The effect of woven and non-woven fiber structure on mechanical properties polyester composite reinforced kenaf

NASA Astrophysics Data System (ADS)

Ratim, S.; Bonnia, N. N.; Surip, S. N.

2012-07-01

The effects of woven and non-woven kenaf fiber on mechanical properties of polyester composites were studied at different types of perform structures. Composite polyester reinforced kenaf fiber has been prepared via hand lay-up process by varying fiber forms into plain weave, twill and mats structure. The reinforcing efficiency of different fiber structure was compared with control of unreinforced polyester sample. It was found that the strength and stiffness of the composites are largely affected by fiber structure. A maximum value for tensile strength of composite was obtained for twill weave pattern of fiber structure while no significant different for plain weave and mat structure. The elastic modulus of composite has shown some improvement on plain and twill weave pattern. Meanwhile, lower value of modulus elasticity achieved by mats structure composite as well as control sample. The modulus of rupture and impact resistance were also analyzed. The improvement of modulus of rupture value can be seen on plain and twill weave pattern. However impact resistance doesn't show significant improvement in all types of structure except for mat fiber. The mechanical properties of kenaf fiber reinforced polyester composite found to be increased with woven and non-woven fiber structures in composite.

A bioinspired study on the compressive resistance of helicoidal fibre structures

NASA Astrophysics Data System (ADS)

Tan, Ting; Ribbans, Brian

2017-10-01

Helicoidal fibre structures are widely observed in natural materials. In this paper, an integrated experimental and analytical approach was used to investigate the compressive resistance of helicoidal fibre structures. First, helicoidal fibre-reinforced composites were created using three-dimensionally printed helicoids and polymeric matrices, including plain, ring-reinforced and helix-reinforced helicoids. Then, load-displacement curves under monotonic compression tests were collected to measure the compressive strengths of helicoidal fibre composites. Fractographic characterization was performed using an X-ray microtomographer and scanning electron microscope, through which crack propagations in helicoidal structures were illustrated. Finally, mathematical modelling was performed to reveal the essential fibre architectures in the compressive resistance of helicoidal fibre structures. This work reveals that fibre-matrix ratios, helix pitch angles and interlayer rotary angles are critical to the compressive resistance of helicoidal structures.

Formation of structure, phase composition and properties of electro explosion resistant coatings using electron-beam processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romanov, Denis A., E-mail: romanov-da@physics.sibsiu.ru, E-mail: kos2906@mail.ru, E-mail: budovskih-ea@physics.sibsiu.ru, E-mail: gromov@physics.sibsiu.ru, E-mail: da-rom@live.ru; Sosnin, Kirill V., E-mail: romanov-da@physics.sibsiu.ru, E-mail: kos2906@mail.ru, E-mail: budovskih-ea@physics.sibsiu.ru, E-mail: gromov@physics.sibsiu.ru, E-mail: da-rom@live.ru; Budovskikh, Evgenij A., E-mail: romanov-da@physics.sibsiu.ru, E-mail: kos2906@mail.ru, E-mail: budovskih-ea@physics.sibsiu.ru, E-mail: gromov@physics.sibsiu.ru, E-mail: da-rom@live.ru

2014-11-14

For the first time, the high intensity electron beam modification of electroexplosion composite coatings of MoCu, MoCCu, WCu, WCCu and TiB{sub 2}Cu systems was done. The studies of phase and elemental composition, defective structure conditions of these coatings were carried out. The regimes of electron-beam processing making possible to form the dense, specular luster surface layers having a submicrocrystalline structure were revealed. It was established that electron-beam processing of elecroexplosion spraying of layer of elecroexplosion spraying carried out in the regime of melting results in the formation of structurally and contrationally homogeneous surface layer. Investigation of the effect of electron-beammore » processing of electroexplosion electroerosion resistant coatings on their tribological properties (wear resistanse and coefficient of friction) and electroerosion resistance was done. It was shown that all the examined costings demonstrate the increase of electroerosion resistance in spark erosion up to 10 times.« less

Creep of Heat-Resistant Composites of an Oxide-Fiber/Ni-Matrix Family

NASA Astrophysics Data System (ADS)

Mileiko, S. T.

2001-09-01

A creep model of a composite with a creeping matrix and initially continuous elastic brittle fibers is developed. The model accounts for the fiber fragmentation in the stage of unsteady creep of the composite, which ends with a steady-state creep, where a minimum possible average length of the fiber is achieved. The model makes it possible to analyze the creep rate of the composite in relation to such parameters of its structure as the statistic characteristics of the fiber strength, the creep characteristics of the matrix, and the strength of the fiber-matrix interface, the latter being of fundamental importance. A comparison between the calculation results and the experimental ones obtained on composites with a Ni-matrix and monocrystalline and eutectic oxide fibers as well as on sapphire fiber/TiAl-matrix composites shows that the model is applicable to the computer simulation of the creep behavior of heat-resistant composites and to the optimization of the structure of such composites. By combining the experimental data with calculation results, it is possible to evaluate the heat resistance of composites and the potential of oxide-fiber/Ni-matrix composites. The composite specimens obtained and tested to date reveal their high creep resistance up to a temperature of 1150°C. The maximum operating temperature of the composites can be considerably raised by strengthening the fiber-matrix interface.

Effects of Co contents on the microstructures and properties of the electrodeposited NiCo–Zr composite coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Fei; Jiang, Chuanhai, E-mail: chuanhaijiang1963@163.com; Zhao, Yuantao

2015-05-15

Highlights: • The novel NiCo–Zr coatings were prepared by electro-deposition. • Surface morphology, crystal structure, grain size and microstrain were examined. • Texture, residual stress and corrosion resistance were investigated. • Addition of Co increased the hardness and corrosion resistance of the coatings. - Abstract: In this study, the NiCo–Zr composite coatings were prepared from the electrolytes with different Co{sup 2+} concentrations by electrodeposition method. The effects of Co contents on the crystal structure, surface morphology, grain size, microstrain and residual stress were examined by X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX) andmore » atomic force microscope (AFM). The corrosion resistance of the composite coatings was also examined by the potentiodynamic polarization and electrochemical impedance (EIS) measurements. The results revealed that the crystal structures of the coatings were dependent on the Co contents and addition of Co content of 58 wt% resulted in the formation of hexagonal (hcp) Co. The increasing Co contents in the NiCo–Zr composite coatings resulted in the smoother and more compact surface, decreased the grain size and increased the microstrain. The micro-hardness and residual stress also increased with increasing Co contents. The addition of Co increased the corrosion resistance of the NiCo–Zr composite coatings compared with the Ni–Zr coating while the corrosion resistance of the NiCo–Zr composite coatings decreased as the Co contents increased.« less

Prepreg effects on honeycomb composite manufacturing

NASA Astrophysics Data System (ADS)

Martin, Cary Joseph

Fiber reinforced composites offer many advantages over traditional materials and are widely utilized in aerospace applications. Advantages include a high stiffness to weight ratio and excellent fatigue resistance. However, the pace of new implementation is slow. The manufacturing processes used to transform composite intermediates into final products are poorly understood and are a source of much variability. This limits new implementation and increases the manufacturing costs of existing designs. One such problem is honeycomb core crush, in which a core-stiffened structure collapses during autoclave manufacture, making the structure unusable and increasing the overall manufacturing cost through increased scrap rates. Consequently, the major goal of this research was to investigate the scaling of core crush from prepreg process-structure-property relations to commercial composite manufacture. The material dependent nature of this defect was of particular interest. A methodology and apparatus were developed to measure the frictional resistance of prepreg materials under typical processing conditions. Through a characterization of commercial and experimental prepregs, it was found that core crush behavior was the result of differences in prepreg frictional resistance. This frictional resistance was related to prepreg morphology and matrix rheology and elasticity. Resin composition and prepreg manufacturing conditions were also found to affect manufacturing behavior. Mechanical and dimensional models were developed and demonstrated utility for predicting this crushing behavior. Collectively, this work explored and identified the process-structure-property relations as they relate to the manufacture of composite materials and suggested several avenues by which manufacturing-robust materials may be developed.

Review of Aircraft Crash Structural Response Research.

DTIC Science & Technology

1982-08-01

structures consisting of conventional built-up metallic construction and those consisting of advanced composite materials were of interest. The latter...increasing importance. Some recent theoretical and experimental studies of the behavior of composite - material structures subjected to severe static...dynamic, and/or impact conditions are noted. Such topics as crashworthiness testing ot composite fuselage structures, the impact resistance of graphite and

Linking composition of extracellular polymeric substances (EPS) to the physical structure and hydraulic resistance of membrane biofilms.

PubMed

Desmond, Peter; Best, James P; Morgenroth, Eberhard; Derlon, Nicolas

2018-04-01

The effect of extracellular polymeric substances (EPS) on the meso-scale physical structure and hydraulic resistance of membrane biofilms during gravity driven membrane (GDM) filtration was investigated. Biofilms were developed on the surface of ultrafiltration membranes during dead-end filtration at ultra-low pressure (70 mbar). Biofilm EPS composition (total protein, polysaccharide and eDNA) was manipulated by growing biofilms under contrasting nutrient conditions. Nutrient conditions consisted of (i) a nutrient enriched condition with a nutrient ratio of 100:30:10 (C: N: P), (ii) a phosphorus limitation (C: N: P ratio: 100:30:0), and (iii) a nitrogen limitation (C: N: P ratio: 100:0:10). The structure of the biofilm was characterised at meso-scale using Optical Coherence Tomography (OCT). Biofilm composition was analysed with respect to total organic carbon, total cellular mass and extracellular concentrations of proteins, polysaccharides, and eDNA. 2D-confocal Raman mapping was used to characterise the functional group composition and micro-scale distribution of the biofilms EPS. Our study reveals that the composition of the EPS matrix can determine the meso-scale physical structure of membrane biofilms and in turn its hydraulic resistance. Biofilms grown under P limiting conditions were characterised by dense and homogeneous physical structures with high concentrations of polysaccharides and eDNA. Biofilm grown under nutrient enriched or N limiting conditions were characterised by heterogeneous physical structures with lower concentrations of polysaccharides and eDNA. For P limiting biofilms, 2D-confocal Raman microscopy revealed a homogeneous spatial distribution of anionic functional groups in homogeneous biofilm structures with higher polysaccharide and eDNA concentrations. This study links EPS composition, physical structure and hydraulic resistance of membrane biofilms, with practical relevance for the hydraulic performances of GDM ultrafiltration. Copyright © 2018 Elsevier Ltd. All rights reserved.

Carbon Nanotube Coatings as Used in Strain Sensors for Composite Tanks

NASA Technical Reports Server (NTRS)

Trigwell, Steve; Snyder, Sarah; Hatfield, Walt; Dervishi, Enkeleda; Biris, Alexandru S.

2011-01-01

The next generation of cryogenic fuel tanks, crew habitats and other components for future spacecraft will focus on the usc of lightweight carbon fiber composite materials. A critical issue in the design and optimization of such tanks and structures will bc in structural health monitoring, however, current strain sensors have limitations. In this study, a novel carbon nanotube thin film was applied to carbon fiber composites for structural monitoring. Applying a load using a 3-point bend test to simulate bowing of a tank wall, induced significant increases in the film's electrical resistance at small deflections. Upon release of the load, the resistance returned to its approximate start value and was reproducible over multiple tests. The results show that a carbon nanotube thin film has great potential for the health monitoring of composite structures.

An engineering approach for the application of textile composites to a structural component

NASA Technical Reports Server (NTRS)

Baldwin, Jack W.; Gracias, Brian K.; Clark, Steven R.

1993-01-01

An engineering approach for the application of textile composites to a structural component is addressed. The main objective is to improve impact resistance of composite blades by using some form of 3-D reinforcement. Project goals, results, and conclusions are discussed.

Coexistence of Heavy Metal and Antibiotic Resistance within a Novel Composite Staphylococcal Cassette Chromosome in a Staphylococcus haemolyticus Isolate from Bovine Mastitis Milk

PubMed Central

Xue, Huping; Wu, Zhaowei; Li, Longping; Li, Fan; Wang, Yiqing

2015-01-01

The structure of a composite staphylococcal cassette chromosome (SCC) carried by a methicillin-resistant Staphylococcus haemolyticus (NW19A) isolated from a bovine milk sample was analyzed. The formation of the circular forms of both single SCC elements and composite SCC elements was detected in NW19A. Twenty heavy metal and antibiotic resistance-related genes coexisted in this composite SCC, suggesting that these genes might be coselected under environmental pressure. The mec gene complex in NW19A, designated type C3, is different from classic C1 or C2 gene complexes structurally and likely evolves differently. Furthermore, results from alignment of the SCC composite island of NW19A with 50 related sequences from different staphylococcal strains provided additional evidence to support the notion that coagulase-negative staphylococci (CoNS) are the original host of heavy metal resistance genes among staphylococci. Given that a SCC composite island could transfer freely among different staphylococcal species from different hosts, more attention should be paid to contamination with heavy metals and antibiotics in dairy farming environments, including wastewater, soil, feces, and feed. PMID:26169408

Coexistence of heavy metal and antibiotic resistance within a novel composite staphylococcal cassette chromosome in a Staphylococcus haemolyticus isolate from bovine mastitis milk.

PubMed

Xue, Huping; Wu, Zhaowei; Li, Longping; Li, Fan; Wang, Yiqing; Zhao, Xin

2015-09-01

The structure of a composite staphylococcal cassette chromosome (SCC) carried by a methicillin-resistant Staphylococcus haemolyticus (NW19A) isolated from a bovine milk sample was analyzed. The formation of the circular forms of both single SCC elements and composite SCC elements was detected in NW19A. Twenty heavy metal and antibiotic resistance-related genes coexisted in this composite SCC, suggesting that these genes might be coselected under environmental pressure. The mec gene complex in NW19A, designated type C3, is different from classic C1 or C2 gene complexes structurally and likely evolves differently. Furthermore, results from alignment of the SCC composite island of NW19A with 50 related sequences from different staphylococcal strains provided additional evidence to support the notion that coagulase-negative staphylococci (CoNS) are the original host of heavy metal resistance genes among staphylococci. Given that a SCC composite island could transfer freely among different staphylococcal species from different hosts, more attention should be paid to contamination with heavy metals and antibiotics in dairy farming environments, including wastewater, soil, feces, and feed. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Toughened and corrosion- and wear-resistant composite structures and fabrication methods thereof

DOEpatents

Seals, Roland D.; Ripley, Edward B.; Hallman, Russell L.

2017-06-20

Composite structures having a reinforced material interjoined with a substrate, wherein the reinforced material comprises a compound selected from the group consisting of titanium monoboride, titanium diboride, and combinations thereof.

Intrinsic Topological Insulator Bi1.5Sb0.5Te3-xSex Thin Crystals

NASA Astrophysics Data System (ADS)

Wang, Wei; Li, Li; Zou, Wenqin; He, Liang; Song, Fengqi; Zhang, Rong; Wu, Xiaoshan; Zhang, Fengming

2015-01-01

The quaternary topological insulator (Bi,Sb)2(Te,Se)3 has demonstrated topological surface states with an insulating bulk. Scientists have identified an optimized composition of Bi1.5Sb0.5Te1.7Se1.3 with the highest resistivity reported. But the physics that drive to this composition remains unclear. Here we report the crystal structure and the magneto-transport properties of Bi1.5Sb0.5Te3-xSex (BSTS) series. A correlation between the structure and the physical properties has been revealed. We found out that within the rhombohedral structure, the composition with most Te substituting Se has the highest resistivity. On the other hand, segregation of other composition phases will introduce much higher bulk concentration.

Materials, Manufacturing and Test Development of a Composite Fan Blade Leading Edge Subcomponent for Improved Impact Resistance

NASA Technical Reports Server (NTRS)

Handschuh, Katherine M.; Miller, Sandi G.; Sinnott, Matthew J.; Kohlman, Lee W.; Roberts, Gary D.; Pereira, J. Michael; Ruggeri, Charles R.

2014-01-01

Application of polymer matrix composite materials for jet engine fan blades is becoming attractive as an alternative to metallic blades; particularly for large engines where significant weight savings are recognized on moving to a composite structure. However, the weight benefit of the composite of is offset by a reduction of aerodynamic efficiency resulting from a necessary increase in blade thickness; relative to the titanium blades. Blade dimensions are largely driven by resistance to damage on bird strike. Further development of the composite material is necessary to allow composite blade designs to approximate the dimensions of a metallic fan blade. The reduction in thickness over the state of the art composite blades is expected to translate into structural weight reduction, improved aerodynamic efficiency, and therefore reduced fuel consumption. This paper presents test article design, subcomponent blade leading edge fabrication, test method development, and initial results from ballistic impact of a gelatin projectile on the leading edge of composite fan blades. The simplified test article geometry was developed to realistically simulate a blade leading edge while decreasing fabrication complexity. Impact data is presented on baseline composite blades and toughened blades; where a considerable improvement to impact resistance was recorded.

Materials, Manufacturing, and Test Development of a Composite Fan Blade Leading Edge Subcomponent for Improved Impact Resistance

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Handschuh, Katherine; Sinnott, Matthew J.; Kohlman, Lee W.; Roberts, Gary D.; Martin, Richard E.; Ruggeri, Charles R.; Pereira, J. Michael

2015-01-01

Application of polymer matrix composite materials for jet engine fan blades is becoming attractive as an alternative to metallic blades; particularly for large engines where significant weight savings are recognized on moving to a composite structure. However, the weight benefit of the composite is offset by a reduction of aerodynamic efficiency resulting from a necessary increase in blade thickness; relative to the titanium blades. Blade dimensions are largely driven by resistance to damage on bird strike. Further development of the composite material is necessary to allow composite blade designs to approximate the dimensions of a metallic fan blade. The reduction in thickness over the state of the art composite blades is expected to translate into structural weight reduction, improved aerodynamic efficiency, and therefore reduced fuel consumption. This paper presents test article design, subcomponent blade leading edge fabrication, test method development, and initial results from ballistic impact of a gelatin projectile on the leading edge of composite fan blades. The simplified test article geometry was developed to realistically simulate a blade leading edge while decreasing fabrication complexity. Impact data is presented on baseline composite blades and toughened blades; where a considerable improvement to impact resistance was recorded.

Composite membrane with integral rim

DOEpatents

Routkevitch, Dmitri; Polyakov, Oleg G

2015-01-27

Composite membranes that are adapted for separation, purification, filtration, analysis, reaction and sensing. The composite membranes can include a porous support structure having elongate pore channels extending through the support structure. The composite membrane also includes an active layer comprising an active layer material, where the active layer material is completely disposed within the pore channels between the surfaces of the support structure. The active layer is intimately integrated within the support structure, thus enabling great robustness, reliability, resistance to mechanical stress and thermal cycling, and high selectivity. Methods for the fabrication of composite membranes are also provided.

Feasibility of SiC composite structures for 1644 deg gas turbine seal applications

NASA Technical Reports Server (NTRS)

Darolia, R.

1979-01-01

The feasibility of silicon carbide composite structures was evaluated for 1644 K gas turbine seal applications. The silicon carbide composites evaluated consisted of Si/SiC Silcomp (Trademark) - and sintered silicon carbide as substrates, both with attached surface layers containing BN as an additive. A total of twenty-eight candidates with variations in substrate type and density, and layer chemistry, density, microstructure, and thickness were evaluated for abradability, cold particle erosion resistance, static oxidation resistance, ballistic impact resistance, and fabricability. The BN-free layers with variations in density and pore size were later added for evaluation. The most promising candidates were evaluated for Mach 1.0 gas oxidation/erosion resistance from 1477 K to 1644 K. The as-fabricated rub layers did not perform satisfactorily in the gas oxidation/erosion tests. However, preoxidation was found to be beneficial in improving the hot gas erosion resistance. Overall, the laboratory and rig test evaluations show that material properties are suitable for 1477 K gas turbine seal applications.

Thermoplastic composite matrices with improved solvent resistance

NASA Technical Reports Server (NTRS)

Hergenrother, P. M.; Jensen, B. J.; Havens, S. J.

1984-01-01

In order to improve solvent resistance of aromatic thermoplastic polymers, ethynyl-terminated aromatic sulfone polymers (ETS), sulfone/ester polymers (SEPE) containing pendent ethynyl groups, and phenoxy resin containing pendent ethynyl groups are synthesized. Cured polysulfones and phenoxy resins containing ethynyl groups on the ends or pendent on the molecules exhibited systematic behavior in solvent resistance, film flexibility, and toughness as a function of crosslink density. The film and composite properties of a cured solvent-resistant ETS were better than those of a commercially available solvent sensitive polysulfone. The study was part of a NASA program to better understand the trade-offs between solvent resistance, processability and mechanical properties which may be useful in designing composite structures for aerospace vehicles.

An All-Organic Composite System for Resistive Change Memory via the Self-Assembly of Plastic-Crystalline Molecules.

PubMed

Cha, An-Na; Lee, Sang-A; Bae, Sukang; Lee, Sang Hyun; Lee, Dong Su; Wang, Gunuk; Kim, Tae-Wook

2017-01-25

An all-organic composite system was introduced as an active component for organic resistive memory applications. The active layer was prepared by mixing a highly polar plastic-crystalline organic molecule (succinonitrile, SN) into an insulating polymer (poly(methyl methacrylate), PMMA). As increasing concentrations of SN from 0 to 3.0 wt % were added to solutions of different concentrations of PMMA, we observed distinguishable microscopic surface structures on blended films of SN and PMMA at certain concentrations after the spin-casting process. The structures were organic dormant volcanos composed of micron-scale PMMA craters and disk type SN lava. Atomic force microscopy (AFM), cross-sectional transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometer (EDX) analysis showed that these structures were located in the middle of the film. Self-assembly of the plastic-crystalline molecules resulted in the phase separation of the SN:PMMA mixture during solvent evaporation. The organic craters remained at the surface after the spin-casting process, indicative of the formation of an all-organic composite film. Because one organic crater contains one SN disk, our system has a coplanar monolayer disk composite system, indicative of the simplest composite type of organic memory system. Current-voltage (I-V) characteristics of the composite films with organic craters revealed that our all-organic composite system showed unipolar type resistive switching behavior. From logarithmic I-V characteristics, we found that the current flow was governed by space charge limited current (SCLC). From these results, we believe that a plastic-crystalline molecule-polymer composite system is one of the most reliable ways to develop organic composite systems as potential candidates for the active components of organic resistive memory applications.

Highly sensitive piezo-resistive graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone composites with improved conductive network construction.

PubMed

Zhao, Hang; Bai, Jinbo

2015-05-13

The constructions of internal conductive network are dependent on microstructures of conductive fillers, determining various electrical performances of composites. Here, we present the advanced graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone (GCHs/PDMS) composites with high piezo-resistive performance. GCH particles were synthesized by the catalyst chemical vapor deposition approach. The synthesized GCHs can be well dispersed in the matrix through the mechanical blending process. Due to the exfoliated GNP and aligned CNTs coupling structure, the flexible composite shows an ultralow percolation threshold (0.64 vol %) and high piezo-resistive sensitivity (gauge factor ∼ 10(3) and pressure sensitivity ∼ 0.6 kPa(-1)). Slight motions of finger can be detected and distinguished accurately using the composite film as a typical wearable sensor. These results indicate that designing the internal conductive network could be a reasonable strategy to improve the piezo-resistive performance of composites.

Selection criteria for wear resistant powder coatings under extreme erosive wear conditions

NASA Astrophysics Data System (ADS)

Kulu, P.; Pihl, T.

2002-12-01

Wear-resistant thermal spray coatings for sliding wear are hard but brittle (such as carbide and oxide based coatings), which makes them useless under impact loading conditions and sensitive to fatigue. Under extreme conditions of erosive wear (impact loading, high hardness of abrasives, and high velocity of abradant particles), composite coatings ensure optimal properties of hardness and toughness. The article describes tungsten carbide-cobalt (WC-Co) systems and self-fluxing alloys, containing tungsten carbide based hardmetal particles [NiCrSiB-(WC-Co)] deposited by the detonation gun, continuous detonation spraying, and spray fusion processes. Different powder compositions and processes were studied, and the effect of the coating structure and wear parameters on the wear resistance of coatings are evaluated. The dependence of the wear resistance of sprayed and fused coatings on their hardness is discussed, and hardness criteria for coating selection are proposed. The so-called “double cemented” structure of WC-Co based hardmetal or metal matrix composite coatings, as compared with a simple cobalt matrix containing particles of WC, was found optimal. Structural criteria for coating selection are provided. To assist the end user in selecting an optimal deposition method and materials, coating selection diagrams of wear resistance versus hardness are given. This paper also discusses the cost-effectiveness of coatings in the application areas that are more sensitive to cost, and composite coatings based on recycled materials are offered.

Thermal characteristics of carbon fiber reinforced epoxy containing multi-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Lee, Jin-woo; Park, Soo-Jeong; Kim, Yun-hae; Riichi-Murakami

2018-06-01

The material with irregular atomic structures such as polymer material exhibits low thermal conductivity because of the complex structural properties. Even materials with same atomic configurations, thermal conductivity may be different based on their structural properties. It is expected that nanoparticles with conductivity will change non-conductive polymer base materials to electrical conductors, and improve the thermal conductivity even with extremely small filling amount. Nano-composite materials contain nanoparticles with a higher surface ratio which makes the higher interface percentage to the total surface of nanoparticles. Therefore, thermal resistance of the interface becomes a dominating factor determines the effective thermal conductivity in nano-composite materials. Carbon fiber has characteristic of resistance or magnetic induction and Also, Carbon nanotube (CNT) has electronic and thermal property. It can be applied for heating system. These characteristic are used as heating composite. In this research, the exothermic characteristics of Carbon fiber reinforced composite added CNT were evaluated depend on CNT length and particle size. It was found that the CNT dispersed in the resin reduces the resistance between the interfaces due to the decrease in the total resistance of the heating element due to the addition of CNTs. It is expected to improve the life and performance of the carbon fiber composite material as a result of the heating element resulting from this paper.

Computational simulation of acoustic fatigue for hot composite structures

NASA Technical Reports Server (NTRS)

Singhal, S. N.; Nagpal, V. K.; Murthy, P. L. N.; Chamis, C. C.

1991-01-01

This paper presents predictive methods/codes for computational simulation of acoustic fatigue resistance of hot composite structures subjected to acoustic excitation emanating from an adjacent vibrating component. Select codes developed over the past two decades at the NASA Lewis Research Center are used. The codes include computation of (1) acoustic noise generated from a vibrating component, (2) degradation in material properties of the composite laminate at use temperature, (3) dynamic response of acoustically excited hot multilayered composite structure, (4) degradation in the first-ply strength of the excited structure due to acoustic loading, and (5) acoustic fatigue resistance of the excited structure, including propulsion environment. Effects of the laminate lay-up and environment on the acoustic fatigue life are evaluated. The results show that, by keeping the angled plies on the outer surface of the laminate, a substantial increase in the acoustic fatigue life is obtained. The effect of environment (temperature and moisure) is to relieve the residual stresses leading to an increase in the acoustic fatigue life of the excited panel.

Computational simulation of acoustic fatigue for hot composite structures

NASA Technical Reports Server (NTRS)

Singhal, Surendra N.; Murthy, Pappu L. N.; Chamis, Christos C.; Nagpal, Vinod K.; Sutjahjo, Edhi

1991-01-01

Predictive methods/computer codes for the computational simulation of acoustic fatigue resistance of hot composite structures subjected to acoustic excitation emanating from an adjacent vibrating component are discussed. Select codes developed over the past two decades at the NASA Lewis Research Center are used. The codes include computation of acoustic noise generated from a vibrating component, degradation in material properties of a composite laminate at use temperature, dynamic response of acoustically excited hot multilayered composite structure, degradation in the first ply strength of the excited structure due to acoustic loading, and acoustic fatigue resistance of the excited structure, including the propulsion environment. Effects of the laminate lay-up and environment on the acoustic fatigue life are evaluated. The results show that, by keeping the angled plies on the outer surface of the laminate, a substantial increase in the acoustic fatigue life is obtained. The effect of environment (temperature and moisture) is to relieve the residual stresses leading to an increase in the acoustic fatigue life of the excited panel.

Composite membranes and methods for making same

DOEpatents

Routkevitch, Dmitri; Polyakov, Oleg G

2012-07-03

Composite membranes that are adapted for separation, purification, filtration, analysis, reaction and sensing. The composite membranes can include a porous support structure having elongate pore channels extending through the support structure. The composite membrane also includes an active layer comprising an active layer material, where the active layer material is completely disposed within the pore channels between the surfaces of the support structure. The active layer is intimately integrated within the support structure, thus enabling great robustness, reliability, resistance to mechanical stress and thermal cycling, and high selectivity. Methods for the fabrication of composite membranes are also provided.

Neonatal lungs--can absolute lung resistivity be determined non-invasively?

PubMed

Brown, B H; Primhak, R A; Smallwood, R H; Milnes, P; Narracott, A J; Jackson, M J

2002-07-01

The electrical resistivity of lung tissue can be related to the structure and composition of the tissue and also to the air content. Conditions such as pulmonary oedema and emphysema have been shown to change lung resistivity. However, direct access to the lungs to enable resistivity to be measured is very difficult. We have developed a new method of using electrical impedance tomographic (EIT) measurements on a group of 142 normal neonates to determine the absolute resistivity of lung tissue. The methodology involves comparing the measured EIT data with that from a finite difference model of the thorax in which lung tissue resistivity can be changed. A mean value of 5.7 +/- 1.7 omega(m) was found over the frequency range 4 kHz to 813 kHz. This value is lower than that usually given for adult lung tissue but consistent with the literature on the composition of the neonatal lung and with structural modelling.

Lithographically defined microporous carbon-composite structures

DOEpatents

Burckel, David Bruce; Washburn, Cody M.; Lambert, Timothy N.; Finnegan, Patrick Sean; Wheeler, David R.

2016-12-06

A microporous carbon scaffold is produced by lithographically patterning a carbon-containing photoresist, followed by pyrolysis of the developed resist structure. Prior to exposure, the photoresist is loaded with a nanoparticulate material. After pyrolysis, the nanonparticulate material is dispersed in, and intimately mixed with, the carbonaceous material of the scaffold, thereby yielding a carbon composite structure.

Investigation of heat-resistant layered coating of Al-Cr-Ni

NASA Astrophysics Data System (ADS)

Shmorgun, V. G.; Trykov, Y. P.; Bogdanov, A. I.; Taube, A. O.

2016-02-01

The paper shows the transformation of the structure and phase composition of the layered coating system Al-Cr-Ni, obtained by the heat treatment of multilayered composite H20N80+AD1, welded by explosion, in the time range 1-300 hours. The cyclic heat resistance of the coating at 1150 ° C is studied.

Laboratory tests on fungal resistance of wood filled polyethylene composites

Treesearch

Craig M. Clemons; Rebecca E. Ibach

2002-01-01

A standard method for determining the durability of structural wood was modified for testing the fungal resistance of composites made from high density polyethylene filled with 50% wood flour. Moisture content, mechanical properties, and weight loss were measured over 12 weeks exposure to brown-and white-rot fungi. Mechanical properties were decreased, but irreversible...

Impact resistance of fiber composite blades used in aircraft turbine engines

NASA Technical Reports Server (NTRS)

Friedrich, L. A.; Preston, J. L., Jr.

1973-01-01

Resistance of advanced fiber reinforced epoxy matrix composite materials to ballistic impact was investigated as a function of impacting projectile characteristics, and composite material properties. Ballistic impact damage due to normal impacts, was classified as transverse (stress wave delamination and splitting), penetrative, or structural (gross failure). Steel projectiles were found to be gelatin ice projectiles in causing penetrative damage leading to reduced tensile strength. Gelatin and ice projectiles caused either transverse or structural damage, depending upon projectile mass and velocity. Improved composite transverse tensile strength, use of dispersed ply lay-ups, and inclusion of PRD-49-1 or S-glass fibers correlated with improved resistance of composite materials to transverse damage. In non-normal impacts against simulated blade shapes, the normal velocity component of the impact was used to correlate damage results with normal impact results. Stiffening the leading edge of simulated blade specimens led to reduced ballistic damage, while addition of a metallic leading edge provided nearly complete protection against 0.64 cm diameter steel, and 1.27 cm diameter ice and gelatin projectiles, and partial protection against 2.54 cm diameter projectiles of ice and gelatin.

MoSi2-Base Structural Composite Passed Engine Test

NASA Technical Reports Server (NTRS)

Nathal, Michael V.; Hebsur, Mohan G.

1999-01-01

The intermetallic compound molybdenum disilicide (MoSi2) is an attractive high-temperature structural material for advanced engine applications. It has excellent oxidation resistance, a high melting point, relatively low density, and high thermal conductivity; and it is easily machined. Past research at the NASA Lewis Research Center has resulted in the development of a hybrid composite consisting of a MoSi2 matrix reinforced with silicon nitride (Si3N4) particulate and silicon carbide (SiC) fibers. This composite has demonstrated attractive strength, toughness, thermal fatigue, and oxidation resistance, including resistance to "pest" oxidation. These properties attracted the interest of the Office of Naval Research and Pratt & Whitney, and a joint NASA/Navy/Pratt & Whitney effort was developed to continue to mature the MoSi2 composite technology. A turbine blade outer air seal, which was part of the Integrated High Performance Turbine Engine Technology (IHPTET) program, was chosen as a first component on which to focus.

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

DTIC Science & Technology

2015-07-01

2008). ............................ 35 Figure 4.1. Proposed composite system by Karimiet al. (2011...strength deterioration when shear capacity was reached. Therefore, strengthening such structures is essential and cannot be neglected. FRP composite ...2007) provide a review of the most significant work related to the use of composite materials to resist blast in buildings. This article includes

Simulation of Impact Phenomena on the Composite Structures Containing Ceramic Plates and High Entropy Alloys

NASA Astrophysics Data System (ADS)

Geantă, V.; Cherecheș, T.; Lixandru, P.; Voiculescu, I.; Ștefănoiu, R.; Dragnea, D.; Zecheru, T.; Matache, L.

2017-06-01

Due to excellent mechanical properties, high entropy alloys from the system AlxCrFeCoNi can be used successfully to create composite structures containing both metallic and ceramic plates, which resists at dynamic load during high speeds impact (like projectiles, explosion). The paper presents four different composite structures made from a combination of metallic materials and ceramics plates: duralumin-ceramics, duralumin-ceramics-HEA, HEA-ceramics-HEA, HEA-ceramics-duralumin. Numerical simulation of impact behavior of the composite structures was performed by virtual methods, taking into account the mechanical properties of both materials. The best results were obtained using composite structures HEA-ceramics-HEA, HEA-ceramics-duralumin.

Integrated analysis of engine structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1981-01-01

The need for light, durable, fuel efficient, cost effective aircraft requires the development of engine structures which are flexible, made from advaced materials (including composites), resist higher temperatures, maintain tighter clearances and have lower maintenance costs. The formal quantification of any or several of these requires integrated computer programs (multilevel and/or interdisciplinary analysis programs interconnected) for engine structural analysis/design. Several integrated analysis computer prorams are under development at Lewis Reseach Center. These programs include: (1) COBSTRAN-Composite Blade Structural Analysis, (2) CODSTRAN-Composite Durability Structural Analysis, (3) CISTRAN-Composite Impact Structural Analysis, (4) STAEBL-StruTailoring of Engine Blades, and (5) ESMOSS-Engine Structures Modeling Software System. Three other related programs, developed under Lewis sponsorship, are described.

Polyimide composites: Application histories

NASA Technical Reports Server (NTRS)

Poveromo, L. M.

1985-01-01

Advanced composite hardware exposed to thermal environments above 127 C (260 F) must be fabricated from materials having resin matrices whose thermal/moisture resistance is superior to that of conventional epoxy-matrix systems. A family of polyimide resins has evolved in the last 10 years that exhibits the thermal-oxidative stability required for high-temperature technology applications. The weight and structural benefits for organic-matrix composites can now be extended by designers and materials engineers to include structures exposed to 316 F (600 F). Polyimide composite materials are now commercially available that can replace metallic or epoxy composite structures in a wide range of aerospace applications.

Geopolymer Porous Nanoceramics for Structural Smart and Thermal Shock Resistant Applications

DTIC Science & Technology

2011-02-02

porous membranes and foams, ceramic armor composites , iron-based geopolymer analogues, geopolymer composites reinforced with chopped polypropylene... geopolymers and geopolymer composites , as fabricated and upon conversion to ceramics with heating. The microstucture consisted of nanoporous...ceramic armore composites , iron-based geopolymer analogues, geopolymer composites reinforced with chopped polypropylene or basalt fibers and

Tough composite materials: Recent developments

NASA Technical Reports Server (NTRS)

Vosteen, L. F. (Editor); Johnston, N. J. (Editor); Teichman, L. A. (Editor); Blankenship, C. P. (Editor)

1985-01-01

The present volume broadly considers topics in composite fracture toughness and impact behavior characterization, composite system constituent properties and their interrelationships, and matrix systems' synthesis and characterization. Attention is given to the characterization of interlaminar crack growth in composites by means of the double cantilever beam specimen, the characterization of delamination resistance in toughened resin composites, the effect of impact damage and open holes on the compressive strength of tough resin/high strain fiber laminates, the effect of matrix and fiber properties on compression failure mechanisms and impact resistance, the relation of toughened neat resin properties to advanced composite mechanical properties, and constituent and composite properties' relationships in thermosetting matrices. Also treated are the effect of cross-link density on the toughening mechanism of elastomer-modified epoxies, the chemistry of fiber/resin interfaces, novel carbon fibers and their properties, the development of a heterogeneous laminating resin, solvent-resistant thermoplastics, NASA Lewis research in advanced composites, and opportunities for the application of composites in commercial aircraft transport structures.

Design of a new bottom antireflective coating composition for KrF resist

NASA Astrophysics Data System (ADS)

Mizutani, Kazuyoshi; Momota, Makoto; Aoai, Toshiaki; Yagihara, Morio

1999-06-01

A study for a new organic bottom antireflective coating (BARC) composition is described. A structural design of a light-absorbing dye was most important because dye structure not only plays a role in eliminating reflection from a substrate but also shows influence on dry etch rate of BARC material to a considerable extent. For example, an anthracene moiety with large absorption at 248 nm had undesirable dry etch resistance. 3-Hydroxy-2-naphthoic acid moiety was found to be one of suitable dyes for KrF BARC compositions, and the polymer bearing the dye showed enough absorbance and good erodability in dry etch. The BARC polymer was eroded as one and a half times faster than a novolak resin, and a little faster than an anthracene incorporated polymer. The result was discussed from the concepts of Ohnishi parameter and the ring parameter for dry etch durability of resist materials. BARC polymer should be thermoset by hard bake to eliminate intermixing with resist compositions. The BARC polymer bearing hydroxy group which is useful for a crosslinking reaction was thermoset in the presence of melamine-formaldehyde crosslinker and an acid catalyst after baking over 200 degrees C.

Resistance heating releases structural adhesive

NASA Technical Reports Server (NTRS)

Glemser, N. N.

1967-01-01

Composite adhesive package bonds components together for testing and enables separation when testing is completed. The composite of adhesives, insulation and a heating element separate easily when an electrical current is applied.

High-Strength Hybrid Textile Composites with Carbon, Kevlar, and E-Glass Fibers for Impact-Resistant Structures. A Review.

NASA Astrophysics Data System (ADS)

Priyanka, P.; Dixit, A.; Mali, H. S.

2017-11-01

The paper reviews the characterization of high-performance hybrid textile composites and their hybridization effects of composite's behavior. Considered are research works based on the finite-element modeling, simulation, and experimental characterization of various mechanical properties of such composites.

Improvements in Microstructure and Wear Resistance of Plasma-Sprayed Fe-Based Amorphous Coating by Laser-Remelting

NASA Astrophysics Data System (ADS)

Jiang, Chaoping; Chen, Hong; Wang, Gui; Chen, Yongnan; Xing, Yazhe; Zhang, Chunhua; Dargusch, Matthew

2017-04-01

Amorphous coating technology is an attractive way of taking advantage of the superior properties of amorphous alloys for structural applications. However, the limited bonds between splats within the plasma-sprayed coatings result in a typically lamellar and porous coating structure. To overcome these limitations, the as-sprayed coating was treated by a laser-remelting process. The microstructure and phase composition of two coatings were analyzed using scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, and x-ray diffraction. The wear resistance of the plasma-sprayed coating and laser-remelted coating was studied comparatively using a pin-on-disc wear test under dry friction conditions. It was revealed that the laser-remelted coating exhibited better wear resistance because of its defect-free and amorphous-nanocrystalline composited structure.

a Study of Composite Coatings on 22MnCrNiMo Steel for Mooring Chain

NASA Astrophysics Data System (ADS)

Shen, Yan; Sahoo, Prasanta K.; Pan, Yipeng

In order to enhance the corrosion resistance of mooring chain, the composite coatings are carried out on the surface of 22MnCrNiMo steel for mooring chain by double-pulsed electrodeposition technology using centrifugal force in the rotating device. The microstructure and anti-corrosion performance of the composite coatings have been investigated experimentally. This paper mainly focuses on the experimental work to determine the structural characteristics and corrosion resistance of composite coatings in the presence of nano-SiC. The results show that the presence of nano-SiC has a significant effect on the preparation of composite coating during the process. The surface of the coating becomes compact and smooth at a moderate concentration of nano-SiC particles. Furthermore, the best corrosion resistance of the composite coatings can be obtained when the concentration of nano-SiC particles is 2.0g.L-1 after salt spray treatment.

Resin selection criteria for tough composite structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Smith, G. T.

1983-01-01

Resin selection criteria are derived using a structured methodology consisting of an upward integrated mechanistic theory and its inverse (top-down structured theory). These criteria are expressed in a "criteria selection space" which are used to identify resin bulk properties for improved composite "toughness". The resin selection criteria correlate with a variety of experimental data including laminate strength, elevated temperature effects and impact resistance.

Thermal and Compositional Variation of Glassy Metal Structure Factors.

NASA Astrophysics Data System (ADS)

From, Milton

The x-ray total structure factor of the glassy -metal alloys Mg_{70}Zn_ {30}, Ca_{70}Mg_{30 } and Mg_{85.5}Cu _{14.5} has been measured at three temperatures: 9K, 150K, and 300K. The data have a statistical precision of about.8% and an absolute accuracy of roughly 3%. Percus-Yevick hard sphere structure factors may be fitted quite accurately to the data in the region of the first peak. In addition, the variation of the experimental structure factor with composition is found to be consistent with the Percus-Yevick theory. At low k values, Percus -Yevick and other theoretical model structure factors are in poor agreement with the data. Within experimental error, the temperature dependence of the structure factors is in agreement with the Debye plane wave phonon model of atomic vibrations. The measured structure factors are used to calculate the electrical resistivity from the Faber-Ziman equation. In most cases, the calculations yield both the correct magnitude of resistivity and sign of the temperature coefficient of resistivity.

Electrical Resistance as a NDE Technique to Monitor Processing and Damage Accumulation in SiC/SiC Composites

NASA Technical Reports Server (NTRS)

Smith, Craig; Morscher, Gregory N.; Xia, Zhenhai

2008-01-01

Ceramic matrix composites are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems. The employment of these materials in such applications is limited by the ability to process components reliable and to accurately monitor and predict damage evolution that leads to failure under stressed-oxidation conditions. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. Electrical resistance of SiC/SiC composites is one technique that shows special promise towards this end. Since both the matrix and the fibers are conductive, changes in matrix or fiber properties should relate to changes in electrical conductivity along the length of a specimen or part. Initial efforts to quantify the electrical resistance of different fiber and different matrix SiC/SiC composites will be presented. Also, the effect of matrix cracking on electrical resistivity for several composite systems will be presented. The implications towards electrical resistance as a technique applied to composite processing, damage detection, and life-modeling will be discussed.

Electrical Resistance of SiC/SiC Ceramic Matrix Composites for Damage Detection and Life-Prediction

NASA Technical Reports Server (NTRS)

Smith, Craig; Morscher, Gregory; Xia, Zhenhai

2009-01-01

Ceramic matrix composites (CMC) are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems due to their low density high thermal conductivity. The employment of these materials in such applications is limited by the ability to accurately monitor and predict damage evolution. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. CMC is a multifunctional material in which the damage is coupled with the material s electrical resistance, providing the possibility of real-time information about the damage state through monitoring of resistance. Here, resistance measurement of SiC/SiC composites under mechanical load at both room temperature monotonic and high temperature creep conditions, coupled with a modal acoustic emission technique, can relate the effects of temperature, strain, matrix cracks, fiber breaks, and oxidation to the change in electrical resistance. A multiscale model can in turn be developed for life prediction of in-service composites, based on electrical resistance methods. Results of tensile mechanical testing of SiC/SiC composites at room and high temperatures will be discussed. Data relating electrical resistivity to composite constituent content, fiber architecture, temperature, matrix crack formation, and oxidation will be explained, along with progress in modeling such properties.

Doped SnO₂ transparent conductive multilayer thin films explored by continuous composition spread.

PubMed

Lee, Jin Ju; Ha, Jong-Yoon; Choi, Won-Kook; Cho, Yong Soo; Choi, Ji-Won

2015-04-13

Mn-doped SnO₂ thin films were fabricated by a continuous composition spread (CCS) method on a glass substrate at room temperature to find optimized compositions. The fabricated materials were found to have a lower resistivity than pure SnO₂ thin films because of oxygen vacancies generated by Mn doping. As Mn content was increased, resistivity was found to decrease for limited doping concentrations. The minimum thin film resistivity was 0.29 Ω-cm for a composition of 2.59 wt % Mn-doped SnO₂. The Sn-O vibrational stretching frequency in FT-IR showed a blue shift, consistent with oxygen deficiency. Mn-doped SnO₂/Ag/Mn-doped SnO₂ multilayer structures were fabricated using this optimized composition deposited by an on-axis radio frequency (RF) sputter. The multilayer transparent conducting oxide film had a resistivity of 7.35 × 10⁻⁵ Ω-cm and an average transmittance above 86% in the 550 nm wavelength region.

Geopolymer Porous Nanoceramics for Structural, for Smart and Thermal Shock Resistant Applications

DTIC Science & Technology

2011-02-02

porous membranes and foams, ceramic armor composites , iron-based geopolymer analogues, geopolymer composites reinforced with chopped polypropylene...the microstructure of geopolymers and geopolymer composites , as fabricated and upon conversion to ceramics with heating. The microstructure consisted...porous membranes and foams, ceramic armor composites , iron-based geopolymer analogues, geopolymer composites reinforced with chopped polypropylene or

Tensile and burning properties of clay/phenolic/GF composite and its application

NASA Astrophysics Data System (ADS)

Diharjo, Kuncoro; Armunanto, V. Bram; Kristiawan, S. Adi

2016-03-01

Composite material has been widely used in automotive due to its properties can be improved by combining with reinforcement, like fiber and particle to enhance mechanical properties and burning resistance. This study aims to investigate the tensile and burning properties of hybrid composite combining glass fiber and clay in phenolic resin. The clay was produced from roof tile rejected by tile industries in Sokka, Kebumen, Indonesia. The composite was made using a press mold method for different number of laminates and orientation of woven-roving-glass-fiber/ WRGF (0/90 and ±45), and the total volume fraction of fiber and clay is constant 40%. The specimens were tested using universal testing machine for tensile properties and burning tests apparatus for burning resistance (time to ignite/ TTI and burning rate/ BR). The enhancing of the Clay/Penolic/GF composite can be performed by the increasing of GF laminates, and the composite with 0/90 orientation of WRGF has higher tensile strength and modulus compared to that with ±45 orientation of WRGF. Both composite with 0/90 and ±45 orientation of WRGF have similar burning resistance (TTI and BR) and the composite containing 13 laminates of WR-GF shows the best burning resistance. According to these properties, this composite has good opportunity to be applied as car body panels or other structure in industries due to save weight and high burning resistance.

[Cellular composition of lymphoid nodules in the trachea wall in rats with different resistance to emotional stress in a model of hemorrhagic stroke].

PubMed

Klyueva, L A

2017-01-01

To reveal regularities of changes in cellular composition of lymphoid nodules in the tracheal wall in male Wistar rats resistant and not resistant to emotional stress in a model of hemorrhagic stroke. Lymphoid formations of the tracheal wall (an area near the bifurcation of the organ) were investigated in 98 male Wistar rats using histological methods. Significant changes in the cellular composition of lymphoid nodules were found. The pattern of changes depends on the stress resistance of rats and the period of the experiment. The active cell destruction in lymphoid nodules was noted both in stress resistant and stress susceptible animals. The changes in the structure of lymphoid nodules found in the experimental hemorrhagic stroke suggest a decrease in the local immune resistance, which is most pronounced in rats not resistant to stress, that may contribute to the development of severe inflammatory complications of stroke such as pneumonia.

Properties of Graphene/Shape Memory Thermoplastic Polyurethane Composites Actuating by Various Methods

PubMed Central

Park, Jin Ho; Dao, Trung Dung; Lee, Hyung-il; Jeong, Han Mo; Kim, Byung Kyu

2014-01-01

Shape memory behavior of crystalline shape memory polyurethane (SPU) reinforced with graphene, which utilizes melting temperature as a shape recovery temperature, was examined with various external actuating stimuli such as direct heating, resistive heating, and infrared (IR) heating. Compatibility of graphene with crystalline SPU was adjusted by altering the structure of the hard segment of the SPU, by changing the structure of the graphene, and by changing the preparation method of the graphene/SPU composite. The SPU made of aromatic 4,4′-diphenylmethane diisocyanate (MSPU) exhibited better compatibility with graphene, having an aromatic structure, compared to that made of the aliphatic hexamethylene diisocyanate. The finely dispersed graphene effectively reinforced MSPU, improved shape recovery of MSPU, and served effectively as a filler, triggering shape recovery by resistive or IR heating. Compatibility was enhanced when the graphene was modified with methanol. This improved shape recovery by direct heating, but worsened the conductivity of the composite, and consequently the efficiency of resistive heating for shape recovery also declined. Graphene modified with methanol was more effective than pristine graphene in terms of shape recovery by IR heating. PMID:28788529

The interaction of hydrogen with metal alloys

NASA Technical Reports Server (NTRS)

Danford, M. D.; Montano, J. W.

1991-01-01

Hydrogen diffusion coefficients were measured for several alloys, and these were determined to be about the same at 25 C for all alloys investigated. The relation of structure, both metallurgical and crystallographic, to the observed hydrogen distribution on charging was investigated, as well as the role of hydride formation in the hydrogen resistance of metal alloys. An attempt was made to correlate the structures and compositions of metal alloys as well as other parameters with the ratios of their notched tensile strengths in hydrogen to that in helium, R(H2/He), which are believed to represent a measure of their hydrogen resistance. Evidence supports the belief that hydrogen permeability and hydrogen resistance are increased by smaller grain sizes for a given alloy composition.

Free vibration of composite re-bars in reinforced structures

NASA Astrophysics Data System (ADS)

Kadioglu, Fethi

2005-11-01

The effect of composite rebar's shape in reinforced concrete beam-type structures on the natural frequencies and modes shapes is investigated through finite element analysis in this paper. Steel rebars are being replaced with composite rebars due to their better ability to resist corrosion in reinforced concrete structures for many infrastructure applications. A variety of composite rebar shapes can be obtained through the pultrusion process. It will be interesting to investigate their shape on free vibration characteristics. The results of natural frequencies and mode shapes are presented and compared for the different composite rebar shapes. The effects of various boundary conditions for different rebar shapes are also investigated.

Carbon fiber polymer-matrix structural composites tailored for multifunctionality by filler incorporation

NASA Astrophysics Data System (ADS)

Han, Seungjin

This dissertation provides multifunctional carbon fiber polymer-matrix structural composites for vibration damping, thermal conduction and thermoelectricity. Specifically, (i) it has strengthened and stiffened carbon fiber polymer-matrix structural composites by the incorporation of halloysite nanotubes, carbon nanotubes and silicon carbide whiskers, (ii) it has improved mechanical energy dissipation using carbon fiber polymer-matrix structural composites with filler incorporation, (iii) it has increased the through-thickness thermal conductivity of carbon fiber polymer-matrix composite by curing pressure increase and filler incorporation, and (iv) it has enhanced the thermoelectric behavior of carbon fiber polymer-matrix structural composites. Low-cost natural halloysite nanotubes (0.1 microm diameter) were effective for strengthening and stiffening continuous fiber polymer-matrix composites, as shown for crossply carbon fiber (5 microm diameter, ˜59 vol.%) epoxy-matrix composites under flexure, giving 17% increase in strength, 11% increase in modulus and 21% decrease in ductility. They were less effective than expensive multiwalled carbon nanotubes (0.02 microm diameter), which gave 25% increase in strength, 11% increase in modulus and 14% decrease in ductility. However, they were more effective than expensive silicon carbide whiskers (1 microm diameter), which gave 15% increase in strength, 9% increase in modulus and 20% decrease in ductility. Each filler, at ˜2 vol.%, was incorporated in the composite at every interlaminar interface by fiber prepreg surface modification. The flexural strength increase due to halloysite nanotubes incorporation related to the interlaminar shear strength increase. The measured values of the composite modulus agreed roughly with the calculated values based on the Rule of Mixtures. Continuous carbon fiber composites with enhanced vibration damping under flexure are provided by incorporation of fillers between the laminae. Exfoliated graphite (EG) as a sole filler is more effective than carbon nanotube (SWCNT/MWCNT), halloysite nanotube (HNT) or nanoclay as sole fillers in enhancing the loss tangent, if the curing pressure is 2.0 (not 0.5) MPa. The MWCNT, SiC whisker and halloysite nanotube as sole fillers are effective for increasing the storage modulus. The combined use of a storage-modulus-enhancing filler (CNT, SiC whisker or HNT) and a loss-tangent-enhancing filler (EG or nanoclay) gives the best performance. With EG, HNT and 2.0-MPa curing, the loss modulus is increased by 110%, while the flexural strength is decreased by 14% and the flexural modulus is not affected. With nanoclay, HNT and 0.5-MPa curing, the loss modulus is increased by 96%, while the flexural strength and modulus are essentially not affected. The low through-thickness thermal conductivity limits heat dissipation from continuous carbon fiber polymer-matrix composites. This conductivity is increased by up to 60% by raising the curing pressure from 0.1 to 2.0 MPa and up to 33% by incorporation of a filler (61.5 vol.%) at the interlaminar interface. The thermal resistivity is dominated by the lamina resistivity (which is contributed substantially by the intralaminar fiber--fiber interfacial resistivity), with the interlaminar interface thermal resistivity being unexpectedly negligible. The lamina resistivity and intralaminar fiber-fiber interfacial resistivity are decreased by up to 56% by raising the curing pressure and up to 36% by filler incorporation. Thermoelectric structural materials are potentially attractive for large-scale energy harvesting. Through filler incorporation and unprecedented decoupling of the bulk (laminae) and interfacial (interlaminar interfaces) contributions to the Seebeck voltage (through-thickness Seebeck voltage of a crossply continuous carbon fiber/epoxy composite laminate), this work provides thermoelectric power magnitudes at ˜70°C up to 110, 1670 and 11000 microV/K for the laminate, a lamina and an interlaminar interface respectively. The interface provides an apparent thermoelectric effect due to carrier backflow. The interfacial voltage is opposite in sign from the laminate and lamina voltages and is slightly lower in magnitude than the lamina voltage. The through-thickness thermoelectric behavior of continuous carbon fiber epoxy-matrix structural composites has been greatly improved by the use of tellurium particles (13 vol.% of composite), bismuth telluride particles (2 vol.%) and carbon black (2 vol.%) at the interlaminar interface. The thermoelectric power is increased from 8 to 163 microV/K, while the electrical resistivity is decreased from 0.17 to 0.02 O.cm, the thermal conductivity is decreased from 1.31 to 0.51 W/m.K, and the dimensionless thermoelectric figure of merit ZT at 70°C is increased from 9 x 10-6 to 9 x 10-2. Decrease in the curing pressure from 4.0 to 0.5 MPa decreases ZT slightly, mainly due to the increase in electrical resistivity.

Amorphous metal formulations and structured coatings for corrosion and wear resistance

DOEpatents

Farmer, Joseph C.

2014-07-15

A system for coating a surface comprising providing a source of amorphous metal that contains more than 11 elements and applying the amorphous metal that contains more than 11 elements to the surface by a spray. Also a coating comprising a composite material made of amorphous metal that contains more than 11 elements. An apparatus for producing a corrosion-resistant amorphous-metal coating on a structure comprises a deposition chamber, a deposition source in the deposition chamber that produces a deposition spray, the deposition source containing a composite material made of amorphous metal that contains more than 11 elements, and a system that directs the deposition spray onto the structure.

Amorphous metal formulations and structured coatings for corrosion and wear resistance

DOEpatents

Farmer, Joseph C [Tracy, CA

2011-12-13

A system for coating a surface comprising providing a source of amorphous metal that contains more than 11 elements and applying the amorphous metal that contains more than 11 elements to the surface by a spray. Also a coating comprising a composite material made of amorphous metal that contains more than 11 elements. An apparatus for producing a corrosion-resistant amorphous-metal coating on a structure comprises a deposition chamber, a deposition source in the deposition chamber that produces a deposition spray, the deposition source containing a composite material made of amorphous metal that contains more than 11 elements, and a system that directs the deposition spray onto the structure.

Design and analysis of aerospace structures at elevated temperatures. [aircraft, missiles, and space platforms

NASA Technical Reports Server (NTRS)

Chang, C. I.

1989-01-01

An account is given of approaches that have emerged as useful in the incorporation of thermal loading considerations into advanced composite materials-based aerospace structural design practices. Sources of structural heating encompass not only propulsion system heat and aerodynamic surface heating at supersonic speeds, but the growing possibility of intense thermal fluxes from directed-energy weapons. The composite materials in question range from intrinsically nonheat-resistant polymer matrix systems to metal-matrix composites, and increasingly to such ceramic-matrix composites as carbon/carbon, which are explicitly intended for elevated temperature operation.

Alteration in lipid composition of plasma membranes of sensitive and resistant Guerin carcinoma cells due to the action of free and liposomal form of cisplatin.

PubMed

Naleskina, L A; Todor, I N; Nosko, M M; Lukianova, N Y; Pivnyuk, V M; Chekhun, V F

2013-09-01

To study in vivo changes of lipid composition of plasma membranes of sensitive and resistant to cisplatin Guerin carcinoma cells under influence of free and liposomal cisplatin forms. The isolation of plasma membranes from parental (sensitive) and resistant to cisplatin Guerin carcinoma cells was by differential ultracentrifugation in sucrose density gradient. Lipids were detected by method of thin-layer chromatography. It was determined that more effective action of cisplatin liposomal form on resistant cells is associated with essential abnormalities of conformation of plasma membrane due to change of lipid components and architectonics of rafts. It results in the increase of membrane fluidity. Reconstructions in lipid composition of plasma membranes of cisplatin-resistant Guerin carcinoma cells provide more intensive delivery of drug into the cells, increase of its concentration and more effective interaction with cellular structural elements.

Evolution of technologies applied to space and aeronautic structures

NASA Astrophysics Data System (ADS)

Abiven, H.

Advanced materials in aerospace structures and their use in reusable launch vehicles are discussed. It is found that composite materials can be used for structures with temperatures up to 400 C, and for most structures with heat shielding. For structures with temperatures up to 1000 C, metals such as Norsial, based on rene alloys could be used. It is concluded that a combination of silicon and carbon composites with Aerocoat/TH hydrotranspiration heat shielding give a heat flux resistant structure with no thermal dilation problems.

Mechanisms of charge transport and resistive switching in composite films of semiconducting polymers with nanoparticles of graphene and graphene oxide

NASA Astrophysics Data System (ADS)

Berestennikov, A. S.; Aleshin, A. N.

2017-11-01

We have investigated the effect of the resistive switching in the composite films based on polyfunctional polymers - PVK, PFD and PVC mixed with particles of Gr and GO with the concentration of ˜ 1 - 3 wt.%. We have developed the solution processed hybrid memory structures based on PVK and GO particles composite films. The effect of the resistive switching in Al/PVK(PFD; PVC):Gr(GO)/ITO/PET structures manifests itself as a sharp change of the electrical resistance from a low-conducting state to a relatively high-conducting state when applying a bias to Al-ITO electrodes of ˜ 0.2-0.4 V. It has been established that a sharp conductivity jump characterized by S-shaped current-voltage curves and the presence of their hysteresis occurs upon applying a voltage pulse to the Au/PVK(PFD; PVC):Gr(GO)/ITO/PET structures, with the switching time in the range from 1 to 30 μs. The mechanism of resistive switching associated with the processes of capture and accumulation of charge carriers by Gr(GO) particles introduced into the matrixes of the PVK polymer due to the reduction/oxidation processes. The possible mechanisms of energy transfer between organic and inorganic components in PVK(PFD; PVC):GO(Gr) films causes increase mobility are discussed. Incorporating of Gr (GO) particles into the polymer matrix is a promising route to enhance the performance of hybrid memory structures, as well as it is an effective medium for memory cells.

An electrical-heating and self-sensing shape memory polymer composite incorporated with carbon fiber felt

NASA Astrophysics Data System (ADS)

Gong, Xiaobo; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2016-03-01

Shape memory polymers (SMPs) have the ability to adjust their stiffness, lock a temporary shape, and recover the permanent shape upon imposing an appropriate stimulus. They have found their way into the field of morphing structures. The electrically Joule resistive heating of the conductive composite can be a desirable stimulus to activate the shape memory effect of SMPs without external heating equipment. Electro-induced SMP composites incorporated with carbon fiber felt (CFF) were explored in this work. The CFF is an excellent conductive filler which can easily spread throughout the composite. It has a huge advantage in terms of low cost, simple manufacturing process, and uniform and tunable temperature distribution while heating. A continuous and compact conductive network made of carbon fibers and the overlap joints among them was observed from the microscopy images, and this network contributes to the high conductive properties of the CFF/SMP composites. The CFF/SMP composites can be electrical-heated rapidly and uniformly, and its’ shape recovery effect can be actuated by the electrical resistance Joule heating of the CFF without an external heater. The CFF/SMP composite get higher modulus and higher strength than the pure SMP without losing any strain recovery property. The high dependence of temperature and strain on the electrical resistance also make the composite a good self-sensing material. In general, the CFF/SMP composite shows great prospects as a potential material for the future morphing structures.

Sputter deposited titanium disilicide at high substrate temperatures

NASA Astrophysics Data System (ADS)

Tanielian, M.; Blackstone, S.; Lajos, R.

1984-08-01

Titanium disilicide films were sputter deposited from a composite TiSi2.1 target on <111> bare silicon wafers both at room temperature and at 600 °C. The room temperature as-deposited films require a 900 °C sintering step to reduce their resistivity. On the other hand, the as-deposited 600 °C films are fully reacted, polycrystalline, have no oxygen contamination, large grain sizes, and are oxidation resistant. Further annealing of these films at 900 °C produces no changes in their crystal structure, composition, resistivity, or grain size.

The electrical resistivity and percolation threshold of MWCNTs/polymer composites filled with a few aligned carbonyl iron particles

NASA Astrophysics Data System (ADS)

Dong, Shuai; Wang, Xiaojie

2018-03-01

Conductive polymer composites (CPCs) consist of multi-walled carbon nanotubes (MWCNTs), a few carbonyl iron particles (CIPs) and polydimethylsiloxane (PDMS) are fabricated under a moderate magnetic field. The alignment of CIPs will change the structure of MWCNT network, and consequently the electrical properties of CPCs. The volume fraction of CIPs is fixed at 0.08 vol% at which CIPs will not directly participate in electric conduction. The electrical resistivity of CPCs and the changes of resistance versus strain are evaluated at various MWCNT volume fractions. The testing results show that a percolation threshold as low as 0.19 vol% is obtained due to the effect of aligned CIPs, comparing with 0.39 vol% of isotropic MWCNT/CIP/PDMS (prepared without magnetic field). Meanwhile, the anisotropic structure reduces the electrical resistivity by more than 80% when the MWCNT volume fractions is over the percolation threshold.

Features of Wear-Resistant Cast Iron Coating Formation During Plasma-Powder Surfacing

NASA Astrophysics Data System (ADS)

Vdovin, K. N.; Emelyushin, A. N.; Nefed'ev, S. P.

2017-09-01

The structure of coatings deposited on steel 45 by plasma-powder surfacing of white wear-resistant cast iron is studied. The effects of surfacing regime and additional production effects on the welding bath during surfacing produced by current modulation, accelerated cooling of the deposited beads by blowing with air, and accelerated cooling of the substrate with running water on the structure, are determined. A new composition is suggested for powder material for depositing wear-resistant and corrosion-resistant coatings on a carbon steel by the plasma-powder process.

Polymer-based composites for aerospace: An overview of IMAST results

NASA Astrophysics Data System (ADS)

Milella, Eva; Cammarano, Aniello

2016-05-01

This paper gives an overview of technological results, achieved by IMAST, the Technological Cluster on Engineering of Polymeric Composite Materials and Structures, in the completed Research Projects in the aerospace field. In this sector, the Cluster developed different solutions: lightweight multifunctional fiber-reinforced polymer composites for aeronautic structures, advanced manufacturing processes (for the optimization of energy consumption and waste reduction) and multifunctional components (e.g., thermal, electrical, acoustic and fire resistance).

An addressable conducting network for autonomic structural health management of composite structures

NASA Astrophysics Data System (ADS)

Takahashi, Kosuke; Park, Jong Se; Hahn, H. Thomas

2010-10-01

The electrical resistance change method (ERCM) has long been an area of interest as an in-service health monitoring system. To apply the ERCM to existing structures, a new concept, the addressable conducting network (ACN), is proposed for autonomic structural health management of graphite/polymer composites. The ACN consists of two sets of conducting lines normal to each other, where one set resides on the top surface of the laminate and the other on the bottom surface. Damage can be detected by monitoring the resistance change 'through the laminate thickness' between two lines. By using a thermally mendable polymer as the matrix, the same conducting lines can be used to supply the electric current needed for resistive heating, thereby allowing the detected damage to be healed. As shown experimentally, the electrical resistance change method using an ACN distinguishes between laminates made of properly and improperly cured prepreg as well as revealing damage generated during three-point bending tests. Finite element analysis was performed to examine the feasibility of the ACN and indicated that the damage can be easily located from the spatial distribution of resistance changes and that the damaged area can be locally heated by supplying a large amount of current to selected conducting lines.

Tribological Properties of AlSi12-Al₂O₃ Interpenetrating Composite Layers in Comparison with Unreinforced Matrix Alloy.

PubMed

Dolata, Anna Janina

2017-09-06

Alumina-Aluminum composites with interpenetrating network structures are a new class of advanced materials with potentially better properties than composites reinforced by particles or fibers. Local casting reinforcement was proposed to take into account problems with the machinability of this type of materials and the shaping of the finished products. The centrifugal infiltration process fabricated composite castings in the form of locally reinforced shafts. The main objective of the research presented in this work was to compare the tribological properties (friction coefficient, wear resistance) of AlSi12/Al₂O₃ interpenetrating composite layers with unreinforced AlSi12 matrix areas. Profilometric tests enabled both quantitative and qualitative analyses of the wear trace that formed on investigated surfaces. It has been shown that interpenetrating composite layers are characterized by lower and more stable coefficients of friction (μ), as well as higher wear resistance than unreinforced matrix areas. At the present stage, the study confirmed that the tribological properties of the composite layers depend on the spatial structure of the ceramic reinforcement, and primarily the volume and size of alumina foam cells.

Cell wall composition and penetration resistance against the fungal pathogen Colletotrichum higginsianum are affected by impaired starch turnover in Arabidopsis mutants.

