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Sample records for composition dependent structural

  1. Some Lower Valence Vanadium Fluorides: Their Crystal Distortions, Domain Structures, Modulated Structures, Ferrimagnetism, and Composition Dependence.

    ERIC Educational Resources Information Center

    Hong, Y. S.; And Others

    1980-01-01

    Describes some contemporary concepts unique to the structure of advanced solids, i.e., their crystal distortions, domain structures, modulated structures, ferrimagnetism, and composition dependence. (Author/CS)

  2. Nepheline structural and chemical dependence on melt composition

    SciTech Connect

    Marcial, José; Crum, Jarrod; Neill, Owen; McCloy, John

    2016-02-01

    Nepheline crystallizes upon slow-cooling in some melts concentrated in Na2O and Al2O3, which can result in a residual glass phase of low chemical durability. Nepheline can incorporate many components often found in high-level waste radioactive borosilicate glass, including glass network ions (e.g., Si, Al, Fe), alkali metals (e.g., Cs, K, Na, and possibly Li), alkaline-earth metals (e.g., Ba, Sr, Ca, Mg), and transition metals (e.g., Mn, and possibly Cr, Zn, Ni). When crystallized from melts of different compositions, nepheline chemistry varies as a function of starting glass composition. Five simulated high level nuclear waste borosilicate glasses shown to crystallize large fractions of nepheline on slow cooling, were selected for study. These melts constituted a range of Al2O3, B2O3, CaO, Na2O, K2O, Fe2O3, and SiO2 compositions. Compositional analyses of nepheline crystals in glass by electron probe micro-analysis (EPMA) indicate that boron is unlikely to be present in any significant concentration, if at all, in nepheline. Also, several models are presented for calculating the fraction of vacancies in the nepheline structure.

  3. Optical study on the dependence of breast tissue composition and structure on subject anamnesis

    NASA Astrophysics Data System (ADS)

    Taroni, Paola; Quarto, Giovanna; Pifferi, Antonio; Abbate, Francesca; Balestreri, Nicola; Menna, Simona; Cassano, Enrico; Cubeddu, Rinaldo

    2015-07-01

    Time domain multi-wavelength (635 to 1060 nm) optical mammography was performed on 200 subjects to estimate their average breast tissue composition in terms of oxy- and deoxy-hemoglobin, water, lipid and collagen, and structural information, as provided by scattering parameters (amplitude and power). Significant (and often marked) dependence of tissue composition and structure on age, menopausal status, body mass index, and use of oral contraceptives was demonstrated.

  4. Wood production response to climate change will depend critically on forest composition and structure.

    PubMed

    Coomes, David A; Flores, Olivier; Holdaway, Robert; Jucker, Tommaso; Lines, Emily R; Vanderwel, Mark C

    2014-12-01

    Established forests currently function as a major carbon sink, sequestering as woody biomass about 26% of global fossil fuel emissions. Whether forests continue to act as a global sink will depend on many factors, including the response of aboveground wood production (AWP; MgC ha(-1 ) yr(-1) ) to climate change. Here, we explore how AWP in New Zealand's natural forests is likely to change. We start by statistically modelling the present-day growth of 97 199 individual trees within 1070 permanently marked inventory plots as a function of tree size, competitive neighbourhood and climate. We then use these growth models to identify the factors that most influence present-day AWP and to predict responses to medium-term climate change under different assumptions. We find that if the composition and structure of New Zealand's forests were to remain unchanged over the next 30 years, then AWP would increase by 6-23%, primarily as a result of physiological responses to warmer temperatures (with no appreciable effect of changing rainfall). However, if warmth-requiring trees were able to migrate into currently cooler areas and if denser canopies were able to form, then a different AWP response is likely: forests growing in the cool mountain environments would show a 30% increase in AWP, while those in the lowland would hardly respond (on average, -3% when mean annual temperature exceeds 8.0 °C). We conclude that response of wood production to anthropogenic climate change is not only dependent on the physiological responses of individual trees, but is highly contingent on whether forests adjust in composition and structure.

  5. Composition-dependent structural changes and antitumor activity of ASC-DP/DSPE-PEG nanoparticles.

    PubMed

    Higashi, Kenjirou; Mibu, Fusako; Saito, Kengo; Limwikrant, Waree; Yamamoto, Keiji; Moribe, Kunikazu

    2017-03-01

    Ascorbyl 2,6-dipalmitate (ASC-DP) and distearoyl phosphatidylethanolamine polyethylene glycol 2000 (DSPE-PEG) formed stable nanoparticles at a molar ratio of less than or equal to 2:1 after dispersing the solvent-evaporated film in water. The mean particle sizes measured by dynamic light scattering were within the range of ca. 100-160nm. Composition-dependent changes of the ASC-DP and DSPE-PEG molecular states within the film were analyzed by wide-angle X-ray diffraction and infrared (IR) and solid-state nuclear magnetic resonance (NMR) spectroscopy. Transmission electron microscopy (TEM) of nanoparticles revealed that ASC-DP/DSPE-PEG changed from a micelle to a disk and tubular structure as the molar ratio increased. Quantitative solution-state (1)H NMR measurements elucidated the structure of nanoparticle in water; the core could be composed of ASC-DP and hydrophobic acyl chains of DSPE, whereas the hydrophilic PEG chains of DSPE-PEG on the surface form the hydration shell to stabilize the nanoparticle dispersion in water. Cytotoxicity of ASC-DP against cancer cell lines was observed by using ASC-DP/DSPE-PEG nanoparticles, and no cytotoxicity against normal cells was found. Thus, the ASC-DP/DSPE-PEG formulation, with tumor cell specific cytotoxicity, can be applicable for cancer monotherapy or in combination with other anticancer drugs.

  6. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaffin, Elise; O'Connor, Ryan T.; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ˜410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods.

  7. Protein packing: dependence on protein size, secondary structure and amino acid composition.

    PubMed

    Fleming, P J; Richards, F M

    2000-06-02

    We have used the occluded surface algorithm to estimate the packing of both buried and exposed amino acid residues in protein structures. This method works equally well for buried residues and solvent-exposed residues in contrast to the commonly used Voronoi method that works directly only on buried residues. The atomic packing of individual globular proteins may vary significantly from the average packing of a large data set of globular proteins. Here, we demonstrate that these variations in protein packing are due to a complex combination of protein size, secondary structure composition and amino acid composition. Differences in protein packing are conserved in protein families of similar structure despite significant sequence differences. This conclusion indicates that quality assessments of packing in protein structures should include a consideration of various parameters including the packing of known homologous proteins. Also, modeling of protein structures based on homologous templates should take into account the packing of the template protein structure.

  8. Protein-nanoparticle interactions: the effects of surface compositional and structural heterogeneity are scale dependent

    NASA Astrophysics Data System (ADS)

    Huang, Rixiang; Carney, Randy P.; Stellacci, Francesco; Lau, Boris L. T.

