The data is the processing parameters, rotation and traverse speeds, which were optimized to incorporate Ni particles. A wide range of parameters covering tool rotation speeds from 1000 rpm to 1800 rpm and a range of traverse speeds from 6 mm/min to 24 mm/min were explored in order to get a defect free stir zone and uniform distribution of particles. The right combination of rotation and traverse speed was found from these experiments. Both as-received coarse particles (70 μm) and ball-milled finer particles (10 μm) were incorporated in the Al matrix using the optimized parameters. PMID:26566541

  10. High-power picosecond laser drilling/machining of carbon fibre-reinforced polymer (CFRP) composites

    NASA Astrophysics Data System (ADS)

    Salama, A.; Li, L.; Mativenga, P.; Sabli, A.

    2016-02-01

    The large differences in physical and thermal properties of the carbon fibre-reinforced polymer (CFRP) composite constituents make laser machining of this material challenging. An extended heat-affected zone (HAZ) often occurs. The availability of ultrashort laser pulse sources such as picosecond lasers makes it possible to improve the laser machining quality of these materials. This paper reports an investigation on the drilling and machining of CFRP composites using a state-of-the-art 400 W picosecond laser system. Small HAZs (<25 µm) were obtained on the entry side of 6-mm-diameter hole drilled on sample of 6 mm thickness, whereas no HAZ was seen below the top surface on the cut surfaces. Multiple ring material removal strategy was used. Furthermore, the effect of laser processing parameters such as laser power, scanning speed and repetition rate on HAZ sizes and ablation depth was investigated.

  11. Repeated self-healing of microvascular carbon fibre reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Coope, T. S.; Wass, D. F.; Trask, R. S.; Bond, I. P.

    2014-11-01

    A self-healing, high performance, carbon fibre reinforced polymer (CFRP) composite is demonstrated by embedding a Lewis-acid catalytic curing agent within a laminate, manufactured using out of autoclave (OOA) composite manufacturing methods. Two configurations of healing agent delivery, pre-mixed and autonomous mixing, are investigated via injection of a healing agent through bio-inspired microvascular channels exposed on Mode I fractured crack planes. Healing is effected when an epoxy resin-solvent healing agent mixture reaches the boundary of embedded solid-state scandium(III) triflate (Sc(OTf)3) catalyst, located on the crack plane, to initiate the ring-opening polymerisation (ROP) of epoxides. Tailored self-healing agents confer high healing efficiency values after multiple healing cycles (69-108%) to successfully mitigate against crack propagation within the composite microstructure.

  12. Nondestructive Evaluation of Carbon Fiber Reinforced Polymer Composites Using Reflective Terahertz Imaging

    PubMed Central

    Zhang, Jin; Li, Wei; Cui, Hong-Liang; Shi, Changcheng; Han, Xiaohui; Ma, Yuting; Chen, Jiandong; Chang, Tianying; Wei, Dongshan; Zhang, Yumin; Zhou, Yufeng

    2016-01-01

    Terahertz (THz) time-domain spectroscopy (TDS) imaging is considered a nondestructive evaluation method for composite materials used for examining various defects of carbon fiber reinforced polymer (CFRP) composites and fire-retardant coatings in the reflective imaging modality. We demonstrate that hidden defects simulated by Teflon artificial inserts are imaged clearly in the perpendicular polarization mode. The THz TDS technique is also used to measure the thickness of thin fire-retardant coatings on CFRP composites with a typical accuracy of about 10 micrometers. In addition, coating debonding is successfully imaged based on the time-delay difference of the time-domain waveforms between closely adhered and debonded sample locations. PMID:27314352

  13. Segmenting delaminations in carbon fiber reinforced polymer composite CT using convolutional neural networks

    NASA Astrophysics Data System (ADS)

    Sammons, Daniel; Winfree, William P.; Burke, Eric; Ji, Shuiwang

    2016-02-01

    Nondestructive evaluation (NDE) utilizes a variety of techniques to inspect various materials for defects without causing changes to the material. X-ray computed tomography (CT) produces large volumes of three dimensional image data. Using the task of identifying delaminations in carbon fiber reinforced polymer (CFRP) composite CT, this work shows that it is possible to automate the analysis of these large volumes of CT data using a machine learning model known as a convolutional neural network (CNN). Further, tests on simulated data sets show that with a robust set of experimental data, it may be possible to go beyond just identification and instead accurately characterize the size and shape of the delaminations with CNNs.

  14. First light with a carbon fiber reinforced polymer 0.4 meter telescope

    NASA Astrophysics Data System (ADS)

    Wilcox, Christopher C.; Santiago, Freddie; Jungwirth, Matthew E.; Martinez, Ty; Restaino, Sergio R.; Bagwell, Brett; Romeo, Robert

    2014-03-01

    For the passed several years, the Naval Research Laboratory (NRL) has been investigating the use of Carbon Fiber Reinforced Polymer (CFRP) material in the construction of a telescope assembly including the optical components. The NRL, Sandia National Laboratories (SNL), and Composite Mirror Applications, Inc. (CMA) have jointly assembled a prototype telescope and achieved "first light" images with a CFRP 0.4 m aperture telescope. CFRP offers several advantages over traditional materials such as creating structures that are lightweight and low coefficient of thermal expansion and conductivity. The telescope's primary and secondary mirrors are not made from glass, but CFRP, as well. The entire telescope weighs approximately 10 kg while a typical telescope of this size would weigh quite a bit more. We present the achievement of "first light" with this telescope demonstrating the imaging capabilities of this prototype and the optical surface quality of the mirrors with images taken during a day's quiescent periods.

  15. Carbon Fiber Reinforced Polymer (CFRP) Optics Quality Assessment for Lightweight Deployable Optics

    NASA Astrophysics Data System (ADS)

    Andrews, J.; Martinez, T.; Restaino, S.; Santiago, F.; Wilcox, C.; Teare, S.; Romeo, R.; Martin, R.

    2010-09-01

    The Naval Research Laboratory and Composite Mirror Applications (CMA) have been working together for several years on the development of Carbon Fiber Reinforced Polymer (CFRP) optics and telescopes. We have documented the potential advantages of this technology in several other publications, including structural, thermal and weight advantages over traditional steel and glass optical systems. In this paper we present results of a battery of optical tests done on various CFRP replicated mirrors. Our goal is to demonstrate not only the optical quality of such mirrors but also their reproducibility and stability. We show test results on a sample of four mirrors. We performed extensive optical tests and also stability and repeatability tests. These tests are geared towards proving the use of this technology for a variety of optical applications including use in our CFRP telescopes.

  16. Low-velocity impact damage characterization of carbon fiber reinforced polymer (CFRP) using infrared thermography

    NASA Astrophysics Data System (ADS)

    Li, Yin; Zhang, Wei; Yang, Zheng-wei; Zhang, Jin-yu; Tao, Sheng-jie

    2016-05-01

    Carbon fiber reinforced polymer (CFRP) after low-velocity impact is detected using infrared thermography, and different damages in the impacted composites are analyzed in the thermal maps. The thermal conductivity under pulse stimulation, frictional heating and thermal conductivity under ultrasonic stimulation of CFRP containing low-velocity impact damage are simulated using numerical simulation method. Then, the specimens successively exposed to the low-velocity impact are respectively detected using the pulse infrared thermography and ultrasonic infrared thermography. Through the numerical simulation and experimental investigation, the results obtained show that the combination of the above two detection methods can greatly improve the capability for detecting and evaluating the impact damage in CFRP. Different damages correspond to different infrared thermal images. The delamination damage, matrix cracking and fiber breakage are characterized as the block-shape hot spot, line-shape hot spot, and

  17. Influence of attenuation on acoustic emission signals in carbon fiber reinforced polymer panels.

    PubMed

    Asamene, Kassahun; Hudson, Larry; Sundaresan, Mannur

    2015-05-01

    Influence of attenuation on acoustic emission (AE) signals in Carbon Fiber Reinforced Polymer (CFRP) crossply and quasi-isotropic panels is examined in this paper. Attenuation coefficients of the fundamental antisymmetric (A0) and symmetric (S0) wave modes were determined experimentally along different directions for the two types of CFRP panels. In the frequency range from 100 kHz to 500 kHz, the A0 mode undergoes significantly greater changes due to material related attenuation compared to the S0 mode. Moderate to strong changes in the attenuation levels were noted with propagation directions. Such mode and frequency dependent attenuation introduces major changes in the characteristics of AE signals depending on the position of the AE sensor relative to the source. Results from finite element simulations of a microscopic damage event in the composite laminates are used to illustrate attenuation related changes in modal and frequency components of AE signals.

  18. Recycling carbon fibre reinforced polymers for structural applications: technology review and market outlook.

    PubMed

    Pimenta, Soraia; Pinho, Silvestre T

    2011-02-01

    Both environmental and economic factors have driven the development of recycling routes for the increasing amount of carbon fibre reinforced polymer (CFRP) waste generated. This paper presents a review of the current status and outlook of CFRP recycling operations, focusing on state-of-the-art fibre reclamation and re-manufacturing processes, and on the commercialisation and potential applications of recycled products. It is shown that several recycling and re-manufacturing processes are reaching a mature stage, with implementations at commercial scales in operation, production of recycled CFRPs having competitive structural performances, and demonstrator components having been manufactured. The major challenges for the sound establishment of a CFRP recycling industry and the development of markets for the recyclates are summarised; the potential for introducing recycled CFRPs in structural components is discussed, and likely promising applications are investigated.

  19. Laser Cutting of Carbon Fiber Reinforced Polymers using Highly Brilliant Laser Beam Sources

    NASA Astrophysics Data System (ADS)

    Klotzbach, Annett; Hauser, Markus; Beyer, Eckhard

    Carbon fiber reinforced polymers (CFRP) are applied more and more in the aircraft industry as well as in the automobile industry. The principal reason is the highly mechanical load capacity along with the low density. Moreover, the corrosion resistance plus the damping behavior of the material can be utilized fully in highly stressed structures. However, the concept of manufacture CFRP-parts close to the final contour does not substitute the need of cutting them. The different properties of fiberand matrix-material constitute an ambitious challenge while cutting CFRP using a laser beam. This paper deals with elementary analysis of the laser remote cutting process and the gas assisted laser cutting of CFRP.

  20. Tribological properties of metal-matrix composite materials reinforced by superelastic hard carbon particles

    NASA Astrophysics Data System (ADS)

    Ushakova, I. N.; Drozdova, E. I.; Chernogorova, O. P.; Blinov, V. M.; Ekimov, E. A.

    2016-05-01

    Metal-matrix composite materials (CMs) are synthesized from a mixture of a metal powder (Ti, Fe, Co, Ni, Cu, Al-based alloy) and fullerenes (10 wt %). The thermobaric synthesis conditions (700-1000°C, 5-8 GPa) ensure the collapse of fullerene molecules and their transformation into superelastic carbon phase particles with an indentation hardness H IT = 10-37 GPa, an elastic modulus E IT = 60-260 GPa, and an elastic recovery of >80% upon indentation. After reinforcing by superelastic hard carbon, the friction coefficient of CM decreases by a factor of 2-4 as compared to the friction coefficient of the matrix metal, and the abrasive wear resistance increases by a factor of 4-200. Superelastic hard carbon particles are a unique reinforcing material for an increase in the wear resistance and a simultaneous decrease in the friction coefficient of CM.

  1. Heat transfer mechanisms in fiber-reinforced polymer composites bonded to concrete

    NASA Astrophysics Data System (ADS)

    Brown, Jeff; Baker, Rebecca; Kallemeyn, Lisa

    2007-04-01

    This research project investigated heat transfer mechanisms that occur during radiant heating of glass/epoxy composites bonded to concrete. The ultimate goal is to develop a field procedure for estimating the thickness of fiber-reinforced polymer (FRP) composites used to strengthen existing reinforced concrete structures. Thickness is an important parameter in the design and implementation of nondestructive testing procedures that evaluate bond in FRP systems. Four concrete samples (15 cm x 30 cm x 5 cm) were constructed with glass/epoxy composite bonded to the surface. The thickness of the composite varied from 1mm to 4mm and thermocouples were placed at 1mm intervals through the depth of the composite. Experimental data was compared with a simple theoretical model that predicts the surface temperature response of a layered system subjected to a uniform heat flux. Two factors were shown to significantly influence the heat transfer mechanism: surface absorptivity of the FRP composite and convective cooling. Additional analytical modeling using the finite element method was performed to account for these affects in an effort to obtain a better estimate of FRP thickness based on experimental data.

  2. Fabrication Of Carbon-Boron Reinforced Dry Polymer Matrix Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

    1999-01-01

    Future generation aerospace vehicles will require specialized hybrid material forms for component structure fabrication. For this reason, high temperature composite prepregs in both dry and wet forms are being developed at NASA Langley Research Center (LaRC). In an attempt to improve compressive properties of carbon fiber reinforced composites, a hybrid carbon-boron tape was developed and used to fabricate composite laminates which were subsequently cut into flexural and compression specimens and tested. The hybrid material, given the designation HYCARB, was fabricated by modifying a previously developed process for the manufacture of dry polymer matrix composite (PMC) tape at LaRC. In this work, boron fibers were processed with IM7/LaRC(TradeMark)IAX poly(amide acid) solution-coated prepreg to form a dry hybrid tape for Automated Tow Placement (ATP). Boron fibers were encapsulated between two (2) layers of reduced volatile, low fiber areal weight poly(amide acid) solution-coated prepreg. The hybrid prepreg was then fully imidized and consolidated into a dry tape suitable for ATP. The fabrication of a hybrid boron material form for tow placement aids in the reduction of the overall manufacturing cost of boron reinforced composites, while realizing the improved compression strengths. Composite specimens were press-molded from the hybrid material and exhibited excellent mechanical properties.

  3. Development of multifunctional fiber reinforced polymer composites through ZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Patterson, Brendan A.; Hwang, Hyun-Sik; Sodano, Henry A.

    2016-04-01

    Piezoelectric nanowires, in particular zinc oxide (ZnO) nanowires, have been vastly used in the fabrication of electromechanical devices to convert wasted mechanical energy into useful electrical energy. Over recent years, the growth of vertically aligned ZnO nanowires on various structural fibers has led to the development of fiber-based nanostructured energy harvesting devices. However, the development of more realistic energy harvesters that are capable of continuous power generation requires a sufficient mechanical strength to withstand typical structural loading conditions. Yet, a durable, multifunctional material system has not been developed thoroughly enough to generate electrical power without deteriorating the mechanical performance. Here, a hybrid composite energy harvester is fabricated in a hierarchical design that provides both efficient power generating capabilities while enhancing the structural properties of the fiber reinforced polymer composite. Through a simple and low-cost process, a modified aramid fabric with vertically aligned ZnO nanowires grown on the fiber surface is embedded between woven carbon fabrics, which serve as the structural reinforcement as well as the top and the bottom electrodes of the nanowire arrays. The performance of the developed multifunctional composite is characterized through direct vibration excitation and tensile strength examination.

  4. Novel mucoadhesion tests for polymers and polymer-coated particles to design optimal mucoadhesive drug delivery systems.

    PubMed

    Takeuchi, Hirofumi; Thongborisute, Jringjai; Matsui, Yuji; Sugihara, Hikaru; Yamamoto, Hiromitsu; Kawashima, Yoshiaki

    2005-11-03

    To design an effective particulate drug delivery system having mucoadhesive function, several mucoadhesion tests for polymers and the resultant particulate systems were developed. Mucin particle method is a simple mucoadhesion test for polymers, in which the commercial mucin particles are used. By measuring the change in particle size or zeta potential of the mucin particle in a certain concentration of polymer solution, we could estimate the extent of their mucoadhesive property. BIACORE method is also a novel mucoadhesion test for polymers. On passing through the mucin suspension on the polymer-immobilized chip of BIACORE instrument, the interaction was quantitatively evaluated with the change in its response diagram. By using these mucoadhesion tests, we detected a strong mucoadhesive property of several types of chitosan and Carbopol. Evaluation of mucoadhesive property of polymer-coated particulate systems was demonstrated with the particle counting method developed by us. To detect the mucoadhesive phenomena in the intestinal tract, we observed the rat intestine with the confocal laser scanning microscope (CLSM) after oral administration of the particulate systems. The resultant photographs clearly showed a longer retention of submicron-sized chitosan-coated liposomes (ssCS-Lip) in the intestinal tract than other liposomal particles tested such as non-coated liposomes and chitosan-coated multilamellar one. These observations explained well the superiority of the ssCS-Lip as drug carrier in oral administration of calcitonin in rats than other liposomal particles.

  5. Advances in Thermal Spray Deposition of Billets for Particle Reinforced Light Metals

    NASA Astrophysics Data System (ADS)

    Wenzelburger, Martin; Zimmermann, Christian; Gadow, Rainer

    2007-04-01

    Forming of light-metals in semi-solid state offers some advantages like low process temperatures, improved mould durability, good flow behavior and fine, globular microstructure of the final material. By the introduction of ceramic particles, increased elastic modulus and yield strength as well as wear resistance and creep behavior can be obtained. By semi-solid forging or semi-solid casting, particle reinforced metals (PRM) can be produced with improved matrix microstructure and beneficial forming process parameters compared to conventional MMC manufacturing techniques. The production of this kind of light metal matrix composites requires the supply of dense semi-finished parts with well defined volume fractions of homogeneously distributed particulate reinforcement. A manufacturing method for cylindrical light metal billets is described that applies thermal spraying as a build-up process for simultaneous deposition of matrix and reinforcement phase with cored wires as spraying material. Thermal spraying leads to small grain sizes and prevents dendrite formation. However, long process cycle times lead to billet heating and recrystallization of the matrix microstructure. In order to preserve small grain sizes that enable semi-solid forming, the thermal spraying process was analyzed by in-flight particle analysis and thermography. As a consequence, the deposition process was optimized by adaptation of the thermal spraying parameters and by application of additional cooling, leading to lower billet temperatures and finer PRM billet microstructure.

  6. Advances in Thermal Spray Deposition of Billets for Particle Reinforced Light Metals

    SciTech Connect

    Wenzelburger, Martin; Zimmermann, Christian; Gadow, Rainer

    2007-04-07

    Forming of light-metals in semi-solid state offers some advantages like low process temperatures, improved mould durability, good flow behavior and fine, globular microstructure of the final material. By the introduction of ceramic particles, increased elastic modulus and yield strength as well as wear resistance and creep behavior can be obtained. By semi-solid forging or semi-solid casting, particle reinforced metals (PRM) can be produced with improved matrix microstructure and beneficial forming process parameters compared to conventional MMC manufacturing techniques. The production of this kind of light metal matrix composites requires the supply of dense semi-finished parts with well defined volume fractions of homogeneously distributed particulate reinforcement. A manufacturing method for cylindrical light metal billets is described that applies thermal spraying as a build-up process for simultaneous deposition of matrix and reinforcement phase with cored wires as spraying material. Thermal spraying leads to small grain sizes and prevents dendrite formation. However, long process cycle times lead to billet heating and recrystallization of the matrix microstructure. In order to preserve small grain sizes that enable semi-solid forming, the thermal spraying process was analyzed by in-flight particle analysis and thermography. As a consequence, the deposition process was optimized by adaptation of the thermal spraying parameters and by application of additional cooling, leading to lower billet temperatures and finer PRM billet microstructure.

  7. Effect of soluble polymer binder on particle distribution in a drying particulate coating.

    PubMed

    Buss, Felix; Roberts, Christine C; Crawford, Kathleen S; Peters, Katharina; Francis, Lorraine F

    2011-07-01

    Soluble polymer is frequently added to inorganic particle suspensions to provide mechanical strength and adhesiveness to particulate coatings. To engineer coating microstructure, it is essential to understand how drying conditions and dispersion composition influence particle and polymer distribution in a drying coating. Here, a 1D model revealing the transient concentration profiles of particles and soluble polymer in a drying suspension is proposed. Sedimentation, evaporation and diffusion govern particle movement with the presence of soluble polymer influencing the evaporation rate and solution viscosity. Results are summarized in drying regime maps that predict particle accumulation at the free surface or near the substrate as conditions vary. Calculations and experiments based on a model system of poly(vinyl alcohol) (PVA), silica particles and water reveal that the addition of PVA slows the sedimentation and diffusion of the particles during drying such that accumulation of particles at the free surface is more likely.

  8. Degradable phosphate glass fiber reinforced polymer matrices: mechanical properties and cell response.

    PubMed

    Brauer, Delia S; Rüssel, Christian; Vogt, Sebastian; Weisser, Jürgen; Schnabelrauch, Matthias

    2008-01-01

    The development of biodegradable materials for internal fracture fixation is of great interest, as they would both eliminate the problem of stress shielding and obviate the need for a second operation to remove fixation devices. Preliminary investigations for the production of degradable fiber reinforced polymer composite materials are detailed. Composites were produced of phosphate invert glass fibers of the glass system P(2)O(5)-CaO-MgO-Na(2)O-TiO(2), which showed a low solubility in previous work. The fibers were embedded into a matrix of a degradable organic polymer network based on methacrylate-modified oligolactide. Fracture behavior, bending strength and elastic modulus were evaluated during 3-point bending tests and the fracture surface of the composites was investigated using a scanning electron microscope. Short-term biocompatibility was tested in an FDA/EtBr viability assay using MC3T3-E1 murine pre-osteoblast cells and showed a good cell compatibility of the composite materials. Results suggested that these composite materials are biocompatible and show mechanical properties which are of interest for the production of degradable bone fixation devices.

  9. Stabilizing Surfactant Templated Cylindrical Mesopores in Polymer and Carbon Films through Composite Formation with Silica Reinforcement

    SciTech Connect

    Song, Lingyan; Feng, Dan; Lee, Hae-Jeong; Wang, Chengqing; Wu, Quanyan; Zhao, Dongyuan; Vogt, Bryan D.

    2010-10-22

    A facile approach to maintain the periodic mesostructure of cylindrical pores in polymer-resin and carbon films after thermal template removal is explored through the reactive coassembly of resol (carbon precursor) and tetraethylorthosilicate (silica precursor) with triblock copolymer Pluronic F127. Without silica, a low porosity, disordered film is formed after pyrolysis despite the presence of an ordered mesostructure prior to template removal. However for silica concentration greater than 25 wt %, pyrolysis at 350 C yields a mesoporous silica-polymer film with well-defined pore mesostructure. These films remain well ordered upon carbonization at 800 C. In addition to the mesostructural stability, the addition of silica to the matrix impacts other morphological characteristics. For example, the average pore size and porosity of the films increase from 3.2 to 7.5 nm and 12 to 45%, respectively, as the concentration of silica in the wall matrix increases from 0 to 32 wt %. The improved thermal stability of the ordered mesostructure with the addition of silica to the matrix is attributed to the reinforcement of the mechanical properties leading to resistance to stress induced collapse of the mesostructure during template removal.

  10. Diode laser cladding of Co-based composite coatings reinforced by spherical WC particles

    NASA Astrophysics Data System (ADS)

    Janicki, Damian; Górka, Jacek; Czupryński, Artur; Kwaśny, Waldemar; Żuk, Marcin

    2016-12-01

    A laser cladding system consisting of a direct diode laser with the flat-top beam profile and an off-axis powder injection nozzle has been used to fabricate Co-based (Satellite 6) metal matrix composite coatings reinforced by spherical-shaped WC particles. Non-porous coatings with the WC fraction of about 50 vol.% and a low dissolution of the WC particles in the matrix have been obtained. The heat input level affects the degree of WC dissolution and the matrix mean free path between the embedded WC particles. Comparative erosion tests between the metallic Satellite 6 and composite Satellite 6/WC coatings showed that the composite coatings exhibit a superior erosion resistance only at the oblique impingement condition. Generally, a low erosion resistance of the composite coatings at the normal impingement is mainly attributed to a very smooth interface between the spherical-shaped WC particles and the matrix alloy.

  11. Polymer composites reinforced by locking-in a liquid-crystalline assembly of cellulose nanocrystallites.

    PubMed

    Tatsumi, Mio; Teramoto, Yoshikuni; Nishio, Yoshiyuki

    2012-05-14

    An attempt was made to synthesize novel composites comprising poly(2-hydroxyethyl methacrylate) (PHEMA) and cellulose nanocrystallites (CNC) (acid-treated cotton microfibrils) from suspensions of CNC in an aqueous 2-hydroxyethyl methacrylate (HEMA) monomer solution. The starting suspensions (∼5 wt % CNC) separated into an isotropic upper phase and an anisotropic bottom one in the course of quiescent standing. By way of polymerization of HEMA in different phase situations of the suspensions, we obtained films of three polymer composites, PHEMA-CNC(iso), PHEMA-CNC(aniso), and PHEMA-CNC(mix), coming from the isotropic phase, anisotropic phase, and embryonic nonseparating mixture, respectively. All the composites were transparent and, more or less, birefringent under a polarized optical microscope. A fingerprint texture typical of cholesteric liquid crystals of longer pitch spread widely in PHEMA-CNC(aniso) but rather locally appeared in PHEMA-CNC(iso). Any of the CNC incorporations into the PHEMA matrix improved the original thermal and mechanical properties of this amorphous polymer material. In dynamic mechanical measurements, the locking-in of the respective CNC assemblies gave rise to an increase in the glass-state modulus E' of PHEMA as well as a marked suppression of the E'-falling at temperatures higher than T(g) (≈ 110 °C) of the vinyl polymer. It was also observed for the composites that their modulus E' rerose in a range of about 150-190 °C, which was attributable to a secondary cross-linking formation between PHEMA chains mediated by the acidic CNC filler. The mechanical reinforcement effect of the CNC dispersions was ensured in a tensile test, whereby PHEMA-CNC(aniso) was found to surpass the other two composites in stiffness and strength.

  12. Schmidt number effects in dissipative particle dynamics simulation of polymers.

    PubMed

    Symeonidis, Vasileios; Karniadakis, George Em; Caswell, Bruce

    2006-11-14

    Simulation studies for dilute polymeric systems are presented using the dissipative particle dynamics method. By employing two different thermostats, the velocity-Verlet and Lowe's scheme, we show that the Schmidt number (S(c)) of the solvent strongly affects nonequilibrium polymeric quantities. The fractional extension of wormlike chains subjected to steady shear is obtained as a function of S(c). Poiseuille flow in microchannels for fixed polymer concentration and varying number of repeated units within a chain is simulated. The nonuniform concentration profiles and their dependence on S(c) are computed. We show the effect of the bounce-forward wall boundary condition on the depletion layer thickness. A power law fit of the velocity profile in stratified Poiseuille flow in a microchannel yields wall viscosities different from bulk values derived from uniform, steady plane Couette flow. The form of the velocity profiles indicates that the slip flow model is not useful for the conditions of these calculations.

  13. Jet Electrochemical Machining of Particle Reinforced Aluminum Matrix Composites with Different Neutral Electrolytes

    NASA Astrophysics Data System (ADS)

    Hackert-Oschätzchen, M.; Lehnert, N.; Martin, A.; Schubert, A.

    2016-03-01

    Conventional mechanical machining of particle reinforced aluminum matrix composites (AMCs) is challenging because the hard ceramic particles in the soft aluminum matrix lead to an increased tool wear. Furthermore, the mechanical and thermal impact during conventional machining affects the microstructure of the AMCs. Electrochemical machining (ECM) is an alternative method to machine AMCs. Based on anodic dissolution, ECM has a slight influence on the work piece material structure and is independent of material strength and hardness. So the microstructure of the work piece remains unaffected. One method of ECM is electrochemical machining with continuous electrolytic free jet (Jet-ECM). Hereby the electrochemical removal is localized by the geometry of the electrolyte jet. By moving the electrolyte jet micro-structures and microgeometries can be generated quickly and flexibly in metallic parts [1]. Another advantage of Jet-ECM is the low consumption of electrolyte which allows an easy and inexpensive change of electrolyte for investigations with different types of electrolyte. In this study AMCs reinforced with different amounts of SiC-particles are machined with two pH-neutral electrolytes using Jet-ECM. The results provide information about the suitability of the selected electrolytes for the machining of AMCs. In addition, the influence of the particle content on the electrochemical removal result will be evaluated.

  14. Effect of Thermal Cycling on the Tensile Behavior of Polymer Composites Reinforced by Basalt and Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Khalili, S. Mohammad Reza; Najafi, Moslem; Eslami-Farsani, Reza

    2017-01-01

    The aim of the present work was to investigate the effect of thermal cycling on the tensile behavior of three types of polymer-matrix composites — a phenolic resin reinforced with woven basalt fibers, woven carbon fibers, and hybrid basalt and carbon fibers — in an ambient environment. For this purpose, tensile tests were performed on specimens previously subjected to a certain number of thermal cycles. The ultimate tensile strength of the specimen reinforced with woven basalt fibers had by 5% after thermal cycling, but the strength of the specimen with woven carbon fibers had reduced to a value by 11% higher than that before thermal cycling.

  15. Co-axial capillaries microfluidic device for synthesizing size- and morphology-controlled polymer core-polymer shell particles.

    PubMed

    Chang, Zhenqi; Serra, Christophe A; Bouquey, Michel; Prat, Laurent; Hadziioannou, Georges

    2009-10-21

    An easy assembling-disassembling co-axial capillaries microfluidic device was built up for the production of double droplets. Uniform polymer core-polymer shell particles were synthesized by polymerizing the two immiscible monomer phases composing the double droplet. Thus poly(acrylamide) core-poly(tri(propylene glycol) diacrylate) shell particles with controlled core diameter and shell thickness were simply obtained by adjusting operating parameters. An empirical law was extracted from experiments to predict core and shell sizes. Additionally uniform and predictable non-spherical polymer objects were also prepared without adding shape-formation procedures in the experimental device. An empirical equation for describing the lengths of rod-like polymer particles is also presented.

  16. Effects of the Amount and Shape of Carbon Fiber-Reinforced Polymer Strengthening Elements on the Ductile Behavior of Reinforced Concrete Beams

    NASA Astrophysics Data System (ADS)

    Hong, Sungnam

    2014-09-01

    A series of beam tests were performed to evaluate the ductility of reinforced concrete (RC) beams strengthened with carbon-fiber-reinforced polymer (CFRP) elements. A total of nine RC beams were produced and loaded up to failure in three-point bending under deflection control. In addition, the amount and shape of the CFRP elements (plates/sheets) were considered as the key test variables. Test results revealed that the strengthening with CFRP elements in the width direction was more effective than the strengthening across their height. The energy method used in an analysis showed that the energy ratio of the beams strengthened with CFRP plates were half or less than half of the energy ratio of the beams strengthened with CFRP sheets. In addition, the ductility of the beams decreased as the strengthening ratio of the CFRP elements increased.

  17. Electron microscopy structure study of laser-clad TiC-Ni particle-reinforced coating

    SciTech Connect

    Ouyang, J.H.; Li, X.; Lei, T.C.

    2000-04-01

    The microstructure of a laser-clad TiC-Ni particle-reinforced coating on 1045 steel was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ion microprobe mass spectroscopy (IMMS). The microstructural constituents of the clad layers (CLs) were analyzed to be TiC particles, {gamma}-Ni primary dendrites, and interdendritic eutectics of {gamma}{sub E}-Ni plus M{sub 23}(CB){sub 6} and M{sub 6}(CB) carboborides. Three growth mechanisms of the original TiC particles were found: (1) stepped lateral growth at the edges, (2) radiated and cylindrically coupled growth at the edges, and (3) bridging growth of the clustered particles. Ordered and modulated structures were found in the original TiC particles. In addition to the original TiC particles, fine TiC particles precipitated from the liquid phase and {gamma}-Ni solid solution during laser cladding. The microstructures of the bonding zones (BZs) were intimately associated with laser processing parameters. The BZs of the clad coatings can be categorized into three types according to the combination of the CL with heat-affected zone (HAZ): (1) straight interface combination, (2) zigzag connection, and (3) combination by partial melting of prior austenitic grain boundaries of the substrate. The microstructural evolution of the CLs was discussed. The formation and phase transformation models of the BZs were proposed.

  18. Precipitation Sequence of a SiC Particle Reinforced Al-Mg-Si Alloy Composite

    NASA Astrophysics Data System (ADS)

    Shen, Rujuan; Wang, Yihan; Guo, Baisong; Song, Min

    2016-11-01

    In this study, the precipitation sequence of a 5 vol.% SiC particles reinforced Al-1.12 wt.%Mg-0.77 wt.%Si alloy composite fabricated by traditional powder metallurgy method was investigated by transmission electron microscopy and hardness measurements. The results indicated that the addition of SiC reinforcements not only suppresses the initial aging stage but also influences the subsequent precipitates. The precipitation sequence of the composite aged at 175 °C can be described as: Guinier-Preston (G.P.) zone → β″ → β' → B', which was confirmed by high-resolution transmission electron microscopy. This work might provide the guidance for the design and fabrication of hardenable automobile body sheet by Al-based composites with enhanced mechanical properties.

  19. An analytical model for particulate reinforced composites (PRCs) taking account of particle debonding and matrix cracking

    NASA Astrophysics Data System (ADS)

    Jiang, Yunpeng

    2016-10-01

    In this work, a simple micromechanics-based model was developed to describe the overall stress-strain relations of particulate reinforced composites (PRCs), taking into account both particle debonding and matrix cracking damage. Based on the secant homogenization frame, the effective compliance tensor could be firstly given for the perfect composites without any damage. The progressive interface debonding damage is controlled by a Weibull probability function, and then the volume fraction of detached particles is involved in the equivalent compliance tensor to account for the impact of particle debonding. The matrix cracking was introduced in the present model to embody the stress softening stage in the deformation of PRCs. The analytical model was firstly verified by comparing with the corresponding experiment, and then parameter analyses were conducted. This modeling will shed some light on optimizing the microstructures in effectively improving the mechanical behaviors of PRCs.

  20. Acoustic emission during fatigue crack propagation in SiC particle reinforced Al matrix composites

    SciTech Connect

    Niklas, A.; Froyen, L.; Wevers, M.; Delaey, L.

    1995-12-01

    The acoustic emission (AE) behavior during fatigue propagation in aluminum 6061 and aluminum 6061 matrix composites containing 5, 10, and 20 wt pct SiC particle reinforcement was investigated under tension-tension fatigue loading. The purpose of this investigation was to monitor fatigue crack propagation by the AE technique and to identify the source(s) of AE. Most of the AEs detected were observed at the top of the load cycles. The cumulative number of AE events was found to correspond closely to the fatigue crack growth and to increase with increasing SiC content. Fractographic studies revealed an increasing number of fractured particles and to a lesser extent decohered particles on the fatigue fracture surface as the crack propagation rate (e.g., {Delta}K) or the SiC content was increased.

  1. Coating of zinc ferrite particles with a conducting polymer, polyaniline.

    PubMed

    Stejskal, Jaroslav; Trchová, Miroslava; Brodinová, Jitka; Kalenda, Petr; Fedorova, Svetlana V; Prokes, Jan; Zemek, Josef

    2006-06-01

    Particles of zinc ferrite, ZnOFe2O3, were coated with polyaniline (PANI) phosphate during the in situ polymerization of aniline in an aqueous solution of phosphoric acid. The PANI-ferrite composites were characterized by FTIR spectroscopy. X-ray photoelectron spectroscopy was used to determine the degree of coating with a conducting polymer. Even a low content of PANI, 1.4 wt%, resulted in the 45% coating of the particles' surface. On the other hand, even at high PANI content, the coating of ferrite surface did not exceeded 90%. This is explained by the clustering of hydrophobic aniline oligomers at the hydrophilic ferrite surface and the consequent irregular PANI coating. The conductivity increased from 2 x 10(-9) to 6.5 S cm(-1) with increasing fraction of PANI phosphate in the composite. The percolation threshold was located at 3-4 vol% of the conducting component. In the absence of any acid, a conducting product, 1.4 x 10(-2) Scm(-1), was also obtained. As the concentration of phosphoric acid increased to 3 M, the conductivity of the composites reached 1.8 S cm(-1) at 10-14 wt% of PANI. The ferrite alone can act as an oxidant for aniline; a product having a conductivity 0.11 S cm(-1) was obtained after a one-month immersion of ferrite in an acidic solution of aniline.

  2. Buckling of Carbon Nanotube-Reinforced Polymer Laminated Composite Materials Subjected to Axial Compression and Shear Loadings

    NASA Technical Reports Server (NTRS)

    Riddick, J. C.; Gates, T. S.; Frankland, S.-J. V.

    2005-01-01

    A multi-scale method to predict the stiffness and stability properties of carbon nanotube-reinforced laminates has been developed. This method is used in the prediction of the buckling behavior of laminated carbon nanotube-polyethylene composites formed by stacking layers of carbon nanotube-reinforced polymer with the nanotube alignment axes of each layer oriented in different directions. Linking of intrinsic, nanoscale-material definitions to finite scale-structural properties is achieved via a hierarchical approach in which the elastic properties of the reinforced layers are predicted by an equivalent continuum modeling technique. Solutions for infinitely long symmetrically laminated nanotube-reinforced laminates with simply-supported or clamped edges subjected to axial compression and shear loadings are presented. The study focuses on the influence of nanotube volume fraction, length, orientation, and functionalization on finite-scale laminate response. Results indicate that for the selected laminate configurations considered in this study, angle-ply laminates composed of aligned, non-functionalized carbon nanotube-reinforced lamina exhibit the greatest buckling resistance with 1% nanotube volume fraction of 450 nm uniformly-distributed carbon nanotubes. In addition, hybrid laminates were considered by varying either the volume fraction or nanotube length through-the-thickness of a quasi-isotropic laminate. The ratio of buckling load-to-nanotube weight percent for the hybrid laminates considered indicate the potential for increasing the buckling efficiency of nanotube-reinforced laminates by optimizing nanotube size and proportion with respect to laminate configuration.

  3. Fabrication of elastomeric stamps with polymer-reinforced sidewalls via chemically selective vapor deposition polymerization of poly(p-xylylene)

    NASA Astrophysics Data System (ADS)

    Suh, Kahp Y.; Langer, Robert; Lahann, Jörg

    2003-11-01

    We report on the preparation of polydimethylsiloxane stamps with selectively grown polymer sidewalls by chemical vapor deposition polymerization of poly(p-xylylene). Using a thin iron layer as an inhibitor, the deposition occurs only on the sidewalls of the features in relief, resulting in a polymer-reinforced stamp. The wetting properties of stamps can be restored after removing the thin iron layer with an acidic solution, which has been verified by pattern transfer to an underlying substrate using molding and microcontact printing.

  4. Three-Dimensional Nanoporous Cellulose Gels as a Flexible Reinforcement Matrix for Polymer Nanocomposites.

    PubMed

    Shi, Zhuqun; Huang, Junchao; Liu, Chuanjun; Ding, Beibei; Kuga, Shigenori; Cai, Jie; Zhang, Lina

    2015-10-21

    With the world's focus on utilization of sustainable natural resources, the conversion of wood and plant fibers into cellulose nanowhiskers/nanofibers is essential for application of cellulose in polymer nanocomposites. Here, we present a novel fabrication method of polymer nanocomposites by in-situ polymerization of monomers in three-dimensionally nanoporous cellulose gels (NCG) prepared from aqueous alkali hydroxide/urea solution. The NCG have interconnected nanofibrillar cellulose network structure, resulting in high mechanical strength and size stability. Polymerization of the monomer gave P(MMA/BMA)/NCG, P(MMA/BA)/NCG nanocomposites with a volume fraction of NCG ranging from 15% to 78%. SEM, TEM, and XRD analyses show that the NCG are finely distributed and preserved well in the nanocomposites after polymerization. DMA analysis demonstrates a significant improvement in tensile storage modulus E' above the glass transition temperature; for instance, at 95 °C, E' is increased by over 4 orders of magnitude from 0.03 MPa of the P(MMA/BMA) up to 350 MPa of nanocomposites containing 15% v/v NCG. This reinforcement effect can be explained by the percolation model. The nanocomposites also show remarkable improvement in solvent resistance (swelling ratio of 1.3-2.2 in chloroform, acetone, and toluene), thermal stability (do not melt or decompose up to 300 °C), and low coefficients of thermal expansion (in-plane CTE of 15 ppm·K(-1)). These nanocomposites will have great promising applications in flexible display, packing, biomedical implants, and many others.

  5. Effect of tool wear on quality of carbon fiber reinforced polymer laminate during edge trimming

    NASA Astrophysics Data System (ADS)

    Hamedanianpour, Hossein

    Polymer matrix composites, especially carbon fiber reinforced polymers (CFRPs) are vastly used in different high technology industries, including aerospace, automotive and wind energy. Normally, when CFRPs are cured to near net shape, finishing operations such as trimming, milling or drilling are used to remove excess materials. The quality of these finishing operations is highly essential at the level of final assembly. The present study aims to study the effect of cutting tool wear on the resulting quality for the trimming process of high performance CFRP laminates, in the aerospace field. In terms of quality parameters, the study focuses on surface roughness and material integrity damages (uncut fibers, fiber pullout, delamination or thermal damage of the matrix), which could jeopardize the mechanical performance of the components. In this study, a 3/8 inch diameter CVD diamond coated carbide tool with six flutes was used to trim 24-ply carbon fiber laminates. Cutting speeds ranging from 200 m/min to 400 m/min and feed rates ranging from 0.3048 mm/rev to 0.4064 mm/rev were used in the experiments. The results obtained using a scanning electron microscope (SEM) showed increasing defect rates with an increase in tool wear. The worst surface integrity, including matrix cracking, fiber pull-out and empty holes, was also observed for plies oriented at -45° degrees. For the surface finish, it was observed that an increase in tool wear resulted in a decrease in surface roughness. Regarding tool wear, a lower rate was observed at lower feed rates and higher cutting speeds, while a higher tool wear rate was observed at intermediate values of our feed rate and cutting speed ranges.