PubMed

Engelsdorf, Timo; Will, Cornelia; Hofmann, Jörg; Schmitt, Christine; Merritt, Brian B; Rieger, Leonie; Frenger, Marc S; Marschall, André; Franke, Rochus B; Pattathil, Sivakumar; Voll, Lars M

2017-01-01

Penetration resistance represents the first level of plant defense against phytopathogenic fungi. Here, we report that the starch-deficient Arabidopsis thaliana phosphoglucomutase (pgm) mutant has impaired penetration resistance against the hemibiotrophic fungus Colletotrichum higginsianum. We could not determine any changes in leaf cutin and epicuticular wax composition or indolic glucosinolate levels, but detected complex alterations in the cell wall monosaccharide composition of pgm. Notably, other mutants deficient in starch biosynthesis (adg1) or mobilization (sex1) had similarly affected cell wall composition and penetration resistance. Glycome profiling analysis showed that both overall cell wall polysaccharide extractability and relative extractability of specific pectin and xylan epitopes were affected in pgm, suggesting extensive structural changes in pgm cell walls. Screening of mutants with alterations in content or modification of specific cell wall monosaccharides indicated an important function of pectic polymers for penetration resistance and hyphal growth of C. higginsianum during the biotrophic interaction phase. While mutants with affected pectic rhamnogalacturonan-I (mur8) were hypersusceptible, penetration frequency and morphology of fungal hyphae were impaired on pmr5 pmr6 mutants with increased pectin levels. Our results reveal a strong impact of starch metabolism on cell wall composition and suggest a link between carbohydrate availability, cell wall pectin and penetration resistance.

Research on the fragment impact resistance of a composite mast

NASA Astrophysics Data System (ADS)

Zhang, Wei; Wu, Chao; Yang, Wenshan; Xu, Shanshan; Ren, Shaofei

2011-09-01

Due to the unique structural mode and material property of a composite sandwich plate, related research such as fragment impact resistance of a composite mast is short of publication and urgent in this field. In this paper, the commonly accepted sandwich core board theory was modified. Damage caused by a fragment attack was simulated onto a sandwich plate model built with solid and shell elements. It was shown that shear failure and vast matrix cracking are the main reasons for outer coat damage, and tension failure and partial matrix cracking are the cause for inner coat damage. Additionally, according to complexities in actual sea battles, different work conditions of missile attacks were set. Ballistic limit values of different fragment sizes were also obtained, which provides references for enhancing the fragment impact resistance of a composite mast.

Effect of remaining coronal structure on the resistance to fracture of crowned endodontically treated maxillary first premolars.

PubMed

Nissan, Joseph; Barnea, Eitan; Bar Hen, Doron; Assif, David

2008-09-01

Endodontically treated maxillary first premolars present a restorative challenge. The objective of the present study was to assess the resistance to fracture of crowned endodontically treated maxillary first premolars under simulated occlusal load, while preserving various degrees of remaining coronal structure. The study consisted of 50 intact maxillary first premolars with bifurcated roots and similar root diameter and length, randomly divided into 5 equal experimental groups. All dowels were luted with Flexi-Flow titanium-reinforced composite resin cement. TiCore titanium-reinforced composite resin was used to fabricate the core. Complete cast crowns were fabricated and cemented with zinc phosphate cement. Forces at fracture and mode of failure were recorded. Statistically significant differences (P < .05) were found among mean failure forces for all tested groups in their resistance to fracture under load with the Kruskal-Wallias test and among all combinations of the 5 groups (Z = -1.56/-2.34; P > .05) with the Mann-Whitney test. This indicates that crowned maxillary first premolars with varying degrees of remaining coronal structure differ significantly in their resistance to fracture under occlusal load. There was increased protection against fracture under occlusal loads with more remaining tooth structure. Within the limitations of this study, remaining coronal structure influenced the fracture resistance of crowned endodontically treated maxillary first premolars. Preservation of tooth structure is important for its protection against fracture under occlusal loads and may influence the tooth prognosis.

Influence of reinforcement type on the mechanical behavior and fire response of hybrid composites and sandwich structures

NASA Astrophysics Data System (ADS)

Giancaspro, James William

Lightweight composites and structural sandwich panels are commonly used in marine and aerospace applications. Using carbon, glass, and a host of other high strength fiber types, a broad range of laminate composites and sandwich panels can be developed. Hybrid composites can be constructed by laminating multiple layers of varying fiber types while sandwich panels are manufactured by laminating rigid fiber facings onto a lightweight core. However, the lack of fire resistance of the polymers used for the fabrication remains a very important problem. The research presented in this dissertation deals with an inorganic matrix (Geopolymer) that can be used to manufacture laminate composites and sandwich panels that are resistant up to 1000°C. This dissertation deals with the influence of fiber type on the mechanical behavior and the fire response of hybrid composites and sandwich structures manufactured using this resin. The results are categorized into the following distinct studies. (i) High strength carbon fibers were combined with low cost E-glass fibers to obtain hybrid laminate composites that are both economical and strong. The E-glass fabrics were used as a core while the carbon fibers were placed on the tension face and on both tension and compression faces. (ii) Structural sandwich beams were developed by laminating various types of reinforcement onto the tension and compression faces of balsa wood cores. The flexural behavior of the beams was then analyzed and compared to beams reinforced with organic composite. The effect of core density was evaluated using oak beams reinforced with inorganic composite. (iii) To measure the fire response, balsa wood sandwich panels were manufactured using a thin layer of a fire-resistant paste to serve for fire protection. Seventeen sandwich panels were fabricated and tested to measure the heat release rates and smoke-generating characteristics. The results indicate that Geopolymer can be effectively used to fabricate both high strength composite plates and sandwich panels. A 2 mm thick coating of fireproofing on balsa wood is sufficient to satisfy FAA fire requirements.

Electrical Resistance Technique to Monitor SiC Composite Detection

NASA Technical Reports Server (NTRS)

Smith, Craig; Morscher, Gregory; Xia, Zhenhai

2008-01-01

Ceramic matrix composites are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems. The employment of these materials in such applications is limited by the ability to process components reliable and to accurately monitor and predict damage evolution that leads to failure under stressed-oxidation conditions. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. Electrical resistance of SiC/SiC composites is one technique that shows special promise towards this end. Since both the matrix and the fibers are conductive, changes in matrix or fiber properties should relate to changes in electrical conductivity along the length of a specimen or part. The effect of matrix cracking on electrical resistivity for several composite systems will be presented and some initial measurements performed at elevated temperatures under stress-rupture conditions. The implications towards electrical resistance as a technique applied to composite processing, damage detection (health monitoring), and life-modeling will be discussed.

Nano-enhanced aerospace composites for increased damage tolerance and service life damage monitoring

NASA Astrophysics Data System (ADS)

Paipetis, A.; Matikas, T. E.; Barkoula, N. M.; Karapappas, P.; Vavouliotis, A.; Kostopoulos, V.

2009-03-01

This study deals with new generation composite systems which apart from the primary reinforcement at the typical fiber scale (~10 μm) are also reinforced at the nanoscale. This is performed via incorporation of nano-scale additives in typical aerospace matrix systems, such as epoxies. Carbon Nanotubes (CNTs) are ideal candidates as their extremely high aspect ratio and mechanical properties render them advantageous to other nanoscale materials. The result is the significant increase in the damage tolerance of the novel composite systems even at very low CNT loadings. By monitoring the resistance change of the CNT network, information both on the real time deformation state of the composite is obtained as a reversible change in the bulk resistance of the material, and the damage state of the material as an irreversible change in the bulk resistance of the material. The irreversible monotonic increase of the electrical resistance can be related to internal damage in the hybrid composite system and may be used as an index of the remaining lifetime of a structural component.

The Electrical and Thermal Conductivity of Woven Pristine and Intercalated Graphite Fiber-Polymer Composites

NASA Technical Reports Server (NTRS)

Gaier, James R.; Vandenburg, Yvonne Yoder; Berkebile, Steven; Stueben, Heather; Balagadde, Frederick

2002-01-01

A series of woven fabric laminar composite plates and narrow strips were fabricated from a variety of pitch-based pristine and bromine intercalated graphite fibers in an attempt to determine the influence of the weave on the electrical and thermal conduction. It was found generally that these materials can be treated as if they are homogeneous plates. The rule of mixtures describes the resistivity of the composite fairly well if it is realized that only the component of the fibers normal to the equipotential surface will conduct current. When the composite is narrow with respect to the fiber weave, however, there is a marked angular dependence of the resistance which was well modeled by assuming that the current follows only along the fibers (and not across them in a transverse direction), and that the contact resistance among the fibers in the composite is negligible. The thermal conductivity of composites made from less conductive fibers more closely followed the rule of mixtures than that of the high conductivity fibers, though this is thought to be an artifact of the measurement technique. Electrical and thermal anisotropy could be induced in a particular region of the structure by weaving together high and low conductivity fibers in different directions, though this must be done throughout all of the layers of the structure as interlaminar conduction precludes having only the top layer carry the anisotropy. The anisotropy in the thermal conductivity is considerably less than either that predicted by the rule of mixtures or the electrical resistivity.

Magnetic and transport properties of Co2Mn1-xCrxSi Heusler alloy thin films

NASA Astrophysics Data System (ADS)

Aftab, M.; Hassnain Jaffari, G.; Hasanain, S. K.; Ali Abbas, Turab; Ismat Shah, S.

2013-09-01

Magnetic, transport, and magnetotransport properties of Co2Mn1-xCrxSi (0 ≤ x ≤ 1) DC sputter grown thin films have been investigated. In films with x > 0.2 saturation magnetization values are seen to deviate from the Slater-Pauling rule due to the enhancement of Co-Cr antisite disorder. The increasing structural disorder eventually results in a sign change of the temperature coefficient of resistivity (at x > 0.6), while a resistivity minimum is observed for the metallic compositions. From resistivity measurements, we conclude that there is a phase transition from a half-metallic ferromagnetic phase to a normal ferromagnetic phase at T ˜ 68 K in composition with x ≤ 0.2. Both the onset temperature and the temperature range for half metallic phase were found to decrease with increasing x among the metallic compositions. Magnetotransport measurements performed on metallic compositions at temperatures below and above the resistivity minimum suggest the presence of both the metallic as well as semiconducting/localized states.

Scientific and Technological Principles of Development of New Cold-Resistant Arc-Steels (Steels for Arctic Applications)

NASA Astrophysics Data System (ADS)

Sych, O. V.; Khlusova, E. I.; Yashin, E. A.

2017-12-01

The paper presents the results of quantitative analysis of C, Mn, Ni and Cu content on strength and cold-resistance of rolled plates. Relations between the ferritic-bainitic structure morphology and anisotropy and steel performance characteristics have been established. Influence of thermal and deformation rolling patterns on steel structure has been studied. The steel chemical composition has been improved and precision thermomechanical processing conditions for production of cold-resistant Arc-steel plates have been developed.

Microstructure and wear resistance of Al2O3-M7C3/Fe composite coatings produced by laser controlled reactive synthesis

NASA Astrophysics Data System (ADS)

Tan, Hui; Luo, Zhen; Li, Yang; Yan, Fuyu; Duan, Rui

2015-05-01

Based on the principle of thermite reaction of Al and Fe2O3 powders, the Al2O3 ceramic reinforced Fe-based composite coatings were fabricated on a steel substrate by laser controlled reactive synthesis and cladding. The effects of different additions of thermite reactants on the phase transition, microstructure evolution, microhardness and wear resistance of the composite coatings were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers microhardness and block-on-ring wear test, respectively. The results show that Al2O3 ceramic and M7C3 carbide are in situ synthesized via the laser controlled reactive synthesis. The Al2O3 ceramic and M7C3 carbides prefer to distribute along the γ-Fe phase boundary continuously, which separates the γ-Fe matrix and is beneficial to the grain refinement. With the increase of thermite reactants, the amount of Al2O3 ceramic and M7C3 carbide in the composite coatings increases gradually. Moreover the cladding layer changes from dendritic structure to columnar structure and martensite structure in the heat affected zone becomes coarse. The increased thermite reactants improve the microhardness and wear resistance of the in situ composite coatings obviously and enhance the hardness of the heat affected zone, which should be ascribed to the grain refinement, ceramic and carbide precipitation and solid solution strengthening.

Effects of laser polishing on surface microstructure and corrosion resistance of additive manufactured CoCr alloys

NASA Astrophysics Data System (ADS)

Wang, W. J.; Yung, K. C.; Choy, H. S.; Xiao, T. Y.; Cai, Z. X.

2018-06-01

Laser polishing of 3D printed metal components has drawn great interest in view of its potential applications in the dental implant industries. In this study, corrosion resistance, surface composition and crystalline structure of CoCr alloys were investigated. The corrosion resistance, micromorphology, composition, phase transformations and crystalline structures of samples were characterized using an electrochemical analyzer, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The results indicate that high laser powers and low object distances within a certain range can facilitate the formation of complex oxide films, which exhibits high corrosion resistance. Further, object distances have a significant influence on cooling rates during the solidification of the melt pool in laser polishing, and fast cooling generates vast amounts of vacancies and defects, which result in the crystalline phase transformation from γ to ε. Consequently, the formed oxides play an important role in corrosion resistance on the outer layer, and inner layer with γ phase also helps keep the CoCr alloys in a stable structure with high resistant to corrosion. The two process parameters in laser polishing, laser power and object distances, are demonstrated as being important for controlling the surface microstructures and corrosion resistance of the additive manufactured CoCr alloy components.

Enhanced protective role in materials with gradient structural orientations: Lessons from Nature.

PubMed

Liu, Zengqian; Zhu, Yankun; Jiao, Da; Weng, Zhaoyong; Zhang, Zhefeng; Ritchie, Robert O

2016-10-15

Living organisms are adept at resisting contact deformation and damage by assembling protective surfaces with spatially varied mechanical properties, i.e., by creating functionally graded materials. Such gradients, together with multiple length-scale hierarchical structures, represent the two prime characteristics of many biological materials to be translated into engineering design. Here, we examine one design motif from a variety of biological tissues and materials where site-specific mechanical properties are generated for enhanced protection by adopting gradients in structural orientation over multiple length-scales, without manipulation of composition or microstructural dimension. Quantitative correlations are established between the structural orientations and local mechanical properties, such as stiffness, strength and fracture resistance; based on such gradients, the underlying mechanisms for the enhanced protective role of these materials are clarified. Theoretical analysis is presented and corroborated through numerical simulations of the indentation behavior of composites with distinct orientations. The design strategy of such bioinspired gradients is outlined in terms of the geometry of constituents. This study may offer a feasible approach towards generating functionally graded mechanical properties in synthetic materials for improved contact damage resistance. Living organisms are adept at resisting contact damage by assembling protective surfaces with spatially varied mechanical properties, i.e., by creating functionally-graded materials. Such gradients, together with multiple length-scale hierarchical structures, represent the prime characteristics of many biological materials. Here, we examine one design motif from a variety of biological tissues where site-specific mechanical properties are generated for enhanced protection by adopting gradients in structural orientation at multiple length-scales, without changes in composition or microstructural dimension. The design strategy of such bioinspired gradients is outlined in terms of the geometry of constituents. This study may offer a feasible approach towards generating functionally-graded mechanical properties in synthetic materials for improved damage resistance. Published by Elsevier Ltd.

A CMC database for use in the next generation launch vehicles (rockets)

NASA Astrophysics Data System (ADS)

Mahanta, Kamala

1994-10-01

Ceramic matrix composites (CMC's) are being envisioned as the state-of-the-art material capable of handling the tough structural and thermal demands of advanced high temperature structures for programs such as the SSTO (Single Stage to Orbit), HSCT (High Speed Civil Transport), etc. as well as for evolution of the industrial heating systems. Particulate, whisker and continuous fiber ceramic matrix (CFCC) composites have been designed to provide fracture toughness to the advanced ceramic materials which have a high degree of wear resistance, hardness, stiffness, and heat and corrosion resistance but are notorious for their brittleness and sensitivity to microscopic flaws such as cracks, voids and impurity.

A CMC database for use in the next generation launch vehicles (rockets)

NASA Technical Reports Server (NTRS)

Mahanta, Kamala

1994-01-01

Ceramic matrix composites (CMC's) are being envisioned as the state-of-the-art material capable of handling the tough structural and thermal demands of advanced high temperature structures for programs such as the SSTO (Single Stage to Orbit), HSCT (High Speed Civil Transport), etc. as well as for evolution of the industrial heating systems. Particulate, whisker and continuous fiber ceramic matrix (CFCC) composites have been designed to provide fracture toughness to the advanced ceramic materials which have a high degree of wear resistance, hardness, stiffness, and heat and corrosion resistance but are notorious for their brittleness and sensitivity to microscopic flaws such as cracks, voids and impurity.

Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugimura, K.; Miyajima, Y.; Sonehara, M.

2016-05-15

This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO{sub 2}) was successfully deposited on the CIP-surface by using hydrolysismore » of TEOS (Si(OC{sub 2}H{sub 5}){sub 4}). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.« less

Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

NASA Astrophysics Data System (ADS)

Sugimura, K.; Miyajima, Y.; Sonehara, M.; Sato, T.; Hayashi, F.; Zettsu, N.; Teshima, K.; Mizusaki, H.

2016-05-01

This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO2) was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC2H5)4). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.

Through-the Thickness(R) braided composites for aircraft applications

NASA Technical Reports Server (NTRS)

Brown, Richard T.

1992-01-01

Material and structural specimens of Through-the-Thickness(R) braided textile composites were tested in a variety of experiments. The results have demonstrated that the preform architecture provides significant payoffs in damage tolerance, delamination resistance, and attachment strength. This paper describes the braiding process, surveys the experimental data base, and illustrates the application of three dimensional braiding in aircraft structures.

Structure and Tribological Properties of B83 Babbit-Based Composite Rods and the Coatings Produced from Them by Arc Surfacing

NASA Astrophysics Data System (ADS)

Bolotova, L. K.; Kalashnikov, I. E.; Kobeleva, L. I.; Katin, I. E.; Kolmakov, A. G.; Mikheev, R. S.; Kobernik, N. V.; Podymova, N. B.

2018-01-01

Surfacing composite rods based on a B83 babbit alloy reinforced by silicon carbide and boron carbide particles are fabricated by extrusion. The structure and the tribological properties of the rods are studied. Extrusion allowed us to introduce and to uniformly distribute reinforcing fillers and to change the size and the morphology of the intermetallic phases in the matrix alloy. The wear resistance of the rods made of the B83 babbit + 5 wt % SiC composite material is shown to be higher than that of commercial B83 alloy samples by a factor of 1.2. Arc surfacing is used to deposit antifriction coatings, which are made of the surfacing composite rods based on B83 babbit reinforced by boron carbide or silicon carbide particles, onto steel substrates. The deposited layers exhibit good adhesion to the substrates: the melting line is continuous and does not contain discontinuities. The structure and the tribological properties of the deposited coatings are studied. The wear resistance of the composite coatings is higher than that of the B83 alloy-based coating by 30%.

Manufacture and performance of carbon/epoxy 3-D woven composites

NASA Technical Reports Server (NTRS)

Brandt, J.; Drechsler, K.; Mohamed, Mansour; Gu, PU

1992-01-01

This paper evaluates 3-D orthogonal woven carbon/epoxy composites. Preforms were manufactured on an automatic 3-D weaving machine developed at N.C. State University. Matrix infiltration was conducted at MBB Central Laboratories. Testing was carried out at both locations and the joint results will be reported. The properties investigated include: interlaminar shear strength, compression, compression after impact, bending, tensile and penetration resistance. The 3-D orthogonal woven composites were compared with laminated and other 3-D composites made with preforms having interlock structure. C-scans were used to examine the quality of infiltration and the damage area after impact. The performance of the composites made from the 3-D orthogonal preforms showed superior properties compared to the other composites. The penetration resistance test showed unexpectedly very good performance.

Microstructure Characterization and Wear-Resistant Properties Evaluation of an Intermetallic Composite in Ni-Mo-Si System.

PubMed

Huang, Boyuan; Song, Chunyan; Liu, Yang; Gui, Yongliang

2017-02-04

Intermetallic compounds have been studied for their potential application as structural wear materials or coatings on engineering steels. In the present work, a newly designed intermetallic composite in a Ni-Mo-Si system was fabricated by arc-melting process with commercially pure metal powders as starting materials. The chemical composition of this intermetallic composite is 45Ni-40Mo-15Si (at %), selected according to the ternary alloy diagram. The microstructure was characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS), and the wear-resistant properties at room temperature were evaluated under different wear test conditions. Microstructure characterization showed that the composite has a dense and uniform microstructure. XRD results showed that the intermetallic composite is constituted by a binary intermetallic compound NiMo and a ternary Mo₂Ni₃Si metal silicide phase. Wear test results indicated that the intermetallic composite has an excellent wear-resistance at room-temperature, which is attributed to the high hardness and strong atomic bonding of constituent phases NiMo and Mo₂Ni₃Si.

Two-dimensional hybrid materials: MoS2-RGO nanocomposites enhanced the barrier properties of epoxy coating

NASA Astrophysics Data System (ADS)

Chen, Chunlin; He, Yi; Xiao, Guoqing; Xia, Yunqin; Li, Hongjie; He, Ze

2018-06-01

By the way of hydrothermal reaction, the MoS2 nanoparticles were loaded on the surface of GO sheets uniformly. Then, the MoS2-RGO composites were modified with γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH560), and followed by preparing the MoS2-RGO/epoxy composite coatings. The morphology and structure of MoS2-RGO were characterized though SEM, TEM, FT-IR and XPS. Besides, the corrosion resistance properties of the as-prepared MoS2-RGO/epoxy composite coatings were characterized by means of electrochemical impedance spectroscopy (EIS) and polarization curves analysis, and then the thermal stability and water permeability resistance of coatings were characterized. The results showed that the MoS2 could be loaded on the surface of GO uniformly when the ratio between MoS2 and GO is 1:1. The anti-corrosion property and permeability resistance of the MoS2-RGO/epoxy composites coating was enhanced significantly due to its excellent barrier property. Besides, the thermal property analysis exhibits that the lamellar structure of MoS2, GO and MoS2-RGO can effectively block the escape of the pyrolysis products, resulting in the maximum thermal weightlessness reduced.

ZrO{sub 2}-ZnO composite thin films for humidity sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velumani, M., E-mail: velumanimohan@gmail.com; Sivacoumar, R.; Alex, Z. C.

2016-05-23

ZrO{sub 2}-ZnO composite thin films were grown by reactive DC magnetron sputtering. X-ray diffraction studies reveal the composite nature of the films with separate ZnO and ZrO{sub 2} phase. Scanning electron microscopy studies confirm the nanocrystalline structure of the films. The films were studied for their impedometric relative humidity (RH) sensing characteristics. The complex impedance plot was fitted with a standard equivalent circuit consisting of an inter-granular resistance and a capacitance in parallel. The DC resistance was found to be decreasing with increase in RH.

Performance evaluations of oxidation-resistant carbon-carbon composites in simulated hypersonic vehicle environments

NASA Technical Reports Server (NTRS)

Barrett, D. M.; Maahs, H. G.; Ohlhorst, C. W.; Vaughn, W. L.; Martin, R. H.

1989-01-01

An evaluation is made of the oxidation-protection requirements of carbon-carbon composite (CCC) structural components in a hypersonic vehicle aerothermodynamic environment, where maximum test temperatures in air are of the order of 2800 F, and pressures range from 0.03 to 1.0 atm. The specimens were exposed to high humidity between tests. Attention was given to the effects of coating composition and thickness, and of substrate architecture and surface preparation, on the oxidation resistance of CCCs. Both surface preparation and coating chemistry have a profound effect on coating adherence and longevity.

Preparation for foam composites. [using polybenzimidazole for fireproofing panels

NASA Technical Reports Server (NTRS)

Maximovich, M. G.

1974-01-01

Methods were developed for the fabrication of fire resistant panels utilizing polybenzimidazole (PBI) and Kerimid 601 resins along with glass, quartz, and Kevlar reinforcements. Stitched truss structure, both unfilled and filled with PBI foam, were successfully fabricated and tested. Second generation structures were then selected, fabricated, and tested, with a PBI/glass skin/PBI foam sandwich structure emerging as the optimum panel concept. Mechanical properties, smoke generation, and fire resistance were determined for the candidate panels.

Tunable resistance coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elam, Jeffrey W.; Mane, Anil U.

2015-08-11

A method and article of manufacture of intermixed tunable resistance composite materials containing at least one of W:Al.sub.2O.sub.3, Mo:Al.sub.2O.sub.3 or M:Al.sub.2O.sub.3 where M is a conducting compound containing either W or Mo. A conducting material and an insulating material are deposited by such methods as ALD or CVD to construct composites with intermixed materials which do not have structure or properties like their bulk counterparts.

Conductive Composites Made Less Expensively

NASA Technical Reports Server (NTRS)

Gaier, James R.

2005-01-01

The use of electrically conductive composite structures for electrostatic dissipation, electromagnetic interference shielding, and ground return planes could save between 30 and 90 percent of the mass of the structure, in comparison to aluminum. One strategy that has been shown to make conducting composites effectively uses intercalated graphite fiber as the reinforcement. Intercalation--the insertion of guest atoms or molecules between the graphene planes--can lower the electrical resistivity of graphite fibers by as much as a factor of 10, without sacrificing mechanical or thermal properties.

Cloning Nacre's 3D Interlocking Skeleton in Engineering Composites to Achieve Exceptional Mechanical Properties.

PubMed

Zhao, Hewei; Yue, Yonghai; Guo, Lin; Wu, Juntao; Zhang, Youwei; Li, Xiaodong; Mao, Shengcheng; Han, Xiaodong

2016-07-01

Ceramic/polymer composite equipped with 3D interlocking skeleton (3D IL) is developed through a simple freeze-casting method, exhibiting exceptionally light weight, high strength, toughness, and shock resistance. Long-range crack energy dissipation enabled by 3D interlocking structure is considered as the primary reinforcing mechanism for such superior properties. The smart composite design strategy should hold a place in developing future structural engineering materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Patterns of cell division, DNA base compositions, and fine structures of some radiation-resistant vegetative bacteria found in food

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanders, S.W.; Maxcy, R.B.

1979-01-01

Representative highly radiation-resistant Moraxella-Acinetobacter (M-A), Pseudomonas radiora, Micrococcus radiodurans, and Micrococcus radiophilus exhibited a wide variety of division systems and cell wall characteristics. However, the more resistant M-A possessed unusually thick cell walls, indicating a possible role of the cell wall in radiation resistance in the M-A. Thick septation was present in most of the bacteria studied, but was absent in P. radiora, thus excluding this as a necessity for high resistance. Reliable determination of the number of division planes of the M-A for use as a taxonomic criterion was achieved by the direct observation of dividing cells. The highlymore » resistant M-A were found to divide in multiple planes and had base compositions of 54.0 to 57.5%, unlike typical Moraxella and/or Acinetobacter species. The taxonomic position of most highly resistant bacteria remains unclear.« less

Improved Damage Resistant Composite Materials Incorporating Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Paine, Jeffrey S. N.; Rogers, Craig A.

1996-01-01

Metallic shape memory alloys (SMA) such as nitinol have unique shape recovery behavior and mechanical properties associated with a material phase change that have been used in a variety of sensing and actuation applications. Recent studies have shown that integrating nitinol-SMA actuators into composite materials increases the composite material's functionality. Hybrid composites of conventional graphite/epoxy or glass/epoxy and nitinol-SMA elements can perform functions in applications where monolithic composites perform inadequately. One such application is the use of hybrid composites to function both in load bearing and armor capacities. While monolithic composites with high strength-to-weight ratios function efficiently as loadbearing structures, because of their brittle nature, impact loading can cause significant catastrophic damage. Initial composite failure modes such as delamination and matrix cracking dissipate some impact energy, but when stress exceeds the composite's ultimate strength, fiber fracture and material perforation become dominant. One of the few methods that has been developed to reduce material perforation is hybridizing polymer matrix composites with tough kevlar or high modulus polyethynylene plies. The tough fibers increase the impact resistance and the stiffer and stronger graphite fibers carry the majority of the load. Similarly, by adding nitinol-SMA elements that absorb impact energy through the stress-induced martensitic phase transformation, the composites' impact perforation resistance can be greatly enhanced. The results of drop-weight and high velocity gas-gun impact testing of various composite materials will be presented. The results demonstrate that hybridizing composites with nitinol-SMA elements significantly increases perforation resistance compared to other traditional toughening elements. Inspection of the composite specimens at various stages of perforation by optical microscope illustrates the mechanisms by which perforation is initiated. Results suggest that the out-of-plane transverse shear properties of the composite and nitinol elements have a significant effect on the perforation resistance. Applications that can utilize the hybrid composites effectively will also be presented with the experimental studies.

Cell wall composition and penetration resistance against the fungal pathogen Colletotrichum higginsianum are affected by impaired starch turnover in Arabidopsis mutants

PubMed Central

Engelsdorf, Timo; Will, Cornelia; Hofmann, Jörg; Schmitt, Christine; Merritt, Brian B.; Rieger, Leonie; Frenger, Marc S.; Marschall, André; Franke, Rochus B.; Pattathil, Sivakumar

2017-01-01

Abstract Penetration resistance represents the first level of plant defense against phytopathogenic fungi. Here, we report that the starch-deficient Arabidopsis thaliana phosphoglucomutase (pgm) mutant has impaired penetration resistance against the hemibiotrophic fungus Colletotrichum higginsianum. We could not determine any changes in leaf cutin and epicuticular wax composition or indolic glucosinolate levels, but detected complex alterations in the cell wall monosaccharide composition of pgm. Notably, other mutants deficient in starch biosynthesis (adg1) or mobilization (sex1) had similarly affected cell wall composition and penetration resistance. Glycome profiling analysis showed that both overall cell wall polysaccharide extractability and relative extractability of specific pectin and xylan epitopes were affected in pgm, suggesting extensive structural changes in pgm cell walls. Screening of mutants with alterations in content or modification of specific cell wall monosaccharides indicated an important function of pectic polymers for penetration resistance and hyphal growth of C. higginsianum during the biotrophic interaction phase. While mutants with affected pectic rhamnogalacturonan-I (mur8) were hypersusceptible, penetration frequency and morphology of fungal hyphae were impaired on pmr5 pmr6 mutants with increased pectin levels. Our results reveal a strong impact of starch metabolism on cell wall composition and suggest a link between carbohydrate availability, cell wall pectin and penetration resistance. PMID:28204541

Impact damage resistance of composite fuselage structure, part 1

NASA Technical Reports Server (NTRS)

Dost, E. F.; Avery, W. B.; Ilcewicz, L. B.; Grande, D. H.; Coxon, B. R.

1992-01-01

The impact damage resistance of laminated composite transport aircraft fuselage structures was studied experimentally. A statistically based designed experiment was used to examine numerous material, laminate, structural, and extrinsic (e.g., impactor type) variables. The relative importance and quantitative measure of the effect of each variable and variable interactions on responses including impactor dynamic response, visibility, and internal damage state were determined. The study utilized 32 three-stiffener panels, each with a unique combination of material type, material forms, and structural geometry. Two manufacturing techniques, tow placement and tape lamination, were used to build panels representative of potential fuselage crown, keel, and lower side-panel designs. Various combinations of impactor variables representing various foreign-object-impact threats to the aircraft were examined. Impacts performed at different structural locations within each panel (e.g., skin midbay, stiffener attaching flange, etc.) were considered separate parallel experiments. The relationship between input variables, measured damage states, and structural response to this damage are presented including recommendations for materials and impact test methods for fuselage structure.

Impact damage resistance and damage suppression properties of shape memory alloys in hybrid composites—a review

NASA Astrophysics Data System (ADS)

Angioni, S. L.; Meo, M.; Foreman, A.

2011-01-01

Composite materials are known to have a poor resistance to through-the-thickness impact loading. There are various methods for improving their impact damage tolerance, such as fiber toughening, matrix toughening, interface toughening, through-the-thickness reinforcements, and selective interlayers and hybrids. Hybrid composites with improved impact resistance are particularly useful in military and commercial civil applications. Hybridizing composites using shape memory alloys (SMA) is one solution since SMA materials can absorb the energy of the impact through superelastic deformation or recovery stress, reducing the effects of the impact on the composite structure. The SMA material may be embedded in the hybrid composites (SMAHC) in many different forms and also the characteristics of the fiber reinforcements may vary, such as SMA wires in woven laminates or SMA foils in unidirectional laminates, only to cite two examples. We will review the state of the art of SMAHC for the purpose of damage suppression. Both the active and passive damage suppression mechanisms will be considered.

Tribological Properties of AlSi12-Al2O3 Interpenetrating Composite Layers in Comparison with Unreinforced Matrix Alloy

PubMed Central

Dolata, Anna Janina

2017-01-01

Alumina–Aluminum composites with interpenetrating network structures are a new class of advanced materials with potentially better properties than composites reinforced by particles or fibers. Local casting reinforcement was proposed to take into account problems with the machinability of this type of materials and the shaping of the finished products. The centrifugal infiltration process fabricated composite castings in the form of locally reinforced shafts. The main objective of the research presented in this work was to compare the tribological properties (friction coefficient, wear resistance) of AlSi12/Al2O3 interpenetrating composite layers with unreinforced AlSi12 matrix areas. Profilometric tests enabled both quantitative and qualitative analyses of the wear trace that formed on investigated surfaces. It has been shown that interpenetrating composite layers are characterized by lower and more stable coefficients of friction (μ), as well as higher wear resistance than unreinforced matrix areas. At the present stage, the study confirmed that the tribological properties of the composite layers depend on the spatial structure of the ceramic reinforcement, and primarily the volume and size of alumina foam cells. PMID:28878162

The interface in tungsten fiber reinforced niobium metal-matrix composites. Final Report Ph.D. Thesis - Case Western Reserve Univ., Cleveland, OH

NASA Technical Reports Server (NTRS)

Grobstein, Toni L.

1989-01-01

The creep resistance of tungsten fiber reinforced niobium metal-matrix composites was evaluated. The interface region between the fiber and matrix was characterized by microhardness and electron probe microanalysis measurements which indicated that its properties were between those of fiber and matrix. However, the measured properties of the composite exceeded those calculated by the rule of mixtures even when the interface zone was assumed to retain all the strength of the fiber. The composite structure appeared to enhance the strengths of both the fibers and the matrix above what they exhibited in stand-alone tests. The effect of fiber orientation and matrix alloy composition on the fiber/matrix interface were also evaluated. Small alloying additions of zirconium and tungsten to the niobium matrix affected the creep resistance of the composites only slightly. A decrease in the creep resistance of the composite with increasing zirconium content in the matrix was ascribed to an increase in the diffusion rate of the fiber/matrix interdiffusion reaction, and a slight increase in the creep resistance of the composite was observed with an addition of 9 w percent tungsten to the matrix. In addition, Kirkendall void formation was observed at the fiber/matrix interface; the void distribution differed depending on the fiber orientation relative to the stress axis.

Passively Damped Laminated Piezoelectric Shell Structures with Integrated Electric Networks

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.

1999-01-01

Multi-field mechanics are presented for curvilinear piezoelectric laminates interfaced with distributed passive electric components. The equations of motion for laminated piezoelectric shell structures with embedded passive electric networks are directly formulated and solved using a finite element methodology. The modal damping and frequencies of the piezoelectric shell are calculated from the poles of the system. Experimental and numerical results are presented for the modal damping and frequency of composite beams with a resistively shunted piezoceramic patch. The modal damping and frequency of plates, cylindrical shells and cylindrical composite blades with piezoelectric-resistor layers are predicted. Both analytical and experimental studies illustrate a unique dependence of modal damping and frequencies on the shunting resistance and show the effect of structural shape and curvature on piezoelectric damping.

Design for inadvertent damage in composite laminates

NASA Technical Reports Server (NTRS)

Singhal, Surendra N.; Chamis, Christos C.

1992-01-01

Simplified predictive methods and models to computationally simulate durability and damage in polymer matrix composite materials/structures are described. The models include (1) progressive fracture, (2) progressively damaged structural behavior, (3) progressive fracture in aggressive environments, (4) stress concentrations, and (5) impact resistance. Several examples are included to illustrate applications of the models and to identify significant parameters and sensitivities. Comparisons with limited experimental data are made.

Sporulation environment influences spore properties in Bacillus: evidence and insights on underlying molecular and physiological mechanisms.

PubMed

Bressuire-Isoard, Christelle; Broussolle, Véronique; Carlin, Frédéric

2018-05-17

Bacterial spores are resistant to physical and chemical insults, which make them a major concern for public health and for industry. Spores help bacteria to survive extreme environmental conditions that vegetative cells cannot tolerate. Spore resistance and dormancy are important properties for applications in medicine, veterinary health, food safety, crop protection, and other domains. The resistance of bacterial spores results from a protective multilayered structure and from the unique composition of the spore core. The mechanisms of sporulation and germination, the first stage after breaking of dormancy, and organization of spore structure have been extensively studied in Bacillus species. This review aims to illustrate how far the structure, composition and properties of spores are shaped by the environmental conditions in which spores form. We look at the physiological and molecular mechanisms underpinning how sporulation media and environment deeply affect spore yield, spore properties like resistance to wet heat and physical and chemical agents, germination, and further growth. For example, spore core water content decreases as sporulation temperature increases, and resistance to wet heat increases. Controlling the fate of Bacillus spores is pivotal to controlling bacterial risks and process efficiencies in, for example, the food industry, and better control hinges on better understanding how sporulation conditions influence spore properties.

Increasing the wear resistance of ultra-high molecular weight polyethylene by adding solid lubricating fillers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panin, S. V., E-mail: svp@ispms.tsc.ru; Kornienko, L. A.; Poltaranin, M. A.

2014-11-14

In order to compare effectiveness of adding solid lubricating fillers for polymeric composites based on ultra-high molecular weight polyethylene (UHMWPE) with graphite, molybdenum disulfide and polytetrafluoroethylene, their tribotechnical characteristics under dry friction, boundary lubrication and abrasive wearing were investigated. The optimal weight fractions of fillers in terms of improving wear resistance have been determined. The supramolecular structure and topography of wear track surfaces of UHMWPE-based composites with different content of fillers have been studied.

Boron/aluminum graphite/resin advanced fiber composite hybrids

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

1975-01-01

Fabrication feasibility and potential of an adhesively bonded metal and resin matrix fiber-composite hybrid are determined as an advanced material for aerospace and other structural applications. The results show that using this hybrid concept makes possible a composite design which, when compared with nonhybrid composites, has greater transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

A Study on 3-Body Abrasive Wear Behaviour of Aluminium 8011 / Graphite Metal Matrix Composite

NASA Astrophysics Data System (ADS)

Latha Shankar, B.; Anil, K. C.; Patil, Rahul

2016-09-01

Metals and alloys have found their vital role in many applications like structural, corrosive, tribological, etc., in engineering environment. The alloys/composites having high strength to low weight ratio have gained attention of many researchers recently. In this work, graphite reinforced Aluminium 8011 metal matrix composite was prepared by conventional stir casting route, by varying the weight % of reinforcement. Uniform distribution of Graphite in matrix alloy was confirmed by optical micrographs. Prepared composite specimens were subjected to 3-body abrasive testing by varying applied load and time, the silica particles of 400 grit size were used as abrasive particles. It was observed that with the increase of weight% of Graphite the wear resistance of composite was also increasing and on comparison it was found that reinforced composite gives good wear resistance than base alloy.

Growth mechanism, distribution characteristics and reinforcing behavior of (Ti, Nb)C particle in laser cladded Fe-based composite coating

NASA Astrophysics Data System (ADS)

Li, Qingtang; Lei, Yongping; Fu, Hanguang

2014-10-01

Over the past decade, researchers have demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance, corrosion resistance, and high temperature properties. In this paper, in-situ (Ti, Nb)C particle reinforced Fe-based composite coatings were produced by laser cladding. The effects of Ti/Nb(atomic ratio) in the cladding powder on the formation mechanism and distribution characteristics of multiple particle were investigated. The results showed that when Ti/Nb > 1, Ti had a stronger ability to bond with C compared with Nb. (Ti, Nb)C multiple particles with TiC core formed in the molten pool. With the decrease of Ti/Nb, core-shell structure disappeared, the structure of particle got close to that of NbC gradually. It is found that the amount, area ratio and distribution of the reinforced particle in the coating containing Ti and Nb elements were improved, compared with these in the coating containing equal Nb element. When Ti/Nb = 1, the effects above-mentioned is most prominent, and the wear resistance of the coating is promoted obviously.

Mechanical energy dissipation in natural ceramic composites.

PubMed

Mayer, George

2017-12-01

Ceramics and glasses, in their monolithic forms, typically exhibit low fracture toughness values, but rigid natural marine ceramic and glass composites have shown remarkable resistance to mechanical failure. This has been observed in load-extension behavior by recognizing that the total area under the curve, notably the part beyond the yield point, often conveys substantial capacity to carry mechanical load. The mechanisms underlying the latter observations are proposed as defining factors for toughness that provide resistance to failure, or capability to dissipate energy, rather than fracture toughness. Such behavior is exhibited in the spicules of glass sponges and in mollusk shells. There are a number of similarities in the manner in which energy dissipation takes place in both sponges and mollusks. It was observed that crack diversion, a new form of crack bridging, creation of new surface area, and other important energy-dissipating mechanisms occur and aid in "toughening". Crack tolerance, key to energy dissipation in these natural composite materials, is assisted by promoting energy distribution over large volumes of loaded specimens by minor components of organic constituents that also serve important roles as adhesives. Viscoelastic deformation was a notable characteristic of the organic component. Some of these energy-dissipating modes and characteristics were found to be quite different from the toughening mechanisms that are utilized for more conventional structural composites. Complementary to those mechanisms found in rigid natural ceramic/organic composites, layered architectures and very thin organic layers played major roles in energy dissipation in these structures. It has been demonstrated in rigid natural marine composites that not only architecture, but also the mechanical behavior of the individual constituents, the nature of the interfaces, and interfacial bonding play important roles in energy dissipation. Additionally, the controlling effects of thin organic layers have been observed in other natural ceramic composite structures, such as teeth and bones, indicating that a variety of similar energy dissipating mechanisms in natural ceramic composites may operate as means to resist failure. Copyright © 2017 Elsevier Ltd. All rights reserved.

Strong, Tough, and Pest Resistant MoSi2-Base Hybrid Composite for Structural Applications

NASA Technical Reports Server (NTRS)

Hebsur, M. G.; Nathal, M. V.

1997-01-01

Addition of about 30 to 50 vol % of Si3N4 particulate to MoSi2 improved resistance to low temperature accelerated oxidation by forming a Si2ON2 protective scale and thereby eliminating catastrophic 'pest failure'. The Si3N4 addition also improved the high temperature creep strength by nearly five orders of magnitude, doubled the room temperature toughness and significantly lowered the CTE of the MoSi2 and eliminated matrix cracking in SCS-6 reinforced composites even after thermal cycling. The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times. The composite exhibited excellent strength and toughness improvement up to 1400 C. More recently, tape casting was adopted as the preferred processing of MoSi2-base composites for improved fiber spacing, ability to use small diameter fibers, and for lower cost. Good strength and toughness values were also obtained with fine diameter Hi-Nicalon tow fibers. This hybrid composite remains competitive with ceramic matrix composites as a replacement for Ni-base superalloys in aircraft engine applications.

Investigation on strain sensing properties of carbon-based nanocomposites for structural aircraft applications

NASA Astrophysics Data System (ADS)

Lamberti, Patrizia; Spinelli, Giovanni; Tucci, Vincenzo; Guadagno, Liberata; Vertuccio, Luigi; Russo, Salvatore

2016-05-01

The mechanical and electrical properties of a thermosetting epoxy resin particularly indicated for the realization of structural aeronautic components and reinforced with multiwalled carbon nanotubes (MWCNTs, at 0.3 wt%) are investigated for specimens subjected to cycles and different levels of applied strain (i.e. ɛ) loaded both in axial tension and flexural mode. It is found that the piezoresistive behavior of the resulting nanocomposite evaluated in terms of variation of the electrical resistance is strongly affected by the applied mechanical stress mainly due to the high sensibility and consequent rearrangement of the electrical percolating network formed by MWCNTs in the composite at rest or even under a small strain. In fact, the variations in electrical resistance that occur during the mechanical stress are correlated to the deformation exhibited by the nanocomposites. In particular, the overall response of electrical resistance of the composite is characterized by a linear increase with the strain at least in the region of elastic deformation of the material in which the gauge factor (i.e. G.F.) of the sensor is usually evaluated. Therefore, the present study aims at investigating the possible use of the nanotechnology for application of embedded sensor systems in composite structures thus having capability of self-sensing and of responding to the surrounding environmental changes, which are some fundamental requirements especially for structural aircraft monitoring applications.

Structure-property relationships in an Al matrix Ca nanofilamentary composite conductor with potential application in high-voltage power transmission

NASA Astrophysics Data System (ADS)

Tian, Liang

This study investigated the processing-structure-properties relationships in an Al/Ca composites using both experiments and modeling/simulation. A particular focus of the project was understanding how the strength and electrical conductivity of the composite are related to its microstructure in the hope that a conducting material with light weight, high strength, and high electrical conductivity can be developed to produce overhead high-voltage power transmission cables. The current power transmission cables (e.g., Aluminum Conductor Steel Reinforced (ACSR)) have acceptable performance for high-voltage AC transmission, but are less well suited for high-voltage DC transmission due to the poorly conducting core materials that support the cable weight. This Al/Ca composite was produced by powder metallurgy and severe plastic deformation by extrusion and swaging. The fine Ca metal powders have been produced by centrifugal atomization with rotating liquid oil quench bath, and a detailed study about the atomization process and powder characteristics has been conducted. The microstructure of Al/Ca composite was characterized by electron microscopy. Microstructure changes at elevated temperature were characterized by thermal analysis and indirect resistivity tests. The strength and electrical conductivity were measured by tensile tests and four-point probe resistivity tests. Predicting the strength and electrical conductivity of the composite was done by micro-mechanics-based analytical modeling. Microstructure evolution was studied by mesoscale-thermodynamics-based phase field modeling and a preliminary atomistic molecular dynamics simulation. The application prospects of this composite was studied by an economic analysis. This study suggests that the Al/Ca (20 vol. %) composite shows promise for use as overhead power transmission cables. Further studies are needed to measure the corrosion resistance, fatigue properties and energized field performance of this composite.

Study of the structure and chemical composition of the protective coating of a fist stage gas turbine blade after regenerative heat treatment

NASA Astrophysics Data System (ADS)

Davidov, D. I.; Kazantseva, N. V.; Vinogradova, N. I.; Ezhov, I. V.

2017-12-01

Investigation of the structure and chemical composition of the protective coating of the first stage IN738 gas turbine blade after standard regenerative heat treatment was done. It was found the degradation of microstructure and chemical composition of both the blade feather and its protective coating. Redistribution of the chemical elements decreasing the corrosion resistance was observed inside the protective coating. Cracks on the boundary between the blade feather and the protective coating were found by scanning electron microscopy. The carbide transformation and sigma phase were found in the structure of the blade feather. Based upon the structural and chemical composition studies, it is concluded that the standard regenerative heat treatment of the IN738 operative gas turbine blade does not provide full structure regeneration.

Control of the electrical resistivity of Ni-Cr wires using low pressure chemical vapor deposition of tin

NASA Astrophysics Data System (ADS)

Kim, Jun-Hyun; Bak, Jeong Geun; Lee, Kangtaek; Kim, Chang-Koo

2018-01-01

Control of the electrical resistivity of Ni-Cr wires is demonstrated using low pressure chemical vapor deposition (LPCVD) of tin on the surface of the wire, after which the effects of the deposition temperature on the structural, morphological, and compositional characteristics of the tin-deposited Ni-Cr wires are investigated. As the deposition temperature is increased, the resistivity of the Ni-Cr wires increases in the temperature range 300-400 °C; then remains nearly constant as the temperature increased to 700 °C. The increase in the resistivity of the Ni-Cr wires is attributed to formation of Ni3Sn2 particulates on the surface of the wire. Compositional analysis shows that the pattern of change in the tin content with the deposition temperature is similar to that of resistivity with temperature, implying that the atomic content of tin on Ni-Cr directly affects the electrical resistivity.

Resistive switching characteristics and mechanisms in silicon oxide memory devices

NASA Astrophysics Data System (ADS)

Chang, Yao-Feng; Fowler, Burt; Chen, Ying-Chen; Zhou, Fei; Wu, Xiaohan; Chen, Yen-Ting; Wang, Yanzhen; Xue, Fei; Lee, Jack C.

2016-05-01

Intrinsic unipolar SiOx-based resistance random access memories (ReRAM) characterization, switching mechanisms, and applications have been investigated. Device structures, material compositions, and electrical characteristics are identified that enable ReRAM cells with high ON/OFF ratio, low static power consumption, low switching power, and high readout-margin using complementary metal-oxide semiconductor transistor (CMOS)-compatible SiOx-based materials. These ideas are combined with the use of horizontal and vertical device structure designs, composition optimization, electrical control, and external factors to help understand resistive switching (RS) mechanisms. Measured temperature effects, pulse response, and carrier transport behaviors lead to compact models of RS mechanisms and energy band diagrams in order to aid the development of computer-aided design for ultralarge-v scale integration. This chapter presents a comprehensive investigation of SiOx-based RS characteristics and mechanisms for the post-CMOS device era.

A Homogenization Approach for Design and Simulation of Blast Resistant Composites

NASA Astrophysics Data System (ADS)

Sheyka, Michael

Structural composites have been used in aerospace and structural engineering due to their high strength to weight ratio. Composite laminates have been successfully and extensively used in blast mitigation. This dissertation examines the use of the homogenization approach to design and simulate blast resistant composites. Three case studies are performed to examine the usefulness of different methods that may be used in designing and optimizing composite plates for blast resistance. The first case study utilizes a single degree of freedom system to simulate the blast and a reliability based approach. The first case study examines homogeneous plates and the optimal stacking sequence and plate thicknesses are determined. The second and third case studies use the homogenization method to calculate the properties of composite unit cell made of two different materials. The methods are integrated with dynamic simulation environments and advanced optimization algorithms. The second case study is 2-D and uses an implicit blast simulation, while the third case study is 3-D and simulates blast using the explicit blast method. Both case studies 2 and 3 rely on multi-objective genetic algorithms for the optimization process. Pareto optimal solutions are determined in case studies 2 and 3. Case study 3 is an integrative method for determining optimal stacking sequence, microstructure and plate thicknesses. The validity of the different methods such as homogenization, reliability, explicit blast modeling and multi-objective genetic algorithms are discussed. Possible extension of the methods to include strain rate effects and parallel computation is also examined.

Structural energy dissipation in extreme loading events using shape memory alloys

NASA Astrophysics Data System (ADS)

Angioni, Stefano L.

It is well known that composite materials have a poor resistance to the damage caused by the impact of foreign objects on their outer surface. There are various methods for improving the impact damage tolerance of composite materials, such as: fibre toughening, matrix toughening, interface toughening, through the thickness reinforcements and selective interlayers and hybrids. Hybrid composites with improved impact resistance would be particularly useful in military and commercial civil applications. Hybridizing composites using shape memory alloys (SMAs) is one solution since SMA materials can absorb the energy of impact through superelastic deformation or recovery stress reducing the effects of the impact on the composite structure. The SMA material may be embedded in the hybrid composites (SMAHC) in many different forms and also the characteristics of the fibre reinforcements may vary, such as SMA wires in unidirectional laminates or SMA foils in unidirectional laminates only to cite two examples. Recently SMA fibres have been embedded in 2-D woven composites. As part of this work, the existing theoretical models for woven composites have been extended to the case of woven SMAHC using a multiscale methodology in order to predict the mechanical properties and failure behaviour of SMAHC plates. Also several parts of the model have been coded in MATLAB and validated against results extracted from the literature, showing good correlation..

Damage Progression in Bolted Composites

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C.; Gotsis, Pascal K.

1998-01-01

Structural durability, damage tolerance, and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions.

Damage Progression in Bolted Composites

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos; Gotsis, Pascal K.

1998-01-01

Structural durability,damage tolerance,and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions.

Composite materials for rail transit systems

NASA Technical Reports Server (NTRS)

Griffin, O. Hayden, Jr.; Guerdal, Zafer; Herakovich, Carl T.

1987-01-01

The potential is explored for using composite materials in urban mass transit systems. The emphasis was to identify specific advantages of composite materials in order to determine their actual and potential usage for carbody and guideway structure applications. The literature was reviewed, contacts were made with major domestic system operators, designers, and builders, and an analysis was made of potential composite application to railcar construction. Composites were found to be in use throughout the transit industry, usually in secondary or auxiliary applications such as car interior and nonstructural exterior panels. More recently, considerable activity has been initiated in the area of using composites in the load bearing elements of civil engineering structures such as highway bridges. It is believed that new and improved manufacturing refinements in pultrusion and filament winding will permit the production of beam sections which can be used in guideway structures. The inherent corrosion resistance and low maintenance characteristics of composites should result in lowered maintenance costs over a prolonged life of the structure.

Advances in joining newer structural materials; Proceedings of the International Conference, Montreal, Canada, July 23-25, 1990

NASA Astrophysics Data System (ADS)

The present conference on advances in joining novel structural materials encompasses such material types as ceramics, plastics and composites, and new metallic materials. Specific issues addressed include the use of conductor electric explosion to join ceramics, the effects of brazing temperature on joint properties of SiC-fiber-reinforced Al-alloy-matrix composites, the in situ structure control of composite materials, and the weldability of polymeric materials that are heterogeneous as to chemical nature from the standpoint of morphology. Also addressed are the joining of the Al-Li alloy 8090, diffusion bonding of a creep-resistant Fe-ODS alloy, the adhesive bonding of zinc-coated steel sheets, welds in thermoplastic composite materials, and hot-melt joints for carbon-fiber-reinforced composites.

Monitoring Damage Accumulation in Ceramic Matrix Composites Using Electrical Resistivity

NASA Technical Reports Server (NTRS)

Smith, Craig E.; Morscher, Gregory N.; Xia, Zhenhai H.

2008-01-01

The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection and accurate life prediction for high-temperature ceramic matrix composites. Woven silicon carbide fiber-reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMC) possess unique properties such as high thermal conductivity, excellent creep resistance, improved toughness, and good environmental stability (oxidation resistance), making them particularly suitable for hot structure applications. In specific, CMCs could be applied to hot section components of gas turbines [1], aerojet engines [2], thermal protection systems [3], and hot control surfaces [4]. The benefits of implementing these materials include reduced cooling air requirements, lower weight, simpler component design, longer service life, and higher thrust [5]. It has been identified in NASA High Speed Research (HSR) program that the SiC/SiC CMC has the most promise for high temperature, high oxidation applications [6]. One of the critical issues in the successful application of CMCs is on-board or insitu assessment of the damage state and an accurate prediction of the remaining service life of a particular component. This is of great concern, since most CMC components envisioned for aerospace applications will be exposed to harsh environments and play a key role in the vehicle s safety. On-line health monitoring can enable prediction of remaining life; thus resulting in improved safety and reliability of structural components. Monitoring can also allow for appropriate corrections to be made in real time, therefore leading to the prevention of catastrophic failures. Most conventional nondestructive evaluation (NDE) techniques such as ultrasonic C-scan, x-ray, thermography, and eddy current are limited since they require structural components of complex geometry to be taken out of service for a substantial length of time for post-damage inspection and assessment. Furthermore, the typical NDE techniques are useful for identifying large interlaminar flaws, but insensitive to CMC materials flaws developed perpendicular to the surface under tensile creep conditions. There are techniques such as piezoelectric sensor [7,8], and optical fiber [9,10] that could be used for on-line health monitoring of CMC structures. However, these systems involve attaching an external sensor or putting special fibers in CMC composites, which would be problematic at high temperature applications.

Structural Technology Evaluation and Analysis Program (STEAP). Delivery Order 0045: Progressive Failure Analysis of Translaminar Reinforced Composite Structures

DTIC Science & Technology

2011-11-01

Approved for public release; distribution unlimited. See additional restrictions described on inside pages STINFO COPY AIR...pin density, diameter and length are some of the parameters related to the effectiveness of z-pins for increasing the delamination resistance...has received considerable attention in recent years due to increased use of composite materials in aerospace and related industries. Mainly in the

Fluid Structure Interaction Effect on Sandwich Composite Structures

DTIC Science & Technology

2011-09-01

far back as ancient Egyptian times in the use of straw and bricks, or more recently in the last century with the use of steel rebar in concrete ...construction of sandwich composites; however, this particular material was selected for its uniform pattern and translucent qualities after it is wetted out...excellent fire retardant and corrosion resistant qualities making it a natural selection for shipboard applications. The same translucent qualities

Monitoring in situ in real time of resin infusion for thermoset composite structures

NASA Astrophysics Data System (ADS)

Faci, A.; Wang, P.; Cochrane, C.; Koncar, V.

2017-10-01

The presented work investigates changes in electrical resistance of embedded sensory yarns as a method to monitor the resin flow front position and curing degree of resin during manufacturing of composite structures by vacuum infusion technology. The sensor concept is based on Piezo-resistive sensors integrated to the flax fabric, having almost identical propriety and dimensions as the flax threads used for the production of reinforcements. In the first time sensors have been characterized and first measures of the resin infusion have been realized in order to demonstrate the feasibility of the proposed approach. Then, the measures in real time were realized with fibrous sensors added to the flax fabric (green composites) to monitor the flow front of resin. A large amount of data recorded, filtered, examined, analysed and processed in order to understand and to optimize the infusion and polymerization process.

Aerogel Hybrid Composite Materials: Designs and Testing for Multifunctional Applications

NASA Technical Reports Server (NTRS)

Williams, Martha K.; Fesmire, James E.

2016-01-01

This webinar will introduce the broad spectrum of aerogel composites and their diverse performance properties such as reduced heat transfer to energy storage, and expands specifically on the aerogel/fiber laminate systems and testing methodologies. The multi-functional laminate composite system, AeroFiber, and its construction is designed by varying the type of fiber (e.g. polyester, carbon, Kevlar®, Spectra® or Innegral(TradeMark) and combinations thereof), the aerogel panel type and thickness, and overall layup configuration. The combination and design of materials may be customized and tailored to achieve a range of desired properties in the resulting laminate system. Multi-functional properties include structural strength, impact resistance, reduction in heat transfer, increased fire resistance, mechanical energy absorption, and acoustic energy dampening. Applications include aerospace, aircraft, automotive, boating, building and construction, lightweight portable structures, liquefied natural gas, cryogenics, transportation and energy, sporting equipment, and military protective gear industries.

Study on the Impact Resistance of Bionic Layered Composite of TiC-TiB2/Al from Al-Ti-B4C System

PubMed Central

Zhao, Qian; Liang, Yunhong; Zhang, Zhihui; Li, Xiujuan; Ren, Luquan

2016-01-01

Mechanical property and impact resistance mechanism of bionic layered composite was investigated. Due to light weight and high strength property, white clam shell was chosen as bionic model for design of bionic layered composite. The intercoupling model between hard layer and soft layer was identical to the layered microstructure and hardness tendency of the white clam shell, which connected the bionic design and fabrication. TiC-TiB2 reinforced Al matrix composites fabricated from Al-Ti-B4C system with 40 wt. %, 50 wt. % and 30 wt. % Al contents were treated as an outer layer, middle layer and inner layer in hard layers. Pure Al matrix was regarded as a soft layer. Compared with traditional homogenous Al-Ti-B4C composite, bionic layered composite exhibited high mechanical properties including flexural strength, fracture toughness, compressive strength and impact toughness. The intercoupling effect of layered structure and combination model of hard and soft played a key role in high impact resistance of the bionic layered composite, proving the feasibility and practicability of the bionic model of a white clam shell. PMID:28773827

Highly antifouling and antibacterial performance of poly (vinylidene fluoride) ultrafiltration membranes blending with copper oxide and graphene oxide nanofillers for effective wastewater treatment.

PubMed

Zhao, Chuanqi; Lv, Jinling; Xu, Xiaochen; Zhang, Guoquan; Yang, Yuesuo; Yang, Fenglin

2017-11-01

Innovation and effective wastewater treatment technology is still in great demand given the emerging contaminants frequently spotted from the aqueous environment. By blending with poly (vinylidene fluoride) (PVDF), the strong hydrophilic graphene oxide (GO) and antibacterial copper oxide (Cu x O) were used as nanofillers to develop the novel, highly antifouling composite membranes via phase inversion process in our latest work. The existence and dispersion of GO and Cu x O posed a significant role on morphologies, structures, surface composition and hydrophilicity of the developed composite membranes, confirmed by SEM, TEM, FTIR and XPS in depth characterization. The SEM images showed that the modified membranes presented a lower resistant structure with developed finger-like macrovoids and thin-walled even interconnected sponge-like pores after adding nanofillers, much encouraging membrane permeation. The XPS results revealed that Cu x O contained Cu 2 O and CuO in the developed membrane and the Cu 2 O nanoparticles were dominant accounting for about 79.3%; thus the modified membrane specifically exhibited an efficient antibacterial capacity. Due to the hydrophilic and bactericidal membrane surface, the composite membranes demonstrated an excellent antifouling performance, including higher flux recovery rate, more resistant against accumulated contaminants and lower filtration resistance, especially lower irreversible resistance. The antifouling property, especially anti-irreversible fouling, was significantly improved, showing a significant engineering potential. Copyright © 2017 Elsevier Inc. All rights reserved.

All ceramic structure for molten carbonate fuel cell

DOEpatents

Smith, James L.; Kucera, Eugenia H.

1992-01-01

An all-ceramic molten carbonate fuel cell having a composition formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The structure includes an anode and cathode separated by an electronically conductive interconnect. The electrodes and interconnect are compositions ceramic materials. Various combinations of ceramic compositions for the anode, cathode and interconnect are disclosed. The fuel cell exhibits stability in the fuel gas and oxidizing environments. It presents reduced sealing and expansion problems in fabrication and has improved long-term corrosion resistance.

Testing of Composite Fan Vanes With Erosion-Resistant Coating Accelerated

NASA Technical Reports Server (NTRS)

Bowman, Cheryl L.; Sutter, James K.; Otten, Kim D.; Samorezov, Sergey; Perusek, Gail P.

2004-01-01

The high-cycle fatigue of composite stator vanes provided an accelerated life-state prior to insertion in a test stand engine. The accelerated testing was performed in the Structural Dynamics Laboratory at the NASA Glenn Research Center under the guidance of Structural Mechanics and Dynamics Branch personnel. Previous research on fixturing and test procedures developed at Glenn determined that engine vibratory conditions could be simulated for polymer matrix composite vanes by using the excitation of a combined slip table and electrodynamic shaker in Glenn's Structural Dynamics Laboratory. Bench-top testing gave researchers the confidence to test the coated vanes in a full-scale engine test.

Numerical simulation of high-temperature thermal contact resistance and its reduction mechanism.

PubMed

Liu, Donghuan; Zhang, Jing

2018-01-01

High-temperature thermal contact resistance (TCR) plays an important role in heat-pipe-cooled thermal protection structures due to the existence of contact interface between the embedded heat pipe and the heat resistive structure, and the reduction mechanism of thermal contact resistance is of special interests in the design of such structures. The present paper proposed a finite element model of the high-temperature thermal contact resistance based on the multi-point contact model with the consideration of temperature-dependent material properties, heat radiation through the cavities at the interface and the effect of thermal interface material (TIM), and the geometry parameters of the finite element model are determined by simple surface roughness test and experimental data fitting. The experimental results of high-temperature thermal contact resistance between superalloy GH600 and C/C composite material are employed to validate the present finite element model. The effect of the crucial parameters on the thermal contact resistance with and without TIM are also investigated with the proposed finite element model.

Numerical simulation of high-temperature thermal contact resistance and its reduction mechanism

PubMed Central

Zhang, Jing

2018-01-01

High-temperature thermal contact resistance (TCR) plays an important role in heat-pipe-cooled thermal protection structures due to the existence of contact interface between the embedded heat pipe and the heat resistive structure, and the reduction mechanism of thermal contact resistance is of special interests in the design of such structures. The present paper proposed a finite element model of the high-temperature thermal contact resistance based on the multi-point contact model with the consideration of temperature-dependent material properties, heat radiation through the cavities at the interface and the effect of thermal interface material (TIM), and the geometry parameters of the finite element model are determined by simple surface roughness test and experimental data fitting. The experimental results of high-temperature thermal contact resistance between superalloy GH600 and C/C composite material are employed to validate the present finite element model. The effect of the crucial parameters on the thermal contact resistance with and without TIM are also investigated with the proposed finite element model. PMID:29547651

Effect of active-layer composition and structure on device performance of coplanar top-gate amorphous oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Yue, Lan; Meng, Fanxin; Chen, Jiarong

2018-01-01

The thin-film transistors (TFTs) with amorphous aluminum-indium-zinc-oxide (a-AIZO) active layer were prepared by dip coating method. The dependence of properties of TFTs on the active-layer composition and structure was investigated. The results indicate that Al atoms acted as a carrier suppressor in IZO films. Meanwhile, it was found that the on/off current ratio (I on/off) of TFT was improved by embedding a high-resistivity AIZO layer between the low-resistivity AIZO layer and gate insulator. The improvement in I on/off was attributed to the decrease in off-state current of double-active-layer TFT due to an increase in the active-layer resistance and the contact resistance between active layer and source/drain electrode. Moreover, on-state current and threshold voltage (V th) can be mainly controlled through thickness and Al content of the low-resistivity AIZO layer. In addition, the saturation mobility (μ sat) of TFTs was improved with reducing the size of channel width or/and length, which was attributed to the decrease in trap states in the semiconductor and at the semiconductor/gate-insulator interface with the smaller channel width or/and shorter channel length. Thus, we can demonstrate excellent TFTs via the design of active-layer composition and structure by utilizing a low cost solution-processed method. The resulting TFT, operating in enhancement mode, has a high μ sat of 14.16 cm2 V-1 s-1, a small SS of 0.40 V/decade, a close-to-zero V th of 0.50 V, and I on/off of more than 105.

UV Grafting Modification of Polyethylene Separator for Liion Battery

NASA Astrophysics Data System (ADS)

Lv, Xiaoyuan; Li, Hua; Zhang, Zhiqiang; Chang, Hiunam; Jiang, Li; Liu, Hezhou

Polyethylene (PE) separator was modified by UV grafting methyl acrylate (MA) and nano-SiO2 composite layer. The structure of functional group and morphology of the separator were analyzed by Fourier transform infrared spectrum (FT-IR) and scanning electron microscope (SEM). The wetting behavior and the heat resistance of the separator were also investigated by contact angle test and thermal shrinkage test respectively. The results show that MA/nano-SiO2 composite layer is successfully grafted onto the PE separator, and the addition of the DI water and butanol can make the nano-SiO2 dispersed better and lead to a microporous structure of the grafting layer. The grafted separator has a better wettability and heat resistance than the pristine one.

On the role of weak interface in crack blunting process in nanoscale layered composites

NASA Astrophysics Data System (ADS)

Li, Yi; Zhou, Qing; Zhang, Shuang; Huang, Ping; Xu, Kewei; Wang, Fei; Lu, Tianjian

2018-03-01

Heterointerface in a nanoscale metallic layered composite could improve its crack resistance. However, the influence of metallic interface structures on crack propagation has not been well understood at atomic scale. By using the method of molecular dynamics (MD) simulation, the crack propagation behavior in Cu-Nb bilayer is compared with that in Cu-Ni bilayer. We find that the weak Cu-Nb interface plays an important role in hindering crack propagation in two ways: (i) dislocation nucleation at the interface releases stress concentration for the crack to propagate; (ii) the easily sheared weak incoherent interface blunts the crack tip. The results are helpful for understanding the interface structure dependent crack resistance of nanoscale bicrystal interfaces.