    2013-07-01

    Nanoparticles (NPs) in the biological environment are exposed to a large variety and concentration of proteins. Proteins are known to adsorb in a `corona' like structure on the surface of NPs. In this study, we focus on the effects of surface compositional and structural heterogeneity on protein adsorption by examining the interaction of self-assembled monolayer coated gold NPs (AuNPs) with two types of proteins: ubiquitin and fibrinogen. This work was designed to systematically investigate the role of surface heterogeneity in nanoparticle-protein interaction. We have chosen the particles as well as the proteins to provide different types (in distribution and length-scale) of heterogeneity. The goal was to unveil the role of heterogeneity and of its length-scale in the particle-protein interaction. Dynamic light scattering and circular dichroism spectroscopy were used to reveal different interactions at pH above and below the isoelectric points of the proteins, which is related to the charge heterogeneity on the protein surface. At pH 7.4, there was only a monolayer of proteins adsorbed onto the NPs and the secondary structure of proteins remained intact. At pH 4.0, large aggregates of nanoparticle-protein complexes were formed and the secondary structures of the proteins were significantly disrupted. In terms of interaction thermodynamics, results from isothermal titration calorimetry showed that ubiquitin adsorbed differently onto (1) AuNPs with charged and nonpolar terminals organized into nano-scale structure (66-34 OT), (2) AuNPs with randomly distributed terminals (66-34 brOT), and (3) AuNPs with homogeneously charged terminals (MUS). This difference in adsorption behavior was not observed when AuNPs interacted with fibrinogen. The results suggested that the interaction between the proteins and AuNPs was influenced by the surface heterogeneity on the AuNPs, and this influence depends on the scale of surface heterogeneity and the size of the proteins

  9. Composition dependent structural organization in trihexyl(tetradecyl)phosphonium chloride ionic liquid-methanol mixtures

    SciTech Connect

    Gupta, Aditya; Sharma, Shobha; Kashyap, Hemant K.

    2015-04-07

    This article reports results from the molecular dynamics simulations on the structural arrangement of the ions and molecules in the mixtures of trihexyl(tetradecyl)phosphonium chloride ([P{sub 666,14}{sup +}][Cl{sup −}]) ionic liquid (IL) and methanol (MeOH) over the entire composition range. Effects of composition on the charge and polarity orderings have been investigated via computation of X-ray scattering structure function, S(q), and by using a partitioning scheme proposed for such multi-component mixtures. Except for the neat methanol liquid, the total S(q) shows two peaks in its intermolecular region for all the mole-fractions. The lowest q peak is dominated primarily by anion-anion, cation-anion, and methanol-anion correlations. Our results signify that the methanol bulk structure, which predominantly has short-distance characteristic correlations and is governed by polar group of methanol, is retained for x{sub IL} ≤ 0.1. Then, the mixture goes through gradual structural changes from methanol-like to the IL-like for 0.1 < x{sub IL} ≤ 0.7. The dipolar interaction between methanol molecules weakens in this range, and the structural landscape of the mixture is steered by strong ion-ion, anion-methanol, and nonpolar interactions. The IL-like structural arrangement is virtually recovered for x{sub IL} > 0.7. At all the compositions studied, while the cation head groups are predominantly solvated by anions and subsequently by methanol molecules, the polar hydroxyl group of methanol is preferentially solvated by the anions. The radial distribution functions of selected pair of atomic species have also confirmed these observations.

  10. Finite temperature performance of hard-soft composite nanomagnets and its dependence on geometry structure of composites

    NASA Astrophysics Data System (ADS)

    Belemuk, A. M.; Chui, S. T.

    2013-01-01

    We study with finite temperature Monte Carlo simulation under periodic boundary conditions remanence, coercivity, and energy product behavior of exchanged-coupled hard and soft alternating layers. We compare multilayer properties with that of a composite composed of cube inclusions of hard phase embedded into a soft matrix. The easy axis of the hard (SmCo5) and soft (FeCo) phases is parallel to the layers and the applied magnetic field. We find a significant increase of the energy product for the multilayer structure as compared with that of the cube structure. In the former case, the switching occurs as a result of a two-step demagnetization process, realizing the concept of exchange-spring behavior, when first the soft layers gradually rotate to the direction of applied field, and then the hard phase layers rotate. In the latter case, we find a significant lowering of the remanent magnetization with increasing soft magnet content than anticipated. This is due to the boundary mismatch of magnetization on the hard/soft interface. We investigate this mismatch as a function of the soft phase content and temperature. The boundary mismatch significantly affects the finite temperature energy product of composites.

  11. A Contribution to Time-Dependent Damage Modeling of Composite Structures

    NASA Astrophysics Data System (ADS)

    Treasurer, Paul; Poirette, Yann; Perreux, Dominique; Thiebaud, Frédéric

    2014-08-01

    The paper presents a new damage model for predicting stiffness loss due to creep loading and cyclic fatigue. The model, developed within a continuum damage mechanics framework, is based on the idea of a time-dependent damage spectrum, some elements of which occur rapidly and others slowly. The use of this spectrum allows a single damage kinematic to model creep and fatigue damage and to take into account the effect of stress amplitude, R ratio, and frequency. The evolution equations are based on similar equation than the one describing the viscoelasticity model and are relatively easy to implement. The new model is compared to the experimental results on carbon fiber/epoxy tubes. Quasi-static, creep and fatigue tests are performed on filament-wound tubular specimens to characterize the elastic, viscoelastic and plastic behavior of the composite material. Varying amounts of damage are observed and discussed depending on stress level and R ratio. The experimental work aims to develop and validate the damage model for predicting stiffness loss due to creep loading and cyclic fatigue.

  12. Structural state scale-dependent physical characteristics and endurance of cermet composite for cutting metal

    SciTech Connect

    Ovcharenko, V. E.; Ivanov, Yu. F.; Mohovikov, A. A.; Baohai, Yu E-mail: yanhui.yhzhao@imr.ac.cn; Zhao, Yanhui E-mail: yanhui.yhzhao@imr.ac.cn

    2014-11-14

    A structural-phase state developed on the surface of a TiC/Ni–Cr–Al cermet alloy under superfast heating and cooling produced by pulse electron beam melting has been presented. The effect of the surface’s structural state multimodality on the temperature dependencies of the friction and endurance of the cermet tool in cutting metal has been investigated. The high-energy flux treatment of subsurface layers by electron beam pulses in argon-containing gas discharge plasma serves to improve the endurance of metal cutting tools manifold (by a factor of 6), to reduce the friction via precipitation of secondary 200 nm carbides in binder interlayers. It is possible to improve the cermet tool endurance for cutting metal by a factor of 10–12 by irradiating the cermet in a reactive nitrogen-containing atmosphere with the ensuing precipitation of nanosize 50 nm AlN particles in the binder interlayers.

  13. Composition dependent intrinsic defect structures in SrTiO3

    SciTech Connect

    Liu, Bin; Cooper, Valentino R; Xu, Haixuan; Xiao, Haiyan; Zhang, Yanwen; Weber, William J

    2014-01-01

    Intrinsic point defect complexes in SrTiO3 under different chemical conditions are studied using density functional theory. The Schottky defect complex consisting of nominally charged Sr, Ti and O vacancies is predicted to be the most stable defect structure in stoichiometric SrTiO3, with a relatively low formation energy of 1.64 eV/defect. In addition, the mechanisms of defect complex formation in nonstoichiometric SrTiO3 are investigated. Excess SrO leads to the formation of the oxygen vacancies and a strontium-titanium antisite defect, while a strontium vacancy together with an oxygen vacancy and the titanium-strontium antisite defect are produced in an excess TiO2 environment. Since point defects, such as oxygen vacancies and cation antisite defects, are intimately related to the functionality of SrTiO3, these results provide guidelines for controlling the formation of intrinsic point defects and optimizing the functionality of SrTiO3 by controlling nonstoichiometric chemical compositions of SrO and TiO2 in experiments.

  14. Probing the Crystal Structure, Composition-Dependent Absolute Energy Levels, and Electrocatalytic Properties of Silver Indium Sulfide Nanostructures.