  6. Nanocomposites with Ca and PO4 release: Effects of reinforcement, dicalcium phosphate particle size and silanization

    PubMed Central

    Xu, Hockin H. K.; Weir, Michael D.; Sun, Limin

    2009-01-01

    Objectives Nano-particles of dicalcium phosphate anhydrous (DCPA) were synthesized in our laboratory for the first time and incorporated into a dental resin. Our goal was to develop a mechanically strong dental composite that has Ca and PO4 ion release to combat tooth caries, and to investigate the effects of whisker reinforcement, DCPA particle size and silanization. Methods DCPA nano-particles and two larger DCPA particles were used with nano-silica-fused whiskers as fillers in a resin matrix. Composite mechanical properties were measured via three-point flexure, and the release of Ca and PO4 ions were measured vs. time. Results Using DCPA nano-particles with a diameter of 112 nm, the composite at a DCPA:whisker mass ratio of 1:1 had a flexural strength (mean ± sd; n = 5) of (112 ± 17) MPa, not significantly different from (112 ± 14) MPa of a commercial non-releasing composite; both were higher than (29 ± 7) MPa for the composite at DCPA:whisker of 1:0 (p < 0.05). The composite with DCPA particle size of 112 nm released Ca to a concentration of 0.85 mmol/L and PO4 of 3.48 mmol/L, higher than Ca of 0.67 mmol/L and PO4 of 1.11 mmol/L using DCPA with 12 μm particle size (p < 0.05). Silanization of DCPA increased the composite strength at DCPA:whisker of 1:0 compared to that without silanization, but decreased the Ca and PO4 release (p < 0.05). Increasing the DCPA particle surface area increased the Ca and PO4 release. Significance Decreasing the DCPA particle size increased the Ca and PO4 release; whisker reinforcement increased the composite strength by 2 to 3 fold. The nano DCPA-whisker composites, with high strength and Ca and PO4 release, may provide the needed, unique combination of stress-bearing and caries-inhibiting capabilities. PMID:17339048

  7. Crystallization kinetics and thermal resistance of bamboo fiber reinforced biodegradable polymer composites

    NASA Astrophysics Data System (ADS)

    Thumsorn, S.; Srisawat, N.; On, J. Wong; Pivsa-Art, S.; Hamada, H.

    2014-05-01

    Bamboo fiber reinforced biodegradable polymer composites were prepared in this study. Biodegradable poly(butylene succinate) (PBS) was blended with bamboo fiber in a twin screw extruder with varied bamboo content from 20-0wt%. PBS/bamboo fiber composites were fabricated by compression molding process. The effect of bamboo fiber contents on properties of the composites was investigated. Non-isothermal crystallization kinetic study of the composites was investigated based on Avrami equation. The kinetic parameters indicated that bamboo fiber acted as heterogeneous nucleation and enhanced crystallinity of the composites. Bamboo fiber was well dispersed on PBS matrix and good adhered with the matrix. Tensile strength of the composites slightly deceased with adding bamboo fiber. However, tensile modulus and impact strength of the composites increased when increasing bamboo fiber contents. It can be noted that bamboo fiber promoted crystallization and crystallinity of PBS in the composites. Therefore, the composites were better in impact load transferring than neat PBS, which exhibited improving on impact performance of the composites.

  8. Active vibration control of a smart pultruded fiber-reinforced polymer I-beam

    NASA Astrophysics Data System (ADS)

    Song, G.; Qiao, P.; Sethi, V.; Prasad, A.

    2004-08-01

    Advanced and innovative materials and structures are increasingly used in civil infrastructure applications. By combining the advantages of composites and smart sensors and actuators, active or smart composite structures can be created and be efficiently adopted in practical structural applications. This paper presents results on active vibration control of pultruded fiber-reinforced polymer (FRP) composite thin-walled I-beams using smart sensors and actuators. The FRP I-beams are made of E-glass fibers and polyester resins. The FRP I-beam is in a cantilevered configuration. The PZT (lead zirconate titanate) type of piezoelectric ceramic patches are used as smart sensors and actuators. These patches are surface bonded near the cantilevered end of the I-beam. Utilizing results from modal analyses and experimental modal testing, several active vibration control methods, such as position feedback control, strain rate feedback control and lead compensation, are investigated. Experimental results demonstrate that the proposed methods achieve effective vibration control of FRP I-beams. For instance, the modal damping ratio of the strong direction first bending mode increases by more than 1000% with positive position feedback control.

  9. Active vibration control of a smart pultruded fiber-reinforced polymer I-beam

    NASA Astrophysics Data System (ADS)

    Song, Gangbing; Qiao, Pizhong; Sethi, Vineet; Prasad, A.

    2002-06-01

    Advanced and innovative materials and structures are increasingly used in civil infrastructure applications. By combining the advantages of composites and smart sensors and actuators, active or smart composite structures can be created and be efficiently adopted in practical structural applications. This paper presents results of active vibration control of a pultruded fiber-reinforced polymer (FRP) composites thin-walled I-beams using smart sensors and actuators. The FRP I-beams are made of E-glass fibers and polyester resins. The FRP I-beam is in a cantilevered configuration. PZT (Lead zirconate titanate) type of piezoelectric ceramic patches are used as smart sensors and actuators. These patches are surface-bonded near the cantilevered end of the I-beam. Utilizing results from modal analyses and experimental modal testing, several active vibration control methods, such as position feedback control, strain rate feedback control and lead compensator, are investigated. Experimental results demonstrate that the proposed methods achieve effective vibration control of FRP I-beams. For instance, the modal damping ratio of the strong direction first bending mode increases by more than 1000 percent with a positive position feedback control.

  10. Characterization and analysis of carbon fibre-reinforced polymer composite laminates with embedded circular vasculature.

    PubMed

    Huang, C-Y; Trask, R S; Bond, I P

    2010-08-06

    A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension.

  11. Research on the Mechanical Properties of a Glass Fiber Reinforced Polymer-Steel Combined Truss Structure

    PubMed Central

    Liu, Pengfei; Zhao, Qilin; Li, Fei; Liu, Jinchun; Chen, Haosen

    2014-01-01

    An assembled plane truss structure used for vehicle loading is designed and manufactured. In the truss, the glass fiber reinforced polymer (GFRP) tube and the steel joint are connected by a new technology featuring a pretightened tooth connection. The detailed description for the rod and node design is introduced in this paper, and a typical truss panel is fabricated. Under natural conditions, the short-term load test and long-term mechanical performance test for one year are performed to analyze its performance and conduct a comparative analysis for a reasonable FEM model. The study shows that the design and fabrication for the node of an assembled truss panel are convenient, safe, and reliable; because of the creep control design of the rods, not only does the short-term structural stiffness meet the design requirement but also the long-term creep deformation tends towards stability. In addition, no significant change is found in the elastic modules, so this structure can be applied in actual engineering. Although the safety factor for the strength of the composite rods is very large, it has a lightweight advantage over the steel truss for the low density of GFRP. In the FEM model, simplifying the node as a hinge connection relatively conforms to the actual status. PMID:25247203

  12. The strong diamagnetic behaviour of unidirectional carbon fiber reinforced polymer laminates

    NASA Astrophysics Data System (ADS)

    Galehdar, A.; Nicholson, K. J.; Callus, P. J.; Rowe, W. S. T.; John, S.; Wang, C. H.; Ghorbani, K.

    2012-12-01

    Carbon fibers are finite conductors with a weak diamagnetic response in a static magnetic field. When illuminated with a high-frequency alternating electromagnetic wave such that the skin depth is greater than the fiber diameter, carbon-fiber composites are shown to exhibit a strong dynamic diamagnetic response. The magnetic susceptibility (χm) is controlled by the polarization angle (θ), which is the angle between the incident electric field and conductor direction. A closed form solution for this behaviour was derived using Maxwell's equations and an understanding of the induced conductor currents. The equation was verified using simulation and free space "wall" and waveguide measurements on unidirectional IM7/977-3 carbon fiber reinforced polymer laminates. The measured responses ranged from non-magnetic at θ = 90°, χm = 0, up to strongly diamagnetic at θ = 30°, χm = -0.75, over the 8-18 GHz bandwidth. The experimental results are in good agreement with theoretical predictions and computational simulations.

  13. Research on the mechanical properties of a glass fiber reinforced polymer-steel combined truss structure.

    PubMed

    Liu, Pengfei; Zhao, Qilin; Li, Fei; Liu, Jinchun; Chen, Haosen

    2014-01-01

    An assembled plane truss structure used for vehicle loading is designed and manufactured. In the truss, the glass fiber reinforced polymer (GFRP) tube and the steel joint are connected by a new technology featuring a pretightened tooth connection. The detailed description for the rod and node design is introduced in this paper, and a typical truss panel is fabricated. Under natural conditions, the short-term load test and long-term mechanical performance test for one year are performed to analyze its performance and conduct a comparative analysis for a reasonable FEM model. The study shows that the design and fabrication for the node of an assembled truss panel are convenient, safe, and reliable; because of the creep control design of the rods, not only does the short-term structural stiffness meet the design requirement but also the long-term creep deformation tends towards stability. In addition, no significant change is found in the elastic modules, so this structure can be applied in actual engineering. Although the safety factor for the strength of the composite rods is very large, it has a lightweight advantage over the steel truss for the low density of GFRP. In the FEM model, simplifying the node as a hinge connection relatively conforms to the actual status.

  14. Noncontact detection of Teflon inclusions in glass-fiber-reinforced polymer composites using terahertz imaging.

    PubMed

    Zhang, Jin; Wang, Jie; Han, Xiaohui; Cui, Hong-Liang; Shi, Changcheng; Zhang, Jinbo; Shen, Yan

    2016-12-20

    We employed terahertz (THz) time-domain spectroscopy (TDS) imaging technology, a new nondestructive testing method, to detect the inclusions of glass-fiber-reinforced polymer (GFRP) composites. The refractive index and absorption coefficient of two types of GFRP composites (epoxy GFRP composites and polyester GFRP composites) were first extracted, and GFRP composites with Teflon inclusions were examined, including an epoxy GFRP solid panel with a smaller Teflon inclusion hidden behind a larger Teflon inclusion, and polyester GFRP solid panels with Teflon inclusions of various sizes, at different depths. It was experimentally demonstrated that THz TDS imaging technology could clearly detect a smaller inclusion hidden behind a larger inclusion. When the reflected THz pulse from the inclusion did not overlap with that from the front surface of the sample, removal of the latter before Fourier transform was shown to be helpful in imaging the inclusions. With sufficiently strong incident THz radiation, inclusion insertion depth had little impact on the ability of the THz wave to detect inclusions. However, as the thickness of the inclusion became thinner, the inclusion detection ability of the THz wave deteriorated. In addition, with a combination of reflected C-scan imaging and B-scan imaging using the reflected time-domain waveform, both the lateral sizes and locations of the inclusions and the depths and thicknesses of the inclusions were clearly ascertained.

  15. Modeling continuous-fiber reinforced polymer composites for exploration of damage tolerant concepts

    NASA Astrophysics Data System (ADS)

    Matthews, Peter J.

    This work aims to improve the predictive capability for fiber-reinforced polymer matrix composite laminates using the finite element method. A new tool for modeling composite damage was developed which considers important modes of failure. Well-known micromechanical models were implemented to predict material values for material systems of interest to aerospace applications. These generated material values served as input to intralaminar and interlaminar damage models. A three-dimensional in-plane damage material model was implemented and behavior verified. Deficiencies in current state-of-the-art interlaminar capabilities were explored using the virtual crack closure technique and the cohesive zone model. A user-defined cohesive element was implemented to discover the importance of traction-separation material constitutive behavior. A novel method for correlation of traction-separation parameters was created. This new damage modeling tool was used for evaluation of novel material systems to improve damage tolerance. Classical laminate plate theory was used in a full-factorial study of layerwise-hybrid laminates. Filament-wound laminated composite cylindrical shells were subjected to quasi-static loading to validate the finite element computational composite damage model. The new tool for modeling provides sufficient accuracy and generality for use on a wide-range of problems.

  16. Recycling of woven carbon-fibre-reinforced polymer composites using supercritical water.

    PubMed

    Knight, Chase C; Zeng, Changchun; Zhang, Chuck; Wang, Ben

    2012-01-01

    Over the past few years, there has been great deal of interest in recycling carbon-fibre-reinforced polymer composites. One method that has shown promising results involves the use of supercritical fluids to achieve separation between matrix and fibres by effectively degrading the resin into lower molecular weight compounds. In addition, the solvents used are environmentally benign and can also be recovered and reused. In this study, supercritical water with 0.05 M KOH as the catalyst was used for the recycling of an aerospace-grade high-performance epoxy carbon fibre composite (Hexcel 8552/IM7). The morphology of the reclaimed fibres was observed by scanning electron microscopy, and the tensile properties of the fibres were measured by single filament testing. The effects of processing time on the resin elimination efficiency and fibre property retention were investigated. With the process developed in this research, as much as 99.2 wt% resin elimination was achieved, resulting in the recovery of clean, undamaged fibres. The reclaimed fibres retained the original tensile strength. The feasibility of recycling multiple layer composites was also explored.

  17. Failure of a carbon fiber-reinforced polymer implant used for transforaminal lumbar interbody fusion.

    PubMed

    Sardar, Zeeshan; Jarzem, Peter

    2013-12-01

    Lumbar interbody fusion is a common procedure owing to the high prevalence of degenerative spinal disorders. During such procedures, carbon fiber-reinforced polymer (CFRP) cages are frequently utilized to fill the void created between adjacent vertebral bodies, to provide mechanical stability, and to carry graft material. Failure of such implants can lead to significant morbidity. We discuss the possible causes leading to the failure of a CFRP cage in a patient with rheumatoid arthritis. Review of a 49-year-old woman who underwent revision anterior lumbar interbody fusion 2 years after posterior instrumentation and transforaminal lumbar interbody fusion at L4-L5 and L5-S1. The patient developed pseudarthrosis at the two previously fused levels with failure of the posterior instrumentation. Revision surgery reveled failure with fragmentation of the CFRP cage at the L5-S1 level. CFRP implants can break if mechanical instability or nonunion occurs in the spinal segments, thus emphasizing the need for optimizing medical management and meticulous surgical technique in achieving stability.

  18. Characterization and analysis of carbon fibre-reinforced polymer composite laminates with embedded circular vasculature

    PubMed Central

    Huang, C.-Y.; Trask, R. S.; Bond, I. P.

    2010-01-01

    A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension. PMID:20150337

  19. High Power Laser Cutting of Fiber Reinforced Thermoplastic Polymers with cw- and Pulsed Lasers

    NASA Astrophysics Data System (ADS)

    Schneider, F.; Wolf, N.; Petring, D.

    Glass fiber and carbon fiber reinforced polymers with thermoplastic matrix enable high volume production with short cycle times. Cutting and trimming operations in these production chains require the use of high average laser power for an efficient cutting speed, but employment of high laser power runs the risk to induce a wide heat affected zone (HAZ). This paper deals with investigations with cw and ns-pulsed CO2-laser radiation in the kilowatt range in single-pass and multiple-pass processes. Using multi-pass processing at high processing speeds of 100 m/min and above a reduced heat affected zone in the range of 100 μm to 200 μm could be achieved by the ns-pulsed radiation. With cw radiation at the same average power of 1 kW however, the HAZ was 300-400 μm. Also employing ns-pulses in the kW-range average power leads to heat accumulation in the material. Small HAZ were obtained with sufficient break times between subsequent passes.

  20. Failure of a Carbon Fiber–Reinforced Polymer Implant Used for Transforaminal Lumbar Interbody Fusion

    PubMed Central

    Sardar, Zeeshan; Jarzem, Peter

    2013-01-01

    Lumbar interbody fusion is a common procedure owing to the high prevalence of degenerative spinal disorders. During such procedures, carbon fiber–reinforced polymer (CFRP) cages are frequently utilized to fill the void created between adjacent vertebral bodies, to provide mechanical stability, and to carry graft material. Failure of such implants can lead to significant morbidity. We discuss the possible causes leading to the failure of a CFRP cage in a patient with rheumatoid arthritis. Review of a 49-year-old woman who underwent revision anterior lumbar interbody fusion 2 years after posterior instrumentation and transforaminal lumbar interbody fusion at L4–L5 and L5–S1. The patient developed pseudarthrosis at the two previously fused levels with failure of the posterior instrumentation. Revision surgery reveled failure with fragmentation of the CFRP cage at the L5–S1 level. CFRP implants can break if mechanical instability or nonunion occurs in the spinal segments, thus emphasizing the need for optimizing medical management and meticulous surgical technique in achieving stability. PMID:24436878

  1. A Numerical Homogenization Scheme for Glass Particle-Toughened Polymers Under Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Karamnejad, Amin; Ahmed, Awais; Sluys, Lambertus Johannes

    A numerical homogenization scheme is presented to model glass particle-toughened polymer materials under dynamic loading. A constitutive law is developed for the polymer material and validated by comparing the results to experimental test data. A similar constitutive law as that of the polymer material with unknown material parameters is assumed for the glass particle-toughened polymer. A homogenization scheme is used to determine the unknown material parameters from the boundary value problem (BVP) of a representative volume element. Unlike the standard computational homogenization scheme, the proposed numerical homogenization scheme can be used after localization occurs in the material. The proposed multiscale model is then verified against direct numerical simulation.

  2. Observation of the electrorheological effect of silicone oil/polymer particles suspension

    SciTech Connect

    Yatsuzuka, Kyoko; Miura, Keiji; Kuramoto, Noriyuki; Asano, Kazutoshi

    1995-05-01

    A liquid insulator that suspends small particles is one of the electrorheological fluids (ERF) whose apparent viscosity becomes larger under an electric field because of the formation of particle chains. Since many possible applications of ERF are expected, the development of a more practical ERF is required. The authors have investigated the ER effect of silicone oil in which small particles are suspended. Silica particles, silica particles coated by conductive polymer film, and polymer particles (microcrystalline cellulose), with a diameter between 5 {approximately} 100 {mu}m, are investigated in order to clarify the difference between suspending materials. To measure the ER effect, a rotational viscometer was constructed. It became clear that the shear stress for cellulose particles is much stronger than that for other particles because of its peculiar particle chain formation due to the particle shape.

  3. Vacuum brazing of high volume fraction SiC particles reinforced aluminum matrix composites

    NASA Astrophysics Data System (ADS)

    Cheng, Dongfeng; Niu, Jitai; Gao, Zeng; Wang, Peng

    2015-03-01

    This experiment chooses A356 aluminum matrix composites containing 55% SiC particle reinforcing phase as the parent metal and Al-Si-Cu-Zn-Ni alloy metal as the filler metal. The brazing process is carried out in vacuum brazing furnace at the temperature of 550°C and 560°C for 3 min, respectively. The interfacial microstructures and fracture surfaces are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy spectrum analysis (EDS). The result shows that adequacy of element diffusion are superior when brazing at 560°C, because of higher activity and liquidity. Dislocations and twins are observed at the interface between filler and composite due to the different expansion coefficient of the aluminum alloy matrix and SiC particles. The fracture analysis shows that the brittle fracture mainly located at interface of filler and composites.

  4. Surface-selective laser sintering of thermolabile polymer particles using water as heating sensitizer

    SciTech Connect

    Antonov, E N; Krotova, L I; Minaev, N V; Minaeva, S A; Mironov, A V; Popov, V K; Bagratashvili, V N

    2015-11-30

    We report the implementation of a novel scheme for surface-selective laser sintering (SSLS) of polymer particles, based on using water as a sensitizer of laser heating and sintering of particles as well as laser radiation at a wavelength of 1.94 μm, corresponding to the strong absorption band of water. A method of sintering powders of poly(lactide-co-glycolide), a hydrophobic bioresorbable polymer, after modifying its surface with an aqueous solution of hyaluronic acid is developed. The sintering thresholds for wetted polymer are by 3 – 4 times lower than those for sintering in air. The presence of water restricts the temperature of the heated polymer, preventing its thermal destruction. Polymer matrices with a developed porous structure are obtained. The proposed SSLS method can be applied to produce bioresorbable polymer matrices for tissue engineering. (interaction of laser radiation with matter. laser plasma)

  5. Surface-selective laser sintering of thermolabile polymer particles using water as heating sensitizer

    NASA Astrophysics Data System (ADS)

    Antonov, E. N.; Krotova, L. I.; Minaev, N. V.; Minaeva, S. A.; Mironov, A. V.; Popov, V. K.; Bagratashvili, V. N.

    2015-11-01

    We report the implementation of a novel scheme for surface-selective laser sintering (SSLS) of polymer particles, based on using water as a sensitizer of laser heating and sintering of particles as well as laser radiation at a wavelength of 1.94 μm, corresponding to the strong absorption band of water. A method of sintering powders of poly(lactide-co-glycolide), a hydrophobic bioresorbable polymer, after modifying its surface with an aqueous solution of hyaluronic acid is developed. The sintering thresholds for wetted polymer are by 3 - 4 times lower than those for sintering in air. The presence of water restricts the temperature of the heated polymer, preventing its thermal destruction. Polymer matrices with a developed porous structure are obtained. The proposed SSLS method can be applied to produce bioresorbable polymer matrices for tissue engineering.

  6. The erosion performance of particle reinforced metal matrix composite coatings produced by co-deposition cold gas dynamic spraying

    NASA Astrophysics Data System (ADS)

    Peat, Tom; Galloway, Alexander; Toumpis, Athanasios; McNutt, Philip; Iqbal, Naveed

    2017-02-01

    This work reports on the erosion performance of three particle reinforced metal matrix composite coatings, co-deposited with an aluminium binder via cold-gas dynamic spraying. The deposition of ceramic particles is difficult to achieve with typical cold spray techniques due to the absence of particle deformation. This issue has been overcome in the present study by simultaneously spraying the reinforcing particles with a ductile metallic binder which has led to an increased level of ceramic/cermet particles deposited on the substrate with thick (>400 μm) coatings produced. The aim of this investigation was to evaluate the erosion performance of the co-deposited coatings within a slurry environment. The study also incorporated standard metallographic characterisation techniques to evaluate the distribution of reinforcing particles within the aluminium matrix. All coatings exhibited poorer erosion performance than the uncoated material, both in terms of volume loss and mass loss. The Al2O3 reinforced coating sustained the greatest amount of damage following exposure to the slurry and recorded the greatest volume loss (approx. 2.8 mm3) out of all of the examined coatings. Despite the poor erosion performance, the WC-CoCr reinforced coating demonstrated a considerable hardness increase over the as-received AA5083 (approx. 400%) and also exhibited the smallest free space length between adjacent particles. The findings of this study reveal that the removal of the AA5083 matrix by the impinging silicon carbide particles acts as the primary wear mechanism leading to the degradation of the coating. Analysis of the wear scar has demonstrated that the damage to the soft matrix alloy takes the form of ploughing and scoring which subsequently exposes carbide/oxide particles to the impinging slurry.

  7. Quantitative Dependence of the Effective Modulus of Particle Reinforced Composites on Partially Debonding Damage

    NASA Astrophysics Data System (ADS)

    Jiang, Yunpeng; Tohgo, Keiichiro; Shimamura, Yoshinobu

    This paper is to study the impact of partially-debonding damage on the effective elasticity of particle reinforced composites (PRC). The particles would lose a part of load-carrying capacity after the interface partially-debonding happens. The damage degree is determined by damage variable parameters in terms of the debonding angle. Two sets of prevailing definitions of damage variable parameters, i.e. Zhao’s and Liu’s, are verified by finite element method (FEM), and the deficiencies of them are clearly demonstrated. To better characterize the effect of the partially-debonding damage, damage variables proposed by Wada are incorporated into an explicit micromechanics model to predict the effective properties of PRC. Finally, the accuracy and efficiency of the developed method are confirmed. In order to deeply understand the inherent damage mechanism, FEM is utilized to analyze the specific stress distribution in and around a debonded particle, and the evolution of the average particle stress with the debonding angle is revealed.

  8. Development of flash nanoprecipitation as a scalable platform for production of hybrid polymer-inorganic Janus particles

    NASA Astrophysics Data System (ADS)

    Lee, Victoria E.; Prud'Homme, Robert K.; Priestley, Rodney D.

    Polymer Janus particles, containing two or more distinct domains, can act as supports for inorganic nanoparticles, stabilizing them against aggregation and templating anisotropic functionalization of the microparticles. This anisotropy can be advantageous for applications such as biofuel upgrading, bionanosensors, and responsive materials. Here, we introduce flash nanoprecipitation (FNP) as a scalable, fast process to create hybrid polymer-inorganic Janus particles with control of particle size and anisotropy. During FNP, polymer Janus particles form by rapid intermixing of a polymer solution with a poor solvent, inducing polymer precipitation and phase separation. Inorganic nanoparticles are then adsorbed selectively onto one domain of the polymer support by exploiting electrostatic interactions between the charged particles. By tuning polymer concentration and ratio in the feed stream, the particle size and anisotropy can be controlled. We further demonstrate that these hybrid particles can simultaneously stabilize emulsions and selectively catalyze the degradation of dye in one phase. With support from the Princeton Imaging Analysis Center.

  9. Particles from preformed polymers as carriers for drug delivery

    PubMed Central

    Miladi, K.; Ibraheem, D.; Iqbal, M.; Sfar, S.; Fessi, H.; Elaissari, A.

    2014-01-01

    Biodegradable and biocompatible polymers are widely used for the encapsulation of drug molecules. Various particulate carriers with different sizes and characteristics have been prepared by miscellaneous techniques. In this review, we reported the commonly used preformed polymer based techniques for the preparation of micro and nano-structured materials intended for drug encapsulation. A description of polymer-solvent interaction was provided. The most widely used polymers were reported and described and their related research studies were mentioned. Moreover, principles of each technique and its crucial operating conditions were described and discussed. Recent applications of all the reported techniques in drug delivery were also reviewed. PMID:26417241

  10. Laser surface forming of AlCoCrCuFeNi particle reinforced AZ91D matrix composites

    NASA Astrophysics Data System (ADS)

    Meng, Guanghui; Yue, T. M.; Lin, Xin; Yang, Haiou; Xie, Hui; Ding, Xu

    2015-07-01

    Traditionally, the laser melt injection (LMI) technique can only be used for forming ceramic particles reinforced metal matrix composites (MMCs) for enhancing surface properties of lightweight engineering materials. In this research, the LMI method was employed to form metal particles reinforced MMCs on AZ91D instead. This was viable because of the unique properties of the AlCoCrCuFeNi high-entropy alloy (HEA) metal particles used. The large difference in melting point between the HEA and the substrate material (AZ91D), and the limited reaction and the lack of fusion between the HEA and Mg have made it possible that a metal particles reinforced AZ91D composite material was produced. The reason of limited reaction was considered mainly due to the relatively high mixing enthalpy between the HEA constituent elements and Mg. Although there was some melting occurred at the particles surface with some solute segregation found in the vicinity close to the surface, intermetallic compounds were not observed. With regard to the wear resistance of the MMCs, it was found that when the volume fraction of the reinforcement phase, i.e. the HEA particles, reached about 0.4, the wear volume loss of the coating was only one-seventh of that of the substrate material.

  11. Active rigidization of carbon-fiber reinforced polymer composites for ultra-lightweight space structures

    NASA Astrophysics Data System (ADS)

    Sarles, Stephen A.; Leo, Donald J.

    2006-03-01

    An active approach for initiating rigidization in carbon-fiber reinforced polymer (CFRP) thermosets links controllable mechanical stiffening to inherent electrical resistivity. With direct applications toward the rigidization of ultra-lightweight, inflatable space structures, temperature-controlled resistive heating is used to create oncommand rigidization. As required by the on-orbit conditions in space, flexible, rigidizable structures demand stable and space-survivable materials that incorporate techniques for providing shape control and structural stiffening. Methods currently employed to achieve a mechanical hardening include many passive techniques: UV curing, sub-T g hardening, and hydro-gel evaporation. The benefits of a passive system (simplicity, energy efficiency) are offset by their inherent lack of control, which can lead to long curing times and weak spots due to uneven curing. In efforts to significantly reduce the transition time of the composite from a structurally-vulnerable state to a fully-rigidized shape and to increase control of the curing process, an active approach is taken. Specifically, temperature-controlled internal resistive heating initiates thermoset curing in a coated carbon fiber composite to form an electrically-controlled, thermally-activated material. Through controlled heating, this research examines how selective temperature control can be used to prescribe matrix consolidation and material rigidization on two different thermosetting resins, U-Nyte Set 201A and 201B. Feedback temperature control, based on a PID control algorithm, was applied to the process of resistive heating. Precise temperature tracking (less than 1.1°C RMS or +/-3.3% error) was achieved for controlled sample heating. Using samples of the thermoset-coated carbon-fiber tow, composite hardening through resistive heating occurred in 24 minutes and required roughly 1 W-hr/inch of electrical energy. The rigidized material was measured to be 14-21 times stiffer

  12. Nanostructured Carbon Nitride Polymer-Reinforced Electrolyte To Enable Dendrite-Suppressed Lithium Metal Batteries.

    PubMed

    Hu, Jiulin; Tian, Jing; Li, Chilin

    2017-04-05

    Lithium metal batteries (LMBs) containing S, O2, and fluoride cathodes are attracting increasing attention owing to their much higher energy density than that of Li-ion batteries. However, current limitation for the progress of LMBs mainly comes from the uncontrolled formation and growth of Li dendrites at the anode side. In order to suppress dendrite growth, exploring novel nanostructured electrolyte of high modulus without degradation of Li-electrolyte interface appears to be a potential solution. Here we propose a lightweight polymer-reinforced electrolyte based on graphitic carbon nitride (g-C3N4) mesoporous microspheres as electrolyte filler [bis(trifluoromethanesulfonimide) lithium salt/di(ethylene glycol) dimethyl ether mixed with g-C3N4, denoted as LiTFSI-DGM-C3N4] for the first time. This nanostructured electrolyte can effectively suppress lithium dendrite growth during cycling, benefiting from the high mechanical strength and nanosheet-built hierarchical structure of g-C3N4. The Li/Li symmetrical cell based on this slurrylike electrolyte enables long-term cycling of at least 120 cycles with a high capacity of 6 mA·h/cm(2) and small plating/stripping overpotential of ∼100 mV at a high current density of 2 mA/cm(2). g-C3N4 filling also enables a separator(Celgard)-free Li/FeS2 cell with at least 400 cycles. The 3D geometry of g-C3N4 shows advantages on interfacial resistance and Li plating/stripping stability compared to its 2D geometry.

  13. Dissipative particle dynamics simulations of polymer-protected nanoparticle self-assembly.

    PubMed

    Spaeth, Justin R; Kevrekidis, Ioannis G; Panagiotopoulos, Athanassios Z

    2011-11-14

    Dissipative particle dynamics simulations were used to study the effects of mixing time, solute solubility, solute and diblock copolymer concentrations, and copolymer block length on the rapid coprecipitation of polymer-protected nanoparticles. The simulations were aimed at modeling Flash NanoPrecipitation, a process in which hydrophobic solutes and amphiphilic block copolymers are dissolved in a water-miscible organic solvent and then rapidly mixed with water to produce composite nanoparticles. A previously developed model by Spaeth et al. [J. Chem. Phys. 134, 164902 (2011)] was used. The model was parameterized to reproduce equilibrium and transport properties of the solvent, hydrophobic solute, and diblock copolymer. Anti-solvent mixing was modeled using time-dependent solvent-solute and solvent-copolymer interactions. We find that particle size increases with mixing time, due to the difference in solute and polymer solubilities. Increasing the solubility of the solute leads to larger nanoparticles for unfavorable solute-polymer interactions and to smaller nanoparticles for favorable solute-polymer interactions. A decrease in overall solute and polymer concentration produces smaller nanoparticles, because the difference in the diffusion coefficients of a single polymer and of larger clusters becomes more important to their relative rates of collisions under more dilute conditions. An increase in the solute-polymer ratio produces larger nanoparticles, since a collection of large particles has less surface area than a collection of small particles with the same total volume. An increase in the hydrophilic block length of the polymer leads to smaller nanoparticles, due to an enhanced ability of each polymer to shield the nanoparticle core. For unfavorable solute-polymer interactions, the nanoparticle size increases with hydrophobic block length. However, for favorable solute-polymer interactions, nanoparticle size exhibits a local minimum with respect to the

  14. Properties of glass/carbon fiber reinforced epoxy hybrid polymer composites

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Sevkani, V. R.; Patel, B. R.; Patel, V. B.

    2016-05-01

    Composite Materials are well known for their tailor-made properties. For the fabrication of composites different types of reinforcements are used for different applications. Sometimes for a particular application, one type of reinforcement may not fulfill the requirements. Therefore, more than one type of reinforcements may be used. Thus, the idea of hybrid composites arises. Hybrid composites are made by joining two or more different reinforcements with suitable matrix system. It helps to improve the properties of composite materials. In the present work glass/carbon fiber reinforcement have been used with a matrix triglycidyl ether of tris(m-hydroxy phenyl) phosphate epoxy resin using amine curing agent. Different physical and mechanical properties of the glass, carbon and glass/carbon fiber reinforced polymeric systems have been found out.

  15. Functionalization of emissive conjugated polymer nanoparticles by coprecipitation: consequences for particle photophysics and colloidal properties

    NASA Astrophysics Data System (ADS)

    Singh, Amita; Bezuidenhout, Michael; Walsh, Nichola; Beirne, Jason; Felletti, Riccardo; Wang, Suxiao; Fitzgerald, Kathleen T.; Gallagher, William M.; Kiely, Patrick; Redmond, Gareth

    2016-07-01

    The functionalization of polyfluorene (PFO) nanoparticles by coprecipitation of the conjugated polymer with an amphiphilic comb polymer, consisting of a hydrophobic polystyrene backbone with hydrophilic, carboxylic acid-terminated polyethylene oxide side-chains (PS-PEG-COOH), is investigated. The comb polymer affects the properties of the formed hybrid nanoparticles. Non-functionalized particles are typically larger (28 nm) than functionalized ones (20 nm); peak molar extinction coefficients are found to differ in a similar trend. Zeta potentials are negative, consistent with negative surface charge on PFO particles due to chemical defect formation, with additional charge on functionalized particles due to the pendant carboxylic acid groups. Emission quantum yields of functionalized particles are typically larger, consistent with lower efficiency of energy transfer to quenchers in smaller particles and weaker PFO interchain interactions due to chain dilution. The trend in per-particle fluorescence brightness values, as confirmed by single particle fluorescence imaging, reflects the nanoparticle extinction coefficients. Photostability studies on aqueous dispersions of hybrid particles indicate mild photobrightening under continuous illumination while PFO particles exhibit slow exponential emission decay. Functionalized particles are also resistant to aggregation during exposure to adenocarcinoma cells. Generally, the hybrid particles exhibit more favorable time-, pH- and medium-dependent stabilities, likely due to steric and electrostatic stabilization by PEG-carboxylic acid functionalities. Overall, the functionalized particles exhibit attractive properties: Reasonably small size, tight size distribution, high absorption cross section, radiative rate and emission quantum yield, excellent brightness and photostability, and good colloidal stability.

  16. Micromechanical and macroscopic models of ductile fracture in particle reinforced metallic materials

    NASA Astrophysics Data System (ADS)

    Hu, Chao; Bai, Jie; Ghosh, Somnath

    2007-06-01

    This paper is aimed at developing two modules contributing to the overall framework of multi-scale modelling of ductile fracture of particle reinforced metallic materials. The first module is for detailed micromechanical analysis of particle fragmentation and matrix cracking of heterogeneous microstructures. The Voronoi cell FEM for particle fragmentation is extended in this paper to incorporate ductile failure through matrix cracking in the form of void growth and coalescence using a non-local Gurson-Tvergaard-Needleman (GTN) model. In the resulting enriched Voronoi cell finite element model (VCFEM) or E-VCFEM, the assumed stress-based hybrid VCFEM formulation is overlaid with narrow bands of displacement based elements to accommodate strain softening in the constitutive behaviour. The second module develops an anisotropic plasticity-damage model in the form of the GTN model for macroscopic analysis in the multi-scale material model. Parameters in this model are calibrated from results of homogenization of microstructural variables obtained by E-VCFEM analysis of microstructural representative volume element. Numerical examples conducted yield satisfactory results.

  17. Inflammatory response against different carbon fiber-reinforced PEEK wear particles compared with UHMWPE in vivo.

    PubMed

    Utzschneider, Sandra; Becker, Fabian; Grupp, Thomas M; Sievers, Birte; Paulus, Alexander; Gottschalk, Oliver; Jansson, Volkmar

    2010-11-01

    Poly(ether ether ketone) (PEEK) and its composites are recognized as alternative bearing materials for use in arthroplasty because of their mechanical properties. The objective of this project was to evaluate the biological response of two different kinds of carbon fiber-reinforced (CFR) PEEK compared with ultra-high molecular weight polyethylene (UHMWPE) in vivo as a standard bearing material. Wear particles of the particulate biomaterials were injected into the left knee joint of female BALB/c mice. Assessment of the synovial microcirculation using intravital fluorescence microscopy as well as histological evaluation of the synovial layer were performed 7 days after particle injection. Enhanced leukocyte-endothelial cell interactions and an increase in functional capillary density as well as histological investigations revealed that all tested biomaterials caused significantly (P < 0.05) increased inflammatory reactions compared with control animals (injected with sterile phosphate-buffered saline), without any difference between the tested biomaterials (P > 0.05). These data suggest that wear debris of CFR-PEEK is comparable with UHMWPE in its biological activity. Therefore, CFR-PEEK represents an alternative bearing material because of its superior mechanical and chemical behavior without any increased biological activity of the wear particles, compared with a standard bearing material.

  18. The diffusion welding of 7075Al-3%SiC particles reinforced composites

    NASA Astrophysics Data System (ADS)

    Aydin, M.; Gürler, R.; Türker, M.

    2009-02-01

    A group of 3% SiC particle reinforced Al-7075 alloys was diffusion joined at 560°C between 1 h and 2 h durations under 2 MPa applied pressure in a vacuum of 2 × 10-3 Pa. Optical microscopy and SEM-EDS studies were used to characterise the weldment and the fracture surfaces of all samples investigated. A non-planar interface formation was observed at the bond interface. The maximum shear strength of 137 MPa was obtained with the composite 7075-3% SiC joined for two hours, which is 92% of the shear strength of the parent material. The fracture surface of the 7075-3% SiC composites displayed a non-planar fracture surfaces with some plastic deformation.

  19. Wear Resistance of Aluminum Matrix Composites Reinforced with Al2O3 Particles After Multiple Remelting

    NASA Astrophysics Data System (ADS)

    Klasik, Adam; Pietrzak, Krystyna; Makowska, Katarzyna; Sobczak, Jerzy; Rudnik, Dariusz; Wojciechowski, Andrzej

    2016-08-01

    Based on previous results, the commercial composites of A359 (AlSi9Mg) alloy reinforced with 22 vol.% Al2O3 particles were submitted to multiple remelting by means of gravity casting and squeeze-casting procedures. The studies were focused on tribological tests, x-ray phase analyses, and microstructural examinations. More promising results were obtained for squeeze-casting method mainly because of the reduction of the negative microstructural effects such as shrinkage porosity or other microstructural defects and discontinuities. The results showed that direct remelting may be treated as economically well-founded and alternative way compared to other recycling processes. It was underlined that the multiple remelting method must be analyzed for any material separately.

  20. Biodegradable, polymer encapsulated, metal oxide particles for MRI-based cell tracking.

    PubMed

    Shapiro, Erik M

    2015-01-01

    Metallic particles have shaped the use of magnetic resonance imaging (MRI) for molecular and cellular imaging. Although these particles have generally been developed for extracellular residence, either as blood pool contrast agents or targeted contrast agents, the coopted use of these particles for intracellular labeling has grown over the last 20 years. Coincident with this growth has been the development of metal oxide particles specifically intended for intracellular residence, and innovations in the nature of the metallic core. One promising nanoparticle construct for MRI-based cell tracking is polymer encapsulated metal oxide nanoparticles. Rather than a polymer coated metal oxide nanocrystal of the core: shell type, polymer encapsulated metal oxide nanoparticles cluster many nanocrystals within a polymer matrix. This nanoparticle composite more efficiently packages inorganic nanocrystals, affording the ability to label cells with more inorganic material. Further, for magnetic nanocrystals, the clustering of multiple magnetic nanocrystals within a single nanoparticle enhances r2 and r2* relaxivity. Methods for fabricating polymer encapsulated metal oxide nanoparticles are facile, yielding both varied compositions and synthetic approaches. This review presents a brief history into the use of metal oxide particles for MRI-based cell tracking and details the development and use of biodegradable, polymer encapsulated, metal oxide nanoparticles and microparticles for MRI-based cell tracking.

  1. Biodegradable, polymer encapsulated, metal oxide particles for MRI-based cell tracking

    PubMed Central

    Shapiro, Erik M.