Proceedings of the Annual Mechanics of Composites Review (6th),

DTIC Science & Technology

1981-02-01

containing and resisting damage in compression-loaded composite structural components. 176( CONTRACTS INCREMENTAL ANALYSIS OF IMPACT DAMAGE NASI -15888 79...EVALUATION OF THE DURABILITY AND DAMAGE TOLERANCE OF CTOL COMPOS- ITE STRUCTURES NASI -15107 77 October 12 - 80 October 11 Project Engineer: Edward P...DEVELOPMENT OF AN ORTHOTROPIC HOLE ELEMENT NASI -15890 79 July 9 - 80 September 24 Project Engineer: Dr. John H. Crews, Jr. Mail Stop 18BE NASA Langley

Low density bismaleimide-carbon microballoon composites. [aircraft and submarine compartment safety

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Parker, J. A. (Inventor)

1978-01-01

A process is described for constructing for a composite laminate structure which exhibits a high resistance to heat and flame provides safer interior structures for aircraft and submarine compartments. Composite laminate structures are prepared by the bismaleimide resin preimpregnation of a fiberglass cloth to form a face sheet which is bonded with a bismaleimide hot melt adhesive to a porous core structure selected from the group consisting of polyamide paper and bismaleimide-glass fabric which is filled with carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic micro-balloons in the presence of nitrogen. A slurry of the carbon microballoons is prepared to fill the porous core structure. The porous core structure and face sheet are bonded to provide panel structures exhibiting increased mechanical capacities and lower oxygen limit values and smoke density values.

Passivation Characteristics of Alloy Corrosion-Resistant Steel Cr10Mo1 in Simulating Concrete Pore Solutions: Combination Effects of pH and Chloride

PubMed Central

Ai, Zhiyong; Sun, Wei; Jiang, Jinyang; Song, Dan; Ma, Han; Zhang, Jianchun; Wang, Danqian

2016-01-01

The electrochemical behaviour for passivation of new alloy corrosion-resistant steel Cr10Mo1 immersed in alkaline solutions with different pH values (13.3, 12.0, 10.5, and 9.0) and chloride contents (0.2 M and 1.0 M), was investigated by various electrochemical techniques: linear polarization resistance, electrochemical impedance spectroscopy and capacitance measurements. The chemical composition and structure of passive films were determined by XPS. The morphological features and surface composition of the immersed steel were evaluated by SEM together with EDS chemical analysis. The results evidence that pH plays an important role in the passivation of the corrosion-resistant steel and the effect is highly dependent upon the chloride contents. In solutions with low chloride (0.2 M), the corrosion-resistant steel has notably enhanced passivity with pH falling from 13.3 to 9.0, but does conversely when in presence of high chloride (1.0 M). The passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer enriched in Fe oxides and hydroxides, and an inner layer, rich in Cr species. The film composition varies with pH values and chloride contents. As the pH drops, more Cr oxides are enriched in the film while Fe oxides gradually decompose. Increasing chloride promotes Cr oxides and Fe oxides to transform into their hydroxides with little protection, and this is more significant at lower pH (10.5 and 9.0). These changes annotate passivation characteristics of the corrosion-resistant steel in the solutions of different electrolyte. PMID:28773867

Passivation Characteristics of Alloy Corrosion-Resistant Steel Cr10Mo1 in Simulating Concrete Pore Solutions: Combination Effects of pH and Chloride.

PubMed

Ai, Zhiyong; Sun, Wei; Jiang, Jinyang; Song, Dan; Ma, Han; Zhang, Jianchun; Wang, Danqian

2016-09-01

The electrochemical behaviour for passivation of new alloy corrosion-resistant steel Cr10Mo1 immersed in alkaline solutions with different pH values (13.3, 12.0, 10.5, and 9.0) and chloride contents (0.2 M and 1.0 M), was investigated by various electrochemical techniques: linear polarization resistance, electrochemical impedance spectroscopy and capacitance measurements. The chemical composition and structure of passive films were determined by XPS. The morphological features and surface composition of the immersed steel were evaluated by SEM together with EDS chemical analysis. The results evidence that pH plays an important role in the passivation of the corrosion-resistant steel and the effect is highly dependent upon the chloride contents. In solutions with low chloride (0.2 M), the corrosion-resistant steel has notably enhanced passivity with pH falling from 13.3 to 9.0, but does conversely when in presence of high chloride (1.0 M). The passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer enriched in Fe oxides and hydroxides, and an inner layer, rich in Cr species. The film composition varies with pH values and chloride contents. As the pH drops, more Cr oxides are enriched in the film while Fe oxides gradually decompose. Increasing chloride promotes Cr oxides and Fe oxides to transform into their hydroxides with little protection, and this is more significant at lower pH (10.5 and 9.0). These changes annotate passivation characteristics of the corrosion-resistant steel in the solutions of different electrolyte.

Exposure of Trypanosoma brucei to an N-acetylglucosamine-Binding Lectin Induces VSG Switching and Glycosylation Defects Resulting in Reduced Infectivity

PubMed Central

Castillo-Acosta, Víctor M.; Ruiz-Pérez, Luis M.; Van Damme, Els J. M.; Balzarini, Jan; González-Pacanowska, Dolores

2015-01-01

Trypanosoma brucei variant surface glycoproteins (VSG) are glycosylated by both paucimannose and oligomannose structures which are involved in the formation of a protective barrier against the immune system. Here, we report that the stinging nettle lectin (UDA), with predominant N-acetylglucosamine-binding specificity, interacts with glycosylated VSGs and kills parasites by provoking defects in endocytosis together with impaired cytokinesis. Prolonged exposure to UDA induced parasite resistance based on a diminished capacity to bind the lectin due to an enrichment of biantennary paucimannose and a reduction of triantennary oligomannose structures. Two molecular mechanisms involved in resistance were identified: VSG switching and modifications in N-glycan composition. Glycosylation defects were correlated with the down-regulation of the TbSTT3A and/or TbSTT3B genes (coding for oligosaccharyltransferases A and B, respectively) responsible for glycan specificity. Furthermore, UDA-resistant trypanosomes exhibited severely impaired infectivity indicating that the resistant phenotype entails a substantial fitness cost. The results obtained further support the modification of surface glycan composition resulting from down-regulation of the genes coding for oligosaccharyltransferases as a general resistance mechanism in response to prolonged exposure to carbohydrate-binding agents. PMID:25746926

Development of an embedded thin-film strain-gauge-based SHM network into 3D-woven composite structure for wind turbine blades

NASA Astrophysics Data System (ADS)

Zhao, Dongning; Rasool, Shafqat; Forde, Micheal; Weafer, Bryan; Archer, Edward; McIlhagger, Alistair; McLaughlin, James

2017-04-01

Recently, there has been increasing demand in developing low-cost, effective structure health monitoring system to be embedded into 3D-woven composite wind turbine blades to determine structural integrity and presence of defects. With measuring the strain and temperature inside composites at both in-situ blade resin curing and in-service stages, we are developing a novel scheme to embed a resistive-strain-based thin-metal-film sensory into the blade spar-cap that is made of composite laminates to determine structural integrity and presence of defects. Thus, with fiberglass, epoxy, and a thinmetal- film sensing element, a three-part, low-cost, smart composite laminate is developed. Embedded strain sensory inside composite laminate prototype survived after laminate curing process. The internal strain reading from embedded strain sensor under three-point-bending test standard is comparable. It proves that our proposed method will provide another SHM alternative to reduce sensing costs during the renewable green energy generation.

Flexible strain sensor based on carbon nanotube rubber composites

NASA Astrophysics Data System (ADS)

Kim, Jin-Ho; Kim, Young-Ju; Baek, Woon Kyung; Lim, Kwon Taek; Kang, Inpil

2010-04-01

Electrically conducting rubber composites (CRC) with carbon nanotubes (CNTs) filler have received much attention as potential materials for sensors. In this work, Ethylene propylene diene M-class rubber (EPDM)/CNT composites as a novel nano sensory material were prepared to develop flexible strain sensors that can measure large deformation of flexible structures. The EPDM/CNT composites were prepared by using a Brabender mixer with multi-walled CNTs and organo-clay. A strain sensor made of EPDM/CNT composite was attached to the surface of a flexible beam and change of resistance of the strain sensor was measured with respect to the beam deflection. Resistance of the sensor was change quite linearly under the bending and compressive large beam deflection. Upon external forces, CRC deformation takes place with the micro scale change of inter-electrical condition in rubber matrix due to the change of contact resistance, and CRC reveals macro scale piezoresistivity. It is anticipated that the CNT/EPDM fibrous strain sensor can be eligible to develop a biomimetic artificial neuron that can continuously sense deformation, pressure and shear force.

Cavitation resistance of surface composition "Steel-Ni-TiNi-TiNiZr-cBNCo", formed by High-Velocity Oxygen-Fuel spraying

NASA Astrophysics Data System (ADS)

Blednova, Zh. M.; Dmitrenko, D. V.; Balaev, E. U. O.

2018-01-01

The object of the study is a multilayered surface composition "Steel - a Multicomponent material with Shape Memory Effect - a wear-resistant layer" under conditions of cavitation effects in sea water. Multicomponent TiNi-based coatings with addition of alloying elements such as Zr in an amount up to 10% mass, allow to create a composite material with a gradient of properties at the interface of layers, which gives new properties to coatings and improves their performance significantly. The use of materials with shape memory effect (SME) as surface layers or in the composition of surface layered compositions allows to provide an effective reaction of materials to the influence of external factors and adaptation to external influences. The surface composite layer cBN-10%Co has high hardness and strength, which ensures its resistance to shock cyclic influences of collapsing caverns. The increased roughness of the surface of a solid surface composite in the form of strong columnar structures ensures the crushing of vacuum voids, redistributing their effect on the entire surface, and not concentrating them in certain zones. In addition, the gradient structure of the multilayer composite coating TiNi-Ti33Ni49Zr18-cBN-10%Co Co makes it possible to create conditions for the relaxation of stresses created by the variable impact load of cavitation caverns and the manifestation of compensating internal forces due to thermo-elastic martensitic transformations of SME materials. The cavitation resistance of the coating TiNi-Ti33Ni49Zr18-cBN-10%Co according to the criterion of mass wear is 15-20 times higher than that of the base material without coating and 10-12 times higher than that of the TiNi-TiNiZr coating. The proposed architecture of the multifunctional gradient composition, "steel-Ni-TiNi- Ti33Ni49Zr18-cBN-10%Co", each layer of which has its functional purpose, allows to increase the service life of parts operating under conditions of cavitation-fatigue loading in corrosive environments.

Optimized adhesives for strong, lightweight, damage-resistant, nanocomposite materials: new insights from natural materials

NASA Astrophysics Data System (ADS)

Hansma, P. K.; Turner, P. J.; Ruoff, R. S.

2007-01-01

From our investigations of natural composite materials such as abalone shell and bone we have learned the following. (1) Nature is frugal with resources: it uses just a few per cent glue, by weight, to glue together composite materials. (2) Nature does not avoid voids. (3) Nature makes optimized glues with sacrificial bonds and hidden length. We discuss how optimized adhesives combined with high specific stiffness/strength structures such as carbon nanotubes or graphene sheets could yield remarkably strong, lightweight, and damage-resistant materials.

Structural wood panels with improved fire resistance

NASA Technical Reports Server (NTRS)

Sawko, P. M. (Inventor)

1980-01-01

Structural wood paneling or other molded wood compositions consisting of finely divided wood chips, flour, or strands are bound together and hot pressed with a modified novolac resin which is the cured product of a prepolymer made from an aralkyl ether or halide with a phenol and a hardening agent such as hexamethylene tetramine. The fire resistance of these articles is further improved by incorporating in the binder certain inorganic fillers, especially a mixture of ammonium oxalate and ammonium phosphate.

MoSi2-Base Hybrid Composite Passed Engine Test

NASA Technical Reports Server (NTRS)

Keith, Theo G., Jr.; Hebsur, Mohan

1998-01-01

The intermetallics compound molybdenum disilicide (MoSi2) is an attractive high-temperature structural material for advanced engine applications. It has excellent oxidation resistance, a high melting point, relatively low density, and high thermal conductivity, and it is easily machined. Past research'at the NASA Lewis Research Center has resulted in the development of a hybrid composite consisting of a MoSi2 matrix reinforced with silicon nitride (Si3N4) Particulate and silicon carbide (SiC) fibers. This composite has demonstrated attractive strength, toughness, thermal fatigue, and oxidation resistance, including resistance to "pest" oxidation. These properties attracted the interest of the Office of Naval Research and Pratt & Whitney, and a joint NASA/Navy/Pratt & Whitney effort was developed to continue to mature the MoSi2 Composite technology. A turbine blade outer air seal, which was part of the Integrated High Performance Turbine Engine Technology (IHPTET) program, was chosen as a first component on which to focus. The first tasks of the materials development effort were to develop improved processing methods to reduce costs and to use fine-diameter fibers that enable the manufacturing of complex shapes. Tape-casting methods were developed to fully infiltrate the fine SiC fibers with matrix powders. The resulting composites were hot pressed to 100-percent density. Composites with cross-plied fiber architectures with 30 vol. % hi-nicalon SiC fibers and 30 vol. % nitride particles are now made routinely and demonstrate a good balance of properties. The next task entailed the measurement of a wide variety of mechanical properties to confirm the suitability of this composite in engines. In particular, participants in this effort demonstrated that composites made with Hi-Nicalon fibers had strength and toughness properties equal to or better than those of the composites made with the large-diameter fibers that had been used previously. Another critically important property measured was impact resistance. Aircraft engine components require sufficient toughness to resist manufacturing defects, assembly damage, stress concentrations at notches, and foreign object damage. Engine company designers indicated that impact resistance would have to be measured before they would seriously consider these types of composites. The Charpy V-notch test was chosen to assess impact resistance, and both monolithic and composite versions Of MOSi2 were tested from -300 to 1400 C. The results (see the following graphs) show that nitride-particulate-reinforced MoSi2 exhibited impact resistance higher than that of many monolithic ceramics and intermetallics, and that the fiber-reinforced composites had even higher values, approaching that of cast superalloys.

Characterization and Properties of Micro-arc Composite Ceramic Coatings on Magnesium Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Long; Jiang, Bailing; Ge, Yanfeng

2013-05-21

Magnesium alloys are of growing interest for many industrial applications due to their favorable strength-to-weight ratio and excellent cast ability. However, one of the limiting factors in the use of magnesium on production vehicles is its poor corrosion resistance. Micro-arc Composite Ceramic (MCC) coatings on AZ91D magnesium alloys were prepared in combination with Micro-arc Oxidation (MAO) and electrophoresis technologies. The microstructure, corrosion resistance, abrasion resistance, stone impact resistance, thermal shock resistance and adhesion of MCC coating were studied, respectively. The surface and cross-section morphologies of MAO and MCC coating showed that the outer organic coating filled the holes on themore » surface of the MAO coating. It acted as a shelter on the MAO coating surface when the MCC coatings were exposed to corrosive environments. The corrosion resistance of the MCC coating was characterized by a copper-accelerated acetic acid salt spray test. The testing results showed that the creep back from scribe lines was less than 1mm and completely fit the evaluation standard. The composite structure of the MCC coating vastly improved the corrosion resistance of Mg alloys. According to testing standards, the resistance to abrasion, stone impact resistance, thermal shock resistance and adhesion of MCC coatings completely met the evaluation standard requirements. The MCC coated AZ91D magnesium alloys possessed excellent properties; this is a promising corrosion and wear resistance surface treatment technology on magnesium alloys for production vehicles.« less

Corrosion resistance and adhesion strength of a spin-assisted layer-by-layer assembled coating on AZ31 magnesium alloy

NASA Astrophysics Data System (ADS)

Zhao, Yan-Bin; Liu, Han-Peng; Li, Chang-Yang; Chen, Yong; Li, Shuo-Qi; Zeng, Rong-Chang; Wang, Zhen-Lin

2018-03-01

A polyvinylpyrrolidone (PVP)/polyacrylic acid (PAA) layer-by-layer (LbL) assembled composite coating with a multilayer structure for the corrosion protection of AZ31 magnesium alloy was prepared by a novel spin-casting method. The microstructure and composition of this coating were investigated by means of SEM, XRD and FT-IR measurements. Moreover, electrochemical, immersion and scratch tests in vitro were performed to measure the corrosion performance and the adhesion strength. These results indicated that the (PVP/PAA)10 composite coating with defect-free, dense and uniform morphologies could be successfully deposited on the surface of magnesium alloy. The coating had excellent corrosion resistance and adhesion strength.

Impact Behavior of Composite Fan Blade Leading Edge Subcomponent with Thermoplastic Polyurethane Interleave

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Roberts, Gary D.; Kohlman, Lee W.; Heimann, Paula J.; Pereira, J. Michael; Ruggeri, Charles R.; Martin, Richard E.; McCorkle, Linda S.

2015-01-01

Impact damage tolerance and damage resistance is a critical metric for application of polymer matrix composites where failure caused by impact damage could compromise structural performance and safety. As a result, several materials and/or design approaches to improve impact damage tolerance have been investigated over the past several decades. Many composite toughening methodologies impart a trade-off between increased fracture toughness and compromised in-plane strength and modulus. In large part, mechanical tests to evaluate composite damage tolerance include static methods such as Mode I, Mode II, and mixed mode failures. However, ballistic impact damage resistance does not always correlate with static properties. The intent of this paper is to evaluate the influence of a thermoplastic polyurethane veil interleave on the static and dynamic performance of composite test articles. Static coupon tests included tension, compression, double cantilever beam, and end notch flexure. Measurement of the resistance to ballistic impact damage were made to evaluate the composites response to high speed impact. The interlayer material showed a decrease of in-plane performance with only a moderate improvement to Mode I and Mode II fracture toughness. However, significant benefit to impact damage tolerance was observed through ballistic tests.

Viscoelastic processing and characterization of high-performance polymeric composite systems

NASA Astrophysics Data System (ADS)

Buehler, Frederic Ulysse

2000-10-01

Fiber reinforced composites, a combination of reinforcing fiber and resin matrix, offer many advantages over traditional materials, and have therefore found wide application in the aerospace and sporting goods industry. Among the advantages that composite materials offer, the most often cited are weight saving, high modulus, high strength-to-weight ratio, corrosion resistance, and fatigue resistance. As much as their attributes are desirable, composites are difficult to process due to their heterogeneous, anisotropic, and viscoelastic nature. It is therefore not surprising that the interrelationship between structure, property, and process is not fully understood. Consequently, the major purpose of this research work was to investigate this interrelationship, and ways to scale it to utilization. First, four prepreg materials, which performed differently in the manufacturing of composite parts, but were supposedly identical, were characterized. The property variations that were found among these prepregs in terms of tack and frictional resistance assessed the need for improved understanding of the prepregging process. Therefore, the influence of the processing parameters on final prepreg quality were investigated, and led to the definition of more adequate process descriptors. Additionally, one of the characterization techniques used in this work, temperature modulated differential scanning calorimetry, was examined in depth with the development of a mathematical model. This model, which enabled the exploration of the relationship between user parameters, sample thermophysical properties, and final results, was then compared to literature data. Collectively, this work explored and identified the key connectors between process, structure, and property as they relate to the manufacturing, design, and performance of composite materials.

Lightning Strike Induced Damage Mechanisms of Carbon Fiber Composites

NASA Astrophysics Data System (ADS)

Kawakami, Hirohide

Composite materials have a wide application in aerospace, automotive, and other transportation industries, because of the superior structural and weight performances. Since carbon fiber reinforced polymer composites possess a much lower electrical conductivity as compared to traditional metallic materials utilized for aircraft structures, serious concern about damage resistance/tolerance against lightning has been rising. Main task of this study is to clarify the lightning damage mechanism of carbon fiber reinforced epoxy polymer composites to help further development of lightning strike protection. The research on lightning damage to carbon fiber reinforced polymer composites is quite challenging, and there has been little study available until now. In order to tackle this issue, building block approach was employed. The research was started with the development of supporting technologies such as a current impulse generator to simulate a lightning strike in a laboratory. Then, fundamental electrical properties and fracture behavior of CFRPs exposed to high and low level current impulse were investigated using simple coupon specimens, followed by extensive parametric investigations in terms of different prepreg materials frequently used in aerospace industry, various stacking sequences, different lightning intensity, and lightning current waveforms. It revealed that the thermal resistance capability of polymer matrix was one of the most influential parameters on lightning damage resistance of CFRPs. Based on the experimental findings, the semi-empirical analysis model for predicting the extent of lightning damage was established. The model was fitted through experimental data to determine empirical parameters and, then, showed a good capability to provide reliable predictions for other test conditions and materials. Finally, structural element level lightning tests were performed to explore more practical situations. Specifically, filled-hole CFRP plates and patch-repaired CFRP plates were selected as structural elements likely to be susceptible to lightning event. This study forms a solid foundation for the understanding of lightning damage mechanism of CFRPs, and become an important first step toward building a practical damage prediction tool of lighting event.

Monitoring of Structural Integrity of Composite Structures by Embedded Optical Fiber Sensors

NASA Technical Reports Server (NTRS)

Osei, Albert J.

2002-01-01

Real time monitoring of the mechanical integrity and stresses on key aerospace composite structures like aircraft wings, walls of pressure vessels and fuel tanks or any other structurally extended components and panels as in space telescopes is very important to NASA. Future military and commercial aircraft as well as NASA space systems such as Space Based Radar and International Space Station will incorporate a monitoring system to sense any degradation to the structure. In the extreme flight conditions of an aerospace vehicle it might be desirable to measure the strain every ten centimeters and thus fully map out the strain field of a composite component. A series of missions and vehicle health management requirements call for these measurements. At the moment thousands of people support a few vehicle launches per year. This number can be significantly reduced by implementing intelligent vehicles with integral nervous systems (smart structures). This would require maintenance to be performed only as needed. Military and commercial aircrafts have an equally compelling case. Maintenance yearly costs are currently reaching astronomical heights. Monitoring techniques are therefore required that allow for maintenance to be performed only when needed. This would allow improved safety by insuring that necessary tasks are performed while reducing costs by eliminating procedures that are costly and not needed. The advantages fiber optical sensors have over conventional electro-mechanical systems like strain gauges have been widely extolled in the research literature. These advantages include their small size, low weight, immunity to electrical resistance, corrosion resistance, compatibility with composite materials and process conditions, and multiplexing capabilities. One fiber optic device which is suitable for distributed sensing is the fiber Bragg grating (FBG). Researchers at NASA MSFC are currently developing techniques for using FBGs for monitoring the integrity of advanced structural materials expected to become the mainstay of the current and future generation space structures. Since carbon-epoxy composites are the materials of choice for the current space structures, the initial study is concentrated on this type of composite. The goals of this activity are to use embedded FBG sensors for measuring strain and temperature of composite structures, and to investigate the effects of various parameters such as composite fiber orientation with respect to the optical sensor, unidirectional fiber composite, fabrication process etc., on the optical performance of the sensor. This paper describes an experiment to demonstrate the use of an embedded FBG for measuring strain in a composite material. The performance of the fiber optic sensor is determined by direct comparison with results from more conventional instrumentation.

The effect of interlaminar graphene nano-sheets reinforced e-glass fiber/ epoxy on low velocity impact response of a composite plate

NASA Astrophysics Data System (ADS)

Al-Maharma, A. Y.; Sendur, P.

2018-05-01

In this study, we compare the inter-laminar effect of graphene nano-sheets (GNSs) and CNTs on the single and multiple dynamic impact response of E-glass fiber reinforced epoxy composite (GFEP). In the comparisons, raw GFEP composite is used as baseline for quantifying the improvement on the dynamic impact response. For that purpose, finite element based models are developed for GNSs on GFEP, graphene coating on glass fibers, inter-laminar composite of CNTs reinforced polyester at 7.5 vol%, and combinations of all these reinforcements. Comparisons are made on three metrics: (i) total deformation, (ii) the contact force, and (iii) internal energy of the composite plate. The improvement on axial modulus (E1) of GFEP reinforced with one layer of GNS (0.5 wt%) without polyester at lamination sequence of [0]8 is 29.4%, which is very close to the improvement of 31% on storage modulus for multi-layer graphene with 0.5 wt% reinforced E-glass/epoxy composite at room temperature. Using three GNSs (1.5 wt%) reinforced polyester composite as interlaminar layer results in an improvement of 57.1% on E1 of GFEP composite. The simulation results reveal that the interlaminar three GNSs/polyester composite at mid-plane of GFEP laminated composite can significantly improve the dynamic impact resistance of GFEP structure compared to the other aforementioned structural reinforcements. Reinforcing GFEP composite with three layers of GNSs/polyester composite at mid-plane results in an average of 35% improvement on the dynamic impact resistance for healthy and damaged composite plate under low velocity impacts of single and multiple steel projectiles. This model can find application in various areas including structural health monitoring, fire retardant composite, and manufacturing of high strength and lightweight mechanical parts such as gas tank, aircraft wings and wind turbine blades.

Oxidation of boron nitride in an arc heated jet.

NASA Technical Reports Server (NTRS)

Buckley, J. D.

1971-01-01

Two grades of hot pressed boron nitride and a boron nitride composite were subjected to oxidation tests in a 2.5 megawatt atmospheric arc jet. The results showed that fabrication and/or composition influenced thermal shock and oxidation resistance. Changes in surface structure and recession due to oxidation suggest correlation with specimen composition. The boron nitride composite reacted with the oxygen in the hot subsonic airstream to produce a glassy coating on the hot face surface.

Review of Recent Developments on Using an Off-Lattice Monte Carlo Approach to Predict the Effective Thermal Conductivity of Composite Systems with Complex Structures

PubMed Central

Gong, Feng; Duong, Hai M.; Papavassiliou, Dimitrios V.

2016-01-01

Here, we present a review of recent developments for an off-lattice Monte Carlo approach used to investigate the thermal transport properties of multiphase composites with complex structure. The thermal energy was quantified by a large number of randomly moving thermal walkers. Different modes of heat conduction were modeled in appropriate ways. The diffusive heat conduction in the polymer matrix was modeled with random Brownian motion of thermal walkers within the polymer, and the ballistic heat transfer within the carbon nanotubes (CNTs) was modeled by assigning infinite speed of thermal walkers in the CNTs. Three case studies were conducted to validate the developed approach, including three-phase single-walled CNTs/tungsten disulfide (WS2)/(poly(ether ether ketone) (PEEK) composites, single-walled CNT/WS2/PEEK composites with the CNTs clustered in bundles, and complex graphene/poly(methyl methacrylate) (PMMA) composites. In all cases, resistance to heat transfer due to nanoscale phenomena was also modeled. By quantitatively studying the influencing factors on the thermal transport properties of the multiphase composites, it was found that the orientation, aggregation and morphology of fillers, as well as the interfacial thermal resistance at filler-matrix interfaces would limit the transfer of heat in the composites. These quantitative findings may be applied in the design and synthesis of multiphase composites with specific thermal transport properties. PMID:28335270

Use of Repeated Fluoropolymer Suspensions to Obtain Composite Electrochemical Coating Based on Zinc

NASA Astrophysics Data System (ADS)

Musikhina, T. A.; Zemtsova, E. A.; Fuks, C. L.

2017-11-01

This article deals with the issues of utilization of the waste products of fluoropolymers, namely, the suspensions of fluoroplasts that have lost their consumer properties. Such waste is recommended to be used as a filler of zinc coatings to provide increased corrosion resistance. Using the method of mathematical planning of the experiment, the authors establish the optimal compositions of galvanizing chloride-ammonium electrolytes to obtain the corrosion-resistant composite electrochemical coatings (CEC) of zinc-fluoropolymer. As a result, coatings with a finely crystalline structure were obtained differing in the distribution pattern on the surface of the samples and depending on the variation in the zinc concentration in the electrolytes. The samples of steel reinforcement with the zinc-fluoropolymer coating were tested on corrosion resistance. The increase of anticorrosive properties in CEC zinc-fluoropolymer and a slight decrease in microhardness were indicated.

Optimum electrode configuration selection for electrical resistance change based damage detection in composites using an effective independence measure

NASA Astrophysics Data System (ADS)

Escalona, Luis; Díaz-Montiel, Paulina; Venkataraman, Satchi

2016-04-01

Laminated carbon fiber reinforced polymer (CFRP) composite materials are increasingly used in aerospace structures due to their superior mechanical properties and reduced weight. Assessing the health and integrity of these structures requires non-destructive evaluation (NDE) techniques to detect and measure interlaminar delamination and intralaminar matrix cracking damage. The electrical resistance change (ERC) based NDE technique uses the inherent changes in conductive properties of the composite to characterize internal damage. Several works that have explored the ERC technique have been limited to thin cross-ply laminates with simple linear or circular electrode arrangements. This paper investigates a method of optimum selection of electrode configurations for delamination detection in thick cross-ply laminates using ERC. Inverse identification of damage requires numerical optimization of the measured response with a model predicted response. Here, the electrical voltage field in the CFRP composite laminate is calculated using finite element analysis (FEA) models for different specified delamination size and locations, and location of ground and current electrodes. Reducing the number of sensor locations and measurements is needed to reduce hardware requirements, and computational effort needed for inverse identification. This paper explores the use of effective independence (EI) measure originally proposed for sensor location optimization in experimental vibration modal analysis. The EI measure is used for selecting the minimum set of resistance measurements among all possible combinations of selecting a pair of electrodes among the n electrodes. To enable use of EI to ERC required, it is proposed in this research a singular value decomposition SVD to obtain a spectral representation of the resistance measurements in the laminate. The effectiveness of EI measure in eliminating redundant electrode pairs is demonstrated by performing inverse identification of damage using the full set of resistance measurements and the reduced set of measurements. The investigation shows that the EI measure is effective for optimally selecting the electrode pairs needed for resistance measurements in ERC based damage detection.

Highly Stable K2SiF6:Mn4+@K2SiF6 Composite Phosphor with Narrow Red Emission for White LEDs.

PubMed

Huang, Lin; Liu, Yong; Yu, Jinbo; Zhu, Yiwen; Pan, Fengjuan; Xuan, Tongtong; Brik, Mikhail G; Wang, Chengxin; Wang, Jing

2018-05-30

Poor water resistance and nongreen synthesis remain great challenges for commercial narrow red-emitting phosphor A 2 MF 6 :Mn 4+ (A = alkali metal ion; M = Si, Ge, Ti) for solid-state lighting and display. We develop here a simple and green growth route to synthesize homogeneous red-emitting composite phosphor K 2 SiF 6 :Mn 4+ @K 2 SiF 6 (KSFM@KSF) with excellent water resistance and high efficiency without the usage of toxic and volatile hydrogen fluoride solution. After immersing into water for 6 h, the as-obtained water-resistant products maintain 76% of the original emission intensity, whereas the emission intensity of non-water-resistant ones steeply drops down to 11%. A remarkable result is that after having kept at 85% humidity and at 85 °C for 504 h (21 days), the emission intensity of the as-obtained water-resistant products is at 80-90%, from its initial value, which is 2-3 times higher than 30-40% for the non-water-resistant products. The surface deactivation-enabled growth mechanism for these phosphors was proposed and investigated in detail. We found that nontoxic H 3 PO 4 /H 2 O 2 aqueous solution promotes the releasing and decomposition of the surface [MnF 6 ] 2- ions and the transformation of the KSFM surface to KSF, which finally contributes to the homogeneous KSFM@KSF composite structure. This composite structure strategy was also successfully used to treat KSFM phosphor prepared by other methods. We believe that the results obtained in the present paper will open the pathway for the large-scale environmentally friendly synthesis of the excellent antimoisture narrow red-emitting A 2 MF 6 :Mn 4+ phosphor to be used for white light-emitting diode applications.

METCAN: The metal matrix composite analyzer

NASA Technical Reports Server (NTRS)

Hopkins, Dale A.; Murthy, Pappu L. N.

1988-01-01

Metal matrix composites (MMC) are the subject of intensive study and are receiving serious consideration for critical structural applications in advanced aerospace systems. MMC structural analysis and design methodologies are studied. Predicting the mechanical and thermal behavior and the structural response of components fabricated from MMC requires the use of a variety of mathematical models. These models relate stresses to applied forces, stress intensities at the tips of cracks to nominal stresses, buckling resistance to applied force, or vibration response to excitation forces. The extensive research in computational mechanics methods for predicting the nonlinear behavior of MMC are described. This research has culminated in the development of the METCAN (METal Matrix Composite ANalyzer) computer code.

Bacterial phylogeny structures soil resistomes across habitats

PubMed Central

Forsberg, Kevin J.; Patel, Sanket; Gibson, Molly K.; Lauber, Christian L.; Knight, Rob; Fierer, Noah; Dantas, Gautam

2014-01-01

Summary Ancient and diverse antibiotic resistance genes (ARGs) have previously been identified from soil1–3, including genes identical to those in human pathogens4. Despite the apparent overlap between soil and clinical resistomes4–6, factors influencing ARG composition in soil and their movement between genomes and habitats remain largely unknown3. General metagenome functions often correlate with the underlying structure of bacterial communities7–12. However, ARGs are hypothesized to be highly mobile4,5,13, prompting speculation that resistomes may not correlate with phylogenetic signatures or ecological divisions13,14. To investigate these relationships, we performed functional metagenomic selections for resistance to 18 antibiotics from 18 agricultural and grassland soils. The 2895 ARGs we discovered were predominantly novel, and represent all major resistance mechanisms15. We demonstrate that distinct soil types harbor distinct resistomes, and that nitrogen fertilizer amendments strongly influenced soil ARG content. Resistome composition also correlated with microbial phylogenetic and taxonomic structure, both across and within soil types. Consistent with this strong correlation, mobility elements syntenic with ARGs were rare in soil compared to sequenced pathogens, suggesting that ARGs in the soil may not transfer between bacteria as readily as is observed in the clinic. Together, our results indicate that bacterial community composition is the primary determinant of soil ARG content, challenging previous hypotheses that horizontal gene transfer effectively decouples resistomes from phylogeny13,14. PMID:24847883

Bacterial phylogeny structures soil resistomes across habitats

NASA Astrophysics Data System (ADS)

Forsberg, Kevin J.; Patel, Sanket; Gibson, Molly K.; Lauber, Christian L.; Knight, Rob; Fierer, Noah; Dantas, Gautam

2014-05-01

Ancient and diverse antibiotic resistance genes (ARGs) have previously been identified from soil, including genes identical to those in human pathogens. Despite the apparent overlap between soil and clinical resistomes, factors influencing ARG composition in soil and their movement between genomes and habitats remain largely unknown. General metagenome functions often correlate with the underlying structure of bacterial communities. However, ARGs are proposed to be highly mobile, prompting speculation that resistomes may not correlate with phylogenetic signatures or ecological divisions. To investigate these relationships, we performed functional metagenomic selections for resistance to 18 antibiotics from 18 agricultural and grassland soils. The 2,895 ARGs we discovered were mostly new, and represent all major resistance mechanisms. We demonstrate that distinct soil types harbour distinct resistomes, and that the addition of nitrogen fertilizer strongly influenced soil ARG content. Resistome composition also correlated with microbial phylogenetic and taxonomic structure, both across and within soil types. Consistent with this strong correlation, mobility elements (genes responsible for horizontal gene transfer between bacteria such as transposases and integrases) syntenic with ARGs were rare in soil by comparison with sequenced pathogens, suggesting that ARGs may not transfer between soil bacteria as readily as is observed between human pathogens. Together, our results indicate that bacterial community composition is the primary determinant of soil ARG content, challenging previous hypotheses that horizontal gene transfer effectively decouples resistomes from phylogeny.

Incremental dynamic analysis of concrete moment resisting frames reinforced with shape memory composite bars

NASA Astrophysics Data System (ADS)

Zafar, Adeel; Andrawes, Bassem

2012-02-01

Fiber reinforced polymer (FRP) reinforcing bars have been used in concrete structures as an alternative to conventional steel reinforcement, in order to overcome corrosion problems. However, due to the linear behavior of the commonly used reinforcing fibers, they are not considered in structures which require ductility and damping characteristics. The use of superelastic shape memory alloy (SMA) fibers with their nonlinear elastic behavior as reinforcement in the composite could potentially provide a solution for this problem. Small diameter SMA wires are coupled with polymer matrix to produce SMA-FRP composite, which is sought in this research as reinforcing bars. SMA-FRP bars are sought in this study to enhance the seismic performance of reinforced concrete (RC) moment resisting frames (MRFs) in terms of reducing their residual inter-story drifts while still maintaining the elastic characteristics associated with conventional FRP. Three story one bay and six story two bay RC MRF prototype structures are designed with steel, SMA-FRP and glass-FRP reinforcement. The incremental dynamic analysis technique is used to investigate the behaviors of the two frames with the three different reinforcement types under a suite of ground motion records. It is found that the frames with SMA-FRP composite reinforcement exhibit higher performance levels including lower residual inter-story drifts, high energy dissipation and thus lower damage, which are important for structures in highly seismic zones.

Synergetic Effect of Yolk-Shell Structure and Uniform Mixing of SnS-MoS₂ Nanocrystals for Improved Na-Ion Storage Capabilities.

PubMed

Choi, Seung Ho; Kang, Yun Chan

2015-11-11

Mixed metal sulfide composite microspheres with a yolk-shell structure for sodium-ion batteries are studied. Tin-molybdenum oxide yolk-shell microspheres prepared by a one-pot spray pyrolysis process transform into yolk-shell SnS-MoS2 composite microspheres. The discharge capacities of the yolk-shell and dense-structured SnS-MoS2 composite microspheres for the 100th cycle are 396 and 207 mA h g(-1), and their capacity retentions measured from the second cycle are 89 and 47%, respectively. The yolk-shell SnS-MoS2 composite microspheres with high structural stability during repeated sodium insertion and desertion processes have low charge-transfer resistance even after long-term cycling. The synergetic effect of the yolk-shell structure and uniform mixing of the SnS and MoS2 nanocrystals result in the excellent sodium-ion storage properties of the yolk-shell SnS-MoS2 composite microspheres by improving their structural stability during cycling.

Three-Axis Distributed Fiber Optic Strain Measurement in 3D Woven Composite Structures

NASA Technical Reports Server (NTRS)

Castellucci, Matt; Klute, Sandra; Lally, Evan M.; Froggatt, Mark E.; Lowry, David

2013-01-01

Recent advancements in composite materials technologies have broken further from traditional designs and require advanced instrumentation and analysis capabilities. Success or failure is highly dependent on design analysis and manufacturing processes. By monitoring smart structures throughout manufacturing and service life, residual and operational stresses can be assessed and structural integrity maintained. Composite smart structures can be manufactured by integrating fiber optic sensors into existing composite materials processes such as ply layup, filament winding and three-dimensional weaving. In this work optical fiber was integrated into 3D woven composite parts at a commercial woven products manufacturing facility. The fiber was then used to monitor the structures during a VARTM manufacturing process, and subsequent static and dynamic testing. Low cost telecommunications-grade optical fiber acts as the sensor using a high resolution commercial Optical Frequency Domain Reflectometer (OFDR) system providing distributed strain measurement at spatial resolutions as low as 2mm. Strain measurements using the optical fiber sensors are correlated to resistive strain gage measurements during static structural loading. Keywords: fiber optic, distributed strain sensing, Rayleigh scatter, optical frequency domain reflectometry

Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments

DOEpatents

Holcombe, C.E. Jr.; Kovach, L.; Taylor, A.J.

1980-01-22

The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400/sup 0/K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10 to 30 vol% carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing gases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.

Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments

DOEpatents

Holcombe, Cressie E.; Kovach, Louis; Taylor, Albert J.

1981-01-01

The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400.degree. K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10-30 vol. % carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing bases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.

Environmental and High-Strain Rate effects on composites for engine applications

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Smith, G. T.

1982-01-01

The Lewis Research Center is conducting a series of programs intended to investigate and develop the application of composite materials to structural components for turbojet engines. A significant part of that effort is directed to establishing resistance, defect growth, and strain rate characteristics of composite materials over the wide range of environmental and load conditions found in commercial turbojet engine operations. Both analytical and experimental efforts are involved.

Epoxy/Fluoroether Composites

NASA Technical Reports Server (NTRS)

Rosser, R. W.; Taylor, M. S.

1986-01-01

Composite materials made from unfilled and glass-fiber-reinforced epoxy toughened by copolymerization with elastomeric prepolymers of perfluoroalkyl ether diacyl fluoride (EDAF). Improved properties due to hydrogen bonding between rubber phase and epoxy matrix, plus formation of rubberlike phase domains that molecularly interpenetrate with epoxy matrix. With optimum rubber content, particle size, and particle shape, entire molecular structure reinforced and toughened. Improved composites also show increased failure strength, stiffness, glass-transition temperature, and resistance to water.

[Resistant starches. Part II. Physico-chemical and technological aspects solution medico-biological problems].

PubMed

Iur'ev, V P; Gapparov, M M; Vasserman, L A; Genkina, N K

2006-01-01

This paper is a review of the recent literature data related to structure, composition and physico-chemical properties of starches as well as the special methods of processing of the starch containing raw sources producing the food products with increasing content of resistant starches. The prognosis is made about usefulness of such resistant starches for control of some metabolic disorder in human organism and for prophylactic aims.

Multi-Functional BN-BN Composite

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Bryant, Robert G. (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Gibbons, Luke (Inventor); Lowther, Sharon (Inventor); Thibeault, Sheila A. (Inventor); Fay, Catharine C. (Inventor)

2017-01-01

Multifunctional Boron Nitride nanotube-Boron Nitride (BN-BN) nanocomposites for energy transducers, thermal conductors, anti-penetrator/wear resistance coatings, and radiation hardened materials for harsh environments. An all boron-nitride structured BN-BN composite is synthesized. A boron nitride containing precursor is synthesized, then mixed with boron nitride nanotubes (BNNTs) to produce a composite solution which is used to make green bodies of different forms including, for example, fibers, mats, films, and plates. The green bodies are pyrolized to facilitate transformation into BN-BN composite ceramics. The pyrolysis temperature, pressure, atmosphere and time are controlled to produce a desired BN crystalline structure. The wholly BN structured materials exhibit excellent thermal stability, high thermal conductivity, piezoelectricity as well as enhanced toughness, hardness, and radiation shielding properties. By substituting with other elements into the original structure of the nanotubes and/or matrix, new nanocomposites (i.e., BCN, BCSiN ceramics) which possess excellent hardness, tailored photonic bandgap and photoluminescence, result.

Enhanced dielectric standoff and mechanical failure in field-structured composites

NASA Astrophysics Data System (ADS)

Martin, James E.; Tigges, Chris P.; Anderson, Robert A.; Odinek, Judy

1999-09-01

We report dielectric breakdown experiments on electric-field-structured composites of high-dielectric-constant BaTiO3 particles in an epoxy resin. These experiments show a significant increase in the dielectric standoff strength perpendicular to the field structuring direction, relative to control samples consisting of randomly dispersed particles. To understand the relation of this observation to microstructure, we apply a simple resistor-short breakdown model to three-dimensional composite structures generated from a dynamical simulation. In this breakdown model the composite material is assumed to conduct primarily through particle contacts, so the simulated structures are mapped onto a resistor network where the center of mass of each particle is a node that is connected to neighboring nodes by resistors of fixed resistance that irreversibly short to perfect conductors when the current reaches a threshold value. This model gives relative breakdown voltages that are in good agreement with experimental results. Finally, we consider a primitive model of the mechanical strength of a field-structured composite material, which is a current-driven, conductor-insulator fuse model. This model leads to a macroscopic fusing behavior and can be related to mechanical failure of the composite.

Method for preparing metallated filament-wound structures

DOEpatents

Peterson, George R.

1979-01-01

Metallated graphite filament-wound structures are prepared by coating a continuous multi-filament carbon yarn with a metal carbide, impregnating the carbide coated yarn with a polymerizable carbon precursor, winding the resulting filament about a mandrel, partially curing the impregnation in air, subjecting the wound composite to heat and pressure to cure the carbon precursor, and thereafter heating the composite in a sizing die at a pressure loading of at least 1000 psi for graphitizing the carbonaceous material in the composite. The carbide in the composite coalesces into rod-like shapes which are disposed in an end-to-end relationship parallel with the filaments to provide resistance to erosion in abrasive laden atmospheres.

Composition-dependent photoluminescence and electronic structure of 2-dimensional borocarbonitrides, BC X N (x = 1, 5)

NASA Astrophysics Data System (ADS)

Moses, Kota; Shirodkar, Sharmila N.; Waghmare, U. V.; Rao, C. N. R.

2014-04-01

Layered borocarbonitrides BCN and BC5N with a wide difference in composition have been prepared by the urea route. These 2D materials show a significant difference in the photoluminescence spectra, with BCN and BC5N showing maxima at 340 and 410 nm (3.61 and 3.0 eV), besides exhibiting different electrical resistivities. First-principles calculations show that BCN and BC5N are associated with different band gaps, the gap of the carbon-rich composition being lower. The change in the electronic structure and properties is related to the composition of BC X N i.e. the ordering of the graphene and BN domains.

Structural studies on carbon materials for advanced space technology. Part 1: Structure and oxidation behavior of some carbon/carbon composite materials

NASA Technical Reports Server (NTRS)

Fischbach, D. B.; Uptegrove, D. R.; Srinivasagopalan, S.

1974-01-01

The microstructure and some microstructural effects of oxidation have been investigated for laminar carbon fiber cloth/cloth binder matrix composite materials. It was found that cloth wave is important in determining the macrostructure of the composites X-ray diffraction analysis showed that the composites were more graphitic than the constituent fiber phases, indicating a graphitic binder matrix phase. Various tests which were conducted to investigate specific properties of the material are described. It was learned that under the moderate temperature and oxidant flow conditions studied, C-700, 730 materials exhibit superior oxidation resistance primarily because of the inhibiting influence of the graphitized binder matrix.

Adsorption and desorption performance of benzene over hierarchically structured carbon-silica aerogel composites.

PubMed

Dou, Baojuan; Li, Jinjun; Wang, Yufei; Wang, Hailin; Ma, Chunyan; Hao, Zhengping

2011-11-30

Hierarchically structured carbon-silica aerogel (CSA) composites were synthesized from cheap water glass precursors and granulated activated carbon via a post-synthesis surface modification with trimethylchlorosilane (TMCS) and a low-cost ambient pressure drying procedure. The resultant CSA composites possess micro/mesoporous structure and hydrophobic surface. The adsorption and desorption performance of benzene on carbon-silica aerogel composite (CSA-2) under static and dynamic conditions were investigated, comparing with pure silica aerogel (CSA-0) and microporous activated carbon (AC). It was found that CSA-2 has high affinity towards aromatic molecules and fast adsorption kinetics. Excellent performance of dynamic adsorption and desorption observed on CSA-2 is related to its higher adsorption capacity than CSA-0 and less mass transfer resistance than AC, arising from the well-developed microporosity and open foam mesostructure in the CSA composites. Copyright © 2011 Elsevier B.V. All rights reserved.

Damage-Tolerant Polymer Composite Systems

NASA Astrophysics Data System (ADS)

Reifsnider, Kenneth L.

1988-11-01

One of the reasons for the rapid growth in the application of polymer composites is the opportunity they provide for the design and construction of composite structures that are especially resistant to losses of strength or reduced life resulting from damage during service. The usefulness of such materials is enhanced by the variety of reinforcement schemes that can be chosen to reflect specific service conditions. Under cyclic loading and demanding mechanical situations (e.g., helicopter parts, vehicle springs and high-speed rotors), polymer composites are considerably superior to competing materials.

A Progressive Damage Methodology for Residual Strength Predictions of Notched Composite Panels

NASA Technical Reports Server (NTRS)

Coats, Timothy W.; Harris, Charles E.

1998-01-01

The translaminate fracture behavior of carbon/epoxy structural laminates with through-penetration notches was investigated to develop a residual strength prediction methodology for composite structures. An experimental characterization of several composite materials systems revealed a fracture resistance behavior that was very similar to the R-curve behavior exhibited by ductile metals. Fractographic examinations led to the postulate that the damage growth resistance was primarily due to fractured fibers in the principal load-carrying plies being bridged by intact fibers of the adjacent plies. The load transfer associated with this bridging mechanism suggests that a progressive damage analysis methodology will be appropriate for predicting the residual strength of laminates with through-penetration notches. A progressive damage methodology developed by the authors was used to predict the initiation and growth of matrix cracks and fiber fracture. Most of the residual strength predictions for different panel widths, notch lengths, and material systems were within about 10% of the experimental failure loads.

The impact behaviour of silk cocoons.

PubMed

Chen, Fujia; Hesselberg, Thomas; Porter, David; Vollrath, Fritz

2013-07-15

Silk cocoons, constructed by silkmoths (Lepidoptera), are protective structural composites. Some cocoons appear to have evolved towards structural and material optimisation in order to sustain impact strikes from predators and hinder parasite ingress. This study investigates the protective properties of silk cocoons with different morphologies by evaluating their impact resistance and damage tolerance. Finite element analysis was used to analyse empirical observations of the quasi-static impact response of the silk cocoons, and to evaluate the separate benefits of the structures and materials through the deformation and damage mechanism. We use design principles from composite engineering in order to understand the structure-property-function relationship of silkworm cocoons. Understanding the highly evolved survival strategies of the organisms building natural cocoons will hopefully lead to inspiration that in turn could lead to improved composite design.

In situ preparation of NiS2/CoS2 composite electrocatalytic materials on conductive glass substrates with electronic modulation for high-performance counter electrodes of dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Li, Faxin; Wang, Jiali; Zheng, Li; Zhao, Yaqiang; Huang, Niu; Sun, Panpan; Fang, Liang; Wang, Lei; Sun, Xiaohua

2018-04-01

The electrocatalytic composite materials of honeycomb structure NiS2 nanosheets loaded with metallic CoS2 nanoparticles are in situ prepared on F doped SnO2 conductive glass (FTO) substrates used as counter electrodes of DSSCs through chemical bath deposition (CBD) and sulfidizing process. Single crystalline NiS2 honeycomb structure array lay a foundation for the large surface area of NiS2/CoS2 composite CEs. The formed NiS2/CoS2 nanointerface modulates electronic structure of composite CEs from the synergetic interactions between CoS2 nanoparticles and NiS2 nanosheets, which dramatically improves the electrocatalytic activity of NiS2/CoS2 composite CEs; Metallic CoS2 nanoparticles covering NiS2 nanosheets electrodes adjusts the electrodes' structure and then reduces the series resistance (Rs) and the Nernst diffusion resistance (Zw) of counter electrodes. The improvement of these areas greatly enhances the electrocatalytic performance of CEs and the short circuit current density (Jsc) and Fill factor (FF) of DSSCs. Impressively, the DSSC based on NiS2/CoS2-0.1 CE shows the best photovoltaic performance with photovoltaic conversion efficiency of 8.22%, which is 24.36% higher than that (6.61%) of the DSSC with Pt CE. And the NiS2/CoS2-0.1 CE also displays a good stability in the iodine based electrolyte. This work indicates that rational construction of composite electrocatalytic materials paves an avenue for high-performance counter electrodes of DSSCs.

Optimisation of the geometry of the drill bit and process parameters for cutting hybrid composite/metal structures in new aircrafts

NASA Astrophysics Data System (ADS)

Isbilir, Ozden

Owing to their desirable strength-to-weight characteristics, carbon fibre reinforced polymer composites have been favourite materials for structural applications in different industries such as aerospace, transport, sports and energy. They provide a weight reduction in whole structure and consequently decrease fuel consumption. The use of lightweight materials such as titanium and its alloys in modern aircrafts has also increased significantly in the last couple of decades. Titanium and its alloys offer high strength/weight ratio, high compressive and tensile strength at high temperatures, low density, excellent corrosion resistance, exceptional erosion resistance, superior fatigue resistance and relatively low modulus of elasticity. Although composite/metal hybrid structures are increasingly used in airframes nowadays, number of studies regarding drilling of composite/metal stacks is very limited. During drilling of multilayer materials different problems may arise due to very different attributes of these materials. Machining conditions of drilling such structures play an important role on tool wear, quality of holes and cost of machining.. The research work in this thesis is aimed to investigate drilling of CFRP/Ti6Al4V hybrid structure and to optimize process parameters and drill geometry. The research work consist complete experimental study including drilling tests, in-situ and post measurements and related analysis; and finite element analysis including fully 3-D finite element models. The experimental investigations focused on drilling outputs such as thrust force, torque, delamination, burr formation, surface roughness and tool wear. An algorithm was developed to analyse drilling induced delamination quantitatively based on the images. In the numerical analysis, novel 3-D finite element models of drilling of CFRP, Ti6Al4V and CFRP/Ti6Al4V hybrid structure were developed with the use of 3-D complex drill geometries. A user defined subroutine was developed to model material and failure behaviour of CFRP. The effects of process parameters on drilling outputs have been investigated and compared with the experimental results. The influences of drill bit geometries have been simulated in this study..

Heat resistant composite structure for shuttle applications (Ryton-B)

NASA Technical Reports Server (NTRS)

1972-01-01

A program was undertaken to characterize Ryton-B resin, develop graphite filament prepregs, undirectional laminates and determine the strength and heat resistance of the composite system. Through the use of a water soluble resin binder, high quality prepreg tape, three inches wide with 4 tows of HM-S were produced. The tape laminated to 0.00175 inch per ply. A wide range of properties in the cured resin and laminate were found using different curing conditions. The thermal stability and strength of molded laminates appears to be very dependent upon the cure cycle used for polymerization.

High-temperature Friction and Wear Resistance of Ni-Co-SiC Composite Coatings

NASA Astrophysics Data System (ADS)

Guo, Fang; Sun, Wan-chang; Jia, Zong-wei; Liu, Xiao-jia; Dong, Ya-ru

2018-05-01

Ni-Co alloy and SiC micro-particles were co-deposited on 45 steel by electrodeposition for high temperature performance. The high temperature tribological characteristics were studied by use of a ball-on-disk method. The micrographs and phase structure of the Ni-Co-SiC composite coatings after high-temperature friction were observed by using a field emission scanning electron microscope(FESEM). The results reveal that the Ni-Co-SiC composite coating presents better wear resistance and lower friction coefficient at high temperature in comparison with that of Ni-Co coating and 45 steel substrate. The embedded SiC particles could strengthen the alloy coating by dispersion strengthening effect and changing the friction mechanism from adhesive wear to abrasive wear.

Research on Extrusion of Rubber Composites Reinforced by Short Fibers Orientation Based on FEA

NASA Astrophysics Data System (ADS)

Zhang, Dewei; Wang, Chuansheng; Shen, Bo; Li, Shaoming; Bian, Huiguang

2018-06-01

In recent years, rubber composites reinforced by short fibers has been researched deeply, because of its good performances such as higher wear resistance, higher cut resistance and so on. Some research results indicated that if short fibers get orientation in rubber composites, the performances of rubber products could be promoted greatly. But how to make short fibers get orientation in rubber matrix during extrusion is still a real problem. And there are many parameters affect the short fibers orientation. So, in this paper, the effects of die structure including expansion-die and dam-expansion-die on extrusion flow field of short fiber and rubber composite material during extrusion process has been researched by Polyflow. And the FEA results about the pressure field, velocity field and the velocity vector of the rubber composites flow field indicate that, comparing with expansion-die and the dam-expansion-die, the latter one is better for the extrusion process of rubber composites and making short fibers get radial orientation in rubber matrix.

Single-walled carbon nanotubes/polymer composite electrodes patterned directly from solution.

PubMed

Chang, Jingbo; Najeeb, Choolakadavil Khalid; Lee, Jae-Hyeok; Kim, Jae-Ho

2011-06-07

This work describes a simple technique for direct patterning of single-walled carbon nanotube (SWNT)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) composite electrodes in a large area on a substrate based on the solution transfer process by microcontact printing using poly(dimethylsiloxane) (PDMS) stamps. Various shapes of SWNT/PEDOT-PSS composite patterns, such as line, circle, and square, can be easily fabricated with high pattern fidelity and structural integrity. The single parallel line pattern device exhibits high electrical conductivity (0.75 × 10(5) S/m) and electronic stability because of alignment of nanotubes and big-size SWNT bundles (∼5 nm). The electromechanical study reveals that the composite patterns show ∼1% resistance change along SWNT alignment direction and ∼5% resistance change along vertical alignment direction after 200 bend cycles. Our approach provides a facile, low-cost method to pattern transparent conductive SWNT/polymer composite electrodes and demonstrates a novel platform for future integration of conducting SWNT/polymer composite patterns for optoelectronic applications.

Piezoresistivity of Resin-Impregnated Carbon Nanotube Film at High Temperatures.

PubMed

Li, Min; Zuo, Tianyi; Wang, Shaokai; Gu, Yizhuo; Gao, Limin; Li, Yanxia; Zhang, Zuoguang

2018-06-13

This paper presents the development of a continuous carbon nanotube (CNT) composite film sensor with a strain detecting range of 0-2% for structural composites. The strain-dependent resistance responses of continuous CNT film and its resin-impregnated composite films were investigated at temperatures as high as 200 °C. The results manifest that impregnation with resin leads to a much larger gauge factor than pristine film. Both the pristine and composite films show an increase in resistivity with increasing temperature. For different composite films, the ordering of gauge factors is consistent with that of the matrix moduli. This indicates that a resin matrix with higher modulus and strong interactions between CNTs/CNT bundles and the resin matrix are beneficial for enhancing the piezoresistive effect. The CNT/PAA composite film has a gauge factor of 4.3 at 150 °C, an order of magnitude higher than the metal foil sensor. Therefore, the CNT composite films have great potential for simultaneous application for reinforcement and as strain sensor to realise a multifunctional composite. © 2018 IOP Publishing Ltd.

The Composition and Spatial Patterns of Bacterial Virulence Factors and Antibiotic Resistance Genes in 19 Wastewater Treatment Plants

PubMed Central

Zhang, Bing; Xia, Yu; Wen, Xianghua; Wang, Xiaohui; Yang, Yunfeng; Zhou, Jizhong; Zhang, Yu

2016-01-01

Bacterial pathogenicity and antibiotic resistance are of concern for environmental safety and public health. Accumulating evidence suggests that wastewater treatment plants (WWTPs) are as an important sink and source of pathogens and antibiotic resistance genes (ARGs). Virulence genes (encoding virulence factors) are good indicators for bacterial pathogenic potentials. To achieve a comprehensive understanding of bacterial pathogenic potentials and antibiotic resistance in WWTPs, bacterial virulence genes and ARGs in 19 WWTPs covering a majority of latitudinal zones of China were surveyed by using GeoChip 4.2. A total of 1610 genes covering 13 virulence factors and 1903 genes belonging to 11 ARG families were detected respectively. The bacterial virulence genes exhibited significant spatial distribution patterns of a latitudinal biodiversity gradient and a distance-decay relationship across China. Moreover, virulence genes tended to coexist with ARGs as shown by their strongly positive associations. In addition, key environmental factors shaping the overall virulence gene structure were identified. This study profiles the occurrence, composition and distribution of virulence genes and ARGs in current WWTPs in China, and uncovers spatial patterns and important environmental variables shaping their structure, which may provide the basis for further studies of bacterial virulence factors and antibiotic resistance in WWTPs. PMID:27907117

Self-Sensing of Position-Related Loads in Continuous Carbon Fibers-Embedded 3D-Printed Polymer Structures Using Electrical Resistance Measurement

PubMed Central

Luan, Congcong; Shen, Hongyao; Fu, Jianzhong

2018-01-01

Condition monitoring in polymer composites and structures based on continuous carbon fibers show overwhelming advantages over other potentially competitive sensing technologies in long-gauge measurements due to their great electromechanical behavior and excellent reinforcement property. Although carbon fibers have been developed as strain- or stress-sensing agents in composite structures through electrical resistance measurements, the electromechanical behavior under flexural loads in terms of different loading positions still lacks adequate research, which is the most common situation in practical applications. This study establishes the relationship between the fractional change in electrical resistance of carbon fibers and the external loads at different loading positions along the fibers’ longitudinal direction. An approach for real-time monitoring of flexural loads at different loading positions was presented simultaneously based on this relationship. The effectiveness and feasibility of the approach were verified by experiments on carbon fiber-embedded three-dimensional (3D) printed thermoplastic polymer beam. The error in using the provided approach to monitor the external loads at different loading positions was less than 1.28%. The study fully taps the potential of continuous carbon fibers as long-gauge sensory agents and reinforcement in the 3D-printed polymer structures. PMID:29584665

Composite Sandwich Structures for Shock Mitigation and Energy Absorption

DTIC Science & Technology

2016-06-28

analysis of the blast performance of foam -core, composite sandwich panels was that on a per unit areal weight density basis, lighter and more crushable... foam cores offered greater blast resistance and energy absorption than the heavier and stronger foam cores. This was found to be the case even on an...absolute weight basis for cuNed sandwich panels and panels subjected to underwater blast. 15. SUBJECT TERMS composite; foam -core sandwich; blast

Characterization and mechanical properties investigation of TiN-Ag films onto Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Du, Dongxing; Liu, Daoxin; Zhang, Xiaohua; Tang, Jingang; Xiang, Dinggen

2016-03-01

To investigate their effect on fretting fatigue (FF) resistance of a Ti-6Al-4V alloy, hard solid lubricating composite films of TiN with varying silver contents (TiN-Ag) were deposited on a Ti-6Al-4V alloy using ion-assisted magnetron sputtering. The surface morphology and structure were analyzed by atomic force microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. The hardness, bonding strength, and toughness of films were tested using a micro-hardness tester, scratch tester, and a repeated press-press test system that was manufactured in-house, respectively. The FF resistance of TiN-Ag composite films was studied using self-developed devices. The results show that the FF resistance of a titanium alloy can be improved by TiN-Ag composite films, which were fabricated using hard TiN coating doped with soft Ag. The FF life of Ag0.5, Ag2, Ag5, Ag10 and Ag20 composite films is 2.41, 3.18, 3.20, 2.94 and 2.87 times as great as that of the titanium alloy, respectively. This is because the composite films have the better toughness, friction lubrication, and high bonding strength. When the atomic fraction of Ag changes from 2% to 5%, the FF resistance of the composite films shows the best performance. This is attributed to the surface integrity of the composite film is sufficiently fine to prevent the initiation and early propagation of FF cracks.

Standard test evaluation of graphite fiber/resin matrix composite materials for improved toughness

NASA Technical Reports Server (NTRS)

Chapman, Andrew J.

1984-01-01

Programs sponsored by NASA with the commercial transport manufacturers to develop a technology data base are required to design and build composite wing and fuselage structures. To realize the full potential of composite structures in these strength critical designs, material systems having improved ductility and interlaminar toughness are being sought. To promote systematic evaluation of new materials, NASA and the commercial transport manufacturers have selected and standardized a set of five common tests. These tests evaluate open hole tension and compression performance, compression performance after impact at an energy level of 20 ft-lb, and resistance to delamination. Ten toughened resin matrix/graphite fiber composites were evaluated using this series of tests, and their performance is compared with a widely used composite system.

Fracture-resistant monolithic dental crowns.

PubMed

Zhang, Yu; Mai, Zhisong; Barani, Amir; Bush, Mark; Lawn, Brian

2016-03-01

To quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns. Fracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution. Experimental measurements and XFEM predictions were self-consistent within data scatter. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Stages of crack propagation within the crown and support substrate were quantified. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Dental nanocomposite crowns have comparable fracture resistance to natural enamel. The results confirm that monolithic crowns are able to sustain high bite forces. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity. Copyright © 2015 Academy of Dental Materials. All rights reserved.

A Water-/Fireproof Flexible Lithium-Oxygen Battery Achieved by Synergy of Novel Architecture and Multifunctional Separator.

PubMed

Yin, Yan-Bin; Yang, Xiao-Yang; Chang, Zhi-Wen; Zhu, Yun-Hai; Liu, Tong; Yan, Jun-Min; Jiang, Qing

2018-01-01

To meet the increasing demands for portable and flexible devices in a rapidly developing society, it is urgently required to develop highly safe and flexible electrochemical energy-storage systems. Flexible lithium-oxygen batteries with high theoretical specific energy density are promising candidates; however, the conventional half-open structure design prevents it from working properly under water or fire conditions. Herein, as a proof-of-concept experiment, a highly safe flexible lithium-oxygen battery achieved by the synergy of a vital multifunctional structure design and a unique composite separator is proposed and fabricated. The structure can effectively prevent the invasion of water from the environment and combustion, which is further significantly consolidated with the help of a polyimide and poly(vinylidene fluoride-co-hexafluoropropylene) composite separator, which holds good water resistance, thermal stability, and ionic conductivity. Unexpectedly, the obtained lithium-oxygen battery exhibits superior flexibility, water resistance, thermal resistance, and cycling stability (up to 218 cycles; at a high current of 1 mA and capacity of 4 mA h). This novel water/fireproof, flexible lithium-oxygen battery is a promising candidate to power underwater flexible electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

FRACTURE-RESISTANT MONOLITHIC DENTAL CROWNS

PubMed Central

Zhang, Yu; Mai, Zhisong; Barani, Amir; Bush, Mark; Lawn, Brian

2016-01-01

Objective To quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns. Methods Fracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution. Results Experimental measurements and XFEM predictions were self consistent within data scatter. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Stages of crack propagation within the crown and support substrate were quantified. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Dental nanocomposite crowns have comparable fracture resistance to natural enamel. Significance The results confirm that monolithic crowns are able to sustain high bite forces. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity. PMID:26792623

Enhancing breakdown strength and energy storage performance of PVDF-based nanocomposites by adding exfoliated boron nitride

NASA Astrophysics Data System (ADS)

Xie, Yunchuan; Wang, Jian; Yu, Yangyang; Jiang, Wanrong; Zhang, Zhicheng

2018-05-01

Polymer/ceramic nanocomposites are promising dielectrics for high energy storage density (Ue) capacitors. However, their low breakdown strength (Eb) and high dielectric loss due to heterogeneous structure seriously limit their applications under high electric field. In this work, boron nitride nano-sheets (BNNS) exfoliated from BN particles were introduced into PVDF-based BaTiO3 (mBT) binary composites to reduce the dielectric loss and promote the Ue. The effects of BNNS on the dielectric properties, especially breakdown resistance, and energy storage performance of the resultant composites were carefully investigated by comparing with the composites without BNNS. The introduction of BNNS could significantly improve Eb and Ue of the final composites. Ternary composite with particle contents of 6 wt% BNNS and 5 wt% mBT presented a Eb of about 400 MV/m and Ue of 5.2 J/cm3, which is 40% and 30% superior to that of the binary composite with 5 wt% mBT, respectively. That may be attributed to the 2D structure, high bulk electrical resistivity, and fine dispersion in PVDF of BNNS, which is acting as an efficient insulating barrier against the leakage current and charges conduction. The depression effect of BNNS onto the charge mobility and the interfacial polarization of the polymer composites is finely addressed, which may offer a promising strategy for the fabrication of high-k polymer composites with low loss.

Structure dependent resistivity and dielectric characteristics of tantalum oxynitride thin films produced by magnetron sputtering

NASA Astrophysics Data System (ADS)

Cristea, D.; Crisan, A.; Cretu, N.; Borges, J.; Lopes, C.; Cunha, L.; Ion, V.; Dinescu, M.; Barradas, N. P.; Alves, E.; Apreutesei, M.; Munteanu, D.

2015-11-01

The main purpose of this work is to present and to interpret the change of electrical properties of TaxNyOz thin films, produced by DC reactive magnetron sputtering. Some parameters were varied during deposition: the flow of the reactive gases mixture (N2 and O2, with a constant concentration ratio of 17:3); the substrate voltage bias (grounded, -50 V or -100 V) and the substrate (glass, (1 0 0) Si or high speed steel). The obtained films exhibit significant differences. The variation of the deposition parameters induces variations of the composition, microstructure and morphology. These differences cause variation of the electrical resistivity essentially correlated with the composition and structural changes. The gradual decrease of the Ta concentration in the films induces amorphization and causes a raise of the resistivity. The dielectric characteristics of some of the high resistance TaxNyOz films were obtained in the samples with a capacitor-like design (deposited onto high speed steel, with gold pads deposited on the dielectric TaxNyOz films). Some of these films exhibited dielectric constant values higher than those reported for other tantalum based dielectric films.

Analysis of the Shear Behavior of Stubby Y-Type Perfobond Rib Shear Connectors for a Composite Frame Structure.

PubMed

Kim, Sang-Hyo; Kim, Kun-Soo; Lee, Do-Hoon; Park, Jun-Seung; Han, Oneil

2017-11-22

Shear connectors are used in steel beam-concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13.