    PubMed

    Saji, Pintu; Ganguli, Ashok K; Bhat, Mohsin A; Ingole, Pravin P

    2016-04-18

    The absolute electronic energy levels in silver indium sulfide (AIS) nanocrystals (NCs) with varying compositions and crystallographic phases have been determined by using cyclic voltammetry. Different crystallographic phases, that is, metastable cubic, orthorhombic, monoclinic, and a mixture of cubic and orthorhombic AIS NCs, were studied. The band gap values estimated from the cyclic voltammetry measurements match well with the band gap values calculated from the diffuse reflectance spectra measurements. The AIS nanostructures were found to show good electrocatalytic activity towards the hydrogen evolution reaction (HER). Our results clearly establish that the electronic and electrocatalytic properties of AIS NCs are strongly sensitive to the composition and crystal structure of AIS NCs. Monoclinic AIS was found to be the most active HER electrocatalyst, with electrocatalytic activity that is almost comparable to the MoS2 -based nanostructures reported in the literature, whereas cubic AIS was observed to be the least active of the studied crystallographic phases and compositions. In view of the HER activity and electronic band structure parameters observed herein, we hypothesize that the Fermi energy level of AIS NCs is an important factor that decides the electrocatalytic efficiency of these nanocomposites. The work presented herein, in addition to being the first of its kind regarding the composition and phase-dependence of electrochemical aspects of AIS NCs, also presents a simple solvothermal method for the synthesis of different crystallographic phases with various Ag/In molar ratios.

  15. A probe into compositional and structural dependence of optical properties of lanthanum fluoride films prepared by resistive heating

    NASA Astrophysics Data System (ADS)

    Rao, Pritty; Kumar, Sanjiv; Tokas, R. B.; Sahoo, N. K.

    2015-01-01

    The paper describes investigations into the correlation between the optical properties and the composition, structure and morphology of lanthanum fluoride films deposited at 373-473 K substrate temperatures by resistive heating of lanthanum fluoride powders. The composition of the films that includes depth profiling of fluorine has been determined non-destructively by ion beam analysis while their structure and morphology have been investigated by glancing incidence X-ray diffraction and atomic force microscopy respectively. The films are polycrystalline, exist in hexagonal phase and display substrate temperature dependent texturing. The substrate temperature has an important influence on composition as well. The films deposited at 373 K or 398 K substrate temperatures are deficient in fluorine but tend to acquire stoichiometric composition at 473 K. Possessing granular (∼100 nm) morphology, the films, in general, are UV transparent but their optical loss increases with texturing. Carbon and oxygen, present as impurities, lower the density and consequently the refractive index (1.47) of the films. Annealing in vacuum at 573 K brings about deterioration in the optical properties of the films which are related mainly to morphological changes and thermal stress.

  16. Composition dependent multiple structural transformations of myoglobin in aqueous ethanol solution: A combined experimental and theoretical study

    SciTech Connect

    Ghosh, R.; Samajdar, R. N.; Bhattacharyya, Aninda Jiban; Bagchi, B.

    2015-07-07

    Experimental studies (circular dichroism and ultra-violet (UV) absorption spectra) and large scale atomistic molecular dynamics simulations (accompanied by order parameter analyses) are combined to establish a number of remarkable (and unforeseen) structural transformations of protein myoglobin in aqueous ethanol mixture at various ethanol concentrations. The following results are particularly striking. (1) Two well-defined structural regimes, one at x{sub EtOH} ∼ 0.05 and the other at x{sub EtOH} ∼ 0.25, characterized by formation of distinct partially folded conformations and separated by a unique partially unfolded intermediate state at x{sub EtOH} ∼ 0.15, are identified. (2) Existence of non-monotonic composition dependence of (i) radius of gyration, (ii) long range contact order, (iii) residue specific solvent accessible surface area of tryptophan, and (iv) circular dichroism spectra and UV-absorption peaks are observed. Interestingly at x{sub EtOH} ∼ 0.15, time averaged value of the contact order parameter of the protein reaches a minimum, implying that this conformational state can be identified as a molten globule state. Multiple structural transformations well known in water-ethanol binary mixture appear to have considerably stronger effects on conformation and dynamics of the protein. We compare the present results with studies in water-dimethyl sulfoxide mixture where also distinct structural transformations are observed along with variation of co-solvent composition.

  17. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R. G.; Wiberley, S. E.

    1985-01-01

    Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

  18. Composite structural materials. [aircraft structures

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1980-01-01

    The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

  19. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1979-01-01

    A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

  20. ACEE composite structures technology

    NASA Technical Reports Server (NTRS)

    Klotzsche, M. (Compiler)

    1984-01-01

    The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program has made significant progress in the development of technology for advanced composites in commercial aircraft. Commercial airframe manufacturers have demonstrated technology readiness and cost effectiveness of advanced composites for secondary and medium primary components and have initiated a concerted program to develop the data base required for efficient application to safety-of-flight wing and fuselage structures. Oral presentations were compiled into five papers. Topics addressed include: damage tolerance and failsafe testing of composite vertical stabilizer; optimization of composite multi-row bolted joints; large wing joint demonstation components; and joints and cutouts in fuselage structure.

  1. Optimization of composite structures

    NASA Technical Reports Server (NTRS)

    Stroud, W. J.

    1982-01-01

    Structural optimization is introduced and examples which illustrate potential problems associated with optimized structures are presented. Optimized structures may have very low load carrying ability for an off design condition. They tend to have multiple modes of failure occurring simultaneously and can, therefore, be sensitive to imperfections. Because composite materials provide more design variables than do metals, they allow for more refined tailoring and more extensive optimization. As a result, optimized composite structures can be especially susceptible to these problems.

  2. Process-Parameter-Dependent Optical and Structural Properties of ZrO2MgO Mixed-Composite Films Evaporated from the solid Solution

    NASA Technical Reports Server (NTRS)

    Sahoo, N. K.; Shapiro, A. P.

    1998-01-01

    The process-parameter-dependent optical and structural properties of ZrO2MgO mixed-composite material have been investigated. Optical properties were derived from spectrophotometric measurements. By use of atomic force microscopy, x-ray diffraction analysis, and energy-dispersive x-ray (EDX) analysis, the surface morphology, grain size distributions, crystallographic phases, and process-dependent material composition of films have been investigated. EDX analysis made evident the correlation between the oxygen enrichment in the films prepared at a high level of oxygen pressure and the very low refractive index. Since oxygen pressure can be dynamically varied during a deposition process, coatings constructed of suitable mixed-composite thin films can benefit from continuous modulation of the index of refraction. A step modulation approach is used to develop various multilayer-equivalent thin-film devices.

  3. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1987-01-01

    The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

  4. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1984-01-01

    Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

  5. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1981-01-01

    The composite aircraft program component (CAPCOMP) is a graduate level project conducted in parallel with a composite structures program. The composite aircraft program glider (CAPGLIDE) is an undergraduate demonstration project which has as its objectives the design, fabrication, and testing of a foot launched ultralight glider using composite structures. The objective of the computer aided design (COMPAD) portion of the composites project is to provide computer tools for the analysis and design of composite structures. The major thrust of COMPAD is in the finite element area with effort directed at implementing finite element analysis capabilities and developing interactive graphics preprocessing and postprocessing capabilities. The criteria for selecting research projects to be conducted under the innovative and supporting research (INSURE) program are described.

  6. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R.; Wiberley, S. E.

    1986-01-01

    Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

  7. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1988-01-01

    A decade long program to develop critical advanced composite technology in the areas of physical properties, structural concept and analysis, manufacturing, reliability, and life predictions is reviewed. Specific goals are discussed. The status of the chemical vapor deposition effects on carbon fiber properties; inelastic deformation of metal matrix laminates; fatigue damage in fibrous MMC laminates; delamination fracture toughness in thermoplastic matrix composites; and numerical analysis of composite micromechanical behavior are presented.

  8. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

  9. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Wiberley, S. E.

    1978-01-01

    The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

  10. ACEE composite structures technology

    NASA Technical Reports Server (NTRS)

    James, A. M.

    1984-01-01

    Topics addressed include: strength and hygrothermal response of L-1011 fin components; wing fuel containment and damage tolerance development; impact dynamics; acoustic transmission; fuselage structure; composite transport wing technology development; spar/assembly concepts.