    2014-01-01

    Metallic particles have shaped the use of MRI for molecular and cellular imaging. While these particles have generally been developed for extracellular residence, either as blood pool contrast agents or targeted contrast agents, the coopted use of these particles for intracellular labeling has grown over the last 20 years. Coincident with this growth has been the development of metal oxide particles specifically intended for intracellular residence, and innovations in the nature of the metallic core. One promising nanoparticle construct for MRI-based cell tracking is polymer encapsulated metal oxide nanoparticles. Rather than a polymer coated metal oxide nanocrystal of the core:shell type, polymer encapsulated metal oxide nanoparticles cluster many nanocrystals within a polymer matrix. This nanoparticle composite more efficiently packages inorganic nanocrystals, affording the ability to label cells with more inorganic material. Further, for magnetic nanocrystals, the clustering of multiple magnetic nanocrystals within a single nanoparticle enhances r2 and r2* relaxivity. Methods for fabricating polymer encapsulated metal oxide nanoparticles are facile, yielding both varied compositions and synthetic approaches. This review presents a brief history into the use of metal oxide particles for MRI-based cell tracking and details the development and use of biodegradable, polymer encapsulated, metal oxide nano- and microparticles for MRI-based cell tracking. PMID:24753150

  2. Dielectric properties of polymer-particle nanocomposites influenced by electronic nature of filler surfaces.

    PubMed

    Siddabattuni, Sasidhar; Schuman, Thomas P; Dogan, Fatih

    2013-03-01

    The interface between the polymer and the particle has a critical role in altering the properties of a composite dielectric. Polymer-ceramic nanocomposites are promising dielectric materials for many electronic and power devices, combining the high dielectric constant of ceramic particles with the high dielectric breakdown strength of a polymer. Self-assembled monolayers of electron rich or electron poor organophosphate coupling groups were applied to affect the filler-polymer interface and investigate the role of this interface on composite behavior. The interface has potential to influence dielectric properties, in particular the leakage and breakdown resistance. The composite films synthesized from the modified filler particles dispersed into an epoxy polymer matrix were analyzed by dielectric spectroscopy, breakdown strength, and leakage current measurements. The data indicate that significant reduction in leakage currents and dielectric losses and improvement in dielectric breakdown strengths resulted when electropositive phenyl, electron-withdrawing functional groups were located at the polymer-particle interface. At a 30 vol % particle concentration, dielectric composite films yielded a maximum energy density of ~8 J·cm(-3) for TiO2-epoxy nanocomposites and ~9.5 J·cm(-3) for BaTiO3-epoxy nanocomposites.

  3. Inductive wireless sensor-actuator node for structural health monitoring of fiber reinforced polymers by means of Lamb-waves

    NASA Astrophysics Data System (ADS)

    Focke, Oliver; Salas, Mariugenia; Herrmann, Axel S.; Lang, Walter

    2015-03-01

    Wireless excitation of Piezo-Wafer-Active-Sensors (PWAS) was achieved using Low-frequency coils produced via Tailored-Fiber-Placement. Carbon Fiber Reinforced Polymer behaves as conductor and depending on the frequency it shields radio waves; this effect is rising at high-frequency. A high permeability material was placed under the highfrequency antenna and re-tuning was performed to improve the quality of transmission. In this manner sensor responses were successfully transmitted wirelessly by analog amplitude modulation. The signals were evaluated to verify the functionality in presence of defects like delamination or holes. Generated power was confirmed to be enough to excite the actuator.

  4. Fabrication and static characterization of carbon-fiber-reinforced polymers with embedded NiTi shape memory wire actuators

    NASA Astrophysics Data System (ADS)

    de Araújo, C. J.; Rodrigues, L. F. A.; Coutinho Neto, J. F.; Reis, R. P. B.

    2008-12-01

    In this work, unidirectional carbon-fiber-reinforced polymers (CFRP) with embedded NiTi shape memory alloy (SMA) wire actuators were manufactured using a universal testing machine equipped with a thermally controlled chamber. Beam specimens containing cold-worked, annealed and trained NiTi SMA wires distributed along their neutral plane were fabricated. Several tests in a three-point bending mode at different constant temperatures were performed. To verify thermal buckling effects, electrical activation of the specimens was realized in a cantilevered beam mode and the influence of the SMA wire actuators on the tip deflection of the composite is demonstrated.

  5. Toughening of carbon fiber-reinforced epoxy polymer composites via copolymers and graphene nano-platelets

    NASA Astrophysics Data System (ADS)

    Downey, Markus A.

    Carbon fiber-reinforced epoxy composites currently play a significant role in many different industries. Due to their high cross-link density, aromatic epoxy polymers used as the matrix in composite materials are very strong and stiff however they lack toughness. This dissertation investigates three areas of the carbon fiber-reinforced composite, which have the potential to increase toughness: the carbon fiber surface; the fiber/matrix interphase; and the matrix material. Approaches to improving each area are presented which lead to enhancing the overall composite toughness without reducing other composite mechanical properties. The toughening of the base matrix material, DGEBA/mPDA, was accomplished by two methods: first, using low concentrations of aliphatic copolymers to enhance energy absorption and second by adding graphene nano-platelets (GnP) to act as crack deflection agents. 1wt% copolymer concentration was determined to substantially increase the notched Izod impact strength without reducing other static-mechanical properties. Toughening of DGEBA/mPDA using 3wt% GnP was found to be dependent on the aspect ratio of GnP and treatment of GnP with tetraethylenepentamine (TEPA). GnP C750 enhanced flexural properties but not fracture toughness because the small aspect ratio cannot effectively deflect cracks. TEPA-grafting enhanced GnP/matrix bonding. Larger aspect ratio GnP M5 and M25 showed significant increases in fracture toughness due to better crack deflection but also decreased flexural strength based on limited GnP/matrix bonding. TEPA-grafting mitigated some of the flexural strength reductions for GnP M5, due to enhanced GnP/matrix adhesion. In the high-fiber volume fraction composite, the fiber/matrix bonding was enhanced with UV-ozone surface treatment by reducing a weak fiber surface boundary layer and increasing the concentration of reactive oxygen groups on the fiber surface. Further increases in Mode I fracture toughness were seen with the

  6. Characterization of nanocellulose reinforced semi-interpenetrating polymer network of poly(vinyl alcohol) & polyacrylamide composite films.

    PubMed

    Mandal, Arup; Chakrabarty, Debabrata

    2015-12-10

    Semi-interpenetrating polymer network (semi-IPN) of poly(vinyl alcohol)/polyacrylamide was reinforced with various doses of nanocellulose. The different composite films thus prepared were characterized with respect to their mechanical, thermal, morphological and barrier properties. The composite film containing 5 wt.% of nanocellulose showed the highest tensile strength. The semi-interpenetrating polymer network of poly(vinyl alcohol)/polyacrylamide; and its various composites with nanocellulose were almost identical in their thermal stability. Each of the composites however exhibited much superior stability with respect to the linear poly(vinyl alcohol) and crosslinked polyacrylamide. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies exhibited phase separated morphology where agglomerates of nanocellulose were found to be dispersed in the matrix of the semi-IPN. The moisture vapor transmission rate (MVTR) was the lowest for the film containing 5 wt.% of nanocellulose.

  7. Deformation and fracture of a particle-reinforced aluminum alloy composite: Part I. Experiments

    NASA Astrophysics Data System (ADS)

    Pandey, A. B.; Majumdar, B. S.; Miracle, D. B.

    2000-03-01

    Mechanical tests were performed on a powder-metallurgically processed 7093/SiC/15p discontinuously reinforced aluminum (DRA) composite in different heat-treatment conditions, to determine the influence of matrix characteristics on the composite response. The work-hardening exponent and the strain to failure varied inversely to the strength, similar to monolithic Al alloys, and this dependence was independent of the dominant damage mode. The damage consisted of SiC particle cracks, interface and near-interface debonds, and matrix rupture inside intense slip bands. Fracture surfaces revealed particle fracture-dominated damage for most of the heat-treatment conditions, including an overaged (OA) condition that exhibited a combination of precipitates at the interface and a precipitate-free zone (PFZ) in the immediate vicinity. In the highly OA conditions and in a 450°C as-rolled condition, when the composite strength became less than 400 MPa, near-interface matrix rupture became dominant. A combination of a relatively weak matrix and a weak zone around the particle likely contributed to this damage mode over that of particle fracture. Fracture-toughness tests show that it is important to maintain a proper geometry and testing procedure to obtain valid fracture-toughness data. Overaged microstructures did reveal a recovery of fracture toughness as compared to the peak-aged (PA) condition, unlike the lack of toughness recovery reported earlier for a similar 7XXX (Al-Zn-Cu-Mg)—based DRA. The PA material exhibited extensive localization of damage and plasticity. The low toughness of the DRA in this PA condition is explored in detail, using fractography and metallography. The damage and fracture micromechanisms formed the basis for modeling the strength, elongation, toughness, and damage, which are described in Part II of this work.

  8. An experimental investigation into the behavior of glassfiber reinforced polymer elements at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Qian, Kenny Zongxi

    This thesis presents a literature review and results of an experimental study about the effects of high temperatures and cyclic loading on the physical and mechanical properties of pultruded glass fiber reinforced polymer (GFRP) square tubes used in civil engineering structural applications. Most laboratory researches have focused mainly on the effect of elevated temperature on the compressive strength of the GFRP square tubes. Limited research has focused on the tensile strength of GFRP coupons under elevated temperatures. Dynamic Mechanical Analyses (DMA) was performed to assess the viscoelastic behavior including the glass transition temperature of GFRP. Sixteen GFRP coupons were tested under elevated temperatures to investigate the tensile strength and the effect of elevated temperatures to the tensile strength of GFRP. The results of an experimental program performed on fifty GFRP square tubes with different designs in 1.83m at normal temperatures were discussed to investigate compression performance. Another experimental program was performed on 20 GFRP square tubes with different designs in 1.22m under elevated temperatures. The experiments results were discussed and showed that the compressive strength of GFRP material was influenced by several factors including the glass transition v temperature and the connection bolts. Failure modes under 25°C and 75°C were crushing and the failure modes with the temperatures above 75°C were not typical crushing due to the glass transition of GFRP. Sixteen GFRP square tubes with length of 0.61m were tested with the same experimental program under elevated temperatures as the control group. Twelve GFRP square tubes with the same size were subjected to cyclic loading under elevated temperatures to investigate the effect of the cyclic loading to the compression properties of GFRP material. According to the experimental results and the discussion, the stiffness was reduced by the cyclic loading. On the contrary, the

  9. Dissipative particle dynamics simulation of depletion layer and polymer migration in micro- and nanochannels for dilute polymer solutions.

    PubMed

    Fedosov, Dmitry A; Em Karniadakis, George; Caswell, Bruce

    2008-04-14

    The flows of dilute polymer solutions in micro- and nanoscale channels are of both fundamental and practical importance in variety of applications in which the channel gap is of the same order as the size of the suspended particles or macromolecules. In such systems depletion layers are observed near solid-fluid interfaces, even in equilibrium, and the imposition of flow results in further cross-stream migration of the particles. In this work we employ dissipative particle dynamics to study depletion and migration in dilute polymer solutions in channels several times larger than the radius of gyration (Rg) of bead-spring chains. We compare depletion layers for different chain models and levels of chain representation, solvent quality, and relative wall-solvent-polymer interactions. By suitable scaling the simulated depletion layers compare well with the asymptotic lattice theory solution of depletion near a repulsive wall. In Poiseuille flow, polymer migration across the streamlines increases with the Peclet and the Reynolds number until the center-of-mass distribution develops two symmetric off-center peaks which identify the preferred chain positions across the channel. These appear to be governed by the balance of wall-chain repulsive interactions and an off-center driving force of the type known as the Segre-Silberberg effect.

  10. Recycling high-performance carbon fiber reinforced polymer composites using sub-critical and supercritical water

    NASA Astrophysics Data System (ADS)

    Knight, Chase C.

    Carbon fiber reinforced plastics (CFRP) are composite materials that consist of carbon fibers embedded in a polymer matrix, a combination that yields materials with properties exceeding the individual properties of each component. CFRP have several advantages over metals: they offer superior strength to weight ratios and superior resistance to corrosion and chemical attack. These advantages, along with continuing improvement in manufacturing processes, have resulted in rapid growth in the number of CFRP products and applications especially in the aerospace/aviation, wind energy, automotive, and sporting goods industries. Due to theses well-documented benefits and advancements in manufacturing capabilities, CFRP will continue to replace traditional materials of construction throughout several industries. However, some of the same properties that make CFRP outstanding materials also pose a major problem once these materials reach the end of service life. They become difficult to recycle. With composite consumption in North America growing by almost 5 times the rate of the US GDP in 2012, this lack of recyclability is a growing concern. As consumption increases, more waste will inevitably be generated. Current composite recycling technologies include mechanical recycling, thermal processing, and chemical processing. The major challenge of CFRP recycling is the ability to recover materials of high-value and preserve their properties. To this end, the most suitable technology is chemical processing, where the polymer matrix can be broken down and removed from the fiber, with limited damage to the fibers. This can be achieved using high concentration acids, but such a process is undesirable due to the toxicity of such materials. A viable alternative to acid is water in the sub-critical and supercritical region. Under these conditions, the behavior of this abundant and most environmentally friendly solvent resembles that of an organic compound, facilitating the breakdown

  11. Flow-Induced Anisotropy in Mixtures of Associative Polymers and Latex Particles.

    PubMed

    Belzung; Lequeux; Vermant; Mewis

    2000-04-01

    The effect of associative polymers on the structure and rheological behavior of colloidal suspensions is discussed. Adding associative polymer is known to increase the viscosity of the suspensions. At high shear rates the increase is close to what could be expected on the basis of the hydrodynamic effects of the added polymer. At low shear rates the viscosity increases much more. Small-angle light scattering (SALS) during flow is used here to investigate the underlying structural mechanisms. The SALS patterns indicate that the associative polymer changes the particulate structure: characteristic butterfly patterns appear even at relatively low particle volume fractions. They are not present in the suspensions without associative polymer. The patterns indicate that fluctuations in particle concentration are more pronounced in the flow direction than in the vorticity direction and that anisotropic particulate structures with an orientation along the vorticity direction develop. The evolution of their characteristic length scale during flow has been followed over time. Changing the hydrophilic part of the polymer from polyacrylamide to polyacrylic acid induces stronger associative interactions. In the suspensions this results in a reduction of the relative viscosity rather than an increase. The difference in degree of associativity between the polymers also has an effect on the SALS patterns in the suspensions both at rest and during flow. The rheology as well as the SALS suggest the presence of a strong polymer network in the second system. The competition between adsorption of the associative polymer on the particles with the intermolecular associations between the polymer chains seems to be responsible for the observed differences. Copyright 2000 Academic Press.

  12. Encapsulation of the HDACi Ex527 into Liposomes and Polymer-Based Particles.

    PubMed

    Hennig, Dorle; Imhof, Diana

    2017-01-01

    Incorporation of drugs into particles can improve their therapeutic effectiveness. Solubility, half-life time, targeting, and the release of the drug can be modified by the encapsulation into a particle. Histone deacetylase inhibitors have a great potential to be used as therapeutics for many different diseases. In this chapter, we describe the inclusion of the low molar mass HDACi Ex527 into polymer-based particles and liposomes.

  13. Polymer ligand–induced autonomous sorting and reversible phase separation in binary particle blends

    PubMed Central

    Schmitt, Michael; Zhang, Jianan; Lee, Jaejun; Lee, Bongjoon; Ning, Xin; Zhang, Ren; Karim, Alamgir; Davis, Robert F.; Matyjaszewski, Krzysztof; Bockstaller, Michael R.

    2016-01-01

    The tethering of ligands to nanoparticles has emerged as an important strategy to control interactions and organization in particle assembly structures. We demonstrate that ligand interactions in mixtures of polymer-tethered nanoparticles (which are modified with distinct types of polymer chains) can impart upper or lower critical solution temperature (UCST/LCST)–type phase behavior on binary particle mixtures in analogy to the phase behavior of the corresponding linear polymer blends. Therefore, cooling (or heating) of polymer-tethered particle blends with appropriate architecture to temperatures below (or above) the UCST (or LCST) results in the organization of the individual particle constituents into monotype microdomain structures. The shape (bicontinuous or island-type) and lengthscale of particle microdomains can be tuned by variation of the composition and thermal process conditions. Thermal cycling of LCST particle brush blends through the critical temperature enables the reversible growth and dissolution of monoparticle domain structures. The ability to autonomously and reversibly organize multicomponent particle mixtures into monotype microdomain structures could enable transformative advances in the high-throughput fabrication of solid films with tailored and mutable structures and properties that play an important role in a range of nanoparticle-based material technologies. PMID:28028538

  14. Effects of water storage of E-glass fiber reinforced denture base polymers on residual methyl methacrylate content.

    PubMed

    Bayraktar, Gulsen; Duran, Ozlem; Bural, Canan; Guvener, Bora

    2004-07-15

    This study investigated the effect of water storage on residual methyl methacrylate (MMA) content of continuous E-glass fiber (Wetrotex International) reinforced denture base polymers. Heat-polymerization (short- and long-term boiling and conventional curing cycle using Meliodent), autopolymerization (processed in air at room temperature and in water at 60 degrees C with the use of Meliodent Rapid Repair), and microwave-polymerization (3 min at 500 W with the use of Acron MC) were employed. The residual MMA contents of 120 specimens were analyzed by high-performance liquid chromatography at deflasking (control) and after water (37 degrees C) storage of 1 day, 1 week, and 1 month. Bonferroni's pairwise comparison test was used for statistical analysis. Significant reduction were determined only in the long-term terminal boiled heat-polymerized test group at the end of 1 day (p < 0.01), 1 week (p < 0.05) and also 1 month of water storage (p < 0.01). Significant reduction in autopolymerized test groups started even after 1 week of water storage (p < 0.05). Microwave-polymerized test groups did not show a significant residual MMA reduction in all time intervals (p > 0.05). The polymerization methods and cycles applied to the glass fiber reinforced denture base polymers influence both the content and the reduction of residual MMA after water storage.

  15. Microscopic study of surface degradation of glass fiber-reinforced polymer rods embedded in concrete castings subjected to environmental conditioning

    SciTech Connect

    Bank, L.C.; Puterman, M.

    1997-12-31

    The surface degradation of glass fiber-reinforced polymer (GFRP) pultruded rods when embedded in concrete castings and subjected to environmental conditioning is discussed in this paper. Investigation of the degradation of the GFRP rods were performed using optical microscopy and scanning electron microscopy (SEM). Unidirectionally reinforced pultruded rods (6.3- and 12.7-mm diameters) containing E-glass fibers in polyester and vinylester matrices were conditioned at standard laboratory conditions (21 C, 65% relative humidity) or submerged in aqueous solutions (tap water) at 80 C for durations of 14 and 84 days. Observations of the surfaces and cross-sections of the rods by optical microscopy and SEM revealed a variety of degradation phenomena. Embedded hygrothermally conditioned rods were found to have developed surface blisters of different sizes and depths. SEM studies of the surface revealed degradation of the polymer matrix material and exposure and degradation of the fibers close to the surface of the rods. The rods with the vinylester resin matrix showed less extensive degradation than those with the polyester resin matrix; however, the degradation characteristics of the two types of rods appear to be similar.

  16. Size-dependent mechanical behavior of nanoscale polymer particles through coarse-grained molecular dynamics simulation.

    PubMed

    Zhao, Junhua; Nagao, Shijo; Odegard, Gregory M; Zhang, Zhiliang; Kristiansen, Helge; He, Jianying

    2013-12-21

    Anisotropic conductive adhesives (ACAs) are promising materials used for producing ultra-thin liquid-crystal displays. Because the mechanical response of polymer particles can have a significant impact in the performance of ACAs, understanding of this apparent size effect is of fundamental importance in the electronics industry. The objective of this research is to use a coarse-grained molecular dynamics model to verify and gain physical insight into the observed size dependence effect in polymer particles. In agreement with experimental studies, the results of this study clearly indicate that there is a strong size effect in spherical polymer particles with diameters approaching the nanometer length scale. The results of the simulations also clearly indicate that the source for the increases in modulus is the increase in relative surface energy for decreasing particle sizes. Finally, the actual contact conditions at the surface of the polymer nanoparticles are shown to be similar to those predicted using Hertz and perfectly plastic contact theory. As ACA thicknesses are reduced in response to reductions in polymer particle size, it is expected that the overall compressive stiffness of the ACA will increase, thus influencing the manufacturing process.

  17. Size-dependent mechanical behavior of nanoscale polymer particles through coarse-grained molecular dynamics simulation

    PubMed Central

    2013-01-01

    Anisotropic conductive adhesives (ACAs) are promising materials used for producing ultra-thin liquid-crystal displays. Because the mechanical response of polymer particles can have a significant impact in the performance of ACAs, understanding of this apparent size effect is of fundamental importance in the electronics industry. The objective of this research is to use a coarse-grained molecular dynamics model to verify and gain physical insight into the observed size dependence effect in polymer particles. In agreement with experimental studies, the results of this study clearly indicate that there is a strong size effect in spherical polymer particles with diameters approaching the nanometer length scale. The results of the simulations also clearly indicate that the source for the increases in modulus is the increase in relative surface energy for decreasing particle sizes. Finally, the actual contact conditions at the surface of the polymer nanoparticles are shown to be similar to those predicted using Hertz and perfectly plastic contact theory. As ACA thicknesses are reduced in response to reductions in polymer particle size, it is expected that the overall compressive stiffness of the ACA will increase, thus influencing the manufacturing process. PMID:24359191

  18. The biological response to nanometre-sized polymer particles

    PubMed Central

    Liu, Aiqin; Richards, Laura; Bladen, Catherine L.; Ingham, Eileen; Fisher, John; Tipper, Joanne L.

    2015-01-01

    Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1–1.0 μm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20 nm, 60 nm, 200 nm and 1.0 μm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNCs). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20 nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNCs at a concentration of 100 μm3 particles per cell after 12 and 24 h. The micrometre-size UHMWPE wear particles (0.1–1.0 μm) and 60 nm, 200 nm and 1.0 μm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNCs. These results indicated that particles below circa 50 nm fail to activate PBMNCs and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages. PMID:26004221

  19. Polymer degradation and ultrafine particles - Potential inhalation hazards for astronauts

    NASA Technical Reports Server (NTRS)

    Ferin, J.; Oberdoerster, G.

    1992-01-01

    To test the hypothesis that exposure to ultrafine particles results in an increased interstiatilization of the particles which is accompanied by an acute pathological inflammation, rats were exposed to titanium dioxide (TiO2) particles by intratracheal instillation and by inhalation. Both acute intratracheal instillation and subchronic inhalation studies on rats show that ultrafine TiO2 particles access the pulmonary interstitium to a larger extent than fine particles and that they elicit an inflammatory response as indicated by PMN increase in lavaged cells. The release of ultrafine particles into the air of an enclosed environment from a thermodegradation event or from other sources is a potential hazard for astronauts. Knowing the mechanisms of action is a prerequisite for technical or medical countermeasures.

  20. Pore Structure of Macroporous Polymers Using Polystyrene/Silica Composite Particles as Pickering Stabilizers.

    PubMed

    Tu, Shuhua; Zhu, Chenxu; Zhang, Lingyun; Wang, Haitao; Du, Qiangguo

    2016-12-13

    A novel approach for the preparation of interconnected macroporous polymers with a controllable pore structure was reported. The method was based on the polymerization of water-in-oil Pickering high internal phase emulsion (HIPE) stabilized by polystyrene (PS)/silica composite particles. The composite Pickering stabilizers were facilely obtained by mixing positively charged PS microspheres and negatively charged silica nanoparticles, and their amphiphilicity could be delicately tailored by varying the ratio of PS and silica. The droplet size of Pickering HIPEs was characterized using an optical microscope. The pore structure of polymer foams was observed using a scanning electron microscope. The interconnectivity of macroporous polymers was evaluated upon their gas permeability, which was greatly improved after etching PS microspheres included in the Pickering stabilizers with tetrahydrofuran. As a result, fine tailoring of the pore structure of polymer foams could be realized by simply tuning the ratio of PS to silica particles in the composite stabilizer.

  1. Development of a novel test-setup for identifying the frictional characteristics of carbon fibre reinforced polymer composites at high surface pressure

    NASA Astrophysics Data System (ADS)

    Saxena, Prateek; Schinzel, Marie; Andrich, Manuela; Modler, Niels

    2016-09-01

    Carbon fibre reinforced polymer composites are extensively used in industrial applications. They are light in weight and have excellent load bearing properties. To understand this material's behaviour when carrying loads at high pressure, a tensile-friction test device was developed that can apply a contact surface pressure between composite and counterpart of 50-300 MPa. A tribological investigation of carbon fibre reinforced epoxy composites was carried out, in which the influence of the surface morphology was investigated by using grinding and sandblasting techniques. The friction coefficient of the polymer composite was measured at 100 MPa surface pressure against uncoated and Diamond-Like Carbon coated stainless steel counterparts.

  2. Damage Precursor Detection in Polymer Matrix Composites Using Novel Smart Composite Particles

    DTIC Science & Technology

    2016-09-20

    was obtained upon the evaporation of the solvent from the organic layer. The insoluble solids were removed via the application of hot ethanol. The...Cyclic loading parameter in tensile fatigue test. Compression test: The goal for the application of cyclobutane-based polymer in its solid state was...AFRL-AFOSR-VA-TR-2016-0328 Damage Precursor Detection in Polymer Matrix Composites Using Novel Smart Composite Particles Aditi Chattopadhyay ARIZONA

  3. Design of sustained release fine particles using two-step mechanical powder processing: particle shape modification of drug crystals and dry particle coating with polymer nanoparticle agglomerate.

    PubMed

    Kondo, Keita; Ito, Natsuki; Niwa, Toshiyuki; Danjo, Kazumi

    2013-09-10

    We attempted to prepare sustained release fine particles using a two-step mechanical powder processing method; particle-shape modification and dry particle coating. First, particle shape of bulk drug was modified by mechanical treatment to yield drug crystals suitable for the coating process. Drug crystals became more rounded with increasing rotation speed, which demonstrates that powerful mechanical stress yields spherical drug crystals with narrow size distribution. This process is the result of destruction, granulation and refinement of drug crystals. Second, the modified drug particles and polymer coating powder were mechanically treated to prepare composite particles. Polymer nanoparticle agglomerate obtained by drying poly(meth)acrylate aqueous dispersion was used as a coating powder. The porous nanoparticle agglomerate has superior coating performance, because it is completely deagglomerated under mechanical stress to form fine fragments that act as guest particles. As a result, spherical drug crystals treated with porous agglomerate were effectively coated by poly(meth)acrylate powder, showing sustained release after curing. From these findings, particle-shape modification of drug crystals and dry particle coating with nanoparticle agglomerate using a mechanical powder processor is expected as an innovative technique for preparing controlled-release coated particles having high drug content and size smaller than 100 μm.

  4. Mechanical analysis of carbon fiber reinforced shape memory polymer composite for self-deployable structure in space environment

    NASA Astrophysics Data System (ADS)

    Hong, Seok Bin; Ahn, Yong San; Jang, Joon Hyeok; Kim, Jin-Gyun; Goo, Nam Seo; Yu, Woong-Ryeol

    2016-04-01

    Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli. Reinforcements as carbon fiber had been used for making shape memory polymer composite (CF-SMPC). This study investigated a possibility of designing self-deployable structures in harsh space condition using CF-SMPCs and analyzed their shape memory behaviors with constitutive equation model.CF-SMPCs were prepared using woven carbon fabrics and a thermoset epoxy based SMP to obtain their basic mechanical properties including actuation in harsh environment. The mechanical and shape memory properties of SMP and CF-SMPCs were characterized using dynamic mechanical analysis (DMA) and universal tensile machine (UTM) with an environmental chamber. The mechanical properties such as flexural strength and tensile strength of SMP and CF-SMPC were measured with simple tensile/bending test and time dependent shape memory behavior was characterized with designed shape memory bending test. For mechanical analysis of CF-SMPCs, a 3D constitutive equation of SMP, which had been developed using multiplicative decomposition of the deformation gradient and shape memory strains, was used with material parameters determined from CF-SMPCs. Carbon fibers in composites reinforced tensile and flexural strength of SMP and acted as strong elastic springs in rheology based equation models. The actuation behavior of SMP matrix and CF-SMPCs was then simulated as 3D shape memory bending cases. Fiber bundle property was imbued with shell model for more precise analysis and it would be used for prediction of deploying behavior in self-deployable hinge structure.

  5. Polymer composite adsorbents using particles of molecularly imprinted polymers or aluminium oxide nanoparticles for treatment of arsenic contaminated waters.

    PubMed

    Önnby, L; Pakade, V; Mattiasson, B; Kirsebom, H

    2012-09-01

    Removal of As(V) by adsorption from water solutions was studied using three different synthetic adsorbents. The adsorbents, (a) aluminium nanoparticles (Alu-NPs, <50 nm) incorporated in amine rich cryogels (Alu-cryo), (b) molecular imprinted polymers (<38 μm) in polyacrylamide cryogels (MIP-cryo) and (c) thiol functionalised cryogels (SH-cryo) were evaluated regarding material characteristics and arsenic removal in batch test and continuous mode. Results revealed that a composite design with particles incorporated in cryogels was a successful means for applying small particles (nano- and micro- scale) in water solutions with maintained adsorption capacity and kinetics. Low capacity was obtained from SH-cryo and this adsorbent was hence excluded from the study. The adsorption capacities for the composites were 20.3 ± 0.8 mg/g adsorbent (Alu-cryo) and 7.9 ± 0.7 mg/g adsorbent (MIP-cryo) respectively. From SEM images it was seen that particles were homogeneously distributed in Alu-cryo and heterogeneously distributed in MIP-cryo. The particle incorporation increased the mechanical stability and the polymer backbones of pure polyacrylamide (MIP-cryo) were of better stability than the amine containing polymer backbone (Alu-cryo). Both composites worked well in the studied pH range of pH 2-8. Adsorption tested in real wastewater spiked with arsenic showed that co-ions (nitrate, sulphate and phosphate) affected arsenic removal for Alu-cryo more than for MIP-cryo. Both composites still adsorbed well in the presence of counter-ions (copper and zinc) present at low concentrations (μg/l). The unchanged and selective adsorption in realistic water observed for MIP-cryo was concluded to be due to a successful imprinting, here controlled using a non-imprinted polymer (NIP). A development of MIP-cryo is needed, considering its low adsorption capacity.

  6. Core-shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery

    NASA Astrophysics Data System (ADS)

    Oka, Chiemi; Ushimaru, Kazunori; Horiishi, Nanao; Tsuge, Takeharu; Kitamoto, Yoshitaka

    2015-05-01

    Core-shell composite particles with biodegradability and superparamagnetic behavior were prepared using a Pickering emulsion for targeted drug delivery based on magnetic guidance. The composite particles were composed of a core of biodegradable polymer and a shell of assembled magnetic iron oxide nanoparticles. It was found that the dispersibility of the nanoparticles is crucial for controlling the core-shell structure. The addition of a small amount of dispersant into the nanoparticle's suspension could improve the dispersibility and led to the formation of composite particles with a thin magnetic shell covering a polymeric core. The composite particles were also fabricated with a model drug loaded into the core, which was released via hydrolysis of the core under strong alkaline conditions. Because the core can also be biodegraded by lipase, this result suggests that the slow release of the drug from the composite particles should occur inside the body.

  7. Preparation of hemispherical polymer particles by cleavage of a Janus poly(methyl methacrylate)/polystyrene composite particle.

    PubMed

    Yamashita, Nobuko; Konishi, Natsumi; Tanaka, Takuya; Okubo, Masayoshi

    2012-09-04

    Micrometer-sized, hemispherical particles were successfully prepared as a result of the cleavage of Janus PMMA/PS composite particles by dispersion into acetone/water (9/1-10/0 v/v) media or a THF/water (8/2 v/v) medium. The spherical composite particles having a Janus structure were prepared by the slow evaporation of toluene from homogeneous PMMA/PS/toluene droplets dispersed in an aqueous medium in advance. It was clarified that the difference in affinity between PMMA and PS phases with respect to the media caused the cleavage of the composite particles. This method is expected to be a novel approach to the preparation of nonspherical polymer particles.

  8. Polymer particles filled with multiple colloidal silica via in situ sol-gel process and their thermal property

    NASA Astrophysics Data System (ADS)

    Byun, Hongsik; Hu, Jiayun; Pakawanit, Phakkhananan; Srisombat, Laongnuan; Kim, Jun-Hyun

    2017-01-01

    The in situ formation of dielectric silica (SiO2) particles was carried out in the presence of temperature-responsive poly(N-isopropylacrylamide) particles. Unlike the typical sol-gel method used to prepare various SiO2 particles, the highly uniform growth of SiO2 particles was achieved within the cross-linked polymer particles (i.e., the polymer particles were filled with the SiO2 particles) simply by utilizing interfacial interactions, including the van der Waals attractive force and hydrogen bonding in nanoscale environments. The structural and morphological features as well as the thermal behaviors of these composites were thoroughly examined by electron microscopes, dynamic light scattering, and thermal analyzers. In particular, the thermal properties of these composites were completely different from the bare polymer, SiO2 particles, and their mixtures, which clearly suggested the successful incorporation of multiple SiO2 particles within the cross-linked polymer particles. Similarly, titanium oxide (TiO2) particles were easily embedded within the polymer particle template which exhibited improved overall properties. As a whole, understanding in situ formation of nanoscale inorganic particles within polymer particle templates can allow for designing novel composite materials possessing enhanced chemical and physical properties.

  9. Theoretical predictions of structures in dispersions containing charged colloidal particles and non-adsorbing polymers.

    PubMed

    Xie, Fei; Turesson, Martin; Woodward, Clifford E; van Gruijthuijsen, Kitty; Stradner, Anna; Forsman, Jan

    2016-04-28

    We develop a theoretical model to describe structural effects on a specific system of charged colloidal polystyrene particles, upon the addition of non-adsorbing PEG polymers. This system has previously been investigated experimentally, by scattering methods, so we are able to quantitatively compare predicted structure factors with corresponding experimental data. Our aim is to construct a model that is coarse-grained enough to be computationally manageable, yet detailed enough to capture the important physics. To this end, we utilize classical polymer density functional theory, wherein all possible polymer configurations are accounted for, subject to a mean-field Boltzmann weight. We make efforts to counteract drawbacks with this mean-field approach, resulting in structural predictions that agree very well with computationally more demanding simulations. Electrostatic interactions are handled at the fully non-linear Poisson-Boltzmann level, and we demonstrate that a linearization leads to less accurate predictions. The particle charge is an experimentally unknown parameter. We define the surface charge such that the experimental and theoretical gel point at equal polymer concentration coincide. Assuming a fixed surface charge for a certain salt concentration, we find very good agreements between measured and predicted structure factors across a wide range of polymer concentrations. We also present predictions for other structural quantities, such as radial distribution functions, and cluster size distributions. Finally, we demonstrate that our model predicts the occurrence of equilibrium clusters at high polymer concentrations, but low particle volume fractions and salt levels.

  10. The effect of shock wave impingement on thin, woven glass fiber reinforced, polymer composite plates

    NASA Astrophysics Data System (ADS)

    Jahnke, Douglas M.

    High-performance fiber-reinforced polymer (FRP) composites have been increasingly used in many applications over the last 30 years. Their high specific stiffness, specific strength, and energy absorption capacity have made them attractive as replacements for traditional materials. While the dynamic response of homogeneous or monolithic materials has been well documented, the response of FRP composites is still under investigation. Knowledge of the response of FRP composites under this type of loading is essential to evaluating its performance as a structural or protective material. While such information starts to be slowly available, the effects of dynamic thermomechanical extremes such as shock wave loading on the FRP composites is relatively unknown. The challenge then is to develop a consistent laboratory methodology that allows investigations of the interactions between a FRP composite and a shock wave and eventually testing of such materials for performance evaluations under shock loading. Measuring the deformation of test specimens caused by shock wave impingement of different intensities was basic to understanding the gross effects on the FRP composites. In early tests, displacement across the diameter of the test specimen was measured after the end of the test giving a static measurement of the permanent deformation. To allow meaningful comparisons between disparate materials subject to different shock wave intensities a method of weighting and normalizing the was developed. The complexity of setting up and running a shock wave test limited the number tests could be performed, so while the results aren't statically robust, the trends observed are useful in comparing or choosing among different materials. A Time-Resolved Catadioptric Stereo Digital Image Correlation (TRC-SDIC) technique was developed which provide a non-contact, full-field method of measuring deformation over the time span from the impingement of the shock wave including the maximum

  11. Simulating the Rayleigh-Taylor instability in polymer fluids with dissipative particle dynamics

    NASA Astrophysics Data System (ADS)

    Li, Yanggui; Geng, Xingguo; Zhuang, Xin; Wang, Lihua; Ouyang, Jie

    2016-04-01

    The Rayleigh-Taylor (RT) instability that occurs in the flow of polymer fluids is numerically investigated with dissipative particle dynamics (DPD) method at the mesoscale particle level. For modeling two-phase flow, the Flory-Huggins parameter is introduced to model binary fluids. And the polymer chains in fluids are described by the modified FENE model that depicts both the elastic tension and the elastic repulsion between the adjacent beads with bond length as the equilibrium length of one segment. Besides, a bead repulsive potential is employed to capture entanglements between polymer chains. Through our model and numerical simulation, we research the dynamics behaviors of the RT instability in polymer fluid medium. Furthermore, we also explore the effects of polymer volume concentration, chain length, and extensibility on the evolution of RT instability. These simulation results show that increasing any of the parameters, concentration, chain length, and extensibility, the saturation length of spikes becomes longer, and the two polymer fluids have less mixture. On the contrary, for the case of low concentration, or short chain, or small extensibility, the spikes easily split and break up, and the RT instability pattern evolves into chaotic structure. These observations indicate that the polymer and its properties drastically modify the RT instability pattern.

  12. Dissipative particle dynamics simulation for the density currents of polymer fluids

    NASA Astrophysics Data System (ADS)

    Li, Yanggui; Geng, Xingguo; Liu, Zhijun; Liu, Qingsheng; Ouyang, Jie

    2016-11-01

    In this work, the two-dimensional lock-exchange density currents of polymer fluids are numerically investigated using dissipative particle dynamics (DPD) at the mesoscale particle level. A modified finitely extensible nonlinear elastic (FENE) chain model is chosen to describe the polymer system, which perfectly depicts not only the elastic tension but also the elastic repulsion between the adjacent beads with bond length as the equilibrium length of one segment. Through the model and numerical simulation, we analyze the dynamics behavior of the density currents of polymer fluids. A comparison with its Newtonian counterpart suggests that the interface between two polymer fluids is more smoothed, and the front structure is different from the Newtonian case because the Kelvin-Helmholtz instability and cleft instability are suppressed by the polymer. Besides, we also probe the influences of polymer volume concentration, chain length and extensibility on the density currents. These simulation results show that increasing any of the parameters, concentration, chain length, and extensibility, the inhibiting effect of polymer on the density currents becomes more significant.

  13. 25th anniversary article: polymer-particle composites: phase stability and applications in electrochemical energy storage.

    PubMed

    Srivastava, Samanvaya; Schaefer, Jennifer L; Yang, Zichao; Tu, Zhengyuan; Archer, Lynden A

    2014-01-15

    Polymer-particle composites are used in virtually every field of technology. When the particles approach nanometer dimensions, large interfacial regions are created. In favorable situations, the spatial distribution of these interfaces can be controlled to create new hybrid materials with physical and transport properties inaccessible in their constituents or poorly prepared mixtures. This review surveys progress in the last decade in understanding phase behavior, structure, and properties of nanoparticle-polymer composites. The review takes a decidedly polymers perspective and explores how physical and chemical approaches may be employed to create hybrids with controlled distribution of particles. Applications are studied in two contexts of contemporary interest: battery electrolytes and electrodes. In the former, the role of dispersed and aggregated particles on ion-transport is considered. In the latter, the polymer is employed in such small quantities that it has been historically given titles such as binder and carbon precursor that underscore its perceived secondary role. Considering the myriad functions the binder plays in an electrode, it is surprising that highly filled composites have not received more attention. Opportunities in this and related areas are highlighted where recent advances in synthesis and polymer science are inspiring new approaches, and where newcomers to the field could make important contributions.

  14. Fundamental Studies of Low Velocity Impact Resistance of Graphite Fiber Reinforced Polymer Matrix Composites. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1985-01-01

    A study was conducted to relate the impact resistance of graphite fiber reinforced composites with matrix properties through gaining an understanding of the basic mechanics involved in the deformation and fracture process, and the effect of the polymer matrix structure on these mechanisms. It was found that the resin matrix structure influences the composite impact resistance in at least two ways. The integration of flexibilizers into the polymer chain structure tends to reduce the T sub g and the mechanical properties of the polymer. The reduction in the mechanical properties of the matrix does not enhance the composite impact resistance because it allows matrix controlled failure to initiate impact damage. It was found that when the instrumented dropweight impact tester is used as a means for assessing resin toughness, the resin toughness is enhanced by the ability of the clamped specimen to deflect enough to produce sufficient membrane action to support a significant amount of the load. The results of this study indicate that crossplied composite impact resistance is very much dependent on the matrix mechanical properties.

  15. Inhibition of MMP-13 with modified polymer particles

    NASA Astrophysics Data System (ADS)

    Tran, Hai; Bratlie, Kaitlin M.

    2016-06-01

    Matrix metalloproteinases (MMPs) are proteases that destroy the extracellular matrix and have important roles in the foreign body response, wound healing, and disease. Of particular importance is the chronic wound environment in which MMP activity is increased, resulting in destruction of the de novo extracellular matrix. One potential treatment of these wounds would be to use dressings that are capable of inhibiting MMP activity. In this study, we examined the effect of seven polymer modifiers (2-amino-3-guanidinopropionic acid, arginine, carnitine, citrulline, creatine, 3-guanidino propionic acid, and Nw-nitro-L-arginine) on MMP-13 activity. MMP-13 is a collagenase that is present in chronic wounds and is zinc dependent. Our results showed that these polymer modifiers were able to inhibit MMP-13 activity to varying degrees. The mechanism of inhibition appears to be binding zinc to the modifiers.