Bismaleimides and related maleimido polymers as matrix resins

NASA Technical Reports Server (NTRS)

Parker, J. A.; Kourtides, D. A.; Fohlen, G. M.

1985-01-01

Significant processing and property improvements can be achieved by copolymerization of state-of-the-art bisimides with various vinyl stilbazole derivatives to give both fire resistance and high-temperature properties from hot-melt compositions. Significant improvement in mechanical properties is achieved through these modifications, which may make these new matrix resins ideal candidates for fireworthy secondary graphite composite structures. Phosphorous modifications of maleimido polymers through phosphonate structure and tricyclophosphazene derivatives provide families of new matrix resins for short-time applications in severe thermo-oxidative environments. With further research these may provide matrix resins for long-term thermo-oxidative stability of advanced composites at temperatures up to 400 to 500 C.

New materials for high temperature turbines; ONERA's DS composites confronted with blade problems

NASA Technical Reports Server (NTRS)

Bibring, H.

1977-01-01

ONERA's refractory DS composites were cited as materials required for use in advanced aircraft turbines, operating at high temperatures. These materials were found to be reliable in the construction of turbine blades. Requirements for a blade material in aircraft turbines operating at higher temperatures were compared with the actual performance as found in COTAC DS composite testing. The structure and properties of the more fully developed 74 and 741 types were specified. High temperature structural stability, impact of thermal and mechanical fatigue, oxidation resistance and coating capability were thoroughly evaluated. The problem of cooling passages in DS eutectic blades is also outlined.

Growth and piezoelectric properties of Ca3Nb(Al0.5Ga0.5)3Si2O14 crystals with langasite structure

NASA Astrophysics Data System (ADS)

Xiong, Kainan; Zheng, Yanqing; Tu, Xiaoniu; Jiang, Bohan; Cao, Shuoliang; Shi, Erwei

2017-06-01

Piezoelectric crystals Ca3Nb(Al0.5Ga0.5)3Si2O14 (CNAGS) with langasite structure have been successfully grown by Czochralski method. In this work, the crystal structure, quality, chemical composition, piezoelectric properties, electric resistivity and optical properties of the as-grown crystals were characterized. The full width at half-maximum (FWHM) of the rocking curve of CNAGS was found to be 23″. The chemical compositions of CNAGS crystals are very close to that of initial compositions. At room temperature, the piezoelectric coefficients d11 and d14 of CNAGS crystals are 4.12 pC/N and -5.03 pC/N, and the electromechanical coupling coefficients k12 and k26 are also determined as 11.6% and 18.3%, respectively. The electric resistivity of as-growth crystal was found to be on the order of 2×108 Ω cm at 500 °C and 1×106 Ω cm at 800 °C. And the transmittances of CNAGS crystals were found to be over 80% in the wavelength range of 700-2700 nm.

Effect of Carbon on the Electrical Properties of Copper Oxide-Based Bulk Composites

NASA Astrophysics Data System (ADS)

Kalinin, Yu. E.; Kashirin, M. A.; Makagonov, V. A.; Pankov, S. Yu.; Sitnikov, A. V.

2018-04-01

The effect of carbon filler on the electrical resistance and the thermopower of copper oxide-based composites produced by ceramic technology by hot pressing has been studied. It is found that the dependences of the electrical resistivity on the filler concentration are characteristic by S-like curves that are typical of percolation systems; in this case, the resistivity decreases more substantially as the carbon content increases as compared to the decrease in thermopower value, which is accompanied by the existence of the maximum of the factor of thermoelectric power near the percolation threshold. The studies of the temperature dependences of the resistivity and the thermopower at low temperatures show that, in the range 240-300 K, the predominant mechanism of the electrotransfer of all the composites under study is the hopping mechanism. At temperatures lower than 240 K, the composites with a nanocrystalline CuO matrix have a hopping conductivity with a variable hopping distance over localized states of the matrix near the Fermi level, which is related to the conductivity over intergrain CuO boundaries. A schematic model of the band structure of nanocrystalline CuO with carbon filler is proposed on the base of the analysis of the found experimental regularities of the electrotransfer.

The Effect of Cu:Ag Atomic Ratio on the Properties of Sputtered Cu–Ag Alloy Thin Films

PubMed Central

Hsieh, Janghsing; Hung, Shunyang

2016-01-01

Cu–Ag thin films with various atomic ratios were prepared using a co-sputtering technique, followed by rapid thermal annealing at various temperatures. The films’ structural, mechanical, and electrical properties were then characterized using X-ray diffractometry (XRD), atomic force microscopy (AFM), FESEM, nano-indentation, and TEM as functions of compositions and annealing conditions. In the as-deposited condition, the structure of these films transformed from a one-phase to a dual-phase state, and the resistivity shows a twin-peak pattern, which can be explained in part by Nordheim’s Rule and the miscibility gap of Cu–Ag alloy. After being annealed, the films’ resistivity followed the mixture rule in general, mainly due to the formation of a dual-phase structure containing Ag-rich and Cu-rich phases. The surface morphology and structure also varied as compositions and annealing conditions changed. The recrystallization of these films varied depending on Ag–Cu compositions. The annealed films composed of 40 at % to 60 at % Cu had higher hardness and lower roughness than those with other compositions. Particularly, the Cu50Ag50 film had the highest hardness after being annealed. From the dissolution testing, it was found that the Cu-ion concentration was about 40 times higher than that of Ag. The galvanic effect and over-saturated state could be the cause of the accelerated Cu dissolution and the reduced dissolution of the Ag. PMID:28774033

Shear Resistance between Concrete-Concrete Surfaces

NASA Astrophysics Data System (ADS)

Kovačovic, Marek

2013-12-01

The application of precast beams and cast-in-situ structural members cast at different times has been typical of bridges and buildings for many years. A load-bearing frame consists of a set of prestressed precast beams supported by columns and diaphragms joined with an additionally cast slab deck. This article is focused on the theoretical and experimental analyses of the shear resistance at an interface. The first part of the paper deals with the state-of-art knowledge of the composite behaviour of concrete-concrete structures and a comparison of the numerical methods introduced in the relevant standards. In the experimental part, a set of specimens with different interface treatments was tested until failure in order to predict the composite behaviour of coupled beams. The experimental part was compared to the numerical analysis performed by means of FEM basis nonlinear software.

Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

PubMed

Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

2016-05-11

The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

An in vitro investigation of wear resistance and hardness of composite resins.

PubMed

Cao, Liqun; Zhao, Xinyi; Gong, Xu; Zhao, Shouliang

2013-01-01

The aim of the present study was to investigate the wear resistance and hardness of five kinds of composite resins. Sixty-five specimens were fabricated with one nano-hybrid (Charisma Diamond), two micro-hybrid (3MZ250, Clearfil AP-X) and two packable (3MP60, Surefil) composite resins, according to a randomized complete block design (n=13, 8 for wear test; 5 for hardness test). The composites were filled in a rectangular mold, and light polymerization. After storage in 37°C deionized water for 24h, all specimens were tested with a custom-made toothbrush machine with a stainless-steel ball as antagonist (3N loads, 1Hz, 6×10(5) cycles) immersed in calcium fluoride slurry. Wear volume, hardness and surface structure of each tested material was examined by a three-dimensional non-contact optical profilometer, Vickers indentation technique and scanning electron microscope. The volume loss ranked from least to most as follows: Charisma Diamond, P60, Z250, Clearfil AP-X and Surefil. Regarding hardness, the rank from highest to lowest as follows: Clearfil AP-X, P60, Surefil, Z250, Charisma Diamond. The interactions between wear resistance and microhardness were not significant. The custom-made machine is considered suitable to simulate sliding of an antagonist cusp on an opposing occlusal composite restoration. Nanofilled composite may have superior wear compared to other composite resins.

Highly improved Uv resistance and composite interfacial properties of aramid fiber via iron (III) coordination

NASA Astrophysics Data System (ADS)

Cheng, Zheng; Hong, Dawei; Dai, Yu; Jiang, Chan; Meng, Chenbo; Luo, Longbo; Liu, Xiangyang

2018-03-01

The poor Uv stability and weak interfacial adhesion are considered as the bottleneck problems for further application of aramid fiber. Herein, a new strategy, Fe3+ coordination, was reported for aramid fiber to simultaneous improve its Uv resistance and composite interfacial shear strength. Fe3+ was introduced onto aramid fiber by coordinating with benzimidazole unit of fiber structure. It can reach a doping capacity of as high as 1516ug/g fiber, and the fiber surface is saturatedly covered with Fe3+. The chemical structure of Fe3+-benzimidazole brings about strong metal-enhanced fluorescence emission effect, which, in turn, greatly raises its Uv stability. Owing to the Fe3+ coordination, the tensile strength of Fe-coordinated fiber could preserve as high as 96% after Uv irradiation, compared with 73% of untreated fiber. Meanwhile, the introduction of Fe3+ improves the surface polarity of aramid fiber and consequently leads to the increase of the composite interfacial shear strength by 39%. It is believed that the Fe-coordinated fiber integrates the advantages of easy production, cost-effective and increased Uv stability, as well as high composite interfacial adhesion, and can be used as promising enhancement for the advanced composite material in harsh environment.

Large strain variable stiffness composites for shear deformations with applications to morphing aircraft skins

NASA Astrophysics Data System (ADS)

McKnight, G. P.; Henry, C. P.

2008-03-01

Morphing or reconfigurable structures potentially allow for previously unattainable vehicle performance by permitting several optimized structures to be achieved using a single platform. The key to enabling this technology in applications such as aircraft wings, nozzles, and control surfaces, are new engineered materials which can achieve the necessary deformations but limit losses in parasitic actuation mass and structural efficiency (stiffness/weight). These materials should exhibit precise control of deformation properties and provide high stiffness when exercised through large deformations. In this work, we build upon previous efforts in segmented reinforcement variable stiffness composites employing shape memory polymers to create prototype hybrid composite materials that combine the benefits of cellular materials with those of discontinuous reinforcement composites. These composites help overcome two key challenges for shearing wing skins: the resistance to out of plane buckling from actuation induced shear deformation, and resistance to membrane deflections resulting from distributed aerodynamic pressure loading. We designed, fabricated, and tested composite materials intended for shear deformation and address out of plane deflections in variable area wing skins. Our designs are based on the kinematic engineering of reinforcement platelets such that desired microstructural kinematics is achieved through prescribed boundary conditions. We achieve this kinematic control by etching sheets of metallic reinforcement into regular patterns of platelets and connecting ligaments. This kinematic engineering allows optimization of materials properties for a known deformation pathway. We use mechanical analysis and full field photogrammetry to relate local scale kinematics and strains to global deformations for both axial tension loading and shear loading with a pinned-diamond type fixture. The Poisson ratio of the kinematically engineered composite is ~3x higher than prototypical orthotropic variable stiffness composites. This design allows us to create composite materials that have high stiffness in the cold state below SMP T g (4-14GPa) and yet achieve large composite shear strains (5-20%) in the hot state (above SMP T g).

Basic materials and structures aspects for hypersonic transport vehicles (HTV)

NASA Astrophysics Data System (ADS)

Steinheil, E.; Uhse, W.

A Mach 5 transport design is used to illustrate structural concepts and criteria for materials selections and also key technologies that must be followed in the areas of computational methods, materials and construction methods. Aside from the primary criteria of low weight, low costs, and conceivable risks, a number of additional requirements must be met, including stiffness and strength, corrosion resistance, durability, and a construction adequate for inspection, maintenance and repair. Current aircraft construction requirements are significantly extended for hypersonic vehicles. Additional consideration is given to long-duration temperature resistance of the airframe structure, the integration of large-volume cryogenic fuel tanks, computational tools, structural design, polymer matrix composites, and advanced manufacturing technologies.

Comparative abrasive wear resistance and surface analysis of dental resin-based materials

PubMed Central

Nayyer, Maleeha; Zahid, Shahreen; Hassan, Syed Hammad; Mian, Salman Aziz; Mehmood, Sana; Khan, Haroon Ahmed; Kaleem, Muhammad; Zafar, Muhammad Sohail; Khan, Abdul Samad

2018-01-01

Objective: The objective of this study was to assess the surface properties (microhardness and wear resistance) of various composites and compomer materials. In addition, the methodologies used for assessing wear resistance were compared. Materials and Methods: This study was conducted using restorative material (Filtek Z250, Filtek Z350, QuiXfil, SureFil SDR, and Dyract XP) to assess wear resistance. A custom-made toothbrush simulator was employed for wear testing. Before and after wear resistance, structural, surface, and physical properties were assessed using various techniques. Results: Structural changes and mass loss were observed after treatment, whereas no significant difference in terms of microhardness was observed. The correlation between atomic force microscopy (AFM) and profilometer and between wear resistance and filler volume was highly significant. The correlation between wear resistance and microhardness were insignificant. Conclusions: The AFM presented higher precision compared to optical profilometers at a nanoscale level, but both methods can be used in tandem for a more detailed and precise roughness analysis. PMID:29657526

A thermoplastic polyimidesulfone. [synthesis of processable and solvent resistant system

NASA Technical Reports Server (NTRS)

St. Clair, T. L.; Yamaki, D. A.

1984-01-01

A polymer system has been prepared which has the excellent thermoplastic properties generally associated with polysulfones, and the solvent resistance and thermal stability of aromatic polyimides. This material, with improved processability over the base polyimide, can be processed in the 260-325 C range in such a manner as to yield high quality, tough unfilled moldings; strong, high-temperature-resistant adhesive bonds; and well consolidated, graphite-fiber-reinforced moldings (composites). The unfilled moldings have physical properties that are similar to aromatic polysulfones which demonstrates the potential as an engineering thermoplastic. The adhesive bonds exhibit excellent retention of initial strength levels even after thermal aging for 5000 hours at 232 C. The graphite-fiber-reinforced moldings have mechanical properties which makes this polymer attractive for the fabrication of structural composites.

Design and analysis of multifunctional structures for embedded electronics in unmanned aerial vehicles

NASA Astrophysics Data System (ADS)

Kothari, Rushabh M.

Multifunctional structures are a new trend in the aerospace industry for the next generation structural design. Many future structures are expected to be something in addition to a load bearing structure. The design and analysis of multifunctional structures combining structural, electrical and thermal functionalities are presented here. The sandwich beam is considered as a starting point for the load bearing structure and then it is modified with a cavity to embed avionics and thermal controls. The embedded avionics inside the load bearing structure would allow weight reduction of the aerospace vehicle due to elimination of separate electronics housing, interconnects, cables etc. The cavity reduces strength of the structure so various reinforcements methods are evaluated. The result of various reinforcements and their effectiveness are presented. The current generation of electronics produce massive amount of heat. In the case of embedded electronics, the excessive heat presents a major challenge to the structural and heat transfer engineers. The embedded nature of electronics prevents the use of the classical heat dissipative methods such as fans and high velocity air flows, etc. The integrated thermal control of the electronics has been designed using passive heat transfer device and highly optimized particulate composite thermal interface material (TIM). The TIMs are used to fill the air gaps and reduce contact resistance between two surfaces, such as electronics and heat dissipators. The efficiency of TIM directly affects the overall heat transfer ability of the integrated thermal control system. The effect of the particles at micron and nano scales are studied for the particulate composite TIM. The thermal boundary resistance study for the particulate composite TIM with nano silica particles is presented in this thesis. The FEA analysis is used to model thermal boundary resistance and compared with the theoretical micromechanics model. The heat pipes are chosen as a part of passive heat transfer device due to their durability and excellent thermal conductivities. The multifunctional system consisting of all above components is modeled for unmanned aerial vehicle (UAV) at subsonic air speeds to demonstrate the validity of the design.

Obtaining valid geologic models from 3-D resistivity inversion of magnetotelluric data at Pahute Mesa, Nevada

USGS Publications Warehouse

Rodriguez, Brian D.; Sweetkind, Donald S.

2015-01-01

The 3-D inversion was generally able to reproduce the gross resistivity structure of the “known” model, but the simulated conductive volcanic composite unit horizons were often too shallow when compared to the “known” model. Additionally, the chosen computation parameters such as station spacing appear to have resulted in computational artifacts that are difficult to interpret but could potentially be removed with further refinements of the 3-D resistivity inversion modeling technique.

Highly efficient phosphorescent organic light-emitting diode with a nanometer-thick Ni silicide/polycrystalline p-Si composite anode.

PubMed

Li, Y Z; Wang, Z L; Luo, H; Wang, Y Z; Xu, W J; Ran, G Z; Qin, G G; Zhao, W Q; Liu, H

2010-07-19

A phosphorescent organic light-emitting diode (PhOLED) with a nanometer-thick (approximately 10 nm) Ni silicide/ polycrystalline p-Si composite anode is reported. The structure of the PhOLED is Al mirror/ glass substrate / Si isolation layer / Ni silicide / polycrystalline p-Si/ V(2)O(5)/ NPB/ CBP: (ppy)(2)Ir(acac)/ Bphen/ Bphen: Cs(2)CO(3)/ Sm/ Au/ BCP. In the composite anode, the Ni-induced polycrystalline p-Si layer injects holes into the V(2)O(5)/ NPB, and the Ni silicide layer reduces the sheet resistance of the composite anode and thus the series resistance of the PhOLED. By adopting various measures for specially optimizing the thickness of the Ni layer, which induces Si crystallization and forms a Ni silicide layer of appropriate thickness, the highest external quantum efficiency and power conversion efficiency have been raised to 26% and 11%, respectively.

Skeletal muscle membrane lipid composition is related to adiposity and insulin action.

PubMed Central

Pan, D A; Lillioja, S; Milner, M R; Kriketos, A D; Baur, L A; Bogardus, C; Storlien, L H

1995-01-01

The cellular basis of insulin resistance is still unknown; however, relationships have been demonstrated between insulin action in muscle and the fatty acid profile of the major membrane structural lipid (phospholipid). The present study aimed to further investigate the hypothesis that insulin action and adiposity are associated with changes in the structural lipid composition of the cell. In 52 adult male Pima Indians, insulin action (euglycemic clamp), percentage body fat (pFAT; underwater weighing), and muscle phospholipid fatty acid composition (percutaneous biopsy of vastus lateralis) were determined. Insulin action (high-dose clamp; MZ) correlated with composite measures of membrane unsaturation (% C20-22 polyunsaturated fatty acids [r= 0.463, P < 0.001], unsaturation index [r= -0.369, P < 0.01]), a number of individual fatty acids and with delta5 desaturase activity (r= 0.451, P < 0.001). pFAT (range 14-53%) correlated with a number of individual fatty acids and delta5 desaturase activity (r= -0.610, P < 0.0001). Indices of elongase activity (r= -0.467, P < 0.001), and delta9 desaturase activity (r= 0.332, P < 0.05) were also related to pFAT but not insulin action. The results demonstrate that delta5 desaturase activity is independently related to both insulin resistance and obesity. While determining the mechanisms underlying this relationship is important for future investigations, strategies aimed at restoring "normal" enzyme activities, and membrane unsaturation, may have therapeutic importance in the "syndromes of insulin resistance." PMID:8675650

High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Park, Cheol (Inventor); Bryant, Robert George (Inventor); Lowther, Sharon E. (Inventor)

2015-01-01

Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

Evaluation of atomic oxygen resistant protective coatings for fiberglass-epoxy composites in LEO

NASA Technical Reports Server (NTRS)

Rutledge, Sharon K.; Paulsen, Phillip E.; Brady, Joyce A.

1989-01-01

Fiberglass-epoxy composite masts are the prime structural members for the Space Station Freedom solar array. At the altitude where Space Station Freedom will operate, atomic oxygen atoms are the most predominant species. Atomic oxygen is highly reactive and has been shown to oxidize organic and some metallic materials. Tests with random and directed atomic oxygen exposure have shown that the epoxy is removed from the composite exposing brittle glass fibers which could be easily removed from the surface where they could contaminate Space Station Freedom Systems. Protection or fiber containment systems; inorganic based paints, aluminum braid, and a metal coating; were evaluated for resistance to atomic oxygen, vacuum ultraviolet radiation, thermal cycling, and mechanical flexing. All appeared to protect well against atomic oxygen and provide fiber containment except for the single aluminum braid covering. UV radiation resistance was acceptable and in general, thermal cycling and flexure had little to no effect on the mass loss rate for most coatings.

Research and development of weathering resistant bridge steel of Shougang

NASA Astrophysics Data System (ADS)

Yang, Yongda; Wang, Yanfeng; Huang, Leqing; Di, Guobiao; Ma, Changwen; Ma, Qingshen

2017-09-01

To introduce the composition design and mechanical properties and microstructure of the weathering bridge steel which would be used for bridge of Guanting reservoir. We adopt cyclic immersion corrosion test to study corrosion resistance difference of weathering bridge steel and common bridge steel. At the same corrosion time, the weight loss and corrosion rate of weathering bridge steel are lower than the common bridge steel's. Testing phase composition of rust layer by X-ray diffraction, two kinds of test steel's rust layer is mainly composed of Goethite and Fe3O4 and Fe2O3. At the same corrosion time, the percentage composition of goethite in rust layer of weathering bridge steel are significantly higher than common bridge steel's, the higher goethite content is, the compacter rust layer structure is. The compact rust layer would prevent the water and air passing the rust layer, and then preventing the further corrosion reaction, improving the corrosion resistance performance of weathering bridge steel.

Advanced Constituents and Processes for Ceramic Composite Engine Components

NASA Technical Reports Server (NTRS)

Yun, H. M.; DiCarlo, J. A.; Bhatt, R. T.

2004-01-01

The successful replacement of metal alloys by ceramic matrix composites (CMC) in hot-section engine components will depend strongly on optimizing the processes and properties of the CMC microstructural constituents so that they can synergistically provide the total CMC system with improved temperature capability and with the key properties required by the components for long-term structural service. This presentation provides the results of recent activities at NASA aimed at developing advanced silicon carbide (Sic) fiber-reinforced hybrid Sic matrix composite systems that can operate under mechanical loading and oxidizing conditions for hundreds of hours at 2400 and 2600 F, temperatures well above current metal capability. These SiC/SiC composite systems are lightweight (-30% metal density) and, in comparison to monolithic ceramics and carbon fiber-reinforced ceramic composites, are able to reliably retain their structural properties for long times under aggressive engine environments. It is shown that the improved temperature capability of the SiC/SiC systems is related first to the NASA development of the Sylramic-iBN Sic fiber, which displays high thermal stability, creep resistance, rupture resistance, and thermal conductivity, and possesses an in-situ grown BN surface layer for added environmental durability. This fiber is simply derived from Sylramic Sic fiber type that is currently produced at ATK COI Ceramics. Further capability is then derived by using chemical vapor infiltration (CVI) to form the initial portion of the hybrid Sic matrix. Because of its high creep resistance and thermal conductivity, the CVI Sic matrix is a required base constituent for all the high temperature SiC/SiC systems. By subsequently thermo- mechanical-treating the CMC preform, which consists of the S ylramic-iBN fibers and CVI Sic matrix, process-related defects in the matrix are removed, further improving matrix and CMC creep resistance and conductivity.

Microstructures, Mechanical Properties, and Wear Resistances of Thixoextruded SiCp/WE43 Magnesium Matrix Composites

NASA Astrophysics Data System (ADS)

Chen, Qiang; Chen, Gang; Han, Fei; Xia, Xiangsheng; Wu, Yang

2017-07-01

Near-net shaping of Mg-RE alloy matrix composites has received increasing attention. In this work, stir casting followed by extrusion was adopted to fabricate Mg-RE alloy (WE43) matrix composites reinforced by micron-sized SiC particles. The microstructural evolutions of SiCp/WE43 composites partially remelted from as-cast and extruded states were studied. Furthermore, the thixoformability of SiCp/WE43 composites in different states was evaluated by thixoextruding a type of double-cup component. The microstructures of as-cast SiCp/WE43 composites were optimized under the comprehensive effects of SiC particles and RE elements. The SiCp/WE43 composite was fully recrystallized during hot extrusion, and the α-Mg matrix consisted of fine equiaxed grains. Although the as-cast SiCp/WE43 composite consisted of satisfactory structures and can be successfully thixoextruded into the final component with good surface quality and no evidence of internal defects, the microstructures, Vickers hardness, tensile mechanical properties, and wear resistance were still inferior to those of the component thixoextruded from extruded composite. Moreover, the thixoextrusion process was analyzed schematically, and an ideal thixoforming process that should contain two stages was proposed.

Risks and reliability of manufacturing processes as related to composite materials for spacecraft structures

NASA Technical Reports Server (NTRS)

Bao, Han P.

1995-01-01

Fabricating primary aircraft and spacecraft structures using advanced composite materials entail both benefits and risks. The benefits come from much improved strength-to-weight ratios and stiffness-to-weight ratios, potential for less part count, ability to tailor properties, chemical and solvent resistance, and superior thermal properties. On the other hand, the risks involved include high material costs, lack of processing experience, expensive labor, poor reproducibility, high toxicity for some composites, and a variety of space induced risks. The purpose of this project is to generate a manufacturing database for a selected number of materials with potential for space applications, and to rely on this database to develop quantitative approaches to screen candidate materials and processes for space applications on the basis of their manufacturing risks including costs. So far, the following materials have been included in the database: epoxies, polycyanates, bismalemides, PMR-15, polyphenylene sulfides, polyetherimides, polyetheretherketone, and aluminum lithium. The first four materials are thermoset composites; the next three are thermoplastic composites, and the last one is is a metal. The emphasis of this database is on factors affecting manufacturing such as cost of raw material, handling aspects which include working life and shelf life of resins, process temperature, chemical/solvent resistance, moisture resistance, damage tolerance, toxicity, outgassing, thermal cycling, and void content, nature or type of process, associate tooling, and in-process quality assurance. Based on industry experience and published literature, a relative ranking was established for each of the factors affecting manufacturing as listed above. Potential applications of this database include the determination of a delta cost factor for specific structures with a given process plan and a general methodology to screen materials and processes for incorporation into the current conceptual design optimization of future spacecrafts as being coordinated by the Vehicle Analysis Branch where this research is being conducted.

Thermal-Mechanical and Thermal Behavior of High-Temperature Structural Materials.

DTIC Science & Technology

1979-12-31

on feveroe side If neceseary at d identify by block number) Absorption coefficient; composites (A1203-BN, BeG-SiC, glass-Ni, ZrC-graphite); crack...Diffusivity of Glass-Ni Composites ’ V1 ’ P H -" ng ._T F,_J’" --Becher and K.S. Mazdiyasn4, -"Aalysis of the Resistance of High-E, Low-E Brittle Composites ...J .S r.PH..-iaeselman, W.M. Su, J.A. Rubin and R. Palicka, r’ ?Dbservations on the Nature of Micro-Cracking in Brittle Composites ,- ..X.L..--K

Polymer matrix composites research at NASA Lewis Research Center

NASA Technical Reports Server (NTRS)

Serafini, T. T.

1982-01-01

The in situ polymerization of monomer reactants (PMR) approach was demonstrated to be a powerful approach for solving many of the processing difficulties associated with the use of high temperature resistant polymers as matrix resins in high performance composites. The PMR-15 polyimide provides the best overall balance of processing characteristics and elevated temperature properties. The excellent properties and commercial availability of composite materials based on PMR-15 led to their acceptance as viable engineering materials. The PMR-15 composites are used to produce a variety of high quality structural components.

Modular fabrication and characterization of complex silicon carbide composite structures Advanced Reactor Technologies (ART) Research Final Report (Feb 2015 – May 2017)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khalifa, Hesham

Advanced ceramic materials exhibit properties that enable safety and fuel cycle efficiency improvements in advanced nuclear reactors. In order to fully exploit these desirable properties, new processing techniques are required to produce the complex geometries inherent to nuclear fuel assemblies and support structures. Through this project, the state of complex SiC-SiC composite fabrication for nuclear components has advanced significantly. New methods to produce complex SiC-SiC composite structures have been demonstrated in the form factors needed for in-core structural components in advanced high temperature nuclear reactors. Advanced characterization techniques have been employed to demonstrate that these complex SiC-SiC composite structures providemore » the strength, toughness and hermeticity required for service in harsh reactor conditions. The complex structures produced in this project represent a significant step forward in leveraging the excellent high temperature strength, resistance to neutron induced damage, and low neutron cross section of silicon carbide in nuclear applications.« less

Advanced Technology Composite Fuselage - Repair and Damage Assessment Supporting Maintenance

NASA Technical Reports Server (NTRS)

Flynn, B. W.; Bodine, J. B.; Dopker, B.; Finn, S. R.; Griess, K. H.; Hanson, C. T.; Harris, C. G.; Nelson, K. M.; Walker, T. H.; Kennedy, T. C.;

Controlled surface segregation leads to efficient coke-resistant nickel/platinum bimetallic catalysts for the dry reforming of methane

DOE PAGES

Li, Lidong; Zhou, Lu; Ould-Chikh, Samy; ...

2015-02-03

Surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. The evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanningmore » transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core–shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. As a result, these catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.« less

Interface structure and properties of CNTs/Cu composites fabricated by electroless deposition and spark plasma sintering

NASA Astrophysics Data System (ADS)

Wang, Hu; Zhang, Zhao-Hui; Hu, Zheng-Yang; Song, Qi; Yin, Shi-Pan

2018-01-01

In this paper, we fabricated a novel copper matrix composites reinforced by carbon nanotubes (CNTs) using electroless deposition (ED) and spark plasma sintering technique. Microstructure, mechanical, electric conductivity, and thermal properties of the CNTs/Cu composites were investigated. The results show that a favorable interface containing C-O and O-Cu bond was formed between CNTs and matrix when the CNTs were coated with nano-Cu by ED method. Thus, we accomplished the uniformly dispersed CNTs in the CNTs/Cu powders and compacted composites, which eventually leads to the enhancement of the mechanical properties of the CNTs/Cu composites in the macro-scale environment. However, the interface structure can hinder the movement of carriers and free electrons and increase the interface thermal resistance, which leads to modest decrease of electrical and thermal conductivity of the CNTs/Cu composites.

Ultra-low temperature curable nano-silver conductive adhesive for piezoelectric composite material

NASA Astrophysics Data System (ADS)

Yan, Chao; Liao, Qingwei; Zhou, Xingli; Wang, Likun; Zhong, Chao; Zhang, Di

2018-01-01

Limited by the low thermal resistance of composite material, ultra-low temperature curable conductive silver adhesive with curing temperature less than 100 °C needed urgently for the surface conduction treatment of piezoelectric composite material. An ultra-low temperature curable nano-silver conductive adhesive with high adhesion strength for the applications of piezoelectric composite material was investigated. The crystal structure of cured adhesive, SEM/EDS analysis, thermal analysis, adhesive properties and conductive properties of different content of nano-silver filler or micron-silver doping samples were studied. The results show that with 60 wt.% nano-silver filler the ultra-low temperature curable conductive silver adhesive had the relatively good conductivity as volume resistivity of 2.37 × 10-4 Ω cm, and good adhesion strength of 5.13 MPa. Minor micron-doping (below 15 wt.%) could improve conductivity, but would decrease other properties. The ultra-low temperature curable nano-silver conductive adhesive could successfully applied to piezoelectric composite material.

Can multi-scale calibrations allow MT-derived resistivities to be used to probe the structure of the deep crust?

NASA Astrophysics Data System (ADS)

Toy, Virginia; Billia, Marco; Easingwood, Richard; Kirilova, Martina; Kluge, Emma; Sauer, Katrina; Sutherland, Rupert; Timms, Nicholas; Townend, John

2017-04-01

Our current knowledge of microstructural and mechanical controls on rock resistivity is such that identical magnetotelluric (MT) anomalies could result from a highly mineralized but extinct shear zone, or from an unmineralized, fluid saturated, active shear zone. In pursuit of the ability to interpret the structure and activity (rather than just the presence) of buried geological structures from electromagnetic data, we are investigating correlations between rock structure and electrical properties of ductile shear zone rocks recovered from the active Alpine Fault Zone, New Zealand. Multi-scale measurements of resistivity exist for this zone: its ductile portions have anomalously high electrical conductivity identified in MT models constructed as part of the South Island Geophysical Transect (SIGHT). Additionally wireline resistivities were measured in situ to 820 m depth during the recent Deep Fault Drilling Project (DFDP-2), and resisistivity of hand samples has been measured at laboratory conditions [Kluge et al., Abstract EGU2017-10139]. In exhumed and borehole samples, the distributions and arrangements of conductivity carriers - graphite, amorphous carbon, and grain boundary pores that would have contained brines or other conductive fluids at depth, have been characterised. These vary systematically according to the total ductile shear strain they have accommodated [Kirilova et al., Abstract EGU2017-5773; Sauer et al., Abstract EGU2017-10485]. Transmission electron microscopy analyses of grain boundaries also indicate that they contain carbon. The next phases of our investigation involve: (i) construction of crustal fluid composition models by quantitative microstructural and compositional/mineralogical mapping of fluid remnants and their solid residues and calibration of these using in situ measurements of fluid composition in DFDP-2 at depths to 820 m; (ii) calculation of resistivities for real microstructures based on electrical properties of the individual component minerals and fluids - for microstructures fully characterised in three-dimensions; (iii) measurement of the effects of dynamic linking of phases during ductile creep of solid rock on complex resistivity of DFDP samples at a range of realistic crustal temperatures and pressures. A particular challenge in this study is to determine appropriate scaling relationships of electrical properties among samples, boreholes, and MT models because dielectric constants of minerals depend on frequency of the imposed current, which varies with scale and, consequently, measurement method. We invite discussion of strategies to overcome this.

On stress-state optimization in steel-concrete composite structures

NASA Astrophysics Data System (ADS)

Brauns, J.; Skadins, U.

2017-10-01

The plastic resistance of a concrete-filled column commonly is given as a sum of the components and taking into account the effect of confinement. The stress state in a composite column is determined by taking into account the non-linear relationship of modulus of elasticity and Poisson’s ratio on the stress level in the concrete core. The effect of confinement occurs at a high stress level when structural steel acts in tension and concrete in lateral compression. The stress state of a composite beam is determined taking into account non-linear dependence on the position of neutral axis. In order to improve the stress state of a composite element and increase the safety of the construction the appropriate strength of steel and concrete has to be applied. The safety of high-stressed composite structures can be achieved by using high-performance concrete (HPC). In this study stress analysis of the composite column and beam is performed with the purpose of obtaining the maximum load-bearing capacity and enhance the safety of the structure by using components with the appropriate strength and by taking into account the composite action. The effect of HPC on the stress state and load carrying capacity of composite elements is analysed.

Dynamic mechanical analysis and organization/storage of data for polymetric materials

NASA Technical Reports Server (NTRS)

Rosenberg, M.; Buckley, W.

1982-01-01

Dynamic mechanical analysis was performed on a variety of temperature resistant polymers and composite resin matrices. Data on glass transition temperatures and degree of cure attained were derived. In addition a laboratory based computer system was installed and data base set up to allow entry of composite data. The laboratory CPU termed TYCHO is based on a DEC PDP 11/44 CPU with a Datatrieve relational data base. The function of TYCHO is integration of chemical laboratory analytical instrumentation and storage of chemical structures for modeling of new polymeric structures and compounds

An improved processible acetylene-terminated polyimide for composites

NASA Technical Reports Server (NTRS)

Landis, A. L.; Naselow, A. B.

1985-01-01

The newest member of a family of thermosetting acetylene-substituted polyimide oligomers is HR600P. This oligomer is the isoimide version of the oligomer known as HR600P and Thermid 600. Although both types of material yield the same heat resistant end products after cure, HR600P has much superior processing characteristics. This attributed to its lower melting temperature (160 + or - 10 C, 320 + or - 20 F) in contrast to 202 C (396 F) for Thermid MC-600, its longer gel time at its processing temperature (16 to 30 minutes bvs 3 minutes), and its excellent solubility in low boiling solvents such as tetrahydrofuran, glymes, or 4:1 methyl ethyl ketone/toluene mixtures. These advantages provide more acceptable coating and impregnation procedures, allow for more complete removal at lower temperatures, provide a longer pot life or working time, and allow composite structure fabrication in conventional autoclaves used for epoxy composite curing. The excellent processing characteristics of HR600P allow its use in large area laminated structures, structural composites, and molding compositions.

Effects of rare earth oxide additive on surface and tribological properties of polyimide composites

NASA Astrophysics Data System (ADS)

Pan, Zihe; Wang, Tianchang; Chen, Li; Idziak, Stefan; Huang, Zhaohui; Zhao, Boxin

2017-09-01

Rare earth oxide La2O3 microparticles-reinforced polyimide (PI) composites (La-PI-Cs) were fabricated, aiming to improve the tribological property of PI. Surface roughness, surface composition, bulk structure, friction force (Ff) and coefficient of friction (COF) at macro/micro preload, and anti-wear performances of La-PI-Cs were studied and compared with neat PI. With La2O3 microparticles, La-PI-Cs showed larger surface roughness, lower surface energy, and higher hydrophobicity than neat PI, and displayed beneficial layered structure different from the compact structure of PI. Owing to these advantages, La-PI-Cs were found to show a 70% reduction in Ff and COF, and a 30% reduction in wear rate, indicating significantly lowered friction and enhanced anti-wear properties after adding La2O3 microparticles. Our research findings demonstrated an easy and low cost method to fabricate polymer composites with low friction and high wear resistance, and help meet the demanding of polymer composites with high tribological performances in broaden applications.

Nondestructive evaluation of composite materials by electrical resistance measurement

NASA Astrophysics Data System (ADS)

Mei, Zhen

This dissertation investigates electrical resistance measurement for nondestructive evaluation of carbon fiber (CF) reinforced polymer matrix composites. The method involves measuring the DC electrical resistance in either the longitudinal or through thickness direction. The thermal history and thermal properties of thermoplastic/CF composites were studied by longitudinal and through-thickness resistance measurements. The resistance results were consistent with differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) results. The resistance measurements gave more information on the melting of the polymer matrix than TMA. They were more sensitive to the glass transition of the polymer matrix than DSC. The through-thickness resistance decreased as autohesion progressed. The activation energy of autohesion was 21.2 kJ/mol for both nylon-6 and polyphenylene sulfide (PPS)/CF composites. Adhesive bonding and debonding were monitored in real-time by measurement of the through-thickness resistance between the adherends in an adhesive joint during heating and subsequent cooling. Debonding occurred during cooling when the pressure or temperature during prior bonding was not sufficiently high. A long heating time below the melting temperature (T m) was found to be detrimental to subsequent PPS adhesive joint development above Tm, due to curing reactions below Tm and consequent reduced mass flow response above Tm. A high heating rate (small heating time) enhanced the bonding more than a high pressure. The longitudinal resistance measurement was used to investigate the effects of temperature and stress on the interface between a concrete substrate and its epoxy/CF composite retrofit. The resistance of the retrofit was increased by bond degradation, whether the degradation was due to heat or stress. The degradation was reversible. Irreversible disturbance in the fiber arrangement occurred slightly as thermal or load cycling occurred, as indicated by the resistance decreasing cycle by cycle. This dissertation also addresses the use of the electrical resistance method to observe thermal and mechanical damage in real time. A temperature increase caused the interlaminar contact resistance to decrease reversibly within each thermal cycle, while thermal damage caused the resistance to decrease abruptly and irreversibly, due to matrix molecular movement and the consequent increase in the chance of fibers of one lamina touching those of an adjacent lamina. The through-thickness volume resistivity irreversibly and gradually decreased upon mechanical damage, which was probably fiber-matrix debonding. Moreover, it reversibly and abruptly increased upon matrix micro-structural change, which occurred reversibly near the peak stress of a stress cycle.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan, Xiaodong; Wu, Hong, E-mail: wuhong927@126.com

Metallic glass composite coatings Ti{sub 45}Cu{sub 41}Ni{sub 9}Zr{sub 5} and Ti{sub 45}Cu{sub 41}Ni{sub 6}Zr{sub 5}Sn{sub 3} (at.%) on a Ti-30Nb-5Ta-7Zr (wt.%) (TNTZ) alloy were prepared by laser cladding. The microstructures of the coatings were characterized by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analyzer (EDXA), and transmission electron microscopy (TEM). Results indicated that the coatings have an amorphous structure embedded with a few nanocrystalline phases and dendrites. A partial substitution of Ni by Sn can improve the glass forming ability of Ti-base metallic glass system, and induce the formation of nano-sized Ni{sub 2}SnTimore » phase during the cyclic laser heating. The tribological behavior of both the substrate and the coatings was investigated in detail. A significant improvement in both the hardness and the wear resistance of the coatings was achieved with the addition of Sn. The relationship between the wear resistance and the microstructures of the coatings was discussed. - Highlights: •Ti-based metallic glass composite coatings were prepared by laser cladding. •The wear resistance is greatly improved by laser cladding of composite coatings. •Substitution of Ni by Sn increases GFA and wear resistance of the coatings. •A good balance of crystalline/amorphous phases improves the wear resistance. •Adhesive wear serves as the dominant wear mechanism of the composite coatings.« less

Continuous esterification to produce biodiesel by SPES/PES/NWF composite catalytic membrane in flow-through membrane reactor: experimental and kinetic studies.

PubMed

Shi, Wenying; He, Benqiao; Cao, Yuping; Li, Jianxin; Yan, Feng; Cui, Zhenyu; Zou, Zhiqun; Guo, Shiwei; Qian, Xiaomin

2013-02-01

A novel composite catalytic membrane (CCM) was prepared from sulfonated polyethersulfone (SPES) and polyethersulfone (PES) blend supported by non-woven fabrics, as a heterogeneous catalyst to produce biodiesel from continuous esterification of oleic acid with methanol in a flow-through mode. A kinetic model of esterification was established based on a plug-flow assumption. The effects of the CCM structure (thickness, area, porosity, etc.), reaction temperature and the external and internal mass transfer resistances on esterification were investigated. The results showed that the CCM structure had a significant effect on the acid conversion. The external mass transfer resistance could be neglected when the flow rate was over 1.2 ml min(-1). The internal mass transfer resistance impacted on the conversion when membrane thickness was over 1.779 mm. An oleic acid conversion kept over 98.0% for 500 h of continuous running. The conversions obtained from the model are in good agreement with the experimental data. Copyright © 2012 Elsevier Ltd. All rights reserved.

Quantitative nondestructive evaluation of materials and structures

NASA Technical Reports Server (NTRS)

Smith, Barry T.

1991-01-01

An experimental investigation was undertaken to quantify damage tolerance and resistance in composite materials impacted using the drop-weight method. Tests were conducted on laminates of several different carbon-fiber composite systems, such as epoxies, modified epoxies, and amorphous and semicrystalline thermoplastics. Impacted composite specimens were examined using destructive and non-destructive techniques to establish the characteristic damage states. Specifically, optical microscopy, ultrasonic, and scanning electron microscopy techniques were used to identify impact induced damage mechanisms. Damage propagation during post impact compression was also studied.

Preparation and Characterization of Ceramizable Kaolin/VMQ and Kaolin/ZB/VMQ Composites

NASA Astrophysics Data System (ADS)

Zhang, X.; Qin, Y.; Pei, Y.; Huang, Z. X.

Ceramizable silicone-based composite was prepared by using methyl vinyl silicone rubber (VMQ) as matrix, calcined Kaolin and zinc borate (ZB) as additives. This composition can form interpenetrating network structures after crosslinking, and then improve heat-resistant properties by firing in air. The results of different formulations were investigated by FTIR. TG-DTG SEM and XRD. It showed that when the temperature above 600°C. the fillers and silicon rubber started to transform from organic to inorganic and internal microstructure became denser.

Nonvolatile RRAM cells from polymeric composites embedding recycled SiC powders.

PubMed

De Girolamo Del Mauro, Anna; Nenna, Giuseppe; Miscioscia, Riccardo; Freda, Cesare; Portofino, Sabrina; Galvagno, Sergio; Minarini, Carla

2014-10-21

Silicon carbide powders have been synthesized from tires utilizing a patented recycling process. Dynamic light scattering, Raman spectroscopy, SEM microscopy, and X-ray diffraction have been carried out to gather knowledge about powders and the final composite structure. The obtained powder has been proven to induce resistive switching in a PMMA polymer-based composite device. Memory effect has been detected in two-terminal devices having coplanar contacts and quantified by read-write-erase measurements in terms of level separation and persistence.

Synthesis of polyoxometalate-loaded epoxy composites

DOEpatents

Anderson, Benjamin J

2014-10-07

The synthesis of a polyoxometalate-loaded epoxy uses a one-step cure by applying an external stimulus to release the acid from the polyoxometalate and thereby catalyze the cure reaction of the epoxy resin. Such polyoxometalate-loaded epoxy composites afford the cured epoxy unique properties imparted by the intrinsic properties of the polyoxometalate. For example, polyoxometalate-loaded epoxy composites can be used as corrosion resistant epoxy coatings, for encapsulation of electronics with improved dielectric properties, and for structural applications with improved mechanical properties.

Distribution and persistence of fecal bacterial populations in liquid and dewatered sludge from a biological treatment plant.

PubMed

Vilanova, Xavier; Blanch, Anicet R

2005-12-01

The changes in composition and structure of fecal coliforms (FC) and enterococci (ENT) populations, as well as the elimination of spores of sulphite-reducing bacteria (SRB), were compared between municipal sewage and their derived sludge in a biological treatment plant in order to determine any selective reduction or adsorption to sludge during the treatment process. Additionally, the persistence of antibiotic-resistant enterococcal populations in two kinds of sludge was also considered to evaluate their potential elimination in the treatment process. Microbial indicators, vancomycin-resistant and erythromycin-resistant enterococci were enumerated. The structure and composition of FC and ENT populations were determined by biochemical fingerprinting and clustering analyses. Raw and treated sewage showed a concentration of FC 1 log unit higher than ENT and nearly 2 log units higher than spores of SRB. However, the three studied indicators showed similar concentrations in both types of sludge. Consequently, FC were eliminated in higher proportion than ENT and spores of SRB in sludge. FC and ENT populations showed high diversity and similarity population indexes for all kinds of samples. Antibiotic-resistant enterococci persisted in a similar proportion in respect to total enterococci not only in treated sewage but also in sludge. The persistence of antibiotic-resistant strains in sludge as well as in treated sewage should be considered if they are used for land disposal or for water reutilization, respectively.

Preparation of Conductive Polymer Graphite (PG) Composites

NASA Astrophysics Data System (ADS)

Munirah Abdullah, Nur; Saddam Kamarudin, M.; Rus, Anika Zafiah M.; Abdullah, M. F. L.

2017-08-01

The preparation of conductive polymer graphite (PG) composites thin film is described. The thickness of the PG composites due to slip casting method was set approximately ~0.1 mm. The optical microscope (OM) and fourier transform infra-red spectroscopy (FTIR) has been operated to distinguish the structure-property relationships scheme of PG composites. It shows that the graphite is homogenously dispersed in polymer matrix composites. The electrical characteristics of the PG composite were measured at room temperature and the electrical conductivity (σ) was discovered with respect of its resistivity (Ω). By achieving conductivity of 103 S/m, it is proven that at certain graphite weight loading (PG20, PG25 and PG30) attributes to electron pathway in PG composites.

Surface characterization and corrosion behavior of calcium phosphate-base composite layer on titanium and its alloys via plasma electrolytic oxidation: A review paper.

PubMed

Rafieerad, A R; Ashra, M R; Mahmoodian, R; Bushroa, A R

2015-12-01

In recent years, calcium phosphate-base composites, such as hydroxyapatite (HA) and carbonate apatite (CA) have been considered desirable and biocompatible coating layers in clinical and biomedical applications such as implants because of the high resistance of the composites. This review focuses on the effects of voltage, time and electrolytes on a calcium phosphate-base composite layer in case of pure titanium and other biomedical grade titanium alloys via the plasma electrolytic oxidation (PEO) method. Remarkably, these parameters changed the structure, morphology, pH, thickness and crystallinity of the obtained coating for various engineering and biomedical applications. Hence, the structured layer caused improvement of the biocompatibility, corrosion resistance and assignment of extra benefits for Osseo integration. The fabricated layer with a thickness range of 10 to 20 μm was evaluated for physical, chemical, mechanical and tribological characteristics via XRD, FESEM, EDS, EIS and corrosion analysis respectively, to determine the effects of the applied parameters and various electrolytes on morphology and phase transition. Moreover, it was observed that during PEO, the concentration of calcium, phosphor and titanium shifts upward, which leads to an enhanced bioactivity by altering the thickness. The results confirm that the crystallinity, thickness and contents of composite layer can be changed by applying thermal treatments. The corrosion behavior was investigated via the potentiodynamic polarization test in a body-simulated environment. Here, the optimum corrosion resistance was obtained for the coating process condition at 500 V for 15 min in Ringer solution. This review has been summarized, aiming at the further development of PEO by producing more adequate titanium-base implants along with desired mechanical and biomedical features. Copyright © 2015 Elsevier B.V. All rights reserved.

Structure dependent electrical properties of Ni-Mg-Cu nano ferrites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choudhari, Nagabhushan J., E-mail: nagabhushanchoudhari@gmail.com; Kakati, Sushanth S.; Hiremath, Chidanandayya S.

2016-05-06

Nano ferrites with the general chemical formula Ni{sub 0.5}Mg{sub x}Cu{sub 1-x} Fe{sub 2}O{sub 4} were synthesized by chemical route. They were characterized by x-ray diffraction by powder method. The diffraction patterns confirm the formation of single phase ferrites. The particle size is calculated by Scherrer formula which varies between 20nm to 60nm. DC resistivity was measured as a function of composition from room temperature to 700{sup o} C by two probe method. These ferrites show higher resistivity than those synthesized by ceramic method, due to control over composition and morphology. This leads to the elimination of domain wall resonance somore » that the materials can work at higher frequencies. AC resistivity was measured as a function of frequency at room temperature. Dielectric dispersion obeys Maxwell - Wagner model, in accordance with Koop’s phenomenological theory. The variation of loss angle follows the variation of ac resistivity with frequency and composition. The change in ac conductivity with frequency obeys the power law σ{sub a} = B.ω{sup n}. Such a behavior suggests that conductivity is due to polarons in all the samples.« less

PEG-PE/clay composite carriers for doxorubicin: Effect of composite structure on release, cell interaction and cytotoxicity.

PubMed

Kohay, Hagay; Sarisozen, Can; Sawant, Rupa; Jhaveri, Aditi; Torchilin, Vladimir P; Mishael, Yael G

2017-06-01

A novel drug delivery system for doxorubicin (DOX), based on organic-inorganic composites was developed. DOX was incorporated in micelles (M-DOX) of polyethylene glycol-phosphatidylethanolamine (PEG-PE) which in turn were adsorbed by the clay, montmorillonite (MMT). The nano-structures of the PEG-PE/MMT composites of LOW and HIGH polymer loadings were characterized by XRD, TGA, FTIR, size (DLS) and zeta measurements. These measurements suggest that for the LOW composite a single layer of polymer intercalates in the clay platelets and the polymer only partially covers the external surface, while for the HIGH composite two layers of polymer intercalate and a bilayer may form on the external surface. These nanostructures have a direct effect on formulation stability and on the rate of DOX release. The release rate was reversely correlated with the degree of DOX interaction with the clay and followed the sequence: M-DOX>HIGH formulation>LOW formulation>DOX/MMT. Despite the slower release from the HIGH formulation, its cytotoxicity effect on sensitive cells was as high as the "free" DOX. Surprisingly, the LOW formulation, with the slowest release, demonstrated the highest cytotoxicity in the case of Adriamycin (ADR) resistant cells. Confocal microscopy images and association tests provided an insight into the contribution of formulation-cell interactions vs. the contribution of DOX release rate. Internalization of the formulations was suggested as a mechanism that increases DOX efficiency, particularly in the ADR resistant cell line. The employment of organic-inorganic hybrid materials as drug delivery systems, has not reached its full potential, however, its functionality as an efficient tunable release system was demonstrated. DOX PEG-PE/clay formulations were design as an efficient drug delivery system. The main aim was to develop PEG-PE/clay formulations of different structures based on various PEG-PE/clay ratios in order to achieve tunable release rates, to control the external surface characteristics and formulation stability. The formulations showed significantly higher toxicity in comparison to "free" DOX, explained by formulation internalization. For each cell line tested, sensitive and ADR resistant, a different formulation structure was found most efficient. The potential of PEG-PE/clay-DOX formulations to improve DOX administration efficacy was demonstrated and should be further explored and implemented for other cancer drugs and cells. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Application of optical interferometric techniques for non-destructive evaluation of novel "green" composite materials

NASA Astrophysics Data System (ADS)

Pagliarulo, Vito; Russo, Pietro; Bianco, Vittorio; Ferraro, Pietro; Simeoli, Giorgio; Cimino, Francesca; Ruggiero, Berardo

2018-04-01

Nowadays the use of advanced composite materials in aeronautics, both civil and military, in automotive and in sport applications, citing some, is well established. The characteristics of composite materials in terms of weight, fatigue resistance and corrosion resistance make them competitive with respect to conventional ones. On the other side, the fabrication process of the most employed composites reinforced by carbon fibers or glass fibers, needs of complex steps that not always are environmental complaisant. Moreover, such fibers are not themselves "green". For these reasons, in the last decades, the use of natural reinforcing fibers has gained an increasing attention allowing the development of new materials with the same advantages of composite systems but respecting the environment. Furthermore, such materials for their structural complexity are not always compatible with the use of standard non-destructive evaluation as the ultrasounds methods. In this work the efficiency of the employment of optical interferometric techniques as nondestructive evaluation methods in full field modality is proved on novel "green" composite materials. In particular, Electronic Speckle Pattern Interferometry has been tested on different kinds of specimens after flexural tests.

A new discrete-element approach for the assessment of the seismic resistance of composite reinforced concrete-masonry buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calio, I.; Cannizzaro, F.; Marletta, M.

2008-07-08

In the present study a new discrete-element approach for the evaluation of the seismic resistance of composite reinforced concrete-masonry structures is presented. In the proposed model, unreinforced masonry panels are modelled by means of two-dimensional discrete-elements, conceived by the authors for modelling masonry structures, whereas the reinforced concrete elements are modelled by lumped plasticity elements interacting with the masonry panels through nonlinear interface elements. The proposed procedure was adopted for the assessment of the seismic response of a case study confined-masonry building which was conceived to be a typical representative of a wide class of residential buildings designed to themore » requirements of the 1909 issue of the Italian seismic code and widely adopted in the aftermath of the 1908 earthquake for the reconstruction of the cities of Messina and Reggio Calabria.« less

A new discrete-element approach for the assessment of the seismic resistance of composite reinforced concrete-masonry buildings

NASA Astrophysics Data System (ADS)

Caliò, I.; Cannizzaro, F.; D'Amore, E.; Marletta, M.; Pantò, B.

2008-07-01

In the present study a new discrete-element approach for the evaluation of the seismic resistance of composite reinforced concrete-masonry structures is presented. In the proposed model, unreinforced masonry panels are modelled by means of two-dimensional discrete-elements, conceived by the authors for modelling masonry structures, whereas the reinforced concrete elements are modelled by lumped plasticity elements interacting with the masonry panels through nonlinear interface elements. The proposed procedure was adopted for the assessment of the seismic response of a case study confined-masonry building which was conceived to be a typical representative of a wide class of residential buildings designed to the requirements of the 1909 issue of the Italian seismic code and widely adopted in the aftermath of the 1908 earthquake for the reconstruction of the cities of Messina and Reggio Calabria.

Triphasic Composite And Method Of Making Same

DOEpatents

Kear, Bernard H.; Sadangi, Rajendra K.; McCandlish, Larry E.; Voronov, Oleg

2000-07-18

A method for fabricating a triphasic composite such as a WC/Co/diamond composite with a high volume fraction of diamond in a WC/Co matrix. The method involves sintering of a WC/Co powder compact to develop a porous preform, which displays some rigidity and strength, infiltrating the porous preform with a controlled distribution of carbon, and high pressure/high temperature treatment of the carbon-containing WC/Co preform to transform the carbon to diamond. The distribution of diamond in the composite can be functionally graded to provide a WC/Co core and a diamond-enriched surface, wherein all three phases form an interconnected structure in three dimensions. Such a tricontinuous structure combines high strength and toughness with superior wear resistance, making it attractive for applications in machine tools and drill bits.

Self-folding with shape memory composites at the millimeter scale

NASA Astrophysics Data System (ADS)

Felton, S. M.; Becker, K. P.; Aukes, D. M.; Wood, R. J.

2015-08-01

Self-folding is an effective method for creating 3D shapes from flat sheets. In particular, shape memory composites—laminates containing shape memory polymers—have been used to self-fold complex structures and machines. To date, however, these composites have been limited to feature sizes larger than one centimeter. We present a new shape memory composite capable of folding millimeter-scale features. This technique can be activated by a global heat source for simultaneous folding, or by resistive heaters for sequential folding. It is capable of feature sizes ranging from 0.5 to 40 mm, and is compatible with multiple laminate compositions. We demonstrate the ability to produce complex structures and mechanisms by building two self-folding pieces: a model ship and a model bumblebee.

Thermally Stable and Electrically Conductive, Vertically Aligned Carbon Nanotube/Silicon Infiltrated Composite Structures for High-Temperature Electrodes.

PubMed

Zou, Qi Ming; Deng, Lei Min; Li, Da Wei; Zhou, Yun Shen; Golgir, Hossein Rabiee; Keramatnejad, Kamran; Fan, Li Sha; Jiang, Lan; Silvain, Jean-Francois; Lu, Yong Feng

2017-10-25

Traditional ceramic-based, high-temperature electrode materials (e.g., lanthanum chromate) are severely limited due to their conditional electrical conductivity and poor stability under harsh circumstances. Advanced composite structures based on vertically aligned carbon nanotubes (VACNTs) and high-temperature ceramics are expected to address this grand challenge, in which ceramic serves as a shielding layer protecting the VACNTs from the oxidation and erosive environment, while the VACNTs work as a conductor. However, it is still a great challenge to fabricate VACNT/ceramic composite structures due to the limited diffusion of ceramics inside the VACNT arrays. In this work, we report on the controllable fabrication of infiltrated (and noninfiltrated) VACNT/silicon composite structures via thermal chemical vapor deposition (CVD) [and laser-assisted CVD]. In laser-assisted CVD, low-crystalline silicon (Si) was quickly deposited at the VACNT subsurfaces/surfaces followed by the formation of high-crystalline Si layers, thus resulting in noninfiltrated composite structures. Unlike laser-assisted CVD, thermal CVD activated the precursors inside and outside the VACNTs simultaneously, which realized uniform infiltrated VACNT/Si composite structures. The growth mechanisms for infiltrated and noninfiltrated VACNT/ceramic composites, which we attributed to the different temperature distributions and gas diffusion mechanism in VACNTs, were investigated. More importantly, the as-farbicated composite structures exhibited excellent multifunctional properties, such as excellent antioxidative ability (up to 1100 °C), high thermal stability (up to 1400 °C), good high velocity hot gas erosion resistance, and good electrical conductivity (∼8.95 Sm -1 at 823 K). The work presented here brings a simple, new approach to the fabrication of advanced composite structures for hot electrode applications.

Electro-mechanical characterization of structural supercapacitors

NASA Astrophysics Data System (ADS)

Gallagher, T.; LaMaster, D.; Ciocanel, C.; Browder, C.

2012-04-01

The paper presents electrical and mechanical properties of structural supercapacitors and discusses limitations associated with the approach taken for the electrical properties evaluation. The structural supercapacitors characterized in this work had the electrodes made of carbon fiber weave, separator made of several cellulose based products, and the solid electrolyte made as PEGDGE based polymer blend. The reported electrical properties include capacitance and leakage resistance; the former was measured using cyclic voltammetry. Mechanical properties have been evaluated thorough tensile and three point bending tests performed on structural supercapacitor coupons. The results indicate that the separator material plays an important role on the electrical as well as mechanical properties of the structural capacitor, and that Celgard 3501 used as separator leads to most benefits for both mechanical and electrical properties. Specific capacitance and leakage resistance as high as 1.4kF/m3 and 380kΩ, respectively, were achieved. Two types of solid polymer electrolytes were used in fabrication, with one leading to higher and more consistent leakage resistance values at the expense of a slight decrease in specific capacitance when compared to the other SPE formulation. The ultimate tensile strength and modulus of elasticity of the developed power storage composite were evaluated at 466MPa and 18.9MPa, respectively. These values are 58% and 69% of the tensile strength and modulus of elasticity values measured for a single layer composite material made with the same type of carbon fiber and with a West System 105 epoxy instead of solid polymer electrolyte.

Tailored interphase structure for improved strength and energy absorption of composites

NASA Astrophysics Data System (ADS)

Gao, Xiao

Fiber reinforced polymeric composites are lightweight, high-strength and high impact-resistant materials used widely for various applications. It has been shown that the mechanical performance of composites are dependent on the interphase, a three-dimensional region of nanometer size in the vicinity of the fiber-matrix boundary that possesses properties different from those of either the fiber reinforcement or the matrix resin and governs the load transfer from matrix to fiber. This research conducts a systematic study on glass fiber-epoxy interphase structure by tailoring adhesion between constituents and the creation of textures to control strength and energy absorption through mechanical interlocking between glass fiber and epoxy matrix. Our objective is to establish the foundation for microstructural design and optimization of the composite's structural and impact performance. Two ways of roughening the glass fiber surface have been studied to create the mechanical interlocking between fiber and resin; the first technique involves forming in-situ islands on the glass fiber surface by using silane blends of Glycidoxypropyltrimethoxy silane (GPS) and Tetraethoxy silane (TEOS); the second technique applies a silane coupling agents based sizing with the incorporation of silica nanoparticles (Ludox TMA, 22 nm) onto the fiber surface. The microdroplet test was selected to characterize the influence of adhesion and mechanical interlocking effects on interphase properties of different sizing sized glass fiber reinforced epoxy systems. A suitable data reduction scheme enables the strength and specified energy absorbed due to debonding, dynamic sliding, and quasi-static sliding to be quantified. In order to validate the effect of tailored interphase structure, which is induced by creating mechanical interlocking between fiber and resin, on macroscopic composite properties, composite panels were made from these four different sizing sized glass fibers and tested using the punch shear test. The composite panel made from the hybrid sizing sized glass fiber exhibited improved strength and energy absorption consistent with the trends in micromechanical measurements. Through all failure stages under macromechanical testing, hybrid sizing sized glass fiber/epoxyamine composite panel shows an increase in the strength and total energy absorption by 13% and 26%, respectively, compared to the compatible sizing sized baseline. Both micromechanical and macromechanical tests demonstrate the significant influence of tailoring the interphase structure on improving the impact performance of the composites. The hybrid sizing with the incorporation of nanoparticles, in particular, can greatly improve the impact resistance (i.e. energy absorption) of composites without sacrificing its structural performance (i.e. strength).

Autonomous sensing of composites with carbon nanotubes for structural health monitoring

NASA Astrophysics Data System (ADS)

Liu, Yingtao; Yekani Fard, Masoud; Rajadas, Abhishek; Chattopadhyay, Aditi

2012-04-01

The development of structural health monitoring techniques leads to the integration of sensing capability within engineering structures. This study investigates the application of multi walled carbon nanotubes in polymer matrix composites for autonomous damage detection through changes in electrical resistance. The autonomous sensing capabilities of fiber reinforced nanocomposites are studied under multiple loading conditions including tension loads. Single-lap joints with different joint lengths are tested. Acoustic emission sensing is used to validate the matrix crack propagation. A digital image correlation system is used to measure the shear strain field of the joint area. The joints with 1.5 inch length have better autonomous sensing capabilities than those with 0.5 inch length. The autonomous sensing capabilities of nanocomposites are found to be sensitive to crack propagation and can revolutionize the research on composite structural health management in the near future.

Thermoelectric generator based on composites obtained by sintering of detonation nanodiamonds

NASA Astrophysics Data System (ADS)

Eidelman, E. D.; Meilakhs, A. P.; Semak, B. V.; Shakhov, F. M.

2017-11-01

A model of a thermoelectric generator is proposed, in which composite materials obtained by sintering diamond nanoparticles are used as the main component. To increase the useful conversion of heat into electric current, it is proposed to use the effect of electron drag by ballistic phonons. To reduce the ineffective heat spread, it is proposed to use the effect of thermal resistance of the boundaries between the graphite-like and diamond-like phases of the composite. An experimental confirmation of the existence of an optimal volume ratio between graphite-like and diamond-like phases of the composite is predicted and obtained. The highest achieved value of thermoelectric coefficient in the actual structure is 80 µV K-1 (which means 20 times increase compared to that of composites not of the optimal structure), with a thermal conductivity of 50 W m-1 K-1. These results were obtained with constant electrical conductivity. The combined influence of these two effects in case of the ideal composite structure should result in an increase of the thermoelectric efficiency parameter by three orders of magnitude.

Reflexive aerostructures: increased vehicle survivability

NASA Astrophysics Data System (ADS)

Margraf, Thomas W.; Hemmelgarn, Christopher D.; Barnell, Thomas J.; Franklin, Mark A.

2007-04-01

Aerospace systems stand to benefit significantly from the advancement of reflexive aerostructure technologies for increased vehicle survivability. Cornerstone Research Group Inc. (CRG) is developing lightweight, healable composite systems for use as primary load-bearing aircraft components. The reflexive system is comprised of piezoelectric structural health monitoring systems, localized thermal activation systems, and lightweight, healable composite structures. The reflexive system is designed to mimic the involuntary human response to damage. Upon impact, the structural health monitoring system will identify the location and magnitude of the damage, sending a signal to a discrete thermal activation control system to resistively heat the shape memory polymer (SMP) matrix composite above activation temperature, resulting in localized shape recovery and healing of the damaged areas. CRG has demonstrated SMP composites that can recover 90 percent of flexural yield stress and modulus after postfailure healing. During the development, CRG has overcome issues of discrete activation, structural health monitoring integration, and healable resin systems. This paper will address the challenges associated with development of a reflexive aerostructure, including integration of structural health monitoring, discrete healing, and healable shape memory resin systems.

Bond-slip detection of concrete-encased composite structure using electro-mechanical impedance technique

NASA Astrophysics Data System (ADS)

Liang, Yabin; Li, Dongsheng; Parvasi, Seyed Mohammad; Kong, Qingzhao; Lim, Ing; Song, Gangbing

2016-09-01

Concrete-encased composite structure is a type of structure that takes the advantages of both steel and concrete materials, showing improved strength, ductility, and fire resistance compared to traditional reinforced concrete structures. The interface between concrete and steel profiles governs the interaction between these two materials under loading, however, debonding damage between these two materials may lead to severe degradation of the load transferring capacity which will affect the structural performance significantly. In this paper, the electro-mechanical impedance (EMI) technique using piezoceramic transducers was experimentally investigated to detect the bond-slip occurrence of the concrete-encased composite structure. The root-mean-square deviation is used to quantify the variations of the impedance signatures due to the presence of the bond-slip damage. In order to verify the validity of the proposed method, finite element model analysis was performed to simulate the behavior of concrete-steel debonding based on a 3D finite element concrete-steel bond model. The computed impedance signatures from the numerical results are compared with the results obtained from the experimental study, and both the numerical and experimental studies verify the proposed EMI method to detect bond slip of a concrete-encased composite structure.