  11. Size-confined fixed-composition and composition-dependent engineered band gap alloying induces different internal structures in L-cysteine-capped alloyed quaternary CdZnTeS quantum dots

    NASA Astrophysics Data System (ADS)

    Adegoke, Oluwasesan; Park, Enoch Y.

    2016-06-01

    The development of alloyed quantum dot (QD) nanocrystals with attractive optical properties for a wide array of chemical and biological applications is a growing research field. In this work, size-tunable engineered band gap composition-dependent alloying and fixed-composition alloying were employed to fabricate new L-cysteine-capped alloyed quaternary CdZnTeS QDs exhibiting different internal structures. Lattice parameters simulated based on powder X-ray diffraction (PXRD) revealed the internal structure of the composition-dependent alloyed CdxZnyTeS QDs to have a gradient nature, whereas the fixed-composition alloyed QDs exhibited a homogenous internal structure. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis confirmed the size-confined nature and monodispersity of the alloyed nanocrystals. The zeta potential values were within the accepted range of colloidal stability. Circular dichroism (CD) analysis showed that the surface-capped L-cysteine ligand induced electronic and conformational chiroptical changes in the alloyed nanocrystals. The photoluminescence (PL) quantum yield (QY) values of the gradient alloyed QDs were 27–61%, whereas for the homogenous alloyed QDs, the PL QY values were spectacularly high (72–93%). Our work demonstrates that engineered fixed alloying produces homogenous QD nanocrystals with higher PL QY than composition-dependent alloying.

  12. Composite foam structures

    NASA Technical Reports Server (NTRS)

    Williams, Brian E. (Inventor); Brockmeyer, Jerry (Inventor); Tuffias, Robert H. (Inventor)

    2005-01-01

    A composite rigid foam structure that has a skin or coating on at least one of its surfaces. The skin is formed in situ by thermal spray techniques. The skin is bonded substantially throughout the surface of the porous substrate to the peripheries of the pores. The skin on the average does not penetrate the surface of the substrate by more than the depth of about 2 to 5 pores. Thus, thermal spraying the skin onto the rigid foam produces a composite that is tightly and uniformly bonded together without unduly increasing the weight of the composite structure. Both thermal conductivity and bonding are excellent.

  13. Lightweight Composite Intertank Structure

    NASA Technical Reports Server (NTRS)

    Mehle, Greg V.

    1995-01-01

    Report presents results of study for proposed lightweight composite material alternative to present semimonocoque aluminum intertank structure for advanced launch vehicles. Proposed structure integrated assembly of sandwich panels made of laminated epoxy-matrix/carbon-fiber skins, and aluminum honeycomb core.

  14. Structural anomaly and dynamic heterogeneity in cycloether/water binary mixtures: Signatures from composition dependent dynamic fluorescence measurements and computer simulations

    NASA Astrophysics Data System (ADS)

    Indra, Sandipa; Guchhait, Biswajit; Biswas, Ranjit

    2016-03-01

    We have performed steady state UV-visible absorption and time-resolved fluorescence measurements and computer simulations to explore the cosolvent mole fraction induced changes in structural and dynamical properties of water/dioxane (Diox) and water/tetrahydrofuran (THF) binary mixtures. Diox is a quadrupolar solvent whereas THF is a dipolar one although both are cyclic molecules and represent cycloethers. The focus here is on whether these cycloethers can induce stiffening and transition of water H-bond network structure and, if they do, whether such structural modification differentiates the chemical nature (dipolar or quadrupolar) of the cosolvent molecules. Composition dependent measured fluorescence lifetimes and rotation times of a dissolved dipolar solute (Coumarin 153, C153) suggest cycloether mole-fraction (XTHF/Diox) induced structural transition for both of these aqueous binary mixtures in the 0.1 ≤ XTHF/Diox ≤ 0.2 regime with no specific dependence on the chemical nature. Interestingly, absorption measurements reveal stiffening of water H-bond structure in the presence of both the cycloethers at a nearly equal mole-fraction, XTHF/Diox ˜ 0.05. Measurements near the critical solution temperature or concentration indicate no role for the solution criticality on the anomalous structural changes. Evidences for cycloether aggregation at very dilute concentrations have been found. Simulated radial distribution functions reflect abrupt changes in respective peak heights at those mixture compositions around which fluorescence measurements revealed structural transition. Simulated water coordination numbers (for a dissolved C153) and number of H-bonds also exhibit minima around these cosolvent concentrations. In addition, several dynamic heterogeneity parameters have been simulated for both the mixtures to explore the effects of structural transition and chemical nature of cosolvent on heterogeneous dynamics of these systems. Simulated four-point dynamic

  15. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been achieved since the initial developments in the mid 1960's. Rather limited applications to primary aircraft structure have been made, however, mainly in a material-substitution mode on military aircraft, except for a few experiments currently underway on large passenger airplanes in commercial operation. To fulfill the promise of composite materials completely requires a strong technology base. NASA and AFOSR recognize the present state of the art to be such that to fully exploit composites in sophisticated aerospace structures, the technology base must be improved. This, in turn, calls for expanding fundamental knowledge and the means by which it can be successfully applied in design and manufacture.

  16. Composite Structural Materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

    1984-01-01

    The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

  17. Multifunctional Composite Structures

    DTIC Science & Technology

    2010-03-01

    especially  for  composites  that  have  thermoplastic  polymer   matrix .  Experimental  evidence  suggests  that  electric  currents  passing  through...Overview Polymer   matrix  composites are widely used as a structural material in a variety of  aerospace  applications  including  commercials  jets...Chung, D. D. L., 2000, "Piezoresistivity in continuous carbon fiber polymer - matrix and cement- matrix composites," Journal of Materials Science, 35

  18. Composition dependent structural and optical properties of PbF₂-TeO₂-B₂O₃-Eu₂O₃ glasses.

    PubMed

    Wagh, Akshatha; Raviprakash, Y; Upadhyaya, Vyasa; Kamath, Sudha D

    2015-12-05

    Boric oxide based quaternary glasses in the system PbF2-TeO2-B2O3-Eu2O3 have been prepared by melt quenching technique. Density, molar volume, FTIR, UV-Vis techniques were used to probe the structural modifications with incorporation of europium ions in the glass network. An increase in glass density & decrease in molar volume (Vm) values proved the structural changes occurring in coordination of boron atom [conversion of BO3 units to BO4]. This resulted in the increase of the compaction of the prepared glasses with increase in Eu2O3 contents. The amorphous natures of the samples were ascertained by XRD and metallization criterion (M) studies. XPS study showed the values of core-level binding energy [O1s, Eu3d, Eu4d, Te3d, Te4d, Pd4f, Pb5d, O1s, and F1s] of (PbF2-TeO2-B2O3-Eu2O3) the glass matrix. The frequency and temperature dependence of dielectric properties of present glasses were investigated in the frequency range of 1 Hz-10 MHz and temperature range of 313-773K. The study of dielectric measurements proved good insulating and thermal stability of the prepared glasses. At room temperature, dielectric loss [tanδ] values were negligibly small for prepared glasses and increased with increase in temperature. FTIR spectroscopy results were in good agreement with optical band energy gap, density, molar volume and hardness values revealing network modifications caused by europium ions in the glass structure.