  16. Plasma polymer-functionalized silica particles for heavy metals removal.

    PubMed

    Akhavan, Behnam; Jarvis, Karyn; Majewski, Peter

    2015-02-25

    Highly negatively charged particles were fabricated via an innovative plasma-assisted approach for the removal of heavy metal ions. Thiophene plasma polymerization was used to deposit sulfur-rich films onto silica particles followed by the introduction of oxidized sulfur functionalities, such as sulfonate and sulfonic acid, via water-plasma treatments. Surface chemistry analyses were conducted by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. Electrokinetic measurements quantified the zeta potentials and isoelectric points (IEPs) of modified particles and indicated significant decreases of zeta potentials and IEPs upon plasma modification of particles. Plasma polymerized thiophene-coated particles treated with water plasma for 10 min exhibited an IEP of less than 3.5. The effectiveness of developed surfaces in the adsorption of heavy metal ions was demonstrated through copper (Cu) and zinc (Zn) removal experiments. The removal of metal ions was examined through changing initial pH of solution, removal time, and mass of particles. Increasing the water plasma treatment time to 20 min significantly increased the metal removal efficiency (MRE) of modified particles, whereas further increasing the plasma treatment time reduced the MRE due to the influence of an ablation mechanism. The developed particulate surfaces were capable of removing more than 96.7% of both Cu and Zn ions in 1 h. The combination of plasma polymerization and oxidative plasma treatment is an effective method for the fabrication of new adsorbents for the removal of heavy metals.

  17. Biocompatible shaped particles from dried multilayer polymer capsules.

    PubMed

    Chen, Jun; Kozlovskaya, Veronika; Goins, Allison; Campos-Gomez, Javier; Saeed, Mohammad; Kharlampieva, Eugenia

    2013-11-11

    We demonstrated a simple and facile approach to fabricate biocompatible monodisperse hollow microparticles of controlled geometry. The hemispherical, spherical, and cubical microparticles are obtained by drying multilayer capsules of hydrogen-bonded poly(N-vinylpyrrolidone)/tannic acid (PVPON/TA)n. Drying spherical capsules results in hemispherical particles if 15 < n < 20. This shape transformation is controlled by capsule stiffness, which is regulated by the layer number, capsule diameter, and PVPON molecular weight. Cubical and spherical hollow particles maintaining their three-dimensional shapes in the dry state are obtained if n ≥ 25.5. A 17-fold stiffness increase is required to lead from totally collapsed (PVPON/TA)5.5 to dried self-supporting (PVPON/TA)25.5 particles of 2 μm in dimensions. All hollow particles could be further resuspended in aqueous solutions while retaining their shapes upon rehydration. The cell growth and viability studies using human cancer cells revealed noncytotoxic properties of the (PVPON/TA) multilayer particles. Both spherical and hemispherical capsules were internalized by macrophages with the uptake of the hemispherical particles per cell two times more efficient. The method presented here allows for a robust preparation of biocompatible shaped particles whose shape and dimensions can be easily tuned by controlling capsule size and wall thickness. The reported structures can be potentially useful for biomedical applications such as shape-controlled cellular uptake and flow dynamics.

  18. Strength and Fracture Behavior of a Particle-Reinforced Transformation-Toughened Trip Steel/ZrO2 Composite

    NASA Astrophysics Data System (ADS)

    Eckner, R.; Krampf, M.; Segel, C.; Krüger, L.

    2016-01-01

    A newly developed particle-reinforced composite based on a high-alloy metastable CrMnNi TRIP steel was investigated concerning its fracture toughness behavior. The particle reinforcement was done using 10 vol.% of metastable MgO-partially-stabilized ZrO 2 (Mg-PSZ), which has the capability of a stress-induced transformation from the tetragonal to the monoclinic phase. Moreover, the alloying concept of the steel matrix enables a strain-induced transformation from the metastable γ-austenite phase to the α'-martensite phase leading to an increase in strength and ductility. Both effects in combination are intended to dissipate energy and increase the fracture toughness of the composite material (R-curve behavior). To evaluate the mechanical performance of the composite, tensile and fracture mechanics tests according to ISO 12135 were performed, followed by microstructural investigations. The fracture process was analyzed in an in situ tensile test with simultaneous recording of SEM micrographs and subsequent optical analysis of deformation. The results obtained show that the toughness of the composite is primarily determined by the presence of reinforcement particles. The low interfacial strength between the steel and ceramic associated with small interparticle spaces leads to an accelerated fracture process and a low overall toughness. This behavior is amplified as soon as particle clusters are formed during processing.

  19. Influence of ECAP temperature on the formability of a particle reinforced 2017 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Wagner, S.; Härtel, M.; Frint, P.; F-X Wagner, M.

    2017-03-01

    Severe plastic deformation methods are commonly used to increase the strength of materials by generating ultrafine-grained microstructures. The application of these methods to Al-Cu alloys is, however, difficult because of their poor formability at room temperature. An additional reduction of formability of such alloys occurs when ceramic particles are added as reinforcement: this often triggers shear localization and crack initiation during ECAP. This is the main reason why equal-channel angular pressing (ECAP) of aluminum matrix composites (AMCs) can generally only be performed at elevated temperatures and using ECAP dies with a channel angle larger than 90° (e.g. 120°). In this study we present a brief first report on an alternative approach for the improvement of the formability of an AMC (AA2017, 10 % SiC): ECAP at low temperatures. We show that, using a temperature of -60 °C and a channel angle of 90° (corresponding to an equivalent strain of 1.1), ECAP of the AMC can be successfully performed without material failure. The mechanical properties of the strongly deformed AMC are analyzed by tensile testing. Our results indicate that the increased formability of the AMC at low temperatures can be attributed to the suppression of unstable plastic flow that affects formability at room temperature.

  20. Evaluation of the Technical-Economic Potential of Particle- Reinforced Aluminum Matrix Composites and Electrochemical Machining

    NASA Astrophysics Data System (ADS)

    Schubert, A.; Götze, U.; Hackert-Oschätzchen, M.; Lehnert, N.; Herold, F.; Meichsner, G.; Schmidt, A.

    2016-03-01

    Compared to conventional cutting, the processing of materials by electrochemical machining offers some technical advantages like high surface quality, no thermal or mechanical impact on the work piece and preservation of the microstructure of the work piece material. From the economic point of view, the possibility of process parallelization and the absence of any process-related tool wear are mentionable advantages of electrochemical machining. In this study, based on experimental results, it will be evaluated to what extent the electrochemical machining is technically and economically suitable for the finish-machining of particle- reinforced aluminum matrix composites (AMCs). Initial studies showed that electrochemical machining - in contrast to other machining processes - has the potential to fulfil demanding requirements regarding precision and surface quality of products or components especially when applied to AMCs. In addition, the investigations show that processing of AMCs by electrochemical machining requires less energy than the electrochemical machining of stainless steel. Therefore, an evaluation of electrochemically machined AMCs - compared to stainless steel - from a technical and an economic perspective will be presented in this paper. The results show the potential of electro-chemically machined AMCs and contribute to the enhancement of instruments for technical-economic evaluations as well as a comprehensive innovation control.

  1. Effect of Home Bleaching on Microleakage of Fiber-reinforced and Particle-filled Composite Resins

    PubMed Central

    Sharafeddin, Farahnaz; Zare, Samira; Javnmardi, Zahra

    2013-01-01

    Background and aims. Bleaching may exert some negative effects on existing composite resin restorations. The aim of this study was to evaluate the effect of home bleaching on microleakage of fiber-reinforced and particle-filled composite resins. Materials and methods. Ninety class V cavities (1.5×2×3 mm) were prepared on the buccal surfaces of 90 bovine teeth. The teeth were randomly divided into 6 groups (n=15) and restored as follows: Groups 1 and 2 with Z100, groups 3 and 4 with Z250, and groups 5 and 6 with Nulite F composite resins. All the specimens were thermocycled. Groups 1, 3 and 5 were selected as control groups (without bleaching) and the experimental groups 2, 4 and 6 were bleached with 22% carbamide peroxide gel. All the samples were immersed in 2% basic fuchsin dye for 24 hours and then sectioned longitudinally. Dye penetration was evaluated under a stereomicroscope (×25), at both the gingival and incisal margins. Data were analyzed using Kruskal-Wallis, Mann-Whitney and Wilcoxon tests (a=0.05). Results. Statistical analyses revealed that bleaching gel increased microleakage only at gingival margins with Z250 (P=0.007). Moreover, the control groups showed a statistically significant difference in microleakage at their gingival margins. Nulite F had the maximum microleakage while Z250 showed the minimum (P=0.006). Conclusion. Microleakage of home-bleached restorations might be related to the type of composite resin used. PMID:24578819

  2. Scalable plasticized polymer electrolytes reinforced with surface-modified sepiolite fillers - A feasibility study in lithium metal polymer batteries

    NASA Astrophysics Data System (ADS)

    Mejía, Alberto; Devaraj, Shanmukaraj; Guzmán, Julio; Lopez del Amo, Juan Miguel; García, Nuria; Rojo, Teófilo; Armand, Michel; Tiemblo, Pilar

    2016-02-01

    Electrochemical properties of (polyethylene oxide) (PEO)/lithium trifluoromethanesulfonate (LiTf)/ethylene carbonate (EC)/sepiolite extruded composite electrolytes were studied. Appreciable electrochemical stability of 4.5 V at 70 °C was observed for polymer composite membranes with D-α-tocopherol-polyethylene glycol 1000 succinate-coated sepiolite fillers. Lithium plating/stripping analysis indicated no evidence of dendrite formation with good interfacial properties which were further confirmed by postmortem analysis of the cells. Solid state NMR studies show the presence of two Li+ population in the membranes. The feasibility of these electrolytes has been shown with LiFePO4 cathode materials. Initial discharge capacity of 142 mAh/g was observed remaining at 110 mAh/g after 25 cycles with a coulombic efficiency of 96%. The upscaling of these polymers can be easily achieved by extrusion technique and the capacity can be improved by varying the cathode architecture.

  3. Strain measurement in a concrete beam by use of the Brillouin-scattering-based distributed fiber sensor with single-mode fibers embedded in glass fiber reinforced polymer rods and bonded to steel reinforcing bars.

    PubMed

    Zeng, Xiaodong; Bao, Xiaoyi; Chhoa, Chia Yee; Bremner, Theodore W; Brown, Anthony W; DeMerchant, Michael D; Ferrier, Graham; Kalamkarov, Alexander L; Georgiades, Anastasis V

    2002-08-20

    The strain measurement of a 1.65-m reinforced concrete beam by use of a distributed fiber strain sensor with a 50-cm spatial resolution and 5-cm readout resolution is reported. The strain-measurement accuracy is +/-15 microepsilon (microm/m) according to the system calibration in the laboratory environment with non-uniform-distributed strain and +/-5 microepsilon with uniform strain distribution. The strain distribution has been measured for one-point and two-point loading patterns for optical fibers embedded in pultruded glass fiber reinforced polymer (GFRP) rods and those bonded to steel reinforcing bars. In the one-point loading case, the strain deviations are +/-7 and +/-15 microepsilon for fibers embedded in the GFRP rods and fibers bonded to steel reinforcing bars, respectively, whereas the strain deviation is +/-20 microepsilon for the two-point loading case.

  4. Feasibility study: Monodisperse polymer particles containing laser-excitable dyes

    NASA Technical Reports Server (NTRS)

    Vanderhoff, John W.; Chen, Jing-Hong

    1993-01-01

    The objective was to determine the feasibility of the preparation of monodisperse spherical poly(methyl methacrylate) and polystyrene particles that contain laser-excitable dyes in the size range 0.1 microns to 1 cm. Poly(methyl methacrylate) and polystyrene were chosen because of their excellent optical properties. The sphericity was required for uniformity of spectral output of re-irradiated light from the dye-containing particles. The monodispersity was required to give each particle the same optical properties when exposed to laser light.

  5. Impact of small changes in particle surface chemistry for unentangled polymer nanocomposites.

    PubMed

    Ranka, Moulik; Varkey, Nihal; Ramakrishnan, Subramanian; Zukoski, Charles F

    2015-02-28

    We report microstructural and rheological consequences of altering silica particle surface chemistry when the particles are suspended in unentangled polyethylene glycol with a molecular weight of 400. The particle surfaces are altered by reacting them with isobutyltrimethyoxysilane. Levels of silanization are chosen so that the particles remain dispersed in the polymer at all volume fractions studied. Our studies indicate that at the levels studied, silanization does not alter the hydrodynamic thickness of the absorbed polymer layer thickness. Rheological properties are not sensitive to levels of silanization up to particle volume fractions where the average particle separation h ∼ 6Rg (4.8 nm). At these volume fractions, composite microstructure undergoes changes associated with jamming of soft particles (decorrelations in the first peak of the particle structure factor and the onset of a non-diffusive mechanism that dominates particle density fluctuations at short times.) In the region of volume fractions where h/Rg < 6, the zero-shear rate viscosity of the composites is extremely sensitive to level of silanization with a decrease in the zero-shear rate viscosity by four orders of magnitude observed for the highest levels of silanization studied in comparison to the bare particles.

  6. Electrical conductivity, dielectric response and space charge dynamics of an electroactive polymer with and without nanofiller reinforcement

    NASA Astrophysics Data System (ADS)

    Kochetov, R.; Tsekmes, I. A.; Morshuis, P. H. F.

    2015-07-01

    Electroactive polymers have gained considerable attention over the last 20 years for exhibiting a large displacement in response to electrical stimulation. The promising fields of application include wave energy converters, muscle-like actuators, sensors, robotics, and biomimetics. For an electrical engineer, electroactive polymers can be seen as a dielectric elastomer film or a compliant capacitor with a highly deformable elastomeric medium. If the elastomer is pre-stretched and pre-charged, a reduction of the tensile force lets the elastomer revert to its original form and increases the electrical potential. The light weight of electroactive polymers, low cost, high intrinsic breakdown strength, cyclical way of operation, reliable performance, and high efficiency can be exploited to utilize the elastomeric material as a transducer. The energy storage for a linear dielectric polymer is determined by its relative permittivity and the applied electric field. The latter is limited by the dielectric breakdown strength of the material. Therefore, to generate a high energy density of a flexible capacitor, the film must be used at the voltage level close to the material’s breakdown or inorganic particles with high dielectric permittivity which can be introduced into the polymer matrix. In the present study, silicone-titania elastomer nanocomposites were produced and the influence of nanoparticles on the macroscopic dielectric properties of the neat elastomer including space charge dynamics, complex permittivity, and electrical conductivity, were investigated.

  7. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various continuous fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermooxidative stability of PMR-15 composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers studied include graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight-loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  8. Beads on a string: structure of bound aggregates of globular particles and long polymer chains.

    PubMed

    Souslov, Anton; Curtis, Jennifer E; Goldbart, Paul M

    2015-11-07

    Macroscopic properties of suspensions, such as those composed of globular particles (e.g., colloidal or macromolecular), can be tuned by controlling the equilibrium aggregation of the particles. We examine how aggregation - and, hence, macroscopic properties - can be controlled in a system composed of both globular particles and long, flexible polymer chains that reversibly bind to one another. We base this on a minimal statistical mechanical model of a single aggregate in which the polymer chain is treated either as ideal or self-avoiding, and, in addition, the globular particles are taken to interact with one another via excluded volume repulsion. Furthermore, each of the globular particles is taken to have one single site to which at most one polymer segment may bind. Within the context of this model, we examine the statistics of the equilibrium size of an aggregate and, thence, the structure of dilute and semidilute suspensions of these aggregates. We apply the model to biologically relevant aggregates, specifically those composed of macromolecular proteoglycan globules and long hyaluronan polymer chains. These aggregates are especially relevant to the materials properties of cartilage and the structure-function properties of perineuronal nets in brain tissue, as well as the pericellular coats of mammalian cells.

  9. Dissipative particle dynamics simulations of polymer-protected nanoparticle self-assembly

    NASA Astrophysics Data System (ADS)

    Spaeth, Justin R.; Kevrekidis, Ioannis G.; Panagiotopoulos, Athanassios Z.

    2011-11-01

    Dissipative particle dynamics simulations were used to study the effects of mixing time, solute solubility, solute and diblock copolymer concentrations, and copolymer block length on the rapid coprecipitation of polymer-protected nanoparticles. The simulations were aimed at modeling Flash NanoPrecipitation, a process in which hydrophobic solutes and amphiphilic block copolymers are dissolved in a water-miscible organic solvent and then rapidly mixed with water to produce composite nanoparticles. A previously developed model by Spaeth et al. [J. Chem. Phys. 134, 164902 (2011)], 10.1063/1.3580293 was used. The model was parameterized to reproduce equilibrium and transport properties of the solvent, hydrophobic solute, and diblock copolymer. Anti-solvent mixing was modeled using time-dependent solvent-solute and solvent-copolymer interactions. We find that particle size increases with mixing time, due to the difference in solute and polymer solubilities. Increasing the solubility of the solute leads to larger nanoparticles for unfavorable solute-polymer interactions and to smaller nanoparticles for favorable solute-polymer interactions. A decrease in overall solute and polymer concentration produces smaller nanoparticles, because the difference in the diffusion coefficients of a single polymer and of larger clusters becomes more important to their relative rates of collisions under more dilute conditions. An increase in the solute-polymer ratio produces larger nanoparticles, since a collection of large particles has less surface area than a collection of small particles with the same total volume. An increase in the hydrophilic block length of the polymer leads to smaller nanoparticles, due to an enhanced ability of each polymer to shield the nanoparticle core. For unfavorable solute-polymer interactions, the nanoparticle size increases with hydrophobic block length. However, for favorable solute-polymer interactions, nanoparticle size exhibits a local minimum with

  10. Dispersion and Reinforcement of Nanotubes in High Temperature Polymers for Ultrahigh Strength and Thermally Conductive Nanocomposites

    DTIC Science & Technology

    2007-10-03

    SWNT [35,36], polypropylene/nano-carbon fiber , polystyrene (PS)/MWNT [34,43] and in-situ polymerization of PI/SWNT [38]) in polymer matrices to...strength and thermal/electric conductivity based on soft macromolecules of controlled glass transition temperature. 1.4.1 The Polybenzoxazoles (PBO...around 270 GPa, greater than that of steel fibers . PBO had been developed by US Air Force researchers as a super heat resistant polymer that surpasses

  11. The Prediction and Simulation for the Mechanical Properties of Ceramic-Based Composites Reinforced with Nano-Micro Particles

    SciTech Connect

    Luo Dongmei; Hu Jinshan; Yang Hong; Zhou Yinglong

    2010-05-21

    The global-local homogenization method with precise period boundary conditions is applied to predict and simulate the mechanical properties of ceramic composites reinforced by spherical nano-micro particles with enwrapping and nesting arrays. The numerical simulation is performed with different size ratios of nano-micro particles, and different configurations for representative volume element. The results show that the low radius ratios of nano-micro particles produce a larger effective Young's modulus for its more uniform dispersion, and the hexagon RVE with nesting array can make an overestimation for effective elastic modulus of ceramic composites, and the interfacial damage between nano-microscopic particles and matrix degenerates the effective elastic modulus. It shows in this paper that it is significant to improve the mechanical properties of ceramic materials by mixing some nano- and micro-particles into the matrix with good designed array methods from the viewpoints of nano-microscopic crystal structure, and a rational interfacial damage model should be further proposed to investigate the toughening mechanism of ceramic-composites reinforced with nano-micro particles.

  12. Effects of Incorporating Nanosized Calcium Phosphate Particles on Properties of Whisker-Reinforced Dental Composites

    PubMed Central

    Xu, Hockin H. K.; Sun, Limin; Weir, Mike D.; Takagi, Shozo; Chow, Laurence C.; Hockey, Bernard

    2009-01-01

    Clinical data indicate that secondary caries and restoration fracture are the most common problems facing tooth restorations. Our ultimate goal was to develop mechanically-strong and caries-inhibiting dental composites. The specific goal of this pilot study was to understand the relationships between composite properties and the ratio of reinforcement filler/releasing filler. Nanoparticles of monocalcium phosphate monohydrate (MCPM) were synthesized and incorporated into a dental resin for the first time. Silicon carbide whiskers were fused with silica nanoparticles and mixed with the MCPM particles at MCPM/whisker mass ratios of 1:0, 2:1, 1:1, 1:2, and 0:1. The composites were immersed for 1–56 days to measure Ca and PO4 release. When the MCPM/whisker ratio was changed from 0:1 to 1:2, the composite flexural strength (mean ± SD; n = 5) decreased from 174 ± 26 MPa to 138 ± 9 MPa (p < 0.05). A commercial nonreleasing composite had a strength of 112 ± 14 MPa. When the MCPM/whisker ratio was changed from 1:2 to 1:1, the Ca concentration at 56 days increased from 0.77 ± 0.04 mmol/L to 1.74 ± 0.06 mmol/L (p < 0.05). The corresponding PO4 concentration increased from 3.88 ± 0.21 mmol/L to 9.95 ± 0.69 mmol/L (p < 0.05). Relationships were established between the amount of release and the MCPM volume fraction vMCPM in the resin: [Ca]= 42.9 vMCPM2.7, and [PO4] = 48.7 vMCPM1.4. In summary, the method of combining nanosized releasing fillers with reinforcing fillers yielded Ca- and PO4-releasing composites with mechanical properties matching or exceeding a commercial stress-bearing, nonreleasing composite. This method may be applicable to the use of other Ca–PO4 fillers in developing composites with high stress-bearing and caries-preventing capabilities, a combination not yet available in any dental materials. PMID:16924611

  13. Canonical free-energy barrier of particle and polymer cluster formation

    NASA Astrophysics Data System (ADS)

    Zierenberg, Johannes; Schierz, Philipp; Janke, Wolfhard

    2017-02-01

    A common approach to study nucleation rates is the estimation of free-energy barriers. This usually requires knowledge about the shape of the forming droplet, a task that becomes notoriously difficult in macromolecular setups starting with a proper definition of the cluster boundary. Here we demonstrate a shape-free determination of the free energy for temperature-driven cluster formation in particle as well as polymer systems. Combined with rigorous results on equilibrium droplet formation, this allows for a well-defined finite-size scaling analysis of the effective interfacial free energy at a fixed density. We first verify the theoretical predictions for the formation of a liquid droplet in a supersaturated particle gas by generalized-ensemble Monte Carlo simulations of a Lennard-Jones system. Going one step further, we then generalize this approach to cluster formation in a dilute polymer solution. Our results suggest an analogy with particle condensation, when the macromolecules are interpreted as extended particles.

  14. A single particle model to simulate the dynamics of entangled polymer melts

    NASA Astrophysics Data System (ADS)

    Kindt, P.; Briels, W. J.

    2007-10-01

    We present a computer simulation model of polymer melts representing each chain as one single particle. Besides the position coordinate of each particle, we introduce a parameter nij for each pair of particles i and j within a specified distance from each other. These numbers, called entanglement numbers, describe the deviation of the system of ignored coordinates from its equilibrium state for the given configuration of the centers of mass of the polymers. The deviations of the entanglement numbers from their equilibrium values give rise to transient forces, which, together with the conservative forces derived from the potential of mean force, govern the displacements of the particles. We have applied our model to a melt of C800H1602 chains at 450K and have found good agreement with experiments and more detailed simulations. Properties addressed in this paper are radial distribution functions, dynamic structure factors, and linear as well as nonlinear rheological properties.

  15. Dependence of the degree of reinforcement of polymer/carbon nanotubes nanocomposites on the nanofiller dimension

    NASA Astrophysics Data System (ADS)

    Mikitaev, A. K.; Kozlov, G. V.

    2015-05-01

    The dependence of the degree of reinforcement of polymethylmethacrylate/carbon nanotubes on the nanofiller content at ultrasmall concentrations of the latter is investigated. It is shown that the extreme character of this dependence is determined by the structural features of the nanofiller. Functionalization of carbon nanotubes gives a positive effect only below their percolation threshold.

  16. Fluorescent protein senses and reports mechanical damage in glass-fiber-reinforced polymer composites.

    PubMed

    Makyła, Katarzyna; Müller, Christoph; Lörcher, Samuel; Winkler, Thomas; Nussbaumer, Martin G; Eder, Michaela; Bruns, Nico

    2013-05-21

    Yellow fluorescent protein (YFP) is used as a mechanoresponsive layer at the fiber/resin interface in glass-fiber-reinforced composites. The protein loses its fluorescence when subjected to mechanical stress. Within the material, it reports interfacial shear debonding and barely visible impact damage by a transition from a fluorescent to a non-fluorescent state.

  17. Reinforcement effect of soy protein/carbohydrate ratio in styrene-butadiene polymer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soy protein and carbohydrate at different ratios were blended with latex to form composites. The variation of protein to carbohydrate ratio has a sifnificant effect on the composite properties and the results from dynamic mechanical method showed a substantial reinforcement effect. The composites ...

  18. Mineral-Ground Micro-Fibrillated Cellulose Reinforcement for Polymer Compounds

    SciTech Connect

    Phipps, Jon; Ireland, Sean; Skuse, David; Edwards, Martha; Mclain, Leslie; Tekinalp, Halil L.; Love, Lonnie J.; Kunc, Vlastimil; Ozcan, Soydan

    2017-01-01

    ORNL worked with Imerys to demonstrate reinforcement of additive manufacturing feedstock materials using mineral-ground microfibrillated cellulose (MFC). Properly prepared/dried mineral-ground cellulose microfibrils significantly improved mechanical properties of both ABS and PLA resins. While tensile strength increases up to ~40% were observed, elastic modulus of the both resins doubled with the addition of 30% MFC.

  19. Effect of monomer composition of polymer matrix on flexural properties of glass fibre-reinforced orthodontic archwire.

    PubMed

    Ohtonen, J; Vallittu, P K; Lassila, L V J

    2013-02-01

    To compare force levels obtained from glass fibre-reinforced composite (FRC) archwires. Specifically, FRC wires were compared with polymer matrices having different dimethacrylate monomer compositions. FRC material (E-glass provided by Stick Tech Ltd, Turku, Finland) with continuous unidirectional glass fibres and four different types of dimethacrylate monomer compositions for the resin matrix were tested. Cross-sectionally round FRC archwires fitting into the 0.3 mm slot of a bracket were divided into 16 groups with six specimens in each group. Glass fibres were impregnated by the manufacturer, and they were initially light-cured by hand light-curing unit or additionally post-cured in light-curing oven. The FRC archwire specimens were tested at 37°C according to a three-point bending test in dry and wet conditions using a span length of 10 mm and a crosshead speed of 1.0 mm/minute. The wires were loaded until final failure. The data were statistically analysed using analysis of variance (ANOVA). The dry FRC archwire specimens revealed higher load values than water stored ones, regardless of the polymer matrix. A majority of the FRC archwires showed higher load values after being post-cured. ANOVA revealed that the polymer matrix, curing method, and water storage had a significant effect (P < 0.05) on the flexural behaviour of the FRC archwire. Polymer matrix composition, curing method, and water storage affected the flexural properties and thus, force level and working range which could be obtained from the FRC archwire.

  20. Polymer latex particles: Preparation, characterization, and coating patterns

    SciTech Connect

    Wang, Leeyih.

    1993-01-01

    The coating patterns of polystyrene latex after spin drying have been intensively investigated. The model microsphere was prepared using emulsifier-free emulsion polymerization. The resulting polystyrene latex was 0.54 [mu]m in diameter with the polydispersity of 1.02. The mobility of latex spheres in concentrated dispersions was studied by diffusing wave spectroscopy (DWS). The diffusion coefficient of the polystyrene spheres dispersed in water decreased as the concentration of latex particles increased. The concentration dependence of the diffusion coefficient of this latex determined by DWS matched closely to the short-time diffusion of poly(methyl methacrylate) latex in a mixed organic fluid determined by PCS using the refractive index matching method. It indicates that the electrical repulsive force between particles in this system has a small effect on the short-time mobility of particles. This result was also confirmed by the diffusion coefficients of polystyrene spheres dispersed in water with the addition of sodium chloride, or dispersed in NMF. The presence of surfactants, SDS and C12E5, in the dispersed medium led to a great reduction on the diffusivity of latex spheres. A two dimensional ordered array of particles can be obtained from the spin drying of polystyrene latex by adding surfactants in a suitable concentration range or by choosing an appropriate substrate and/or dispersing fluid. A mechanism for the formation of hexagonally packed particles was proposed as the actions of three factors: retractive, frictional, and capillary forces.

  1. A Comparison of the Elastic Properties of Graphene- and Fullerene-Reinforced Polymer Composites: The Role of Filler Morphology and Size

    NASA Astrophysics Data System (ADS)

    Lu, Chang-Tsan; Weerasinghe, Asanka; Maroudas, Dimitrios; Ramasubramaniam, Ashwin

    2016-08-01

    Nanoscale carbon-based fillers are known to significantly alter the mechanical and electrical properties of polymers even at relatively low loadings. We report results from extensive molecular-dynamics simulations of mechanical testing of model polymer (high-density polyethylene) nanocomposites reinforced by nanocarbon fillers consisting of graphene flakes and fullerenes. By systematically varying filler concentration, morphology, and size, we identify clear trends in composite stiffness with reinforcement. To within statistical error, spherical fullerenes provide a nearly size-independent level of reinforcement. In contrast, two-dimensional graphene flakes induce a strongly size-dependent response: we find that flakes with radii in the 2-4 nm range provide appreciable enhancement in stiffness, which scales linearly with flake radius. Thus, with flakes approaching typical experimental sizes (~0.1-1 μm), we expect graphene fillers to provide substantial reinforcement, which also is much greater than what could be achieved with fullerene fillers. We identify the atomic-scale features responsible for this size- and morphology-dependent response, notably, ordering and densification of polymer chains at the filler-matrix interface, thereby providing insights into avenues for further control and enhancement of the mechanical properties of polymer nanocomposites.

  2. A Comparison of the Elastic Properties of Graphene- and Fullerene-Reinforced Polymer Composites: The Role of Filler Morphology and Size

    PubMed Central

    Lu, Chang-Tsan; Weerasinghe, Asanka; Maroudas, Dimitrios; Ramasubramaniam, Ashwin

    2016-01-01

    Nanoscale carbon-based fillers are known to significantly alter the mechanical and electrical properties of polymers even at relatively low loadings. We report results from extensive molecular-dynamics simulations of mechanical testing of model polymer (high-density polyethylene) nanocomposites reinforced by nanocarbon fillers consisting of graphene flakes and fullerenes. By systematically varying filler concentration, morphology, and size, we identify clear trends in composite stiffness with reinforcement. To within statistical error, spherical fullerenes provide a nearly size-independent level of reinforcement. In contrast, two-dimensional graphene flakes induce a strongly size-dependent response: we find that flakes with radii in the 2–4 nm range provide appreciable enhancement in stiffness, which scales linearly with flake radius. Thus, with flakes approaching typical experimental sizes (~0.1–1 μm), we expect graphene fillers to provide substantial reinforcement, which also is much greater than what could be achieved with fullerene fillers. We identify the atomic-scale features responsible for this size- and morphology-dependent response, notably, ordering and densification of polymer chains at the filler–matrix interface, thereby providing insights into avenues for further control and enhancement of the mechanical properties of polymer nanocomposites. PMID:27546738

  3. Thermal diffusivity of Al-Mg based metallic matrix composite reinforced with Al2O3 ceramic particles

    NASA Astrophysics Data System (ADS)

    Cruz-Orea, A.; Morales, J. E.; Saavedra S, R.; Carrasco, C.

    2010-03-01

    Thermal diffusivities of Al-Mg based metallic matrix composite reinforced with ceramic particles of Al2O3 are reported in this article. The samples were produced by rheocasting and the studied operational condition in this case is the shear rate: 800, 1400 and 2000 rpm. Additionally, the AlMg base alloy was tested. Measurements of thermal diffusivity were performed at room temperature by using photoacoustic technique.

  4. Physical and Mechanical Properties of LoVAR: A New Lightweight Particle-Reinforced Fe-36Ni Alloy

    NASA Technical Reports Server (NTRS)

    Stephenson, Timothy; Tricker, David; Tarrant, Andrew; Michel, Robert; Clune, Jason

    2015-01-01

    Fe-36Ni is an alloy of choice for low thermal expansion coefficient (CTE) for optical, instrument and electrical applications in particular where dimensional stability is critical. This paper outlines the development of a particle-reinforced Fe-36Ni alloy that offers reduced density and lower CTE compared to the matrix alloy. A summary of processing capability will be given relating the composition and microstructure to mechanical and physical properties.

  5. Nanoscale indentation of polymer and composite polymer-silica core-shell submicrometer particles by atomic force microscopy.

    PubMed

    Armini, Silvia; Vakarelski, Ivan U; Whelan, Caroline M; Maex, Karen; Higashitani, Ko

    2007-02-13

    Atomic force microscopy was employed to probe the mechanical properties of surface-charged polymethylmethacrylate (PMMA)-based terpolymer and composite terpolymer core-silica shell particles in air and water media. The composite particles were achieved with two different approaches: using a silane coupling agent (composite A) or attractive electrostatic interactions (composite B) between the core and the shell. Young's moduli (E) of 4.3+/-0.7, 11.1+/-1.7, and 8.4+/-1.7 GPa were measured in air for the PMMA-based terpolymer, composite A, and composite B, respectively. In water, E decreases to 1.6+/-0.2 GPa for the terpolymer; it shows a slight decrease to 8.0+/-1.2 GPa for composite A, while it decreases to 2.9+/-0.6 GPa for composite B. This trend is explained by considering a 50% swelling of the polymer in water confirmed by dynamic light scattering. Close agreement is found between the absolute values of elastic moduli determined by nanoindentation and known values for the corresponding bulk materials. The thickness of the silica coating affects the mechanical properties of composite A. In the case of composite B, because the silica shell consists of separate particles free to move in the longitudinal direction that do not individually deform when the entire composite deforms, the elastic properties of the composites are determined exclusively by the properties of the polymer core. These results provide a basis for tailoring the mechanical properties of polymer and composite particles in air and in solution, essential in the design of next-generation abrasive schemes for several technological applications.

  6. Diagnostics of glass fiber reinforced polymers and comparative analysis of their fabrication techniques with the use of acoustic emission

    NASA Astrophysics Data System (ADS)

    Bashkov, O. V.; Bryansky, A. A.; Panin, S. V.; Zaikov, V. I.

    2016-11-01

    Strength properties of the glass fiber reinforced polymers (GFRP) fabricated by vacuum and vacuum autoclave molding techniques were analyzed. Measurements of porosity of the GFRP parts manufactured by various molding techniques were conducted with the help of optical microscopy. On the basis of experimental data obtained by means of acoustic emission hardware/software setup, the technique for running diagnostics and forecasting the bearing capacity of polymeric composite materials based on the result of three-point bending tests has been developed. The operation principle of the technique is underlined by the evaluation of the power function index change which takes place on the dependence of the total acoustic emission counts versus the loading stress.

  7. Polymer blend of PLA/PHBV based bionanocomposites reinforced with nanocrystalline cellulose for potential application as packaging material.

    PubMed

    Dasan, Y K; Bhat, A H; Ahmad, Faiz

    2017-02-10

    The current research discusses the development of poly (lactic acid) (PLA) and poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforced nanocrystalline cellulose bionanocomposites. The nanocrystalline cellulose was derived from waste oil palm empty fruit bunch fiber by acid hydrolysis process. The resulting nanocrystalline cellulose suspension was then surface functionalized by TEMPO-mediated oxidation and solvent exchange process. Furthermore, the PLA/PHBV/nanocrystalline cellulose bionanocomposites were produced by solvent casting method. The effect of the addition of nanocrystalline cellulose on structural, morphology, mechanical and barrier properties of bionanocomposites was investigated. The results revealed that the developed bionanocomposites showed improved mechanical properties and decrease in oxygen permeability rate. Therefore, the developed bio-based composite incorporated with an optimal composition of nanocrystalline cellulose exhibits properties as compared to the polymer blend.

  8. Prestressing Effects on the Performance of Concrete Beams with Near-surface-mounted Carbon-fiber-reinforced Polymer Bars

    NASA Astrophysics Data System (ADS)

    Hong, Sungnam; Park, Sun-Kyu

    2016-07-01

    The effects of various prestressing levels on the flexural behavior of concrete beams strengthened with prestressed near-surface-mounted (NSM) carbon-fiber-reinforced polymer (CFRP) bars were investigated in this study. Four-point flexural tests up to failure were performed using a total of six strengthened prestressed and nonprestressed concrete beams. The nonprestressed strengthened beam failed by premature debonding at the interface of concrete and the epoxy adhesive, but the prestressed one failed owing due to rupture of the CFRP bar. As the prestressing level of the CFRP bar increased, the cracking and yield loads of the prestressed beams increased, but its effect on their deflections was insignificant. The ultimate load was constant regardless of prestressing level, but the ultimate deflection was almost inversely proportional to the level.

  9. Effect of asperity-scale tensile stresses on the wear behavior of normally oriented fiber-reinforced polymer composites

    SciTech Connect

    Wu, J.P.; Ovaert, T.C.

    1994-01-01

    Wear of unidirectional continuous fiber-reinforced polymer composites with fiber orientation normal to the contact plane, sliding over scribed stainless steel disks having a controlled surface topography, is investigated in relation to the tensile stresses developed near the contact region. The composite is modeled as a transversely isotropic half-space whose effective elastic moduli are estimated from composite micro-mechanical considerations. The scribed disk is treated as a rough surface whose controlled topographical features serve as model hemispherical indenters against the composite. With friction coefficients obtained from the wear experiments, the tensile stress field at an below the composite surface is estimated. From this, an estimated of the theoretical depth of fiber-matrix separation (fiber debonding) is calculated based on the composite transverse tensile strength. A correlation between the wear rate and theoretical depth of debonding was shown for several composites.

  10. Prediction of elastic properties for polymer-particle nanocomposites exhibiting an interphase.

    PubMed

    Deng, Fei; Van Vliet, Krystyn J

    2011-04-22

    Particle-polymer nanocomposites often exhibit mechanical properties described poorly by micromechanical models that include only the particle and matrix phases. Existence of an interfacial region between the particle and matrix, or interphase, has been posited and indirectly demonstrated to account for this effect. Here, we present a straightforward analytical approach to estimate effective elastic properties of composites comprising particles encapsulated by an interphase of finite thickness and distinct elastic properties. This explicit solution can treat nanocomposites that comprise either physically isolated nanoparticles or agglomerates of such nanoparticles; the same framework can also treat physically isolated nanoparticle aggregates or agglomerates of such aggregates. We find that the predicted elastic moduli agree with experiments for three types of particle-polymer nanocomposites, and that the predicted interphase thickness and stiffness of carbon black-rubber nanocomposites are consistent with measured values. Finally, we discuss the relative influence of the particle-polymer interphase thickness and stiffness to identify maximum possible changes in the macroscale elastic properties of such materials.

  11. Physical Methods for the Preparation of Hybrid Nanocomposite Polymer Latex Particles

    NASA Astrophysics Data System (ADS)

    Teixeira, Roberto F. A.; Bon, Stefan A. F.

    In this chapter, we will highlight conceptual physical approaches towards the fabrication of nanocomposite polymer latexes in which each individual latex particle contains one or more "hard" nanoparticles, such as clays, silicates, titanates, or other metal(oxides). By "physical approaches" we mean that the "hard" nanoparticles are added as pre-existing entities, and are not synthesized in situ as part of the nanocomposite polymer latex fabrication process. We will narrow our discussion to focus on physical methods that rely on the assembly of nanoparticles onto the latex particles after the latex particles have been formed, or its reciprocal analogue, the adhesion of polymer onto an inorganic nanoparticle. First, will discuss the phenomenon of heterocoagulation and its various driving forces, such as electrostatic interactions, the hydrophobic effect, and secondary molecular interactions. We will then address methods that involve assembly of nanoparticles onto or around the more liquid precursors (i.e., swollen/growing latex particles or monomer droplets). We will focus on the phenomenon of Pickering stabilization. We will then discuss features of particle interaction with soft interfaces, and see how the adhesion of particles onto emulsion droplets can be applied in suspension, miniemulsion, and emulsion polymerization. Finally, we will very briefly mention some interesting methods that make use of interface-driven templating for making well-defined assembled clusters and supracolloidal structures.

  12. Evaluation of two matrix materials intended for fiber-reinforced polymers.

    PubMed

    Segerström, Susanna; Meriç, Gökçe; Knarvang, Torbjørn; Ruyter, I Eystein

    2005-10-01

    Two matrix resins for fiber composites that remain in a fluid state during storage and handling before polymerization were evaluated. The resin mixtures, based on methyl methacrylate (MMA), were produced with two different cross-linking agent systems: 1,4-butanediol dimethacrylate and ethylene glycol dimethacrylate or diethylene glycol dimethacrylate. Water sorption, water solubility, water uptake and residual MMA monomer were determined. Thermomechanical analysis was used to determine linear dimensional changes as a function of temperature. Flexural strength and modulus as well as fracture work and the maximum stress intensity factor were determined. The results revealed similar values for both matrix polymers regarding water sorption, water solubility, water uptake, residual MMA monomer (0.5 wt% (+/- 0.03)) and coefficient of linear thermal expansion. Flexural strength for polymer B was 68.7 MPa (+/- 9.8) compared to 56.0 MPa (+/- 13.3) for polymer A when tested dry and 64 MPa (+/- 6.1) compared to (54 MPa (+/- 3.3) when water-saturated. Fracture toughness tests showed higher maximum stress intensity factor values for polymer B (0.75 +/- 0.17) MPa x m1/2 than for polymer A (0.55 +/- 0.12) MPa x m1/2. The resin binders showed an appropriate consistency while remaining in a fluid state during storage and manipulation.