An in vitro investigation of wear resistance and hardness of composite resins

PubMed Central

Cao, Liqun; Zhao, Xinyi; Gong, Xu; Zhao, Shouliang

2013-01-01

Purpose: The aim of the present study was to investigate the wear resistance and hardness of five kinds of composite resins. Materials and Methods: Sixty-five specimens were fabricated with one nano-hybrid (Charisma Diamond), two micro-hybrid (3MZ250, Clearfil AP-X) and two packable (3MP60, Surefil) composite resins, according to a randomized complete block design (n=13, 8 for wear test; 5 for hardness test). The composites were filled in a rectangular mold, and light polymerization. After storage in 37°C deionized water for 24h, all specimens were tested with a custom-made toothbrush machine with a stainless-steel ball as antagonist (3N loads, 1Hz, 6×105 cycles) immersed in calcium fluoride slurry. Wear volume, hardness and surface structure of each tested material was examined by a three-dimensional non-contact optical profilometer, Vickers indentation technique and scanning electron microscope. Results: The volume loss ranked from least to most as follows: Charisma Diamond, P60, Z250, Clearfil AP-X and Surefil. Regarding hardness, the rank from highest to lowest as follows: Clearfil AP-X, P60, Surefil, Z250, Charisma Diamond. The interactions between wear resistance and microhardness were not significant. Conclusions: The custom-made machine is considered suitable to simulate sliding of an antagonist cusp on an opposing occlusal composite restoration. Nanofilled composite may have superior wear compared to other composite resins. PMID:23844265

High temperature static strain measurement with an electrical resistance strain gage

NASA Technical Reports Server (NTRS)

Lei, Jih-Fen

1992-01-01

An electrical resistance strain gage that can supply accurate static strain measurement for NASP application is being developed both in thin film and fine wire forms. This gage is designed to compensate for temperature effects on substrate materials with a wide range of thermal expansion coefficients. Some experimental results of the wire gage tested on one of the NASP structure materials, i.e., titanium matrix composites, are presented.

Production and application of chemical fibers with special properties for manufacturing composite materials and goods of different usage

NASA Technical Reports Server (NTRS)

Levit, R.

1993-01-01

The development of modern technologies demands the creation of new nonmetallic, fibrous materials with specific properties. The fibers and materials developed by NII 'Chimvolokno', St. Petersburg, can be divided into two groups. The first group includes heat-resistant fibers, fire-resistant fibers, thermotropic fibers, fibers for medical application, and textile structures. The second group contains refractory fibers, chemoresistant and antifriction fibers, fibers on the basis of polyvinyl alcohol, microfiltering films, and paperlike and nonwoven materials. In cooperation with NPO 'Chimvolokno' MYTITSHI, we developed and started producing heat-resistant high-strength fibers on the base of polyhetarearilin and aromatic polyimides (SVM and terlon); heat-resistant fibers on the base of polyemede (aramid); fire-retardant fibers (togilen); chemoresistant and antifriction fibers on the basis of homo and copolymers of polytetrafluoroethylene (polyfen and ftorin); and water soluble, acetylated, and high-modulus fibers from polyvinyl alcohol (vylen). Separate reports will deal with textile structures and thermotropic fibers, as well as with medical fibers. One of the groups of refractory fibers carbon fibers (CF) and the corresponding paperlike nonwoven materials are discussed in detail. Also, composite materials (CM) and their base, which is the subject of the author's research since 1968, is discussed.

Composition for use in high-temperature hydrogen-fluorine environments and method for making the composition

DOEpatents

Kovach, L.; Holcombe, C.E.

1980-08-22

The present invention relates to a composition particularly suitable for use as structural components subject to high-temperature environments containing gaseous hydrogen and fluorine. The composition of the present invention consists essentially of lanthanum hexaboride-molybdenum diboride with dispersed silicon. The composition is formed by hot pressing a powder mixture of lanthanum hexaboride as the major constituent and molybdenum disilicide. This composition exhibits substantial resistance to thermal shock and corrosion in environments containing hydrogen and fluorine gases at material surface temperatures up to about 1850/sup 0/K. Upon exposure of the hot-pressed composition to high-temperature environments containing fluorine gases, a highly protective layer of lanthanum trifluoride containing dispersed molybdenum is formed on exposed surfaces of the composition.

Composition for use in high-temperature hydrogen-fluorine environments and method for making the composition

DOEpatents

Kovach, Louis; Holcombe, Cressie E.

1982-01-01

The present invention relates to a composition particularly suitable for as structural components subject to high-temperature environments containing gaseous hydrogen and fluorine. The composition of the present invention consists essentially of lanthanum hexaboride-molybdenum diboride with dispersed silicon. The composition is formed by hot pressing a powder mixture of lanthanum hexaboride as the major constituent and molybdenum disilicide. This composition exhibits substantial resistance to thermal shock and corrosion in environments containing hydrogen and fluorine gases at material surface temperatures up to about 1850.degree. K. Upon exposure of the hot-pressed composition to high-temperature environments containing fluorine gases, a highly protective layer of lanthanum trifluoride containing dispersed molybdenum is formed on exposed surfaces of the composition.

Tribological properties and lubrication mechanism of in situ graphene-nickel matrix composite impregnated with lubricating oil

NASA Astrophysics Data System (ADS)

Lei, Yu; Du, Jinfang; Pang, Xianjuan; Wang, Haizhong; Yang, Hua; Jiang, Jinlong

2018-05-01

A solid-liquid synergetic lubricating system has been designed to develop a novel self-lubricating nickel matrix composite. The graphene-nickel (G-Ni) matrix composite with porous structure was fabricated by in situ growing graphene in bulk nickel using a powder metallurgy method. The porous structures of the composite were used to store polyalphaolefin (PAO) oil for self-lubricating. It is found that the G-Ni matrix composite under oil lubrication condition exhibited superior tribological properties as compared to pure nickel and the composite under dry sliding condition. The prestored oil was released from pores to the sliding surface forming a lubricating oil film during friction process. This lubricating oil film can protect the worn surface from severe oxidation, and help the formation and transfer of a carbon-based solid tribofilm derived from graphene and lubricating oil. This solid (graphene)-liquid (oil) synergistic lubricating mechanism is responsible for the reduction of friction coefficient and improvement of wear resistance of the in situ fabricated G-Ni matrix composite.

Characterization of the staphylococcal cassette chromosome composite island of Staphylococcus haemolyticus SH32, a methicillin-resistant clinical isolate from China.

PubMed

Yu, Dongliang; Pi, Borui; Chen, Yan; Wang, Yanfei; Ruan, Zhi; Otto, Michael; Yu, Yunsong

2014-01-01

Staphylococcal cassette chromosome (SCC) elements contribute considerably to virulence and resistance to antibiotic agents in staphylococci. SCC elements in coagulase-negative staphylococci (CoNS) are highly diverse and there is evidence suggesting that they serve as a reservoir for antibiotic resistance genes in methicillin-resistant Staphylococcus aureus (MRSA). However, only a small number of SCC elements have been characterized in CoNS and their exact roles in the emergence and evolution of MRSA remain to be demonstrated. Here, we determined the structure of an SCC composite island (CISH32) found in the clinical Staphylococcus haemolyticus isolate SH32 by whole-genome DNA sequencing. CISH32 was 48 kb in length and mainly composed of two imperfect SCC elements, namely (i) a ΨSCCmec(SH32) part containing a class C1 mec gene complex but lacking ccr genes and (ii) a SCCSH32 part with a ccrA5B3 gene complex but lacking mec genes. In addition, CISH32 contained a type III restriction-modification system and several resistance loci, for example genes conferring resistance to cadmium and arsenic. ΨSCCmec(SH32) is almost entirely identical to a pseudo SCCmec element found in S. haemolyticus WCH1 and shares pronounced sequence similarity to a ΨSCCmec element of S. haemolyticus JCSC1435. However, staphylococci other than S. haemolyticus, including S. aureus and S. epidermidis, contain homologs of SCCSH32 that are more similar to SCCSH32 than those elements found in S. haemolyticus, suggesting that CISH32 of S. haemolyticus SH32 was assembled in recent evolutionary events. Moreover, the composite structure of CISH32 indicates that the detection of class C1 mec and ccrA5B3 gene complexes in S. haemolyticus does not always indicate the existence of a UT9-type SCCmec element, which has remained questionable.

Characterization of the Staphylococcal Cassette Chromosome Composite Island of Staphylococcus haemolyticus SH32, a Methicillin-Resistant Clinical Isolate from China

PubMed Central

Yu, Dongliang; Pi, Borui; Chen, Yan; Wang, Yanfei; Ruan, Zhi; Otto, Michael; Yu, Yunsong

2014-01-01

Staphylococcal cassette chromosome (SCC) elements contribute considerably to virulence and resistance to antibiotic agents in staphylococci. SCC elements in coagulase-negative staphylococci (CoNS) are highly diverse and there is evidence suggesting that they serve as a reservoir for antibiotic resistance genes in methicillin-resistant Staphylococcus aureus (MRSA). However, only a small number of SCC elements have been characterized in CoNS and their exact roles in the emergence and evolution of MRSA remain to be demonstrated. Here, we determined the structure of an SCC composite island (CISH32) found in the clinical Staphylococcus haemolyticus isolate SH32 by whole-genome DNA sequencing. CISH32 was 48 kb in length and mainly composed of two imperfect SCC elements, namely (i) a ΨSCCmec(SH32) part containing a class C1 mec gene complex but lacking ccr genes and (ii) a SCCSH32 part with a ccrA5B3 gene complex but lacking mec genes. In addition, CISH32 contained a type III restriction-modification system and several resistance loci, for example genes conferring resistance to cadmium and arsenic. ΨSCCmec(SH32) is almost entirely identical to a pseudo SCCmec element found in S. haemolyticus WCH1 and shares pronounced sequence similarity to a ΨSCCmec element of S. haemolyticus JCSC1435. However, staphylococci other than S. haemolyticus, including S. aureus and S. epidermidis, contain homologs of SCCSH32 that are more similar to SCCSH32 than those elements found in S. haemolyticus, suggesting that CISH32 of S. haemolyticus SH32 was assembled in recent evolutionary events. Moreover, the composite structure of CISH32 indicates that the detection of class C1 mec and ccrA5B3 gene complexes in S. haemolyticus does not always indicate the existence of a UT9-type SCCmec element, which has remained questionable. PMID:24466348

Self-diagnosis of damage in fibrous composites using electrical resistance measurements

NASA Astrophysics Data System (ADS)

Kang, Ji Ho; Paty, Spandana; Kim, Ran Y.; Tandon, G. P.

2006-03-01

The objective of this research was to develop a practical integrated approach using extracted features from electrical resistance measurements and coupled electromechanical models of damage, for in situ damage detection and sensing in carbon fiber reinforced plastic (CFRP) composite structures. To achieve this objective, we introduced specific known damage (in terms of type, size, and location) into CFRP laminates and established quantitative relationships with the electrical resistance measurements. For processing of numerous measurement data, an autonomous data acquisition system was devised. We also established a specimen preparation procedure and a method for electrode setup. Coupon and panel CFRP laminate specimens with several known damage were tested and post-processed with the measurement data. Coupon specimens with various sizes of artificial delaminations obtained by inserting Teflon film were manufactured and the resistance was measured. The measurement results showed that increase of delamination size led to increase of resistance implying that it is possible to sense the existence and size of delamination. Encouraged by the results of coupon specimens, we implemented the measurement system on panel specimens. Three different quasi-isotropic panels were designed and manufactured: a panel with artificial delamination by inserting Teflon film at the midplane, a panel with artificial delamination by inserting Teflon film between the second and third plies from the surface, and an undamaged panel. The first two panels were designed to determine the feasibility of detecting delamination using the developed measurement system. The third panel had no damage at first, and then three different sizes of holes were drilled at a chosen location. Panels were prepared using the established procedures with six electrode connections on each side making a total of twenty-four electrode connections for a panel. All possible pairs of electrodes were scanned and the resistance was measured for each pair. The measurement results showed the possibility of the established measurement system for an in-situ damage detection method for CFRP composite structures.

Process Optimization of Bismaleimide (BMI) Resin Infused Carbon Fiber Composite

NASA Technical Reports Server (NTRS)

Ehrlich, Joshua W.; Tate, LaNetra C.; Cox, Sarah B.; Taylor, Brian J.; Wright, M. Clara; Faughnan, Patrick D.; Batterson, Lawrence M.; Caraccio, Anne J.; Sampson, Jeffery W.

2013-01-01

Engineers today are presented with the opportunity to design and build the next generation of space vehicles out of the lightest, strongest, and most durable materials available. Composites offer excellent structural characteristics and outstanding reliability in many forms that will be utilized in future aerospace applications including the Commercial Crew and Cargo Program and the Orion space capsule. NASA's Composites for Exploration (CoEx) project researches the various methods of manufacturing composite materials of different fiber characteristics while using proven infusion methods of different resin compositions. Development and testing on these different material combinations will provide engineers the opportunity to produce optimal material compounds for multidisciplinary applications. Through the CoEx project, engineers pursue the opportunity to research and develop repair patch procedures for damaged spacecraft. Working in conjunction with Raptor Resins Inc., NASA engineers are utilizing high flow liquid infusion molding practices to manufacture high-temperature composite parts comprised of intermediate modulus 7 (IM7) carbon fiber material. IM7 is a continuous, high-tensile strength composite with outstanding structural qualities such as high shear strength, tensile strength and modulus as well as excellent corrosion, creep, and fatigue resistance. IM7 carbon fiber, combined with existing thermoset and thermoplastic resin systems, can provide improvements in material strength reinforcement and deformation-resistant properties for high-temperature applications. Void analysis of the different layups of the IM7 material discovered the largest total void composition within the [ +45 , 90 , 90 , -45 ] composite panel. Tensile and compressional testing proved the highest mechanical strength was found in the [0 4] layup. This paper further investigates the infusion procedure of a low-cost/high-performance BMI resin into an IM7 carbon fiber material and the optical, chemical, and mechanical analyses performed.

Radiation-resistant composite for biological shield of personnel

NASA Astrophysics Data System (ADS)

Barabash, D. E.; Barabash, A. D.; Potapov, Yu B.; Panfilov, D. V.; Perekalskiy, O. E.

2017-10-01

This article presents the results of theoretical and practical justification for the use of polymer concrete based on nonisocyanate polyurethanes in biological shield structures. We have identified the impact of ratio: polymer - radiation-resistant filling compound on the durability and protection properties of polymer concrete. The article expounds regression dependence of the change of basic properties of the aforementioned polymer concrete on the absorbed radiation dose rate. Synergy effect in attenuation of radioactivity release in case of conjoint use of hydrogenous polymer base and radiation-resistant powder is also addressed herein.

Slow crack growth in SiC platelet reinforced Al{sub 2}O{sub 3} composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belmonte, M.; Moya, J.S.; Miranzo, P.

1996-05-15

Ceramic matrix composites with enhanced toughness are at present projected for many structural applications such as high temperature components in gas turbine, structures for hypersonic aircraft and bioprosthetic devices. The incorporation of a SiC dispersed second phase in form of whisker or platelets into an alumina matrix has allowed to improve material toughness, thermal shock resistance and R-curve behavior. Recently, considerable interest in the acquisition of slow crack growth (SCG) data for ceramic materials has arisen in order to predict the service lifetime of brittle components. Non-oxide ceramics such as SiC and Si{sub 3}N{sub 4} are extremely resistant to crackmore » growth at low temperatures, whereas oxide ceramics are susceptible to stress corrosion because of the chemical interaction between water and stressed cracks. Up to date, there are not many papers devoted to SCG of SiC whiskers reinforced Al{sub 2}O{sub 3} composites and none about SiC platelets used as reinforcement. The objective of the present work has been to evaluate the slow crack growth in a Al{sub 2}O{sub 3}/SiC-platelet composite by double torsion testing analysis. The results will be compared with those obtained for SiC whisker reinforced Al{sub 2}O{sub 3} composite tested using the same conditions.« less

Electrical/Mechanical Monitoring of Shape Memory Alloy Reinforcing Fibers Obtained by Pullout Tests in SMA/Cement Composite Materials.

PubMed

Kim, Eui-Hyun; Lee, Hyunbae; Kim, Jae-Hwan; Bae, Seung-Muk; Hwang, Heesu; Yang, Heesun; Choi, Eunsoo; Hwang, Jin-Ha

2018-02-22

Self-healing is an essential property of smart concrete structures. In contrast to other structural metals, shape memory alloys (SMAs) offer two unique effects: shape memory effects, and superelastic effects. Composites composed of SMA wires and conventional cements can overcome the mechanical weaknesses associated with tensile fractures in conventional concretes. Under specialized environments, the material interface between the cementitious component and the SMA materials plays an important role in achieving the enhanced mechanical performance and robustness of the SMA/cement interface. This material interface is traditionally evaluated in terms of mechanical aspects, i.e., strain-stress characteristics. However, the current work attempts to simultaneously characterize the mechanical load-displacement relationships synchronized with impedance spectroscopy as a function of displacement. Frequency-dependent impedance spectroscopy is tested as an in situ monitoring tool for structural variations in smart composites composed of non-conducting cementitious materials and conducting metals. The artificial geometry change in the SMA wires is associated with an improved anchoring action that is compatible with the smallest variation in resistance compared with prismatic SMA wires embedded into a cement matrix. The significant increase in resistance is interpreted to be associated with the slip of the SMA fibers following the elastic deformation and the debonding of the SMA fiber/matrix.

Self cleaning coatings for graffiti prevention removal and de-pollution (demo project).

DOT National Transportation Integrated Search

2012-01-01

The primary focus of this report is to demonstrate the suitability of an inorganic polymer composite : coating for transportation related structures. This report presents the results of three field : applications and evaluation of graffiti resistance...

Multiply fully recyclable carbon fibre reinforced heat-resistant covalent thermosetting advanced composites

NASA Astrophysics Data System (ADS)

Yuan, Yanchao; Sun, Yanxiao; Yan, Shijing; Zhao, Jianqing; Liu, Shumei; Zhang, Mingqiu; Zheng, Xiaoxing; Jia, Lei

2017-03-01

Nondestructive retrieval of expensive carbon fibres (CFs) from CF-reinforced thermosetting advanced composites widely applied in high-tech fields has remained inaccessible as the harsh conditions required to recycle high-performance resin matrices unavoidably damage the structure and properties of CFs. Degradable thermosetting resins with stable covalent structures offer a potential solution to this conflict. Here we design a new synthesis scheme and prepare a recyclable CF-reinforced poly(hexahydrotriazine) resin matrix advanced composite. The multiple recycling experiments and characterization data establish that this composite demonstrates performance comparable to those of its commercial counterparts, and more importantly, it realizes multiple intact recoveries of CFs and near-total recycling of the principal raw materials through gentle depolymerization in certain dilute acid solution. To our best knowledge, this study demonstrates for the first time a feasible and environment-friendly preparation-recycle-regeneration strategy for multiple CF-recycling from CF-reinforced advanced composites.

Multiply fully recyclable carbon fibre reinforced heat-resistant covalent thermosetting advanced composites.

PubMed

Yuan, Yanchao; Sun, Yanxiao; Yan, Shijing; Zhao, Jianqing; Liu, Shumei; Zhang, Mingqiu; Zheng, Xiaoxing; Jia, Lei

2017-03-02

Nondestructive retrieval of expensive carbon fibres (CFs) from CF-reinforced thermosetting advanced composites widely applied in high-tech fields has remained inaccessible as the harsh conditions required to recycle high-performance resin matrices unavoidably damage the structure and properties of CFs. Degradable thermosetting resins with stable covalent structures offer a potential solution to this conflict. Here we design a new synthesis scheme and prepare a recyclable CF-reinforced poly(hexahydrotriazine) resin matrix advanced composite. The multiple recycling experiments and characterization data establish that this composite demonstrates performance comparable to those of its commercial counterparts, and more importantly, it realizes multiple intact recoveries of CFs and near-total recycling of the principal raw materials through gentle depolymerization in certain dilute acid solution. To our best knowledge, this study demonstrates for the first time a feasible and environment-friendly preparation-recycle-regeneration strategy for multiple CF-recycling from CF-reinforced advanced composites.

Multiply fully recyclable carbon fibre reinforced heat-resistant covalent thermosetting advanced composites

PubMed Central

Yuan, Yanchao; Sun, Yanxiao; Yan, Shijing; Zhao, Jianqing; Liu, Shumei; Zhang, Mingqiu; Zheng, Xiaoxing; Jia, Lei

2017-01-01

Nondestructive retrieval of expensive carbon fibres (CFs) from CF-reinforced thermosetting advanced composites widely applied in high-tech fields has remained inaccessible as the harsh conditions required to recycle high-performance resin matrices unavoidably damage the structure and properties of CFs. Degradable thermosetting resins with stable covalent structures offer a potential solution to this conflict. Here we design a new synthesis scheme and prepare a recyclable CF-reinforced poly(hexahydrotriazine) resin matrix advanced composite. The multiple recycling experiments and characterization data establish that this composite demonstrates performance comparable to those of its commercial counterparts, and more importantly, it realizes multiple intact recoveries of CFs and near-total recycling of the principal raw materials through gentle depolymerization in certain dilute acid solution. To our best knowledge, this study demonstrates for the first time a feasible and environment-friendly preparation-recycle-regeneration strategy for multiple CF-recycling from CF-reinforced advanced composites. PMID:28251985

Structure and characteristics of functional powder composite materials obtained by spark plasma sintering

NASA Astrophysics Data System (ADS)

Oglezneva, S. A.; Kachenyuk, M. N.; Kulmeteva, V. B.; Ogleznev, N. B.

2017-07-01

The article describes the results of spark plasma sintering of ceramic materials based on titanium carbide, titanium carbosilicide, ceramic composite materials based on zirconium oxide, strengthened by carbon nanostructures and composite materials of electrotechnical purpose based on copper with addition of carbon structures and titanium carbosilicide. The research shows that the spark plasma sintering can achieve relative density of the material up to 98%. The effect of sintering temperature on the phase composition, density and porosity of the final product has been studied. It was found that with addition of carbon nanostructures the relative density and hardness decrease, but the fracture strength of ZrO2 increases up to times 2. The relative erosion resistance of the electrodes made of composite copper-based powder materials, obtained by spark plasma sintering during electroerosion treatment of tool steel exceeds that parameter of pure copper up to times 15.

Site preferences of actinide cations in [NZP] compounds

NASA Astrophysics Data System (ADS)

Hawkins, H. T.; Spearing, D. R.; Smith, D. M.; Hampel, F. G.; Veirs, D. K.; Scheetz, B. E.

2000-07-01

Compounds adopting the sodium dizirconium tris(phosphate) (NaZr2(PO4)3) structure type belong to the [NZP] structural family of compounds. [NZP] compounds possess desirable properties that would permit their application as hosts for the actinides. These properties include compositional flexibility (i.e., three structural sites that can accommodate a variety of different cations), high thermal stability, negligible thermal expansion, and resistance to radiation damage. Experimental data indicate that [NZP] compounds resist dissolution and release of constituents over a wide range of experimental conditions. Moreover, [NZP] compounds may be synthesized by both conventional and novel methods and may be heat treated or sintered at modest temperatures (800 °C-1350 °C) in open or restricted systems.

Impact of composition and crystallization behavior of atomic layer deposited strontium titanate films on the resistive switching of Pt/STO/TiN devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aslam, N.; Rodenbücher, C.; Szot, K.

2014-08-14

The resistive switching (RS) properties of strontium titanate (Sr{sub 1+x}Ti{sub 1+y}O{sub 3+(x+2y)}, STO) based metal-oxide-metal structures prepared from industrial compatible processes have been investigated focusing on the effects of composition, microstructure, and device size. Metastable perovskite STO films were prepared on Pt-coated Si substrates utilizing plasma-assisted atomic layer deposition (ALD) from cyclopentadienyl-based metal precursors and oxygen plasma at 350 °C, and a subsequent annealing at 600 °C in nitrogen. Films of 15 nm and 12 nm thickness with three different compositions [Sr]/([Sr] + [Ti]) of 0.57 (Sr-rich STO), 0.50 (stoichiometric STO), and 0.46 (Ti-rich STO) were integrated into Pt/STO/TiN crossbar structures with sizes ranging from 100 μm{supmore » 2} to 0.01 μm{sup 2}. Nano-structural characterizations revealed a clear effect of the composition of the as-deposited STO films on their crystallization behavior and thus on the final microstructures. Local current maps obtained by local-conductivity atomic force microscopy were in good agreement with local changes of the films' microstructures. Correspondingly, also the initial leakage currents of the Pt/STO/TiN devices were affected by the STO compositions and by the films' microstructures. An electroforming process set the Pt/STO/TiN devices into the ON-state, while the forming voltage decreased with increasing initial leakage current. After a RESET process under opposite voltage has been performed, the Pt/STO/TiN devices showed a stable bipolar RS behavior with non-linear current-voltage characteristics for the high (HRS) and the low (LRS) resistance states. The obtained switching polarity and nearly area independent LRS values agree with a filamentary character of the RS behavior according to the valence change mechanism. The devices of 0.01 μm{sup 2} size with a 12 nm polycrystalline stoichiometric STO film were switched at a current compliance of 50 μA with voltages of about ±1.0 V between resistance states of about 40 kΩ (LRS) and 1 MΩ (HRS). After identification of the influences of the films' microstructures, i.e., grain boundaries and small cracks, the remaining RS properties could be ascribed to the effect of the [Sr]/([Sr] + [Ti]) composition of the ALD STO thin films.« less

Multifunctional smart composites with integrated carbon nanotube yarn and sheet

NASA Astrophysics Data System (ADS)

Chauhan, Devika; Hou, Guangfeng; Ng, Vianessa; Chaudhary, Sumeet; Paine, Michael; Moinuddin, Khwaja; Rabiee, Massoud; Cahay, Marc; Lalley, Nicholas; Shanov, Vesselin; Mast, David; Liu, Yijun; Yin, Zhangzhang; Song, Yi; Schulz, Mark

2017-04-01

Multifunctional smart composites (MSCs) are materials that combine the good electrical and thermal conductivity, high tensile and shear strength, good impact toughness, and high stiffness properties of metals; the light weight and corrosion resistance properties of composites; and the sensing or actuation properties of smart materials. The basic concept for MSCs was first conceived by Daniel Inman and others about 25 years ago. Current laminated carbon and glass fiber polymeric composite materials have high tensile strength and are light in weight, but they still lack good electrical and thermal conductivity, and they are sensitive to delamination. Carbon nanotube yarn and sheets are lightweight, electrically and thermally conductive materials that can be integrated into laminated composite materials to form MSCs. This paper describes the manufacturing of high quality carbon nanotube yarn and sheet used to form MSCs, and integrating the nanotube yarn and sheet into composites at low volume fractions. Various up and coming technical applications of MSCs are discussed including composite toughening for impact and delamination resistance; structural health monitoring; and structural power conduction. The global carbon nanotube overall market size is estimated to grow from 2 Billion in 2015 to 5 Billion by 2020 at a CAGR of 20%. Nanotube yarn and sheet products are predicted to be used in aircraft, wind machines, automobiles, electric machines, textiles, acoustic attenuators, light absorption, electrical wire, sporting equipment, tires, athletic apparel, thermoelectric devices, biomedical devices, lightweight transformers, and electromagnets. In the future, due to the high maximum current density of nanotube conductors, nanotube electromagnetic devices may also become competitive with traditional smart materials in terms of power density.

Characterization of thermal destruction behavior of hybrid composites based on polyoxymethylene, ethylene-octene copolymer impact modifier and ZnO nanofiller

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meri, Remo Merijs; Zicans, Janis; Abele, Agnese

Hybrid polymer nanocomposites, composed of polyoxymethylene (POM), ethylene octene copolymer (EOC) and plasma synthesized tetrapod shaped zinc oxide (ZnO), were prepared by using melt compounding. The content of EOC in the POM based composites was varied between 10 and 50 mass %, while the content of ZnO was constant (2 mass %). Thermal behaviour of POM based systems was studied by using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The influence of the elastomer content and/or ZnO addition on the thermal stability of POM based systems was evaluated. The influence of the α-octene content in the elastomer on themore » thermal decomposition behaviour of POM and its nanocomposites with ZnO was also evaluated. Results of thermogravimetric analysis showed that, by rising either the elastomer or ZnO content, thermal stability of the investigated POM composites was increased. The modifying effect of EOC17 in respect of thermal resistance was somewhat larger than that of EOC38 because of the smaller amount of tertiary carbon atoms in the macromolecular structure of the former elastomer. Improved thermal resistance of ZnO containing POM based composites was because of impermeable structure the inorganic nanofiller allowing decrease gas exchange rate and facilitating non-combustible gases, such as CO{sub 2}, stay in the zone of burning. Addition of ZnO have a potential to influence structure of the polymer blend matrix itself by improving its barrier characteristics.« less

Toughened uni-piece, fibrous, reinforced, oxidization-resistant composite

NASA Technical Reports Server (NTRS)

Stewart, David A. (Inventor); Leiser, Daniel B. (Inventor)

2008-01-01

A composite thermal protection structure, for applications such as atmospheric re-entry vehicles, that can withstand temperatures as high as 3600.degree F. The structure includes an exposed surface cap having a specially formulated coating, an insulator base adjacent to the cap with another specially formulated coating, and one or more pins that extend from the cap through the insulator base to tie the cap and base together, through ceramic bonding and mechanical attachment. The cap and insulator base have corresponding depressions and projections that mate and allow for differences in thermal expansion of the cap and base.

TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

NASA Astrophysics Data System (ADS)

Ghalamboran, Milad; Saedi, Yasin

2016-03-01

The fabrication method and characterization results of a TiO2-TiO2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO2 crystallites embedded in a matrix of nanometric TiO2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant.

Comparison of Failure Process of Bended Beams Reinforced with Steel Bars and GFRP Bars

NASA Astrophysics Data System (ADS)

Kaszyńska, Maria; Błyszko, Jarosław; Olczyk, Norbert

2017-10-01

The Fibre Reinforced Polymer (FRP) composite rebar has been used in civil engineering structures for several years. It has many characteristics, which not only are equal to those of steel rebar, but significantly surpass them. The composite rebar has high corrosion resistance, electromagnetic neutrality and has much higher tensile strength than steel. Also, because of its low weight and easy processing composite rebar is convenient for shipment and use. Development of architectural concrete technology in past years opens new, interesting perspectives for use of composite rebar. However, implementation of those concretes in structures is often burdened with many issues, especially concerning faulty performance. One of it is rebar’s corrosion, visible on the surface of the element as rusty stains. Even if the structure was properly developed meeting all the requirements for texture, porosity or colour uniformity, and rusty stains can completely destroy the final decorative effect of concrete’s surface. Despite many advantages, the use of composite rebar in reinforced structures creates significant number of new “behaviours” in its different working stages. Structures reinforced with the steel rebar will behave differently than the ones with composite FRP rebar under continuous load, in case of a fire, exposed to aggressive environment or at breaking point. In the latter, significant role plays its linear-elastic behaviour in the whole tensile range till rupture. This means that the FPR rebar does not exhibit plastic deformation and reaches its bearing capacity suddenly without any visible signs. This should be considered during designing stage and included as an additional reduction coefficient. The article presents result of research and analysis of destructive tests performed on concrete beams reinforced with traditional steel rebar and composite rebar made of glass fibre and braided with basaltic (GFRP). Four single-span simply supported beams under static load were tested. Both types of beams were designed to have the same bearing capacity. Beams reinforced with GFRP rebar exhibited much bigger cracking than traditionally reinforced bars. The width of cracks appearing in beams reinforced with GFRP bars was equal or greater than limit values (0.4 mm) even though the ratio of moment of resistance and cracking moment was greater than 3. The composite rebar exhibits many significant advantages over steel rebar, but its rather low Young’s modulus comparing to steel causes exceeded deflection and cracking of bended concrete elements.

Preparation and tribological behaviors of poly (ether ether ketone) nanocomposite films containing graphene oxide nanosheets

NASA Astrophysics Data System (ADS)

Song, Hao-Jie; Li, Na; Yang, Jin; Min, Chun-Ying; Zhang, Zhao-zhu

2013-02-01

The composite films of poly (ether ether ketone) (PEEK) filled with different proportions of graphene oxide (GO) nanosheets were prepared by the cast method. The tribological behaviors of the composite films under boundary lubrication (water and liquid paraffin oil lubrication) were investigated and compared with that under dry sliding on an UMT-2 friction and wear machine, by running a steel sphere against the composite films. The results were as follows: GO nanosheets as the filler greatly improve the wear resistance of PEEK under boundary lubrication, though the composites show a different dependence of wear resistance on the filler content. Scanning electron microscopy and optical microscopy performed to analyze the wear scar surfaces after friction confirmed that the outstanding lubrication performance of GO could be attributed to their small size and extremely thin laminated structure, which allow the GO to easily enter the contact area, thereby preventing the rough surfaces from coming into direct contact.

Ultra High Temperature Ceramics' Processing Routes and Microstructures Compared

NASA Technical Reports Server (NTRS)

Gusman, Michael; Stackpoole, Mairead; Johnson, Sylvia; Gasch, Matt; Lau, Kai-Hung; Sanjurjo, Angel

2009-01-01

Ultra High Temperature Ceramics (UHTCs), such as HfB2 and ZrB2 composites containing SiC, are known to have good thermal shock resistance and high thermal conductivity at elevated temperatures. These UHTCs have been proposed for a number of structural applications in hypersonic vehicles, nozzles, and sharp leading edges. NASA Ames is working on controlling UHTC properties (especially, mechanical properties, thermal conductivity, and oxidation resistance) through processing, composition, and microstructure. In addition to using traditional methods of combining additives to boride powders, we are preparing UHTCs using coat ing powders to produce both borides and additives. These coatings and additions to the powders are used to manipulate and control grain-boundary composition and second- and third-phase variations within the UHTCs. Controlling the composition of high temperature oxidation by-products is also an important consideration. The powders are consolidated by hot-pressing or field-assisted sintering (FAS). Comparisons of microstructures and hardness data will be presented.

Cycle oxidation behavior and anti-oxidation mechanism of hot-dipped aluminum coating on TiBw/Ti6Al4V composites with network microstructure.

PubMed

Li, X T; Huang, L J; Wei, S L; An, Q; Cui, X P; Geng, L

2018-04-10

Controlled and compacted TiAl 3 coating was successfully fabricated on the network structured TiBw/Ti6Al4V composites by hot-dipping aluminum and subsequent interdiffusion treatment. The network structure of the composites was inherited to the TiAl 3 coating, which effectively reduces the thermal stress and avoids the cracks appeared in the coating. Moreover, TiB reinforcements could pin the TiAl 3 coating which can effectively improve the bonding strength between the coating and composite substrate. The cycle oxidation behavior of the network structured coating on 873 K, 973 K and 1073 K for 100 h were investigated. The results showed the coating can remarkably improve the high temperature oxidation resistance of the TiBw/Ti6Al4V composites. The network structure was also inherited to the Al 2 O 3 oxide scale, which effectively decreases the tendency of cracking even spalling about the oxide scale. Certainly, no crack was observed in the coating after long-term oxidation due to the division effect of network structured coating and pinning effect of TiB reinforcements. Interfacial reaction between the coating and the composite substrate occurred and a bilayer structure of TiAl/TiAl 2 formed next to the substrate after oxidation at 973 K and 1073 K. The anti-oxidation mechanism of the network structured coating was also discussed.

Titanium/beryllium laminates: Fabrication, mechanical properties, and potential aerospace applications

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Lark, R. F.

1978-01-01

The investigation indicated that structural laminates can be made which have: a modulus of elasticity comparable to steel, fracture strength of comparable to the yield strength of titanium, density comparable to aluminum, impact resistance comparable to titanium, and little or no notch sensitivity. These laminates can have stiffness and weight advantages over other materials including advanced fiber composites, in some aerospace applications where buckling resistance, vibration frequencies, and weight considerations control the design.

Bioactive Ca-P coating with self-sealing structure on pure magnesium.

PubMed

Gan, Junjie; Tan, Lili; Yang, Ke; Hu, Zhuangqi; Zhang, Qiang; Fan, Xinmin; Li, Yangde; Li, Weirong

2013-04-01

Bioactive coatings containing Ca and P with self-sealing structures were fabricated on the surface of pure magnesium using micro-arc oxidation technique (MAO) in a specific calcium hydroxide based electrolyte system. Coatings were prepared at three applied voltages, i.e. 360, 410 and 450 V, and the morphology, chemical composition, corrosion resistance and the degradation properties in Hank's solution of the MAO-coated samples with three different applied voltages were investigated. It was found that all the three coatings showed similar surface morphologies that the majority of micro-pores were filled with compound particles. Both the porous structures and the compound particles were found to contain consistent chemical compositions which were mainly composed of O, Mg, F, Ca and P. Electrochemical tests showed a significant increase in corrosion resistance for the three coatings, meanwhile the coating obtained at 450 V exhibited the superior corrosion resistance owing to the largest coating thickness. The long term immersion tests in Hank's solution also revealed an effective reduction in corrosion rate for the MAO coated samples, and the pH values of the coated samples always maintained a lower level. Besides, all the three coatings were subjected to a mild and uniform degradation, while the coating obtained at 360 V showed a relatively obvious degradation characteristic and appreciable Ca and P contents on the surfaces of the three coatings were observed after immersion in Hank's solution. The results of the present study confirmed that the MAO coatings containing bioactive Ca and P elements with self-sealing structures could significantly enhance the corrosion resistance of magnesium substrate in Hanks' solution with great potential for medical application.

Lead-Free KNbO3:xZnO Composite Ceramics.

PubMed

Lv, Xiang; Li, Zhuoyun; Wu, Jiagang; Xiao, Dingquan; Zhu, Jianguo

2016-11-09

It is a tough issue to develop dense and water resistant KNbO 3 ceramics due to high evaporation and hygroscopicity of K 2 O. Here, KNbO 3 :xZnO composite ceramics were used to successfully solve this problem, where ZnO particles were randomly distributed into a KNbO 3 matrix. The addition of ZnO hardly affects the phase structure of KNbO 3 , and moreover, the enhancement of electrical properties, thermal stability, and aging characteristics was observed in KNbO 3 :xZnO composite ceramics. The composites possessed the maximum d 33 of 120 ± 5 pC/N, which is superior to that of pure KNbO 3 (d 33 = 80 pC/N). More importantly, a strong water resistance and an aging-free characteristic were observed in KNbO 3 :0.4ZnO. This is the first time for KNbO 3 ceramics to simultaneously improve electrical properties and resolve the water-absorbing properties. We believe that these composite ceramics are promising for practical applications.

Heavy ion irradiation effects of brannerite-type ceramics

NASA Astrophysics Data System (ADS)

Lian, J.; Wang, L. M.; Lumpkin, G. R.; Ewing, R. C.

2002-05-01

Brannerite, UTi 2O 6, occurs in polyphase Ti-based, crystalline ceramics that are under development for plutonium immobilization. In order to investigate radiation effects caused by α-decay events of Pu, a 1 MeV Kr + irradiation on UTi 2O 6, ThTi 2O 6, CeTi 2O 6 and a more complex material, composed of Ca-containing brannerite and pyrochlore, was performed over a temperature range of 25-1020 K. The ion irradiation-induced crystalline-to-amorphous transformation was observed in all brannerite samples. The critical amorphization temperatures of the different brannerite compositions are: 970 K, UTi 2O 6; 990 K, ThTi 2O 6; 1020 K, CeTi 2O 6. The systematic increase in radiation resistance from Ce-, Th- to U-brannerite is related to the difference of mean atomic mass of A-site cation in the structure. As compared with the pyrochlore structure-type, brannerite phases are more susceptible to ion irradiation-induced amorphization. The effects of structure and chemical compositions on radiation resistance of brannerite-type and pyrochlore-type ceramics are discussed.

Protective coatings for composite tubes in space applications

NASA Technical Reports Server (NTRS)

Dursch, Harry W.; Hendricks, Carl L.

1987-01-01

Protective coatings for graphite/epoxy (Gr/Ep) tubular structures for a manned Space Station truss structure were evaluated. The success of the composite tube truss structure depends on its stability to long-term exposure to the low earth orbit (LEO) environment, with particular emphasis placed on atomic oxygen. Concepts for protectively coating Gr/Ep tubes include use of inorganic coated metal foils and electroplating. These coatings were applied to Gr/Ep tubes and then subjected to simulated LEO environment to evaluate survivability of coatings and coated tubes. Evaluation included: atomic oxygen resistance, changes in optical properties and adhesion, abrasion resistance, surface preparation required, coating uniformity, and formation of microcracks in the Gr/Ep tubes caused by thermal cycling. Program results demonstrated that both phosphoric and chromic acid anodized Al foil provided excellent adhesion to Gr/Ep tubes and exhibited stable optical properties when subjected to simulated LEO environment. The SiO2/Al coatings sputtered onto Al foils also resulted in an excellent protective coating. Electroplated Ni exhibited unacceptable adhesion loss to Gr/Ep tubes during atomic oxygen exposure.

Influence of substrate bias voltage on structure and properties of the CrAlN films deposited by unbalanced magnetron sputtering

NASA Astrophysics Data System (ADS)

Lv, Yanhong; Ji, Li; Liu, Xiaohong; Li, Hongxuan; Zhou, Huidi; Chen, Jianmin

2012-02-01

The CrAlN films were deposited on silicon and stainless steel substrates by unbalanced magnetron sputtering system. The influence of substrate bias on deposition rate, composition, structure, morphology and properties of the CrAlN films was investigated. The results showed that, with the increase of the substrate bias voltage, the deposition rate decreased accompanied by a change of the preferred orientation of the CrAlN film from (2 2 0) to (2 0 0). The grain size and the average surface roughness of the CrAlN films declined as the bias voltage increases above -100 V. The morphology of the films changed from obviously columnar to dense glass-like structure with the increase of the bias voltage from -50 to -250 V. Meanwhile, the films deposited at moderate bias voltage had better mechanical and tribological properties, while the films deposited at higher bias voltage showed better corrosion resistance. It was found that the corrosion resistance improvement was not only attributed to the low pinhole density of the film, but also to chemical composition of films.

PLUTONIUM-ZIRCONIUM ALLOYS

DOEpatents

Schonfeld, F.W.; Waber, J.T.

1960-08-30

A series of nuclear reactor fuel alloys consisting of from about 5 to about 50 at.% zirconium (or higher zirconium alloys such as Zircaloy), balance plutonium, and having the structural composition of a plutonium are described. Zirconium is a satisfactory diluent because it alloys readily with plutonium and has desirable nuclear properties. Additional advantages are corrosion resistance, excellent fabrication propenties, an isotropie structure, and initial softness.

Sintering Process and Mechanical Property of MWCNTs/HDPE Bulk Composite.

PubMed

Ming-Wen, Wang; Tze-Chi, Hsu; Jie-Ren, Zheng

2009-08-01

Studies have proved that increasing polymer matrices by carbon nanotubes to form structural reinforcement and electrical conductivity have significantly improved mechanical and electrical properties at very low carbon nanotubes loading. In other words, increasing polymer matrices by carbon nanotubes to form structural reinforcement can reduce friction coefficient and enhance anti-wear property. However, producing traditional MWCNTs in polymeric materix is an extremely complicated process. Using melt-mixing process or in situ polymerization leads to better dispersion effect on composite materials. In this study, therefore, to simplify MWCNTs /HDPE composite process and increase dispersion, powder was used directly to replace pellet to mix and sinter with MWCNTs. The composite bulks with 0, 0.5, 1, 2 and 4% nanotube content by weight was analyzed under SEM to observe nanotubes dispersion. At this rate, a MWCNTs/HDPE composite bulk with uniformly dispersed MWCNTs was achieved, and through the wear bench (Pin-on-Disk), the wear experiment has accomplished. Accordingly, the result suggests the sintered MWCNTs/HDPE composites amplify the hardness and wear-resist property.

Structure, mechanical and magnetic properties of Al4C3 reinforced nickel matrix nanocomposites

NASA Astrophysics Data System (ADS)

Chaudhari, Alok Kumar; Singh, Dhananjay Kumar; Singh, V. B.

2018-05-01

A new type of nanocomposite, Ni-Al4C3 was prepared using Al4C3 as reinforcement by cathodic co-deposition at different current densities (1.0 to 5.0 A dm‑2) from a nickel acetate-N-methyl formamide (non-aqueous) bath. Influence of current density and incorporation of Al4C3 particles in nickel matrix on the structure and properties of the composite coatings was investigated. Surface morphology and composition of the deposits were determined by SEM and EDAX. Crystallographic structure and orientation of the electrodeposited Ni-Al4C3 composite were studied by x-ray diffraction. Compared to nickel metal, these nanocomposites exhibited finer grains, higher microhardness, improved corrosion resistance and enhanced soft magnetic properties. Composite deposited at higher current densities (>2 A dm‑2) shows mild texturing along (200) plane. The effect of heat treatment on the microstructure, texture and microhardness of the nanocomposites was also investigated.

Preparation and Exceptional Mechanical Properties of Bone-Mimicking Size-Tuned Graphene Oxide@Carbon Nanotube Hybrid Paper.

PubMed

Oh, Jun Young; Kim, Yern Seung; Jung, Yeonsu; Yang, Seung Jae; Park, Chong Rae

2016-02-23

The self-assembled nanostructures of carbon nanomaterials possess a damage-tolerable architecture crucial for the inherent mechanical properties at both micro- and macroscopic levels. Bone, or "natural composite," has been known to have superior energy dissipation and fracture resistance abilities due to its unique load-bearing hybrid structure. However, few approaches have emulated the desirable structure using carbon nanomaterials. In this paper, we present an approach in fabricating a hybrid composite paper based on graphene oxide (GO) and carbon nanotube (CNT) that mimicks the natural bone structure. The size-tuning strategy enables smaller GO sheets to have more cross-linking reactions with CNTs and be homogeneously incorporated into CNT-assembled paper, which is advantageous for effective stress transfer. The resultant hybrid composite film has enhanced mechanical strength, modulus, toughness, and even electrical conductivity compared to previously reported CNT-GO based composites. We further demonstrate the usefulness of the size-tuned GOs as the "stress transfer medium" by performing in situ Raman spectroscopy during the tensile test.

Methods for Producing High-Performance Silicon Carbide Fibers, Architectural Preforms, and High-Temperature Composite Structures

NASA Technical Reports Server (NTRS)

Yun, Hee-Mann (Inventor); DiCarlo, James A. (Inventor)

2014-01-01

Methods are disclosed for producing architectural preforms and high-temperature composite structures containing high-strength ceramic fibers with reduced preforming stresses within each fiber, with an in-situ grown coating on each fiber surface, with reduced boron within the bulk of each fiber, and with improved tensile creep and rupture resistance properties tier each fiber. The methods include the steps of preparing an original sample of a preform formed from a pre-selected high-strength silicon carbide ceramic fiber type, placing the original sample in a processing furnace under a pre-selected preforming stress state and thermally treating the sample in the processing furnace at a pre-selected processing temperature and hold time in a processing gas having a pre-selected composition, pressure, and flow rate. For the high-temperature composite structures, the method includes additional steps of depositing a thin interphase coating on the surface of each fiber and forming a ceramic or carbon-based matrix within the sample.

Boron modified molybdenum silicide and products

DOEpatents

Meyer, M.K.; Akinc, M.

1999-02-02

A boron-modified molybdenum silicide material is disclosed having the composition comprising about 80 to about 90 weight % Mo, about 10 to about 20 weight % Si, and about 0.1 to about 2 weight % B and a multiphase microstructure including Mo{sub 5}Si{sub 3} phase as at least one microstructural component effective to impart good high temperature creep resistance. The boron-modified molybdenum silicide material is fabricated into such products as electrical components, such as resistors and interconnects, that exhibit oxidation resistance to withstand high temperatures in service in air as a result of electrical power dissipation, electrical resistance heating elements that can withstand high temperatures in service in air and other oxygen-bearing atmospheres and can span greater distances than MoSi{sub 2} heating elements due to improved creep resistance, and high temperature structural members and other fabricated components that can withstand high temperatures in service in air or other oxygen-bearing atmospheres while retaining creep resistance associated with Mo{sub 5}Si{sub 3} for structural integrity. 7 figs.

Boron modified molybdenum silicide and products

DOEpatents

Meyer, Mitchell K.; Akinc, Mufit

1999-02-02

A boron-modified molybdenum silicide material having the composition comprising about 80 to about 90 weight % Mo, about 10 to about 20 weight % Si, and about 0.1 to about 2 weight % B and a multiphase microstructure including Mo.sub.5 Si.sub.3 phase as at least one microstructural component effective to impart good high temperature creep resistance. The boron-modified molybdenum silicide material is fabricated into such products as electrical components, such as resistors and interconnects, that exhibit oxidation resistance to withstand high temperatures in service in air as a result of electrical power dissipation, electrical resistance heating elements that can withstand high temperatures in service in air and other oxygen-bearing atmospheres and can span greater distances than MoSi.sub.2 heating elements due to improved creep resistance, and high temperature structural members and other fabricated components that can withstand high temperatures in service in air or other oxygen-bearing atmospheres while retaining creep resistance associated with Mo.sub.5 Si.sub.3 for structural integrity.

Inorganic-organic nanocomposites formed using porous ceramic particles

NASA Astrophysics Data System (ADS)

Luo, Jiazhong

Inorganic-organic nanocomposites are expected to be of great significance in new material technologies impacting many different fields. We develop new nanomaterials of this type that have an interpenetrating network structure via in-situ polymerization of monomer within the nanopores of inorganic gel particles (porosity 20-80 vol.%). Due to strong nanomechanical bonding, these thermosetting polymer composites are expected to exhibit improved mechanical performance. Particle porosity is a primary factor. In contrast to HCl-catalyzed gels, more porous HF-catalyzed gels (porosity 62 vol.%) produced higher composite wear-resistance. At the same loading, the wear rates decrease linearly with increasing filler porosity. Better wear resistance is associated with fine-scale plastic deformation as opposed to brittle fracture and particle pull-out. For the coupling of HF-catalyzed particles with gamma-methacryloxypropyl trimethoxysilane, FTIR and solid-state sp{13}C/sp{29}Si NMR show that the use of a catalyst (n-propylamine) and a nonpolar solvent (cyclohexane), causes the degree of coupling and self-condensation to increase. Ethanol competes with the silane for the surface and results in less silane self-condensation. Surprisingly, the silane diminishes the composite wear resistance due to its pore-filling effect and the subsequent decrease in polymer interpenetration. A transition from plastic deformation to brittle fracture is involved. A new sol-gel technique was found to prepare porous (up to 76.54 vol.%) silica nanoparticles from solution via sodium fluoride (NaF) salt catalysis. Full interpenetration is achieved without the use of silane coupling agents. The resulting composites displayed improved wear resistance, toughness, modulus, hardness and high compressive strength. Toughening and reinforcement can be explained by pore confinement. DMA and DEA were combined with TEM to investigate related structure and property issues. The filler matrix effect on composite wear was evaluated utilizing the phase transformation of porous alumina gels from the stable monohydrate to the gamma-alumina form between 300 and 400sp°C; conveniently the total amount of porosity remains the same. gamma-alumina is more efficient than the monohydrate in improving wear resistance. The susceptibility of the monohydrate to 'transgranular' deformation and the crack-deflection of gamma-alumina in an 'intergranular' mode are responsible for the similar toughening effect of these two reinforcements.

Characterization of a highly hop-resistant Lactobacillus brevis strain lacking hop transport.

PubMed

Behr, Jürgen; Gänzle, Michael G; Vogel, Rudi F

2006-10-01

Resistance to hops is a prerequisite for lactic acid bacteria to spoil beer. In this study we analyzed mechanisms of hop resistance of Lactobacillus brevis at the metabolism, membrane physiology, and cell wall composition levels. The beer-spoiling organism L. brevis TMW 1.465 was adapted to high concentrations of hop compounds and compared to a nonadapted strain. Upon adaptation to hops the metabolism changed to minimize ethanol stress. Fructose was used predominantly as a carbon source by the nonadapted strain but served as an electron acceptor upon adaptation to hops, with concomitant formation of acetate instead of ethanol. Furthermore, hop adaptation resulted in higher levels of lipoteichoic acids (LTA) incorporated into the cell wall and altered composition and fluidity of the cytoplasmic membrane. The putative transport protein HitA and enzymes of the arginine deiminase pathway were overexpressed upon hop adaptation. HorA was not expressed, and the transport of hop compounds from the membrane to the extracellular space did not account for increased resistance to hops upon adaptation. Accordingly, hop resistance is a multifactorial dynamic property, which can develop during adaptation. During hop adaptation, arginine catabolism contributes to energy and generation of the proton motive force until a small fraction of the population has established structural improvements. This acquired hop resistance is energy independent and involves an altered cell wall composition. LTA shields the organism from accompanying stresses and provides a reservoir of divalent cations, which are otherwise scarce as a result of their complexation by hop acids. Some of the mechanisms involved in hop resistance overlap with mechanisms of pH resistance and ethanol tolerance and as a result enable beer spoilage by L. brevis.

The effect of temperature and moisture on electrical resistance, strain sensitivity and crack sensitivity of steel fiber reinforced smart cement composite

NASA Astrophysics Data System (ADS)

Teomete, Egemen

2016-07-01

Earthquakes, material degradations and other environmental factors necessitate structural health monitoring (SHM). Metal foil strain gages used for SHM have low durability and low sensitivity. These factors motivated researchers to work on cement based strain sensors. In this study, the effects of temperature and moisture on electrical resistance, compressive and tensile strain gage factors (strain sensitivity) and crack sensitivity were determined for steel fiber reinforced cement based composite. A rapid increase of electrical resistance at 200 °C was observed due to damage occurring between cement paste, aggregates and steel fibers. The moisture—electrical resistance relationship was investigated. The specimens taken out of the cure were saturated with water and had a moisture content of 9.49%. The minimum electrical resistance was obtained at 9% moisture at which fiber-fiber and fiber-matrix contact was maximum and the water in micro voids was acting as an electrolyte, conducting electrons. The variation of compressive and tensile strain gage factors (strain sensitivities) and crack sensitivity were investigated by conducting compression, split tensile and notched bending tests with different moisture contents. The highest gage factor for the compression test was obtained at optimal moisture content, at which electrical resistance was minimum. The tensile strain gage factor for split tensile test and crack sensitivity increased by decreasing moisture content. The mechanisms between moisture content, electrical resistance, gage factors and crack sensitivity were elucidated. The relations of moisture content with electrical resistance, gage factors and crack sensitivities have been presented for the first time in this study for steel fiber reinforced cement based composites. The results are important for the development of self sensing cement based smart materials.

Composite structural armor for combat vehicle applications

NASA Technical Reports Server (NTRS)

Haskell, William E., III; Alesi, A. L.; Parsons, G. R.

1990-01-01

Several projects that have demonstrated the advantages of using thick composite armor technology for structural applications in armored combat vehicles are discussed. The first involved composite cargo doors for the Marine Corps LVTP-7 amphibious landing vehicle. Another was a demonstration composite turret that offered a weight reduction of 15.5 percent. The advantages of this composite armor compared to metallic armors used for combat vehicle hull and turret applications are reduced weight at equal ballistic protection; reduced back armor spall; excellent corrosion resistance; reduced production costs by parts consolidation; and inherent thermal and acoustic insulative properties. Based on the encouraging results of these past programs, the Demonstration Composite Hull Program was started in September 1986. To demonstrate this composite armor technology, the Army's newest infantry fighting vehicle, the Bradley Fighting Vehicle (BFV), was selected as a model. A composite infantry fighting vehicle, designated the CIFV for this program, has been designed and fabricated and is currently undergoing a 6000 mile field endurance test. The CIFV demonstration vehicle uses the BFV engine, transmission, suspension, track and other equipment.

Fabrication and characterization of a biodegradable Mg-2Zn-0.5Ca/1β-TCP composite.

PubMed

Huang, Yan; Liu, Debao; Anguilano, Lorna; You, Chen; Chen, Minfang

2015-09-01

A biodegradable magnesium matrix and beta-tricalcium phosphate (β-TCP) particles reinforced composite Mg-2Zn-0.5Ca/1beta-TCP (wt.%) was fabricated for biomedical applications by the novel route of combined high shear solidification (HSS) and equal channel angular extrusion (ECAE). The as-cast composite obtained by HSS showed a fine and equiaxed grain structure with globally uniformly distributed β-TCP particles in aggregates of 2-25 μm in size. The ECAE processing at 300 °C resulted in further microstructural refinement and the improvement of β-TCP particle distribution. During ECAE, the β-TCP aggregates were broken into smaller ones or individual particles, forming a dispersion in the matrix. Such fabricated composite exhibited enhanced hardness and in vitro corrosion resistance. The enhanced hardness was attributed to both the addition of β-TCP particles and grain refinement while the development of a Ca-P rich surface layer from β-TCP during corrosion was responsible for the improvement in corrosion resistance. The composite was characterized in terms of microstructural evolution during fabrication, mechanical properties and electrochemical performance during polarization and immersion tests in a simulated body fluid. Discussions are made on the benefits of both HSS and ECAE and the mechanisms responsible for the enhanced corrosion resistance. Copyright © 2015 Elsevier B.V. All rights reserved.

Chrome-free Samarium-based Protective Coatings for Magnesium Alloys

NASA Astrophysics Data System (ADS)

Hou, Legan; Cui, Xiufang; Yang, Yuyun; Lin, Lili; Xiao, Qiang; Jin, Guo

The microstructure of chrome-free samarium-based conversion coating on magnesium alloy was investigated and the corrosion resistance was evaluated as well. The micro-morphology, transverse section, crystal structure and composition of the coating were observed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and X- ray photoelectron spectroscopy (XPS), respectively. The corrosion resistance was evaluated by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS). The results reveal that the morphology of samarium conversion coating is of crack-mud structure. Tiny cracks distribute in the compact coating deposited by samarium oxides. XRD, EDS and XPS results characterize that the coating is made of amorphous and trivalent-samarium oxides. The potentiodynamic polarization curve, EIS and OCP indicate that the samarium conversion coating can improve the corrosion resistance of magnesium alloys.

Equations to assess the impact resistance of fiber composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Hanson, M. P.; Serafini, T. T.

1972-01-01

Numerical analysis of impact resistance of composite materials containing fibers is discussed. Mathematical model of longitudinal impact resistance is presented. Potential impact resistance of various fiber composites as obtained by numerical analysis is presented as plotted curve.

A Numerical Analysis of the Resistance and Stiffness of the Timber and Concrete Composite Beam

NASA Astrophysics Data System (ADS)

Szumigała, Ewa; Szumigała, Maciej; Polus, Łukasz

2015-03-01

The article presents the results of a numerical analysis of the load capacity and stiffness of the composite timber and concrete beam. Timber and concrete structures are relatively new, they have not been thoroughly tested and they are rarely used because of technological constraints. One of the obstacles to using them is difficulty with finding a method which would allow successful cooperation between concrete and timber, which has been proposed by the authors of the present article. The modern idea of sustainable construction design requires the use of new more environmentally-friendly solutions. Wood as an ecological material is easily accessible, less energy-consuming, and under certain conditions more corrosion-resistant than steel. The analysis presented in the article showed that cooperation between a wooden beam and a concrete slab on profiled steel sheeting is possible. The analysed composite beam has a greater load capacity and stiffness than the wooden beam.

Outside-the-(Cavity-prep)-Box Thinking

PubMed Central

Thompson, V.P.; Watson, T.F.; Marshall, G.W.; Blackman, B.R.K.; Stansbury, J.W.; Schadler, L.S.; Pearson, R.A.; Libanori, R.

2013-01-01

Direct placement restorative materials must interface with tooth structures that are often compromised by caries or trauma. The material must seal the interface while providing sufficient strength and wear resistance to assure function of the tooth for, ideally, the lifetime of the patient. Needed are direct restorative materials that are less technique-sensitive than current resin-based composite systems while having improved properties. The ideal material could be successfully used in areas of the world with limited infrastructure. Advances in our understanding of the interface between the restoration adhesive system and the stages of carious dentin can be used to promote remineralization. Application of fracture mechanics to adhesion at the tooth-restoration interface can provide insights for improvement. Research in polymer systems suggests alternatives to current composite resin matrix systems to overcome technique sensitivity, while advances in nano- and mesoparticle reinforcement and alignment in composite systems can increase material strength, toughness, and wear resistance, foreshadowing dental application. PMID:24129814

Research on the Influence of Size Effect for the mechanical Performance of GFRP tube concrete steel tube composite column under axial compression

NASA Astrophysics Data System (ADS)

Li, Wen; Wang, Tong; Na, Yu

2017-08-01

FRP tube-concrete-steel tube composite column (DSTC) was a new type of composite structures. The column consists of FRP outer tube and steel tube and concrete. Concrete was filled between FRP outer tube and steel tube. This column has the character of light and high strength and corrosion resistance. In this paper, properties of DSTC axial compression were studied in depth. The properties were studied by two groups DSTC short columns under axial compression performance experiment. The different size of DSTC short columns was importantly considered. According to results of the experiment, we can conclude that with the size of the column increases the ability of it to resist deformation drops. On the other hand, the size effect influences on properties of different concrete strength DSTC was different. The influence of size effect on high concrete strength was less than that of low concrete.

Lessons learned for composite structures

NASA Technical Reports Server (NTRS)

Whitehead, R. S.

1991-01-01

Lessons learned for composite structures are presented in three technology areas: materials, manufacturing, and design. In addition, future challenges for composite structures are presented. Composite materials have long gestation periods from the developmental stage to fully matured production status. Many examples exist of unsuccessful attempts to accelerate this gestation period. Experience has shown that technology transition of a new material system to fully matured production status is time consuming, involves risk, is expensive and should not be undertaken lightly. The future challenges for composite materials require an intensification of the science based approach to material development, extension of the vendor/customer interaction process to include all engineering disciplines of the end user, reduced material costs because they are a significant factor in overall part cost, and improved batch-to-batch pre-preg physical property control. Historical manufacturing lessons learned are presented using current in-service production structure as examples. Most producibility problems for these structures can be traced to their sequential engineering design. This caused an excessive emphasis on design-to-weight and schedule at the expense of design-to-cost. This resulted in expensive performance originated designs, which required costly tooling and led to non-producible parts. Historically these problems have been allowed to persist throughout the production run. The current/future approach for the production of affordable composite structures mandates concurrent engineering design where equal emphasis is placed on product and process design. Design for simplified assembly is also emphasized, since assembly costs account for a major portion of total airframe costs. The future challenge for composite manufacturing is, therefore, to utilize concurrent engineering in conjunction with automated manufacturing techniques to build affordable composite structures. Composite design experience has shown that significant weight savings have been achieved, outstanding fatigue and corrosion resistance have been demonstrated, and in-service performance has been very successful. Currently no structural design show stoppers exist for composite structures. A major lesson learned is that the full scale static test is the key test for composites, since it is the primary structural 'hot spot' indicator. The major durability issue is supportability of thin skinned structure. Impact damage has been identified as the most significant issue for the damage tolerance control of composite structures. However, delaminations induced during assembly operations have demonstrated a significant nuisance value. The future challenges for composite structures are threefold. Firstly, composite airframe weight fraction should increase to 60 percent. At the same time, the cost of composite structures must be reduced by 50 percent to attain the goal of affordability. To support these challenges it is essential to develop lower cost materials and processes.

Fabrication of large area woodpile structure in polymer

NASA Astrophysics Data System (ADS)

Gupta, Jaya Prakash; Dutta, Neilanjan; Yao, Peng; Sharkawy, Ahmed S.; Prather, Dennis W.

2009-02-01

A fabrication process of three-dimensional Woodpile photonic crystals based on multilayer photolithography from commercially available photo resist SU8 have been demonstrated. A 6-layer, 2 mm × 2mm woodpile has been fabricated. Different factors that influence the spin thickness on multiple resist application have been studied. The fabrication method used removes, the problem of intermixing, and is more repeatable and robust than the multilayer fabrication techniques for three dimensional photonic crystal structures that have been previously reported. Each layer is developed before next layer photo resist spin, instead of developing the whole structure in the final step as used in multilayer process. The desired thickness for each layer is achieved by the calibration of spin speed and use of different photo resist compositions. Deep UV exposure confinement has been the defining parameter in this process. Layer uniformity for every layer is independent of the previous developed layers and depends on the photo resist planarizing capability, spin parameters and baking conditions. The intermixing problem, which results from the previous layers left uncrossed linked photo resist, is completely removed in this process as the previous layers are fully developed, avoiding any intermixing between the newly spun and previous layers. Also this process gives the freedom to redo every spin any number of times without affecting the previously made structure, which is not possible in other multilayer process where intermediate developing is not performed.

Structural and functional polymer-matrix composites for electromagnetic applications

NASA Astrophysics Data System (ADS)

Wu, Junhua

This dissertation addresses the science and technology of functional and structural polymer-matrix composite materials for electromagnetic applications, which include electromagnetic interference (EMI) shielding and low observability (Stealth). The structural composites are continuous carbon fiber epoxy-matrix composites, which are widely used for airframes. The functional composites are composites with discontinuous fillers and in both bulk and coating forms. Through composite structure variation, attractive electromagnetic properties have been achieved. With no degradation of the tensile strength or modulus, the shielding effectiveness of the structural composites has been improved by enhancing multiple reflections through light activation of the carbon fiber. The multiple reflections loss of the electromagnetic wave increases from 1.1 to 10.2 dB at 1.0 GHz due to the activation. Such a large effect of multiple reflections has not been previously reported in any material. The observability of these composites has been lowered by decreasing the electrical conductivity (and hence decreasing the reflection loss) through carbon fiber coating. The incorporation of mumetal, a magnetic alloy particulate filler (28-40 mum size), in a latex paint has been found to be effective for enhancing the shielding only if the electrical resistivity of the resulting composite coating is below 10 O.cm, as rendered by a conductive particulate filler, such as nickel flake (14-20 mum size). This effectiveness (39 dB at 1.0 GHz) is attributed to the absorption of the electromagnetic wave by the mumetal and the nickel flake, with the high conductivity rendered by the presence of the nickel flake resulting in a relatively high reflection loss of 15.5 dB. Without the nickel flake, the mumetal gives only 3 dB of shielding and 1.5 dB of reflection loss at 1.0 GHz. Nickel powder (0.3-0.5 mum size) has been found to be an effective filler for improving the shielding of polyethersulfone (PES) bulk composites. At 13 vol.%, it gives 90 dB of shielding at 1.0 GHz, compared to 46 dB for nickel powder (20-40 mum) and the prior value of 87 dB reported by Shui and Chung for nickel filament (0.4 mum diameter). The minimum filler content for high shielding is 7-13 vol.% for both nickel powders, compared to 3-7 vol.% for nickel filament. Due to the skin effect, a small filler unit size helps the shielding, which is dominated by reflection. Carbon filament (0.1 mum, >100 mum long, >1000 in aspect ratio) is effective for enhancing the shielding effectiveness of a coating made from a water-based colloid that contains graphite particle (0.7-0.8 mum, 22 wt.%) and a starch-type binder. The filament addition increases the shielding from 11 to 20 dB at 1.0 GHz. This increase in shielding is associated with increase in reflectivity and decrease in electrical resistivity. Graphite flake (5 mum) at the same volume proportion is even more effective; its addition increases the shielding from 11 to 28 dB. The combined use of the graphite flake and a low proportion of stainless steel fiber (11 mum diameter, 2 mm long, 180 in aspect ratio) is yet more effective; it increases the shielding from 11 to 34 dB. Alumina particle (5 mum size, 15 vol.%) is effective for increasing the impedance of a coating made from the graphite colloid by 290%, though the shielding effectiveness is reduced from 18 to 11 dB at 1.0 GHz. The high impedance is attractive for MRIcompatible pacemaker leads. The interface between filler and matrix also affects the shielding. Silane treatment of the surface of graphite flake (5 mum) used in the graphite colloid decreases the viscosity (e.g., from 1750 to 1460 CP), but it also decreases the shielding effectiveness (e.g., from 20 to 16 dB at 1 GHz). Ozone treatment gives a similar effect. The decrease of the shielding effectiveness is attributed to the increase in resistivity due to the surface treatment. Measured and calculated values of the reflection loss are comparable, with the measured value lower than the corresponding calculated value, when the resistivity is sufficiently low (e.g., resistivity below 10 O.cm in case of PES-matrix composites) and a strongly magnetic filler such as mumetal is absent. The agreement is better when the skin depth approaches the specimen thickness. The agreement is worse for the latex paint-based composites than the PES-matrix composites, probably due to superior electrical connectivity in the latter.

Hypervelocity Impact Experiments on Epoxy/Ultra-High Molecular Weight Polyethylene Composite Panels Reinforced with Nanotubes

NASA Technical Reports Server (NTRS)

Khatiwada, Suman; Laughman, Jay W.; Armada, Carlos A.; Christiansen, Eric L.; Barrera, Enrique V.