  19. Repairs of composite structures

    NASA Astrophysics Data System (ADS)

    Roh, Hee Seok

    Repair on damaged composite panels was conducted. To better understand adhesively bonded repair, the study investigates the effect of design parameters on the joint strength. The design parameters include bondline length, thickness of adherend and type of adhesive. Adhesives considered in this study were tested to measure their tensile material properties. Three types of adhesively bonded joints, single strap, double strap, and single lap joint were considered under changing bondline lengths, thickness of adherend and type of adhesive. Based on lessons learned from bonded joints, a one-sided patch repair method for composite structures was conducted. The composite patch was bonded to the damaged panel by either film adhesive FM-73M or paste adhesive EA-9394 and the residual strengths of the repaired specimens were compared under varying patch sizes. A new repair method using attachments has been suggested to enhance the residual strength. Results obtained through experiments were analyzed using finite element analysis to provide a better repair design and explain the experimental results. It was observed that the residual strength of the repaired specimen was affected by patch length. Method for rapid repairs of damaged composite structures was investigated. The damage was represented by a circular hole in a composite laminated plate. Pre-cured composite patches were bonded with a quick-curing commercial adhesive near (rather than over) the hole. Tensile tests were conducted on specimens repaired with various patch geometries. The test results showed that, among the methods investigated, the best repair method restored over 90% of the original strength of an undamaged panel. The interfacial stresses in the adhesive zone for different patches were calculated in order to understand the efficiencies of the designs of these patch repairs. It was found that the composite patch that yielded the best strength had the lowest interfacial peel stress between the patch and

  20. Composite mechanics for engine structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    1989-01-01

    Recent research activities and accomplishments at Lewis Research Center on composite mechanics for engine structures are summarized. The activities focused mainly on developing procedures for the computational simulation of composite intrinsic and structural behavior. The computational simulation encompasses all aspects of composite mechanics, advanced three-dimensional finite-element methods, damage tolerance, composite structural and dynamic response, and structural tailoring and optimization.

  1. Composite mechanics for engine structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    1987-01-01

    Recent research activities and accomplishments at Lewis Research Center on composite mechanics for engine structures are summarized. The activities focused mainly on developing procedures for the computational simulation of composite intrinsic and structural behavior. The computational simulation encompasses all aspects of composite mechanics, advanced three-dimensional finite-element methods, damage tolerance, composite structural and dynamic response, and structural tailoring and optimization.

  2. Hybrid composite laminate structures

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F. (Inventor)

    1977-01-01

    An invention which relates to laminate structures and specifically to essentially anisotropic fiber composite laminates is described. Metal foils are selectively disposed within the laminate to produce increased resistance to high velocity impact, fracture, surface erosion, and other stresses within the laminate.

  3. Composition and temperature dependent electronic structures of NiS2 -xSex alloys: First-principles dynamical mean-field theory approach

    NASA Astrophysics Data System (ADS)

    Moon, Chang-Youn; Kang, Hanhim; Jang, Bo Gyu; Shim, Ji Hoon

    2015-12-01

    We investigate the evolution of the electronic structure of NiS2 -xSex alloys with varying temperature and composition x by using the combined approach of density-functional theory and dynamical mean-field theory. Adopting realistic alloy structures containing S and Se dimers, we map their electronic correlation strength on the phase diagram and observe the metal-insulator transition (MIT) at the composition x =0.5 , which is consistent with the experimental measurements. The temperature dependence of the local magnetic susceptibility is found to show a typical Curie-Weiss-like behavior in the insulating phase while it shows a constant Pauli-like behavior in the metallic phase. A comparison of the electronic structures for NiS2 and NiSe2 in different lattice structures suggests that the MIT in this alloy system can be classified as of bandwidth-control type, where the change in the hybridization strength between Ni d and chalcogen p orbitals is the most important parameter.

  4. Unibody Composite Pressurized Structure

    NASA Technical Reports Server (NTRS)

    Rufer, Markus; Conger, Robert; Bauer, Thomas; Newman, John

    2013-01-01

    An integrated, generic unibody composite pressurized structure (UCPS) combined with a positive expulsion device (PED), consisting of an elastomeric bladder for monopropellant hydrazine, has been quasi-standardized for spacecraft use. The combination functions as an all-composite, non-metallic, propellant tank with bladder. The integrated UCPS combines several previous innovations - specifically, the linerless, all-composite cryogenic tank technology; all-composite boss; resin formulation; and integrated stringer system. The innovation combines the UCPS with an integrated propellant management device (PMD), the PED or bladder, to create an entirely unique system for in-space use. The UCPS is a pressure vessel that incorporates skirts, stringers, and other structures so that it is both an in-space hydrazine tank, and also a structural support system for a spacecraft in a single, all-composite unit. This innovation builds on the progress in the development of a previous SBIR (Small Business Innovation Research) Phase I with Glenn Research Center and an SBIR III with Johnson Space Center that included the fabrication of two 42-in. (˜107-cm) diameter all-composite cryogenic (LOX and liquid methane) UCPS test tanks for a lunar lander. This Phase II provides hydra zine compatibility testing of the elastomeric bladder, a see-through PED to validate the expulsion process and model, and a complete UCPS-based PED with stringers and skirts that will be used to conduct initial qualification and expulsion tests. This extends the UCPS technology to include hydrazine-based, in-space pro - pulsion applications and can also be used for electric propulsion. This innovation creates a system that, in comparison to the traditional approach, is lower in weight, cost, volume, and production time; is stronger; and is capable of much higher pressures. It also has fewer failure modes, and is applicable to both chemical and electric propulsion systems.

  5. Structural and compositional dependence of the CdTexSe1-x alloy layer photoactivity in CdTe-based solar cells

    DOE PAGES

    Poplawsky, Jonathan D.; Guo, Wei; Paudel, Naba; ...

    2016-07-27

    The published external quantum efficiency data of the world-record CdTe solar cell suggests that the device uses bandgap engineering, most likely with a CdTexSe1₋x alloy layer to increase the short-circuit current and overall device efficiency. Here atom probe tomography, transmission electron microscopy and electron beam-induced current are used to clarify the dependence of Se content on the photoactive properties of CdTexSe1₋x alloy layers in bandgap-graded CdTe solar cells. Four solar cells were prepared with 50, 100, 200 and 400 nm-thick CdSe layers to reveal the formation, growth, composition, structure and photoactivity of the CdTexSe1₋x alloy with respect to the degreemore » of Se diffusion. Finally, the results show that the CdTexSe1₋x layer photoactivity is highly dependent on the crystalline structure of the alloy (zincblende versus wurtzite), which is also dependent on the Se and Te concentrations.« less

  6. Structural and compositional dependence of the CdTexSe1−x alloy layer photoactivity in CdTe-based solar cells

    PubMed Central

    Poplawsky, Jonathan D.; Guo, Wei; Paudel, Naba; Ng, Amy; More, Karren; Leonard, Donovan; Yan, Yanfa

    2016-01-01

    The published external quantum efficiency data of the world-record CdTe solar cell suggests that the device uses bandgap engineering, most likely with a CdTexSe1−x alloy layer to increase the short-circuit current and overall device efficiency. Here atom probe tomography, transmission electron microscopy and electron beam-induced current are used to clarify the dependence of Se content on the photoactive properties of CdTexSe1−x alloy layers in bandgap-graded CdTe solar cells. Four solar cells were prepared with 50, 100, 200 and 400 nm-thick CdSe layers to reveal the formation, growth, composition, structure and photoactivity of the CdTexSe1−x alloy with respect to the degree of Se diffusion. The results show that the CdTexSe1−x layer photoactivity is highly dependent on the crystalline structure of the alloy (zincblende versus wurtzite), which is also dependent on the Se and Te concentrations. PMID:27460872

  7. Structural and compositional dependence of the CdTexSe1-x alloy layer photoactivity in CdTe-based solar cells

    SciTech Connect

    Poplawsky, Jonathan D.; Guo, Wei; Paudel, Naba; Ng, Amy; More, Karren; Leonard, Donovan; Yan, Yanfa

    2016-07-27

    The published external quantum efficiency data of the world-record CdTe solar cell suggests that the device uses bandgap engineering, most likely with a CdTexSe1₋x alloy layer to increase the short-circuit current and overall device efficiency. Here atom probe tomography, transmission electron microscopy and electron beam-induced current are used to clarify the dependence of Se content on the photoactive properties of CdTexSe1₋x alloy layers in bandgap-graded CdTe solar cells. Four solar cells were prepared with 50, 100, 200 and 400 nm-thick CdSe layers to reveal the formation, growth, composition, structure and photoactivity of the CdTexSe1₋x alloy with respect to the degree of Se diffusion. Finally, the results show that the CdTexSe1₋x layer photoactivity is highly dependent on the crystalline structure of the alloy (zincblende versus wurtzite), which is also dependent on the Se and Te concentrations.