  13. Mesoscopic simulation of entanglements using dissipative particle dynamics: application to polymer brushes.

    PubMed

    Goujon, Florent; Malfreyt, Patrice; Tildesley, Dominic J

    2008-07-21

    We use a simple spring-spring repulsion to model entanglements between polymers in dissipative particle dynamics (DPD) simulations. The model is applied to a polymer brushes system to study lubrication. We demonstrate that this method leads to mechanical equilibrium in polymer brushes using the normal DPD time step. The number of bond crossings is calculated to provide a quantitative description of the entanglement. We demonstrate that it is possible to avoid 99% of the bond crossings with the values of spring-spring repulsion that can be used without significantly decreasing the time step. A shear force is applied to the system to study the effect of the decrease in the bond crossings on the structure and rheological properties of the brushes. In particular, we show how the friction coefficient increases with the decrease in the bond crossings of the polymers.

  14. Quantitative study of polymer conformation and dynamics by single-particle tracking.

    PubMed Central

    Qian, H; Elson, E L

    1999-01-01

    We present a new method for analyzing the dynamics of conformational fluctuations of individual flexible polymer molecules. In single-particle tracking (SPT), one end of the polymer molecule is tethered to an immobile substratum. A microsphere attached to the other end serves as an optical marker. The conformational fluctuations of the polymer molecule can be measured by optical microscopy via the motion of the microsphere. The bead-and-spring theory for polymer dynamics is further developed to account for the microsphere, and together the measurement and the theory yield quantitative information about molecular conformations and dynamics under nonperturbing conditions. Applying the method to measurements carried out on DNA molecules provides information complementary to recent studies of single DNA molecules under extensional force. Combining high precision measurements with the theoretical analysis presented here creates a powerful tool for studying conformational dynamics of biological and synthetic macromolecules at the single-molecule level. PMID:10049340

  15. Molecular and structural properties of polymer composites filled with activated charcoal particles

    NASA Astrophysics Data System (ADS)

    Tahir, Dahlang; Liong, Syarifuddin; Bakri, Fahrul

    2016-03-01

    We have studied the molecular properties, structural properties, and chemical composition of composites by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, and X-ray fluorescence (XRF) spectroscopy, respectively. FTIR spectra shows absorption band of hydroxyl group (-OH), methyl group (-CH3) and aromatic group (C-C). The absorption band for aromatic group (C-C) shows the formation of carbonaceous in composites. XRF shows chemical composition of composites, which the main chemicals are SO3, Cl, and ZnO. The loss on ignition value (LOI) of activated charcoal indicates high carbonaceous matter. The crystallite size for diffraction pattern from hydrogel polymer is about 17 nm and for activated charcoal are about 19 nm. The crystallite size of the polymer is lower than that of activated charcoal, which make possible of the particle from filler in contact with each other to form continuous conducting polymer through polymer matrix.

  16. Viscoelastic Properties of Polymer Systems From Dissipative Particle Dynamics Simulations

    DTIC Science & Technology

    2008-11-01

    interacting particles, and t is the time step. Español and Warren (1995) showed that the system samples the canonical ensemble and obeys the...Sloan, J.; Napadensky, E.; Beyer, R.; Snyder, J.; Chung, P. W.; McKnight, S. 25th Army Science Conference, 2006. Español , P.; Warren, P. B

  17. A Facile Synthesis of Dynamic, Shape-Changing Polymer Particles

    DTIC Science & Technology

    2014-04-02

    onion - like” radial morphology.[11,3d] This is due to preferential wetting of one block by the surfactant layer surrounding the dispersed particle. Such...behavior, and nanoparticles with P2VP as the outermost layer of an “inverse onion ” morphol- ogy (Figure 2, and see Figure S-1b in the Supporting Infor

  18. Feasibility study: Monodisperse polymer particles containing laser-excitable dyes

    NASA Technical Reports Server (NTRS)

    Venkateswarlu, Putcha; He, K. X.; Sharma, A.

    1993-01-01

    The optical properties associated with small particles, which include aerosols, hydrosols and solid microspheres have an impact on several areas of science and engineering. Since the advent of high-speed computers and lasers, the interaction of light with matter in the form of small particles with a discontinuous optical boundary relative to the surroundings has been much better understood. Various nonlinear optical effects have been observed involving interaction of a laser beam with both solid microspheres and liquid microdroplets. These include observation of second and third harmonic generation, four wave mixing, optical visibility, two photon absorption, observation of stimulated emission and lasing, and Stimulated Raman Scattering. Many of these effects are observed with laser intensities which are orders of magnitude less than that required by threshold condition for interactions in macroscopic bulk medium. The primary reason for this is twofold. The front surface of the microsphere acts as a thick lens to enhance the internal intensity of the input laser radiation, and the spherical shape of the droplet acts as an optical cavity to provide feedback at specific wavelengths corresponding to the whispering gallery modes or the morphology dependent resonances (MDR's). The most interesting and significant recent finding in this field is undoubtedly the existence of resonance peaks in linear and nonlinear optical spectra. Such resonance peaks are only dependent on the particle morphology, which means the size, shape and refractive index of the particle. Because of the simultaneous presence of these resonances, they have been referred to by many names, including structural resonances, whispering modes or whispering gallery modes, creeping waves, circumferential waves, surfaces modes, and virtual modes. All of these names refer to the same phenomena, i.e. morphology dependent resonances (MDR's) which has already been described and predicted precisely by

  19. An experimental study of non-destructive testing on glass fibre reinforced polymer composites after high velocity impact event

    NASA Astrophysics Data System (ADS)

    Razali, N.; Sultan, M. T. H.; Cardona, F.

    2016-10-01

    A non-destructive testing method on Glass Fibre Reinforced Polymer (GFRP) after high velocity impact event using single stage gas gun (SSGG) is presented. Specimens of C- type and E-type fibreglass reinforcement, which were fabricated with 6mm, 8mm, 10mm and 12mm thicknesses and size 100 mm x 100 mm, were subjected to a high velocity impact with three types of bullets: conical, hemispherical and blunt at various gas gun pressure levels from 6 bar to 60 bar. Visual observation techniques using a lab microscope were used to determine the infringed damage by looking at the crack zone. Dye penetrants were used to inspect the area of damage, and to evaluate internal and external damages on the specimens after impact. The results from visual analysis of the impacted test laminates were discussed and presented. It was found that the impact damage started with induced delamination, fibre cracking and then failure, simultaneously with matrix cracking and breakage, and finally followed by the fibres pulled out. C-type experienced more damaged areas compared to E-type of GFRP.

  20. Microstructure and Mechanical Properties of Cr-SiC Particles-Reinforced Fe-Based Alloy Coating

    NASA Astrophysics Data System (ADS)

    Wang, Fu-cheng; Du, Xiao-dong; Zhan, Ma-ji; Lang, Jing-wei; Zhou, Dan; Liu, Guang-fu; Shen, Jian

    2015-12-01

    In this study, SiC particles were first coated with Cr to form a layer that can protect the SiC particles from dissolution in the molten pool. Then, the Cr-SiC powder was injected into the tail of molten pool during plasma-transferred arc welding process (PTAW), where the temperature was relatively low, to prepare Cr-SiC particles reinforced Fe-based alloy coating. The microstructure and phase composition of the powder and surface coatings were analyzed, and the element distribution and hardness at the interfacial region were also evaluated. The protective layer consists of Cr3Si, Cr7C3, and Cr23C6, which play an important role in the microstructure and mechanical properties. The protective layer is dissolved in the molten pool forming a flocculent region and a transition region between the SiC particles and the matrix. The tribological performance of the coating was also assessed using a ring-block sliding wear tester with GGr15 grinding ring under 490 and 980 N load. Cr-SiC particles-reinforced coating has a lower wear rate than the unreinforced coating.

  1. Long-term changes in amphetamine-induced reinforcement and aversion in rats following exposure to 56Fe particle

    NASA Technical Reports Server (NTRS)

    Rabin, B. M.; Joseph, J. A.; Shukitt-Hale, B.

    2003-01-01

    Exposing rats to heavy particles produces alterations in the functioning of dopaminergic neurons and in the behaviors that depend upon the integrity of the dopaminergic system. Two of these dopamine-dependent behaviors include amphetamine-induced reinforcement, measure using the conditioned place preference procedure, and amphetamine-induced reinforcement, measured using the conditioned place preference procedure, and amphetamine-induced aversion, measured using the conditioned taste aversion. Previous research has shown that exposing rats to 1.0 Gy of 1GeV/n 56Fe particles produced a disruption of an amphetamine-induced taste aversion 3 days following exposure, but produced an apparent enhancement of the aversion 112 days following exposure. The present experiments were designed to provide a further evaluation of these results by examining taste aversion learning 154 days following exposure to 1.0 Gy 56Fe particles and to establish the convergent validity of the taste aversion results by looking at the effects of exposure on the establishment of an amphetamine-induced conditioned place preference 3, 7, and 16 weeks following irradiation. The taste aversion results failed to confirm the apparent enhancement of the amphetamine-induced CTA observed in the prior experiment. However, exposure to 56Fe particles prevented the acquisition of amphetamine-induced place preference at all three-time intervals. The results are interpreted as indicating that exposure to heavy particles can produce long-term changes in behavioral functioning. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  2. Long-term changes in amphetamine-induced reinforcement and aversion in rats following exposure to 56Fe particle

    NASA Astrophysics Data System (ADS)

    Rabin, B. M.; Joseph, J. A.; Shukitt-Hale, B.

    Exposing rats to heavy particles produces alterations in the functioning of dopaminergic neurons and in the behaviors that depend upon the integrity of the dopaminergic system. Two of these dopamine-dependent behaviors include amphetamine-induced reinforcement, measure using the conditioned place preference procedure, and amphetamine-induced reinforcement, measured using the conditioned place preference procedure, and amphetamine-induced aversion, measured using the conditioned taste aversion. Previous research has shown that exposing rats to 1.0 Gy of 1GeV/n 56Fe particles produced a disruption of an amphetamine-induced taste aversion 3 days following exposure, but produced an apparent enhancement of the aversion 112 days following exposure. The present experiments were designed to provide a further evaluation of these results by examining taste aversion learning 154 days following exposure to 1.0Gy 56Fe particles and to establish the convergent validity of the taste aversion results by looking at the effects of exposure on the establishment of an amphetamine-induced conditioned place preference 3, 7, and 16 weeks following irradiation. The taste aversion results failed to confirm the apparent enhancement of the amphetamine-induced CTA observed in the prior experiment. However, exposure to 56Fe particles prevented the acquisition of amphetamine-induced place preference at all three-time intervals. The results are interpreted as indicating that exposure to heavy particles can produce long-term changes in behavioral functioning.

  3. Near-field optical mapping of single gold nano particles using photo-induced polymer movement of azo-polymers

    NASA Astrophysics Data System (ADS)

    Ishitobi, Hidekazu; Kobayashi, Taka-aki; Ono, Atsushi; Inouye, Yasushi

    2017-03-01

    In this study, polymer movement was induced in azo-polymer films by optical near-fields generated in the vicinity of single gold nano particles (GNPs) to visualize near-field distribution with a spatial resolution beyond the diffraction limit of light. A linearly polarized (Ex) laser beam was irradiated into GNPs to excite local surface plasmon resonance that enhanced the near-field around the GNPs. The findings indicated that different GNP diameters (that is, 50 nm and 80 nm) resulted in different deformation patterns on the films. The results were compared with theoretical calculations of near-field distributions, and the observations revealed that the deformation patterns were dependent on the ratio between Ex and Ey wherein each possessed a different field distribution.

  4. Optimization of the Infrastructure of Reinforced Concrete Reservoirs by a Particle Swarm Algorithm

    NASA Astrophysics Data System (ADS)

    Kia, Saeed; Sebt, Mohammad Hassan; Shahhosseini, Vahid

    2015-03-01

    Optimization techniques may be effective in finding the best modeling and shapes for reinforced concrete reservoirs (RCR) to improve their durability and mechanical behavior, particularly for avoiding or reducing the bending moments in these structures. RCRs are one of the major structures applied for reserving fluids to be used in drinking water networks. Usually, these structures have fixed shapes which are designed and calculated based on input discharges, the conditions of the structure's topology, and geotechnical locations with various combinations of static and dynamic loads. In this research, the elements of reservoir walls are first typed according to the performance analyzed; then the range of the membrane based on the thickness and the minimum and maximum cross sections of the bar used are determined in each element. This is done by considering the variable constraints, which are estimated by the maximum stress capacity. In the next phase, based on the reservoir analysis and using the algorithm of the PARIS connector, the related information is combined with the code for the PSO algorithm, i.e., an algorithm for a swarming search, to determine the optimum thickness of the cross sections for the reservoir membrane's elements and the optimum cross section of the bar used. Based on very complex mathematical linear models for the correct embedding and angles related to achain of peripheral strengthening membranes, which optimize the vibration of the structure, a mutual relation is selected between the modeling software and the code for a particle swarm optimization algorithm. Finally, the comparative weight of the concrete reservoir optimized by the peripheral strengthening membrane is analyzed using common methods. This analysis shows a 19% decrease in the bar's weight, a 20% decrease in the concrete's weight, and a minimum 13% saving in construction costs according to the items of a checklist for a concrete reservoir at 10,000 m3.

  5. Ingrowth of human mesenchymal stem cells into porous silk particle reinforced silk composite scaffolds: An in vitro study.

    PubMed

    Rockwood, Danielle N; Gil, Eun Seok; Park, Sang-Hyug; Kluge, Jonathan A; Grayson, Warren; Bhumiratana, Sarindr; Rajkhowa, Rangam; Wang, Xungai; Kim, Sung Jun; Vunjak-Novakovic, Gordana; Kaplan, David L

    2011-01-01

    Silk fibroin protein is biodegradable and biocompatible, exhibiting excellent mechanical properties for various biomedical applications. However, porous three-dimensional (3-D) silk fibroin scaffolds, or silk sponges, usually fall short in matching the initial mechanical requirements for bone tissue engineering. In the present study, silk sponge matrices were reinforced with silk microparticles to generate protein-protein composite scaffolds with desirable mechanical properties for in vitro osteogenic tissue formation. It was found that increasing the silk microparticle loading led to a substantial increase in the scaffold compressive modulus from 0.3 MPa (non-reinforced) to 1.9 MPa for 1:2 (matrix:particle) reinforcement loading by dry mass. Biochemical, gene expression, and histological assays were employed to study the possible effects of increasing composite scaffold stiffness, due to microparticle reinforcement, on in vitro osteogenic differentiation of human mesenchymal stem cells (hMSCs). Increasing silk microparticle loading increased the osteogenic capability of hMSCs in the presence of bone morphogenic protein-2 (BMP-2) and other osteogenic factors in static culture for up to 6 weeks. The calcium adsorption increased dramatically with increasing loading, as observed from biochemical assays, histological staining, and microcomputer tomography (μCT) analysis. Specifically, calcium content in the scaffolds increased by 0.57, 0.71, and 1.27 mg (per μg of DNA) from 3 to 6 weeks for matrix to particle dry mass loading ratios of 1:0, 1:1, and 1:2, respectively. In addition, μCT imaging revealed that at 6 weeks, bone volume fraction increased from 0.78% for non-reinforced to 7.1% and 6.7% for 1:1 and 1:2 loading, respectively. Our results support the hypothesis that scaffold stiffness may strongly influence the 3-D in vitro differentiation capabilities of hMSCs, providing a means to improve osteogenic outcomes.

  6. pH-dependent control of particle motion through surface interactions with patterned polymer brush surfaces.

    PubMed

    Dunderdale, Gary; Howse, Jonathan; Fairclough, Patrick

    2012-09-11

    In this Article, we show that inclined silicon surfaces patterned with poly(methacrylic acid) brushes are able to control the position and movement of 20 μm silica particles, which are propelled across the patterned surface by sedimentation forces. Three different types of behavior were observed depending on the angle between the direction in which a particle sedimented and the orientation of the polymer-brush silicon interface. At small angles, particles were found to sediment to the brush interface and then sediment following the direction of the brush interface. At larger angles, particles sedimented to the interface and then followed the direction of the brush interface, but then after a certain distance changed direction to pass over the interface. At the largest angles where the brush interface was approximately perpendicular to the motion of the particle, particles were found to travel over the interface unperturbed. This behavior was also found to be pH dependent, allowing the formation of pH responsive "gates", which allow particles to pass at low pH but not at high pH. It was also found that if patterned polymer brush surfaces were oriented in the correct way, they were able to control the number of particles present at specific locations.

  7. Rigid spine reinforced polymer microelectrode array probe and method of fabrication

    DOEpatents

    Tabada, Phillipe; Pannu, Satinderpall S

    2014-05-27

    A rigid spine-reinforced microelectrode array probe and fabrication method. The probe includes a flexible elongated probe body with conductive lines enclosed within a polymeric material. The conductive lines connect microelectrodes found near an insertion end of the probe to respective leads at a connector end of the probe. The probe also includes a rigid spine, such as made from titanium, fixedly attached to the probe body to structurally reinforce the probe body and enable the typically flexible probe body to penetrate and be inserted into tissue, such as neural tissue. By attaching or otherwise fabricating the rigid spine to connect to only an insertion section of the probe body, an integrally connected cable section of the probe body may remain flexible.

  8. Effect of Particles on Rheology and Morphology of Immiscible PI/PDMS Polymer Blends

    NASA Astrophysics Data System (ADS)

    Thareja, Prachi; Velankar, Sachin S.

    2008-07-01

    We present the effects of several interfacially-active particles on the rheology of model immiscible polymer blends of polyisoprene (PI) and polydimethylsiloxane (PDMS) with a droplet-matrix morphology. The particles are capable of adsorbing at the PI/PDMS interface, and hence addition of these particles is expected to significantly affect the breakup and coalescence of drops and consequently the drop size. Using rheology (specifically, strain recovery upon cessation of shear) as a tool to probe morphological evolution, we show that none of the particles are able to prevent coalescence of the drops, at least at a particle loading of 0.5 vol.%. Remarkably however, some particle types strongly promote coalescence in some blends.

  9. Optimisation of Fabric Reinforced Polymer Composites Using a Variant of Genetic Algorithm

    NASA Astrophysics Data System (ADS)

    Axinte, Andrei; Taranu, Nicolae; Bejan, Liliana; Hudisteanu, Iuliana

    2017-03-01

    Fabric reinforced polymeric composites are high performance materials with a rather complex fabric geometry. Therefore, modelling this type of material is a cumbersome task, especially when an efficient use is targeted. One of the most important issue of its design process is the optimisation of the individual laminae and of the laminated structure as a whole. In order to do that, a parametric model of the material has been defined, emphasising the many geometric variables needed to be correlated in the complex process of optimisation. The input parameters involved in this work, include: widths or heights of the tows and the laminate stacking sequence, which are discrete variables, while the gaps between adjacent tows and the height of the neat matrix are continuous variables. This work is one of the first attempts of using a Genetic Algorithm (GA) to optimise the geometrical parameters of satin reinforced multi-layer composites. Given the mixed type of the input parameters involved, an original software called SOMGA (Satin Optimisation with a Modified Genetic Algorithm) has been conceived and utilised in this work. The main goal is to find the best possible solution to the problem of designing a composite material which is able to withstand to a given set of external, in-plane, loads. The optimisation process has been performed using a fitness function which can analyse and compare mechanical behaviour of different fabric reinforced composites, the results being correlated with the ultimate strains, which demonstrate the efficiency of the composite structure.

  10. Characterization of the correlation between the interfaces and failure behaviors for particle reinforced Mg–Li composites

    SciTech Connect

    Zhang, Q.Q.; Wu, G.Q. Huang, Z.; Tao, Y.

    2014-03-01

    The interfacial microstructure of SiC{sub p} or YAl{sub 2p} reinforced Mg–14Li–3Al matrix composites was comparatively characterized by scanning electron microscopy and electron probe microanalysis. A nanoindentation combined with scanning electron microscopy technique was used to characterize the interfacial mechanical properties between the reinforcements and matrix. The interfacial strength and failure behaviors for the composites were analyzed from the load–penetration curves and corresponding images. In situ tensile tests were used to observe the fracture and deformation processes with the aid of scanning electron microscopy. The results show that both the chemical and mechanical compatibilities between the YAl{sub 2} particles and LA143 matrix are better than those between the SiC particles and LA143 matrix. The interfacial breakage load for the SiC/LA143 composite is lower than that for the YAl{sub 2}/LA143 composite because of the worse chemical and mechanical compatibilities between the ceramic particles and metal matrix. Interfacial breakage is the main failure mechanism for the SiC/LA143 composite, while the particle breakage and matrix crack are the main failure mechanism for the YAl{sub 2}/LA143 composite. These may be related to the stronger interfacial bonding between the intermetallic particles and metal matrix. - Highlights: • The compatibility for YAl{sub 2} particle with LA143 matrix is better than SiC particle. • The strength of the YAl{sub 2}/LA143 interface is higher than the SiC/LA143 interface. • The main failure behavior for the SiC/LA143 composite is interfacial breakage. • The main failure behavior for YAl{sub 2}/LA143 composite is particle and matrix breakage. • The interfacial strength plays an important role on the composite failure behavior.

  11. Dielectrophoresis in particle confinement: Aligned carbon particles in polymer matrix below percolation threshold

    NASA Astrophysics Data System (ADS)

    Knaapila, M.; Høyer, H.; Helgesen, G.

    2014-09-01

    We review preparation and properties of confined, aligned string-like particle assemblies formed by dielectrophoresis under alternating electric fields. Particular attention is placed on carbon particles aligned in the oligomer matrix. In these systems the particle fraction is low, below the isotropic percolation threshold. The matrix is polymerized after alignment, which locks the aligned strings in place. Application examples are discussed including particle separation, conductivity enhancement and piezoresistive sensors.

  12. Corrosion resistance of enamel coating modified by calcium silicate and sand particle for steel reinforcement in concrete

    NASA Astrophysics Data System (ADS)

    Tang, Fujian

    Porcelain enamel has stable chemical property in harsh environments such as high temperature, acid and alkaline, and it can also chemically react with substrate reinforcing steel resulting in improved adherence strength. In this study, the corrosion resistances of enamel coating modified by calcium silicate and sand particles, which are designed for improved bond strength with surrounding concrete, were investigated in 3.5 wt% NaCl solution. It consists of two papers that describe the results of the study. The first paper investigates the corrosion behavior of enamel coating modified by calcium silicate applied to reinforcing steel bar in 3.5 wt% NaCl solution by OCP, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The coatings include a pure enamel, a mixed enamel that consists of 50% pure enamel and 50% calcium silicate by weight, and a double enamel that has an inner pure enamel layer and an outer mixed enamel layer. Electrochemical tests demonstrates that both pure and double enamel coatings can significantly improve corrosion resistance, while the mixed enamel coating offers very little protection due to connected channels. The second paper is focused on the electrochemical characteristics of enamel coating modified by sand particle applied to reinforcing steel bar in 3.5 wt% NaCl solution by EIS. Six percentages by weight are considered including 5%, 10%, 20%, 30%, 50%, and 70%. Results reveal that addition of sand particle does not affect its corrosion resistance significantly. Most of the sand particles can wet very well with enamel body, while some have a weak zone which is induced during the cooling stage due to different coefficient of thermal expansion. Therefore, quality control of sand particle is the key factor to improve its corrosion resistance.

  13. Fiber-Reinforced Polymer Composites in Bridges: a State-of-the-Art Report

    DTIC Science & Technology

    2005-05-01

    VACUUM ASSISTED RESIN TRANSFER MOLDING Description of VARTM Process VARTM is a vacuum variation of RTM (Resin Transfer Molding). In RTM ...AMIPC has worked toward developing and demonstrating intelligent RTM and VARTM processing of polymer composites to improve quality and reduce...comprehensive, 3-D simulation software tool for mold filing and enables investigating processing conditions in RTM and VARTM . • VARTM Injection

  14. Fiber-Reinforced Polymer Composites in Bridges: A State-of-the-Art Report

    DTIC Science & Technology

    2005-05-01

    VACUUM ASSISTED RESIN TRANSFER MOLDING Description of VARTM Process VARTM is a vacuum variation of RTM (Resin Transfer Molding). In RTM ...AMIPC has worked toward developing and demonstrating intelligent RTM and VARTM processing of polymer composites to improve quality and reduce...comprehensive, 3-D simulation software tool for mold filing and enables investigating processing conditions in RTM and VARTM . • VARTM Injection

  15. Controlling the motion and placement of micrometer-sized metal particles using patterned polymer brush surfaces.

    PubMed

    Dunderdale, Gary J; Howse, Jonathan R; Fairclough, J Patrick A

    2011-10-04

    In this paper, we show that silicon surfaces patterned with poly(methacrylic acid) brushes are able to control the Brownian motion of 2-3 μm iron particles, which sediment onto the surface in aqueous solution and experience differences in repulsive force depending upon their position. Differences in repulsion lead to different gravitational potential energies across the surface, which gives bias to the Brownian motion taking place. Three regimes have been identified depending upon the brush height: (i) no control of Brownian motion when the brush height is small, (ii) Brownian motion that is influenced by the polymer brush when the brush 17 height is intermediate, (iii) Brownian motion that is confined by polymer brush barriers when the brush height is greatest. The height of brush found necessary to significantly influence iron particle motion was small at 39 nm or 2% of the particle diameter.

  16. Hierarchical ZnO particles grafting by fluorocarbon polymer derivative: Preparation and superhydrophobic behavior

    NASA Astrophysics Data System (ADS)

    Gao, Dahai; Jia, Mengqiu

    2015-07-01

    Superhydrophobic surfaces on the basis of hierarchical ZnO particles grafted by fluoroethylene-vinylether (FEVE) polymer derivative were prepared using a facile, mild and low-cost method. X-ray diffraction (XRD) and scanning electron microscope (SEM) revealed that the resulting ZnO particles via hydrothermal process exhibit micro-nano dual-scale morphology with high purity under a suitable surfactant amount and alkali concentration. The grafting of FEVE derivative was confirmed by Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectrometer (EDS), suggesting that hierarchical surface of ZnO particles was an imported monomolecular layer of fluorocarbon polymer. The obtained surface fabricated by drop-casting shows considerably high contact angle and good resistance to water immersion. The wetting behavior in this work was furthermore analyzed by theoretical wetting model. This work demonstrates that the sufficient low-wettable surface and high roughness both take a vital role in the superhydrophobic behavior.

  17. Active one-particle microrheology of an unentangled polymer melt studied by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Kuhnhold, A.; Paul, W.

    2015-04-01

    We present molecular dynamics simulations for active one-particle microrheology of an unentangled polymer melt. The tracer particle is forced to oscillate by an oscillating harmonic potential, which models an experiment using optical tweezers. The amplitude and phase shift of this oscillation are related to the complex shear modulus of the polymer melt. In the linear response regime at low frequencies, the active microrheology gives the same result as the passive microrheology, where the thermal motion of a tracer particle is related to the complex modulus. We expand the analysis to include full hydrodynamic effects instead of stationary Stokes friction only, and show that different approaches suggested in the literature lead to completely different results, and that none of them improves on the description using the stationary Stokes friction.

  18. Modeling the effect of nano-sized polymer particles on the properties of lipid membranes

    NASA Astrophysics Data System (ADS)

    Rossi, Giulia; Monticelli, Luca

    2014-12-01

    The interaction between polymers and biological membranes has recently gained significant interest in several research areas. On the biomedical side, dendrimers, linear polyelectrolytes, and neutral copolymers find application as drug and gene delivery agents, as biocidal agents, and as platforms for biological sensors. On the environmental side, plastic debris is often disposed of in the oceans and gets degraded into small particles; therefore concern is raising about the interaction of small plastic particles with living organisms. From both perspectives, it is crucial to understand the processes driving the interaction between polymers and cell membranes. In recent times progress in computer technology and simulation methods has allowed computational predictions on the molecular mechanism of interaction between polymeric materials and lipid membranes. Here we review the computational studies on the interaction between lipid membranes and different classes of polymers: dendrimers, linear charged polymers, polyethylene glycol (PEG) and its derivatives, polystyrene, and some generic models of polymer chains. We conclude by discussing some of the technical challenges in this area and future developments.

  19. Semiconducting polymer encapsulated mesoporous silica particles with conjugated Europium complexes: toward enhanced luminescence under aqueous conditions.

    PubMed

    Zhang, Jixi; Prabhakar, Neeraj; Näreoja, Tuomas; Rosenholm, Jessica M

    2014-01-01

    Immobilization of lanthanide organic complexes in meso-organized hybrid materials for luminescence applications have attracted immense interest due to the possibility of controlled segregation at the nanoscopic level for novel optical properties. Aimed at enhancing the luminescence intensity and stability of the hybrid materials in aqueous media, we developed polyvinylpyrrolidone (PVP) stabilized, semiconducting polymer (poly(9-vinylcarbazole), PVK) encapsulated mesoporous silica hybrid particles grafted with Europium(III) complexes. Monosilylated β-diketonate ligands (1-(2-naphthoyl)-3,3,3-trifluoroacetonate, NTA) were first co-condensed in the mesoporous silica particles as pendent groups for bridging and anchoring the lanthanide complexes, resulting in particles with an mean diameter of ∼ 450 nm and a bimodal pore size distribution centered at 3.5 and 5.3 nm. PVK was encapsulated on the resulted particles by a solvent-induced surface precipitation process, in order to seal the mesopores and protect Europium ions from luminescence quenching by producing a hydrophobic environment. The obtained polymer encapsulated MSN-EuLC@PVK-PVP particles exhibit significantly higher intrinsic quantum yield (Φ(Ln) = 39%) and longer lifetime (τ(obs) = 0.51 ms), as compared with those without polymer encapsulation. Most importantly, a high luminescence stability was realized when MSN-EuLC@PVK-PVP particles were dispersed in various aqueous media, showing no noticeable quenching effect. The beneficial features and positive attributes of both mesoporous silica and semiconducting polymers as lanthanide-complex host were merged in a single hybrid carrier, opening up the possibility of using these hybrid luminescent materials under complex aqueous conditions such as biological/physiological environments.

  20. Flow-induced translocation of polymers through a fluidic channel: a dissipative particle dynamics simulation study.

    PubMed

    Guo, Jiayi; Li, Xuejin; Liu, Yuan; Liang, Haojun

    2011-04-07

    The dynamics of flow-induced translocation of polymers through a fluidic channel has been studied by dissipative particle dynamics (DPD) approach. Unlike implicit solvent models, the many-body energetic and hydrodynamic interactions are preserved naturally by incorporating explicit solvent particles in this approach. The no-slip wall boundary and the adaptive boundary conditions have been implemented in the modified DPD approach to model the hydrodynamic flow within a specific wall structure of fluidic channel and control the particles' density fluctuations. The results show that the average translocation time versus polymer chain length satisfies a power-law scaling of τ ∼N(1.152). The conformational changes and translocation dynamics of polymers through the fluidic channel have also been investigated in our simulations, and two different translocation processes, i.e., the single-file and double-folded translocation events, have been observed in detail. These findings may be helpful in understanding the conformational and dynamic behaviors of such polymer and/or DNA molecules during the translocation processes.

  1. Aqueous particulate foams stabilized solely with polymer latex particles.

    PubMed

    Fujii, S; Iddon, P D; Ryan, A J; Armes, S P

    2006-08-29

    In this article, a wide range of latexes are evaluated as possible foam stabilizers. These include near-monodisperse, poly(N-vinyl pyrrolidone)-stabilized polystyrene [PNVP-PS] latexes with diameters ranging from 170 nm to 1.62 microm, submicrometer-sized poly(ethylene glycol)-stabilized polystyrene [PEGMA-PS] latex particles, a PNVP-stabilized poly(4-bromostyrene) [PNVP-PBrS] latex with a mean diameter of 870 nm, two PNVP-stabilized poly(methyl methacrylate) [PNVP-PMMA] latexes with mean diameters of 730 nm and 1.20 microm, a PNVP-stabilized poly(2-hydroxypropyl methacrylate) [PNVP-PHPMA] latex with a mean diameter of 630 nm, and a charge-stabilized anionic PS latex of 220 nm diameter. The effect of varying the particle size, latex concentration, and latex surface composition on foam stability were studied in detail. The larger PNVP-PS latexes, the PNVP-PBrS, and the two PNVP-PMMA latexes gave highly stable foams, whereas PEGMA-PS, PNVP-PHPMA, and the charge-stabilized PS latex produced either no foams or foams with inferior long-term stabilities. Scanning electron microscopy studies revealed hexagonally close-packed latex arrays in the walls of the dried foam, which leads to localized moiré patterns being observed by optical microscopy. Moreover, these dried foams are highly iridescent in bright transmitted light.

  2. Bond strength investigations and structural applicability of composite fiber-reinforced polymer (FRP) rebars

    NASA Astrophysics Data System (ADS)

    Kachlakev, Damian Ivanov

    The composite FRP rebars research at Oregon State University was initiated in 1993 principally to develop a non-metallic hollow reinforcement. It was recognized that the tensile properties of such reinforcement are unquestionably superior to steel, but its performance in concrete could be problematic. The bond between FRP rebars and concrete was identified as a critical area of concern. The purpose of this study is (i) to analyze a variety of FRP and steel reinforcing units; (ii) to advance the knowledge of bond mechanism, failure modes, and parameters influencing the bond strength; (iii) to compare composite rebars to conventional steel and to assess their applicability as reinforcing members. Commercially available FRP rebars were investigated. Particular emphasis was given to a hollow glass FRP rod designed at Oregon State University. Several parameters were investigated, including: failure mode, concrete compressive strength, rebar diameter and circumference/cross section ratio, embedment length, concrete cover, and microstructure of the composite rebars. It was recognized that the ASTM C234-90 pull-out standard is test of concrete strength. Therefore, a modified pull-out test was developed for evaluating the bond strength behavior. A newly developed European bond test procedure was compared with locally modified version of the pull-out method. The new procedure was used for the first time in the United States. The study demonstrated a phenomenon, not reported in the published research at this time, defined as a size effect. The size effects result in lower bond strength with increasing area of the interface between FRP bars and concrete. The next phase of the research was dedicated to the hollow glass FRP rebar. The goal was to compare its bond properties to conventional steel and solid FRP bars. The study led to two new phenomena not described in the literature previously. Results showed that the concrete compressive strength does not significantly affect the

  3. Polymer concrete for precast repair of continuously reinforced concrete pavement on IH 30, near Mt. Pleasant

    NASA Astrophysics Data System (ADS)

    Meyer, A. M.; McCullough, B. F.; Fowler, D. W.

    1981-08-01

    Two punchout repairs made in a continuously reinforced concrete pavement (CRCP) using precast portland cement panels are described. The two repairs, one 1.44 sq. ft., the other 36 sq. ft., were completed and opened to traffic in one afternoon. This technique provides a rapid method of repair that produces a repair that is structurally as good or better than the surrounding pavement. With a trained crew, the repair time can be reduced and thus reducing lane closure time. Since lane closure time is a critical consideration in high volume highways, this method is cost effective in those areas.

  4. Selective transport of Fe(III) using ionic imprinted polymer (IIP) membrane particle

    NASA Astrophysics Data System (ADS)

    Djunaidi, Muhammad Cholid; Jumina, Siswanta, Dwi; Ulbricht, Mathias

    2015-12-01

    The membrane particles was prepared from polyvinyl alcohol (PVA) and polymer IIP with weight ratios of 1: 2 and 1: 1 using different adsorbent templates and casting thickness. The permeability of membrane towards Fe(III) and also mecanism of transport were studied. The selectivity of the membrane for Fe(III) was studied by performing adsorption experiments also with Cr(III) separately. In this study, the preparation of Ionic Imprinted Polymer (IIP) membrane particles for selective transport of Fe (III) had been done using polyeugenol as functional polymer. Polyeugenol was then imprinted with Fe (III) and then crosslinked with PEGDE under alkaline condition to produce polyeugenol-Fe-PEGDE polymer aggregates. The agrregates was then crushed and sieved using mesh size of 80 and the powder was then used to prepare the membrane particles by mixing it with PVA (Mr 125,000) solution in 1-Methyl-2-pyrrolidone (NMP) solvent. The membrane was obtained after casting at a speed of 25 m/s and soaking in NaOH solution overnight. The membrane sheet was then cut and Fe(III) was removed by acid to produce IIP membrane particles. Analysis of the membrane and its constituent was done by XRD, SEM and size selectivity test. Experimental results showed the transport of Fe(III) was faster with the decrease of membrane thickness, while the higher concentration of template ion correlates with higher Fe(III) being transported. However, the transport of Fe(III) was slower for higher concentration of PVA in the membrane. IImparticles works through retarded permeation mechanism, where Fe(III) was bind to the active side of IIP. The active side of IIP membrane was dominated by the -OH groups. The selectivity of all IIP membranes was confirmed as they were all unable to transport Cr (III), while NIP (Non-imprinted Polymer) membrane was able transport Cr (III).

  5. Coarse-grained explicit solvent simulation of the translational and rotational diffusion of a spherical particle in a polymer solution

    NASA Astrophysics Data System (ADS)

    Pryamitsyn, Victor; Ganesan, Venkat

    We use an extension of DPD model to address the dynamical properties of a colloid particle in an unentangled semi-dilute polymer solution. Solvent and monomers are represented as DPD particles.The colloid particle is represented as a larger DPD particle with the rotational degrees of freedom and tangential component of the dissipative and random DPD interactions with the solvent and monomers. This allows us to model a finite slip length boundary condition at the particle fluid interface and study translational Dt and rotational Dr diffusivities of a spherical particle. For zero polymer concentration our results agree with the Stokes-Einstein (SE) theory. Fore dilute and semi-dilute polymer solutions we have found that polymer dynamic follow the Zimm model in a dilute regime and the Rouse model at high polymer concentration. For particles smaller than the polymer Rg observed Dt is much high than SE prediction for R >Rg SE prediction recovers. We have found that increase of Dr relative to SE is rather correlated to the R/Rg ratio than R/ξ, where ξ is the thickness of a depletion shell around the particle. Dr is very sensitive to the slip length at the particle fluid interface and insensitive to R/Rg.

  6. Preparation of Pt/Rh bimetallic colloidal particles in polymer solutions using borohydride-reduction.

    PubMed

    Harada, Masafumi; Einaga, Hisahiro

    2007-04-15

    Colloidal dispersions of Pt/Rh bimetallic particles have been synthesized by the reduction of Pt(IV)/Rh(III) ionic solutions by using borohydride-reduction in the presence of poly(N-vinyl-2-pyrrolidone). The size and the structure of the synthesized particles have been examined by transmission electron micrograph (TEM) and extended X-ray absorption fine structure (EXAFS). We have succeeded in producing the bimetallic Pt/Rh particles with an average diameter of 2.8 nm in polymer solutions by the stepwise addition of sodium borohydride aqueous solution. The distribution of different metallic species in a particle tended to be "cluster-in-cluster" structure, in contrast to the bimetallic particle with an average diameter of 1.4 nm synthesized by alcohol-reduction which have a core-shell structure.

  7. Functional crosslinked polymer particles synthesized by precipitation polymerization for liquid chromatography.

    PubMed

    Perrier-Cornet, R; Héroguez, V; Thienpont, A; Babot, O; Toupance, T

    2008-01-25

    Highly crosslinked functional polymer particles with narrow size distribution have been produced by precipitation copolymerization of divinylbenzene, ethylene glycol dimethacrylate and vinylbenzyl chloride using a simple reflux protocol. After establishing the satisfactory synthesis conditions, we produced uniform chlorobenzyl particles with different size depending on the polymerization times. The porosity of those particles was modulated from microporous to mesoporous structure by using various porogens such as toluene, dodecanol, cyclohexanol and polypropylene glycol. These particles were tested as stationary phase in high-performance liquid chromatography for the separation of polycyclic aromatic hydrocarbons in reversed-phase mode. The separation was observed even for elution 100% organic (methanol) without any participation of water fraction in the eluent composition. The influences of particles size, specific surface area and packing conditions on the separation behavior were investigated.

  8. Modeling of dynamic mechanical properties of polymer composites reinforced by one dimensional nanofillers

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Lu, M.; Chen, M. H.; Wang, L. S.; Bu, Z. X.; Song, G.; Sun, L.

    2016-11-01

    Owing to their high aspect ratio, large specific surface area, high axial Young's modulus/strength, and low density, one dimensional carbon nanomaterials can introduce significant change to the mechanical properties of polymer matrices, both static and dynamic. Thus, one of the most important potential applications of carbon nanotubes or nanofibers is to utilize the enhanced dynamic damping properties of polymer nanocomposites for improved vibration, acoustic, and fatigue performances. This study focuses on calculating the nanocomposite energy dissipation under dynamic mechanical loading. A micromechanical model based on quasi-static stick-slip analysis has been developed to quantify the dynamic mechanical properties of the nanocomposites as a function of external strain in the elastic region. Storage and loss moduli are used to characterize such dynamic mechanical behaviors. Influences of nanotube bundling and nanotube alignment on the damping property of composites have been quantified. Simulation results are in good agreement with the reported experimental measurements.

  9. The effect of matrix microstructure on cyclic response and fatigue behavior of particle- reinforced 2219 aluminum: Part I. room temperature behavior

    NASA Astrophysics Data System (ADS)

    Vyletel, G. M.; Allison, J. E.; van Aken, D. C.