2012-01-01

Advanced composites with multi-functional capabilities are of great interest to the designers of aerospace structures. Polymer matrix composites (PMCs) reinforced with high strength fibers provide a lightweight and high strength alternative to metals and metal alloys conventionally used in aerospace architectures. Novel reinforcements such as nanofillers offer potential to improve the mechanical properties and add multi-functionality such as radiation resistance and sensing capabilities to the PMCs. This paper reports the hypervelocity impact (HVI) test results on ultra-high molecular weight polyethylene (UHMWPE) fiber composites reinforced with single-walled carbon nanotubes (SWCNT) and boron nitride nanotubes (BNNT). Woven UHMWPE fabrics, in addition to providing excellent impact properties and high strength, also offer radiation resistance due to inherent high hydrogen content. SWCNT have exceptional mechanical and electrical properties. BNNT (figure 1) have high neutron cross section and good mechanical properties that add multi-functionality to this system. In this project, epoxy based UHMWPE composites containing SWCNT and BNNT are assessed for their use as bumper shields and as intermediate plates in a Whipple Shield for HVI resistance. Three composite systems are prepared to compare against one another: (I) Epoxy/UHMWPE, (II) Epoxy/UHMWPE/SWCNT and (III) Epoxy/UHMWPE/SWCNT/BNNT. Each composite is a 10.0 by 10.0 by 0.11 cm3 panel, consisting of 4 layers of fabrics arranged in cross-ply orientation. Both SWCNT and BNNT are 0.5 weight % of the fabric preform. Hypervelocity impact tests are performed using a two-stage light gas gun at Rice University

Composite films from pectin and fish skin gelatin or soybean flour protein.

PubMed

Liu, LinShu; Liu, Cheng-Kung; Fishman, Marshall L; Hicks, Kevin B

2007-03-21

Composite films were prepared from pectin and fish skin gelatin (FSG) or pectin and soybean flour protein (SFP). The inclusion of protein promoted molecular interactions, resulting in a well-organized homogeneous structure, as revealed by scanning electron microscopy and fracture-acoustic emission analysis. The resultant composite films showed an increase in stiffness and strength and a decrease in water solubility and water vapor transmission rate, in comparison with films cast from pectin alone. The composite films inherited the elastic nature of proteins, thus being more flexible than the pure pectin films. Treating the composite films with glutaraldehyde/methanol induced chemical cross-linking with the proteins and reduced the interstitial spaces among the macromolecules and, consequently, improved their mechanical properties and water resistance. Treating the protein-free pectin films with glutaraldehyde/methanol also improved the Young's modulus and tensile strength, but showed little effect on the water resistance, because the treatment caused only dehydration of the pectin films and the dehydration is reversible. The composite films were biodegradable and possessed moderate mechanical properties and a low water vapor transmission rate. Therefore, the films are considered to have potential applications as packaging or coating materials for food or drug industries.

Probabilistic Dynamic Buckling of Smart Composite Shells

NASA Technical Reports Server (NTRS)

Abumeri, Galib H.; Chamis, Christos C.

2003-01-01

A computational simulation method is presented to evaluate the deterministic and nondeterministic dynamic buckling of smart composite shells. The combined use of composite mechanics, finite element computer codes, and probabilistic analysis enable the effective assessment of the dynamic buckling load of smart composite shells. A universal plot is generated to estimate the dynamic buckling load of composite shells at various load rates and probabilities. The shell structure is also evaluated with smart fibers embedded in the plies right below the outer plies. The results show that, on the average, the use of smart fibers improved the shell buckling resistance by about 10 percent at different probabilities and delayed the buckling occurrence time. The probabilistic sensitivities results indicate that uncertainties in the fiber volume ratio and ply thickness have major effects on the buckling load while uncertainties in the electric field strength and smart material volume fraction have moderate effects. For the specific shell considered in this evaluation, the use of smart composite material is not recommended because the shell buckling resistance can be improved by simply re-arranging the orientation of the outer plies, as shown in the dynamic buckling analysis results presented in this report.

Probabilistic Dynamic Buckling of Smart Composite Shells

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Abumeri, Galib H.

2007-01-01

A computational simulation method is presented to evaluate the deterministic and nondeterministic dynamic buckling of smart composite shells. The combined use of intraply hybrid composite mechanics, finite element computer codes, and probabilistic analysis enable the effective assessment of the dynamic buckling load of smart composite shells. A universal plot is generated to estimate the dynamic buckling load of composite shells at various load rates and probabilities. The shell structure is also evaluated with smart fibers embedded in the plies right next to the outer plies. The results show that, on the average, the use of smart fibers improved the shell buckling resistance by about 10% at different probabilities and delayed the buckling occurrence time. The probabilistic sensitivities results indicate that uncertainties in the fiber volume ratio and ply thickness have major effects on the buckling load while uncertainties in the electric field strength and smart material volume fraction have moderate effects. For the specific shell considered in this evaluation, the use of smart composite material is not recommended because the shell buckling resistance can be improved by simply re-arranging the orientation of the outer plies, as shown in the dynamic buckling analysis results presented in this report.

Effect of Iron Impurity on the Phase Composition, Structure and Properties of Magnesium Alloys Containing Manganese and Aluminum

NASA Astrophysics Data System (ADS)

Volkova, E. F.

2017-07-01

Results of a study of the interaction between iron impurity and manganese and aluminum alloying elements during formation of phase composition in alloys of the Mg - Mn, Mg - Al, Mg - Al - Mn, and Mg - Al - Zn - Mn systems are presented. It is proved that this interaction results in introduction of Fe into the intermetallic phase. The phase compositions of model magnesium alloys and commercial alloys MA2-1 and MA5 are studied. It is shown that both manganese and aluminum may bind the iron impurity into phases. Composite Fe-containing intermetallic phases of different compositions influence differently the corrosion resistance of magnesium alloys.

Study on the Unsteady Creep of Composite Beams with an Irregular Laminar Fibrous Structure Made from Nonlinear Hereditary Materials

NASA Astrophysics Data System (ADS)

Yankovskii, A. P.

2017-09-01

The creep of homogenous and hybrid composite beams of an irregular laminar fibrous structure is investigated. The beams consist of thin walls and flanges (load-carrying layers). The walls may be reinforced longitudinally or crosswise in the plane, and the load-carrying layers are reinforced in the longitudinal direction. The mechanical behavior of phase materials is described by the Rabotnov nonlinear hereditary theory of creep taking into account their possible different resistance to tension and compression. On the basis of hypotheses of the Timoshenko theory, with using the method of time steps, a problem is formulated for the inelastic bending deformation of such beams with account of the weakened resistance of their walls to the transverse shear. It is shown that, at discrete instants of time, the mechanical behavior of such structures can formally be described by the governing relations for composite beams made of nonlinear elastic anisotropic materials with a known initial stress state. The method of successive iterations, similar to the method of variable parameters of elasticity, is used to linearize the boundary-value problem at each instant of time. The bending deformation is investigated for homogeneous and reinforced cantilever and simply supported beams in creep under the action of a uniformly distributed transverse load. The cross sections of the beams considered are I-shaped. It is found that the use of the classical theory for such beams leads to the prediction of indefensibly underestimated flexibility, especially in long-term loading. It is shown that, in beams with reinforced load-carrying layers, the creep mainly develops due to the shear strains of walls. It is found that, in short- and long-term loadings of composite beams, the reinforcement structures rational by the criterion of minimum flexibility are different.

High temperature structural sandwich panels

NASA Astrophysics Data System (ADS)

Papakonstantinou, Christos G.

High strength composites are being used for making lightweight structural panels that are being employed in aerospace, naval and automotive structures. Recently, there is renewed interest in use of these panels. The major problem of most commercial available sandwich panels is the fire resistance. A recently developed inorganic matrix is investigated for use in cases where fire and high temperature resistance are necessary. The focus of this dissertation is the development of a fireproof composite structural system. Sandwich panels made with polysialate matrices have an excellent potential for use in applications where exposure to high temperatures or fire is a concern. Commercial available sandwich panels will soften and lose nearly all of their compressive strength temperatures lower than 400°C. This dissertation consists of the state of the art, the experimental investigation and the analytical modeling. The state of the art covers the performance of existing high temperature composites, sandwich panels and reinforced concrete beams strengthened with Fiber Reinforced Polymers (FRP). The experimental part consists of four major components: (i) Development of a fireproof syntactic foam with maximum specific strength, (ii) Development of a lightweight syntactic foam based on polystyrene spheres, (iii) Development of the composite system for the skins. The variables are the skin thickness, modulus of elasticity of skin and high temperature resistance, and (iv) Experimental evaluation of the flexural behavior of sandwich panels. Analytical modeling consists of a model for the flexural behavior of lightweight sandwich panels, and a model for deflection calculations of reinforced concrete beams strengthened with FRP subjected to fatigue loading. The experimental and analytical results show that sandwich panels made with polysialate matrices and ceramic spheres do not lose their load bearing capability during severe fire exposure, where temperatures reach several hundred degrees Centigrade. Hence the material has excellent potential for various types of applications. The analytical predictions from both models provide reasonably accurate results. Glass, AR-glass, carbon and Nicalon tows and carbon fabrics could be successfully used as skin reinforcements increasing the flexural stiffness and strength of the core. No occurrence of fiber delamination was observed.

Improving the corrosion wear resistance of AISI 316L stainless steel by particulate reinforced Ni matrix composite alloying layer

NASA Astrophysics Data System (ADS)

Xu, Jiang; Zhuo, Chengzhi; Tao, Jie; Jiang, Shuyun; Liu, Linlin

2009-01-01

In order to overcome the problem of corrosion wear of AISI 316L stainless steel (SS), two kinds of composite alloying layers were prepared by a duplex treatment, consisting of Ni/nano-SiC and Ni/nano-SiO2 predeposited by brush plating, respectively, and subsequent surface alloying with Ni-Cr-Mo-Cu by a double glow process. The microstructure of the two kinds of nanoparticle reinforced Ni-based composite alloying layers was investigated by means of SEM and TEM. The electrochemical corrosion behaviour of composite alloying layers compared with the Ni-based alloying layer and 316L SS under different conditions was characterized by potentiodynamic polarization test and electrochemical impedance spectroscopy. Results showed that under alloying temperature (1000 °C) conditions, amorphous nano-SiO2 particles still retained the amorphous structure, whereas nano-SiC particles were decomposed and Ni, Cr reacted with SiC to form Cr6.5Ni2.5Si and Cr23C6. In static acidic solution, the corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiO2 particles interlayer is lower than that of the Ni-based alloying layer. However, the corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiO2 particles interlayer is prominently superior to that of the Ni-based alloying layer under acidic flow medium condition and acidic slurry flow condition. The corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiC particles interlayer is evidently lower than that of the Ni-based alloying layer, but higher than that of 316L SS under all test conditions. The results show that the highly dispersive nano-SiO2 particles are helpful in improving the corrosion wear resistance of the Ni-based alloying layer, whereas carbides and silicide phase are deleterious to that of the Ni-based alloying layer due to the fact that the preferential removal of the matrix around the precipitated phase takes place by the chemical attack of an aggressive medium.

Summary of the Effects of Two Years of Hygro-Thermal Cycling on a Carbon/Epoxy Composite Material

NASA Technical Reports Server (NTRS)

Kohlman, Lee W.; Binienda, Wieslaw K.; Roberts, Gary D.; Miller, Sandi G.; Pereira, J. Michael; Bail, Justin L.

2011-01-01

Composite materials are beginning to be used for structures in the fan section of commercial gas turbine engines. This paper explores the type of damage that could occur within one type of composite material after exposure to hygrothermal cycles (temperature/humidity cycles) that are representative of the environment in the fan section of an engine. The effect of this damage on composite material properties is measured. Chemical changes in the matrix material were limited to the exposed surface. Microcrack formation was identified in the composite material. This damage did not cause a significant reduction in tensile strength or impact penetration resistance of the composite material. Additional data is needed to assess the effect of damage on compressive strength.

Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

NASA Technical Reports Server (NTRS)

Gao, Xiujie; Burton, Deborah; Turner, Travis L.; Brinson, Catherine

2005-01-01

Shape memory alloy hybrid composites with adaptive-stiffening or morphing functions are simulated using finite element analysis. The composite structure is a laminated fiber-polymer composite beam with embedded SMA ribbons at various positions with respect to the neutral axis of the beam. Adaptive stiffening or morphing is activated via selective resistance heating of the SMA ribbons or uniform thermal loads on the beam. The thermomechanical behavior of these composites was simulated in ABAQUS using user-defined SMA elements. The examples demonstrate the usefulness of the methods for the design and simulation of SMA hybrid composites. Keywords: shape memory alloys, Nitinol, ABAQUS, finite element analysis, post-buckling control, shape control, deflection control, adaptive stiffening, morphing, constitutive modeling, user element

Fatigue resistance criteria for fiber-reinforced composite structures. Final report, 1 Apr 1971-30 Sep 1974

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dvorak, G.J.

1974-10-01

The research effort was concentrated on metal matrix composites, such as the Al--B, Al--Be, Cu--W, and similar systems. It was found that in as- fabricated composites with soft matrices fatigue failure can be prevented if the composite shakes down during cyclic loading. The fatigue strength of heat- treated composites is affected by residual microstresses, but failure can be prevented if the total microstresses are kept within the respective fatigue limits (at 10 to the 7th power cycles) of the constituents. These criteria for prevention of fatigue failure in metal matrix composite systems were verified by extensive comparisons of theoretical predictionsmore » with available experimental results. (GRA)« less

Prevalence of Antibiotic Resistance Genes and Bacterial Community Composition in a River Influenced by a Wastewater Treatment Plant

PubMed Central

Marti, Elisabet; Jofre, Juan; Balcazar, Jose Luis

2013-01-01

Antibiotic resistance represents a global health problem, requiring better understanding of the ecology of antibiotic resistance genes (ARGs), their selection and their spread in the environment. Antibiotics are constantly released to the environment through wastewater treatment plant (WWTP) effluents. We investigated, therefore, the effect of these discharges on the prevalence of ARGs and bacterial community composition in biofilm and sediment samples of a receiving river. We used culture-independent approaches such as quantitative PCR to determine the prevalence of eleven ARGs and 16S rRNA gene-based pyrosequencing to examine the composition of bacterial communities. Concentration of antibiotics in WWTP influent and effluent were also determined. ARGs such as qnrS, bla TEM, bla CTX-M, bla SHV, erm(B), sul(I), sul(II), tet(O) and tet(W) were detected in all biofilm and sediment samples analyzed. Moreover, we observed a significant increase in the relative abundance of ARGs in biofilm samples collected downstream of the WWTP discharge. We also found significant differences with respect to community structure and composition between upstream and downstream samples. Therefore, our results indicate that WWTP discharges may contribute to the spread of ARGs into the environment and may also impact on the bacterial communities of the receiving river. PMID:24205347

Enhanced photoelectrochemical water splitting by oxides heterojunction photocathode coupled with Ag.

PubMed

Lu, Xue; Liu, Zhifeng

2017-08-14

A novel one-dimensional Co 3 O 4 /CuO/Ag composite structure film was directly grown on indium tin oxide glass substrate by a simple hydrothermal method and electrodeposition method. The film was employed for the first time as a photocathode for photoelectrochemical (PEC) water splitting to generate hydrogen. The photocurrent density of the Co 3 O 4 /CuO/Ag composite structure achieved -5.13 mA cm -2 at -0.2 V vs. RHE, which is roughly 12.8 times that of 1D Co 3 O 4 nanowires and 3.31 times Co 3 O 4 /CuO heterojunction photocathodes. The enhanced PEC performance of this Co 3 O 4 /CuO/Ag composite structure ascribes increased light-harvesting and light-absorption, distensible photoresponse range, decreased interface charge transfer resistance, and improved photogenerated electron-hole pairs transfer and separation.

Influences of surface modification of nano-silica by silane coupling agents on the thermal and frictional properties of cyanate ester resin

NASA Astrophysics Data System (ADS)

Chuang, Wang; Geng-sheng, Jiao; Lei, Peng; Bao-lin, Zhu; Ke-zhi, Li; Jun-long, Wang

2018-06-01

The surface of nano-silicon dioxide (nano-SiO2) particles was modified by small molecular coupling agent KH-560 and macromolecular coupling agent SEA-171, respectively, to change the surface activity and structure. The modified nano-SiO2 was then used for reinforcing cyanate ester resin (CE). Influences of the content of nano-SiO2 and the interfacial structure over the thermal and frictional properties of nano-SiO2/CE composites were investigated. The mechanism of the surface modification of silicon dioxide by KH-560 and SEA-171 was discussed. The experimental results show that the addition of coupling agents increased the interfacial bonding between nano-SiO2 particles and the CE resin so that the heat resistance and friction properties of the composites were improved. After surface treatment of nano-SiO2 by SEA-171, the thermal decomposition temperature of the 3.0 wt% nano-SiO2/CE composites increased nearly by 75 °C and the frictional coefficient was reduced by 25% compared with that of the pure CE, and the wear resistance increased by 77%.

Experimental and simulation of split semi-torus key in PVC foam core to improve the debonding resistance of composite sandwich panel

NASA Astrophysics Data System (ADS)

Juliyana, M.; Santhana Krishnan, R.

2018-02-01

The sandwich composite panels consisting of facesheet and core material are used as a primary structural member for aerospace, civil and marine areas due to its high stiffness to weight ratio. But the debonding nature of facesheet from the foam core under shear loading conditions leads to failure of the composite structure. To inhibit the debonding, an innovative methodology of introducing semi-torus key is used in the present study. The polyvinyl chloride foam core(PVC) is grooved and filled with semi-torus shaped chopped strand prepregs which are sandwiched between alternate layers of woven roven(WR) and chopped strand mat(CSM) skins by vacuum infusion process. The sandwich panel manufactured with semi-torus keys is evaluated regarding experimental and numerical simulations under shear loading conditions. The present innovative concept delays the debonding between face-sheet and foam core with enhancement the shear load carrying capability as the initial stiffness is higher than the conventional model. Also, the shear behaviour of the proposed concept is in good agreement with experimental results. The split semi-torus keys sustain the shear failure resulting in resistance to debonding capability.

Application of fiber-reinforced bismaleimide materials to aircraft nacelle structures

NASA Technical Reports Server (NTRS)

Peros, Vasilios; Ruth, John; Trawinski, David

1992-01-01

Existing aircraft engine nacelle structures employ advanced composite materials to reduce weight and thereby increase overall performance. Use of advanced composite materials on existing aircraft nacelle structures includes fiber-reinforced epoxy structures and has typically been limited to regions furthest away from the hot engine core. Portions of the nacelle structure that are closer to the engine require materials with a higher temperature capability. In these portions, existing nacelle structures employ aluminum sandwich construction and skin/stringer construction. The aluminum structure is composed of many detail parts and assemblies and is usually protected by some form of ablative, insulator, or metallic thermal shield. A one-piece composite inner cowl for a new-generation engine nacelle structure has been designed using fiber-reinforced bismaleimide (BMI) materials and honeycomb core in a sandwich construction. The new composite design has many advantages over the existing aluminum structure. Multiple details were integrated into the one-piece composite design, thereby significantly reducing the number of detail parts and fasteners. The use of lightweight materials and the reduction of the number of joints result in a significant weight reduction over the aluminum design; manufacturing labor and the overall number of tools required have also been reduced. Several significant technical issues were addressed in the development of a BMI composite design. Technical evaluation of the available BMI systems led to the selection of a toughened BMI material which was resistant to microcracking under thermal cyclic loading and enhanced the damage tolerance of the structure. Technical evaluation of the degradation of BMI materials in contact with aluminum and other metals validated methods for isolation of the various materials. Graphite-reinforced BMI in contact with aluminum and some steels was found to degrade in salt spray testing. Isolation techniques such as those used for graphite-reinforced epoxy structures were shown to provide adequate protection. The springback and producibility of large BMI structures were evaluated by manufacturing prototype hardware which had the full-scale cross section of the one-piece composite structure.

Multi-physics damage sensing in nano-engineered structural composites.

PubMed

de Villoria, Roberto Guzmán; Yamamoto, Namiko; Miravete, Antonio; Wardle, Brian L

2011-05-06

Non-destructive evaluation techniques can offer viable diagnostic and prognostic routes to mitigating failures in engineered structures such as bridges, buildings and vehicles. However, existing techniques have significant drawbacks, including poor spatial resolution and limited in situ capabilities. We report here a novel approach where structural advanced composites containing electrically conductive aligned carbon nanotubes (CNTs) are ohmically heated via simple electrical contacts, and damage is visualized via thermographic imaging. Damage, in the form of cracks and other discontinuities, usefully increases resistance to both electrical and thermal transport in these materials, which enables tomographic full-field damage assessment in many cases. Characteristics of the technique include the ability for real-time measurement of the damage state during loading, low-power operation (e.g. 15 °C rise at 1 W), and beyond state-of-the-art spatial resolution for sensing damage in composites. The enhanced thermographic technique is a novel and practical approach for in situ monitoring to ascertain structural health and to prevent structural failures in engineered structures such as aerospace and automotive vehicles and wind turbine blades, among others.

Multi-physics damage sensing in nano-engineered structural composites

NASA Astrophysics Data System (ADS)

Guzmán de Villoria, Roberto; Yamamoto, Namiko; Miravete, Antonio; Wardle, Brian L.

2011-05-01

Non-destructive evaluation techniques can offer viable diagnostic and prognostic routes to mitigating failures in engineered structures such as bridges, buildings and vehicles. However, existing techniques have significant drawbacks, including poor spatial resolution and limited in situ capabilities. We report here a novel approach where structural advanced composites containing electrically conductive aligned carbon nanotubes (CNTs) are ohmically heated via simple electrical contacts, and damage is visualized via thermographic imaging. Damage, in the form of cracks and other discontinuities, usefully increases resistance to both electrical and thermal transport in these materials, which enables tomographic full-field damage assessment in many cases. Characteristics of the technique include the ability for real-time measurement of the damage state during loading, low-power operation (e.g. 15 °C rise at 1 W), and beyond state-of-the-art spatial resolution for sensing damage in composites. The enhanced thermographic technique is a novel and practical approach for in situ monitoring to ascertain structural health and to prevent structural failures in engineered structures such as aerospace and automotive vehicles and wind turbine blades, among others.

The effect of heat treatment simulating porcelain firing processes on titanium corrosion resistance.

PubMed

Sokołowski, Grzegorz; Rylska, Dorota; Sokołowski, Jerzy

2016-01-01

Corrosion resistance of titanium used in metal-ceramic restorations in manufacturing is based on the presence of oxide layer on the metal surface. The procedures used during combining metallic material with porcelain may affect the changes in oxide layers structure, and thus anticorrosive properties of metallic material. The aim of the study was an evaluation of potential changes in the structure and selected corrosion properties of titanium after sandblasting and thermal treatment applicable to the processes of ceramics fusion. Milled titanium elements were subjected to a few variants of the processes typical of ceramics fusion and studied in terms of resistance to electrochemical corrosion. The study included the OCP changes over time, measurements of Icorr, Ecorr and Rp as well as potentiodynamic examinations. Surface microstructure and chemical composition were analyzed using SEM and EDS methods. The results obtained allow us to conclude that the processes corresponding to ceramic oxidation and fusion on titanium in the variants used in the study do not cause deterioration of its anticorrosive properties, and partially enhance the resistance. This depends on the quality of oxide layers structure. Titanium elements treated by porcelain firing processes do not lose their corrosion resistance.

High temperature insulation barrier composite

NASA Technical Reports Server (NTRS)

Onstott, Joseph W. (Inventor)

1989-01-01

A composite material suitable for providing insulation for the nozzle structure of the Space Shuttle and other similar surfaces is disclosed. The composite layer is comprised of an outer skin layer of nickel chromium and an interleaved inner region comprising a top layer of nickel chromium foil which acts as a primary convective shield. There are at least two layers of alumina batting adjacent to the layers of silicon carbide fabric. An additional layer of nickel chromium foil is used as a secondary convective shield. The composite is particularly advantageous for use as nozzle insulation because of its ability to withstand high reentry temperatures, its flexibility, oxidation resistance, low conductivity, and light weight.

Fabrication and testing of prestressed composite rotor blade spar specimens

NASA Technical Reports Server (NTRS)

Gleich, D.

1974-01-01

Prestressed composite spar specimens were fabricated and evaluated by crack propagation and ballistic penetration tests. The crack propagation tests on flawed specimens showed that the prestressed composite spar construction significantly suppresses crack growth. Damage from three high velocity 30 caliber projectile hits was confined to three small holes in the ballistic test specimen. No fragmentation or crack propagation was observed indicating good ballistic damage resistance. Rotor attachment approaches and improved structural performance configurations were identified. Design theory was verified by tests. The prestressed composite spar configuration consisted of a compressively prestressed high strength ARDEFORM 301 stainless steel liner overwrapped with pretensioned S-994 fiberglass.

Temperature Dependences of the Product of the Differential Resistance by the Area in MIS-Structures Based on Cd x Hg1- x Te Grown by Molecularbeam Epitaxy on Alternative Si and GaAs Substrates

NASA Astrophysics Data System (ADS)

Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.; Varavin, V. S.; Vasil'ev, V. V.; Dvoretskii, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Sidorov, G. Yu.

2017-06-01

In a temperature range of 9-200 K, temperature dependences of the differential resistance of space-charge region in the strong inversion mode are experimentally studied for MIS structures based on CdxHg1-xTe (x = 0.22-0.40) grown by molecular-beam epitaxy. The effect of various parameters of structures: the working layer composition, the type of a substrate, the type of insulator coating, and the presence of a near-surface graded-gap layer on the value of the product of differential resistance by the area is studied. It is shown that the values of the product RSCRA for MIS structures based on n-CdHgTe grown on a Si(013) substrate are smaller than those for structures based on the material grown on a GaAs(013) substrate. The values of the product RSCRA for MIS structures based on p-CdHgTe grown on a Si(013) substrate are comparable with the value of the analogous parameter for MIS structures based on p-CdHgTe grown on a GaAs(013) substrate.

Impact Resistance of Lightweight Hybrid Structures for Gas Turbine Engine Fan Containment Applications

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G.; Noebe, Ronald D.; Revilock, Duane M.

2003-01-01

The ballistic impact resistance of hybrid composite sandwich structures was evaluated with the ultimate goal of developing new materials or structures for potential gas turbine engine fan containment applications. The sandwich structures investigated consisted of GLARE-5 laminates as face sheets with lightweight cellular metallic materials such as honeycomb, foam, and lattice block as a core material. The impact resistance of these hybrid sandwich structures was compared to GLARE-5 laminates and 2024-T3 Al sheet, which were tested as a function of areal weight (material thickness). The GLARE-5 laminates exhibited comparable impact properties to that of 2024-T3 Al at low areal weights, even though there were significant differences in the static tensile properties of these materials. The GLARE-5, however, did have a greater ballistic limit than straight aluminum sheet at higher areal weights. Furthermore, there is up to a 25% advantage in ballistic limit for the GLARE-5/foam sandwich structures compared to straight 2024-T3 Al. But no advantage in ballistic limit was observed between any of the hybrid sandwich structures and thicker versions of GLARE-5. Recommendations for future work are provided, based on these preliminary data.

Lightweight Thermal Protection System for Atmospheric Entry

NASA Technical Reports Server (NTRS)

Stewart, David; Leiser, Daniel

2007-01-01

TUFROC (Toughened Uni-piece Fibrous Reinforced Oxidation-resistant Composite) has been developed as a new thermal protection system (TPS) material for wing leading edge and nose cap applications. The composite withstands temperatures up to 1,970 K, and consists of a toughened, high-temperature surface cap and a low-thermal-conductivity base, and is applicable to both sharp and blunt leading edge vehicles. This extends the possible application of fibrous insulation to the wing leading edge and/or nose cap on a hypersonic vehicle. The lightweight system comprises a treated carbonaceous cap composed of ROCCI (Refractory Oxidation-resistant Ceramic Carbon Insulation), which provides dimensional stability to the outer mold line, while the fibrous base material provides maximum thermal insulation for the vehicle structure.

Development of load and resistance factor design for FRP strengthening of reinforced concrete bridges.

DOT National Transportation Integrated Search

2006-05-01

Externally bonded fiber reinforced polymer (FRP) composites are an increasingly adopted technology for the renewal of existing concrete structures. In order to encourage the further use of these materials, a design code is needed that considers the i...

High-entropy Alloys with High Saturation Magnetization, Electrical Resistivity, and Malleability

PubMed Central

Zhang, Yong; Zuo, TingTing; Cheng, YongQiang; Liaw, Peter K.

2013-01-01

Soft magnetic materials (SMMs) find important applications in a number of areas. The diverse requirements for these applications are often demanding and challenging for the design and fabrication of SMMs. Here we report a new class of FeCoNi(AlSi)x (0 ≤ x ≤ 0.8 in molar ratio) SMMs based on high-entropy alloys (HEAs). It is found that with the compositional and structural changes, the optimal balance of magnetic, electrical, and mechanical properties is achieved at x = 0.2, for which the combination of saturation magnetization (1.15 T), coercivity (1,400 A/m), electrical resistivity (69.5 μΩ·cm), yield strength (342 MPa), and strain without fracture (50%) makes the alloy an excellent SMM. Ab initio calculations are used to explain the high magnetic saturation of the present HEAs and the effects of compositional structures on magnetic characteristics. The HEA-based SMMs point to new directions in both the application of HEAs and the search for novel SMMs. PMID:23492734

Corrosion behavior of a superduplex stainless steel in chloride aqueous solution

NASA Astrophysics Data System (ADS)

Dabalà, Manuele; Calliari, Irene; Variola, Alessandra

2004-04-01

Super duplex stainless steels (SDSS) have been widely used as structural materials for chemical plants (especially in those engaged in phosphoric acid production), in the hydrometallurgy industries, and as materials for offshore applications due to their excellent corrosion resistance in chloride environments, compared with other commercial types of ferritic stainless steels. These alloys also possess superior weldability and better mechanical properties than austenitic stainless steels. However, due to their two-phase structure, the nature of which is very dependent on their composition and thermal history, the behavior of SDSS regarding localized corrosion appears difficult to predict, especially in chloride environments. To improve their final properties, the effect of the partition of the alloying elements between the two phases, and the composition and microstructure of each phase are the key to understanding the localized corrosion phenomena of SDSS. This paper concerns the effects of the SDSS microstructure and heat treatment on the SDSS corrosion resistance in aqueous solutions, containing different amounts of NaCl at room temperature.

Novel matrix resins for composites for aircraft primary structures, phase 1

NASA Technical Reports Server (NTRS)

Woo, Edmund P.; Puckett, P. M.; Maynard, S.; Bishop, M. T.; Bruza, K. J.; Godschalx, J. P.; Mullins, M. J.

1992-01-01

The objective of the contract is the development of matrix resins with improved processability and properties for composites for primarily aircraft structures. To this end, several resins/systems were identified for subsonic and supersonic applications. For subsonic aircraft, a series of epoxy resins suitable for RTM and powder prepreg was shown to give composites with about 40 ksi compressive strength after impact (CAI) and 200 F/wet mechanical performance. For supersonic applications, a thermoplastic toughened cyanate prepreg system has demonstrated excellent resistance to heat aging at 360 F for 4000 hours, 40 ksi CAI and useful mechanical properties at greater than or equal to 310 F. An AB-BCB-maleimide resin was identified as a leading candidate for the HSCT. Composite panels fabricated by RTM show CAI of approximately 50 ksi, 350 F/wet performance and excellent retention of mechanical properties after aging at 400 F for 4000 hours.

Investigation on the relationship between NbC and wear-resistance of Fe matrix composite coatings with different C contents

NASA Astrophysics Data System (ADS)

Zhao, Changchun; Zhou, Yefei; Xing, Xiaolei; Liu, Sha; Ren, Xuejun; Yang, Qingxiang

2018-05-01

The wear resistance of Fe-based composite coating is significantly related with the character of carbides and matrix, which could be strongly affected by C content in it. In this work, the Fe-based composite coatings with different C contents were prepared. The microstructure and phase structure of the coatings were analyzed by scanning electron microscope (SEM) equipped with an energy-dispersive spectroscopy (EDS) and X-ray diffractometer (XRD). The hardness and wear resistance of the coatings were determined. Then the hardness and brittleness of carbon poor niobium carbides were calculated by first principles calculation. The results show that, the phase structures of the coatings are mainly composed of NbC, γ phase (retained austenite) and α phase (martensite). With the increase of C content, the retained austenite appears and C content of martensite is increased. The hardness of the coatings are increased from HRC 22 to HRC 59. The distribution and morphology of NbC are changed with the increase of C content. The NbC precipitated in reticular grain boundary can be observed when C content is 0.4 wt.% C (C-1). NbC turn into granular and small rod morphology when C content increases to 0.8 wt.% C (C-2). The cracks and defects cannot been found on the surface of the coating when C content is 1.2 wt.% C(C-3), whose hardness is HRC 58 and wear loss is 0.27 g/N cm2 in 8 h. The flaky M7C3 carbide precipitates on the coating when C content is 1.4 wt.% C(C-4), which weaken the wear resistance of the matrix. Compared with the hardfacing coatings with different C contents, the C-3 coating processes higher hardness and wear resistance.

Structural optimization and amorphous calcium phosphate mineralization in sensory setae of a terrestrial crustacean (Isopoda: Oniscidea).

PubMed

Vittori, Miloš; Srot, Vesna; Bussmann, Birgit; Predel, Felicitas; van Aken, Peter A; Štrus, Jasna

2018-06-09

Terrestrial isopods possess large sensory setae on their walking legs. Increased fracture resistance of these elongated structures is of crucial importance, making the exoskeleton forming the setae an interesting durable material that may inspire biomimetic designs. We studied the cuticle of the sensory setae with analytical electron microscopy in order to gain detailed insights into its structure and composition at the nanometer scale and identify features that increase the fracture resistance of these minute skeletal elements. The setae are stiff structures formed by mineralized cuticle that are connected to the leg exoskeleton by a non-mineralized joint membrane. Our results demonstrate that different layers of the setal cuticle display contrasting organizations of the chitin-protein fibers and mineral particles. While in the externally positioned exocuticle organic fibers shift their orientation helicoidally in sequential layers, the fibers are aligned axially in the internally positioned endocuticle. In the setal cuticle, layers of structurally anisotropic cuticle likely providing strength in the axial direction are combined with layers of isotropic cuticle which may allow the setae to better resist perpendicular loading. They are further strengthened with amorphous calcium phosphate, a highly fracture resistant mineral rarely observed in invertebrate skeletons. Copyright © 2018 Elsevier Ltd. All rights reserved.

The impact of a 12-week resistance training program on strength, body composition, and self-concept of Hispanic adolescents.

PubMed

Velez, Amelia; Golem, Devon L; Arent, Shawn M

2010-04-01

Current evidence suggests that a resistance training program may be physically and psychologically beneficial for adolescents. The purpose of this study was to examine the effects of a structured resistance training program on strength, body composition, and self-concept in normal and overweight Hispanic adolescents. Male and female participants (n = 28; 16.1 +/- 0.2 y; 164.5 +/- 1.4 cm; 63.3 +/- 2.5 kg; 20.0 +/- 1.7% body fat [BF]) were recruited from a predominantly Hispanic high school. Prior to the 12-week program, strength, body composition, and self-concept were assessed. Subjects were randomly assigned to a control group (CON; n = 15) or to a resistance training group (RT; n = 13) that participated in supervised strength training 3 days/week. All measures were repeated at the end of the 12-week program. RT had significantly greater strength increases for bench press (p < 0.001), seated row (p = 0.002), shoulder press (p < 0.001), and squats (p = 0.002). RT had significant reductions in %BF (p = 0.001), whereas CON had slightly increased %BF. RT had an increase in condition/stamina competence (p = 0.008), attractive body adequacy (p = 0.017), and global self-worth (p = 0.013) from pretest to posttest, whereas no change was observed for CON. In conclusion, resistance training resulted in significant physiological and psychological improvements in Hispanic adolescents compared to typical school-based activities. These findings indicate that resistance training can be incorporated into the activities of Hispanic adolescents to promote improved health and fitness.

An Investigation on the Use of a Laser Ablation Treatment on Metallic Surfaces and the Influence of Temperature on Fracture Toughness of Hybrid Co-Cured Metal-PMC Interfaces

NASA Technical Reports Server (NTRS)

Connell, John; Palmieri, Frank; Truong, Hieu; Ochoa, Ozden; Lagoudas, Dimitris

2015-01-01

Hybrid composite laminates that contain alternating layers of titanium alloys and carbon fabric reinforced polyimide matrix composites (PMC) are excellent candidates for light-weight, high-temperature structural materials for high-speed aerospace vehicles. The delamination resistance of the hybrid titanium-PMC interface is of crucial consideration for structural integrity during service. Here, we report the first investigations on the use of laser ablation in combination with sol-gel treatment technique on Ti/NiTi foil surfaces in co-cured hybrid polyimide matrix composite laminates. Mode-I and mode-II fracture toughness of the hybrid Ti/NiTi-PMC interface as a function of temperature were determined via experimental testing and finite element analysis.

Experimental study of the fracture toughness of a ceramic/ceramic-matrix composite sandwich structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Z.; Taya, M.; Dunn, M.L.

A hybrid experimental-numerical approach has been used to measure the fracture resistance of a sandwich structure consisting of a 304 stainless steel/partially stabilized zirconia ceramic-matrix composite crack-arresting layer embedded in a partially stabilized zirconia ceramic specimen. The mode 1 fracture toughness increases significantly when the crack propagates from the ceramic into the ceramic-matrix composite region. The increased toughening due to the stainless steel particles is explained reasonably well by a toughening model based on processing-induced thermal residual stresses. In addition, several experimental modifications were made to the chevron-notch wedge-loaded double cantilever beam specimen to overcome numerous problems encountered in generatingmore » a precrack in the small, brittle specimens used in this study.« less

Toughened uni-piece, fibrous, reinforced, oxidization-resistant composite

NASA Technical Reports Server (NTRS)

Stewart, David A. (Inventor); Leiser, Daniel B. (Inventor)

2008-01-01

A composite thermal protection structure, for applications such as atmospheric re-entry vehicles, that can withstand temperatures as high as 3600.degree. F. The structure includes an exposed surface cap having a specially formulated coating, an insulator base adjacent to the cap with another specially formulated coating, and one or more pins that extend from the cap through the insulator base to tie the cap and base together, through ceramic bonding and mechanical attachment. The cap and insulator base have corresponding depressions and projections that mate and allow for differences in thermal expansion of the cap and base. A thin coating of a reaction cured glass formulation is optionally provided on the structure to allow reduce oxidization and/or to reduce catalytic efficiency.

Integrated thick-film nanostructures based on spinel ceramics

PubMed Central

2014-01-01

Integrated temperature-humidity-sensitive thick-film structures based on spinel-type semiconducting ceramics of different chemical compositions and magnesium aluminate ceramics were prepared and studied. It is shown that temperature-sensitive thick-film structures possess good electrophysical characteristics in the region from 298 to 358 K. The change of electrical resistance in integrated thick-film structures is 1 order, but these elements are stable in time and can be successfully used for sensor applications. PMID:24670141

High diversity in SCCmec elements among multidrug-resistant Staphylococcus haemolyticus strains originating from paediatric patients; characterization of a new composite island.

PubMed

Hosseinkhani, Farideh; Tammes Buirs, Matthias; Jabalameli, Fereshteh; Emaneini, Mohammad; van Leeuwen, Willem B

2018-06-06

Staphylococcus haemolyticus has emerged as a highly antimicrobial-resistant healthcare-associated pathogen, in particular for patients admitted to neonatal intensive care. The objective of this study was to study the nature of SCCmec types among MDR-SH strains isolated from paediatric patients. S. haemolyticus strains (n=60) were isolated from paediatric patients. Antibiotic resistance patterns were established using the disk agar diffusion and micro-broth dilution methods. SCCmec typing was performed using whole-genome sequencing (WGS) and an additional PCR analysis. All S. haemolyticus isolates demonstrated multidrug resistance. Using WGS, various novel mec types and combinations of SCCmec types were found, including a new composite island [SCCmec type V (Vd)+SCC cad/ars/cop] comprising 30 % of the strains. SCCmec type V was identified in 23 % of the isolates. A combination of the mecA gene enclosed by two copies of IS431 and absence of the mecRI and ccr genes was identified in 11 strains. In total, mecA regulatory genes were absent in all SH isolates used in this study. A high diversity of SCCmec elements with the prevalence of a new composite island was determined among MRSH strains. The structure of the composite island represented by MDR-SH strains in this study, in combination with the presence of a restriction-modification system type III, is described for the first time in this study. The presence of an 8 bp direct repeat (DR) and the sequences flanking the DR may support the integration of the mecA gene complex as a composite transposon (IS431-mecA-IS431) independently from recombinase genes.

Multi-Dimensional Damage Detection for Surfaces and Structures

NASA Technical Reports Server (NTRS)

Williams, Martha; Lewis, Mark; Roberson, Luke; Medelius, Pedro; Gibson, Tracy; Parks, Steen; Snyder, Sarah

2013-01-01

Current designs for inflatable or semi-rigidized structures for habitats and space applications use a multiple-layer construction, alternating thin layers with thicker, stronger layers, which produces a layered composite structure that is much better at resisting damage. Even though such composite structures or layered systems are robust, they can still be susceptible to penetration damage. The ability to detect damage to surfaces of inflatable or semi-rigid habitat structures is of great interest to NASA. Damage caused by impacts of foreign objects such as micrometeorites can rupture the shell of these structures, causing loss of critical hardware and/or the life of the crew. While not all impacts will have a catastrophic result, it will be very important to identify and locate areas of the exterior shell that have been damaged by impacts so that repairs (or other provisions) can be made to reduce the probability of shell wall rupture. This disclosure describes a system that will provide real-time data regarding the health of the inflatable shell or rigidized structures, and information related to the location and depth of impact damage. The innovation described here is a method of determining the size, location, and direction of damage in a multilayered structure. In the multi-dimensional damage detection system, layers of two-dimensional thin film detection layers are used to form a layered composite, with non-detection layers separating the detection layers. The non-detection layers may be either thicker or thinner than the detection layers. The thin-film damage detection layers are thin films of materials with a conductive grid or striped pattern. The conductive pattern may be applied by several methods, including printing, plating, sputtering, photolithography, and etching, and can include as many detection layers that are necessary for the structure construction or to afford the detection detail level required. The damage is detected using a detector or sensory system, which may include a time domain reflectometer, resistivity monitoring hardware, or other resistance-based systems. To begin, a layered composite consisting of thin-film damage detection layers separated by non-damage detection layers is fabricated. The damage detection layers are attached to a detector that provides details regarding the physical health of each detection layer individually. If damage occurs to any of the detection layers, a change in the electrical properties of the detection layers damaged occurs, and a response is generated. Real-time analysis of these responses will provide details regarding the depth, location, and size estimation of the damage. Multiple damages can be detected, and the extent (depth) of the damage can be used to generate prognostic information related to the expected lifetime of the layered composite system. The detection system can be fabricated very easily using off-the-shelf equipment, and the detection algorithms can be written and updated (as needed) to provide the level of detail needed based on the system being monitored. Connecting to the thin film detection layers is very easy as well. The truly unique feature of the system is its flexibility; the system can be designed to gather as much (or as little) information as the end user feels necessary. Individual detection layers can be turned on or off as necessary, and algorithms can be used to optimize performance. The system can be used to generate both diagnostic and prognostic information related to the health of layer composite structures, which will be essential if such systems are utilized for space exploration. The technology is also applicable to other in-situ health monitoring systems for structure integrity.

An Investigation of SiC/SiC Woven Composite Under Monotonic and Cyclic Loading

NASA Technical Reports Server (NTRS)

Lang, J.; Sankar, J.; Kelkar, A. D.; Bhatt, R. T.; Singh, M.; Lua, J.

1997-01-01

The desirable properties in ceramic matrix composites (CMCs), such as high temperature strength, corrosion resistance, high toughness, low density, or good creep resistance have led to increased use of CMCs in high-speed engine structural components and structures that operate in extreme temperature and hostile aero-thermo-chemical environments. Ceramic matrix composites have been chosen for turbine material in the design of 21 st-century civil propulsion systems to achieve high fuel economy, improved reliability, extended life, and reduced cost. Most commercial CMCs are manufactured using a chemical vapor infiltration (CVI) process. However, a lower cost fabrication known as melt-infiltration process is also providing CMCs marked for use in hot sections of high-speed civil transports. The scope of this paper is to report on the material and mechanical characterization of the CMCs subjected to this process and to predict the behavior through an analytical model. An investigation of the SiC/SiC 8-harness woven composite is ongoing and its tensile strength and fatigue behavior is being characterized for room and elevated temperatures. The investigation is being conducted at below and above the matrix cracking stress once these parameters are identified. Fractography and light microscopy results are being studied to characterize the failure modes resulting from pure uniaxial loading. A numerical model is also being developed to predict the laminate properties by using the constituent material properties and tow undulation.

Investigation of Structural Properties of Carbon-Epoxy Composites Using Embedded Fiber-Optic Bragg Gratings

NASA Technical Reports Server (NTRS)

Osei, Albert J.

2003-01-01

Real time monitoring of the mechanical integrity and stresses on key aerospace composite structures like aircraft wings, walls of pressure vessels and fuel tanks or any other structurally extended components and panels as in space telescopes is very important to NASA. Future military and commercial aircraft as well as NASA space systems such as Space Based Radar and International Space Station will incorporate a monitoring system to sense any degradation to the structure. In the extreme flight conditions of an aerospace vehicle it might be desirable to measure the strain every ten centimeters and thus fully map out the strain field of a composite component. A series of missions and vehicle health management requirements call for these measurements. At the moment thousands of people support a few vehicle launches per year. This number can be significantly reduced by implementing intelligent vehicles with integral nervous systems (smart structures). This would require maintenance to be performed only as needed. Military and commercial aircrafts have an equally compelling case. Annual maintenance costs are currently reaching astronomical heights. Monitoring techniques are therefore required that allow for maintenance to be performed only when needed. This would allow improved safety by insuring that necessary tasks are performed while reducing costs by eliminating procedures that are costly and not needed. The advantages fiber optical sensors have over conventional electro-mechanical systems like strain gauges have been widely extolled in the research literature. These advantages include their small size, low weight, immunity to electrical resistance, corrosion resistance, compatibility with composite materials and process conditions, and multiplexing capabilities. One fiber optic device which is suitable for distributed sensing is the fiber Bragg grating (FBG). This is a periodic perturbation in the refractive index of the fiber core. When a broadband light is coupled into the optical fiber sensor, a reflection peak will be obtained centered around a wavelength called Bragg-wavelength. The Bragg-wavelength depends on the refractive index and the period of the grating, which both change due to mechanical and thermal strain applied to the sensor. The shift in the Bragg-wavelength is directly proportional to the strain. Researchers at NASA MSFC are currently developing techniques for using FBGs for monitoring the integrity of advanced structural materials expected to become the mainstay of the current and future generation space structures. Since carbon-epoxy composites are the materials of choice for the current space structures, the initial study is concentrated on this type of composite. The goals of this activity are to use embedded FBG sensors for measuring strain and temperature of composite structures, and to investigate the effects of various parameters such as composite fiber orientation with respect to the optical sensor, unidirectional fiber composite, fabrication process etc., on the optical performance of the sensor. This paper describes an experiment to demonstrate the use of an embedded FBG for measuring strain in a composite material. The performance of the fiber optic sensor is determined by direct comparison with results from more conventional instrumentation.

Enhancement of the in-plane shear properties of carbon fiber composites containing carbon nanotube mats

NASA Astrophysics Data System (ADS)

Kim, Hansang

2015-01-01

The in-plane shear property of carbon fiber laminates is one of the most important structural features of aerospace and marine structures. Fiber-matrix debonding caused by in-plane shear loading is the major failure mode of carbon fiber composites because of the stress concentration at the interfaces. In this study, carbon nanotube mats (CNT mat) were incorporated in two different types of carbon fiber composites. For the case of woven fabric composites, mechanical interlocking between the CNTs and the carbon fibers increased resistance to shear failure. However, not much improvement was observed for the prepreg composites as a result of incorporation of the CNT mats. The reinforcement mechanism of the CNT mat layer was investigated by a fractographic study using scanning electron microscopy. In addition, the CNT mat was functionalized by three different methods and the effectiveness of the functionalization methods was determined and the most appropriate functionalization method for the CNT mat was air oxidation.

Effect of CFRC layers on the electrical properties and failure mode of RC beams strengthened with CFRC composites

NASA Astrophysics Data System (ADS)

Wu, Sigang; Dai, Hongzhe; Wang, Wei

2007-12-01

This paper designs an innovative reinforced concrete (RC) beam strengthened with carbon fiber reinforced concrete (CFRC) composites. Six groups of test beams, five with different degrees of strengthening, achieved by changing the location and the thickness of the CFRC layer, and one virgin RC beam, were tested in four-point bending over a span of 3000 mm. We investigate the effect of the CFRC layer on the flexural performance and the electrical properties of the designed beams. The test results indicate that the CFRC strengthened RC beam exhibits improved electrical properties as well as better mechanical performance. Also, the location and the thickness of the CFRC layer affect the initial electrical resistance and other electrical properties of the beam. Relationships between electrical resistance, loading, deflection and cracks show that the increase in the electrical resistance can be used to monitor the extent of damage to the designed beam. Based on this discovery, a new health monitoring technique for RC structures is produced by means of electrical resistance measurements.

A Highly Sensitive Resistive Pressure Sensor Based on a Carbon Nanotube-Liquid Crystal-PDMS Composite.

PubMed

Pan, Jin; Liu, Shiyu; Yang, Yicheng; Lu, Jiangang

2018-06-08

Resistive pressure sensors generally employ microstructures such as pores and pyramids in the active layer or on the electrodes to reduce the Young’s modulus and improve the sensitivity. However, such pressure sensors always exhibit complex fabrication process and have difficulties in controlling the uniformity of microstructures. In this paper, we demonstrated a highly sensitive resistive pressure sensor based on a composite comprising of low-polarity liquid crystal (LPLC), multi-walled carbon nanotube (MWCNT), and polydimethylsiloxane (PDMS) elastomer. The LPLC in the PDMS forms a polymer-dispersed liquid crystal (PDLC) structure which can not only reduce the Young’s modulus but also contribute to the construction of conductive paths in the active layer. By optimizing the concentration of LC in PDMS elastomer, the resistive pressure sensor shows a high sensitivity of 5.35 kPa −1 , fast response (<150 ms), and great durability. Fabrication process is also facile and the uniformity of the microstructures can be readily controlled. The pressure sensor offers great potential for applications in emerging wearable devices and electronic skins.

Microstructure and wear resistance of one-step in-situ synthesized TiN/Al composite coatings on Ti6Al4V alloy by a laser nitriding process

NASA Astrophysics Data System (ADS)

Fu, Yao; Zhang, Xian-Cheng; Sui, Jian-Feng; Tu, Shan-Tung; Xuan, Fu-Zhen; Wang, Zheng-Dong

2015-04-01

The aim of this paper was to develop a one-step in situ method to synthesize the TiN reinforced Al metallic matrix composite coatings on Ti6Al4V alloy. In this method, the Al powder and nitrogen gas were simultaneously fed into feeding nozzle during a laser nitriding process. The microstructure, microhardness and sliding wear resistance of TiN/Al coatings synthesized at different laser powers in laser nitriding were investigated. Results showed that the crack- and pore-free coatings can be made through the proposed method. However, the morphologies and distribution of TiN dendrites and wear resistance of coatings were strongly dependent on laser power used in nitriding. With increasing the laser power, the amount and density of massive TiN dendritic structure in the coating decreased and the elongated and narrow dendrites increased, leading to the increment of wear resistance of coating. When the laser power is high, the convectional flow pattern of the melt pool can be seen near the bottom of pool.

Phosphoric acid addition effect on the microstructure and magnetic properties of iron-based soft magnetic composites

NASA Astrophysics Data System (ADS)

Hsiang, Hsing-I.; Fan, Liang-Fang; Hung, Jia-Jing

2018-02-01

The phosphoric acid addition effect on phosphate insulation coating microstructure was investigated in this study. The relationships between the phosphate insulation coating microstructure and temperature resistance, corrosion resistance and magnetic properties of iron-based soft magnetic composites (SMCs) were studied by using SEM, TEM/EDS and FTIR. It was observed that an iron phosphate/carbonyl iron core/shell structure is formed with carbonyl iron powder after phosphatizing treatment. The iron phosphate phase was identified as amorphous and its thickness increased from 30 nm to 60 nm as the phosphoric acid concentration was increased from 1 wt% to 2 wt%. When the phosphoric acid concentration was further increased to 5 wt%, the excess iron phosphate precipitates between the soft magnetic composite particles. The temperature and corrosion resistance and resistivity of the iron-based SMCs can be effectively improved using carbonyl iron powders after phosphatizing. The initial permeability of the iron-based SMCs decreased with increasing phosphoric acid concentration due to thicker insulation layer formation. However, the imaginary permeability below the domain wall displacement resonance frequency decreased with increasing phosphoric acid concentration. The DC-bias superposition characteristic can also be improved by increasing the phosphoric acid concentration. Iron-based SMCs with superior temperature and corrosion resistance, initial permeability, magnetic loss and DC-bias superposition characteristics can be obtained by controlling the phosphoric acid concentration during phosphatizing to adjust the iron phosphate precipitate thickness on the iron powder surface.

Differences in Cellulosic Supramolecular Structure of Compositionally Similar Rice Straw Affect Biomass Metabolism by Paddy Soil Microbiota

PubMed Central

Ogura, Tatsuki; Date, Yasuhiro; Kikuchi, Jun

2013-01-01

Because they are strong and stable, lignocellulosic supramolecular structures in plant cell walls are resistant to decomposition. However, they can be degraded and recycled by soil microbiota. Little is known about the biomass degradation profiles of complex microbiota based on differences in cellulosic supramolecular structures without compositional variations. Here, we characterized and evaluated the cellulosic supramolecular structures and composition of rice straw biomass processed under different milling conditions. We used a range of techniques including solid- and solution-state nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy followed by thermodynamic and microbial degradability characterization using thermogravimetric analysis, solution-state NMR, and denaturing gradient gel electrophoresis. These measured data were further analyzed using an “ECOMICS” web-based toolkit. From the results, we found that physical pretreatment of rice straw alters the lignocellulosic supramolecular structure by cleaving significant molecular lignocellulose bonds. The transformation from crystalline to amorphous cellulose shifted the thermal degradation profiles to lower temperatures. In addition, pretreated rice straw samples developed different microbiota profiles with different metabolic dynamics during the biomass degradation process. This is the first report to comprehensively characterize the structure, composition, and thermal degradation and microbiota profiles using the ECOMICS toolkit. By revealing differences between lignocellulosic supramolecular structures of biomass processed under different milling conditions, our analysis revealed how the characteristic compositions of microbiota profiles develop in addition to their metabolic profiles and dynamics during biomass degradation. PMID:23840554

An assessment of fracture resistance of three composite resin core build-up materials on three prefabricated non-metallic posts, cemented in endodontically treated teeth: an in vitro study

PubMed Central

Pal, Bhupinder; Pujari, Prashant

2015-01-01

Endodontically treated teeth with excessive loss of tooth structure would require to be restored with post and core to enhance the strength and durability of the tooth and to achieve retention for the restoration. The non-metallic posts have a superior aesthetic quality. Various core build-up materials can be used to build-up cores on the posts placed in endodontically treated teeth. These materials would show variation in their bonding with the non-metallic posts thus affecting the strength and resistance to fracture of the remaining tooth structure. Aims. The aim of the study was to assess the fracture resistance of three composite resin core build-up materials on three prefabricated non-metallic posts, cemented in extracted endodontically treated teeth. Material and Methods. Forty-five freshly extracted maxillary central incisors of approximately of the same size and shape were selected for the study. They were divided randomly into 3 groups of 15 each, depending on the types of non-metallic posts used. Each group was further divided into 3 groups (A, B and C) of 5 samples each depending on three core build-up material used. Student’s unpaired ‘t’ test was also used to analyse and compare each group with the other groups individually, and decide whether their comparisons were statistically significant. Results. Luxacore showed the highest fracture resistance among the three core build-up materials with all the three posts systems. Ti-core had intermediate values of fracture resistance and Lumiglass had the least values of fracture resistance. PMID:25755926

Tailoring surface properties of ArF resists thin films with functionally graded materials (FGM)

NASA Astrophysics Data System (ADS)

Takemoto, Ichiki; Ando, Nobuo; Edamatsu, Kunishige; Fuji, Yusuke; Kuwana, Koji; Hashimoto, Kazuhiko; Funase, Junji; Yokoyama, Hiroyuki

2007-03-01

Our recent research effort has been focused on new top coating-free 193nm immersion resists with regard to leaching of the resist components and lithographic performance. We have examined methacrylate-based resins that control the surface properties of ArF resists thin films by surface segregation behavior. For a better understanding of the surface properties of thin films, we prepared the six resins (Resin 1-6) that have three types fluorine containing monomers, a new monomer (Monomer A), Monomer B and Monomer C, respectively. We blended the base polymer (Resin 0) with Resin (1-6), respectively. We evaluated contact angles, surface properties and lithographic performances of the polymer blend resists. The static and receding contact angles of the resist that contains Resin (1-6) are greater than that of the base polymer (Resin 0) resist. The chemical composition of the surface of blend polymers was investigated with X-ray photoelectron spectroscopy (XPS). It was shown that there was significant segregation of the fluorine containing resins to the surface of the blend films. We analyzed Quantitative Structure-Property Relationships (QSPR) between the surface properties and the chemical composition of the surface of polymer blend resists. The addition of 10 wt% of the polymer (Resin 1-6) to the base polymer (Resin 0) did not influence the lithographic performance. Consequently, the surface properties of resist thin films can be tailored by the appropriate choice of fluorine containing polymer blends.

Vegetative resistance to flow in South Florida; summary of vegetation sampling at sites NESRS3 and P33, Shark River slough, April 1996

USGS Publications Warehouse

Carter, Virginia; Ruhl, H.; Rybicki, N.B.; Reel, J.T.; Gammon, P.T.

1999-01-01

The U.S. Geological Survey is one of many agencies participating in the effort to restore the south Florida Everglades. We are sampling and characterizing the vegetation at selected sites in the Everglades as part of a study to quantify vegetative flow resistance. The objectives of the vegetative sampling are (1) to provide detailed information on species composition, vegetative characteristics, vegetative structure, and biomass for quantification of vegetative resistance to flow, and (2) to use this information to classify the vegetation and to improve existing vegetation maps for use with numerical models of surface-water flow. Vegetative sampling was conducted in the Shark River Slough in April, 1996. The data collected and presented here include live, dead, and periphyton biomass, vegetation characteristics and structure, and leaf area index.

Research on Heat Resistant Transparent Interlayers Based on the Ethylene Terpolymer.

DTIC Science & Technology

1976-08-01

the s ; - c i v i n g machine as it is about to pass under th~ kn if’e .The block was skived into 10, 30 , and 50 rail sheets. Laminat es of glass...reviewed and is approved for publicati on. Project Monito FOR THE COMMANDER T .J ~~ EI~~~~~~JR~,C~~~~~ Composite and Fibrous Materials Branch...iated under Project No. 29lZ~, “Non—metallic and Composite Mater ia ls , ” and Task No. 03, “Structural Plastics and Composites ” . The work was

SiC-Based Composite Materials Obtained by Siliconizing Carbon Matrices

NASA Astrophysics Data System (ADS)

Shikunov, S. L.; Kurlov, V. N.

2017-12-01

We have developed a method for fabrication of parts of complicated configuration from composite materials based on SiC ceramics, which employs the interaction of silicon melt with the carbon matrix having a certain composition and porosity. For elevating the operating temperatures of ceramic components, we have developed a method for depositing protective silicon-carbide coatings that is based on the interaction of the silicon melt and vapor with carbon obtained during thermal splitting of hydrocarbon molecules. The new structural ceramics are characterized by higher operating temperatures; chemical stability; mechanical strength; thermal shock, wear and radiation resistance; and parameters stability.

The Design and Synthesis of Epoxy Matrix Composites Curable by Electron Beam Induced Cationic Polymerization

NASA Technical Reports Server (NTRS)

Crivello, James V.

2000-01-01

Several new series of novel, high reactivity epoxy resins are described which are designed specifically for the fabrication of high performance carbon fiber reinforced composites for commercial aircraft structural applications using cationic UV and e-beam curing. The objective of this investigation is to provide resin matrices which rapidly and efficiently cure under low e-beam doses which are suitable to high speed automated composite fabrication techniques such as automated tape and tow placement. It was further the objective of this work to provide resins with superior thermal, oxidative and atomic oxygen resistance.

Open-Lattice Composite Design Strengthens Structures

NASA Technical Reports Server (NTRS)

2007-01-01

Advanced composite materials and designs could eventually be applied as the framework for spacecraft or extraterrestrial constructions for long-term space habitation. One such structure in which NASA has made an investment is the IsoTruss grid structure, an extension of a two-dimensional "isogrid" concept originally developed at McDonnell Douglas Astronautics Company, under contract to NASA's Marshall Space Flight Center in the early 1970s. IsoTruss is a lightweight and efficient alternative to monocoque composite structures, and can be produced in a manner that involves fairly simple techniques. The technology was developed with support from NASA to explore space applications, and is garnering global attention because it is extremely lightweight; as much as 12 times stronger than steel; inexpensive to manufacture, transport, and install; low-maintenance; and is fully recyclable. IsoTruss is expected to see application as utility poles and meteorological towers, for the aforementioned reasons and because its design offers superior wind resistance and is less susceptible to breaking and woodpeckers. Other applications, such as reinforcement for concrete structures, stand-alone towers, sign supports, prostheses, irrigation equipment, and sporting goods are being explored

Corrosion resistance and in-vitro bioactivity of BaO containing Na2O-CaO-P2O5 phosphate glass-ceramic coating prepared on 316 L, duplex stainless steel 2205 and Ti6Al4V

NASA Astrophysics Data System (ADS)

Edathazhe, Akhila B.; Shashikala, H. D.

2018-03-01

The phosphate glass with composition 11Na2O-15BaO-29CaO-45P2O5 was coated on biomedical implant materials such as stainless steel 316 L, duplex stainless steel (DSS) 2205 and Ti6Al4V alloy by thermal enamelling method. The structural properties and composition of glass coated substrates were studied by x-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive x-ray spectroscopy (EDS) analysis. The coatings were partially crystalline in nature with porous structure and pore size varied from micro to nanometer range. The polarization curve was obtained for uncoated and coated substrates from electrochemical corrosion test which was conducted at 37 °C in Hank’s balanced salt solution (HBSS). The corrosion resistance of 316 L substrate increased after coating, whereas it decreased in case of DSS 2205 and Ti6Al4V. The XRD and SEM/EDS studies indicated the bioactive hydroxyapatite (HAp) layer formation on all the coated surfaces after electrochemical corrosion test, which improved the corrosion resistance. The observed electrochemical corrosion behavior can be explained based on protective HAp layer formation, composition and diffusion of ions on glass coated surfaces. The in-vitro bioactivity test was carried out at 37 °C in HBS solution for 14 days under static conditions for uncoated and coated substrates. pH and ion release rate measurements from the coated samples were conducted to substantiate the electrochemical corrosion test. The lower ion release rates of Na+ and Ca2+ from coated 316 L supported its higher electrochemical corrosion resistance among coated samples. Among the uncoated substrates, DSS showed higher electrochemical corrosion resistance. Amorphous calcium-phosphate (ACP) layer formation on all the coated substrates after in-vitro bioactivity test was confirmed by XRD, SEM/EDS and ion release measurements. The present work is a comparative study of corrosion resistance and bioactivity of glass coated and uncoated biomedical implants such as 316 L, DSS and Ti6Al4V.

Improving the tribological and corrosive properties of MoS2-based coatings by dual-doping and multilayer construction

NASA Astrophysics Data System (ADS)

Shang, Kedong; Zheng, Shaoxian; Ren, Siming; Pu, Jibin; He, Dongqing; Liu, Shuan

2018-04-01

The pure MoS2 coating always performs high friction coefficient and short service life when used in high humidity or after long-time storage in humid atmospheric environment. In this study, the MoS2/Pb-Ti composite and MoS2/Pb-Ti multilayer coatings are deposited to improve the corrosion resistance in 3.5 wt% NaCl solution and tribological performance in high humidity condition. The electrochemical impedance spectra and salt spray test shown that the MoS2/Pb-Ti composite and multilayer coatings can inhibit the permeation of oxygen and other corrosive elements, thus resulting a high corrosion resistance. Furthermore, compared with pure MoS2 coating, the tribological performance of the MoS2/Pb-Ti composite and multilayer coatings is also improved significantly owing to the high mechanical properties and compact structure. Moreover, the heterogenous interfaces in MoS2/Pb-Ti multilayer coating play an important role to improve the corrosion resistance and tribological performance of coatings. Overall, the dual-doping and multilayer construction are promising approaches to design the MoS2 coatings as the environmentally adaptive lubricants.

High-pressure studies on nanocrystalline borderline Co1-xFexS2 (x = 0.4 and 0.5) using Mössbauer spectroscopic and electrical resistivity techniques up to 8 GPa

NASA Astrophysics Data System (ADS)

Chandra, Usha; Sharma, Pooja; Parthasarathy, G.

2016-12-01

Like bulk, Co1-xFexS2 nanoparticles also display an anomaly at x = 0.5. The borderline contiguous Co1-xFexS2 (x = 0.4 and 0.5) nanoparticles were synthesized with colloidal method and characterized for pyrite structure using various techniques, viz., X-ray diffraction, energy dispersive X-ray analysis (EDAX), S K-edge X-ray absorption near edge spectra, transmission electron microscopy (TEM) and Fourier transformed infra-red spectroscopy. The report presents the effect of high pressure on the borderline compositions using the Mössbauer spectroscopic and electrical resistivity techniques. Magnetic measurements on the system showed drastic lowering of Tc due to nanosize of the particles. With increased pressure, quadrupole splitting showed an expected trend of increase to attain a peak representing a second-order phase transition between 4 and 5 GPa for both the compositions. The pressure coefficient of electrical resistivity varied from -0.02 GPa to -0.06 GPa across transition pressure indicating a sluggish nature of transition. This is the first report of pressure effect on nanosized borderline compositions.

Load Distribution Factors for Composite Multicell Box Girder Bridges

NASA Astrophysics Data System (ADS)

Tiwari, Sanjay; Bhargava, Pradeep

2017-12-01

Cellular steel section composite with a concrete deck is one of the most suitable superstructures in resisting torsional and warping effects induced by highway loading. This type of structure has inherently created new design problems for engineers in estimating its load distribution when subjected to moving vehicles. Indian Codes of Practice does not provide any specific guidelines for the design of straight composite concrete deck-steel multi-cell bridges. To meet the practical requirements arising during the design process, a simple design method is needed for straight composite multi-cell bridges in the form of load distribution factors for moment and shear. This work presents load distribution characteristics of straight composite multi-cell box girder bridges under IRC trains of loads.

Evaluation of Mechanical Properties of MWCNT / Nanoclay Reinforced Aluminium alloy Metal Matrix Composite

NASA Astrophysics Data System (ADS)

Ratna Kumar, P. S. Samuel; Robinson Smart, D. S.; Alexis, S. John

2018-04-01

Aluminium alloy 5083 (AA5083) is a widely used material in aerospace, marine, defence and structural applications were mechanical and corrosion resistance property plays a vital role. For the present work, MWCNT / Nanoclay (montmorillonite (MMT) K10) mixed with AA5083 for different composition in weight percentage to enhance the mechanical property. Semi-solid state casting method (Compo-casting) was used to fabricate the composite materials. By using Field-emission scanning electron microscope (FESEM) the uniform dispersion of the reinforcement and microstructure were studied. Finally, the addition of Nanoclay shows decrease in tensile strength compared to the AA5083 / MWCNT composites and hardness value of the composites (AA5083 / MWCNT and AA5083 / Nanoclay) was found to increase significantly.