  8. Deployable Soft Composite Structures

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Rodrigue, Hugo; Ahn, Sung-Hoon

    2016-02-01

    Deployable structure composed of smart materials based actuators can reconcile its inherently conflicting requirements of low mass, good shape adaptability, and high load-bearing capability. This work describes the fabrication of deployable structures using smart soft composite actuators combining a soft matrix with variable stiffness properties and hinge-like movement through a rigid skeleton. The hinge actuator has the advantage of being simple to fabricate, inexpensive, lightweight and simple to actuate. This basic actuator can then be used to form modules capable of different types of deformations, which can then be assembled into deployable structures. The design of deployable structures is based on three principles: design of basic hinge actuators, assembly of modules and assembly of modules into large-scale deployable structures. Various deployable structures such as a segmented triangular mast, a planar structure comprised of single-loop hexagonal modules and a ring structure comprised of single-loop quadrilateral modules were designed and fabricated to verify this approach. Finally, a prototype for a deployable mirror was developed by attaching a foldable reflective membrane to the designed ring structure and its functionality was tested by using it to reflect sunlight onto to a small-scale solar panel.

  9. Deployable Soft Composite Structures

    PubMed Central

    Wang, Wei; Rodrigue, Hugo; Ahn, Sung-Hoon

    2016-01-01

    Deployable structure composed of smart materials based actuators can reconcile its inherently conflicting requirements of low mass, good shape adaptability, and high load-bearing capability. This work describes the fabrication of deployable structures using smart soft composite actuators combining a soft matrix with variable stiffness properties and hinge-like movement through a rigid skeleton. The hinge actuator has the advantage of being simple to fabricate, inexpensive, lightweight and simple to actuate. This basic actuator can then be used to form modules capable of different types of deformations, which can then be assembled into deployable structures. The design of deployable structures is based on three principles: design of basic hinge actuators, assembly of modules and assembly of modules into large-scale deployable structures. Various deployable structures such as a segmented triangular mast, a planar structure comprised of single-loop hexagonal modules and a ring structure comprised of single-loop quadrilateral modules were designed and fabricated to verify this approach. Finally, a prototype for a deployable mirror was developed by attaching a foldable reflective membrane to the designed ring structure and its functionality was tested by using it to reflect sunlight onto to a small-scale solar panel. PMID:26892762

  10. Deployable Soft Composite Structures.

    PubMed

    Wang, Wei; Rodrigue, Hugo; Ahn, Sung-Hoon

    2016-02-19

    Deployable structure composed of smart materials based actuators can reconcile its inherently conflicting requirements of low mass, good shape adaptability, and high load-bearing capability. This work describes the fabrication of deployable structures using smart soft composite actuators combining a soft matrix with variable stiffness properties and hinge-like movement through a rigid skeleton. The hinge actuator has the advantage of being simple to fabricate, inexpensive, lightweight and simple to actuate. This basic actuator can then be used to form modules capable of different types of deformations, which can then be assembled into deployable structures. The design of deployable structures is based on three principles: design of basic hinge actuators, assembly of modules and assembly of modules into large-scale deployable structures. Various deployable structures such as a segmented triangular mast, a planar structure comprised of single-loop hexagonal modules and a ring structure comprised of single-loop quadrilateral modules were designed and fabricated to verify this approach. Finally, a prototype for a deployable mirror was developed by attaching a foldable reflective membrane to the designed ring structure and its functionality was tested by using it to reflect sunlight onto to a small-scale solar panel.

  11. Honeycomb-laminate composite structure

    NASA Technical Reports Server (NTRS)

    Gilwee, W. J., Jr.; Parker, J. A. (Inventor)

    1977-01-01

    A honeycomb-laminate composite structure was comprised of: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a noncombustible fibrous material impregnated with a polyimide resin laminated on the cellular core. A process for producing the honeycomb-laminate composite structure and articles containing the honeycomb-laminate composite structure is described.

  12. Probabilistic Design of Composite Structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2006-01-01

    A formal procedure for the probabilistic design evaluation of a composite structure is described. The uncertainties in all aspects of a composite structure (constituent material properties, fabrication variables, structural geometry, and service environments, etc.), which result in the uncertain behavior in the composite structural responses, are included in the evaluation. The probabilistic evaluation consists of: (1) design criteria, (2) modeling of composite structures and uncertainties, (3) simulation methods, and (4) the decision-making process. A sample case is presented to illustrate the formal procedure and to demonstrate that composite structural designs can be probabilistically evaluated with accuracy and efficiency.

  13. Bonded and Stitched Composite Structure

    NASA Technical Reports Server (NTRS)

    Zalewski, Bart F. (Inventor); Dial, William B. (Inventor)

    2014-01-01

    A method of forming a composite structure can include providing a plurality of composite panels of material, each composite panel having a plurality of holes extending through the panel. An adhesive layer is applied to each composite panel and a adjoining layer is applied over the adhesive layer. The method also includes stitching the composite panels, adhesive layer, and adjoining layer together by passing a length of a flexible connecting element into the plurality of holes in the composite panels of material. At least the adhesive layer is cured to bond the composite panels together and thereby form the composite structure.

  14. Causality and Composite Structure

    SciTech Connect

    Joglekar, Satish D.

    2007-10-03

    In this talk, we discuss the question of whether a composite structure of elementary particles, with a length scale 1/{lambda}, can leave observable effects of non-locality and causality violation at higher energies (but {<=}{lambda}); employing a model-independent approach based on Bogoliubov-Shirkov formulation of causality. We formulate a condition which must be fulfilled for the derived theory to be causal, if the fundamental theory is so; and analyze it to exhibit possibilities which fulfil and which violate the condition. We comment on how causality violating amplitudes can arise.

  15. Progressive Fracture of Composite Structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Minnetyan, Levon

    2008-01-01

    A new approach is described for evaluating fracture in composite structures. This approach is independent of classical fracture mechanics parameters like fracture toughness. It relies on computational simulation and is programmed in a stand-alone integrated computer code. It is multiscale, multifunctional because it includes composite mechanics for the composite behavior and finite element analysis for predicting the structural response. It contains seven modules; layered composite mechanics (micro, macro, laminate), finite element, updating scheme, local fracture, global fracture, stress based failure modes, and fracture progression. The computer code is called CODSTRAN (Composite Durability Structural ANalysis). It is used in the present paper to evaluate the global fracture of four composite shell problems and one composite built-up structure. Results show that the composite shells and the built-up composite structure global fracture are enhanced when internal pressure is combined with shear loads.

  16. Composition- and temperature-dependent liquid structures in Al-Cu alloys: an ab initio molecular dynamics and x-ray diffraction study

    NASA Astrophysics Data System (ADS)

    Xiong, L. H.; Wang, X. D.; Cao, Q. P.; Zhang, D. X.; Xie, H. L.; Xiao, T. Q.; Jiang, J. Z.