    1995-12-01

    The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and overaged 2219/TiC/15p and unreinforced 2219 Al were investigated using plastic strain-controlled and stress-controlled testing. In addition, the influence of grain size on the particle-reinforced materials was examined. In both reinforced and unreinforced materials, the naturally aged conditions were cyclically unstable, exhibiting an initial hardening behavior followed by an extended region of cyclic stability and ultimately a softening region. The overaged reinforced material was cyclically stable for the plastic strains examined, while the overaged unreinforced material exhibited cyclic hardening at plastic strains greater than 2.5 × 10-4. Decreasing grain size of particle-reinforced materials modestly increased the cyclic flow stress of both naturally aged and overaged materials. Reinforced and unreinforced materials exhibited similar fatigue life behaviors; however, the reinforced and unreinforced naturally aged materials had superior fatigue lives in comparison to the overaged materials. Grain size had no effect on the fatigue life behavior of the particle-reinforced materials. The fatigue lives were strongly influenced by the presence of clusters of TiC particles and exogenous Al3Ti intermetallics.

  10. The effect of matrix microstructure on cyclic response and fatigue behavior of particle-reinforced 2219 aluminum. Part 1: Room temperature behavior

    SciTech Connect

    Vyletel, G.M.; Allison, J.E.; Van Aken, D.C.

    1995-12-01

    The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and overaged 2219/TiC/15p and unreinforced 2219 Al were investigated using plastic strain-controlled and stress-controlled testing. In addition, the influence of grain size on the particle-reinforced materials was examined. In both reinforced and unreinforced materials, the naturally aged conditions were cyclically unstable, exhibiting an initial hardening behavior followed by an extended region of cyclic stability and ultimately a softening region. The overaged reinforced material was cyclically stable for the plastic strains examined, while the overaged unreinforced material exhibited cyclic hardening at plastic strains greater than 2.5 {times} 10{sup {minus}4}. Decreasing grain size of particle-reinforced materials modestly increased the cyclic flow stress of both naturally aged and overaged materials. Reinforced and unreinforced materials exhibited similar fatigue life behaviors; however, the reinforced and unreinforced naturally aged materials had superior fatigue lives in comparison to the overaged materials. Grain size had no effect on the fatigue life behavior of the particle-reinforced materials. The fatigue lives were strongly influenced by the presence of clusters of TiC particles and exogenous Al{sub 3}Ti intermetallics.

  11. Thermal expansion properties of carbon nanotube/silicon carbide particle-reinforced magnesium composites fabricated by squeeze infiltration

    NASA Astrophysics Data System (ADS)

    Cho, Dae Hyun; Nam, Ji Hoon; Lee, Byoung Woo; Yim, Si On; Park, Ik Min

    2016-03-01

    In this study, hybrid composites of AZ91 Mg alloy reinforced with carbon nanotubes (CNTs) and silicon carbide particles (SiCps) were successfully fabricated by the squeeze infiltration method. For this fabrication, hybrid preforms of CNTs (5, 10, and 15 vol%) and SiCps (30 vol%) were produced by vacuum suction from slurry mix containing organic and inorganic binders. Hybrid CNT+SiCp/AZ91 Mg composites were fabricated by squeeze infiltration, and the melt infiltrated well between the reinforcements during squeeze infiltration to produce a hybrid MMC with virtually no pores. Their microstructural and thermal expansion properties were evaluated The resulting CNT+SiCp/AZ91 Mg hybrid composites were found to exhibit a significant decrease in their coefficients of thermal expansion with an increase in the CNT volume fraction, owing to the near-zero thermal expansion of the CNTs and the CTE mismatch between them and the AZ91 Mg matrix.

  12. Splat formation during thermal spraying of polymer particles: Mathematical modeling and experimental analysis

    NASA Astrophysics Data System (ADS)

    Ivosevic, Milan

    This thesis develops and presents a model for predicting the three-dimensional splat formation process for polymer particles under High Velocity Oxy-Fuel (HVOF) combustion spray process conditions. During HVOF spray deposition, jets of high temperature, high velocity gases are used to heat, melt and accelerate particulate materials injected into the jet and propel them towards a surface to be coated. Upon impact at the surface, multiple hot particles impact and form splats that overlap, cool and consolidate to form a coating. These splats are the building blocks of an HVOF coating and coating characteristics such as porosity, roughness, adhesive and cohesive strengths depend on the morphology of these splats and how they bond to the substrate and to each other. Fully coupled transport models of particle acceleration and heating in an HVOF jet were simultaneously integrated within a FORTRAN code to predict particle velocity and particle temperature profiles at impact. Then, a volume-of-fluid computational fluid mechanics package, Flow-3DRTM, was used to predict particle deformation and splat shapes using results from the acceleration and heating models as the initial conditions. Fluid flow of spreading polymer droplets was modeled as a generalized Newtonian fluid with temperature and shear rate dependent viscosity. While shear thinning primarily affected the droplet spreading ratio, the internal temperature distribution had the largest effect on the final splat shape, particularly when particles were partially melted. The predicted shapes of deformed particles exhibited good qualitative agreement with experimentally observed splats. Most of the larger experimentally observed (> 70 mum) Nylon-11 splats sprayed onto room temperature flat or rough substrates exhibited a characteristic "fried-egg" shape with a large, nearly-hemispherical, core in the center of a thin disk. This shape was formed from polymer particles having a low temperature, high viscosity core and a

  13. Nafion electro-spun reinforced membranes for polymer electrolyte fuel cell.

    PubMed

    Carbone, Alessandra; Saccà, Ada; Busacca, Concetta; Frontera, Patrizia; Antonucci, Pier Luigi; Passalacqua, Enza

    2011-10-01

    The introduction of different reinforcement materials (yarns, fibrils, etc) into the membranes has been investigated with the aim of maintaining adequate membrane properties in terms of mechanical strength, good chemical stability, low swelling at critical temperatures and a stable electrochemical performance in PEFC. An innovative technique for the development of membranes is based on polymeric films containing polymeric nanofibres obtained through electrospinning. The electrospinning of Nafion blends with polyvinylpirrolidone (PVP) and polystyrene (PS) was investigated in this work. In particular, the morphology and diameter of electrospun fibres as a function of the electrospinning parameters and solution preparation have been studied and in both cases, a critical concentration of blend solution was found. Beaded fibres were obtained above such a concentration and, below it, only fibre mats were observed. Reinforced Nafion-based membranes were realised by using the obtained spun films. Preliminary proton conductivity and fuel cell results have shown the capability of operating in a fuel cell environment with a slightly higher performance than pure Nafion but having an improved stability at high temperatures.

  14. A viscoelastic-viscoplastic model for short-fibre reinforced polymers with complex fibre orientations

    NASA Astrophysics Data System (ADS)

    Nciri, M.; Notta-Cuvier, D.; Lauro, F.; Chaari, F.; Zouari, B.; Maalej, Y.

    2015-09-01

    This paper presents an innovative approach for the modelling of viscous behaviour of short-fibre reinforced composites (SFRC) with complex distributions of fibre orientations and for a wide range of strain rates. As an alternative to more complex homogenisation methods, the model is based on an additive decomposition of the state potential for the computation of composite's macroscopic behaviour. Thus, the composite material is seen as the assembly of a matrix medium and several linear elastic fibre media. The division of short fibres into several families means that complex distributions of orientation or random orientation can be easily modelled. The matrix behaviour is strain-rate sensitive, i.e. viscoelastic and/or viscoplastic. Viscoelastic constitutive laws are based on a generalised linear Maxwell model and the modelling of the viscoplasticity is based on an overstress approach. The model is tested for the case of a polypropylene reinforced with short-glass fibres with distributed orientations and subjected to uniaxial tensile tests, in different loading directions and under different strain rates. Results demonstrate the efficiency of the model over a wide range of strain rates.

  15. Physicochemical evaluation of silica-glass fiber reinforced polymers for prosthodontic applications.

    PubMed

    Meriç, Gökçe; Dahl, Jon E; Ruyter, I Eystein

    2005-06-01

    This investigation was designed to formulate silica-glass fiber reinforced polymeric materials. Fused silica-glass fibers were chosen for the study. They were heat-treated at various temperatures (500 degrees C, 800 degrees C and 1100 degrees C), silanized, sized and incorporated in two modified resin mixtures (A and B). The flexural properties in dry and wet conditions were tested and statistically analyzed, and the content of residual methyl methacrylate (MMA) monomer, dimensional changes with temperature, water sorption and solubility were determined. Woven fibers [36.9% (wt/wt)], heat-treated at 500 degrees C, gave the highest strength values for the polymeric composites (an ultimate transverse strength of 200 Mpa and a flexural modulus of 10 GPa) compared with the fibers heat-treated at other temperatures. There was no statistically significant difference in the measured flexural properties between resins A and B regarding fiber treatment and water storage time. These fiber composites had a small quantity of residual MMA content [0.37 +/- 0.007% (wt/wt)] and very low water solubility, indicating good biocompatibility. It was suggested that silica-glass fibers could be used for reinforcement as a result of their anticipated good qualities in aqueous environments, such as the oral environment.

  16. A plant fiber reinforced polymer composite prepared by a twin-screw extruder.

    PubMed

    Sui, G; Fuqua, M A; Ulven, C A; Zhong, W H

    2009-02-01

    Polypropylene (PP) composites reinforced using a novel plant fiber, sunflower hull sanding dust (SHSD), were prepared using a twin-screw extruder. Thermal and mechanical properties of the SHSD/PP composites were characterized and compared to an organically modified clay (organo-clay)/PP composite. Differential scanning calorimetry (DSC) analysis showed that the crystallization temperature and the degree of crystallinity of PP exhibited changes with addition of SHSD and organo-clay. Mechanical properties of the PP were enhanced with the addition of SHSDs. Both the flexural strength and flexural modulus of the PP composites containing 5% (w/w) SHSD were comparable to that of the 5% (w/w) organo-clay reinforced PP. Scanning electron microscope (SEM) observation showed that no obvious agglomeration of SHSD existed in the PP matrix. Compared to the neat PP and organo-clay/PP, the SHSD/PP composites exhibited a relatively decreasing rate of thermal degradation with increase in temperature. Experimental results suggest that SHSD, as a sunflower processing byproduct, may find promising applications in composite materials.

  17. Microexplosions and ignition dynamics in engineered aluminum/polymer fuel particles

    DOE PAGES

    Rubio, Mario A.; Gunduz, I. Emre; Groven, Lori J.; ...

    2016-11-11

    Aluminum particles are widely used as a metal fuel in solid propellants. However, poor combustion efficiencies and two-phase flow losses result due in part to particle agglomeration. Engineered composite particles of aluminum (Al) with inclusions of polytetrafluoroethylene (PTFE) or low-density polyethylene (LDPE) have been shown to improve ignition and yield smaller agglomerates in solid propellants, recently. Reductions in agglomeration were attributed to internal pressurization and fragmentation (microexplosions) of the composite particles at the propellant surface. We explore the mechanisms responsible for microexplosions in order to better understand the combustion characteristics of composite fuel particles. Single composite particles of Al/PTFE andmore » Al/LDPE with diameters between 100 and 1200 µm are ignited on a substrate to mimic a burning propellant surface in a controlled environment using a CO2 laser in the irradiance range of 78–7700 W/cm2. Furthermore, the effects of particle size, milling time, and inclusion content on the resulting ignition delay, product particle size distributions, and microexplosion tendencies are reported. For example particles with higher PTFE content (30 wt%) had laser flux ignition thresholds as low as 77 W/cm2, exhibiting more burning particle dispersion due to microexplosions compared to the other materials considered. Composite Al/LDPE particles exhibit relatively high ignition thresholds compared to Al/PTFE particles, and microexplosions were observed only with laser fluxes above 5500 W/cm2 due to low LDPE reactivity with Al resulting in negligible particle self-heating. However, results show that microexplosions can occur for Al containing both low and high reactivity inclusions (LDPE and PTFE, respectively) and that polymer inclusions can be used to tailor the ignition threshold. Furthermore, this class of modified metal particles shows significant promise for application in many different energetic materials

  18. Microexplosions and ignition dynamics in engineered aluminum/polymer fuel particles

    SciTech Connect

    Rubio, Mario A.; Gunduz, I. Emre; Groven, Lori J.; Sippel, Travis R.; Han, Chang Wan; Unocic, Raymond R.; Ortalan, Volkan; Son, Steven F.

    2016-11-11

    Aluminum particles are widely used as a metal fuel in solid propellants. However, poor combustion efficiencies and two-phase flow losses result due in part to particle agglomeration. Engineered composite particles of aluminum (Al) with inclusions of polytetrafluoroethylene (PTFE) or low-density polyethylene (LDPE) have been shown to improve ignition and yield smaller agglomerates in solid propellants, recently. Reductions in agglomeration were attributed to internal pressurization and fragmentation (microexplosions) of the composite particles at the propellant surface. We explore the mechanisms responsible for microexplosions in order to better understand the combustion characteristics of composite fuel particles. Single composite particles of Al/PTFE and Al/LDPE with diameters between 100 and 1200 µm are ignited on a substrate to mimic a burning propellant surface in a controlled environment using a CO2 laser in the irradiance range of 78–7700 W/cm2. Furthermore, the effects of particle size, milling time, and inclusion content on the resulting ignition delay, product particle size distributions, and microexplosion tendencies are reported. For example particles with higher PTFE content (30 wt%) had laser flux ignition thresholds as low as 77 W/cm2, exhibiting more burning particle dispersion due to microexplosions compared to the other materials considered. Composite Al/LDPE particles exhibit relatively high ignition thresholds compared to Al/PTFE particles, and microexplosions were observed only with laser fluxes above 5500 W/cm2 due to low LDPE reactivity with Al resulting in negligible particle self-heating. However, results show that microexplosions can occur for Al containing both low and high reactivity inclusions (LDPE and PTFE, respectively) and that polymer inclusions can be used to tailor the ignition threshold. Furthermore, this class of modified metal particles shows significant promise for application in

  19. Removal of toxic uranium from synthetic nuclear power reactor effluents using uranyl ion imprinted polymer particles.

    PubMed

    Preetha, Chandrika Ravindran; Gladis, Joseph Mary; Rao, Talasila Prasada; Venkateswaran, Gopala

    2006-05-01

    Major quantities of uranium find use as nuclear fuel in nuclear power reactors. In view of the extreme toxicity of uranium and consequent stringent limits fixed by WHO and various national governments, it is essential to remove uranium from nuclear power reactor effluents before discharge into environment. Ion imprinted polymer (IIP) materials have traditionally been used for the recovery of uranium from dilute aqueous solutions prior to detection or from seawater. We now describe the use of IIP materials for selective removal of uranium from a typical synthetic nuclear power reactor effluent. The IIP materials were prepared for uranyl ion (imprint ion) by forming binary salicylaldoxime (SALO) or 4-vinylpyridine (VP) or ternary SALO-VP complexes in 2-methoxyethanol (porogen) and copolymerizing in the presence of styrene (monomer), divinylbenzene (cross-linking monomer), and 2,2'-azobisisobutyronitrile (initiator). The resulting materials were then ground and sieved to obtain unleached polymer particles. Leached IIP particles were obtained by leaching the imprint ions with 6.0 M HCl. Control polymer particles were also prepared analogously without the imprint ion. The IIP particles obtained with ternary complex alone gave quantitative removal of uranyl ion in the pH range 3.5-5.0 with as low as 0.08 g. The retention capacity of uranyl IIP particles was found to be 98.50 mg/g of polymer. The present study successfully demonstrates the feasibility of removing uranyl ions selectively in the range 5 microg - 300 mg present in 500 mL of synthetic nuclear power reactor effluent containing a host of other inorganic species.

  20. Novel mini-reactor of silicone oil droplets for synthesis of morphology-controlled polymer particles.

    PubMed

    Nagao, Daisuke; Ohta, Tatsuya; Ishii, Haruyuki; Imhof, Arnout; Konno, Mikio

    2012-12-21

    Inside spaces of emulsion droplets can be used as mini-reactors for material synthesis. The novel application of sol-gel derived silicone oil droplets as mini-reactors was examined for the case of polymerization of styrene (St) and comonomers with the oil-soluble initiator 2,2'-azobis(2,4-dimethylvaleronitrile). Polydimethylsiloxane (PDMS) droplets prepared from dimethylsiloxane were used as the mini-reactors, in which the polymerization of St without comonomers was first conducted. In the polymerization, the St/PDMS volume ratio was varied from 0.025 to 0.10. After the polymerization, each PDMS droplet contained a polystyrene (PSt) particle. The St/PDMS ratio of 0.05 enabled the synthesis of micrometer-sized, spherical PSt particles with low polydispsersity. Copolymerization of St with comonomers having hydrophilic groups deformed the spherical shape of particles to lens-like or disk-like morphologies that were obtained with acrylic acid or sodium 4-styrene sulfonate, respectively. In another copolymerization, with divinylbenzene used as a cross-linker, hemispherical polymer particles were formed. To diversify the particle morphologies further, the proposed mini-reactor synthesis was combined with the recently proposed silicone oil droplet templating method (Ohta et al., 2012). Around the PDMS droplets containing a polymer particle, polymeric shells with a depression were successfully formed with the proposed method. The remaining PDMS oil inside the polymeric shells was extracted with ethanol, which caused hemispherical polymeric bowl-shaped capsules having a protrusion on the inside.

  1. Microstructure and Strain Rate Effects on the Mechanical Behavior of Particle Reinforced Epoxy-Based Reactive Materials

    DTIC Science & Technology

    2011-12-01

    properties between metals on polymer substrates using X- ray photoelectron spectroscopy (XPS). In their work, they focused on two main groups of metals...versus substrate temperature for DEA/air- oxidized Al heated in vacuum. The error bars are derived from estimated uncertainties in measuring peak... production of an interphase around the particles. To corroborate their findings they showed two distinct peaks in the free volume distribution from PALS

  2. Adsorption and disjoining pressure isotherms of confined polymers using dissipative particle dynamics.

    PubMed

    Goicochea, A Gama

    2007-11-06

    The adsorption and disjoining pressure isotherms of polymers confined by planar walls are obtained using Monte Carlo (MC) simulations in the Grand Canonical (GC) ensemble in combination with the mesoscopic technique known as dissipative particle dynamics (DPD). Two models of effective potentials for the confining surfaces are used: one with both an attractive and a repulsive term and one with a purely repulsive term. As for the polymer, seven-bead linear model of polyethylene glycol (PEG) dissolved in water is used. The results indicate remarkably good agreement between the trends shown by our adsorption isotherms and those obtained from experiments of PEG on oxide surfaces. Additionally, the disjoining pressure isotherm of water shows oscillations, while those of PEG display the same trend for both wall models. Moreover, it is found that the disjoining pressure isotherms are in qualitative agreement with those from experiments on confined linear polymers.

  3. Effect of embedded printed circuit board (PCB) sensors on the mechanical behavior of glass fiber-reinforced polymer (GFRP) structures

    NASA Astrophysics Data System (ADS)

    Javdanitehran, M.; Hoffmann, R.; Groh, J.; Vossiek, M.; Ziegmann, G.

    2016-06-01

    The embedding of dielectric chipless sensors for cure monitoring into fiber-reinforced thermosets allows for monitoring and controlling the curing process and consequently higher quality in production. The embedded sensors remain after the processing in the structure. This affects the integrity of the composite structure locally. In order to investigate these effects on the mechanical behavior of the glass fiber-reinforced polymer (GFRP), sensors made on special low loss substrates are integrated into laminates with different lay-ups and thicknesses using vacuum assisted resin transfer molding (VARTM) method. In a parametric study the size of the sensor is varied to observe its influence on the strength and the stiffness of the laminates according to its lay-up and thickness. The size and orientation of the resin rich areas near sensors as well as the distortion in load bearing area as the consequences of the introduction of the sensors are investigated in conjunction with the strength of the structure. An empirical model is proposed by the authors which involves the previously mentioned factors and is used as a rapid tool for the prediction of the changes in bending and tensile strength of simple structures with embedded sensors. The methodology for model’s calibration as well as the validation of the model against the experimental data of different laminates with distinct lay-ups and thicknesses are presented in this work. Mechanical tests under tensile and bending loading indicate that the reduction of the structure’s strength due to sensor integration can be attributed to the size and the orientation of rich resin zones and depends over and above on the size of distorted load bearing area. Depending on the sensor’s elastic modulus the stiffness of the structure may vary through the introduction of a sensor.

  4. Mechanical Properties of Carbon Nanofiber Reinforced Polymer Composites-Molecular Dynamics Approach

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit; Chandra, Rakesh; Kumar, Pramod; Kumar, Navin

    2016-06-01

    Molecular dynamics simulation has been used to study the effect of carbon nanofiber (CNF) volume fraction ( V f) and aspect ratio ( l/d) on mechanical properties of CNF-reinforced polypropylene (PP) composites. Materials Studio 5.5 has been used as a tool for finding the modulus and damping in composites. CNF composition in PP was varied by volume from 0% to 16%. The aspect ratio of CNF was varied from l/d = 5 to l/d = 100. Results show that, with only 2% addition by volume of CNF in PP, E 11 increases 748%. Increase in E 22 is much less in comparison to the increase in E 11. With the increase in the CNF aspect ratio ( l/d) up to l/d = 60, the longitudinal loss factor ( η 11) decreases rapidly. The results of this study have been compared with those available in the literature.

  5. Assessment of solvent capsule-based healing for woven E-glass fibre-reinforced polymers

    NASA Astrophysics Data System (ADS)

    Manfredi, Erica; Cohades, Amaël; Richard, Inès; Michaud, Véronique

    2015-01-01

    Vacuum Assisted Resin Infusion Molding (VARIM) with low vacuum pressure difference was used to manufacture woven glass fibre-reinforced epoxy resin plates, with a fibre volume fraction of approx. 50 vol% and containing ethyl phenylacetate (EPA)-filled capsules for self-healing purposes. Capsules were introduced by functionalising the fabrics through manual dispersion. We investigated the capability of autonomously healing delaminations induced by static loading in Mode I and II. Healing did not take place for composite samples; this was attributed to the presence of bare fibres on the crack plane and to the reduction of EPA diffusion into the matrix in the presence of fibres both of which hinder the swelling mechanism responsible for healing the cracks.

  6. Pyrolysis of reinforced polymer composites: Parameterizing a model for multiple compositions

    NASA Astrophysics Data System (ADS)

    Martin, Geraldine E.

    A single set of material properties was developed to describe the pyrolysis of fiberglass reinforced polyester composites at multiple composition ratios. Milligram-scale testing was performed on the unsaturated polyester (UP) resin using thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) to establish and characterize an effective semi-global reaction mechanism, of three consecutive first-order reactions. Radiation-driven gasification experiments were conducted on UP resin and the fiberglass composites at compositions ranging from 41 to 54 wt% resin at external heat fluxes from 30 to 70 kW m -2. The back surface temperature was recorded with an infrared camera and used as the target for inverse analysis to determine the thermal conductivity of the systematically isolated constituent species. Manual iterations were performed in a comprehensive pyrolysis model, ThermaKin. The complete set of properties was validated for the ability to reproduce the mass loss rate during gasification testing.

  7. Milling damage on Carbon Fibre Reinforced Polymer using TiAlN coated End mills

    NASA Astrophysics Data System (ADS)

    Konneh, Mohamed; Izman, Sudin; Rahman Kassim, Abdullah Abdul

    2015-07-01

    This paper reports on the damage caused by milling Carbon Fibre Reinforced Composite (CFRP) with 2-flute 4 mm-diameter solid carbide end mills, coated with titanium aluminium nitride. The machining parameters considered in work are, rotation speed, feed rate and depth of cut. Experiments were designed based on Box-Behnken design and the experiments conducted on a Mikrotool DT-110 CNC micro machine. A laser tachometer was used to ascertain a rotational speed for conducting any machining trial. Optical microscopy examination reveals minimum delamination value of 4.05 mm at the spindle speed of 25,000 rpm, depth of cut of 50μm and feed rate of 3 mm/min and the maximum delamination value of 5.04 mm at the spindle speed of 35000 rpm, depth of cut of 150μm and feed rate of 9 mm/min A mathematical model relating the milling parameters and delamination has been established.

  8. Fundamental analysis of the failure of polymer-based fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Kanninen, M. F.; Rybicki, E. F.; Griffith, W. I.; Broek, D.

    1975-01-01

    A mathematical model predicting the strength of unidirectional fiber reinforced composites containing known flaws and with linear elastic-brittle material behavior was developed. The approach was to imbed a local heterogeneous region surrounding the crack tip into an anisotropic elastic continuum. This (1) permits an explicit analysis of the micromechanical processes involved in the fracture, and (2) remains simple enough to be useful in practical computations. Computations for arbitrary flaw size and orientation under arbitrary applied loads were performed. The mechanical properties were those of graphite epoxy. With the rupture properties arbitrarily varied to test the capabilities of the model to reflect real fracture modes, it was shown that fiber breakage, matrix crazing, crack bridging, matrix-fiber debonding, and axial splitting can all occur during a period of (gradually) increasing load prior to catastrophic failure. The calculations also reveal the sequential nature of the stable crack growth process proceding fracture.

  9. Extrusion of polysaccharide nanocrystal reinforced polymer nanocomposites through compatibilization with poly(ethylene oxide).

    PubMed

    Pereda, Mariana; El Kissi, Nadia; Dufresne, Alain

    2014-06-25

    Polysaccharide nanocrystals with a rodlike shape but with different dimensions and specific surface area were prepared from cotton and capim dourado cellulose, and with a plateletlike morphology from waxy maize starch granules. The rheological behavior of aqueous solutions of poly(ethylene oxide) (PEO) with different molecular weights when adding these nanoparticles was investigated evidencing specific interactions between PEO chains and nanocrystals. Because PEO also bears hydrophobic moieties, it was employed as a compatibilizing agent for the melt processing of polymer nanocomposites. The freeze-dried mixtures were used to prepare nanocomposite materials with a low density polyethylene matrix by extrusion. The thermal and mechanical behavior of ensuing nanocomposites was studied.

  10. A multiplexed electrospray process for single-step synthesis of stabilized polymer particles for drug delivery.

    PubMed

    Almería, Begoña; Fahmy, Tarek M; Gomez, Alessandro

    2011-09-05

    While conventional methods for biodegradable particle production rely predominately on batch, emulsion preparation methods, an alternative process based on multiplexed electrospray (ES) can offer distinct advantages. These include enhanced encapsulation efficiency of hydrophilic and hydrophobic agents, scale-up potential, tight control over particle size and excellent particulate reproducibility. Here we developed a well-controlled ES process to synthesize coated biodegradable polymer particles. We demonstrate this process with the Poly(DL-lactic-co-glycolic acid) system encapsulating amphiphilic agents such as doxorubicin (DOX), Rhodamine B (RHO(B)) and Rhodamine B octadecyl ester perchlorate (RHO(BOEP)). We show that in a single-step flow process particles can be made encapsulating the agent with high efficiency and coated either with emulsifiers that stabilize them in solution or that may facilitate further functionalization for targeted drug delivery. The coating process allows for the surface modification of the particles without further changes in particle size or morphology, and with minimal loss of drug (>94% encapsulation efficiency). This synthesis technique is well suited for massive scale-up using microfabricated, multiplexed arrays consisting of multiple electrospray nozzles operating in parallel. A simple analytical model of the diffusion of the encapsulated agent within the polymer reveals two distinct phases in the cumulative release profile: a first phase in which the release is dominated by diffusion and a second phase with a slower release related to the erosion of the polymer matrix. The first, diffusion-driven stage is highly affected by particle agglomeration properties, whereas the second one shows a much less pronounced dependence on particle size. Modeling suggests that the size of the particles will substantially influence the initial burst in both the percentage of drug released and the rate at which it is released. It will also affect to

  11. Polymer blend particles with defined compositions for targeting antigen to both class I and II antigen presentation pathways.

    PubMed

    Tran, Kenny K; Zhan, Xi; Shen, Hong

    2014-05-01

    Defense against many persistent and difficult-to-treat diseases requires a combination of humoral, CD4(+) , and CD8(+) T-cell responses, which necessitates targeting antigens to both class I and II antigen presentation pathways. In this study, polymer blend particles are developed by mixing two functionally unique polymers, poly(lactide-co-glycolide) (PLGA) and a pH-responsive polymer, poly(dimethylaminoethyl methacrylate-co-propylacrylic acid-co-butyl methacrylate) (DMAEMA-co-PAA-co-BMA). Polymer blend particles are shown to enable the delivery of antigens into both class I and II antigen presentation pathways in vitro. Increasing the ratio of the pH-responsive polymer in blend particles increases the degree of class I antigen presentation, while maintaining high levels of class II antigen presentation. In a mouse model, it is demonstrated that a significantly higher and sustained level of CD4(+) and CD8(+) T-cell responses, and comparable antibody responses, are elicited with polymer blend particles than PLGA particles and a conventional vaccine, Alum. The polymer blend particles offer a potential vaccine delivery platform to generate a combination of humoral and cell-mediated immune responses that insure robust and long-lasting immunity against many infectious diseases and cancers.

  12. Nonlocal Entropic Repulsion Effects on Rod Polymer Induced Depletion Attraction between Spherical Particles

    NASA Astrophysics Data System (ADS)

    Chen, Yeng-Long; Schweizer, Kenneth

    2002-03-01

    The polymer liquid state integral equation approach for treating depletion phenomena in rigid rod-colloid suspensions is generalized to account for spatially nonlocal entropic repulsions which modify rod orientation near an impenetrable particle. A thermodynamically consistent theory for the rod segment-particle direct correlation function is formulated under athermal conditions for thin rods and all ratios of the rod length, L, to sphere diameter, D. Results for the polymer density profile near a colloid, the cross second virial coefficient, and the sphere-sphere depletion potential under dilute polymer conditions have been obtained. Relative to simpler approaches based on the (local) Percus-Yevick closure approximation, the new theory represents a qualitative improvement for the shape of the polymer density profile at small separations, and a major quantitative improvement for the depletion attraction strength at colloidal contact when D>L. Detailed comparisons reveal very good agreement of the theory with both exact simulation results for all size asymmetry ratios, and recent direct experimental measurements of the fd-virus(rod) induced depletion potential between silica colloids where L ~ D.

  13. Investigation of dielectric properties of polymer composites reinforced with carbon nanotubes in the frequency band of 0.01 Hz - 10 MHz

    NASA Astrophysics Data System (ADS)

    Goshev, A. A.; Eseev, M. K.; Kapustin, S. N.; Vinnik, L. N.; Volkov, A. S.

    2016-08-01

    The goal of this work is experimental study of dielectric properties of polymer nanocomposites reinforced with multiwalled carbon nanotubes (MWCNTs) in alternating electric field in low frequency band of 0.01 Hz - 10 MHz. We investigated the influence, functionalization degree, aspect ratio, concentration of carbon nanotubes (CNTs) on dielectric properties of polymer sample. We also studied the dependence of dielectric properties on the polymerization temperature. The dependence of CNTs agglomeration on sample polymerization temperature and temperature's influence on conductivity has been shown. We conducted model calculation of percolation threshold and figured out its dependence on CNTs aspect ratio.

  14. Investigations of the effects of particle properties on the wear resistance of the particle reinforced composites using a novel wear model

    NASA Astrophysics Data System (ADS)

    Prabhu, T. Ram

    2016-08-01

    A wear model is developed based on the discrete lattice spring-mass approach to study the effects of particle volume fraction, size, and stiffness on the wear resistance of particle reinforced composites. To study these effects, we have considered three volume fractions (10%, 20% and 30%), two sizes (10 × 10 and 4 × 4 sites), and two different stiffness of particles embedded in the matrix in a regular pattern. In this model, we have discretized the composite system (400 × 100 sites) into the lumped masses connected with interaction spring elements in two dimensions. The interaction elements are assumed as linear elastic and ideal plastic under applied forces. Each mass is connected to its first and second nearest neighbors by springs. The matrix and particles sites are differentiated by choosing the different stiffness values. The counter surface is simulated as a rigid body that moves on the composite material at a constant sliding speed along the horizontal direction. The governing equations are formed by equating the spring force between the pair of sites given by Hooke’s law plus external contact forces and the force due to the motion of the site given by the equation of motion. The equations are solved for the plastic strain accumulated in the springs using an explicit time stepping procedure based on a finite difference form of the above equations. If the total strain accumulated in the spring elements connected to a lump mass site exceeds the failure strain, the springs are considered to be broken, and the mass site is removed or worn away from the lattice and accounts as a wear loss. The model predicts that (i) increasing volume fraction, reducing particle size and increasing particle stiffness enhance the wear resistance of the particle reinforced composites, (ii) the particle stiffness is the most significant factor affecting the wear resistance of the composites, and (iii) the wear resistance reduced above the critical volume fraction (Vc), and Vc

  15. Dissipative particle dynamics simulations in the grand canonical ensemble: applications to polymer brushes.

    PubMed

    Goujon, Florent; Malfreyt, Patrice; Tildesley, Dominic J

    2004-04-19

    We have used the dissipative particle dynamics (DPD) method in the grand canonical ensemble to study the compression of grafted polymer brushes in good solvent conditions. The force-distance profiles calculated from DPD simulations in the grand canonical ensemble are in very good agreement with the self-consistent field (SCF) theoretical models and with experimental results for two polystyrene brush layers grafted onto mica surfaces in toluene.

  16. Physical characterization and in silico modeling of inulin polymer conformation during vaccine adjuvant particle formation.

    PubMed

    Barclay, Thomas G; Rajapaksha, Harinda; Thilagam, Alagu; Qian, Gujie; Ginic-Markovic, Milena; Cooper, Peter D; Gerson, Andrea; Petrovsky, Nikolai

    2016-06-05

    This study combined physical data from synchrotron SAXS, FTIR and microscopy with in-silico molecular structure predictions and mathematical modeling to examine inulin adjuvant particle formation and structure. The results show that inulin polymer chains adopt swollen random coil in solution. As precipitation occurs from solution, interactions between the glucose end group of one chain and a fructose group of an adjacent chain help drive organized assembly, initially forming inulin ribbons with helical organization of the chains orthogonal to the long-axis of the ribbon. Subsequent aggregation of the ribbons results in the layered semicrystalline particles previously shown to act as potent vaccine adjuvants. γ-Inulin adjuvant particles consist of crystalline layers 8.5 nm thick comprising helically organized inulin chains orthogonal to the plane of the layer. These crystalline layers alternate with amorphous layers 2.4 nm thick, to give overall particle crystallinity of 78%.

  17. Ignition of a polymer propellant of hybrid rocket motor by a hot particle

    NASA Astrophysics Data System (ADS)

    Glushkov, D. O.; Kuznetsov, G. V.; Strizhak, P. A.

    2017-04-01

    The ignition of polymethylmethacrylate (typical model propellant of the hybrid rocket motor) by a hot particle in a shape of parallelepiped, polyhedron, disk is investigated numerically. The initial temperature of a heat source varied within the range 950-1150 K, size of particle - within the range 2-6 mm. It is established that varying these parameters influenced significantly the main characteristic of the process - ignition delay time under ignition conditions close to critical. For considered shape of particles, ignition delay time is in ascending sequence: parallelepiped, polyhedron, disk. Three polymer ignition regimes, which characterized by the initial temperature of a heat source, ignition delay time and a location of an ignition zone in a vicinity of a hot particle, are emphasized. It is illustrated that taking into account the dependence of thermal and physical characteristics of polymethylmethacrylate on temperature, the ignition delay time increased due to augmentation of energy accumulated by a subsurface layer.

  18. Effect of heat treatment on microstructure and interface of SiC particle reinforced 2124 Al matrix composite

    SciTech Connect

    Mandal, Durbadal; Viswanathan, Srinath

    2013-11-15

    The microstructure and interface between metal matrix and ceramic reinforcement of a composite play an important role in improving its properties. In the present investigation, the interface and intermetallic compound present in the samples were characterized to understand structural stability at an elevated temperature. Aluminum based 2124 alloy with 10 wt.% silicon carbide (SiC) particle reinforced composite was prepared through vortex method and the solid ingot was deformed by hot rolling for better particle distribution. Heat treatment of the composite was carried out at 575 °C with varying holding time from 1 to 48 h followed by water quenching. In this study, the microstructure and interface of the SiC particle reinforced Al based composites have been studied using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA) associated with wavelength dispersive spectroscopy (WDS) and transmission electron microscopy (TEM) to identify the precipitate and intermetallic phases that are formed during heat treatment. The SiC particles are uniformly distributed in the aluminum matrix. The microstructure analyses of Al–SiC composite after heat treatment reveal that a wide range of dispersed phases are formed at grain boundary and surrounding the SiC particles. The energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy analyses confirm that finely dispersed phases are CuAl{sub 2} and CuMgAl{sub 2} intermetallic and large spherical phases are Fe{sub 2}SiAl{sub 8} or Al{sub 15}(Fe,Mn){sub 3}Si. It is also observed that a continuous layer enriched with Cu and Mg of thickness 50–80 nm is formed at the interface in between Al and SiC particles. EDS analysis also confirms that Cu and Mg are segregated at the interface of the composite while no carbide is identified at the interface. - Highlights: • The composite was successfully heat treated at 575°C for 1

  19. Study on experimental characterization of carbon fiber reinforced polymer panel using digital image correlation: A sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Kashfuddoja, Mohammad; Prasath, R. G. R.; Ramji, M.

    2014-11-01

    In this work, the experimental characterization of polymer-matrix and polymer based carbon fiber reinforced composite laminate by employing a whole field non-contact digital image correlation (DIC) technique is presented. The properties are evaluated based on full field data obtained from DIC measurements by performing a series of tests as per ASTM standards. The evaluated properties are compared with the results obtained from conventional testing and analytical models and they are found to closely match. Further, sensitivity of DIC parameters on material properties is investigated and their optimum value is identified. It is found that the subset size has more influence on material properties as compared to step size and their predicted optimum value for the case of both matrix and composite material is found consistent with each other. The aspect ratio of region of interest (ROI) chosen for correlation should be the same as that of camera resolution aspect ratio for better correlation. Also, an open cutout panel made of the same composite laminate is taken into consideration to demonstrate the sensitivity of DIC parameters on predicting complex strain field surrounding the hole. It is observed that the strain field surrounding the hole is much more sensitive to step size rather than subset size. Lower step size produced highly pixilated strain field, showing sensitivity of local strain at the expense of computational time in addition with random scattered noisy pattern whereas higher step size mitigates the noisy pattern at the expense of losing the details present in data and even alters the natural trend of strain field leading to erroneous maximum strain locations. The subset size variation mainly presents a smoothing effect, eliminating noise from strain field while maintaining the details in the data without altering their natural trend. However, the increase in subset size significantly reduces the strain data at hole edge due to discontinuity in

  20. Impact of Sterilization Method on Protein Aggregation and Particle Formation in Polymer-Based Syringes.

    PubMed

    Kiminami, Hideaki; Krueger, Aaron B; Abe, Yoshihiko; Yoshino, Keisuke; Carpenter, John F

    2017-04-01

    The effects of sterilization methods on the storage stability of erythropoietin (EPO) in polymer-based syringes were assessed by quantifying protein oxidation, aggregation, and particle formation. Micro-particle counting and size exclusion chromatography coupled with a multi-angle light scattering detector demonstrated much lower levels of protein particles and aggregates for EPO stored for 12 weeks in steam-sterilized than in radiation (Rad)-sterilized syringes. Intermediate levels of damage were observed for EPO stored in ethylene oxide-sterilized syringes. HPLC analysis documented that the Rad-sterilized syringes caused increased oxidation of the protein during storage. In contrast, in the steam- and ethylene oxide-sterilized syringes EPO oxidation did not change. Analysis with electron spin resonance revealed that only Rad-sterilized syringes formed radicals in the syringe body, which persisted over the 12-week storage period. These results demonstrated that Rad-sterilization generated radicals in the syringes which in turn caused increased EPO oxidation, particle formation, and protein aggregation. Therefore, steam sterilization was shown to be a preferable sterilization method for the polymer-based syringe system when using biopharmaceutical drugs highly sensitive to oxidation, and particle formation and aggregation.

  1. Effects of biodegradable polymer particles on rat marrow-derived stromal osteoblasts in vitro.

    PubMed

    Wake, M C; Gerecht, P D; Lu, L; Mikos, A G

    1998-07-01

    Effects of biodegradable particles of poly(L-lactic acid) (PLLA) and poly(DL-lactic-co-glycolic acid) (PLGA) 50/50 with diameter ranging from 1.0 to 1.5 microm on rat marrow stromal osteoblasts in vitro have been investigated over a period of 28 days. This study examined the effects of three particle parameters, concentration, polymer molecular weight, and composition, on osteoblast proliferation and function. Cell cultures were challenged with particles at two different time points: upon cell seeding (Day 1), and after cells had begun to establish their own mineralized extracellular matrix (Day 14). The most significant trend observed in those cultures challenged with particles beginning on Day 1 was due to increasing the concentration of particles, resulting in decreased [3H]-thymidine incorporation, cell count, and mineralization. Those cultures challenged with particles beginning on Day 14 were significantly more mineralized than those challenged with particles beginning on Day 1. In addition, increasing osteocalcin secretion confirmed the osteoblastic phenotype of the derived stromal cells. These studies suggest that the particles may affect the bone remodeling process surrounding a degrading implant by direct interaction with osteoblasts in addition to their indirect contributions to the inflammatory mechanism via mediators secreted by macrophages upon their phagocytosis.

  2. Magnetic-Field-Assisted Fabrication and Manipulation of Nonspherical Polymer Particles in Ferrofluid-Based Droplet Microfluidics.

    PubMed

    Zhu, Taotao; Cheng, Rui; Sheppard, Gareth R; Locklin, Jason; Mao, Leidong

    2015-08-11

    We report a novel magnetic-field-assisted method for the fabrication and manipulation of nonspherical polymer particles within a ferrofluid-based droplet microfluidic device. Shape control and chain assembly of droplets with tunable lengths have been achieved.