Improving Thermomechanical Properties of SiC/SiC Composites

NASA Technical Reports Server (NTRS)

DiCarlo, James A.; Bhatt, Ramakrishna T.

2006-01-01

Today, a major thrust toward improving the thermomechanical properties of engine components lies in the development of fiber-reinforced silicon carbide matrix composite materials, including SiC-fiber/SiC-matrix composites. These materials are lighter in weight and capable of withstanding higher temperatures, relative to state-of-the-art metallic alloys and oxide-matrix composites for which maximum use temperatures are in the vicinity of 1,100 C. In addition, the toughness or damage tolerance of the SiC-matrix composites is significantly greater than that of unreinforced silicon-based monolithic ceramics. For successful application in advanced engine systems, the SiC-matrix composites should be able to withstand component service stresses and temperatures for the desired component lifetimes. Inasmuch as the high-temperature structural lives of ceramic materials are typically limited by creep-induced growth of flaws, a key property required of such composite materials is high resistance to creep under conditions of use. Also, the thermal conductivity of the materials should be as high as possible so as to minimize component thermal gradients and thermal stresses. A state-of-the-art SiC-matrix composite is typically fabricated in a three-step process: (1) fabrication of a component-shaped architectural preform reinforced by thermally stable high-performance fibers, (2) chemical-vapor infiltration (CVI) of a fiber-coating material such as boron nitride (BN) into the preform, and (3) infiltration of an SiC-based matrix into the remaining porosity in the preform. Generally, the matrices of the highest-performing composites are fabricated by initial use of a CVI SiC matrix component that is typically more thermally stable and denser than matrix components formed by processes other than CVI. As such, the initial SiC matrix component made by CVI provides better environmental protection to the coated fibers embedded within it. Also, the denser CVI SiC imparts to the composite better resistance to propagation of cracks, enhanced thermal conductivity, and higher creep resistance.

Synthesis, Structure and Antimicrobial Property of Green Composites from Cellulose, Wool, Hair and Chicken Feather

PubMed Central

Tran, Chieu D.; Prosenc, Franja; Franko, Mladen; Benzi, Gerald

2016-01-01

Novel composites between cellulose (CEL) and keratin (KER) from three different sources (wool, hair and chicken feather) were successfully synthesized in a simple one-step process in which butylmethylimidazolium chloride (BMIm+Cl−), an ionic liquid, was used as the sole solvent. The method is green and recyclable because [BMIm+Cl−] used was recovered for reuse. Spectroscopy (FTIR, XRD) and imaging (SEM) results confirm that CEL and KER remain chemically intact and homogeneously distributed in the composites. KER retains some of its secondary structure in the composites. Interestingly, the minor differences in the structure of KER in wool, hair and feather produced pronounced differences in the conformation of their corresponding composites with wool has the highest α-helix content and feather has the lowest content. These results correlate well with mechanical and antimicrobial properties of the composites. Specifically, adding CEL into KER substantially improves mechanical strength of [CEL+KER] composites made from all three different sources, wool, hair and chicken feathers (i.e., [CEL+wool], [CEL+hair] and [CEL+feather]. Since mechanical strength is due to CEL, and CEL has only random structure, [CEL+feather] has, expectedly, the strongest mechanical property because feather has the lowest content of α-helix. Conversely, [CEL+wool] composite has the weakest mechanical strength because wool has the highest α-helix content. All three composites exhibit antibacterial activity against methicillin resistant S. aureus (MRSA). The antibacterial property is due not to CEL but to the protein and strongly depends on the type of the keratin, namely, the bactericidal effect is strongest for feather and weakest for wool. These results together with our previous finding that [CEL+KER] composites can control release of drug such as ciprofloxacin clearly indicate that these composites can potentially be used as wound dressing PMID:27474680

Piezoresistive strain sensing of carbon nanotubes-based composite skin for aeronautical morphing structures

NASA Astrophysics Data System (ADS)

Viscardi, Massimo; Arena, Maurizio; Barra, Giuseppina; Vertuccio, Luigi; Ciminello, Monica; Guadagno, Liberata

2018-03-01

Nowadays, smart composites based on different nano-scale carbon fillers, such as carbon nanotubes (CNTs), are increasingly being thought of as a more possible alternative solution to conventional smart materials, mainly for their improved electrical properties. Great attention is being given by the research community in designing highly sensitive strain sensors for more and more ambitious challenges: in such context, interest fields related to carbon nanotubes have seen extraordinary development in recent years. The authors aim to provide the most contemporary overview possible of carbon nanotube-based strain sensors for aeronautical application. A smart structure as a morphing wing needs an embedded sensing system in order to measure the actual deformation state as well as to "monitor" the structural conditions. Looking at more innovative health monitoring tools for the next generation of composite structures, a resin strain sensor has been realized. The epoxy resin was first analysed by means of a micro-tension test, estimating the electrical resistance variations as function of the load, in order to demonstrate the feasibility of the sensor. The epoxy dogbone specimen has been equipped with a standard strain gauge to quantify its strain sensitivity. The voltamperometric tests highlight a good linearity of the electrical resistance value as the load increases at least in the region of elastic deformation of the material. Such intrinsic piezoresistive performance is essentially attributable to the re-arrangement of conductive percolating network formed by MWCNT, induced by the deformation of the material due to the applied loads. The specimen has been prepared within this investigation, to demonstrate its performance for a future composite laminate typical of aerospace structures. The future carbon-fiber sensor can replace conventional metal foil strain gauges in aerospace applications. Furthermore, dynamic tests will be carried out to detect any non-reversible changes to the sensing response.

Effect of polyamide 6 on the morphology and electrical conductivity of carbon black-filled polypropylene composites

NASA Astrophysics Data System (ADS)

Zhang, Xuewei; Liu, Jiang; Wang, Yi; Wu, Wei

2017-12-01

Carbon black (CB)-filled polypropylene (PP) with surface resistivity between 106 and 109 Ω sq-1 is the ideal antistatic plastic material in the electronics and electric industry. However, a large amount of CB may have an adverse effect on the mechanical properties and processing performance of the material, thus an improved ternary system is developed. Blends of CB-filled PP and polyamide 6 (PA6) have been prepared by melt blending in order to obtain electrically conductive polymer composites with a low electrical percolation threshold based on the concept of double percolation. The morphological developments of these composites were studied by scanning electron microscopy. The results showed that CB particles were selectively dispersed in PA6 phases due to the good interaction and interfacial adhesion between CB and PA6. At the same CB loadings, the surface resistivity of PP/PA6/CB composite was smaller than that of PP/CB composite system, which indicated the better conductivity in the former composite. The increasing amount of PA6 in the composites changed the morphology from a typical sea-island morphology to a co-continuous morphology. What is more, with 8 wt% of CB and PP/PA6 phase ratio of 70/30 in which the PP and PA6 phases formed a co-continuous structure, the electrical conductivity of the composite peaked at 2.01 × 105 Ω sq-1.

3-dimensional free standing micro-structures by proton beam writing of Su 8-silver nanoParticle polymeric composite

NASA Astrophysics Data System (ADS)

Igbenehi, H.; Jiguet, S.

2012-09-01

Proton beam lithography a maskless direct-write lithographic technique (well suited for producing 3-Dimensional microstructures in a range of resist and semiconductor materials) is demonstrated as an effective tool in the creation of electrically conductive freestanding micro-structures in an Su 8 + Nano Silver polymer composite. The structures produced show non-ohmic conductivity and fit the percolation theory conduction model of tunneling of separated nanoparticles. Measurements show threshold switching and a change in conductivity of at least 4 orders of magnitude. The predictable range of protons in materials at a given energy is exploited in the creation of high aspect ratio, free standing micro-structures, made from a commercially available SU8 Silver nano-composite (GMC3060 form Gersteltec Inc. a negative tone photo-epoxy with added metallic nano-particles(Silver)) to create films with enhanced electrical properties when exposed and cured. Nano-composite films are directly written on with a finely focused MeV accelerated Proton particle beam. The energy loss of the incident proton beams in the target polymer nano- composite film is concentrated at the end of its range, where damage occurs; changing the chemistry of the nano-composite film via an acid initiated polymerization - creating conduction paths. Changing the energy of the incident beams provide exposed regions with different penetration and damage depth - exploited in the demonstrated cantilever microstructure.

Investigation of Antibacterial and Fouling Resistance of Silver and Multi-Walled Carbon Nanotubes Doped Poly(Vinylidene Fluoride-co-Hexafluoropropylene) Composite Membrane

PubMed Central

Macevele, Lutendo E.; Moganedi, Kgabo L. M.; Magadzu, Takalani

2017-01-01

Composite membranes were successfully prepared using a phase-inversion method. The X-ray powder diffraction (XRD) and energy dispersive X-ray (EDX) profiles has confirmed formation of 4.8 wt % Ag/poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), 3 wt % Ag-MWCNTs/PVDF-HFP (EDX surface composition of Ag nanoparticles) and 1.5 wt % MWCNTs/PVDF-HFP composite membranes. The MWCNTs crystallites are mainly encapsulated by a layer of PVDF-HFP, as evidenced by disappearance of graphitic peak. The scanning electron microscopy (SEM) images have depicted the formation of microporous structure, with few MWCNTs on the surface and strongly interacting with PVDF-HFP as demonstrated by thermogravimetric analysis (TGA), XRD and Fourier transform infrared (FTIR) data. The data indicated an increase in porosity, swellability and water content of the PVDF-HFP membrane with the addition of MWCNTs and/or Ag nanoparticles, showing an improved hydrophilicity. The 1.5 wt % MWCNTs/PVDF-HFP composite membrane showed good desalination and fouling resistance rates, which correlates with a low water contact angle. The combined effects of Ag nanoparticles and MWCNTs do not promote fouling resistance of PVDF-HFP membranes, as shown during NaCl microfiltration (this is linked with high water contact angle as compared to that of MWCNTs/PVDF-HFP composite). Both 1.5 wt % MWCNTs/PVDF-HFP and 3 wt % Ag-MWCNTs/PVDF-HFP composite membranes prevented the bacteria passing through the membrane (100% bacterial load reduction). The surface of 3 wt % Ag-MWCNTs/PVDF-HFP showed good bactericidal and non-leaching properties of the dopant materials (MWCNTs and Ag), as evidenced by bacterial growth on the edges of the membranes. PMID:28703740

Parametric Study of Fire Performance of Concrete Filled Hollow Steel Section Columns with Circular and Square Cross-Section

NASA Astrophysics Data System (ADS)

Nurfaidhi Rizalman, Ahmad; Tahir, Ng Seong Yap Mahmood Md; Mohammad, Shahrin

2018-03-01

Concrete filled hollow steel section column have been widely accepted by structural engineers and designers for high rise construction due to the benefits of combining steel and concrete. The advantages of concrete filled hollow steel section column include higher strength, ductility, energy absorption capacity, and good structural fire resistance. In this paper, comparison on the fire performance between circular and square concrete filled hollow steel section column is established. A three-dimensional finite element package, ABAQUS, was used to develop the numerical model to study the temperature development, critical temperature, and fire resistance time of the selected composite columns. Based on the analysis and comparison of typical parameters, the effect of equal cross-sectional size for both steel and concrete, concrete types, and thickness of external protection on temperature distribution and structural fire behaviour of the columns are discussed. The result showed that concrete filled hollow steel section column with circular cross-section generally has higher fire resistance than the square section.

Synthesis and thermal conductivity of type II silicon clathrates

NASA Astrophysics Data System (ADS)

Beekman, M.; Nolas, G. S.

2006-08-01

We have synthesized and characterized polycrystalline Na 1Si 136 and Na 8Si 136, compounds possessing the type II clathrate hydrate crystal structure. Resistivity measurements from 10 to 300 K indicate very large resistivities in this temperature range, with activated temperature dependences indicative of relatively large band gap semiconductors. The thermal conductivity is very low; two orders-of-magnitude lower than that of diamond-structure silicon at room temperature. The thermal conductivity of Na 8Si 136 displays a temperature dependence that is atypical of crystalline solids and more indicative of amorphous materials. This work is part of a continuing effort to explore the many different compositions and structure types of clathrates, a class of materials that continues to be of interest for scientific and technological applications.

A nanometallic nickel-coated, glass-fibre-based structural health monitoring system for polymer composites

NASA Astrophysics Data System (ADS)

Balaji, R.; Sasikumar, M.

2017-09-01

Glass-fibre-reinforced polymer matrix composites are widely used in various industries because of their unique high strength to weight ratio. Unlike metals, strain-induced and damage states of composites are complicated to predict under real-time loading due to their anisotropic nature. With that focus, a piezoresistive nanomaterial-based structural health monitoring system for laminated polymer composites is proposed to measure the strain induced in the composite under real-time loading. Nanometallic nickel-coated glass fibres are embedded into the polymer composites to monitor the strain and damage induced in them. The nanometallic nickel is coated over the glass fibre by a dip coating technique using epoxy as the binding agent. A microcontroller-based electrical resistance measurement system is used to measure the piezoresistive variation in the coated glass fibre under real-time loading. Using the piezoresistance variation of the embedded nanometallic nickel-coated glass fibre, the real-time strain and damage induced in the composite can be correlated. The piezoresistive response of the coated glass fibre is descibed in two phases, the deformation phase and the failure phase, which clearly show the various states of strain and damage induced in the composites.

Effect of fabrication processes on mechanical properties of glass fiber reinforced polymer composites for 49 meter (160 foot) recreational yachts

NASA Astrophysics Data System (ADS)

Kim, Dave (dea-wook); Hennigan, Daniel John; Beavers, Kevin Daniel

2010-03-01

Polymer composite materialsoffer high strength and stiffness to weight ratio, corrosion resistance, and total life cost reductions that appeal to the marine industry. The advantages of composite construction have led to their incorporation in U.S. yacht hull structures over 46 meters (150 feet) in length. In order to construct even larger hull structures, higher quality composites with a lower cost production techniques need to be developed. In this study, the effect of composite hull fabrication processes on mechanical properties of glass fiber reinforced plastic(GFRP) composites is presented. Fabrication techniques used in this study are hand lay-up (HL), vacuum infusion (VI), and hybrid (HL+VI) processes. Mechanical property testing includes: tensile, compressive, and ignition loss sample analysis. Results demonstrate that the vacuum pressure implemented during composite fabrication has an effect on mechanical properties. The VI processed GFRP yields improved mechanical properties in tension/compression strengths and tensile modulus. The hybrid GFRP composites, however, failed in a sequential manor, due to dissimilar failure modes in the HL and VI processed sides. Fractography analysis was conducted to validate the mechanical property testing results

Electrical conduction in polymer dielectrics

NASA Technical Reports Server (NTRS)

Cotts, D. B.

1985-01-01

The use of polymer dielectrics with moderate resistivities could reduce or eliminate problems associated with spacecraft charging. The processes responsible for conduction and the properties of electroactive polymers are reviewed, and correlations drawn between molecular structure and electrical conductivity. These structure-property relationships led to the development of several new electroactive polymer compositions and the identification of several systems that have the requisite thermal, mechanical, environmental and electrical properties for use in spacecraft.

Development of Improved Environmental Resistant Organic-Reinforced Materials Systems

DTIC Science & Technology

1975-11-01

Advanced composites , graphite and boron reinforced laminates, moisture resistance, environmental resistance, organic matrix composites . 20. ABSTRACT...in November 1975 for publication. Efforts at TOD were conducted within the Advanced Composites Engineering Departmfntrunde; L technical...weight makes^organic matrix advanced composites hardware extremely attractive for today s modern Air Force weapons systems. Accordingly, such

Structure-property and composition-property relationships for poly(ethylene terephthalate) surfaces modified by helium plasma-based ion implantation

NASA Astrophysics Data System (ADS)

Tóth, A.; Veres, M.; Kereszturi, K.; Mohai, M.; Bertóti, I.; Szépvölgyi, J.

2011-10-01

The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and ID/ IG ratio and between chroma and ID/ IG ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp 2 carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the ID/ IG ratio and inverse correlations between surface energy and ID/ IG ratio and between dispersive component of surface energy and ID/ IG ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp 2 carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the π → π* shake-up satellite of the C 1s peak.

Viscoelasticity of biofilms and their recalcitrance to mechanical and chemical challenges

PubMed Central

Peterson, Brandon W.; He, Yan; Ren, Yijin; Zerdoum, Aidan; Libera, Matthew R.; Sharma, Prashant K.; van Winkelhoff, Arie-Jan; Neut, Danielle; Stoodley, Paul; van der Mei, Henny C.; Busscher, Henk J.

2015-01-01

We summarize different studies describing mechanisms through which bacteria in a biofilm mode of growth resist mechanical and chemical challenges. Acknowledging previous microscopic work describing voids and channels in biofilms that govern a biofilms response to such challenges, we advocate a more quantitative approach that builds on the relation between structure and composition of materials with their viscoelastic properties. Biofilms possess features of both viscoelastic solids and liquids, like skin or blood, and stress relaxation of biofilms has been found to be a corollary of their structure and composition, including the EPS matrix and bacterial interactions. Review of the literature on viscoelastic properties of biofilms in ancient and modern environments as well as of infectious biofilms reveals that the viscoelastic properties of a biofilm relate with antimicrobial penetration in a biofilm. In addition, also the removal of biofilm from surfaces appears governed by the viscoelasticity of a biofilm. Herewith, it is established that the viscoelasticity of biofilms, as a corollary of structure and composition, performs a role in their protection against mechanical and chemical challenges. Pathways are discussed to make biofilms more susceptible to antimicrobials by intervening with their viscoelasticity, as a quantifiable expression of their structure and composition. PMID:25725015

I-5/Gilman advanced technology bridge project

NASA Astrophysics Data System (ADS)

Lanza di Scalea, Francesco; Karbhari, Vistasp M.; Seible, Frieder

2000-04-01

The UCSD led I-5/Gilman Advanced Technology Bridge Project will design and construct a fully functional traffic bridge of advanced composite materials across Interstate 5 in La Jolla, California. Its objective is to demonstrate the use of advanced composite technologies developed by the aerospace industry in commercial applications to increase the life expectancy of new structures and for the rehabilitation of aging infrastructure components. The structure will be a 450 ft long, 60 ft wide cable-stayed bridge supported by a 150 ft A-frame pylon with two vehicular lanes, two bicycle lanes, pedestrian walkways and utility tunnels. The longitudinal girders and pylon will be carbon fiber shells filled with concrete. The transverse deck system will consist of hollow glass/carbon hybrid tubes and a polypropylene fiber reinforced concrete deck with an arch action. Selected cables will be composite. The bridge's structural behavior will be monitored to determine how advanced composite materials perform in civil infrastructure applications. The bridge will be instrumented to obtain performance and structural health data in real time and, where possible, in a remote fashion. The sensors applied to the bridge will include electrical resistance strain gages, fiberoptic Bragg gratings and accelerometers.

Improved irradiation tolerance of reactive gas pulse sputtered TiN coatings with a hybrid architecture of multilayered and compositionally graded structures

NASA Astrophysics Data System (ADS)

Liang, Wei; Yang, Jijun; Zhang, Feifei; Lu, Chenyang; Wang, Lumin; Liao, Jiali; Yang, Yuanyou; Liu, Ning

2018-04-01

This study investigates the improved irradiation tolerance of reactive gas pulse (RGP) sputtered TiN coatings which has hybrid architecture of multilayered and compositionally graded structures. The multilayered RGP-TiN coating is composed of hexagonal close-packed Ti phase and face-centred cubic TiN phase sublayers, where the former sublayer has a compositionally graded structure and the latter one maintains constant stoichiometric atomic ratio of Ti:N. After 100 keV He ion irradiation, the RGP-TiN coating exhibits improved irradiation resistance compared with its single layered (SL) counterpart. The size and density of He bubbles are smaller in the RGP-TiN coating than in the SL-TiN coating. The irradiation-induced surface blistering of the coatings shows a similar tendency. Meanwhile, the irradiation hardening and adhesion strength of the RGP-TiN coatings were not greatly affected by He irradiation. Moreover, the irradiation damage tolerance of the coatings can be well tuned by changing the undulation period number of N2 gas flow rate. Detailed analysis suggested that this improved irradiation tolerance could be related to the combined contribution of the multilayered and compositionally graded structures.

Tribological properties of epoxy composite coatings reinforced with functionalized C-BN and H-BN nanofillers

NASA Astrophysics Data System (ADS)

Yu, Jingjing; Zhao, Wenjie; Wu, Yinghao; Wang, Deliang; Feng, Ruotao

2018-03-01

A series of epoxy resin (EP) composite coatings reinforced with functionalized cubic boron nitride (FC-BN) and functionalized hexagonal boron nitride (FH-BN) were fabricated successfully on 316L stainless steel by hand lay-up technique. The structure properties were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The morphologies were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, UMT-3 tribometer and surface profiler were used to investigate tribological behaviors of as-prepared composite coatings under dry friction and seawater conditions respectively. The results demonstrated that the presence of FC-BN or FH-BN fillers could greatly decrease the friction coefficient (COF) and wear rate of epoxy, in addition, composite coatings possess better tribological properties under seawater condition which was attributed to the lubricating effect of seawater. Moreover, FC-BN endows the composite coatings the highest wear resistance, and FH-BN /EP composite coatings exhibited the best friction reduction performance which is attributed to the self-lubricating performance of lamella structure for FH-BN sheet.

Sintering Process and Mechanical Property of MWCNTs/HDPE Bulk Composite

PubMed Central

Tze-Chi, Hsu; Jie-Ren, Zheng

2009-01-01

Studies have proved that increasing polymer matrices by carbon nanotubes to form structural reinforcement and electrical conductivity have significantly improved mechanical and electrical properties at very low carbon nanotubes loading. In other words, increasing polymer matrices by carbon nanotubes to form structural reinforcement can reduce friction coefficient and enhance anti-wear property. However, producing traditional MWCNTs in polymeric materix is an extremely complicated process. Using melt-mixing process or in situ polymerization leads to better dispersion effect on composite materials. In this study, therefore, to simplify MWCNTs /HDPE composite process and increase dispersion, powder was used directly to replace pellet to mix and sinter with MWCNTs. The composite bulks with 0, 0.5, 1, 2 and 4% nanotube content by weight was analyzed under SEM to observe nanotubes dispersion. At this rate, a MWCNTs/HDPE composite bulk with uniformly dispersed MWCNTs was achieved, and through the wear bench (Pin-on-Disk), the wear experiment has accomplished. Accordingly, the result suggests the sintered MWCNTs/HDPE composites amplify the hardness and wear-resist property. PMID:19730688

Colloidal-based additive manufacturing of bio-inspired composites

NASA Astrophysics Data System (ADS)

Studart, Andre R.

Composite materials in nature exhibit heterogeneous architectures that are tuned to fulfill the functional demands of the surrounding environment. Examples range from the cellulose-based organic structure of plants to highly mineralized collagen-based skeletal parts like bone and teeth. Because they are often utilized to combine opposing properties such as strength and low-density or stiffness and wear resistance, the heterogeneous architecture of natural materials can potentially address several of the technical limitations of artificial homogeneous composites. However, current man-made manufacturing technologies do not allow for the level of composition and fiber orientation control found in natural heterogeneous systems. In this talk, I will present two additive manufacturing technologies recently developed in our group to build composites with exquisite architectures only rivaled by structures made by living organisms in nature. Since the proposed techniques utilize colloidal suspensions as feedstock, understanding the physics underlying the stability, assembly and rheology of the printing inks is key to predict and control the architecture of manufactured parts. Our results will show that additive manufacturing routes offer a new exciting pathway for the fabrication of biologically-inspired composite materials with unprecedented architectures and functionalities.

Manufacturing Technology of Composite Materials—Principles of Modification of Polymer Composite Materials Technology Based on Polytetrafluoroethylene

PubMed Central

Panda, Anton; Dyadyura, Kostiantyn; Valíček, Jan; Harničárová, Marta; Zajac, Jozef; Modrák, Vladimír; Pandová, Iveta; Vrábel, Peter; Nováková-Marcinčínová, Ema; Pavelek, Zdeněk

2017-01-01

The results of the investigations into the technological formation of new wear-resistant polymer composites based on polytetrafluoroethylene (PTFE) filled with disperse synthetic and natural compounds are presented. The efficiency of using PTFE composites reinforced with carbon fibers depends on many factors, which influence the significant improvement of physicomechanical characteristics. The results of this research allow stating that interfacial and surface phenomena of the polymer–solid interface and composition play a decisive role in PTFE composites properties. Fillers hinder the relative movement of the PTFE molecules past one another and, in this way, reduce creep or deformation of the parts, reducing the wear rate of parts used in dynamic applications as well as the coefficient of thermal expansion. The necessary structural parameters of such polymer composites are provided by regimes of process equipment. PMID:28772733

Manufacturing Technology of Composite Materials-Principles of Modification of Polymer Composite Materials Technology Based on Polytetrafluoroethylene.

PubMed

Panda, Anton; Dyadyura, Kostiantyn; Valíček, Jan; Harničárová, Marta; Zajac, Jozef; Modrák, Vladimír; Pandová, Iveta; Vrábel, Peter; Nováková-Marcinčínová, Ema; Pavelek, Zdeněk

2017-03-31

The results of the investigations into the technological formation of new wear-resistant polymer composites based on polytetrafluoroethylene (PTFE) filled with disperse synthetic and natural compounds are presented. The efficiency of using PTFE composites reinforced with carbon fibers depends on many factors, which influence the significant improvement of physicomechanical characteristics. The results of this research allow stating that interfacial and surface phenomena of the polymer-solid interface and composition play a decisive role in PTFE composites properties. Fillers hinder the relative movement of the PTFE molecules past one another and, in this way, reduce creep or deformation of the parts, reducing the wear rate of parts used in dynamic applications as well as the coefficient of thermal expansion. The necessary structural parameters of such polymer composites are provided by regimes of process equipment.

Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

NASA Technical Reports Server (NTRS)

Gao, Xiu-Jie; Turner, Travis L.; Burton, Deborah; Brinson, L. Catherine

2005-01-01

The usage of shape memory materials has extended rapidly to many fields, including medical devices, actuators, composites, structures and MEMS devices. For these various applications, shape memory alloys (SMAs) are available in various forms: bulk, wire, ribbon, thin film, and porous. In this work, the focus is on SMA hybrid composites with adaptive-stiffening or morphing functions. These composites are created by using SMA ribbons or wires embedded in a polymeric based composite panel/beam. Adaptive stiffening or morphing is activated via selective resistance heating or uniform thermal loads. To simulate the thermomechanical behavior of these composites, a SMA model was implemented using ABAQUS user element interface and finite element simulations of the systems were studied. Several examples are presented which show that the implemented model can be a very useful design and simulation tool for SMA hybrid composites.

Hurricanes, coral reefs and rainforests: resistance, ruin and recovery in the Caribbean

USGS Publications Warehouse

Lugo, Ariel E.; Rogers, Caroline S.; Nixon, Scott W.

2000-01-01

The coexistence of hurricanes, coral reefs, and rainforests in the Caribbean demonstrates that highly structured ecosystems with great diversity can flourish in spite of recurring exposure to intense destructive energy. Coral reefs develop in response to wave energy and resist hurricanes largely by virtue of their structural strength. Limited fetch also protects some reefs from fully developed hurricane waves. While storms may produce dramatic local reef damage, they appear to have little impact on the ability of coral reefs to provide food or habitat for fish and other animals. Rainforests experience an enormous increase in wind energy during hurricanes with dramatic structural changes in the vegetation. The resulting changes in forest microclimate are larger than those on reefs and the loss of fruit, leaves, cover, and microclimate has a great impact on animal populations. Recovery of many aspects of rainforest structure and function is rapid, though there may be long-term changes in species composition. While resistance and repair have maintained reefs and rainforests in the past, human impacts may threaten their ability to survive.

Damage-Resistant Composites Using Electrospun Nanofibers: A Multiscale Analysis of the Toughening Mechanisms.

PubMed

Daelemans, Lode; van der Heijden, Sam; De Baere, Ives; Rahier, Hubert; Van Paepegem, Wim; De Clerck, Karen

2016-05-11

Today, fiber-reinforced polymer composites are a standard material in applications where a high stiffness and strength are required at minimal weight, such as aerospace structures, ultralight vehicles, or even flywheels for highly efficient power storage systems. Although fiber-reinforced polymer composites show many advantages compared to other materials, delamination between reinforcing plies remains a major problem limiting further breakthrough. Traditional solutions that have been proposed to toughen the interlaminar region between reinforcing plies have already reached their limit or have important disadvantages such as a high cost or the need for adapted production processes. Recently, electrospun nanofibers have been suggested as a more viable interlaminar toughening method. Although the expected benefits are numerous, the research on composite laminates enhanced with electrospun nanofibrous veils is still very limited. The work that has been done so far is almost exclusively focused on interlaminar fracture toughness tests with different kinds of nanofibers, where typically a trial and error approach has been used. A thorough understanding of the micromechanical fracture mechanisms and the parameters to obtain toughened composites has not been reported as of yet, but it is crucial to advance the research and design highly damage-resistant composites. This article provides such insight by analyzing the nanofiber toughening effect on three different levels for several nanofiber types. Only by combining the results from different levels, a thorough understanding can be obtained. These levels correspond to the hierarchical nature of a composite: the laminate, the interlaminar region, and the matrix resin. It is found that each level corresponds to certain mechanisms that result in a toughening effect. The bridging of microcracks by electrospun nanofibers is the main toughening mechanism resulting in damage resistance. Nevertheless, the way in which the nanofiber bridging mechanism expresses itself is different for each scale and dependent on parameters linked to a certain scale. The multiscale analysis of the toughening mechanisms reported in this paper is therefore crucial for understanding the behavior of nanofiber toughened composites, and as such allows for designing novel, damage-resistant, nanofiber-toughened materials.

Welding of a corrosion-resistant composite material based on VT14 titanium alloy obtained using an electron beam emitted into the atmosphere

NASA Astrophysics Data System (ADS)

Golkovski, M. G.; Samoylenko, V. V.; Polyakov, I. A.; Lenivtseva, O. G.; Chakin, I. K.; Komarov, P. N.; Ruktuev, A. A.

2017-01-01

The study investigates the possibility of inert gas arc welding of a double layer composite material on a titanium base with an anti-corrosive layer obtained by fused deposition of a powder mix containing tantalum and niobium over a titanium base using an electron beam emitted into the atmosphere. Butt welding and fillet welding options were tested with two types of edge preparation. Welds were subjected to a metallographic examination including a structural study and an analysis of the chemical and phase composition of the welds. A conclusion was made regarding the possibility of using welding for manufacturing of items from the investigated composite material.

Changes in the mechanism of heat transfer in passing from microparticles to nanoparticles

NASA Astrophysics Data System (ADS)

Shakhov, F. M.; Meilakhs, A. P.; Eidelman, E. D.

2016-03-01

On the basis of experimental data on thermal conduction and sound velocity in composites obtained by sintering detonation nanodiamonds with the crystallite size of 4-5 nm and diamond micropowders with a grain size of about 10 μm at a high pressure (5-7 GPa) and high temperature (1200-1800°C), mechanisms of heat transfer in such structures are suggested. These mechanisms are shown to be different in composites of micro- and nanoparticles. In composites of micrometer particles, the conventional macroscopic mechanism of phonon propagation is active. In composites with a grain size of a few nanometers, the main contribution comes from thermal resistance on grain boundaries.

Mechanical and microwave absorbing properties of carbon-filled polyurethane.

PubMed

Kucerová, Z; Zajícková, L; Bursíková, V; Kudrle, V; Eliás, M; Jasek, O; Synek, P; Matejková, J; Bursík, J

2009-01-01

Polyurethane (PU) matrix composites were prepared with various carbon fillers at different filler contents in order to investigate their structure, mechanical and microwave absorbing properties. As fillers, flat carbon microparticles, carbon microfibers and multiwalled carbon nanotubes (MWNT) were used. The microstructure of the composite was examined by scanning electron microscopy and transmission electron microscopy. Mechanical properties, namely universal hardness, plastic hardness, elastic modulus and creep were assessed by means of depth sensing indentation test. Mechanical properties of PU composite filled with different fillers were investigated and the composite always exhibited higher hardness, elastic modulus and creep resistance than un-filled PU. Influence of filler shape, content and dispersion was also investigated.

Recent advances in 193-nm single-layer photoresists based on alternating copolymers of cycloolefins

NASA Astrophysics Data System (ADS)

Houlihan, Francis M.; Wallow, Thomas I.; Timko, Allen G.; Neria, E.; Hutton, Richard S.; Cirelli, Raymond A.; Nalamasu, Omkaram; Reichmanis, Elsa

1997-07-01

We report on our recent investigations on the formulation and processing of 193 nm single layer photoresists based on alternating copolymers of cycloolefins with maleic anhydride. Resists formulated with cycloolefin copolymers are compatible with 0.262 N tetramethylammonium developers, have excellent adhesion, sensitivity, etch resistance and thermal flow properties. The effect of polymer structure and composition, dissolution inhibitor structure and loading as well as the effect of the photoacid generator on the resist dissolution properties was investigated. Based on the results high contrast formulations were evaluated on a GCA XLS (NA equals 0.53, 4X reduction optics) deep-UV stepper to exhibit 0.27 micrometer L/S pair resolution with excellent photosensitivity. Based on the dissolution properties and a spectroscopic examination of the resist, we have designed materials that show less than 0.17 micrometer L/S pair resolution with 193 nm exposures. In this paper, the formulation methodology is detailed and the most recent results upon both with 248 and 193 nm irradiation are described.

Design and Performance of Property Gradient Ternary Nitride Coating Based on Process Control.

PubMed

Yan, Pei; Chen, Kaijie; Wang, Yubin; Zhou, Han; Peng, Zeyu; Jiao, Li; Wang, Xibin

2018-05-09

Surface coating is an effective approach to improve cutting tool performance, and multiple or gradient coating structures have become a common development strategy. However, composition mutations at the interfaces decrease the performance of multi-layered coatings. The key mitigation technique has been to reduce the interface effect at the boundaries. This study proposes a structure design method for property-component gradient coatings based on process control. The method produces coatings with high internal cohesion and high external hardness, which could reduce the composition and performance mutations at the interface. A ZrTiN property gradient ternary nitride coating was deposited on cemented carbide by multi-arc ion plating with separated Ti and Zr targets. The mechanical properties, friction behaviors, and cutting performances were systematically investigated, compared with a single-layer coating. The results indicated that the gradient coating had better friction and wear performance with lower wear rate and higher resistance to peeling off during sliding friction. The gradient coating had better wear and damage resistance in cutting processes, with lower machined surface roughness Ra. Gradient-structured coatings could effectively inhibit micro crack initiation and growth under alternating force and temperature load. This method could be extended to similar ternary nitride coatings.

Manufacturing technology of integrated textile-based sensor networks for in situ monitoring applications of composite wind turbine blades

NASA Astrophysics Data System (ADS)

Haentzsche, Eric; Mueller, Ralf; Huebner, Matthias; Ruder, Tristan; Unger, Reimar; Nocke, Andreas; Cherif, Chokri

2016-10-01

Based on in situ strain sensors consisting of piezo-resistive carbon filament yarns (CFYs), which have been successfully integrated into textile reinforcement structures during their textile-technological manufacturing process, a continuous load of fibre-reinforced plastic (FRP) components has been realised. These sensors are also suitable for structural health monitoring (SHM) applications. The two-dimensional sensor layout is made feasible by the usage of a modular warp yarn path manipulation unit. Using a functional model of a small wind turbine blade in thermoset composite design, the sensor function for basic SHM applications (e.g. static load monitoring) are demonstrated. Any mechanical loads along the pressure or suction side of the wind turbine blade can be measured and calculated via a correlative change in resistance of the CFYs within the textile reinforcement plies. Performing quasi-static load tests on both tensile specimen and full-scale wind turbine blade, elementary results have been obtained concerning electro-mechanical behaviour and spatial resolution of global and even local static stresses according to the CFY sensor integration length. This paper demonstrates the great potential of textile-based and textile-technological integrated sensors in reinforcement structures for future SHM applications of FRPs.

Rapid continuous synthesis of spherical reduced graphene ball-nickel oxide composite for lithium ion batteries

PubMed Central

Choi, Seung Ho; Ko, You Na; Lee, Jung-Kul; Kang, Yun Chan

2014-01-01

In this study, we synthesized a powder consisting of core-shell-structured Ni/NiO nanocluster-decorated graphene (Ni/NiO-graphene) by a simple process for use as an anodic material for lithium-ion batteries. First, a crumpled graphene powder consisting of uniformly distributed Ni nanoclusters was prepared by one-pot spray pyrolysis. This powder was subsequently transformed into the Ni/NiO-graphene composite by annealing at 300°C in air. The Ni/NiO-graphene composite powder exhibited better electrochemical properties than those of the hollow-structured NiO-Ni composite and pure NiO powders. The initial discharge and charge capacities of the Ni/NiO-graphene composite powder were 1156 and 845 mA h g−1, respectively, and the corresponding initial coulombic efficiency was 73%. The discharge capacities of the Ni/NiO-graphene, NiO-Ni, and pure NiO powders after 300 cycles were 863, 647, and 439 mA h g−1, respectively. The high stability of the Ni/NiO-graphene composite powder, attributable to the unique structure of its particles, resulted in it exhibiting long-term cycling stability even at a current density of 1500 mA g−1, as well as good rate performance. The structural stability of the Ni/NiO-graphene composite powder particles during cycling lowered the charge transfer resistance and improved the Li-ion diffusion rate. PMID:25167932

Fabrication and characterization of aerosol-jet printed strain sensors for multifunctional composite structures

NASA Astrophysics Data System (ADS)

Zhao, Da; Liu, Tao; Zhang, Mei; Liang, Richard; Wang, Ben

2012-11-01

Traditional multifunctional composite structures are produced by embedding parasitic parts, such as foil sensors, optical fibers and bulky connectors. As a result, the mechanical properties of the composites, especially the interlaminar shear strength (ILSS), could be largely undermined. In the present study, we demonstrated an innovative aerosol-jet printing technology for printing electronics inside composite structures without degrading the mechanical properties. Using the maskless fine feature deposition (below 10 μm) characteristics of this printing technology and a pre-cure protocol, strain sensors were successfully printed onto carbon fiber prepregs to enable fabricating composites with intrinsic sensing capabilities. The degree of pre-cure of the carbon fiber prepreg on which strain sensors were printed was demonstrated to be critical. Without pre-curing, the printed strain sensors were unable to remain intact due to the resin flow during curing. The resin flow-induced sensor deformation can be overcome by introducing 10% degree of cure of the prepreg. In this condition, the fabricated composites with printed strain sensors showed almost no mechanical degradation (short beam shearing ILSS) as compared to the control samples. Also, the failure modes examined by optical microscopy showed no difference. The resistance change of the printed strain sensors in the composite structures were measured under a cyclic loading and proved to be a reliable mean strain gauge factor of 2.2 ± 0.06, which is comparable to commercial foil metal strain gauge.

A Complex Shaped Reinforced Thermoplastic Composite Part Made of Commingled Yarns With Integrated Sensor

NASA Astrophysics Data System (ADS)

Risicato, Jean-Vincent; Kelly, Fern; Soulat, Damien; Legrand, Xavier; Trümper, Wolfgang; Cochrane, Cedric; Koncar, Vladan

2015-02-01

This paper focuses on the design and one shot manufacturing process of complex shaped composite parts based on the overbraiding of commingled yarns. The commingled yarns contain thermoplastic fibres used as the matrix and glass fibres as the reinforcement material. This technology reduces the flow path length for the melted thermoplastic and aims to improve the impregnation of materials with high viscosity. The tensile strength behaviour of the material was firstly investigated in order to evaluate the influence of the manufacturing parameters on flat structured braids that have been consolidated on a heating press. A good compatibility between the required geometry and the braiding process was observed. Additionally, piezo-resistive sensor yarns, based on glass yarns coated with PEDOT: PSS, have been successfully integrated within the composite structure. The sensor yarns have been inserted into the braided fabric, before consolidation. The inserted sensors provide the ability to monitor the structural health of the composite part in a real time. The design and manufacture of the complete complex shaped part has then been successfully achieved.

Action of ionizing radiation on epoxy resins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van de Voorde, M. E.

1970-12-01

The resistance of classical and experimental epoxy resins to irradiation was studied. The resistance to irradiation of epoxy resins of diverse compositions as well as the development of resins having a radioresistance that approaches that of certain ceramics are discussed. Sources of irradiation and the techniques of dosimetry used are described. The structures of certain epoxy resins and of hardeners are given. The preparation of these resins and their physical properties is described. The effects of radiation on epoxy resins, as well as conditions of irradiation, and suggested mechanisms for degradation of the irradiated resins are discussed. The relationship betweenmore » chemical structure of the resins and their physical properties is evaluated. (115 references) (JCB)« less

When are Racial Disparities in Education the Result of Racial Discrimination? A Social Science Perspective.

ERIC Educational Resources Information Center

Mickelson, Roslyn Arlin

2003-01-01

Synthesizes the social science research on racially correlated disparities in education, focusing on biological determinism (behavioral genetics); social structure (e.g., reproduction theory and resistance theory); school organization and opportunities to learn (e.g., resources, racial composition, and tracking); family background (financial,…

Structures, Design and Test: Materials

NASA Technical Reports Server (NTRS)

2004-01-01

NASA Marshall has developed a technology that combines a film/adhesive laydown module with fiber placement technology to enable the processing of composite prepreg tow/tape and films, foils, or adhesives on the same placement machine. The deve!opment of this technology grew out of NASA's need for lightweight, permeation-resistant cryogenic propellant tanks.

Structure and Properties of Intercalated Graphite Fiber-Polymer Composites.

DTIC Science & Technology

1983-07-07

resistivities of all com- nal graphite. Experimental evidence (1,2) in- plexes were determined both before and after dicated that the electrophilic N02...others show promise as fluorinating agents in chemical synthesisI21. At this point, however, so little is Known of processing parameters and long-term

Titanium diboride ceramic fiber composites for Hall-Heroult cells

DOEpatents

Besmann, Theodore M.; Lowden, Richard A.

1990-01-01

An improved cathode structure for Hall-Heroult cells for the electrolytic production of aluminum metal. This cathode structure is a preform fiber base material that is infiltrated with electrically conductive titanium diboride using chemical vapor infiltration techniques. The structure exhibits good fracture toughness, and is sufficiently resistant to attack by molten aluminum. Typically, the base can be made from a mat of high purity silicon carbide fibers. Other ceramic or carbon fibers that do not degrade at temperatures below about 1000 deg. C can be used.

Energy storage in structural composites by introducing CNT fiber/polymer electrolyte interleaves.

PubMed

Senokos, Evgeny; Ou, Yunfu; Torres, Juan Jose; Sket, Federico; González, Carlos; Marcilla, Rebeca; Vilatela, Juan J

2018-02-21

This work presents a method to produce structural composites capable of energy storage. They are produced by integrating thin sandwich structures of CNT fiber veils and an ionic liquid-based polymer electrolyte between carbon fiber plies, followed by infusion and curing of an epoxy resin. The resulting structure behaves simultaneously as an electric double-layer capacitor and a structural composite, with flexural modulus of 60 GPa and flexural strength of 153 MPa, combined with 88 mF/g of specific capacitance and the highest power (30 W/kg) and energy (37.5 mWh/kg) densities reported so far for structural supercapacitors. In-situ electrochemical measurements during 4-point bending show that electrochemical performance is retained up to fracture, with minor changes in equivalent series resistance for interleaves under compressive stress. En route to improving interlaminar properties we produce grid-shaped interleaves that enable mechanical interconnection of plies by the stiff epoxy. Synchrotron 3D X-ray tomography analysis of the resulting hierarchical structure confirms the formation of interlaminar epoxy joints. The manuscript discusses encapsulation role of epoxy, demonstrated by charge-discharge measurements of composites immersed in water, a deleterious agent for ionic liquids. Finally, we show different architectures free of current collector and electrical insulators, in which both CNT fiber and CF act as active electrodes.

Effect of Al content on impact resistance behavior of Al-Ti-B4C composite fabricated under air atmosphere.

PubMed

Zhao, Qian; Liang, Yunhong; Zhang, Zhihui; Li, Xiujuan; Ren, Luquan

2016-12-01

Reaction behavior, mechanical property and impact resistance of TiC-TiB 2 /Al composite reacted from Al-Ti-B 4 C system with various Al content via combination method of combustion synthesis and hot pressed sintering under air was investigated. Al content was the key point to the variation of mechanical property and impact resistance. Increasing Al content could increase the density, strength and toughness of the composite. Due to exorbitant ceramic content, 10wt.% and 20wt.% Al-Ti-B 4 C composites exhibited poor molding ability and machinability. Flexural strength, fracture toughness, compressive strength and impact toughness of 30-50wt.% Al-Ti-B 4 C composite were higher than those of Al matrix. The intergranular fracture dispersed and defused impact load and restricted crack extension, enhancing the impact resistance of the composite. The composite with 50wt.% Al content owned highest mechanical properties and impact resistance. The results were useful for the application of TiC-TiB 2 /Al composite in impact resistance field of ceramic reinforced Al matrix composite. Copyright © 2016 Elsevier Ltd. All rights reserved.

Creep and Environmental Durability of EBC/CMCs Under Imposed Thermal Gradient Conditions

NASA Technical Reports Server (NTRS)

Appleby, Matthew; Morscher, Gregory N.; Zhu, Dongming

2013-01-01

Interest in SiC fiber-reinforced SiC ceramic matrix composite (CMC) environmental barrier coating (EBC) systems for use in high temperature structural applications has prompted the need for characterization of material strength and creep performance under complex aerospace turbine engine environments. Stress-rupture tests have been performed on SiC/SiC composites systems, with varying fiber types and coating schemes to demonstrate material behavior under isothermal conditions. Further testing was conducted under exposure to thermal stress gradients to determine the effect on creep resistance and material durability. In order to understand the associated damage mechanisms, emphasis is placed on experimental techniques as well as implementation of non-destructive evaluation; including electrical resistivity monitoring. The influence of environmental and loading conditions on life-limiting material properties is shown.

A novel strategy for durable superhydrophobic coating on glass substrate via using silica chains to fix silica particles

NASA Astrophysics Data System (ADS)

Huang, Qi-Zhang; Fang, Yue-Yun; Liu, Peng-Yi; Zhu, Yan-Qing; Shi, Ji-Fu; Xu, Gang

2018-01-01

The practical application of superhydrophobic coatings on glass is usually restricted by their poor wear resistance due to the insufficient adhesion. A double-silica-layered structure was proposed to reinforce the coating adhesion on glass substrate. The wettability, surface morphologies, and chemical composition were investigated by water contact angle measurement, scanning electron microscopy (SEM), and fourier transformed infrared (FTIR) spectroscopy. The prepared superhydrophobic coating displays a good wear-resistance by emery paper and sand abrasion, which also has excellent thermal stability and UV resistance. This strategy shows a bright future for durable superhydrophobic coating on glass.

Effect of Translaminar Reinforcements and Hybridization on Damage Resistance and Tolerance of Composite Laminates

DTIC Science & Technology

2012-01-01

REINFORCEMENTS AND HYBRIDIZATION ON DAMAGE RESISTANCE AND TOLERANCE OF COMPOSITE LAMINATES It was shown that the damage resistance and tolerance of... laminated composites can be enhanced by the employment of translaminar reinforcements (TLR) such as stitching, z-pinning and 3D weaving and also by hybrid...Park, NC 27709-2211 Composite Laminates Resistance REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR/MONITOR’S ACRONYM

Bioinspired polydimethylsiloxane-based composites with high shear resistance against wet tissue.

PubMed

Fischer, Sarah C L; Levy, Oren; Kroner, Elmar; Hensel, René; Karp, Jeffrey M; Arzt, Eduard

2016-08-01

Patterned microstructures represent a potential approach for improving current wound closure strategies. Microstructures can be fabricated by multiple techniques including replica molding of soft polymer-based materials. However, polymeric microstructures often lack the required shear resistance with tissue needed for wound closure. In this work, scalable microstructures made from composites based on polydimethylsiloxane (PDMS) were explored to enhance the shear resistance with wet tissue. To achieve suitable mechanical properties, PDMS was reinforced by incorporation of polyethylene (PE) particles into the pre-polymer and by coating PE particle reinforced substrates with parylene. The reinforced microstructures showed a 6-fold enhancement, the coated structures even a 13-fold enhancement in Young׳s modulus over pure PDMS. Shear tests of mushroom-shaped microstructures (diameter 450µm, length 1mm) against chicken muscle tissue demonstrate first correlations that will be useful for future design of wound closure or stabilization implants. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Novel ammonia sensor based on polyaniline/polylactic acid composite films

NASA Astrophysics Data System (ADS)

Sotirov, S.; Bodurov, I.; Marudova, M.

2017-01-01

We propose a new type of ammonia sensor based on composite film between polyaniline (emeraldine base) dissolved in dimethylformamide, and poly(DL-lactic) acid dissolved in chloroform. The two solutions were mixed in weight ratio of the components 1:1 and cast on Al2O3 substrate, on which silver electrodes were deposited previously. The active layer structure and morphology were examined by atomic force microscopy. The sensor resistance at constant humidity and different ammonia concentrations was measured. It was found that an increase in the ammonia concentration leads to resistance increase. This result is explained in the terms of ionic interactions between the polyaniline and the ammonia, which change the permittivity of the sensor active media. A response between 2% and 590% was shown depending on the ammonia concentration. The sensor is reversible and possesses response time of typically 100 s. Based on the changes of the sensor resistance, ammonia concentration from 10 ppm to 1000 ppm could be detected.

Nanofabrication and characterization of PVA-organofiller/Ag nanocoatings on pMAD plasmids

NASA Astrophysics Data System (ADS)

Erdonmez, D.; Mosayyebi, S.; Erkan, K.; Salimi, K.; Nagizade, N.; Saglam, N.; Rzayev, Z. M. O.

2014-11-01

Nowadays, the most important problem in microbial researches is bacterial resistance which is carried out by DNA plasmids against antibacterial agents. The effect of antibacterial nanoparticles on bacteria is remarkable, but studies on the interactions of these particles with plasmids do not search or there are no adequate studies. We proposed that the nanoparticles, which are disrupted the self-assembled structure of plasmids, may decrease the resistance of bacteria, and therefore, increase the activity of utilized antibacterial agents. In this work, we synthesized polymer nanofiber webs samples by electrospinning technique from pure water solution of nanocomposites with different contents of silver nanoparticles, and surface morphology of nanofibers composites were characterized by SEM microscopy. Their interactions with pMAD DNA plasmids were investigated. It was demonstrated that the synthesized Ag-carrying nanohybrid composites with higher surface contacted areas were significantly inhibited the activity of plasmid DNA against bacterial resistance. Agreeing with obtained results, synthesized nanofiber coatings can be recommended for the widely applications in nanobiotechnology, nanomedicine, and bioengineering processing.

UiO-66-NH₂/GO Composite: Synthesis, Characterization and CO₂ Adsorption Performance.

PubMed

Cao, Yan; Zhang, Hongmei; Song, Fujiao; Huang, Tao; Ji, Jiayu; Zhong, Qin; Chu, Wei; Xu, Qi

2018-04-11

In this work, a new composite materials of graphene oxide (GO)-incorporated metal-organic framework (MOF)(UiO-66-NH₂/GO) were in-situ synthesized, and were found to exhibit enhanced high performances for CO₂ capture. X-ray diffraction (XRD), scanning electron microscope (SEM), N₂ physical adsorption, and thermogravimetric analysis (TGA) were applied to investigate the crystalline structure, pore structure, thermal stability, and the exterior morphology of the composite. We aimed to investigate the influence of the introduction of GO on the stability of the crystal skeleton and pore structure. Water, acid, and alkali resistances were tested for physical and chemical properties of the new composites. CO₂ adsorption isotherms of UiO-66, UiO-66-NH₂, UiO-66/GO, and UiO-66-NH₂/GO were measured at 273 K, 298 K, and 318 K. The composite UiO-66-NH₂/GO exhibited better optimized CO₂ uptake of 6.41 mmol/g at 273 K, which was 5.1% higher than that of UiO-66/GO (6.10 mmol/g). CO₂ adsorption heat and CO₂/N₂ selectivity were then calculated to further evaluate the CO₂ adsorption performance. The results indicated that UiO-66-NH₂/GO composites have a potential application in CO₂ capture technologies to alleviate the increase in temperature of the earth's atmosphere.

Seismic Performance of Composite Shear Walls Constructed Using Recycled Aggregate Concrete and Different Expandable Polystyrene Configurations.

PubMed

Liu, Wenchao; Cao, Wanlin; Zhang, Jianwei; Qiao, Qiyun; Ma, Heng

2016-03-02

The seismic performance of recycled aggregate concrete (RAC) composite shear walls with different expandable polystyrene (EPS) configurations was investigated. Six concrete shear walls were designed and tested under cyclic loading to evaluate the effect of fine RAC in designing earthquake-resistant structures. Three of the six specimens were used to construct mid-rise walls with a shear-span ratio of 1.5, and the other three specimens were used to construct low-rise walls with a shear-span ratio of 0.8. The mid-rise and low-rise shear walls consisted of an ordinary recycled concrete shear wall, a composite wall with fine aggregate concrete (FAC) protective layer (EPS modules as the external insulation layer), and a composite wall with sandwiched EPS modules as the insulation layer. Several parameters obtained from the experimental results were compared and analyzed, including the load-bearing capacity, stiffness, ductility, energy dissipation, and failure characteristics of the specimens. The calculation formula of load-bearing capacity was obtained by considering the effect of FAC on composite shear walls as the protective layer. The damage process of the specimen was simulated using the ABAQUS Software, and the results agreed quite well with those obtained from the experiments. The results show that the seismic resistance behavior of the EPS module composite for shear walls performed better than ordinary recycled concrete for shear walls. Shear walls with sandwiched EPS modules had a better seismic performance than those with EPS modules lying outside. Although the FAC protective layer slightly improved the seismic performance of the structure, it undoubtedly slowed down the speed of crack formation and the stiffness degradation of the walls.

Seismic Performance of Composite Shear Walls Constructed Using Recycled Aggregate Concrete and Different Expandable Polystyrene Configurations

PubMed Central

Liu, Wenchao; Cao, Wanlin; Zhang, Jianwei; Qiao, Qiyun; Ma, Heng

2016-01-01

The seismic performance of recycled aggregate concrete (RAC) composite shear walls with different expandable polystyrene (EPS) configurations was investigated. Six concrete shear walls were designed and tested under cyclic loading to evaluate the effect of fine RAC in designing earthquake-resistant structures. Three of the six specimens were used to construct mid-rise walls with a shear-span ratio of 1.5, and the other three specimens were used to construct low-rise walls with a shear-span ratio of 0.8. The mid-rise and low-rise shear walls consisted of an ordinary recycled concrete shear wall, a composite wall with fine aggregate concrete (FAC) protective layer (EPS modules as the external insulation layer), and a composite wall with sandwiched EPS modules as the insulation layer. Several parameters obtained from the experimental results were compared and analyzed, including the load-bearing capacity, stiffness, ductility, energy dissipation, and failure characteristics of the specimens. The calculation formula of load-bearing capacity was obtained by considering the effect of FAC on composite shear walls as the protective layer. The damage process of the specimen was simulated using the ABAQUS Software, and the results agreed quite well with those obtained from the experiments. The results show that the seismic resistance behavior of the EPS module composite for shear walls performed better than ordinary recycled concrete for shear walls. Shear walls with sandwiched EPS modules had a better seismic performance than those with EPS modules lying outside. Although the FAC protective layer slightly improved the seismic performance of the structure, it undoubtedly slowed down the speed of crack formation and the stiffness degradation of the walls. PMID:28773274

Biodegradation of the chitin-protein complex in crustacean cuticle

USGS Publications Warehouse

Artur, Stankiewicz B.; Mastalerz, Maria; Hof, C.H.J.; Bierstedt, A.; Flannery, M.B.; Briggs, D.E.G.; Evershed, R.P.

1998-01-01

Arthropod cuticles consist predominantly of chitin cross-linked with proteins. While there is some experimental evidence that this chitin-protein complex may resist decay, the chemical changes that occur during degradation have not been investigated in detail. The stomatopod crustacean Neogonodactylus oerstedii was decayed in the laboratory under anoxic conditions. A combination of pyrolysis-gas chromatography/mass spectrometry and FTIR revealed extensive chemical changes after just 2 weeks that resulted in a cuticle composition dominated by chitin. Quantitative analysis of amino acids (by HPLC) and chitin showed that the major loss of proteins and chitin occurred between weeks 1 and 2. After 8 weeks tyrosine, tryptophan and valine are the most prominent amino acid moieties, showing their resistance to degradation. The presence of cyclic ketones in the pyrolysates indicates that mucopolysaccharides or other bound non-chitinous carbohydrates are also resistant to decay. There is no evidence of structural degradation of chitin prior to 8 weeks when FTIR revealed a reduction in chitin-specific bands. The chemical changes are paralleled by structural changes in the cuticle, which becomes an increasingly open structure consisting of loose chitinous fibres. The rapid rate of decay in the experiments suggests that where chitin and protein are preserved in fossil cuticles degradation must have been inhibited.Arthropod cuticles consist predominantly of chitin cross-linked with proteins. While there is some experimental evidence that this chitin-protein complex may resist decay, the chemical changes that occur during degradation have not been investigated in detail. The stomatopod crustacean Neogonodactylus oerstedii was decayed in the laboratory under anoxic conditions. A combination of pyrolysis-gas chromatography/mass spectrometry and FTIR revealed extensive chemical changes after just 2 weeks that resulted in a cuticle composition dominated by chitin. Quantitative analysis of amino acids (by HPLC) and chitin showed that the major loss of proteins and chitin occurred between weeks 1 and 2. After 8 weeks tyrosine, tryptophan and valine are the most prominent amino acid moieties, showing their resistance to degradation. The presence of cyclic ketones in the pyrolysates indicates that mucopolysaccharides or other bound non-chitinous carbohydrates are also resistant to decay. There is no evidence of structural degradation of chitin prior to 8 weeks when FTIR revealed a reduction in chitin-specific bands. The chemical changes are paralleled by structural changes in the cuticle, which becomes an increasingly open structure consisting of loose chitinous fibres. The rapid rate of decay in the experiments suggests, that where chitin and protein are preserved in fossil cuticles degradation must have been inhibited.

Production and Structural Investigation of Polyethylene Composites with Modified Kaolin

NASA Astrophysics Data System (ADS)

Domka, L.; Malicka, A.; Stachowiak, N.

2008-08-01

The study was undertaken to evaluate the effect of the filler (kaolin) modification with silane coupling agents on the properties of the polyethylene (HDPE Hostalen ACP 5831) composites. Powder mineral fillers are added to polymers to modify the properties of the latter and to reduce the cost of their production. A very important factor is the filler dispersion in the polymer matrix. Kaolin modified with 3-methacryloxypropyltrimethoxysilane and pure kaolin were characterised by surface area, pore size, water absorbing capacity, paraffin oil absorbing capacity, bulk density, scanning electron microscopy observations and X-ray diffraction measurements. Their performance was characterised by determination of the mechanical resistance upon static stretching and tearing, and their structure was observed in scanning electron microscopy images. The results were compared to those obtained for the composites with unmodified filler and pure HDPE.

Preparation of Polyurethane/Graphite Composite Films with Stable Mechanical Property and Wear Resistance Underwater.

PubMed

Wang, Miaomiao; Wang, Zubin; Chen, Qirong; Meng, Xiangfu; Heng, Liping

2018-06-01

The wear resistance and stable mechanical properties affect the service life of the underwater functional materials to a certain extent. Unfortunately, the current study of underwater functional materials is rarely related to these aspects. Herein, we successfully designed and prepared polyurethane/graphite nanosheet (PU/GN) composite materials, which exhibited excellent wear resistance and stable mechanical properties underwater. The PU/GN composite films were prepared by evaporating a mixed solution of PU and GN on concave hexagonal honeycomb silicon templates. The mechanical properties of the composite films were determined by tensile test, and the wear resistance was evaluated by comparing the surface morphology before and after grind. By adjusting the content of graphite in the composite films, we found that the composite films containing 23 wt% GN had higher tensile strength and superior wear resistance. Moreover, this composite film showed an outstanding stability when expose to water. The impressive results along with simple preparation process made PU/GN composite films had potential applications in robust underwater functional materials.

Preparation and Sound Absorption Properties of a Barium Titanate/Nitrile Butadiene Rubber–Polyurethane Foam Composite with Multilayered Structure

PubMed Central

Jiang, Xueliang; Yang, Zhen; Wang, Zhijie; Zhang, Fuqing; You, Feng

2018-01-01

Barium titanate/nitrile butadiene rubber (BT/NBR) and polyurethane (PU) foam were combined to prepare a sound-absorbing material with an alternating multilayered structure. The effects of the cell size of PU foam and the alternating unit number on the sound absorption property of the material were investigated. The results show that the sound absorption efficiency at a low frequency increased when decreasing the cell size of PU foam layer. With the increasing of the alternating unit number, the material shows the sound absorption effect in a wider bandwidth of frequency. The BT/NBR-PU foam composites with alternating multilayered structure have an excellent sound absorption property at low frequency due to the organic combination of airflow resistivity, resonance absorption, and interface dissipation. PMID:29565321

Preparation and Sound Absorption Properties of a Barium Titanate/Nitrile Butadiene Rubber-Polyurethane Foam Composite with Multilayered Structure.

PubMed

Jiang, Xueliang; Yang, Zhen; Wang, Zhijie; Zhang, Fuqing; You, Feng; Yao, Chu

2018-03-22

Barium titanate/nitrile butadiene rubber (BT/NBR) and polyurethane (PU) foam were combined to prepare a sound-absorbing material with an alternating multilayered structure. The effects of the cell size of PU foam and the alternating unit number on the sound absorption property of the material were investigated. The results show that the sound absorption efficiency at a low frequency increased when decreasing the cell size of PU foam layer. With the increasing of the alternating unit number, the material shows the sound absorption effect in a wider bandwidth of frequency. The BT/NBR-PU foam composites with alternating multilayered structure have an excellent sound absorption property at low frequency due to the organic combination of airflow resistivity, resonance absorption, and interface dissipation.

Hypervelocity Impact Studies of Carbon Nanotubes and Fiber-Reinforced Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Khatiwada, Suman

This dissertation studies the hypervelocity impact characteristics of carbon nanotubes (CNTs), and investigates the use of CNTs as reinforcements in ultra-high molecular weight polyethylene (UHMWPE) fiber composites for hypervelocity impact shielding applications. The first part of this dissertation is aimed at developing an understanding of the hypervelocity impact response of CNTs--at the nanotube level. Impact experiments are designed with CNTs as projectiles to impact and crater aluminum plates. The results show that carbon nanotubes are resistant to the high-energy shock pressures and the ultra-high strain loading during hypervelocity impacts. Under our experimental conditions, single-walled carbon nanotubes survive impacts up to 4.07 km/s, but transform to graphitic ribbons and nanodiamonds at higher impact velocities. The nanodiamonds are metastable and transform to onion-like nanocarbon over time. Double-walled carbon nanotubes retain their form and structure even at impacts over 7 km/s. Higher hypervelocity impact resistance of DWCNTs could be attributed to the absorption of additional energy due to relative motion between the layers in the transverse direction of these coaxial nanotubes. The second part of this dissertation researches the effect of reinforcement of carbon nanotubes and their buckypapers on the hypervelocity impact shielding properties of UHMWPE-fiber composites arranged in a Whipple Shield configuration (a shield design used for the protection of the international space station from hypervelocity impacts by orbital debris). Composite laminates were prepared via compression molding and nanotube buckypapers via vacuum filtration. Dispersed nanotubes were introduced to the composite laminates via direct spraying onto the fabric prior to composite processing. The experimental results show that nanotubes dispersed in polymer matrix do not affect the hypervelocity impact resistance of the composite system. Nanotube buckypapers, however, improve the impact resistance of the composite, owing to the collective dampening of the shock wave amplitudes by the interconnected nanotube network in a buckypaper. The location of the buckypaper inside the composite, its thickness, and its surface modification with metals, all affect its hypervelocity impact shielding properties. Buckypaper coated with nickel and placed on the top surface of the UHMWPE-fiber composite provides the best impact resistance. Physical properties such as high bulk speed of sound in the nanotubes, and a combination of high density and high bulk speed of sound in nickel make the nickel-coated buckypaper a good hypervelocity impact shielding material. In addition, an explorative study on the use of nanograin metals for hypervelocity impact shielding was conducted.

Permeability and flammability study of composite sandwich structures for cryogenic applications

NASA Astrophysics Data System (ADS)

Bubacz, Monika

Fiber reinforced plastics offer advantageous specific strength and stiffness compared to metals and has been identified as candidates for the reusable space transportation systems primary structures including cryogenic tanks. A number of carbon and aramid fiber reinforced plastics have been considered for the liquid hydrogen tanks. Materials selection is based upon mechanical properties and containment performance (long and short term) and upon manufacturing considerations. The liquid hydrogen tank carries shear, torque, end load, and bending moment due to gusts, maneuver, take-off, landing, lift, drag, and fuel sloshing. The tank is pressurized to about 1.5 atmosphere (14.6psi or 0.1 MPa) differential pressure and on ascent maintains the liquid hydrogen at a temperature of 20K. The objective of the research effort into lay the foundation for developing the technology required for reliable prediction of the effects of various design, manufacturing, and service parameters on the susceptibility of composite tanks to develop excessive permeability to cryogenic fuels. Efforts will be expended on developing the materials and structural concepts for the cryogenic tanks that can meet the functional requirements. This will include consideration for double wall composite sandwich structures, with inner wall to meet the cryogenic requirements. The structure will incorporate nanoparticles for properties modifications and developing barriers. The main effort will be extended to tank wall's internal skin design. The main requirements for internal composite stack are: (1) introduction of barrier film (e.g. honeycomb material paper sheet) to reduce the wall permeability to hydrogen, (2) introduction of nanoparticles into laminate resin to prevent micro-cracking or crack propagation. There is a need to characterize and analyze composite sandwich structural damage due to burning and explosion. Better understanding of the flammability and blast resistance of the composite structures needs to be evaluated.

Application of C/C composites to the combustion chamber of rocket engines. Part 1: Heating tests of C/C composites with high temperature combustion gases

NASA Astrophysics Data System (ADS)

Tadano, Makoto; Sato, Masahiro; Kuroda, Yukio; Kusaka, Kazuo; Ueda, Shuichi; Suemitsu, Takeshi; Hasegawa, Satoshi; Kude, Yukinori

1995-04-01

Carbon fiber reinforced carbon composite (C/C composite) has various superior properties, such as high specific strength, specific modulus, and fracture strength at high temperatures of more than 1800 K. Therefore, C/C composite is expected to be useful for many structural applications, such as combustion chambers of rocket engines and nose-cones of space-planes, but C/C composite lacks oxidation resistivity in high temperature environments. To meet the lifespan requirement for thermal barrier coatings, a ceramic coating has been employed in the hot-gas side wall. However, the main drawback to the use of C/C composite is the tendency for delamination to occur between the coating layer on the hot-gas side and the base materials on the cooling side during repeated thermal heating loads. To improve the thermal properties of the thermal barrier coating, five different types of 30-mm diameter C/C composite specimens constructed with functionally gradient materials (FGM's) and a modified matrix coating layer were fabricated. In this test, these specimens were exposed to the combustion gases of the rocket engine using nitrogen tetroxide (NTO) / monomethyl hydrazine (MMH) to evaluate the properties of thermal and erosive resistance on the thermal barrier coating after the heating test. It was observed that modified matrix and coating with FGM's are effective in improving the thermal properties of C/C composite.