    2017-01-01

    The composition- and temperature-dependent liquid structures in eight Alrich-Cu binary alloys (from hypoeutectic Al93Cu7 to hypereutectic Al70Cu30) have been experimentally and computationally studied by x-ray diffraction (XRD) experiments and ab initio molecular dynamics (AIMD) simulations. The remarkable agreements of structure factors for all liquid Alrich-Cu alloys obtained from high-temperature high-energy XRD measurements and AIMD simulations have been achieved, which consolidates the analyses of structural evolutions in Alrich-Cu liquids during the cooling processing by AIMD simulations. The heat capacity of liquid Alrich-Cu alloys continuously increases and presents no abnormal peak when reducing the temperature, which differs from the reported prediction for 55-atom Alrich-Cu nanoliquids. The diffusivities of Al and Cu undergo an increasing deviation from Arrhenius behavior by tuning Cu concentration from 7 to 30 atomic percentages, correlated to the local ordering in these liquids by means of coordination number, bond-angle distribution, Honeycutt-Andersen index, bond-orientational order and Voronoi tessellation analyses. Upon cooling, the microstructure of the liquid Alrich-Cu alloys inclines to form Al2Cu crystal-like local atomic ordering, especially in the hypereutectic liquids. The favorable short-range ordering between Cu and Al atoms could cause the non-Arrhenius diffusion behavior.

  17. Composition-dependent structure of polycrystalline magnetron-sputtered V-Al-C-N hard coatings studied by XRD, XPS, XANES and EXAFS.

    PubMed

    Krause, Bärbel; Darma, Susan; Kaufholz, Marthe; Mangold, Stefan; Doyle, Stephen; Ulrich, Sven; Leiste, Harald; Stüber, Michael; Baumbach, Tilo

    2013-08-01

    V-Al-C-N hard coatings with high carbon content were deposited by reactive radio-frequency magnetron sputtering using an experimental combinatorial approach, deposition from a segmented sputter target. The composition-dependent coexisting phases within the coating were analysed using the complementary methods of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine-structure spectroscopy (EXAFS). For the analysis of the X-ray absorption near-edge spectra, a new approach for evaluation of the pre-edge peak was developed, taking into account the self-absorption effects in thin films. Within the studied composition range, a mixed face-centred cubic (V,Al)(C,N) phase coexisting with a C-C-containing phase was observed. No indication of hexagonal (V,Al)(N,C) was found. The example of V-Al-C-N demonstrates how important a combination of complementary methods is for the detection of coexisting phases in complex multi-element coatings.

  18. Composition-dependent structure of polycrystalline magnetron-sputtered V–Al–C–N hard coatings studied by XRD, XPS, XANES and EXAFS

    PubMed Central

    Krause, Bärbel; Darma, Susan; Kaufholz, Marthe; Mangold, Stefan; Doyle, Stephen; Ulrich, Sven; Leiste, Harald; Stüber, Michael; Baumbach, Tilo

    2013-01-01

    V–Al–C–N hard coatings with high carbon content were deposited by reactive radio-frequency magnetron sputtering using an experimental combinatorial approach, deposition from a segmented sputter target. The composition-dependent coexisting phases within the coating were analysed using the complementary methods of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine-structure spectroscopy (EXAFS). For the analysis of the X-ray absorption near-edge spectra, a new approach for evaluation of the pre-edge peak was developed, taking into account the self-absorption effects in thin films. Within the studied composition range, a mixed face-centred cubic (V,Al)(C,N) phase coexisting with a C–C-containing phase was observed. No indication of hexagonal (V,Al)(N,C) was found. The example of V–Al–C–N demonstrates how important a combination of complementary methods is for the detection of coexisting phases in complex multi-element coatings. PMID:24046506

  19. Composite materials for space structures

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.; Sykes, G. F.; Bowles, D. E.

    1985-01-01

    The use of advanced composites for space structures is reviewed. Barriers likely to limit further applications of composites are discussed and highlights of research to improve composites are presented. Developments in composites technology which could impact spacecraft systems are reviewed to identify technology needs and opportunities.

  20. Dependency Structures and Transformational Rules.

    ERIC Educational Resources Information Center

    Robinson, Jane J.

    In this paper the author shows that dependency grammars are not only equivalent to structure-free phrase-structure grammars (i.e., equally adequate), but are even more informative: they express both the "is a" relation which phrase-structure grammars express and the "governs" relation which phrase-structure grammars obscure. It…

  1. Temperature dependent structures and properties of Bi0.5Na0.5TiO3-based lead free piezoelectric composite.

    PubMed

    Zhang, Ji; Sun, Lei; Geng, Xiao-Yu; Zhang, Bin-Bin; Yuan, Guo-Liang; Zhang, Shan-Tao

    2016-07-05

    The thermal depolarization around 100 °C of the Bi0.5Na0.5TiO3-based piezoelectric solid solutions leads to the disappearance of macroscopic ferroelectric/piezoelectric properties and remains a long-standing obstacle for their actual applications. In this communication, we report lead-free piezoelectric composites of 0.94Bi0.5Na0.5TiO3-0.06BaTiO3:0.5ZnO (BNT-6BT:0.5ZnO, where 0.5 is the mole ratio of ZnO to BNT-6BT) with deferred thermal depolarization, which is experimentally confirmed by systematic temperature dependent dielectric, ferroelectric, piezoelectric measurements. Especially, based on temperature dependent X-ray diffraction measurements on unpoled and poled samples, thermal depolarization is confirmed to have no relationship with the structural phase transition, the possible mechanism for the deferred thermal depolarization is correlated with the ZnO-induced local electric field which can suppress the depolarization field. We believe our results may be helpful for understanding the origin of thermal depolarization in BNT-based piezoelectric materials, and thus provide an effective way to overcoming this obstacle.

  2. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1983-01-01

    Transverse properties of fiber constituents in composites, fatigue in composite materials, matrix dominated properties of high performance composites, numerical investigation of moisture effects, numerical investigation of the micromechanics of composite fracture, advanced analysis methods, compact lug design, and the RP-1 and RP-2 sailplanes projects are discussed.

  3. Bonded composite repair of composite structures

    NASA Astrophysics Data System (ADS)

    Mahler, Mary A.

    Repair and maintenance cost drives a large percentage of the lifetime cost of aircraft structures. Understanding repair issues can lead to a structure that significantly lowers the lifetime cost. Advanced composite materials, while offering the potential to increase aircraft capabilities with minimum weight, are more susceptible to repairable damage than conventional aircraft materials. Improved inspection and repair methods are required to ensure structural integrity and aircraft readiness in the existing operational environment. Many of today's innovative composite designs may result in aircraft structures that are unreasonably difficult to repair. As a first step, technical issues associated with bonded composite repair of composite structures were investigated. An extensive literature review identified many areas where real world composite repairs are being used successfully. An electronic database was developed summarizing the publications found during the literature review. The database includes publication, experimental test results and analytical results of advanced composite bonded repairs. The current analysis of repair does not account for the variations that exist in repair. To facilitate the analysis, a finite element interface was developed to provide analysts with a tool that would create complete finite element models of repaired structures efficiently and in a 3-dimensional view. The finite element models created by the developed interface were successfully correlated to test data for accuracy of the results. Parametric studies were performed using the interface to evaluate effects of repair variables. Thermal impact of repair on the repair panel is one area lacking attention in the repair literature. To understand the impact of heat and thermal gradients of the repair, an analytical investigation was performed to evaluate. the parameters affected by heat. For a solid laminate, the temperature at the adhesive bondline was investigated. The primary

  4. ACEE composite structures technology

    NASA Technical Reports Server (NTRS)

    Quinlivan, John T.; Wilson, Robert D.; Smith, Peter J.; Johnson, Ronald W.