  3. Effect of pressure on the formation of superelastic hard particles in a metal-fullerene system and the tribological properties of composite materials reinforced with such particles

    NASA Astrophysics Data System (ADS)

    Chernogorova, O. P.; Drozdova, E. I.; Blinov, V. M.; Ovchinnikova, I. N.

    2011-03-01

    Raman spectroscopy, X-ray diffraction, and microhardness and modulus of elasticity measurements are used to study the influence of compacting pressure (5, 8 GPa) on the structure and properties of the phases prepared from fullerene soot extract (mixture of C60 and C70 crystallites) in a mixture with a cobalt powder. Carbon particles synthesized during high-temperature treatment at a pressure of 5 or 8 GPa and reinforcing composite samples have a universal hardness H u (hardness measured from the total (elastic and plastic) strain under loading) of 12 or 25 GPa, respectively. After heating of samples to 900°C, the values of H u of the particles decrease to 9-11 GPa at elastic recovery of the phase more than 85%. The dry friction coefficients of iron- and cobalt-based composite materials in contact with tool steel are 0.08 and 0.04, respectively.

  4. Mechanical properties of neat polymer matrix materials and their unidirectional carbon fiber-reinforced composites

    NASA Technical Reports Server (NTRS)

    Zimmerman, Richard S.; Adams, Donald F.

    1988-01-01

    The mechanical properties of two neat resin systems for use in carbon fiber epoxy composites were characterized. This included tensile and shear stiffness and strengths, coefficients of thermal and moisture expansion, and fracture toughness. Tests were conducted on specimens in the dry and moisture-saturated states, at temperatures of 23, 82 and 121 C. The neat resins tested were American Cyanamid 1806 and Union Carbide ERX-4901B(MPDA). Results were compared to previously tested neat resins. Four unidirectional carbon fiber reinforced composites were mechanically characterized. Axial and transverse tension and in-plane shear strengths and stiffness were measured, as well as transverse coefficients of thermal and moisture expansion. Tests were conducted on dry specimens only at 23 and 100 C. The materials tested were AS4/3502, AS6/5245-C, T300/BP907, and C6000/1806 unidirectional composites. Scanning electron microscopic examination of fracture surfaces was performed to permit the correlation of observed failure modes with the environmental test conditions.

  5. A review and analysis of microwave absorption in polymer composites filled with carbonaceous particles

    NASA Astrophysics Data System (ADS)

    Qin, F.; Brosseau, C.

    2012-03-01

    Carbon (C) is a crucial material for many branches of modern technology. A growing number of demanding applications in electronics and telecommunications rely on the unique properties of C allotropes. The need for microwave absorbers and radar-absorbing materials is ever growing in military applications (reduction of radar signature of aircraft, ships, tanks, and targets) as well as in civilian applications (reduction of electromagnetic interference among components and circuits, reduction of the back-radiation of microstrip radiators). Whatever the application for which the absorber is intended, weight reduction and optimization of the operating bandwidth are two important issues. A composite absorber that uses carbonaceous particles in combination with a polymer matrix offers a large flexibility for design and properties control, as the composite can be tuned and optimized via changes in both the carbonaceous inclusions (C black, C nanotube, C fiber, graphene) and the embedding matrix (rubber, thermoplastic). This paper offers a perspective on the experimental efforts toward the development of microwave absorbers composed of carbonaceous inclusions in a polymer matrix. The absorption properties of such composites can be tailored through changes in geometry, composition, morphology, and volume fraction of the filler particles. Polymer composites filled with carbonaceous particles provide a versatile system to probe physical properties at the nanoscale of fundamental interest and of relevance to a wide range of potential applications that span radar absorption, electromagnetic protection from natural phenomena (lightning), shielding for particle accelerators in nuclear physics, nuclear electromagnetic pulse protection, electromagnetic compatibility for electronic devices, high-intensity radiated field protection, anechoic chambers, and human exposure mitigation. Carbonaceous particles are also relevant to future applications that require environmentally benign and

  6. Computational modeling of the electromagnetic characteristics of carbon fiber-reinforced polymer composites with different weave structures

    NASA Astrophysics Data System (ADS)

    Hassan, A. M.; Douglas, J. F.; Garboczi, E. J.

    2014-02-01

    Carbon fiber reinforced polymer composites (CFRPC) are of great interest in the aerospace and automotive industries due to their exceptional mechanical properties. Carbon fibers are typically woven and inter-laced perpendicularly in warps and wefts to form a carbon fabric that can be embedded in a binding matrix. The warps and wefts can be interlaced in different patterns called weaving structures. The primary weaving structures are the plain, twill, and satin weaves, which give different mechanical composite properties. The goal of this work is to computationally investigate the dependence of CFRPC microwave and terahertz electromagnetic characteristics on weave structure. These bands are good candidates for the Nondestructive Evaluation (NDE) of CFRPC since their wavelengths are comparable to the main weave features. 3D full wave electromagnetic simulations of several different weave models have been performed using a finite element (FEM) simulator, which is able to accurately model the complex weave structure. The computational experiments demonstrate that the reflection of electromagnetic waves from CFRPC depend sensitively on weave structure. The reflection spectra calculated in this work can be used to identify the optimal frequencies for the NDE of each weave structure.

  7. Determining the material parameters for the reconstruction of defects in carbon fiber reinforced polymers from data measured by flash thermography

    NASA Astrophysics Data System (ADS)

    Müller, Jan P.; Götschel, Sebastian; Maierhofer, Christiane; Weiser, Martin

    2017-02-01

    Flash thermography is a fast and reliable non-destructive testing method for the investigation of defects in carbon fiber reinforced polymer (CFRP) materials. In this paper numerical simulations of transient thermography data are presented, calculated for a quasi-isotropic flat bottom hole sample. They are compared to experimental data. These simulations are one important step towards the quantitative reconstruction of a flaw by assessing thermographic data. The applied numerical model is based on the finite-element method, extended by a semi-analytical treatment of the boundary of the sample, which is heated by the flash light. A crucial part for a reliable numerical model is the prior determination of the material parameters of the specimen as well as of the experimental parameters of the set-up. The material parameters in plane and in depth diffusivity are measured using laser line excitation. In addition, the absorption and heat transfer process of the first layers is investigated using an IR microscopic lens. The performance of the two distinct components of CFRP during heating - epoxy resin and carbon fibers - is examined. Finally, the material parameters are optimized by variation and comparison of the simulation results to the experimental data. The optimized parameters are compared to the measured ones and further methods to ensure precise material parameter measurements are discussed.

  8. Active vortex generator deployed on demand by size independent actuation of shape memory alloy wires integrated in fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Hübler, M.; Nissle, S.; Gurka, M.; Wassenaar, J.

    2016-04-01

    Static vortex generators (VGs) are installed on different aircraft types. They generate vortices and interfuse the slow boundary layer with the fast moving air above. Due to this energizing, a flow separation of the boundary layer can be suppressed at high angles of attack. However the VGs cause a permanently increased drag over the whole flight cycle reducing the cruise efficiency. This drawback is currently limiting the use of VGs. New active VGs, deployed only on demand at low speed, can help to overcome this contradiction. Active hybrid structures, combining the actuation of shape memory alloys (SMA) with fiber reinforced polymers (FRP) on the materials level, provide an actuation principle with high lightweight potential and minimum space requirements. Being one of the first applications of active hybrid structures from SMA and FRP, these active vortex generators help to demonstrate the advantages of this new technology. A new design approach and experimental results of active VGs are presented based on the application of unique design tools and advanced manufacturing approaches for these active hybrid structures. The experimental investigation of the actuation focuses on the deflection potential and the dynamic response. Benchmark performance data such as a weight of 1.5g and a maximum thickness of only 1.8mm per vortex generator finally ensure a simple integration in the wing structure.

  9. Development of a self-stressing NiTiNb shape memory alloy (SMA)/fiber reinforced polymer (FRP) patch

    NASA Astrophysics Data System (ADS)

    El-Tahan, M.; Dawood, M.; Song, G.

    2015-06-01

    The objective of this research is to develop a self-stressing patch using a combination of shape memory alloys (SMAs) and fiber reinforced polymer (FRP) composites. Prestressed carbon FRP patches are emerging as a promising alternative to traditional methods to repair cracked steel structures and civil infrastructure. However, prestressing these patches typically requires heavy and complex fixtures, which is impractical in many applications. This paper presents a new approach in which the prestressing force is applied by restraining the shape memory effect of NiTiNb SMA wires. The wires are subsequently embedded in an FRP overlay patch. This method overcomes the practical challenges associated with conventional prestressing. This paper presents the conceptual development of the self-stressing patch with the support of experimental observations. The bond between the SMA wires and the FRP is evaluated using pull-out tests. The paper concludes with an experimental study that evaluates the patch response during activation subsequent monotonic tensile loading. The results demonstrate that the self-stressing patch with NiTiNb SMA is capable of generating a significant prestressing force with minimal tool and labor requirements.

  10. Carbon fiber reinforced polymer dimensional stability investigations for use on the laser interferometer space antenna mission telescope.

    PubMed

    Sanjuán, J; Preston, A; Korytov, D; Spector, A; Freise, A; Dixon, G; Livas, J; Mueller, G

    2011-12-01

    The laser interferometer space antenna (LISA) is a mission designed to detect low frequency gravitational waves. In order for LISA to succeed in its goal of direct measurement of gravitational waves, many subsystems must work together to measure the distance between proof masses on adjacent spacecraft. One such subsystem, the telescope, plays a critical role as it is the laser transmission and reception link between spacecraft. Not only must the material that makes up the telescope support structure be strong, stiff, and light, but it must have a dimensional stability of better than 1 pm Hz(-1/2) at 3 mHz and the distance between the primary and the secondary mirrors must change by less than 2.5 μm over the mission lifetime. Carbon fiber reinforced polymer is the current baseline material; however, it has not been tested to the pico meter level as required by the LISA mission. In this paper, we present dimensional stability results, outgassing effects occurring in the cavity and discuss its feasibility for use as the telescope spacer for the LISA spacecraft.

  11. Glass fiber-reinforced polymer packaged fiber Bragg grating sensors for low-speed weigh-in-motion measurements

    NASA Astrophysics Data System (ADS)

    Al-Tarawneh, Mu'ath; Huang, Ying

    2016-08-01

    The weight of rolling trucks on roads is one of the critical factors for the management of road networks due to the continuous increase in truck weight. Weigh-in-motion (WIM) sensors have been widely used for weight enforcement. A three-dimensional glass fiber-reinforced polymer packaged fiber Bragg grating sensor (3-D GFRP-FBG) is introduced for in-pavement WIM measurement at low vehicle passing speed. A sensitivity study shows that the developed sensor is very sensitive to the sensor installation depth and the longitudinal and transverse locations of the wheel loading position. The developed 3-D GFRP-FBG sensor is applicable for most practical pavements with a panel length larger than 6 ft, and it also shows a very good long-term durability. For the three components in 3-D of the developed sensor, the longitudinal component has the highest sensitivity for WIM measurements, followed by the transverse and vertical components. Field testing validated the sensitivity and repeatability of the developed 3-D GFRP-FBG sensor. The developed sensor provides the transportation agency one alternative solution for WIM measurement, which could significantly improve the measurement efficiency and long-term durability.

  12. Tolerancing of a carbon fiber reinforced polymer metering tube structure of a high-resolution space-borne telescope

    NASA Astrophysics Data System (ADS)

    Ekinci, Mustafa

    2016-07-01

    High resolution space borne telescopes require dimensionally stable structures to meet very stringent optical requirements. Furthermore, high resolution space borne telescope structures need to have high stiffness and be lightweight in order to survive launch loads. Carbon fiber reinforced polymers (CFRP) are lightweight and have tailorable mechanical properties like stiffness and coefficient of thermal expansion. However, mechanical properties are highly dependent on manufacturing processes and manufacturing precision. Moreover CFRP tend to absorb moisture which affects dimensional stability of the structure in the vacuum environment. In order to get specified properties out of manufacturing, tolerances need to be defined very accurately. In this paper, behavior of CFRP metering tube structure of a high resolution space borne camera is investigated for ply orientation, fiber and void content deviations which may arise from manufacturing errors and limitations. A computer code is generated to determine laminate properties of stacked up uni-directional (UD) laminae using classical laminate theory with fiber and matrix properties obtained from suppliers and literature. After defining laminate stackup, many samples are virtually created with ply orientations, volumetric fiber and void content that randomly deviates in a tolerance range which will be used in manufacturing. Normal distribution, standard deviation and mean values are presented for elasticity modulus, coefficient of thermal expansion (CTE), coefficient of moisture expansion (CME) and thermal conductivity in axial and transverse directions of quasi-isotropic stackups and other stackups which have properties presented in literature.

  13. Multi Scale Modeling of Continuous Aramid Fiber Reinforced Polymer Matrix Composites Used in Ballistic Protection Applications

    DTIC Science & Technology

    2014-11-16

    molecular chain; (b) fibril ; (c) fiber; (d) yarn; (e) fabric/ply; (f) single lamina; (g) stacked lamina; and (h) laminate. In addition, issues...identified and their respective mechanical constitutive relations derived and parameterized: (a) molecular chain; (b) fibril ; (c) fiber; (d) yarn; (e... Fibril length scales – At these length scales, the material is represented as an ensemble of interacting constituent particles (atoms/ions); (b) Fiber

  14. Characteristics of ionic polymer-metal composite with chemically doped TiO2 particles

    NASA Astrophysics Data System (ADS)

    Jung, Youngsoo; Kim, Seong Jun; Kim, Kwang J.; Lee, Deuk Yong

    2011-12-01

    Many studies have investigated techniques to improve the bending performance of ionic polymer-metal composite (IPMC) actuators, including 'doping' of metal particles in the polymer membrane usually by means of physical processes. This study is mainly focused on the characterization of the physical, electrochemical and electromechanical properties of TiO2-doped ionic polymer membranes and IPMCs prepared by the sol-gel method, which results in a uniform distribution of the particles inside the polymer membrane. X-ray and UV-visible spectra indicate the presence of anatase-TiO2 in the modified membranes. TiO2-doped membranes (0.16 wt%) exhibit the highest level of water uptake. The glass transition temperature of these membranes, measured using differential scanning calorimetry (DSC), increases with the increase of the amount of TiO2 in the membrane. Dynamic mechanical analysis (DMA) demonstrated that the storage modulus of dried TiO2-doped ionic polymer membranes increases as the amount of TiO2 in the membrane increases, whereas the storage modulus of hydrated samples is closely related to the level of water uptake. Electrochemical impedance spectroscopy (EIS) shows that the conductivity of TiO2-doped membranes decreases with increasing TiO2 content in spite of an internal resistance drop in the samples. Above all, bending deflection of TiO2-doped IPMC decreased with higher TiO2 content in the membrane while the blocking force of each sample increased with the higher TiO2 content. Additionally, it was determined that the lifetime of IPMC is strongly dependent on the level of water uptake.

  15. Investigating the particle to fibre transition threshold during electrohydrodynamic atomization of a polymer solution.

    PubMed

    Husain, O; Lau, W; Edirisinghe, M; Parhizkar, M

    2016-08-01

    Electrohydrodynamic atomization (EHDA) is a key research area for producing micro and nano-sized structures. This process can be categorized into two main operating regimes: electrospraying for particle generation and electrospinning for fibre production. Producing particles/fibres of the desired size or morphology depends on two main factors; properties of the polymeric solution used and the processing conditions including flow rate, applied voltage and collection distance. In this work the particle-fibre transition region was analyzed by changing the polymer concentration of PLGA poly (lactic-co-glycolic acid) in acetone between 2 and 25wt%. Subsequently the processing conditions were adjusted to study the optimum transition parameters. Additionally the EHDA configuration was also modified by adding a metallic plate to observe the deposition area. The diameter and the distance of the plate from the capillary tip were adjusted to investigate variations in particle and fibre morphologies as well. It was found that complete transition from particles to fibres occurs at 20wt% indicating concentration to be the dominant criterion. Low flow rates yielded fibres without beads. However the applied voltage and distance between the tip of the nozzle jetting the polymer solution and collector (working distance) did not yield definitive results. Reducing the collector distance and increasing applied voltages produces smooth as well as beaded fibres. Addition of a metal plate reduces particle size by ~1μm; the fibre size increases especially with increasing plate diameter while bead density and size reduces when the disc is fixed closer to the capillary tip. Additionally, the deposition area is reduced by 70% and 57% with the addition of metal plates of 30mm and 60mm, respectively. The results indicate that a metal plate can be utilized further to tune the particle/fibre size and morphology and this also significantly increases the yield of EHDA process which is currently a

  16. Microstructural study and densification analysis of hot work tool steel matrix composites reinforced with TiB{sub 2} particles

    SciTech Connect

    Fedrizzi, A.; Pellizzari, M.; Zadra, M.; Marin, E.

    2013-12-15

    Hot work tool steels are characterized by good toughness and high hot hardness but are less wear resistant than other tooling materials, such as high speed steel. Metal matrix composites show improved tribological behavior, but not much work has been done in the field of hot work tool steels. In this paper TiB{sub 2}-reinforced hot work tool steel matrix composites were produced by spark plasma sintering (SPS). Mechanical alloying (MA) was proposed as a suited process to improve the composite microstructure. Density measurements and microstructure confirmed that MA promotes sintering and produces a fine and homogeneous dispersion of reinforcing particles. X-ray diffraction patterns of the sintered composites highlighted the formation of equilibrium Fe{sub 2}B and TiC, as predicted by thermodynamic calculations using Thermo-Calc® software. Scanning electron microscopy as well as scanning Kelvin probe force microscopy highlighted the reaction of the steel matrix with TiB{sub 2} particles, showing the formation of a reaction layer at the TiB{sub 2}-steel interface. Phase investigations pointed out that TiB{sub 2} is not chemically stable in steel matrix because of the presence of carbon even during short time SPS. - Highlights: • TiB{sub 2} reinforced steel matrix composites were produced by spark plasma sintering. • TiB{sub 2} was successfully dispersed in the steel matrix by mechanical alloying. • Steel and TiB{sub 2} react during sintering forming equilibrium Fe{sub 2}B and TiC. • The new phases were investigated by means of AFM, Volta potential and XRD analyses.

  17. Enhanced single-particle brightness and photostability of semiconductor polymer dots by enzymatic oxygen scavenging system

    NASA Astrophysics Data System (ADS)

    Liu, Zhihe; Yang, Yingkun; Sun, Zezhou; Wu, Changfeng

    2016-12-01

    Semiconductor polymer dots (Pdots) are emerging as an excellent fluorescent probe in biology and medicine. However, the photostability of Pdots can't meet the requirements of long term single-particle imaging and tracking applications. Here we describe the enhanced single-particle brightness and photostability of Pdots by using an efficient enzymatic oxygen scavenging system (OSS). Pdots with particle diameters of 21 nm and 43 nm (PFBT21 and PFBT43) were prepared by a nanoprecipitation method. Single-particle imaging and photobleaching were performed to investigate the effect of OSS on the per-particle brightness and photostability of Pdots. Our results indicate that the single-particle brightness of the PFBT21 Pdots in OSS was enhanced nearly two times as compare to the PFBT21 Pdots in water. The photobleaching percentages of PFBT21 and PFBT43 in OSS were determined to be 29% and 33%, respectively. These values are decreased by 2-3 times as compared to those of the same Pdots in water, indicating the significantly improved photostability of Pdots by OSS. This study provides a promising approach for enhancing photostability of Pdots in long term single-particle tracking.

  18. Self-healing of damage in fibre-reinforced polymer-matrix composites.

    PubMed

    Hayes, S A; Zhang, W; Branthwaite, M; Jones, F R

    2007-04-22

    Self-healing resin systems have been discussed for over a decade and four different technologies had been proposed. However, little work on their application as composite matrices has been published although this was one of the stated aims of the earliest work in the field. This paper reports on the optimization of a solid-state self-healing resin system and its subsequent use as a matrix for high volume fraction glass fibre-reinforced composites. The resin system was optimized using Charpy impact testing and repeated healing, while the efficiency of healing in composites was determined by analysing the growth of delaminations following repeated impacts with or without a healing cycle. To act as a reference, a non-healing resin system was subjected to the same treatments and the results are compared with the healable system. The optimized resin system displays a healing efficiency of 65% after the first healing cycle, dropping to 35 and 30% after the second and third healing cycles, respectively. Correction for any healability due to further curing showed that approximately 50% healing efficiency could be achieved with the bisphenol A-based epoxy resin containing 7.5% of polybisphenol-A-co-epichlorohydrin. The composite, on the other hand, displays a healing efficiency of approximately 30%. It is therefore clear that the solid-state self-healing system is capable of healing transverse cracks and delaminations in a composite, but that more work is needed to optimize matrix healing within a composite and to develop a methodology for assessing recovery in performance.

  19. Friction and wear characteristics of polymer-matrix friction materials reinforced by brass fibers

    NASA Astrophysics Data System (ADS)

    Xian, Jia; Xiaomei, Ling

    2004-10-01

    This study is an investigation of friction materials reinforced by brass fibers, and the influence of the organic adhesion agent, cast-iron debris, brass fiber, and graphite powder on the friction-wear characteristics. Friction and wear testing was performed on a block-on-ring tribometer (MM200). The friction pair consisted of the friction materials and gray cast iron (HT200). The worn surface layers formed by sliding dry friction were examined using scanning electron microscopy (SEM), x-ray energy-dispersive analysis (EDX), and differential thermal analysis-thermogravimetric analysis (DTA-TAG). The experimental results showed that the friction coefficient and the wear loss of the friction materials increased with the increase of cast-iron debris, but decreased with the increase of graphite powder content. The friction coefficient and wear loss also increased slightly when the mass fraction of brass fibers was over 19%. When the mass fraction of organic adhesion agent was about 10 11%, the friction materials had excellent friction-wear performance. Surface heating from friction pyrolyzes the organic ingredient in the worn surface layer of the friction materials, with the pyrolysis depth being about 0.5 mm. The surface layers were rich in iron but poor in copper, and they were formed on the worn surface of the friction material. When the mass fraction of brass fibers was about 16 20%, the friction materials possessed better wear resistance and a copper transfer film formed on the friction surface of counterpart. Fatigue cracks were also found in the worn surface of the gray cast-iron counterpart, with fatigue wear being the prevailing wear mechanism.

  20. Development of polymer-biomolecule core-shell particles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Suthiwangcharoen, Nisaraporn

    Developing efficient strategies to introduce biomolecules around polymeric nanoparticles (NPs) is critical for targeted delivery of therapeutic or diagnostic agents. Although polymeric NPs have been well established, problems such as toxicity, stability, and immunoresistance remain potential concerns. The first part of this dissertation focuses on the development of nanosized targeted drug delivery vehicle in cancer chemotherapy. The vehicle was created by the self-assembly of folate-grafted filamentous bacteriophage M13 with poly(caprolactone- b-2-vinylpyridine) while doxorubicin, the antitumor drugs, was successfully loaded in the interior of the vehicles. These particles offer unique properties of being able to selectively target tumor cells while appearing to be safe and non-toxic to normal cells. Although they have shown great prospects in many biomedical applications, less is known about the interactions between biomolecules and polymers. The next part of the dissertation focuses on the self-assembly of proteins and polymers to create polymer-protein core-shell nanoparticles (PPCS-NPs). Several proteins with different isoelectric points and molecular weights were employed to demonstrate a versatility of our assembly method while a series of esterified derivatives of poly(2-hydroxyethyl methacrylate) (pHEMA) were synthesized to evaluate the interaction between proteins and polymers. Our data indicated that the polymers containing pyridine residues can successfully assemble with proteins, and the mechanism is mainly governed by hydrogen bonding and the hydrophobic/hydrophilic interactions. This in turn helps retaining proteins' folding conformation and functionality, which are also demonstrated in the in vitro/in vivo cellular uptake of the PPCS-NPs in endothelial cells. The last part of the dissertation focuses on the self-assembly of the bienzyme-polymer NPs. Glucose oxidase (GOX) together with horseradish peroxidase (HRP) were employed to construct bienzyme

  1. Effect of Y2O3 and TiC Reinforcement Particles on Intermetallic Formation and Hardness of Al6061 Composites via Mechanical Alloying and Sintering

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Liang; Lin, Chen-Han

    2015-08-01

    Al6061-based composites reinforced with 2 wt pctY2O3 and 2 wt pctTiC particles produced by mechanical alloying were investigated. The reinforced particles play important roles in the microstructural development and in determining the properties of the alloys. High-energy ball milling can facilitate a solid-state reaction between reinforced particles and the Al matrix, and the reaction kinetics of atomic diffusion can be accelerated enormously by subsequent sintering processing. As a result, complex intermetallic compounds and oxide particles can be formed in the alloy. In this study, the effect of reinforcement on phase formation and mechanical properties of Al6061-based composites has been examined. The results suggest that nano-Y2O3 particles can act as nucleation sites to facilitate formation of Al-Si-Y-O-based oxide particles. The addition of TiC particles can effectively refine the grain structure and encourage formation of iron-rich intermetallic compounds. Nanoindentation was used to understand the local variations in mechanical properties of the Al6061-based composites.

  2. Canonical free-energy barrier of particle and polymer cluster formation

    PubMed Central

    Zierenberg, Johannes; Schierz, Philipp; Janke, Wolfhard

    2017-01-01

    A common approach to study nucleation rates is the estimation of free-energy barriers. This usually requires knowledge about the shape of the forming droplet, a task that becomes notoriously difficult in macromolecular setups starting with a proper definition of the cluster boundary. Here we demonstrate a shape-free determination of the free energy for temperature-driven cluster formation in particle as well as polymer systems. Combined with rigorous results on equilibrium droplet formation, this allows for a well-defined finite-size scaling analysis of the effective interfacial free energy at a fixed density. We first verify the theoretical predictions for the formation of a liquid droplet in a supersaturated particle gas by generalized-ensemble Monte Carlo simulations of a Lennard-Jones system. Going one step further, we then generalize this approach to cluster formation in a dilute polymer solution. Our results suggest an analogy with particle condensation, when the macromolecules are interpreted as extended particles. PMID:28240262

  3. LOW-COST COMPOSITES IN VEHICLE MANUFACTURE - Natural-fiber-reinforced polymer composites in automotive applications.

    SciTech Connect

    Holbery, Jim; Houston, Dan

    2006-11-01

    In the last decade, natural fiber composites have experienced rapid growth in the European automotive market, and this trend appears to be global in scale, provided the cost and performance is justified against competing technologies. However, mass reduction, recyclability, and performance requirements can be met today by competing systems such as injection-molded unreinforced thermoplastics; natural fiber composites will continue to expand their role in automotive applications only if such technical challenges as moisture stability, fiber-polymer interface compatibility, and consistent, repeatable fiber sources are available to supply automotive manufacturers. Efforts underway by Tier I and II automotive suppliers to explore hybrid glass-natural fiber systems, as well as applications that exploit such capabilities as natural fiber sound dampening characteristics, could very well have far-reaching effects. In addition, the current development underway of bio-based resins such as Polyhydroxyalkanoate (PHA) biodegradable polyesters and bio-based polyols could provide fully bio-based composite options to future automotive designers. In short, the development of the natural fiber composite market would make a positive impact on farmers and small business owners on a global scale, reduce US reliance on foreign oil, improve environmental quality through the development of a sustainable resource supply chain, and achieve a better CO2 balance over the vehicle?s lifetime with near-zero net greenhouse gas emissions.

  4. Effect of re-melting on particle distribution and interface formation in SiC reinforced 2124Al matrix composite

    SciTech Connect

    Mandal, Durbadal; Viswanathan, Srinath

    2013-12-15

    The interface between metal matrix and ceramic reinforcement particles plays an important role in improving properties of the metal matrix composites. Hence, it is important to find out the interface structure of composite after re-melting. In the present investigation, the 2124Al matrix with 10 wt.% SiC particle reinforced composite was re-melted at 800 °C and 900 °C for 10 min followed by pouring into a permanent mould. The microstructures reveal that the SiC particles are distributed throughout the Al-matrix. The volume fraction of SiC particles varies from top to bottom of the composite plate and the difference increases with the decrease of re-melting temperature. The interfacial structure of re-melted 2124Al–10 wt.%SiC composite was investigated using scanning electron microscopy, an electron probe micro-analyzer, a scanning transmission electron detector fitted with scanning electron microscopy and an X-ray energy dispersive spectrometer. It is found that a thick layer of reaction product is formed at the interface of composite after re-melting. The experimental results show that the reaction products at the interface are associated with high concentration of Cu, Mg, Si and C. At re-melting temperature, liquid Al reacts with SiC to form Al{sub 4}C{sub 3} and Al–Si eutectic phase or elemental Si at the interface. High concentration of Si at the interface indicates that SiC is dissociated during re-melting. The X-ray energy dispersive spectrometer analyses confirm that Mg- and Cu-enrich phases are formed at the interface region. The Mg is segregated at the interface region and formed MgAl{sub 2}O{sub 4} in the presence of oxygen. The several elements identified at the interface region indicate that different types of interfaces are formed in between Al matrix and SiC particles. The Al–Si eutectic phase is formed around SiC particles during re-melting which restricts the SiC dissolution. - Highlights: • Re-melted composite shows homogeneous particle

  5. Electronic conduction and microstructure in polymer composites filled with carbonaceous particles

    NASA Astrophysics Data System (ADS)

    Mdarhri, A.; Brosseau, C.; Zaghrioui, M.; El Aboudi, I.

    2012-08-01

    Physical and physico-chemical properties of polymer filled with carbon black (CB) particles, namely, the microstructure dependence of these properties, are not only interesting on their own but are particularly important for electronic applications as they can impose limits on the sensitivity of a device. With this purpose, we report on an experimental study of the structural and electrical properties of semi-crystalline ethylene-co-butyl acrylate polymer filled with conductive CB nano-particles. We found that the value of the direct current conductivity exhibits a jump of 12 orders of magnitude over a small change in CB concentration and is due to a percolation-like behavior. To assess the temperature evolution of supercolative samples, we present measurements of the conductivity as function of temperature. Above the glass transition temperature of the polymer, the CB network restricts the motions of the polymer chains. This behavior was ascribed to the change in CB mesostructure in the polymer matrix as probed by scanning electron microscopy and atomic force microscopy as well as to the difference in the thermal expansion between the two phases. In addition to the observed conductivity increase, the effect of adding CB particles in the polymer matrix is to increase the thermal stability as is probed by thermogravimetric analysis tests. The room temperature alternating current conductivity, studied over the frequency range from 100 Hz to 15 MHz, is interpreted as arising mainly from inter-aggregate polarization effects. By considering carefully the CB content of the alternating current conductivity, we found that our experimental data agree well with the Sheng's model of fluctuation-induced tunnelling of charge carriers over nanometric gaps between adjacent CB aggregates. For studying the filler content dependence of the effective permittivity, several mixing laws and effective medium theories have been used. The observed discrepancies between our experimental

  6. Nanocrystalline nickel ferrite particles synthesized by non-hydrolytic sol-gel method and their composite with biodegradable polymer.

    PubMed

    Yin, H; Casey, P S; Chow, G M

    2012-11-01

    Targeted drug delivery has been one of the most important biomedical applications for magnetic particles. Such applications require magnetic particles to have functionalized surfaces/surface coatings that facilitate their incorporation into a polymer matrix to produce a polymer composite. In this paper, nanocrystalline nickel ferrite particles with an oleic acid surface coating were synthesized using a non-hydrolytic sol-gel method and incorporated into a biodegradable polymer matrix, poly(D,L-lactide) PLA prepared using a double emulsion method. As-synthesized nickel ferrite particles had a multi-crystalline structure with chemically adsorbed oleic acid on their surface. After forming the PLA composite, nickel ferrite particles were encapsulated in PLA microspheres. At low nickel ferrite concentrations, composites showed very similar surface charges to that of PLA. The composites were magnetically responsive and increasing the nickel ferrite concentration was found to increase magnetization of the composite.

  7. Sol-gel derived nanoscale bioactive glass (NBG) particles reinforced poly(ε-caprolactone) composites for bone tissue engineering.

    PubMed

    Lei, Bo; Shin, Kwan-Ha; Noh, Da-Young; Jo, In-Hwan; Koh, Young-Hag; Kim, Hyoun-Ee; Kim, Sung Eun

    2013-04-01

    This study investigated the effect of the addition of sol-gel derived nanoscale bioactive glass (NBG) particles on the mechanical properties and biological performances of PCL polymer, in order to evaluate the potential applications of PCL/NBG composites for bone tissue regeneration. Regardless of the NBG contents (10, 20, and 30 wt.%), the NBG particles, which were synthesized through the sol-gel process using polyethylene glycol (PEG) polymer as a template, could be uniformly dispersed in the PCL matrix, while generating pores in the PCL/NBG composites. The elastic modulus of the PCL/NBG composites increased remarkably from 89±11 MPa to 383±50 MPa with increasing NBG content from 0 to 30 wt.%, while still showing good ultimate tensile strength in the range of 15-19 MPa. The hydrophilicity, water absorption and degradation behavior of the PCL/NBG composites were also enhanced by the addition of the NBG particles. Furthermore, the PCL/NBG composite with a NBG content of 30 wt.% showed significantly enhanced in vitro bioactivity and cellular response compared to those of the pure PCL.

  8. Strain measurement in a concrete beam by use of the Brillouin-scattering-based distributed fiber sensor with single-mode fibers embedded in glass fiber reinforced polymer rods and bonded to steel reinforcing bars

    NASA Astrophysics Data System (ADS)

    Zeng, Xiaodong; Bao, Xiaoyi; Chhoa, Chia Yee; Bremner, Theodore W.; Brown, Anthony W.; DeMerchant, Michael D.; Ferrier, Graham; Kalamkarov, Alexander L.; Georgiades, Anastasis V.

    2002-08-01

    The strain measurement of a 1.65-m reinforced concrete beam by use of a distributed fiber strain sensor with a 50-cm spatial resolution and 5-cm readout resolution is reported. The strain-measurement accuracy is plus-or-minus15 mu][epsilon (mum/m) according to the system calibration in the laboratory environment with non-uniform-distributed strain and plus-or-minus5 mu][epsilon with uniform strain distribution. The strain distribution has been measured for one-point and two-point loading patterns for optical fibers embedded in pultruded glass fiber reinforced polymer (GFRP) rods and those bonded to steel reinforcing bars. In the one-point loading case, the strain deviations are plus-or-minus7 and plus-or-minus15 mu][epsilon for fibers embedded in the GFRP rods and fibers bonded to steel reinforcing bars, respectively, whereas the strain deviation is plus-or-minus20 mu][epsilon for the two-point loading case.

  9. Self-Healing Nanofiber-Reinforced Polymer Composites. 1. Tensile Testing and Recovery of Mechanical Properties.

    PubMed

    Lee, Min Wook; An, Seongpil; Jo, Hong Seok; Yoon, Sam S; Yarin, Alexander L

    2015-09-09

    the composites reinforced by such mats. This is the first work, to the best of our knowledge, where self-healing nanofibers and composites based on them were developed, tested, and revealed restoration of mechanical properties (stiffness) in a 24 h rest period at room temperature.

  10. The microflow behavior and interphase characterization of fiber-reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Foley, Maureen Elizabeth

    reduction. This process was used to evaluate glass fiber reinforced epoxy and vinyl ester systems under quasi-static and cyclic loading as examples of the DILA capabilities.

  11. Experimental Study of the Flexural and Compression Performance of an Innovative Pultruded Glass-Fiber-Reinforced Polymer-Wood Composite Profile

    PubMed Central

    Qi, Yujun; Xiong, Wei; Liu, Weiqing; Fang, Hai; Lu, Weidong

    2015-01-01

    The plate of a pultruded fiber-reinforced polymer or fiber-reinforced plastic (FRP) profile produced via a pultrusion process is likely to undergo local buckling and cracking along the fiber direction under an external load. In this study, we constructed a pultruded glass-fiber-reinforced polymer-light wood composite (PGWC) profile to explore its mechanical performance. A rectangular cross-sectional PGWC profile was fabricated with a paulownia wood core, alkali-free glass fiber filaments, and unsaturated phthalate resin. Three-point bending and short column axial compression tests were conducted. Then, the stress calculation for the PGWC profile in the bending and axial compression tests was performed using the Timoshenko beam theory and the composite component analysis method to derive the flexural and axial compression rigidity of the profile during the elastic stress stage. The flexural capacity for this type of PGWC profile is 3.3-fold the sum of the flexural capacities of the wood core and the glass-fiber-reinforced polymer (GFRP) shell. The equivalent flexural rigidity is 1.5-fold the summed flexural rigidity of the wood core and GFRP shell. The maximum axial compressive bearing capacity for this type of PGWC profile can reach 1.79-fold the sum of those of the wood core and GFRP shell, and its elastic flexural rigidity is 1.2-fold the sum of their rigidities. These results indicate that in PGWC profiles, GFRP and wood materials have a positive combined effect. This study produced a pultruded composite material product with excellent mechanical performance for application in structures that require a large bearing capacity. PMID:26485431

  12. Experimental Study of the Flexural and Compression Performance of an Innovative Pultruded Glass-Fiber-Reinforced Polymer-Wood Composite Profile.

    PubMed

    Qi, Yujun; Xiong, Wei; Liu, Weiqing; Fang, Hai; Lu, Weidong

    2015-01-01

    The plate of a pultruded fiber-reinforced polymer or fiber-reinforced plastic (FRP) profile produced via a pultrusion process is likely to undergo local buckling and cracking along the fiber direction under an external load. In this study, we constructed a pultruded glass-fiber-reinforced polymer-light wood composite (PGWC) profile to explore its mechanical performance. A rectangular cross-sectional PGWC profile was fabricated with a paulownia wood core, alkali-free glass fiber filaments, and unsaturated phthalate resin. Three-point bending and short column axial compression tests were conducted. Then, the stress calculation for the PGWC profile in the bending and axial compression tests was performed using the Timoshenko beam theory and the composite component analysis method to derive the flexural and axial compression rigidity of the profile during the elastic stress stage. The flexural capacity for this type of PGWC profile is 3.3-fold the sum of the flexural capacities of the wood core and the glass-fiber-reinforced polymer (GFRP) shell. The equivalent flexural rigidity is 1.5-fold the summed flexural rigidity of the wood core and GFRP shell. The maximum axial compressive bearing capacity for this type of PGWC profile can reach 1.79-fold the sum of those of the wood core and GFRP shell, and its elastic flexural rigidity is 1.2-fold the sum of their rigidities. These results indicate that in PGWC profiles, GFRP and wood materials have a positive combined effect. This study produced a pultruded composite material product with excellent mechanical performance for application in structures that require a large bearing capacity.

  13. [Distribution of biological particles in two-phase systems of water soluble polymers and salts].

    PubMed

    Kononova, O A; Gorovaia, T B; Tiutiunnikov, A V; Prokhorova, N V; Tarasevich, I V; Khramov, E N

    2000-01-01

    The paper discusses the problems of purification of Provachek's rickettsias used to prepare typhus vaccines and diagnostic kits. The currently available agents contain many admixtures of rickettsias products, more commonly yolk and chick embryo yolk sack cell detritus, which make it impossible to determine the true antigenic properties of rickettsias in the context of protection and diagnosis. By applying the well-known principle of distribution of biological particles in the two-phase systems of water soluble polymers, investigations were made to examine the distribution of rickettsias and their infected biological mass in the system: polyethylene glycol-6600, sodium-500 dextran sulfate, potassium phosphate, sodium chloride in order to prepare agents of pure rickettsias. It has been found that rickettsias are distributed in the polymer-enriched phase, their number and the degree of purity when isolated from the infected biological mass depends on the capacity of an interphase wherein tissue detritus sorption occurs.

  14. Optical coherence tomography based particle image velocimetry (OCT-PIV) of polymer flows

    NASA Astrophysics Data System (ADS)

    Buchsbaum, A.; Egger, M.; Burzic, I.; Koepplmayr, T.; Aigner, M.; Miethlinger, J.; Leitner, M.

    2015-06-01

    The measurement of spatially resolved velocity distributions is crucial for modelling flow and for understanding properties of materials produced in extrusion processes. Traditional methods for flow visualization such as particle image velocimetry (PIV) rely on optically transparent media and cannot be applied to turbid polymer melts. Here we present optical coherence tomography as an imaging technique for PIV data processing that allows for measuring a sequence of time resolved images even in turbid media. Time-resolved OCT images of a glass-fibre polymer compound were acquired during an extrusion process in a slit die. The images are post-processed by ensemble cross-correlation to calculate spatially resolved velocity vector fields. The results compared well with velocity data obtained by Doppler-OCT. Overall, this new technique (OCT-PIV) represents an important extension of PIV to turbid materials by the use of OCT.