High Thermal Conductivity Polymer Matrix Composites (PMC) for Advanced Space Radiators

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Bowman, Cheryl; Beach, Duane

2007-01-01

High temperature polymer matrix composites (PMC) reinforced with high thermal conductivity (approx. 1000 W/mK) pitch-based carbon fibers are evaluated for a facesheet/fin structure of large space radiator systems. Significant weight reductions along with improved thermal performance, structural integrity and space durability toward its metallic counterparts were envisioned. Candidate commercial resin systems including Cyanate Esters, BMIs, and polyimide were selected based on thermal capabilities and processability. PMC laminates were designed to match the thermal expansion coefficient of various metal heat pipes or tubes. Large, but thin composite panels were successfully fabricated after optimizing cure conditions. Space durability of PMC with potential degradation mechanisms was assessed by simulated thermal aging tests in high vacuum, 1-3 x 10(exp -6) torr, at three temperatures, 227 C, 277 C, and 316 C for up to one year. Nanocomposites with vapor-grown carbon nano-fibers and exfoliated graphite flakes were attempted to improve thermal conductivity (TC) and microcracking resistance. Good quality nanocomposites were fabricated and evaluated for TC and durability including radiation resistance. TC was measured in both in-plan and thru-the-thickness directions, and the effects of microcracks on TC are also being evaluated. This paper will discuss the systematic experimental approaches, various performance-durability evaluations, and current subcomponent design and fabrication/manufacturing efforts.

The challenges of achieving good electrical and mechanical properties when making structural supercapacitors

NASA Astrophysics Data System (ADS)

Ciocanel, C.; Browder, C.; Simpson, C.; Colburn, R.

2013-04-01

The paper presents results associated with the electro-mechanical characterization of a composite material with power storage capability, identified throughout the paper as a structural supercapacitor. The structural supercapacitor uses electrodes made of carbon fiber weave, a separator made of Celgard 3501, and a solid PEG-based polymer blend electrolyte. To be a viable structural supercapacitor, the material has to have good mechanical and power storage/electrical properties. The literature in this area is inconsistent on which electrical properties are evaluated, and how those properties are assessed. In general, measurements of capacitance or specific capacitance (i.e. capacitance per unit area or per unit volume) are made, without considering other properties such as leakage resistance and equivalent series resistance of the supercapacitor. This paper highlights the significance of these additional electrical properties, discusses the fluctuation of capacitance over time, and proposes methods to improve the stability of the material's electric properties over time.

High temperature resistant cermet and ceramic compositions. [for thermal resistant insulators and refractory coatings

NASA Technical Reports Server (NTRS)

Phillips, W. M. (Inventor)

1978-01-01

High temperature oxidation resistance, high hardness and high abrasion and wear resistance are properties of cermet compositions particularly to provide high temperature resistant refractory coatings on metal substrates, for use as electrical insulation seals for thermionic converters. The compositions comprise a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride are also described.

Properties and rapid sintering of a nanostructured tetragonal zirconia composites

NASA Astrophysics Data System (ADS)

Shon, In-Jin; Yoon, Jin-Kook; Hong, Kyung-Tae

2017-09-01

4YSZ is generally used as oxygen sensors, fuel cells, thermal barrier and hip and knee joint replacements as a result of these excellent properties with its high biocompatibility, low density, good resistance against corrosion, high ionic conductivity, hard phase and melting point. However, 4YTZ with coarse grain has low resistance to wear and abrasion because of low hardness and low fracture toughness at room temperature. The fracture toughness and hardness of a 4YTZ can be improved by forming nanostructured composites and addition of a second hard phase. In this study, nanostuctured 4YTZ-graphene composites with nearly full density were achieved using high-frequency induction heated sintering for one min at a pressure of 80 MPa. The rapid consolidation and addition of graphene to 4YTZ retained the nano-scale structure of the ceramic by inhibiting grain growth. The grain size of 4YTZ was reduced remarkably by the addition of graphene and the addition of graphene to 4YTZ greatly improved the fracture toughness without decrease of hardness.

Preparation of the CNC/Ag/beeswax composites for enhancing antibacterial and water resistance properties of paper.

PubMed

Liu, Kai; Liang, Hunan; Nasrallah, Joseph; Chen, Lihui; Huang, Liulian; Ni, Yonghao

2016-05-20

An effective method of preparing composites containing inorganic (Ag) and organic (beeswax) particles was established in this study. Ag nanoparticles were first immobilized on the cellulose nanocrystals (CNC) during the reduction of AgNO3 in the presence of CNC, then mixed with beeswax by high speed stirring. Scanning transmission electron microscopy (STEM) images indicated that Ag and beeswax particles were uniformly dispersed and stable in the network structure formed by CNC. Upon coating on a paper surface, a layer of beeswax film was evident based on scanning electron microscopy (SEM) images. The dynamic contact angle and antibacterial activity tests indicated that the contact angle of coated paper reached 113.06° and the growth inhibition of Escherichia coli increased to 99.96%, respectively, at a coating amount of 21.53 g/m(2). When applied onto paper surface by coating, the CNC/Ag/beeswax composites can impact paper with antibacterial property and improved water resistance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Membrane fouling related to microbial community and extracellular polymeric substances at different temperatures.

PubMed

Gao, Da-Wen; Wen, Zhi-Dan; Li, Bao; Liang, Hong

2013-09-01

An anoxic-aerobic membrane bioreactor was established to investigate the role of microorganisms and microbial metabolites in membrane fouling at different temperatures. The results showed that the membrane fouling cycle at 303, 293, and 283 K were 30, 29, and 5.5 days, respectively. Polysaccharides dominated the extracellular polymeric substances (EPS) and soluble microbial products (SMP) at 303 and 293 K, instead, proteins was the predominant composition of metabolites at 283 K. The correlation coefficient (r(2)) was calculated to identify the relationship between temperature (T), filtration resistance (R) and compositions of EPS and SMP. In biocake, the EPS polysaccharides (EPSc) was the most correlative factor to temperature (T) and filtration resistance (R); in mixed liquor, the ratio of SMP polysaccharides to proteins (SMPc/p) was the most correlative factor. The microbial community structure and the dominant species was the major reason causing the change of EPS and SMP composition. Copyright © 2013 Elsevier Ltd. All rights reserved.

Evaluating the thermal damage resistance of graphene/carbon nanotube hybrid composite coatings

NASA Astrophysics Data System (ADS)

David, L.; Feldman, A.; Mansfield, E.; Lehman, J.; Singh, G.

2014-03-01

We study laser irradiation behavior of multiwalled carbon nanotubes (MWCNT) and chemically modified graphene (rGO)-composite spray coatings for use as a thermal absorber material for high-power laser calorimeters. Spray coatings on aluminum test coupon were exposed to increasing laser irradiance for extended exposure times to quantify their damage threshold and optical absorbance. The coatings, prepared at varying mass % of MWCNTs in rGO, demonstrated significantly higher damage threshold values at 2.5 kW laser power at 10.6 μm wavelength than carbon paint or MWCNTs alone. Electron microscopy and Raman spectroscopy of irradiated specimens show that the coating prepared at 50% CNT loading endure at least 2 kW.cm-2 for 10 seconds without significant damage. The improved damage resistance is attributed to the unique structure of the composite in which the MWCNTs act as an efficient absorber of laser light while the much larger rGO sheets surrounding them, dissipate the heat over a wider area.

Structure and properties of composite iron-based coatings obtained by the electromechanical technique

NASA Astrophysics Data System (ADS)

Dubinskii, N. A.

2007-09-01

The influence of the electrolyte temperature and current density on the content of inclusions of powder particles in composite coatings obtained by the electrochemical technique has been investigated. It has been found that the wear resistance of iron coatings with inclusions of powder particles of aluminum, kaolin, and calcium silicate increases from 5 to 10 times compared to coating without inclusions of disperse particles, and the friction coefficient therewith decreases from 0.097 to 0.026. It has been shown that the mechanical properties of iron obtained by the method of electrochemical deposition depend on their fine structure. The regimes of deposition of iron-based coatings have been optimized.

Foam composite structures. [for fire retardant airframe materials

NASA Technical Reports Server (NTRS)

Delano, C. B.; Milligan, R. J.

1976-01-01

The need to include fire resistant foams into state of the art aircraft interior paneling to increase passenger safety in aircraft fires was studied. Present efforts were directed toward mechanical and fire testing of panels with foam inclusions. Skinned foam filled honeycomb and PBI structural foams were the two constructions investigated with attention being directed toward weight/performance/cost trade-off. All of the new panels demonstrated improved performance in fire and some were lighter weight but not as strong as the presently used paneling. Continued efforts should result in improved paneling for passenger safety. In particular the simple partial filling (fire side) of state-of-the-art honeycomb with fire resistant foams with little sacrifice in weight would result in panels with increased fire resistance. More important may be the retarded rate of toxic gas evolution in the fire due to the protection of the honeycomb by the foam.

Vegetative resistance to flow in south Florida; summary of vegetation sampling at sites NESRS3 and P33, Shark River slough, November, 1996

USGS Publications Warehouse

Carter, Virginia; Reel, J.T.; Rybicki, N.B.; Ruhl, H.; Gammon, P.T.; Lee, J.K.

1999-01-01

The U.S. Geological Survey is one of many agencies participating in the effort to restore the South Florida Everglades. We are sampling and characterizing the vegetation at selected sites in the Everglades as part of a study to quantify vegetative flow resistance. The objectives of the vegetation sampling are (1) to provide detailed information on species composition, vegetation characteristics, vegetation structure, and biomass for quantification of vegetative resistance to flow, and (2) to use this information to classify the vegetation and to improve existing vegetation maps for use with numerical models of surface-water flow. Vegetation was sampled at two sites in the Shark River Slough in November, 1996. The data collected and presented here include those for live and dead standing sawgrass, other dead material, periphyton biomass, vegetation characteristics and structure, and leaf area index.

Low resistance Ohmic contact to p-type crystalline silicon via nitrogen-doped copper oxide films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xinyu, E-mail: xinyu.zhang@anu.edu.au; Wan, Yimao; Bullock, James

2016-08-01

This work explores the application of transparent nitrogen doped copper oxide (CuO{sub x}:N) films deposited by reactive sputtering to create hole-selective contacts for p-type crystalline silicon (c-Si) solar cells. It is found that CuO{sub x}:N sputtered directly onto crystalline silicon is able to form an Ohmic contact. X-ray photoelectron spectroscopy and Raman spectroscopy measurements are used to characterise the structural and physical properties of the CuO{sub x}:N films. Both the oxygen flow rate and the substrate temperature during deposition have a significant impact on the film composition, as well as on the resulting contact resistivity. After optimization, a low contactmore » resistivity of ∼10 mΩ cm{sup 2} has been established. This result offers significant advantages over conventional contact structures in terms of carrier transport and device fabrication.« less

Combination of sorption properties of polydimethylsiloxane and solid-phase extraction sorbents in a single composite material for the passive sampling of polar and apolar pesticides in water.

PubMed

Martin, Alexis; Margoum, Christelle; Coquery, Marina; Randon, Jérôme

2016-10-01

Passive sampling techniques have been developed as an alternative method for in situ integrative monitoring of trace levels of neutral pesticides in environmental waters. The objective of this work was to develop a new receiving phase for pesticides with a wide range of polarities in a single step. We describe the development of three new composite silicone rubbers, combining polydimethylsiloxane mechanical and sorption properties with solid-phase extraction sorbents, prepared as a receiving phase for passive sampling. A composite silicone rubber composed of polydimethylsiloxane/poly(divinylbenzene-co-N-vinylpyrrolidone) was selected by batch experiments for its high sorption properties for pesticides with octanol-water partition coefficients ranging from 2.3 to 5.5. We named this composite material "Polar/Apolar Composite Silicone Rubber". A structural study by scanning electron microscopy confirmed the homogeneous dispersion of the sorbent particles and the encapsulation of particles within the polydimethylsiloxane matrix. We also demonstrate that this composite material is resistant to common solvents used for the back-extraction of analytes and has a maximal resistance temperature of 350°C. Therefore, the characteristics of the "Polar/Apolar Composite Silicone Rubber" meet most of the criteria for use as a receiving phase for the passive sampling of pesticides. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural, dielectric and impedance spectroscopic studies of Ni0.5Zn0.5-xLixFe2O4 nanocrystalline ferrites

NASA Astrophysics Data System (ADS)

Venkatesh, Davuluri; Ramesh, K. V.

2017-09-01

Nanocrystalline lithium substituted Ni-Zn ferrites with composition Ni0.5Zn0.5-xLixFe2O4 (x = 0.00-0.25 in steps of 0.05) were synthesized by the citrate gel auto-combustion method and were sintered at 1000∘C for 4 h in air atmosphere. The structural, dielectric, impedance spectroscopic and magnetic properties were studied by using X-ray diffraction, impedance analyzer and vibrating sample magnetometer respectively. The X-ray diffraction patterns confirm that all samples exhibit a single phase cubic spinel structure. Suitable cation distribution for all compositions has been proposed by using the X-ray diffraction line intensity calculations and the theoretical lattice parameter for each composition was observed in close agreement with the experimental ones and thereby supporting the proposed distribution. An increase in the saturation magnetization was observed up to x = 0.10 level of Li+ substitution and thereafter magnetization reduced for higher concentrations to the highest level of Li+ substitution. The dielectric constant and the DC resistivity of Ni-Zn-Li ferrites were noticed to decrease with increase in the Li+ ion concentration. The impedance spectroscopic studies by using the Cole-Cole plots were studied in order to obtain the relaxation time, grain resistance and grain capacitance. AC conductivity initially remained almost independent of frequency for lower frequencies and thereafter for higher frequencies the AC conductivity increased with increase of Lithium concentration.

Novel Swelling-Resistant Sodium Alginate Membrane Branching Modified by Glycogen for Highly Aqueous Ethanol Solution Pervaporation.

PubMed

Ji, Chen-Hao; Xue, Shuang-Mei; Xu, Zhen-Liang

2016-10-12

A novel carbohydrate chain cross-linking method of sodium alginate (SA) is proposed in which glycogen with the branched-chain structure is utilized to cross-link with SA matrix by the bridging of glutaraldehyde (GA). The active layer of SA composite ceramic membrane modified by glycogen and GA for pervaporation (PV) demonstrates great advantages. The branched structure increases the chain density of the active layer, which compresses the free volume between the carbohydrate chains of SA. Large amounts of hydroxyl groups are consumed during the reaction with GA, which reduces the hydrogen bond formation between water molecules and the polysaccharide matrix. The two factors benefit the active layer with great improvement in swelling resistance, promoting the potential of the active layer for the dehydration of an ethanol-water solution containing high water content. Meanwhile, the modified active layer is loaded on the rigid α-Al 2 O 3 ceramic membrane by dip-coating method with the enhancement of anti-deformation and controllable thickness of the active layer. Characterization techniques such as SEM, AFM, XRD, FTIR, XPS, and water contact angle are utilized to observe the composite structure and surface morphology of the composite membrane, to probe the free volume variation, and to determine the chemical composition and hydrophilicity difference of the active layer caused by the different glycogen additive amounts. The membrane containing 3% glycogen in the selective layer demonstrates the flux at 1250 g m -2 h -1 coupled with the separation factor of 187 in the 25 wt % water content feed solution at the operating temperature of 75 °C, reflecting superior pervaporation processing capacity compared with the general organic PV membranes in the same condition.

Structural singularities in Ge(x)Te(100-x) films.

PubMed

Piarristeguy, A A; Micoulaut, M; Escalier, R; Jóvári, P; Kaban, I; van Eijk, J; Luckas, J; Ravindren, S; Boolchand, P; Pradel, A

2015-08-21

Structural and calorimetric investigation of Ge(x)Te(100-x) films over wide range of concentration 10 < x < 50 led to evidence two structural singularities at x ∼ 22 at. % and x ∼ 33-35 at. %. Analysis of bond distribution, bond variability, and glass thermal stability led to conclude to the origin of the first singularity being the flexible/rigid transition proposed in the framework of rigidity model and the origin of the second one being the disappearance of the undercooled region resulting in amorphous materials with statistical distributions of bonds. While the first singularity signs the onset of the Ge-Ge homopolar bonds, the second is related to compositions where enhanced Ge-Ge correlations at intermediate lengthscales (7.7 Å) are observed. These two threshold compositions correspond to recently reported resistance drift threshold compositions, an important support for models pointing the breaking of homopolar Ge-Ge bonds as the main phenomenon behind the ageing of phase change materials.

Effect of farnesol on structure and composition of Staphylococcus epidermidis biofilm matrix.

PubMed

Gomes, Fernanda; Teixeira, Pilar; Cerca, Nuno; Azeredo, Joana; Oliveira, Rosário

2011-10-01

Staphylococcus epidermidis is the most frequent cause of nosocomial sepsis and catheter-related infections in which biofilm formation is considered to be one of the main virulence mechanisms. Moreover, their increased resistance to conventional antibiotic therapy enhances the need to develop new therapeutical agents. Farnesol, a natural sesquiterpenoid present in many essential oils, has been described as impairing bacterial growth. The aim of this study was to evaluate the effect of farnesol on the structure and composition of biofilm matrix of S. epidermidis. Biofilms formed in the presence of farnesol (300 μM) contained less biomass, and displayed notable changes in the composition of the biofilm matrix. Changes in the spacial structure were also verified by confocal scanning laser microscopy (CSLM). The results obtained by the quantification of extracellular polymers and by wheat germ agglutinin (WGA) fluorescent detection of glycoproteins containing β(1→4)-N-acetyl-D: -glucosamine support the hypothesis that farnesol causes disruption of the cytoplasmic membrane and consequently release of cellular content.

Characterization of structures of the Nankai Trough accretionary prism from integrated analyses of LWD log response, resistivity images and clay mineralogy of cuttings: Expedition 338 Site C0002

NASA Astrophysics Data System (ADS)

Jurado, Maria Jose; Schleicher, Anja

2014-05-01

The objective of our research is a detailed characterization of structures on the basis of LWD oriented images and logs,and clay mineralogy of cuttings from Hole C0002F of the Nankai Trough accretionary prism. Our results show an integrated interpretation of structures derived from borehole images, petrophysical characterization on LWD logs and cuttings mineralogy. The geometry of the structure intersected at Hole C0002F has been characterized by the interpretation of oriented borehole resistivity images acquired during IODP Expedition 338. The characterization of structural features, faults and fracture zones is based on a detailed post-cruise interpretation of bedding and fractures on borehole images and also on the analysis of Logging While Drilling (LWD) log response (gamma radioactivity, resistivity and sonic logs). The interpretation and complete characterization of structures (fractures, fracture zones, fault zones, folds) was achieved after detailed shorebased reprocessing of resistivity images, which allowed to enhance bedding and fracture's imaging for geometry and orientation interpretation. In order to characterize distinctive petrophysical properties based on LWD log response, it could be compared with compositional changes derived from cuttings analyses. Cuttings analyses were used to calibrate and to characterize log response and to verify interpretations in terms of changes in composition and texture at fractures and fault zones defined on borehole images. Cuttings were taken routinely every 5 m during Expedition 338, indicating a clay-dominated lithology of silty claystone with interbeds of weakly consolidated, fine sandstones. The main mineralogical components are clay minerals, quartz, feldspar and calcite. Selected cuttings were taken from areas of interest as defined on LWD logs and images. The clay mineralogy was investigated on the <2 micron clay-size fraction, with special focus on smectite and illite minerals. Based on X-ray diffraction analysis measured at room temperature and a relative humidity of ~30%, we compared the shape and size of illite and smectite, as well as their water content and their polytypes. The comparison of cuttings mineralogy with logging while drilling (LWD) data allowed us to characterize structural, petrophysical and mineralogical properties at fracture and fault zones. We also analyzed the relationship between deformation structures and compositional and mineralogical changes. We established a correlation between observed results on clay mineralogy and log responses in relation with the structures and trends characterized on logging data. In general, the log data provide a good correlation with the actual mineralogy and the relative abundance of clay. In particular we analyzed trends characterized by smectite water layers as indication of compaction. These trends were correlated with log response (on sonic velocity) within Unit IV. Our results show the integration of logging data and cutting sample analyses as a valuable tool for characterization of petrophysical and mineralogical changes of the structures of the Nankai accretionary prism.

Bond slip detection of concrete-encased composite structure using shear wave based active sensing approach

NASA Astrophysics Data System (ADS)

Zeng, Lei; Parvasi, Seyed Mohammad; Kong, Qingzhao; Huo, Linsheng; Lim, Ing; Li, Mo; Song, Gangbing

2015-12-01

Concrete-encased composite structure exhibits improved strength, ductility and fire resistance compared to traditional reinforced concrete, by incorporating the advantages of both steel and concrete materials. A major drawback of this type of structure is the bond slip introduced between steel and concrete, which directly reduces the load capacity of the structure. In this paper, an active sensing approach using shear waves to provide monitoring and early warning of the development of bond slip in the concrete-encased composite structure is proposed. A specimen of concrete-encased composite structure was investigated. In this active sensing approach, shear mode smart aggregates (SAs) embedded in the concrete act as actuators and generate desired shear stress waves. Distributed piezoceramic transducers installed in the cavities of steel plates act as sensors and detect the wave response from shear mode SAs. Bond slip acts as a form of stress relief and attenuates the wave propagation energy. Experimental results from the time domain analysis clearly indicate that the amplitudes of received signal by lead zirconate titanate sensors decreased when bond slip occurred. In addition, a wavelet packet-based analysis was developed to compute the received signal energy values, which can be used to determine the initiation and development of bond slip in concrete-encased composite structure. In order to establish the validity of the proposed method, a 3D finite element analysis of the concrete-steel bond model is further performed with the aid of the commercial finite element package, Abaqus, and the numerical results are compared with the results obtained in experimental study.

Effect of Chemical Structure and Network Formation on Physical Properties of Di(Cyanate Ester) Thermosets (Post Print)

DTIC Science & Technology

2012-02-06

with glass or polyethylene reinforcements for use in radomes and antenna structures,4 where their unusually low dielectric constant and low moisture ...are prized for their elevated glass transition temperature, good adhesion to metals, resistance to degradation by moisture , and excellent flame...on the performance of cyanate ester resins and composites. Cyanate ester monomers, particularly when catalyzed, may react with adventitious moisture to

Procurement of a Nanoindenter for Structure-Function Analyses of Biologically Inspired High Performance Composite Materials

DTIC Science & Technology

2012-01-13

abalone shell (Figures 3, 4). Here, we can see that the damage is significantly mitigated in the nacreous regions while cracks formed in the Calcitic...properties. Page 5 / 11 Identifying the crack propagation mechanisms helps to identify new designs for impact resistant materials, so the...human tooth from dentin – dentin/ enamel junction – enamel . It is clear that higher resolution scans are necessary to interrogate local structure

Significant enhancement in volumetric and gravimetric capacitance of Cu-TiO2/PPY composite for supercapacitor application

NASA Astrophysics Data System (ADS)

Purty, B.; Choudhary, R. B.

2018-04-01

Copper doped titanium dioxide-polypyrrole (Cu-TiO2/PPY) composite was successfully synthesized via chemical oxidative in-situ polymerization process. The structural and morphological properties of Cu-TiO2/PPY composite were investigated using X-ray diffractometer (XRD), field emission electron microscopy (FESEM) and transmission electron microscopy(TEM) techniques. The electrochemical properties of as-synthesized composite were studied using cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopic (EIS) techniques. The novel Cu-TiO2/PPY composite showed enhanced volumetric capacitance ˜714 F cm-1 and gravimetric capacitance ˜674 F g-1 at 1 A g-1. In addition an excellent coulombic efficiency and comparabley low charge transfer resistance than pure PPY suggests improved supercapacitive performance of Cu-TiO2/PPY composite as an electrode material.

The monolithic carbon aerogels and aerogel composites for electronics and thermal protection applications

NASA Astrophysics Data System (ADS)

Lu, Sheng; Guo, Hui; Zhou, Yugui; Liu, Yuanyuan; Jin, Zhaoguo; Liu, Bin; Zhao, Yingmin

2017-09-01

Monolithic carbon aerogels have been prepared by condensation polymerization and high temperature pyrolysis. The morphology of carbon aerogels are characterized by SEM. The pore structure is characterized by N2 adsorption-desorption technique. Monolithic carbon aerogels are mesoporous nanomaterials. Carbon fiber reinforced carbon aerogel composites are prepared by in-situ sol-gel process. Fiber reinforced carbon aerogel composites are of high mechanical strength. The thermal response of the fiber reinforced aerogel composite samples are tested in an arc plasma wind tunnel. Carbon aerogel composites show good thermal insulation capability and high temperature resistance in inert atmosphere even at ultrahigh temperature up to 1800 °C. The results show that they are suitable for applications in electrodes for supercapacitors/ Lithium-ion batteries and aerospace thermal protection area.

Processing and Characterization of Graphene/Polyimide-Nickel Oxide Hybrid Nanocomposites for Advanced Energy Storage in Supercapacitor Applications

NASA Astrophysics Data System (ADS)

Okafor, Patricia A.

This research is focused on enhancing electrochemical properties/energy storage capabilities of graphene-polyimide composites. The composite's dense morphology/structure limits ionic penetration owing to high bulk resistances resulting in poor electrochemical performance. Modification of the composite's morphology by incorporation of facile pores during curing increases total available surface area to electrolyte species. Presence of pores increases adsorption sites for double layer formation and increases overall capacitance. In this work, aromatic polyimide precursors were reacted in the presence of nano-graphene fillers to synthesize graphene-polyimide composite films. The resulting composite was very stiff and dense with a high glass transition temperature (Tg) of 400 °C and storage modulus of 7.20 GPa. Selective decomposition of a thermally labile poly(acrylic ester) resin introduced into the composite during synthesis creates pores of varying size and shapes which increases available surface area of embedded stacked graphene sheets available for ion adsorption and double layer formation. Proper control over pore size and specific surface area of pores was required to ensure good performance in terms of both power delivery rate and energy storage capacity. Dynamic mechanical studies on modified composite showed very good mechanical property while shifts in imide peaks to lower wave numbers in Raman and Fourier transform spectroscopy (FTIR) confirms presence of chemical interaction between graphene filler and polymer matrix confirming uniform dispersion of fillers in the material. Thermogravimetric analysis (TGA) shows thermal stability for the composite systems at temperatures above 700°C. To further optimize material's energy storage capabilities, a hybrid composite was formed by depositing relatively cheap nickel oxide onto the modified porous composite system by a two-step process. A remarkable improvement in electrochemical properties up to an order of magnitude was observed. Electrochemical performance of the hybrid system showed strong dependence on deposition current density, deposition time and substrate pore morphology. Increased NiO particle size (aggregates) was observed with increased deposition time and current density which had a significant impact on charge transfer resistance and specific capacitance. Several correlations were made between composite's morphology and obtained properties. The material's morphology showed direct correlation with double layer capacitance, charge capacity, bulk resistance and sheet conductivity measured using cyclic voltammetry (CV), cyclic charge discharge (CCD), electrochemical impedance spectroscopy (EIS) and four probe measurements respectively. It was observed that smaller well distributed pores showed enhanced properties compared to larger pores. Material's overall performance shows a linear dependence on porosity. The overall electrochemical and electrical behavior of the system is directly linked to the composite's morphology and structure as will be demonstrated in this thesis work.

Composition for radiation shielding

DOEpatents

Kronberg, J.W.

1994-08-02

A composition for use as a radiation shield is disclosed. The shield has a depleted uranium core for absorbing gamma rays and a bismuth coating for preventing chemical corrosion and absorbing gamma rays. Alternatively, a sheet of gadolinium may be positioned between the uranium core and the bismuth coating for absorbing neutrons. The composition is preferably in the form of a container for storing materials that emit radiation such as gamma rays and neutrons. The container is preferably formed by casting bismuth around a pre-formed uranium container having a gadolinium sheeting, and allowing the bismuth to cool. The resulting container is a structurally sound, corrosion-resistant, radiation-absorbing container. 2 figs.

Composition for radiation shielding

DOEpatents

Kronberg, James W.

1994-01-01

A composition for use as a radiation shield. The shield has a depleted urum core for absorbing gamma rays and a bismuth coating for preventing chemical corrosion and absorbing gamma rays. Alternatively, a sheet of gadolinium may be positioned between the uranium core and the bismuth coating for absorbing neutrons. The composition is preferably in the form of a container for storing materials that emit radiation such as gamma rays and neutrons. The container is preferably formed by casting bismuth around a pre-formed uranium container having a gadolinium sheeting, and allowing the bismuth to cool. The resulting container is a structurally sound, corrosion-resistant, radiation-absorbing container.

Rinse-resistant superhydrophobic block copolymer fabrics by electrospinning, electrospraying and thermally-induced self-assembly

NASA Astrophysics Data System (ADS)

Wu, Jie; Li, Xin; Wu, Yang; Liao, Guoxing; Johnston, Priscilla; Topham, Paul D.; Wang, Linge

2017-11-01

An inherent problem that restricts the practical application of superhydrophobic materials is that the superhydrophobic property is not sustainable; it can be diminished, or even lost, when the surface is physically damaged. In this work, we present an efficient approach for the fabrication of superhydrophobic fibrous fabrics with great rinse-resistance where a block copolymer has been electrospun into a nanofibrous mesh while micro-sized beads have been subsequently electrosprayed to give a morphologically composite material. The intricate nano- and microstructure of the composite was then fixed by thermally annealing the block copolymer to induce self-assembly and interdigitation of the microphase separated domains. To demonstrate this approach, a polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) nanofibrous scaffold was produced by electrospinning before SEBS beads were electrosprayed into this mesh to form a hierarchical micro/nanostructure of beads and fibers. The effects of type and density of SEBS beads on the surface morphology and wetting properties of composite membranes were studied extensively. Compared with a neat SEBS fibrous mesh, the composite membrane had enhanced hydrophobic properties. The static water contact angle increased from 139° (±3°) to 156° (±1°), while the sliding angle decreased to 8° (±1°) from nearly 90°. In order to increase the rinse-resistance of the composite membrane, a thermal annealing step was applied to physically bind the fibers and beads. Importantly, after 200 h of water flushing, the hierarchical surface structure and superhydrophobicity of the composite membrane were well retained. This work provides a new route for the creation of superhydrophobic fabrics with potential in self-cleaning applications.

High temperature resistant cermet and ceramic compositions

NASA Technical Reports Server (NTRS)

Phillips, W. M. (Inventor)

1978-01-01

Cermet compositions having high temperature oxidation resistance, high hardness and high abrasion and wear resistance, and particularly adapted for production of high temperature resistant cermet insulator bodies are presented. The compositions are comprised of a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Also disclosed are novel ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride.

Progressive Fracture of [0/90/ + or - Theta]s Composite Structure Under Uniform Pressure Load

NASA Technical Reports Server (NTRS)

Gotsis, Pascalis K.; Chamis, Christos C.; Gotsis, Christos K.; Mouratidis, Ericos

2007-01-01

S-Glass/epoxy [0/90/plus or minus theta]s for theta =45 deg., 60 deg., and 75 deg. laminated fiber-reinforced composite stiffened plate was simulated to investigated for damage and fracture progression under uniform pressure. An integrated computer code was augmented for the simulation of the damage initiation, growth, accumulation, and propagation to fracture and to structural collapse. Results show in detail the damage progression sequence and structural fracture resistance during different degradation stages. Damage through the thickness of the laminate initiated first at [0/90/plus or minus 45]s at 15.168 MPa (2200 psi), followed by [0/90/plus or minus 60]s at 16.96 MPa (2460 psi) and finally by [0/90/plus or minus 75]s at 19.3 MPa (2800 psi). After damage initiation happened the cracks propagate rapidly to structural fracture.

Microstructure and Properties of (TiB2 + NiTi)/Ti Composite Coating Fabricated by Laser Cladding

NASA Astrophysics Data System (ADS)

Lin, Yinghua; Lei, Yongping; Fu, Hanguang; Lin, Jian

2015-10-01

Agglomerated TiB2 particle and network-like structure-reinforced titanium matrix composite coatings were prepared by laser cladding of the Ni + TiB2 + Ti preplaced powders on Ti-6Al-4V alloy. The network-like structure mainly consisted of NiTi and Ni3Ti. Through the experiment, it was found that the size of agglomerated particle gradually decreased with the increase of Ti content, but the number of the network-like structure first increased and then disappeared. In-situ reaction competition mechanism and the formation of network-like structure were discussed. The average micro-hardness gradually decreased with the increase of Ti content, but the average fracture toughness gradually increased. Meanwhile, the wear resistance of the coatings is higher than that of the substrate, but the wear loss of the coatings is gradually increased with the increase of Ti content.

Stress-corrosion cracking in metals

NASA Technical Reports Server (NTRS)

1971-01-01

Criteria and recommended practices for preventing stress-corrosion cracking from impairing the structural integrity and flightworthiness of space vehicles are presented. The important variables affecting stress-corrosion cracking are considered to be the environment, including time and temperature; metal composition, and structure; and sustained tensile stress. For designing spacecraft structures that are free of stress-corrosion cracking for the service life of the vehicle the following rules apply: (1) identification and control of the environments to which the structure will be exposed during construction, storage, transportation, and use; (2) selection of alloy compositions and tempers which are resistant to stress-corrosion cracking in the identified environment; (3) control of fabrication and other processes which may introduce residual tensile stresses or damage the material; (4) limitation of the combined residual and applied tensile stresses to below the threshold stress level for the onset of cracking throughout the service life of the vehicle; and (5) establishment of a thorough inspection program.

Frequencies of polymorphisms associated with BSE resistance differ significantly between Bos taurus, Bos indicus, and composite cattle

PubMed Central

Brunelle, Brian W; Greenlee, Justin J; Seabury, Christopher M; Brown, Charles E; Nicholson, Eric M

2008-01-01

Background Transmissible spongiform encephalopathies (TSEs) are neurodegenerative diseases that affect several mammalian species. At least three factors related to the host prion protein are known to modulate susceptibility or resistance to a TSE: amino acid sequence, atypical number of octapeptide repeats, and expression level. These factors have been extensively studied in breeds of Bos taurus cattle in relation to classical bovine spongiform encephalopathy (BSE). However, little is currently known about these factors in Bos indicus purebred or B. indicus × B. taurus composite cattle. The goal of our study was to establish the frequency of markers associated with enhanced susceptibility or resistance to classical BSE in B. indicus purebred and composite cattle. Results No novel or TSE-associated PRNP-encoded amino acid polymorphisms were observed for B. indicus purebred and composite cattle, and all had the typical number of octapeptide repeats. However, differences were observed in the frequencies of the 23-bp and 12-bp insertion/deletion (indel) polymorphisms associated with two bovine PRNP transcription regulatory sites. Compared to B. taurus, B. indicus purebred and composite cattle had a significantly lower frequency of 23-bp insertion alleles and homozygous genotypes. Conversely, B. indicus purebred cattle had a significantly higher frequency of 12-bp insertion alleles and homozygous genotypes in relation to both B. taurus and composite cattle. The origin of these disparities can be attributed to a significantly different haplotype structure within each species. Conclusion The frequencies of the 23-bp and 12-bp indels were significantly different between B. indicus and B. taurus cattle. No other known or potential risk factors were detected for the B. indicus purebred and composite cattle. To date, no consensus exists regarding which bovine PRNP indel region is more influential with respect to classical BSE. Should one particular indel region and associated genotypes prove more influential with respect to the incidence of classical BSE, differences regarding overall susceptibility and resistance for B. indicus and B. taurus cattle may be elucidated. PMID:18808703

Controllable two-scale network architecture and enhanced mechanical properties of (Ti5Si3+TiBw)/Ti6Al4V composites.

PubMed

Jiao, Y; Huang, L J; Duan, T B; Wei, S L; Kaveendran, B; Geng, L

2016-09-13

Novel Ti6Al4V alloy matrix composites with a controllable two-scale network architecture were successfully fabricated by reaction hot pressing (RHP). TiB whiskers (TiBw) were in-situ synthesized around the Ti6Al4V matrix particles, and formed the first-scale network structure (FSNS). Ti5Si3 needles (Ti5Si3) precipitated in the β phase around the equiaxed α phase, and formed the secondary-scale network structure (SSNS). This resulted in increased deformation compatibility accompanied with enhanced mechanical properties. Apart from the reinforcement distribution and the volume fraction, the ratio between Ti5Si3 and TiBw fraction were controlled. The prepared (Ti5Si3 + TiBw)/Ti6Al4V composites showed higher tensile strength and ductility than the composites with a one-scale microstructure, and superior wear resistance over the Ti6Al4V alloy under dry sliding wear conditions at room temperature.

Multi-slice nanostructured WS2@rGO with enhanced Li-ion battery performance and a comprehensive mechanistic investigation.

PubMed

Li, Honglin; Yu, Ke; Fu, Hao; Guo, Bangjun; Lei, Xiang; Zhu, Ziqiang

2015-11-28

A thin nanoslice structured WS2@reduced graphene oxide (rGO) composite was successfully fabricated by a facile hydrothermal synthesis method. The layered structure and morphology of the composite were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The WS2@rGO composite structure demonstrated significantly enhanced rate capability performance in comparison with pristine WS2 when used as an anode material for lithium-ion batteries (LIBs). The composite demonstrated a capacity of 565 mA h g(-1) after 100 cycles when cycled at 0.1 A g(-1) and it could still deliver a stable capacity of about 337 mA h g(-1) at 2 A g(-1). Electrochemical impedance spectroscopy (EIS) measurement showed that the synergistic effect between WS2 and rGO could remarkably reduce the contact resistance and improve the corresponding electrochemical performances. In order to analyze and interpret the corresponding results from a theoretically sound perspective, first principles calculations was further performed to investigate the corresponding inner mechanisms of pristine WS2 and WS2@graphene composite. The nudged elastic band (NEB) method was used to investigate the diffusion properties of Li in the different structures. Molecular dynamics (MD) simulation and Young's modulus calculation were further employed to explore the stability and mechanical properties of the two structures for the first time. These new perspectives pave the way for the design and fabrication of graphene-TMDs based composites as the next generation of LIB anode materials with high power density and cycling stability.

Biological soil crusts across disturbance–recovery scenarios: effect of grazing regime on community dynamics.

PubMed

Concostrina-Zubiri, L; Huber-Sannwald, E; Martínez, I; Flores Flores, J L; Reyes-Agüero, J A; Escude, A; Belnap, J

Grazing represents one of the most common disturbances in drylands worldwide, affecting both ecosystem structure and functioning. Despite the efforts to understand the nature and magnitude of grazing effects on ecosystem components and processes, contrasting results continue to arise. This is particularly remarkable for the biological soil crust (BSC) communities (i.e., cyanobacteria, lichens, and bryophytes), which play an important role in soil dynamics. Here we evaluated simultaneously the effect of grazing impact on BSC communities (resistance) and recovery after livestock exclusion (resilience) in a semiarid grassland of Central Mexico. In particular, we examined BSC species distribution, species richness, taxonomical group cover (i.e., cyanobacteria, lichen, bryophyte), and composition along a disturbance gradient with different grazing regimes (low, medium, high impact) and along a recovery gradient with differently aged livestock exclosures (short-, medium-, long-term exclusion). Differences in grazing impact and time of recovery from grazing both resulted in slight changes in species richness; however, there were pronounced shifts in species composition and group cover. We found we could distinguish four highly diverse and dynamic BSC species groups: (1) species with high resistance and resilience to grazing, (2) species with high resistance but low resilience, (3) species with low resistance but high resilience, and (4) species with low resistance and resilience. While disturbance resulted in a novel diversity configuration, which may profoundly affect ecosystem functioning, we observed that 10 years of disturbance removal did not lead to the ecosystem structure found after 27 years of recovery. These findings are an important contribution to our understanding of BCS dynamics from a species and community perspective placed in a land use change context.

Biological soil crusts across disturbance-recovery scenarios: effect of grazing regime on community dynamics

USGS Publications Warehouse

Concostrina-Zubiri, L.; Huber-Sannwald, E.; Martínez, I.; Flores Flores, J. L.; Reyes-Agüero, J. A.; Escudero, A.; Belnap, Jayne

2014-01-01

Grazing represents one of the most common disturbances in drylands worldwide, affecting both ecosystem structure and functioning. Despite the efforts to understand the nature and magnitude of grazing effects on ecosystem components and processes, contrasting results continue to arise. This is particularly remarkable for the biological soil crust (BSC) communities (i.e., cyanobacteria, lichens, and bryophytes), which play an important role in soil dynamics. Here we evaluated simultaneously the effect of grazing impact on BSC communities (resistance) and recovery after livestock exclusion (resilience) in a semiarid grassland of Central Mexico. In particular, we examined BSC species distribution, species richness, taxonomical group cover (i.e., cyanobacteria, lichen, bryophyte), and composition along a disturbance gradient with different grazing regimes (low, medium, high impact) and along a recovery gradient with differently aged livestock exclosures (short-, medium-, long-term exclusion). Differences in grazing impact and time of recovery from grazing both resulted in slight changes in species richness; however, there were pronounced shifts in species composition and group cover. We found we could distinguish four highly diverse and dynamic BSC species groups: (1) species with high resistance and resilience to grazing, (2) species with high resistance but low resilience, (3) species with low resistance but high resilience, and (4) species with low resistance and resilience. While disturbance resulted in a novel diversity configuration, which may profoundly affect ecosystem functioning, we observed that 10 years of disturbance removal did not lead to the ecosystem structure found after 27 years of recovery. These findings are an important contribution to our understanding of BCS dynamics from a species and community perspective placed in a land use change context.

Characterization of Reinforced Structural Composites with Carbon Nanotubes Grown Directly on the Fibers/Fabrics Using the PopTube Approach

NASA Astrophysics Data System (ADS)

Guin, William Edward

Carbon nanotubes (CNTs) are ideal candidates for the reinforcement of the matrix and interphase zone in polymer matrix composites (PMCs), due to their ability to more effectively bind the reinforcing fibers to the matrix material. This can lead to the enhancement of several critical composite properties - including interfacial shear strength and interlaminar fracture toughness - that are typically associated with a composite material's resistance to delamination. Direct dispersion of CNTs into the matrix of the composites has been shown to be very difficult. A more effective way to reinforce PMCs using CNTs is to grow CNTs directly on the reinforcing fibers. To this end, a novel technique used to grow CNTs directly on carbon fibers has been developed at The University of Alabama and Auburn University. This method, referred to as the PopTube Approach, uses microwave irradiation to grow CNTs at room temperature in air, without the need for inert gas protection or additional feed stock gases. The simple nature of the PopTube Approach lends itself to large-scale, high-yield manufacturing that can be done in a cost effective manner. However, before this technique is developed beyond the laboratory scale, its effectiveness as a route to produce CNT-reinforced composites must be evaluated in a comprehensive manner. The objective of this work is to do just that - characterize the mechanical properties of CNT-reinforced composites produced via the PopTube Approach. A systematic experimental program is carried out to provide a comprehensive assessment of the effects of the PopTube Approach on a wide range of composite mechanical properties. Results show that the PopTube Approach provides for enhanced resistance to delamination with respect to several different loading events. Fractography studies are used to qualitatively understand the mechanisms responsible for these improvements in delamination resistance on the micro-scale. Results also suggest that improvements in delamination resistance via CNT reinforcement may come at the expense of the tensile properties of PMCs - which gives rise to the conclusion that in practice, the degree and manner of CNT reinforcement in PMCs should be carefully considered on an application-by-application basis. Together, the collection of studies performed herein provides a wide-ranging quantitative and qualitative assessment of the effects of the PopTube Approach CNT reinforcement scheme on the mechanical properties and behavior of polymer matrix composites.

Ultrasonic-microwave assisted synthesis of three-dimensional polyvinyl alcohol carbonate/graphene oxide sponge and studies of surface resistivity and thermal stability.

PubMed

Song, Yunna; Li, Yuehai; Li, Jihui; Li, Yongshen; Niu, Shuai; Li, Ning

2018-04-01

In the article, graphene oxide (GO) was prepared by flake graphite, nitric acid and peroxyacetic acid via the sonochemical method and characterized, and polyvinyl alcohol carbonate/GO composite (PVAC/GO composite) was synthesized by polyvinyl alcohol (PVA), dimethyl carbonate (DMC) and GO via the approach of transesterification in the case of ultrasonic-microwave synergistic effects and characterized, and three-dimensional PVAC/GO sponge (3D PVAC/GO sponge) was manufactured by PVAC/GO composite via the foaming approach and characterized, and the thermal stability and surface resistivity of 3D PVAC/GO sponge were investigated. Based on those, it had been attested that PVAC polymer was structured by DMC and PVA and had the six-membered lactone rings and the ether bonds, and PVAC/GO composite was constituted by 2D GO lattice and PVAC polymer, and 3D PVAC/GO sponge was constructed by PVAC/GO composite, and the surface resistivity of 3D PVAC/GO sponge with 0.00, 0.60, 1.20, 1.80 and 2.40 g of GO were 9.07  ×  10 7 , 6.02  ×  10 7 , 4.65  ×  10 7 , 2.47  ×  10 7 and 1.06  ×  107 O/sq, and the thermal stability of 3D PVAC/GO sponge had improved. Copyright © 2017 Elsevier B.V. All rights reserved.

LiV3O8/Polytriphenylamine Composites with Enhanced Electrochemical Performances as Cathode Materials for Rechargeable Lithium Batteries

PubMed Central

Li, Wenjuan; Zhu, Limin; Yu, Ziheng; Xie, Lingling; Cao, Xiaoyu

2017-01-01

LiV3O8/polytriphenylamine composites are synthesized by a chemical oxidative polymerization process and applied as cathode materials for rechargeable lithium batteries (RLB). The structure, morphology, and electrochemical performances of the composites are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, galvanostatic discharge/charge tests, and electrochemical impedance spectroscopy. It was found that the polytriphenylamine particles were composited with LiV3O8 nanorods which acted as a protective barrier against the side reaction of LiV3O8, as well as a conductive network to reduce the reaction resistance among the LiV3O8 particles. Among the LiV3O8/polytriphenylamine composites, the 17 wt % LVO/PTPAn composite showed the largest d100 spacing. The electrochemical results showed that the 17 wt % LVO/PTPAn composite maintained a discharge capacity of 271 mAh·g−1 at a current density of 60 mA·g−1, as well as maintaining 236 mAh·g−1 at 240 mA·g−1 after 50 cycles, while the bare LiV3O8 sample retained only 169 and 148 mAh·g−1, respectively. Electrochemical impedance spectra (EIS) results implied that the 17 wt % LVO/PTPAn composite demonstrated a decreased charge transfer resistance and increased Li+ ion diffusion ability, therefore manifesting better rate capability and cycling performance compared to the bare LiV3O8 sample. PMID:28772705

Effect of polyamide 6 on the morphology and electrical conductivity of carbon black-filled polypropylene composites

PubMed Central

Zhang, Xuewei; Liu, Jiang; Wang, Yi

2017-01-01

Carbon black (CB)-filled polypropylene (PP) with surface resistivity between 106 and 109 Ω sq−1 is the ideal antistatic plastic material in the electronics and electric industry. However, a large amount of CB may have an adverse effect on the mechanical properties and processing performance of the material, thus an improved ternary system is developed. Blends of CB-filled PP and polyamide 6 (PA6) have been prepared by melt blending in order to obtain electrically conductive polymer composites with a low electrical percolation threshold based on the concept of double percolation. The morphological developments of these composites were studied by scanning electron microscopy. The results showed that CB particles were selectively dispersed in PA6 phases due to the good interaction and interfacial adhesion between CB and PA6. At the same CB loadings, the surface resistivity of PP/PA6/CB composite was smaller than that of PP/CB composite system, which indicated the better conductivity in the former composite. The increasing amount of PA6 in the composites changed the morphology from a typical sea–island morphology to a co-continuous morphology. What is more, with 8 wt% of CB and PP/PA6 phase ratio of 70/30 in which the PP and PA6 phases formed a co-continuous structure, the electrical conductivity of the composite peaked at 2.01 × 105 Ω sq−1. PMID:29308223

Failure of structural elements made of polymer supported composite materials during the multiyear natural aging

NASA Astrophysics Data System (ADS)

Blinkov, Pavel; Ogorodov, Leonid; Grabovyy, Peter

2018-03-01

Modern high-rise construction introduces a number of limitations and tasks. In addition to durability, comfort and profitability, projects should take into account energy efficiency and environmental problems. Polymer building materials are used as substitutes for materials such as brick, concrete, metal, wood and glass, and in addition to traditional materials. Plastic materials are light, can be formed into complex shapes, durable and low, and also possess a wide range of properties. Plastic materials are available in various forms, colors and textures and require minimal or no color. They are resistant to heat transfer and diffusion of moisture and do not suffer from metal corrosion or microbial attack. Polymeric materials, including thermoplastics, thermoset materials and wood-polymer composites, have many structural and non-structural applications in the construction industry. They provide unique and innovative solutions at a low cost, and their use is likely to grow in the future. A number of polymer composite materials form complex material compositions, which are applied in the construction in order to analyze the processes of damage accumulation under the conditions of complex nonstationary loading modes, and to determine the life of structural elements considering the material aging. This paper present the results of tests on short-term compression loading with a deformation rate of v = 2 mm/min using composite samples of various shapes and sizes.

Toughened and corrosion- and wear-resistant composite structures and fabrication methods thereof

DOEpatents

Seals, Roland D; Ripley, Edward B; Hallman, Russell L

2014-04-08

Composite structures having a reinforced material interjoined with a substrate and methods of creating a composite material interjoined with a substrate. In some embodiments the composite structure may be a line or a spot or formed by reinforced material interjoined with the substrate. The methods typically include disposing a precursor material comprising titanium diboride and/or titanium monoboride on at least a portion of the substrate and heating the precursor material and the at least a portion of the substrate in the presence of an oxidation preventative until at least a portion of the precursor material forms reinforced material interjoined with the substrate. The precursor material may be disposed on the substrate as a sheet or a tape or a slurry or a paste. Localized surface heating may be used to heat the precursor material. The reinforced material typically comprises a titanium boron compound, such as titanium monoboride, and preferably comprises .beta.-titanium. The substrate is typically titanium-bearing, iron-bearing, or aluminum-bearing. A welding rod is provided as an embodiment. The welding rod includes a metal electrode and a precursor material is disposed adjacent at least a portion of the metal electrode. A material for use in forming a composite structure is provided. The material typically includes a precursor material that includes one or more materials selected from the following group: titanium diboride and titanium monoboride. The material also typically includes a flux.

Static and dynamic strain energy release rates in toughened thermosetting composite laminates

NASA Technical Reports Server (NTRS)

Cairns, Douglas S.

1992-01-01

In this work, the static and dynamic fracture properties of several thermosetting resin based composite laminates are presented. Two classes of materials are explored. These are homogeneous, thermosetting resins and toughened, multi-phase, thermosetting resin systems. Multi-phase resin materials have shown enhancement over homogenous materials with respect to damage resistance. The development of new dynamic tests are presented for composite laminates based on Width Tapered Double Cantilevered Beam (WTDCB) for Mode 1 fracture and the End Notched Flexure (ENF) specimen. The WTDCB sample was loaded via a low inertia, pneumatic cylinder to produce rapid cross-head displacements. A high rate, piezo-electric load cell and an accelerometer were mounted on the specimen. A digital oscilloscope was used for data acquisition. Typical static and dynamic load versus displacement plots are presented. The ENF specimen was impacted in three point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions were determined analytically and experimentally. The test results for Mode 1 fracture are relatively insensitive to strain rate effects for the laminates tested in this study. The test results from Mode 2 fracture indicate that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. While the static fracture properties of the homogeneous systems may be relatively high, the apparent Mode 2 dynamic critical strain energy release rate drops significantly. The results indicate that static Mode 2 fracture testing is inadequate for determining the fracture performance of composite structures subjected to conditions such as low velocity impact. A good correlation between the basic Mode 2 dynamic fracture properties and the performance is a combined material/structural Compression After Impact (CAI) test is found. These results underscore the importance of examining rate-dependent behavior for determining the longevity of structures manufactured from composite materials.

Flexible Transparent Conductive Films with High Performance and Reliability Using Hybrid Structures of Continuous Metal Nanofiber Networks for Flexible Optoelectronics.

PubMed

Park, Juyoung; Hyun, Byung Gwan; An, Byeong Wan; Im, Hyeon-Gyun; Park, Young-Geun; Jang, Junho; Park, Jang-Ung; Bae, Byeong-Soo

2017-06-21

We report an Ag nanofiber-embedded glass-fabric reinforced hybrimer (AgNF-GFRHybrimer) composite film as a reliable and high-performance flexible transparent conducting film. The continuous AgNF network provides superior optoelectronic properties of the composite film by minimizing transmission loss and junction resistance. In addition, the excellent thermal/chemical stability and mechanical durability of the GFRHybrimer matrix provides enhanced mechanical durability and reliability of the final AgNF-GFRHybrimer composite film. To demonstrate the availability of our AgNF-GFRHybrimer composite as a transparent conducting film, we fabricated a flexible organic light-emitting diode (OLED) device on the AgNF-GFRHybrimer film; the OLED showed stable operation during a flexing.

Synthesis and characterization of MoS2/Ti composite coatings on Ti6Al4V prepared by laser cladding

NASA Astrophysics Data System (ADS)

Yang, Rongjuan; Liu, Zongde; Wang, Yongtian; Yang, Guang; Li, Hongchuan

2013-02-01

The MoS2/Ti composite coating with sub-micron grade structure has been prepared on Ti6Al4V by laser method under argon protection. The morphology, microstructure, microhardness and friction coefficient of the coating were examined. The results indicated that the molybdenum disulfide was decomposed during melting and resolidification. The phase organization of composite coating mainly consisted of ternary element sulfides, molybdenum sulfides and titanium sulfides. The friction coefficient of and the surface roughness the MoS2/Ti coating were lower than those of Ti6Al4V. The composite coating exhibits excellent adhesion to the substrates, less surface roughness, good wear resistance and harder surface.

Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application

NASA Technical Reports Server (NTRS)

Laakso, J. H.; Straayer, J. W.

1974-01-01

A final program summary is reported for test and evaluation activities that were conducted for space shuttle web selection. Large scale advanced composite shear web components were tested and analyzed to evaluate application of advanced composite shear web construction to a space shuttle orbiter thrust structure. The shear web design concept consisted of a titanium-clad + or - 45 deg boron/epoxy web laminate stiffened with vertical boron-epoxy reinforced aluminum stiffeners and logitudinal aluminum stiffening. The design concept was evaluated to be efficient and practical for the application that was studied. Because of the effects of buckling deflections, a requirement is identified for shear buckling resistant design to maximize the efficiency of highly-loaded advanced composite shear webs.

Performance evaluation of a non-woven lithium ion battery separator prepared through a paper-making process

NASA Astrophysics Data System (ADS)

Huang, Xiaosong

2014-06-01

Porous separator functions to electrically insulate the negative and positive electrodes yet communicate lithium ions between the two electrodes when infiltrated with a liquid electrolyte. The separator must fulfill numerous requirements (e.g. permeability, wettability, and thermal stability) in order to optimize the abuse tolerance and electrochemical performance of a battery. Non-woven mat separators have advantages such as high porosity and heat resistance. However, their applications in lithium ion batteries are very limited as their inadequate pore structures could cause accelerated battery performance degradation and even internal short. This work features the development of thermally stable non-woven composite separators using a low cost paper-making process. The composite separators offer significantly improved thermal dimensional stability and exhibit superior wettability by the liquid electrolyte compared to a conventional polypropylene separator. The open porous structures of the non-woven composite separators also resulted in high effective ionic conductivities. The electrochemical performance of the composite separators was tested in coin cells. Stable cycle performances and improved rate capabilities have been observed for the coin cells with these composite separators.

The impact of a freshwater fish farm on the community of tetracycline-resistant bacteria and the structure of tetracycline resistance genes in river water.

PubMed

Harnisz, Monika; Korzeniewska, Ewa; Gołaś, Iwona

2015-06-01

The aim of this study was to assess the impact of a fish farm on the structure of antibiotic resistant bacteria and antibiotic resistance genes in water of Drwęca River. Samples of upstream river waters; post-production waters and treated post-production waters from fish farm; as well as downstream river waters were monitored for tetracycline resistant bacteria, tetracycline resistant genes, basic physico-chemical parameters and tetracyclines concentration. The river waters was characterized by low levels of pollution, which was determined based on water temperature, pH and concentrations of dissolved oxygen and tetracycline antibiotics. Culture-dependent (heterotrophic plate counts, counts of bacteria resistant to oxytetracycline (OTC(R)) and doxycycline (DOX(R)), minimum inhibitory concentrations for oxytetracycline and doxycycline, multidrug resistance of OTC(R) and DOX(R), qualitative composition of OTC(R) and DOX(R), prevalence of tet genes in resistant isolates) and culture-independent surveys (quantity of tet gene copies) revealed no significant differences in the abundance of antibiotic-resistant bacteria and antibiotic resistance genes between the studied samples. The only way in which the fish farm influenced water quality in the Drwęca River was by increasing the diversity of tetracycline-resistance genes. However, it should also be noted that the bacteria of the genera Aeromonas sp. and Acinetobacter sp. were able to transfer 6 out of 13 tested tet genes into Escherichiacoli, which can promote the spread of antibiotic resistance in the environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Brazing of Stainless Steels to Yttria Stabilized Zirconia (YSZ) Using Silver -Base Brazes

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay; Shpargel, Tarah P.; Asthana, Rajiv

2005-01-01

Three silver-base brazes containing either noble metal palladium (Palcusil-10 and Palcusil-15) or active metal titanium (Ticusil) were evaluated for high-temperature oxidation resistance, and their effectiveness in joining yttria stabilized zirconia (YSZ) to a corrosion-resistant ferritic stainless steel. Thermogravimetric analysis (TGA), and optical- and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) were used to evaluate the braze oxidation behavior and the structure and chemistry of the YSZ/braze/steel joints. The effect of the braze type and processing conditions on the interfacial microstructure and composition of the joint regions is discussed with reference to the chemical changes that occur at the interface. It was found that chemical interdiffusion of the constituents of YSZ, steel and the brazes led to compositional changes and/or interface reconstruction, and metallurgically sound joints.

Fire Resistance of Large-Scale Cross-Laminated Timber Panels

NASA Astrophysics Data System (ADS)

Henek, Vladan; Venkrbec, Václav; Novotný, Miloslav

2017-12-01

Wooden structures are increasingly being used in the construction of residential buildings. A common and often published reason to avoid wooden structures is their insufficient fire resistance, which reduces bearing capacity. For this reason, composite sandwich structures began to be designed to eliminate this drawback, as well as others. Recently, however, the trend is for a return to the original, wood-only variant and a search is underway for new technical means of improving the properties of such structures. Many timber structure technologies are known, but structures made from cross-laminated timber (CLT) panels have been used very often in recent years. CLT panels, also known as X-LAM, are currently gaining popularity in Europe. In the case of CLT panels composed of several layers of boards, they can be said to offer a certain advantage in that after the surface layer of a board has burnt and the subsurface layer has dried, oxygen is not drawn to the unburned wood for further combustion and thus the burning process ceases. CLT panels do not need to be specially modified or coated with fire resistant materials, although they are usually lined with gypsum-fibre fire resistant boards due to guidelines set out in the relevant standards. This paper presents a new method for the assessment of load-bearing perimeter walls fabricated from CLT panels without the use of an inner fire-retardant lining to ensure fire resistance at the level required by European standards (i.e. those harmonized for the Czech construction industry). The calculations were verified through laboratory tests which show that better parameters can be achieved during the classification of structures from the fire resistance point of view. The aim of the article is to utilize the results of assessment and testing by an accredited laboratory in order to demonstrate the possibilities of using CLT panels for the construction of multistorey as well as multi-purpose buildings in the Czech Republic.

Process and Structural Health Monitoring of Composite Structures with Embedded Fiber Optic Sensors and Piezoelectric Transducers

NASA Astrophysics Data System (ADS)

Keulen, Casey James

Advanced composite materials are becoming increasingly more valuable in a plethora of engineering applications due to properties such as tailorability, low specific strength and stiffness and resistance to fatigue and corrosion. Compared to more traditional metallic and ceramic materials, advanced composites such as carbon, aramid or glass reinforced plastic are relatively new and still require research to optimize their capabilities. Three areas that composites stand to benefit from improvement are processing, damage detection and life prediction. Fiber optic sensors and piezoelectric transducers show great potential for advances in these areas. This dissertation presents the research performed on improving the efficiency of advanced composite materials through the use of embedded fiber optic sensors and surface mounted piezoelectric transducers. Embedded fiber optic sensors are used to detect the presence of resin during the injection stage of resin transfer molding, monitor the degree of cure and predict the remaining useful life while in service. A sophisticated resin transfer molding apparatus was developed with the ability of embedding fiber optics into the composite and a glass viewing window so that resin flow sensors could be verified visually. A novel technique for embedding optical fiber into both 2- and 3-D structures was developed. A theoretical model to predict the remaining useful life was developed and a systematic test program was conducted to verify this model. A network of piezoelectric transducers was bonded to a composite panel in order to develop a structural health monitoring algorithm capable of detecting and locating damage in a composite structure. A network configuration was introduced that allows for a modular expansion of the system to accommodate larger structures and an algorithm based on damage progression history was developed to implement the network. The details and results of this research are contained in four manuscripts that are included in Appendices A-D while the body of the dissertation provides background information and a summary of the results.

Structural Integrity Of Low-Velocity Impacted C/SIC Ceramic Matrix Composites

NASA Astrophysics Data System (ADS)

Knoche, R.; Drose, A.

2012-07-01

Carbon fibre reinforced silicon carbide (C/SiC) ceramic matrix composites (CMC) are most favourable for thermal protection systems & hot structures in re-entry vehicles since they offer superior heat resistance, high specific strength as well as a low coefficient of temperature expansion (CTE). To ensure the structural integrity of these C/SiC structures and thus mission safety all potential degradation effects during manufacturing and lifetime have to be considered. One of the most probable defects which may harm the structural integrity significantly can be caused by low-velocity impacts (LVI) which may occur during transportation and integration by e.g. dropping of tools. Thus the present study focuses on the residual mechanical and thermo-mechanical performance of C/SiC composites after being exposed to a low-velocity impact in terms of initial and residual mechanical performance, changes in microstructure, as well as thermo-mechanical performance through exposing specimens to multiple experimentally simulated re-entries. The results reveal the impact characteristics and damage mechanisms of C/SiC CMC exposed to a low-velocity impact and evidence the functional reliability as well as the damage tolerance of the C/SiC material investigated.

Fire-Retardant and Thermally Insulating Phenolic-Silica Aerogels.

PubMed

Yu, Zhi-Long; Yang, Ning; Apostolopoulou-Kalkavoura, Varvara; Qin, Bing; Ma, Zhi-Yuan; Xing, Wei-Yi; Qiao, Chan; Bergström, Lennart; Antonietti, Markus; Yu, Shu-Hong

2018-04-16

Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by their poor fire resistance and inorganic insulation materials are either brittle or display a high thermal conductivity. Herein we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Co-polymerization and nanoscale phase separation of the phenol-formaldehyde-resin (PFR) and silica generate a binary network with domain sizes below 20 nm. The PFR/SiO 2 aerogel can resist a high-temperature flame without disintegration and prevents the temperature on the non-exposed side from increasing above the temperature critical for the collapse of reinforced concrete structures. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of Nd3+ and Mn2+ ions Co-doped Spinal Strontium Nanoferrites for High Frequency Device Applications

NASA Astrophysics Data System (ADS)

Ahmad, Iqbal; Shah, Syed Mujtaba; Ashiq, Muhammad Naeem; Nawaz, Faisal; Shah, Afzal; Siddiq, Muhammad; Fahim, Iqra; Khan, Samiullah

2016-10-01

Microemulsion method has been used for the synthesis of high resistive spinal nanoferrites with nominal composition Sr1- x Nd x Fe2- y Mn y O4 (0.0 ≤ x ≤ 0.1, 0.0 ≤ y ≤ 1.0) for high frequency device applications. It has been confirmed by x-ray diffraction (XRD) results that these ferrites have a cubic spinal structure with a mean crystallite size ranging from 34 mm to 47 nm. The co-substitution of Nd3+ and Mn2+ ions was performed, and its effect on electrical, dielectric and impedance properties was analyzed employing direct current (DC) resistivity measurements, dielectric measurements and electrochemical impedance spectroscopy (EIS). The DC resistivity ( ρ) value was the highest for the composition Sr0.90Nd0.1FeMnO4, but for the same composition, dielectric parameters and alternating current (AC) conductivity showed their minimum values. In the lower frequency range, the magnitudes of dielectric parameters decrease with increasing frequency and show an almost independent frequency response at higher frequencies. Dielectric polarization has been employed to explain these results. It was inferred from the results of EIS that the conduction process in the studied ferrite materials is predominantly governed by grain boundary volume.

Comparison of Fecal Microbial Composition and Antibiotic Resistance Genes from Swine, Farm Workers and the Surrounding Villagers.

PubMed

Sun, Jian; Huang, Ting; Chen, Chong; Cao, Ting-Ting; Cheng, Ke; Liao, Xiao-Ping; Liu, Ya-Hong

2017-07-10

The external environment plays a critical role in shaping the structure of the gut microbiome. One potential health threat lies in the release of antibiotic resistant genes (ARGs) from cross-contaminated microbiomes. We focused this study on a comparison of fecal microbial composition and antibiotic resistant genes between farm workers, local villagers and swine. We used a high-throughput next-generation sequencing of 16S rRNA and real-time PCR for these studies. Our results indicated that workers had less species diversity as compared to the local villagers. Moreover, the bacterial communities of the farm workers, the local villagers and swine feces were clearly divided into three groups. The workers had a greater abundance of Proteobacteria as compared to swine and the local villagers. The Clostridiaceae in the workers and swine were more abundant than the local villagers. In addition, there were ARG differences between the farm workers or local villager's and swine feces. The farm workers and the local villagers had similar relative abundance except for macrolide ARGs. Taken together, these data suggest that the swine farm environment affects the fecal bacterial composition of swine farm workers. However, ARG spread was influenced by factors independent of the swine farm environment.

Methods for producing silicon carbide architectural preforms

NASA Technical Reports Server (NTRS)

DiCarlo, James A. (Inventor); Yun, Hee (Inventor)

2010-01-01

Methods are disclosed for producing architectural preforms and high-temperature composite structures containing high-strength ceramic fibers with reduced preforming stresses within each fiber, with an in-situ grown coating on each fiber surface, with reduced boron within the bulk of each fiber, and with improved tensile creep and rupture resistance properties for each fiber. The methods include the steps of preparing an original sample of a preform formed from a pre-selected high-strength silicon carbide ceramic fiber type, placing the original sample in a processing furnace under a pre-selected preforming stress state and thermally treating the sample in the processing furnace at a pre-selected processing temperature and hold time in a processing gas having a pre-selected composition, pressure, and flow rate. For the high-temperature composite structures, the method includes additional steps of depositing a thin interphase coating on the surface of each fiber and forming a ceramic or carbon-based matrix within the sample.

Temperature and composition phase diagram in the iron-based ladder compounds Ba 1 - x Cs x Fe 2 Se 3

DOE PAGES

Hawai, Takafumi; Nambu, Yusuke; Ohgushi, Kenya; ...

2015-05-28

We investigated the iron-based ladder compounds (Ba,Cs)Fe₂Se₃. Their parent compounds BaFe₂Se₃ and CsFe₂Se₃ have different space groups, formal valences of Fe, and magnetic structures. Electrical resistivity, specific heat, magnetic susceptibility, x-ray diffraction, and powder neutron diffraction measurements were conducted to obtain a temperature and composition phase diagram of this system. Block magnetism observed in BaFe₂Se₃ is drastically suppressed with Cs doping. In contrast, stripe magnetism observed in CsFe₂Se₃ is not so fragile against Ba doping. A new type of magnetic structure appears in intermediate compositions, which is similar to stripe magnetism of CsFe₂Se₃, but interladder spin configuration is different. Intermediatemore » compounds show insulating behavior, nevertheless a finite T-linear contribution in specific heat was obtained at low temperatures.« less