  15. Fatigue damage characterization of braided and woven fiber reinforced polymer matrix composites at room and elevated temperatures

    NASA Astrophysics Data System (ADS)

    Montesano, John

    The use of polymer matrix composites (PMC) for manufacturing primary load-bearing structural components has significantly increased in many industrial applications. Specifically in the aerospace industry, PMCs are also being considered for elevated temperature applications. Current aerospace-grade composite components subjected to fatigue loading are over-designed due to insufficient understanding of the material failure processes, and due to the lack of available generic fatigue prediction models. A comprehensive literature survey reveals that there are few fatigue studies conducted on woven and braided fabric reinforced PMC materials, and even fewer at elevated temperatures. It is therefore the objective of this study to characterize and subsequently model the elevated temperature fatigue behaviour of a triaxial braided PMC, and to investigate the elevated temperature fatigue properties of two additional woven PMCs. An extensive experimental program is conducted using a unique test protocol on the braided and woven composites, which consists of static and fatigue testing at various test temperatures. The development of mechanically-induced damage is monitored using a combination of non-destructive techniques which included infrared thermography, fiber optic sensors and edge replication. The observed microscopic damage development is quantified and correlated to the exhibited macroscopic material behaviour at all test temperatures. The fiber-dominated PMC materials considered in this study did not exhibit notable time- or temperature-dependent static properties. However, fatigue tests reveal that the local damage development is in fact notably influenced by temperature. The elevated temperature environment increases the toughness of the thermosetting polymers, which results in consistently slower fatigue crack propagation rates for the respective composite materials. This has a direct impact on the stiffness degradation rate and the fatigue lives for the braided

  16. Asymmetric lipid-polymer particles (LIPOMER) by modified nanoprecipitation: role of non-solvent composition.

    PubMed

    Jindal, Anil B; Devarajan, Padma V

    2015-07-15

    Asymmetric lipid polymer nanostructures (LIPOMER) comprising glyceryl monostearate (GMS) as lipid and Gantrez AN 119 (Gantrez) as polymer, revealed enhanced splenic accumulation. In the present paper, we attempt to explain the formation of asymmetric GMS LIPOMER using real time imaging. Particles were prepared by precipitation under static conditions using different non-solvent phase compositions. The process was video recorded and the videos converted to time elapsed images using the FFmpeg 0.10.2 software at 25 frames/sec. Non-solvent compositions comprising >30% of IPA/Acetone revealed significant stranding of the solvent phase and slower onset of precipitation(2-6s). At lower concentrations of IPA and acetone, and in non-solvent compositions comprising ethanol/water the stranding phenomenon was not evident. Further, rapid precipitation(<1 s) was evident. Nanoprecipitation based on the Marangoni effect is a result of diffusion stranding, interfacial turbulence, and mass transfer of solvent and non-solvent resulting in solute precipitation. Enhanced diffusion stranding favored by high interaction of GMS and Gantrez(low ΔPol), and the low solubility parameter(Δδtotal) and high mixing enthalpy(ΔHM) of GMS in IPA resulted in droplets with random shapes analogous to an amoeba with pseudopodia, which on precipitation formed asymmetric particles. Asymmetric particles could be readily designed through appropriate selection of solutes and non-solvent phase by modified nanoprecipitation.

  17. Trace Detection of Metalloporphyrin-Based Coordination Polymer Particles via Modified Surface-Enhanced Raman Scattering Assisted by Surface Metallization

    PubMed Central

    Caravella, Alessio

    2016-01-01

    This study proposed a facile method to detect metalloporphyrin-based coordination polymer particles (Z-CPPs) in aqueous solution by modified surface-enhanced Raman scattering (SERS). The SERS-active particles are photodeposited on the surface of Z-CPPs, offering an enhanced Raman signal for the trace detection of Z-CPPs. PMID:28115934

  18. Particle Restabilization in Silica/PEG/Ethanol Suspensions: How Strongly do Polymers Need To Adsorb To Stabilize Against Aggregation?

    SciTech Connect

    Kim, So Youn; Zukoski, Charles F.

    2014-09-24

    We study the effects of increasing the concentration of a low molecular weight polyethylene glycol on the stability of 44 nm diameter silica nanoparticles suspended in ethanol. Polymer concentration, c{sub p}, is increased from zero to that characterizing the polymer melt. Particle stability is accessed through measurement of the particle second-virial coefficient, B{sub -2}, performed by light scattering and ultrasmall angle X-ray scattering (USAXS). The results show that at low polymer concentration, c{sub p} < 3 wt %, B{sub -2} values are positive, indicating repulsive interactions between particles. B{sub -2} decreases at intermediate concentrations (3 wt % < c{sub p} < 50 wt %), and particles aggregates are formed. At high concentrations (50 wt % < c{sub p}) B{sub -2} increases and stabilizes at a value expected for hard spheres with a diameter near 44 nm, indicating the particles are thermodynamically stable. At intermediate polymer concentrations, rates of aggregation are determined by measuring time-dependent changes in the suspension turbidity, revealing that aggregation is slowed by the necessity of the particles diffusing over a repulsive barrier in the pair potential. The magnitude of the barrier passes through a minimum at c{sub p} {approx} 12 wt % where it has a value of {approx}12kT. These results are understood in terms of a reduction of electrostatic repulsion and van der Waals attractions with increasing c{sub p}. Depletion attractions are found to play a minor role in particle stability. A model is presented suggesting displacement of weakly adsorbed polymer leads to slow aggregation at intermediate concentration, and we conclude that a general model of depletion restabilization may involve increased strength of polymer adsorption with increasing polymer concentration.

  19. Effects of damage and thermal residual stresses on the overall elastoplastic behavior of particle-reinforced metal matrix composites

    NASA Astrophysics Data System (ADS)

    Liu, Haitao

    The objective of the present study is to investigate damage mechanisms and thermal residual stresses of composites, and to establish the frameworks to model the particle-reinforced metal matrix composites with particle-matrix interfacial debonding, particle cracking or thermal residual stresses. An evolutionary interfacial debonding model is proposed for the composites with spheroidal particles. The construction of the equivalent stiffness is based on the fact that when debonding occurs in a certain direction, the load-transfer ability will lose in that direction. By using this equivalent method, the interfacial debonding problem can be converted into a composite problem with perfectly bonded inclusions. Considering the interfacial debonding is a progressive process in which the debonding area increases in proportion to external loading, a progressive interfacial debonding model is proposed. In this model, the relation between external loading and the debonding area is established using a normal stress controlled debonding criterion. Furthermore, an equivalent orthotropic stiffness tensor is constructed based on the debonding areas. This model is able to study the composites with randomly distributed spherical particles. The double-inclusion theory is recalled to model the particle cracking problems. Cracks inside particles are treated as penny-shape particles with zero stiffness. The disturbed stress field due to the existence of a double-inclusion is expressed explicitly. Finally, a thermal mismatch eigenstrain is introduced to simulate the inconsistent expansions of the matrix and the particles due to the difference of the coefficients of thermal expansion. Micromechanical stress and strain fields are calculated due to the combination of applied external loads and the prescribed thermal mismatch eigenstrains. For all of the above models, ensemble-volume averaging procedures are employed to derive the effective yield function of the composites. Numerical

  20. Particle beam experiments for the analysis of reactive sputtering processes in metals and polymer surfaces.

    PubMed

    Corbella, Carles; Grosse-Kreul, Simon; Kreiter, Oliver; de los Arcos, Teresa; Benedikt, Jan; von Keudell, Achim

    2013-10-01

    A beam experiment is presented to study heterogeneous reactions relevant to plasma-surface interactions in reactive sputtering applications. Atom and ion sources are focused onto the sample to expose it to quantified beams of oxygen, nitrogen, hydrogen, noble gas ions, and metal vapor. The heterogeneous surface processes are monitored in situ by means of a quartz crystal microbalance and Fourier transform infrared spectroscopy. Two examples illustrate the capabilities of the particle beam setup: oxidation and nitriding of aluminum as a model of target poisoning during reactive magnetron sputtering, and plasma pre-treatment of polymers (PET, PP).

  1. Size-Dependent Strengthening Of Particle-Reinforced Aluminum Matrix Composites

    DTIC Science & Technology

    2011-05-01

    decay was observed in the dislocation density as the particle size increases and appears to saturate at approximately 16 m particle radius (figure 3b...It should be noted that prior to saturation , the 5% volume fraction curve is lower than that of the 20%. As a result, the strength of the 20...HOPPEL R KRAFT B LEAVY M SCHEIDLER T WEERASOORIYA C WILLIAMS (10 CPS) RDRL WMP C T BJERKE S SEGLETES G BOYCE R MUDD

  2. Laser induction hybrid rapid cladding of WC particles reinforced NiCrBSi composite coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Shengfeng; Dai, Xiaoqin

    2010-05-01

    In order to investigate the microstructure characteristics and properties of Ni-based WC composite coatings containing a relatively large amount of WC particles by laser induction hybrid rapid cladding (LIHRC) and compare to the individual laser cladding without preheating, Ni60A + 35 wt.% WC composite coatings are deposited on A3 steel plates by LIHRC and the individual laser cladding without preheating. The composite coating produced by the individual laser cladding without preheating exhibits many cracks and pores, while the smooth composite coating without cracks and pores is obtained by LIHRC. Moreover, the cast WC particles take on the similar dissolution characteristics in Ni60A + 35 wt.% WC composite coatings by LIHRC and the individual laser cladding without preheating. Namely, the completely dissolved WC particles interact with Ni-based alloy solvent to precipitate the blocky and herringbone carbides, while the partially dissolved WC particles still preserve the primary lamellar eutectic structure. A few WC particles are split at the interface of WC and W 2C, and then interact with Ni-based alloy solvent to precipitate the lamellar carbides. Compared with the individual laser cladding without preheating, LIHRC has the relatively lower temperature gradient and the relatively higher laser scanning speed. Therefore, LIHRC can produce the crack-free composite coating with relatively higher microhardness and relatively more homogeneous distribution of WC particles and is successfully applied to strengthen the corrugated roller, showing that LIHRC process has a higher efficiency and good cladding quality.

  3. Hierarchically functionalized magnetic core/multishell particles and their postsynthetic conversion to polymer capsules.

    PubMed

    Schmitt, Sophia; Silvestre, Martin; Tsotsalas, Manuel; Winkler, Anna-Lena; Shahnas, Artak; Grosjean, Sylvain; Laye, Fabrice; Gliemann, Hartmut; Lahann, Joerg; Bräse, Stefan; Franzreb, Matthias; Wöll, Christof

    2015-01-01

    The controlled synthesis of hierarchically functionalized core/multishell particles is highly desirable for applications in medicine, catalysis, and separation. Here, we describe the synthesis of hierarchically structured metal-organic framework multishells around magnetic core particles (magMOFs) via layer-by-layer (LbL) synthesis. The LbL deposition enables the design of multishell systems, where each MOF shell can be modified to install different functions. Here, we used this approach to create controlled release capsules, in which the inner shell serves as a reservoir and the outer shell serves as a membrane after postsynthetic conversion of the MOF structure to a polymer network. These capsules enable the controlled release of loaded dye molecules, depending on the surrounding media.

  4. Analysis of Particle Distribution in Milled Al-Based Composites Reinforced by B4C Nanoparticles

    NASA Astrophysics Data System (ADS)

    Alihosseini, Hamid; Dehghani, Kamran

    2017-03-01

    In the present work, high-energy ball milling was employed to synthesize Al-(5-10 wt.%)B4C nanocomposite. To do this, two sizes of particles of 50 nm as nanoparticles (NPs) and 50 μm as coarse particles (CPs) were used. The morphology and microstructure of the milled powders were characterized using particle size analyzer, SEM, TEM and EDX techniques. It was found that milling time, B4C particles size and their content strongly affect the characteristics of powders during milling process. The breaking and cold welding of powders was recognized as two main competitive actions during the milling process that influence the microstructural evolutions. It was found that the presence of CPs led to the formation of microcracks which promote the fracture process of Al powders. The dominated mechanisms during the fabrication of composites and nanocomposites were discussed. Also, the theoretical issues regarding the changes in morphology and distribution of B4C particles in CPs and NPs are clarified.

  5. Polymer-mediated nanorod self-assembly predicted by dissipative particle dynamics simulations.

    PubMed

    Khani, Shaghayegh; Jamali, Safa; Boromand, Arman; Hore, Michael J A; Maia, Joao

    2015-09-14

    Self-assembly of nanoparticles in polymer matrices is an interesting and growing subject in the field of nanoscience and technology. We report herein on modelling studies of the self-assembly and phase behavior of nanorods in a homopolymer matrix, with the specific goal of evaluating the role of deterministic entropic and enthalpic factors that control the aggregation/dispersion in such systems. Grafting polymer brushes from the nanorods is one approach to control/impact their self-assembly capabilities within a polymer matrix. From an energetic point of view, miscible interactions between the brush and the matrix are required for achieving a better dispersibility; however, grafting density and brush length are the two important parameters in dictating the morphology. Unlike in previous computational studies, the present Dissipative Particle Dynamics (DPD) simulation framework is able to both predict dispersion or aggregation of nanorods and determine the self-assembled structure, allowing for the determination of a phase diagram, which takes all of these factors into account. Three types of morphologies are predicted: dispersion, aggregation and partial aggregation. Moreover, favorable enthalpic interactions between the brush and the matrix are found to be essential for expanding the window for achieving a well-dispersed morphology. A three-dimensional phase diagram is mapped on which all the afore-mentioned parameters are taken into account. Additionally, in the case of immiscibility between brushes and the matrix, simulations predict the formation of some new and tunable structures.

  6. Modification of chitosan membranes with nanosilica particles as polymer electrolyte membranes

    NASA Astrophysics Data System (ADS)

    Kusumastuti, Ella; Siniwi, Widasari Trisna; Mahatmanti, F. Widhi; Jumaeri, Atmaja, Lukman; Widiastuti, Nurul

    2016-04-01

    Chitosan has been widely used as polymer matrix for Polymer Electrolyte Membrane (PEM) application replacing Nafion which has shortcomings in terms of high methanol permeability that degrades the performance of fuel cells. Chitosan membranes modification is performed by adding nanosilica to prevent methanol transport through the membrane. Nanosilica is synthesized by sol-gel method and the particle diameter is obtained by analysis using Breunner Emmet Teller (BET) that is 6.59 nm. Nanosilica is mixed with chitosan solution to obtain nanosilica-chitosan as polymer electrolyte membrane. The membranes are synthesized through phase inversion method with nanosilica composition including 0; 0.5; 1; 2; 3; 5; and 10% w/w of chitosan. Characterization of the membranes indicate that the results of water swelling, proton conductivity and methanol permeability of the membrane with 3% nanosilica respectively were 49.23%, 0.231 S/cm, and 5.43 x 10-7 cm2/s. Based on the results of membrane selectivity calculation, the optimum membrane is the composition of 3% nanosilica with value 5.91 x 105 S s cm-3. The results of functional groups analysis with FTIR showed that it was only physical interaction that occurred between chitosan and nanosilica since no significant changes found in peak around the wave number 1000-1250 cm--1.

  7. Investigation of Preparation and Mechanisms of a Dispersed Particle Gel Formed from a Polymer Gel at Room Temperature

    PubMed Central

    Zhao, Guang; Dai, Caili; Zhao, Mingwei; You, Qing; Chen, Ang

    2013-01-01

    A dispersed particle gel (DPG) was successfully prepared from a polymer gel at room temperature. The polymer gel system, morphology, viscosity changes, size distribution, and zeta potential of DPG particles were investigated. The results showed that zirconium gel systems with different strengths can be cross-linked within 2.5 h at low temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) results showed that the particles were polygonal particles with nano-size distribution. According to the viscosity changes, the whole preparation process can be divided into two major stages: the bulk gel cross-linking reaction period and the DPG particle preparation period. A polymer gel with a 3-dimensional network was formed in the bulk gel cross-linking reaction period whereas shearing force and frictional force were the main driving forces for the preparation of DPG particles, and thus affected the morphology of DPG particles. High shearing force and frictional force reduced the particle size distribution, and then decreased the zeta potential (absolute value). The whole preparation process could be completed within 3 h at room temperature. It could be an efficient and energy-saving technology for preparation of DPG particles. PMID:24324817

  8. Encapsulation of anticancer drug and magnetic particles in biodegradable polymer nanospheres.

    PubMed

    Koneracká, M; Múčková, M; Závišová, V; Tomašovičová, N; Kopčanský, P; Timko, M; Juríková, A; Csach, K; Kavečanský, V; Lancz, G

    2008-05-21

    In this study, we have prepared PLGA (poly-D,L-lactide-co-glycolide) nanospheres loaded with biocompatible magnetic fluid and anticancer drug taxol by a modified nanoprecipitation technique and investigated their magnetic properties. A magnetic fluid, MF-PEG, with a biocompatible layer of polyethylene glycol (PEG), was chosen as a magnetic carrier. The PLGA, whose copolymer ratio of D,L-lactide to glycolide is 85:15, was utilized as a capsulation material. Taxol, as an important anticancer drug, was chosen for its significant role against a wide range of tumours. The morphology and particle size distributions of the prepared nanospheres were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and showed a spherical shape of prepared nanospheres with size 250 nm. Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetry (TGA) analysis confirmed incorporation of magnetic particles and taxol into the PLGA polymer. The results showed good encapsulation with magnetite content 21.5 wt% and taxol 0.5 wt%. Magnetic properties of magnetic fluids and taxol within the PLGA polymer matrix were investigated by SQUID magnetometry from 4.2 to 300 K. The SQUID measurements showed superparamagnetism of prepared nanospheres with a blocking temperature of 160 K and saturation magnetization 1.4 mT.

  9. Consistent model reduction of polymer chains in solution in dissipative particle dynamics: Model description

    NASA Astrophysics Data System (ADS)

    Moreno, Nicolas; Nunes, Suzana P.; Calo, Victor M.

    2015-11-01

    We introduce a framework for model reduction of polymer chain models for dissipative particle dynamics (DPD) simulations, where the properties governing the phase equilibria such as the characteristic size of the chain, compressibility, density, and temperature are preserved. The proposed methodology reduces the number of degrees of freedom required in traditional DPD representations to model equilibrium properties of systems with complex molecules (e.g., linear polymers). Based on geometrical considerations we explicitly account for the correlation between beads in fine-grained DPD models and consistently represent the effect of these correlations in a reduced model, in a practical and simple fashion via power laws and the consistent scaling of the simulation parameters. In order to satisfy the geometrical constraints in the reduced model we introduce bond-angle potentials that account for the changes in the chain free energy after the model reduction. Following this coarse-graining process we represent high molecular weight DPD chains (i.e., ≥ 200 beads per chain) with a significant reduction in the number of particles required (i.e., ≥ 20 times the original system). We show that our methodology has potential applications modeling systems of high molecular weight molecules at large scales, such as diblock copolymer and DNA.

  10. Mass spectra of neutral particles released during electrical breakdown of thin polymer films

    NASA Technical Reports Server (NTRS)

    Kendall, B. R. F.

    1985-01-01

    A special type of time-of-flight mass spectrometer triggered from the breakdown event was developed to study the composition of the neutral particle flux released during the electrical breakdown of polymer films problem. Charge is fed onto a metal-backed polymer surface by a movable smooth platinum contact. A slowly increasing potential from a high-impedance source is applied to the contact until breakdown occurs. The breakdown characteristics is made similar to those produced by an electron beam charging system operating at similar potentials. The apparatus showed that intense instantaneous fluxes of neutral particles are released from the sites of breakdown events. For Teflon FEP films of 50 and 75 microns thickness the material released consists almost entirely of fluorocarbon fragments, some of them having masses greater than 350 atomic mass units amu, while the material released from a 50 micron Kapton film consists mainly of light hydrocarbons with masses at or below 44 amu, with additional carbon monoxide and carbon dioxide. The apparatus is modified to allow electron beam charging of the samples.

  11. The Microstructure-Processing-Property Relationships in an Al Matrix Composite System Reinforced by Al-Cu-Fe Alloy Particles

    SciTech Connect

    Tang, Fei

    2004-01-01

    Metal matrix composites (MMC), especially Al matrix composites, received a lot of attention during many years of research because of their promise for the development of automotive and aerospace materials with improved properties and performance, such as lighter weight and better structural properties, improved thermal conductivity and wear resistance. In order to make the MMC materials more viable in various applications, current research efforts on the MMCs should continue to focus on two important aspects, including improving the properties of MMCs and finding more economical techniques to produce MMCs. Solid state vacuum sintering was studied in tap densified Al powder and in hot quasi-isostatically forged samples composed of commercial inert gas atomized or high purity Al powder, generated by a gas atomization reaction synthesis (GARS) technique. The GARS process results in spherical Al powder with a far thinner surface oxide. The overall results indicated the enhanced ability of GARS-processed Al and Al alloy powders for solid state sintering, which may lead to simplification of current Al powder consolidation processing methods. Elemental Al-based composites reinforced with spherical Al-Cu-Fe alloy powders were produced by quasi-isostatic forging and vacuum hot pressing (VHP) consolidation methods. Microstructures and tensile properties of AYAl-Cu-Fe composites were characterized. It was proved that spherical Al-Cu-Fe alloy powders can serve as an effective reinforcement particulate for elemental Al-based composites, because of their high hardness and a preferred type of matrix/reinforcement interfacial bonding, with reduced strain concentration around the particles. Ultimate tensile strength and yield strength of the composites were increased over the corresponding Al matrix values, far beyond typical observations. This remarkable strengthening was achieved without precipitation hardening and without severe strain hardening during consolidation because of

  12. Exploiting fluorescent polymers to probe the self-assembly of virus-like particles.

    PubMed

    Cadena-Nava, Ruben D; Hu, Yufang; Garmann, Rees F; Ng, Benny; Zelikin, Alexander N; Knobler, Charles M; Gelbart, William M

    2011-03-17

    The inside surfaces of the protein shells of many viruses are positively charged, thereby enhancing the self-assembly of capsid proteins around their (oppositely charged) RNA genome. These proteins have been shown to organize similarly around a variety of nonbiological, negatively charged, polymers, for example, poly(styrene sulfonate) (PSS), forming virus-like particles (VLPs). We have demonstrated recently that the VLPs formed from cowpea chlorotic mottle virus (CCMV) capsid protein increase in size (from T=2 to T=3 structures) upon increase in PSS molecular weight (from 400 kDa to 3.4 MDa), and that the total charge on the PSS exceeds that of the capsid protein by as much as a factor of 9. Here, we extend studies of this kind to PSS molecules that are sufficiently small that two or more can be packaged into VLPs. The use of 38 kDa PSS polymers that have been fluorescently labeled with Rhodamine B allows us to determine the number of PSS molecules per capsid. Electron micrographs of the VLPs show a bimodal distribution of particle diameters, with one peak centered around 19 nm, typical of a T=1 triangulation number, and the other around 21 nm, consistent with a pseudo T=2 structure; increasing the molar ratio of protein to PSS in the reaction mix shifts the VLP distribution from T=1 to T=2 structures. By combining fluorescence and gel electrophoresis measurements, it is determined that, on average, there are two polymers in each T=1 capsid and three in each T=2, with the PSS charge less than that of the capsid protein by as much as a factor of 2. VLPs of this kind provide a versatile model system for determining the principles underlying self-assembly of controlled numbers of cargo molecules in nanocontainers of increasing size.

  13. Silica hybrid particles with nanometre polymer shells and their influence on the toughening of polypropylene.

    PubMed

    Zheng, Jing-Zhi; Zhou, Xing-Ping; Xie, Xiao-Lin; Mai, Yiu-Wing

    2010-10-01

    Colloidal silica particles were synthesized by the sol-gel process and then modified with 3-methacryloxypropyltrimethoxysilane (γ-MPS) to induce vinyl groups on the surface of the silica particles. By means of in situ emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA), a series of core-shell silica hybrid particles with nanometre poly(MMA-co-BA) shells were fabricated, which were subsequently compounded with isotactic polypropylene (PP) in the molten state. Upon increasing the feed silica : monomer ratio from 1 : 1 to 4 : 1, the poly(MMA-co-BA) shell thickness on the silica core decreased from 50 nm to 10 nm. Owing to the existence of the nanometre poly(MMA-co-BA) shells, the silica hybrid particles were monodispersed in the PP matrix, causing homogeneous debonding at the PP/silica interface, followed by plastic void expansion and matrix shear yielding during impact fracture. These deformation mechanisms greatly toughened the PP-silica composites. A critical shell thickness of poly(MMA-co-BA) was needed to achieve optimal mechanical properties. That is, when the polymer shell thickness was 15 nm, compared to pure PP, the impact toughness of the PP-silica composite was more than doubled with little degradation of tensile strength.

  14. Facile hierarchical assembly of gold particle decorated conductive polymer nanofibers for electrochemical sensing

    NASA Astrophysics Data System (ADS)

    Dai, Minhui; Chen, Juhong; Goddard, Julie M.; Nugen, Sam R.

    2017-02-01

    In this study, we successfully applied vapor-phase polymerization towards the synthesis of PEDOT nanofibers which were subsequently functionalized with gold particles and used as electrodes for electrochemical sensing. Two methods were used to synthesize the PEDOT nanofibers including (1) electrospinning followed by vapor-phase polymerization (EVP), and (2) one-step vapor-phase polymerization (OSVP). The average diameter of EVP fibers was approximately 350 nm, and OSVP was approximately 200 nm. Gold particles (∼500 nm) were synthesized by an oxidation-reduction reaction between gold precursors and residue EDOT monomers on the surface of the PEDOT nanofibers. In order to investigate the electrochemical performance of these electrodes, ascorbic acid was chosen as an analyte model. Our results indicated that PEDOT nanofiber electrodes showed an enhanced response with respect to bare gold electrodes. Furthermore, the OSVP PEDOT nanofibers with gold particles demonstrated the highest sensitivity at low ascorbic acid concentrations. These hierarchically assembled, gold particle-decorated, conductive polymer nanofibers were further fabricated into flexible electrodes, demonstrating a potential in advanced applications such as wearable electronics.

  15. Dynamics of particle chain formation in a liquid polymer under ac electric field: modeling and experiments

    NASA Astrophysics Data System (ADS)

    Belijar, G.; Valdez-Nava, Z.; Diaham, S.; Laudebat, L.; Jones, T. B.; Lebey, T.

    2017-01-01

    Polymer/ceramic composite materials are of great interest for their many potential applications because of their ability to combine at least two properties of the constitutive elements: particles and matrix. In most cases, such enhanced properties are required only in one direction. Orthotropic materials can be elaborated by applying an ac electric field to form particle chain structures in the direction of the electric field due to the dielectrophoretic interactions affecting the particles. However, there is still a lack in the understanding of the impact of the structures on the properties of the material. The aim of this study is to propose a predictive model for the evolution of the permittivity during the chain formation, by including micro- and macroscopic phenomena. The chaining model is based on dipole-dipole interactions and the dielectric permittivity is computed through a finite element method. In parallel, an experimental study is performed with online permittivity measurements of composites during chaining. The developed model is able to predict the experimental results from 1 vol% while taking into account parameters such as the resin viscosity and permittivity and the transient evolution of the applied electric field. The formation of particle chains inside a material has applications in many domains such as electrorheological fluids, anisotropic composites, self-recovery materials etc. Such a developed model is a valuable tool for the tailoring of materials.

  16. A distant real-time radar NDE technique for the in-depth inspection of glass fiber reinforced polymer-retrofitted concrete columns

    NASA Astrophysics Data System (ADS)

    Yu, Tzu-Yang; Buyukozturk, Oral

    2008-03-01

    A novel real-time radar NDE technique for the in-depth inspection of glass fiber reinforced polymer (GFRP)-retrofitted concrete columns is proposed. In this technique, continuous wave radar signals are transmitted in the far-field region (distant inspection), and reflected signals are collected by the same signal transmitter. Collected radar signals are processed by tomographic reconstruction methods for real-time image reconstruction. In-depth condition in the near-surface region of GFRP-concrete systems is revealed and evaluated by reconstructed images.

  17. Pulsed micro-laser line thermography on submillimeter porosity in carbon fiber reinforced polymer composites: experimental and numerical analyses for the capability of detection.

    PubMed

    Zhang, Hai; Fernandes, Henrique; Djupkep Dizeu, Frank Billy; Hassler, Ulf; Fleuret, Julien; Genest, Marc; Ibarra-Castanedo, Clemente; Robitaille, François; Joncas, Simon; Maldague, Xavier

    2016-12-01

    In this article, pulsed micro-laser line thermography (pulsed micro-LLT) was used to detect the submillimeter porosities in a 3D preformed carbon fiber reinforced polymer composite specimen. X-ray microcomputed tomography was used to verify the thermographic results. Then, finite element analysis was performed on the corresponding models on the basis of the experimental results. The same infrared image processing techniques were used for the experimental and simulation results for comparative purposes. Finally, a comparison of experimental and simulation postprocessing results was conducted. In addition, an analysis of probability of detection was performed to evaluate the detection capability of pulsed micro-LLT on submillimeter porosity.

  18. Probing effects of polymer adsorption in colloidal particle suspensions by light scattering as relevant for the aquatic environment: An overview.

    PubMed

    Tiraferri, Alberto; Borkovec, Michal

    2015-12-01

    Modification of particle surfaces by adsorption of polymers is a process that governs particle behavior in aqueous environmental systems. The present article briefly reviews the current understanding of the adsorption mechanisms and the properties of the resulting layers, and it discusses two environmentally relevant cases of particle modification by polymers. In particular, the discussion focuses on the usefulness of methods based on light scattering to probe such adsorbed layers together with the resulting properties of the particle suspensions, and it highlights advantages and disadvantages of these techniques. Measurement of the electrophoretic mobility allows to follow the development of the adsorption layer and to characterize the charge of the modified particles. At saturation, the surface charge is governed by the charge of the adsorbed film. Dynamic light scattering provides information on the film thickness and on the behavior of the modified suspensions. The charge and the structure of the adsorbed layer influence the stability of the particles, as well as the applicability of the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). This fundamental knowledge is presented in the light of environmental systems and its significance for applied systems is underlined. In particular, the article discusses two examples of environmental processes involving adsorption of polymers, namely, the modification of particles by natural adsorption of humic substances and the tailoring of surface properties of iron-based particles used to remediate contaminated aquifers.

  19. Anterior cervical corpectomy: review and comparison of results using titanium mesh cages and carbon fibre reinforced polymer cages.

    PubMed

    Kabir, Syed M R; Alabi, J; Rezajooi, Kia; Casey, Adrian T H

    2010-10-01

    Different types of cages have recently become available for reconstruction following anterior cervical corpectomy. We review the results using titanium mesh cages (TMC) and stackable CFRP (carbon fibre reinforced polymer) cages. Forty-two patients who underwent anterior cervical corpectomy between November 2001 and September 2008 were retrospectively reviewed. Pathologies included cervical spondylotic myelopathy (CSM), cervical radiculopathy, OPLL (ossified posterior longitudinal ligament), metastasis/primary bone tumour, rheumatoid arthritis and deformity correction. All patients were evaluated clinically and radiologically. Outcome was assessed on the basis of the Odom's criteria, neck disability index (NDI) and myelopathy disability index (MDI). Mean age was 60 years and mean follow-up was 1½ years. Majority of the patients had single-level corpectomy. Twenty-three patients had TMC cages while 19 patients had CFRP cages. The mean subsidence noted with TMC cage was 1.91 mm, while with the stackable CFRP cage it was 0.5 mm. This difference was statistically significant (p < 0.05). However, there was no statistically significant correlation noted between subsidence and clinical outcome (p > 0.05) or between subsidence and post-operative sagittal alignment (p > 0.05) in either of the groups. Three patients had significant subsidence (> 3 mm), one of whom was symptomatic. There were no hardware-related complications. On the basis of the Odom's criterion, 9 patients (21.4%) had an excellent outcome, 14 patients (33.3%) had a good outcome, 9 patients (21.4%) had a fair outcome and 5 patients (11.9%) had a poor outcome, i.e. symptoms and signs unchanged or exacerbated. Mean post-operative NDI was 26.27% and mean post-operative MDI was 19.31%. Fusion was noted in all 42 cases. Both TMC and stackable CFRP cages provide solid anterior column reconstruction with good outcome following anterior cervical corpectomy. However, more subsidence is noted with TMC cages though

  20. Acoustic emission and acousto-ultrasonic signature analysis of failure mechanisms in carbon fiber reinforced polymer materials

    NASA Astrophysics Data System (ADS)

    Carey, Shawn Allen

    Fiber reinforced polymer composite materials, particularly carbon (CFRPs), are being used for primary structural applications, particularly in the aerospace and naval industries. Advantages of CFRP materials, compared to traditional materials such as steel and aluminum, include: light weight, high strength to weight ratio, corrosion resistance, and long life expectancy. A concern with CFRPs is that despite quality control during fabrication, the material can contain many hidden internal flaws. These flaws in combination with unseen damage due to fatigue and low velocity impact have led to catastrophic failure of structures and components. Therefore a large amount of research has been conducted regarding nondestructive testing (NDT) and structural health monitoring (SHM) of CFRP materials. The principal objective of this research program was to develop methods to characterize failure mechanisms in CFRP materials used by the U.S. Army using acoustic emission (AE) and/or acousto-ultrasonic (AU) data. Failure mechanisms addressed include fiber breakage, matrix cracking, and delamination due to shear between layers. CFRP specimens were fabricated and tested in uniaxial tension to obtain AE and AU data. The specimens were designed with carbon fibers in different orientations to produce the different failure mechanisms. Some specimens were impacted with a blunt indenter prior to testing to simulate low-velocity impact. A signature analysis program was developed to characterize the AE data based on data examination using visual pattern recognition techniques. It was determined that it was important to characterize the AE event , using the location of the event as a parameter, rather than just the AE hit (signal recorded by an AE sensor). A back propagation neural network was also trained based on the results of the signature analysis program. Damage observed on the specimens visually with the aid of a scanning electron microscope agreed with the damage type assigned by the

  1. Steady shear rheometry of dissipative particle dynamics models of polymer fluids in reverse Poiseuille flow.

    PubMed

    Fedosov, Dmitry A; Karniadakis, George Em; Caswell, Bruce

    2010-04-14

    Polymer fluids are modeled with dissipative particle dynamics (DPD) as undiluted bead-spring chains and their solutions. The models are assessed by investigating their steady shear-rate properties. Non-Newtonian viscosity and normal stress coefficients, for shear rates from the lower to the upper Newtonian regimes, are calculated from both plane Couette and plane Poiseuille flows. The latter is realized as reverse Poiseuille flow (RPF) generated from two Poiseuille flows driven by uniform body forces in opposite directions along two-halves of a computational domain. Periodic boundary conditions ensure the RPF wall velocity to be zero without density fluctuations. In overlapping shear-rate regimes the RPF properties are confirmed to be in good agreement with those calculated from plane Couette flow with Lees-Edwards periodic boundary conditions (LECs), the standard virtual rheometer for steady shear-rate properties. The concentration and the temperature dependence of the properties of the model fluids are shown to satisfy the principles of concentration and temperature superposition commonly employed in the empirical correlation of real polymer-fluid properties. The thermodynamic validity of the equation of state is found to be a crucial factor for the achievement of time-temperature superposition. With these models, RPF is demonstrated to be an accurate and convenient virtual rheometer for the acquisition of steady shear-rate rheological properties. It complements, confirms, and extends the results obtained with the standard LEC configuration, and it can be used with the output from other particle-based methods, including molecular dynamics, Brownian dynamics, smooth particle hydrodynamics, and the lattice Boltzmann method.

  2. Dissipative particle dynamics study of translational diffusion of rigid-chain rodlike polymer in nematic phase

    NASA Astrophysics Data System (ADS)

    Zhao, Tongyang; Wang, Xiaogong

    2013-09-01

    In this study, dissipative particle dynamics (DPD) method was employed to investigate the translational diffusion of rodlike polymer in its nematic phase. The polymer chain was modeled by a rigid rod composed of consecutive DPD particles and solvent was represented by independent DPD particles. To fully understand the translational motion of the rods in the anisotropic phase, four diffusion coefficients, D_{||}u, D_ bot u, D_{||}n, D_ bot n were obtained from the DPD simulation. By definition, D_{||}n and D_ bot n denote the diffusion coefficients parallel and perpendicular to the nematic director, while D_{||}u and D_ bot u denote the diffusion coefficients parallel and perpendicular to the long axis of a rigid rod u. In the simulation, the velocity auto-correlation functions were used to calculate the corresponding diffusion coefficients from the simulated velocity of the rods. Simulation results show that the variation of orientational order caused by concentration and temperature changes has substantial influences on D_{||}u and D_ bot u. In the nematic phase, the changes of concentration and temperature will result in a change of local environment of rods, which directly influence D_{||}u and D_ bot u. Both D_{||}n and D_ bot n can be represented as averages of D_{||}u and D_ bot u, and the weighted factors are functions of the orientational order parameter S2. The effect of concentration and temperature on D_{||}n and D_ bot n demonstrated by the DPD simulation can be rationally interpreted by considering their influences on D_{||}u, D_ bot u and the order parameter S2.

  3. Understanding mechanical properties of polymer nanocomposites with molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Sen, Suchira

    Equilibrium Molecular Dynamics (MD) simulations are used extensively to study various aspects of polymer nanocomposite (PNC) behavior in the melt state---the key focus is on understanding mechanisms of mechanical reinforcement. Mechanical reinforcement of the nanocomposite is believed to be caused by the formation of a network-like structure---a result of polymer chains bridging particles to introduce network elasticity. In contrast, in traditional composites, where the particle size range is hundreds of microns and high loadings of particle are used, the dominant mechanism is the formation of a percolated filler structure. The difference in mechanism with varying particle sizes, at similar particle loading, arises from the polymer-particle interfacial area available, which increases dramatically as the particle size decreases. Our interest in this work is to find (a) the kind of polymer-particle interactions necessary to facilitate the formation of a polymer network in a nanocomposite, and (b) the reinforcing characteristics of such a polymer network. We find that very strong polymer-particle binding is necessary to create a reinforcing network. The strength of the binding has to be enough to immobilize polymer on the particle surface for timescales comparable and larger than the terminal relaxation time of the stress of the neat melt. The second finding, which is a direct outcome of very strong binding, is that the method of preparation plays a critical role in determining the reinforcement of the final product. The starting conformations of the polymer chains determine the quality of the network. The strong binding traps the polymer on the particle surface which gets rearranged to a limited extent, within stress relaxation times. Significant aging effects are seen in system relaxation; the inherent non-equilibrium consequences of such strong binding. The effect of the polymer immobilization slows down other relaxation processes. The diffusivity of all chains is

  4. Space science applications for conducting polymer particles: synthetic mimics for cosmic dust and micrometeorites.

    PubMed

    Fielding, Lee A; Hillier, Jon K; Burchell, Mark J; Armes, Steven P

    2015-12-11

    Over the last decade or so, a range of polypyrrole-based particles have been designed and evaluated for space science applications. This electrically conductive polymer enables such particles to efficiently acquire surface charge, which in turn allows their acceleration up to the hypervelocity regime (>1 km s(-1)) using a Van de Graaff accelerator. Either organic latex (e.g. polystyrene or poly(methyl methacrylate)) or various inorganic materials (such as silica, olivine or pyrrhotite) can be coated with polypyrrole; these core-shell particles are useful mimics for understanding the hypervelocity impact ionisation behaviour of micro-meteorites (a.k.a. cosmic dust). Impacts on metal targets at relatively low hypervelocities (<10 km s(-1)) generate ionic plasma composed mainly of molecular fragments, whereas higher hypervelocities (>10 km s(-1)) generate predominately atomic species, since many more chemical bonds are cleaved if the particles impinge with higher kinetic energy. Such fundamental studies are relevant to the calibration of the cosmic dust analyser (CDA) onboard the Cassini spacecraft, which was designed to determine the chemical composition of Saturn's dust rings. Inspired by volcanism observed for one of the Jupiter's moons (Io), polypyrrole-coated sulfur-rich latexes have also been designed to help space scientists understand ionisation spectra originating from sulfur-rich dust particles. Finally, relatively large (20 μm diameter) polypyrrole-coated polystyrene latexes have proven to be useful for understanding the extent of thermal ablation of organic projectiles when fired at ultralow density aerogel targets at up to 6.1 km s(-1) using a Light Gas Gun. In this case, the sacrificial polypyrrole overlayer simply provides a sensitive spectroscopic signature (rather than a conductive overlayer), and the scientific findings have important implications for the detection of organic dust grains during the Stardust space mission.

  5. Superficially porous particles with 1000Å pores for large biomolecule high performance liquid chromatography and polymer size exclusion chromatography.

    PubMed

    Wagner, Brian M; Schuster, Stephanie A; Boyes, Barry E; Shields, Taylor J; Miles, William L; Haynes, Mark J; Moran, Robert E; Kirkland, Joseph J; Schure, Mark R

    2017-03-17

    To facilitate mass transport and column efficiency, solutes must have free access to particle pores to facilitate interactions with the stationary phase. To ensure this feature, particles should be used for HPLC separations which have pores sufficiently large to accommodate the solute without restricted diffusion. This paper describes the design and properties of superficially porous (also called Fused-Core(®), core shell or porous shell) particles with very large (1000Å) pores specifically developed for separating very large biomolecules and polymers. Separations of DNA fragments, monoclonal antibodies, large proteins and large polystyrene standards are used to illustrate the utility of these particles for efficient, high-resolution applications.

  6. Synthesis of Zwitterionic Polymer Particles via Combined Distillation Precipitation Polymerization and Click Chemistry for Highly Efficient Enrichment of Glycopeptide.

    PubMed

    Liu, Jianxi; Yang, Kaiguang; Shao, Wenya; Li, Senwu; Wu, Qi; Zhang, Shen; Qu, Yanyan; Zhang, Lihua; Zhang, Yukui

    2016-08-31

    Because of the low abundance of glycopeptide in natural biological samples, methods for efficient and selective enrichment of glycopeptides play a significant role in mass spectrometry (MS)-based glycoproteomics. In this study, a novel kind of zwitterionic hydrophilic interaction chromatography polymer particles, namely, poly(N,N-methylenebisacrylamide-co-methacrylic acid)@l-Cys (poly(MBAAm-co-MAA)@l-Cys), for the enrichment of glycopeptides was synthesized by a facile and efficient approach that combined distillation precipitation polymerization (DPP) and "thiol-ene" click reaction. In the DPP approach, residual vinyl groups explored outside the core with high density, then the functional ligand cysteine was immobilized on