    1984-01-01

    Toppics addressed include: advanced composites on Boeing commercial aircraft; composite wing durability; damage tolerance technology development; heavily loaded wing panel design; and pressure containment and damage tolerance in fuselages.

  5. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1979-01-01

    Technology utilization of fiber reinforced composite materials is discussed in the areas of physical properties, and life prediction. Programs related to the Composite Aircraft Program are described in detail.

  6. Investigation of Composite Structures

    NASA Technical Reports Server (NTRS)

    Hyer, Michael W.

    2000-01-01

    This final report consists of a compilation of four separate written documents, three dealing with the response and failure of elliptical composite cylinders to an internal pressure load, and the fourth dealing with the influence of manufacturing imperfections in curved composite panels. The three focused on elliptical cylinders consist of the following: 1 - A paper entitled "Progressive Failure Analysis of Internally Pressurized Elliptical Composite Cylinders," 2 - A paper entitled "Influence of Geometric Nonlinearities on the Response and Failure of Internally Pressurized Elliptical Composite Cylinders," and 3 - A report entitled "Response and Failure of Internally Pressurized Elliptical Composite Cyclinders." The document which deals with the influence of manufacturing imperfections is a paper entitled "Manufacturing Distortions of Curved Composite Panels."

  7. Precision Composite Space Structures

    DTIC Science & Technology

    2007-10-15

    analysis of composite laminates with bolted joints under bending loads. J Compos Mater 1995;29(1):15-36. 283 [D.52]. Lee JD. Three dimensional...fiber reinforced composite bends . J Compos Mater 1986;20(1):30-45. [D.57]. Nagesh. Finite-element analysis of pressure vessels with progressive...composite cylinder subjected to three-point bending : Correlation of beam theory with experiment. Compos Struct 2004;63(3-4):439-445. [D.135]. Huang ZM

  8. Composite structural materials. [fiber reinforced composites for aircraft structures

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

    1981-01-01

    Physical properties of fiber reinforced composites; structural concepts and analysis; manufacturing; reliability; and life prediction are subjects of research conducted to determine the long term integrity of composite aircraft structures under conditions pertinent to service use. Progress is reported in (1) characterizing homogeneity in composite materials; (2) developing methods for analyzing composite materials; (3) studying fatigue in composite materials; (4) determining the temperature and moisture effects on the mechanical properties of laminates; (5) numerically analyzing moisture effects; (6) numerically analyzing the micromechanics of composite fracture; (7) constructing the 727 elevator attachment rib; (8) developing the L-1011 engine drag strut (CAPCOMP 2 program); (9) analyzing mechanical joints in composites; (10) developing computer software; and (11) processing science and technology, with emphasis on the sailplane project.

  9. 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

  10. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1983-01-01

    Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

  11. Combustible structural composites and methods of forming combustible structural composites

    DOEpatents

    Daniels, Michael A.; Heaps, Ronald J.; Steffler, Eric D.; Swank, W. David

    2013-04-02

    Combustible structural composites and methods of forming same are disclosed. In an embodiment, a combustible structural composite includes combustible material comprising a fuel metal and a metal oxide. The fuel metal is present in the combustible material at a weight ratio from 1:9 to 1:1 of the fuel metal to the metal oxide. The fuel metal and the metal oxide are capable of exothermically reacting upon application of energy at or above a threshold value to support self-sustaining combustion of the combustible material within the combustible structural composite. Structural-reinforcing fibers are present in the composite at a weight ratio from 1:20 to 10:1 of the structural-reinforcing fibers to the combustible material. Other embodiments and aspects are disclosed.

  12. Combustible structural composites and methods of forming combustible structural composites

    DOEpatents

    Daniels, Michael A.; Heaps, Ronald J.; Steffler, Eric D; Swank, William D.

    2011-08-30

    Combustible structural composites and methods of forming same are disclosed. In an embodiment, a combustible structural composite includes combustible material comprising a fuel metal and a metal oxide. The fuel metal is present in the combustible material at a weight ratio from 1:9 to 1:1 of the fuel metal to the metal oxide. The fuel metal and the metal oxide are capable of exothermically reacting upon application of energy at or above a threshold value to support self-sustaining combustion of the combustible material within the combustible structural composite. Structural-reinforcing fibers are present in the composite at a weight ratio from 1:20 to 10:1 of the structural-reinforcing fibers to the combustible material. Other embodiments and aspects are disclosed.

  13. Composite desiccant structure

    DOEpatents

    Fraioli, Anthony V.; Schertz, William W.

    1987-01-01

    A composite formed of small desiccant particles retained in a dark matrix composed of a porous binder containing a transition metal oxide with pores to provide moisture transport with respect to the particles, and metallic fibers to remove the heat of condensation during dehumidification and provide heat for the removal of moisture during regeneration. The moisture absorbing properties of the composite may be regenerated by exposure of the dark matrix to solar radiation with dehumidification occurring at night.

  14. Composite desiccant structure

    DOEpatents

    Fraioli, A.V.; Schertz, W.W.

    1984-06-06

    This patent discloses a composite formed of small desiccant particles retained in a dark matrix composed of a porous binder containing a transition metal oxide with pores to provide moisture transport with respect to the particles, and metallic fibers to remove the heat of condensation during dehumidification and provide heat for the removal of moisture during regeneration. The moisture absorbing properties of the composite may be regenerated by exposure of the dark matrix to solar radiation with dehumidification occurring at night.

  15. Probabilistic assessment of composite structures

    NASA Technical Reports Server (NTRS)

    Shiao, Michael E.; Abumeri, Galib H.; Chamis, Christos C.

    1993-01-01

    A general computational simulation methodology for an integrated probabilistic assessment of composite structures is discussed and demonstrated using aircraft fuselage (stiffened composite cylindrical shell) structures with rectangular cutouts. The computational simulation was performed for the probabilistic assessment of the structural behavior including buckling loads, vibration frequencies, global displacements, and local stresses. The scatter in the structural response is simulated based on the inherent uncertainties in the primitive (independent random) variables at the fiber matrix constituent, ply, laminate, and structural scales that describe the composite structures. The effect of uncertainties due to fabrication process variables such as fiber volume ratio, void volume ratio, ply orientation, and ply thickness is also included. The methodology has been embedded in the computer code IPACS (Integrated Probabilistic Assessment of Composite Structures). In addition to the simulated scatter, the IPACS code also calculates the sensitivity of the composite structural behavior to all the primitive variables that influence the structural behavior. This information is useful for assessing reliability and providing guidance for improvement. The results from the probabilistic assessment for the composite structure with rectangular cutouts indicate that the uncertainty in the longitudinal ply stress is mainly caused by the uncertainty in the laminate thickness, and the large overlap of the scatter in the first four buckling loads implies that the buckling mode shape for a specific buckling load can be either of the four modes.

  16. Hydrodynamic Forces on Composite Structures

    DTIC Science & Technology

    2014-06-01

    the free surface and fluid-structure interaction. The comparable mass density between composite plates and water results in pronounced fluid...angles yields different free surface effects including vortices and the onset of cavitation . 14. SUBJECT TERMS Fluid structure interaction, FSI, finite...the effects of the free surface and fluid-structure interaction. The comparable mass density between composite plates and water results in pronounced

  17. Field-structured composite studies.

    SciTech Connect

    Martin, James Ellis; Williamson, Rodney L.

    2004-04-01

    Field-structured composites (FSCs) were produced by hosting micron-sized gold-coated nickel particles in a pre-polymer and allowing the mixture to cure in a magnetic field environment. The feasibility of controlling a composite's electrical conductivity using feedback control applied to the field coils was investigated. It was discovered that conductivity in FSCs is primarily determined by stresses in the polymer host matrix due to cure shrinkage. Thus, in cases where the structuring field was uniform and unidirectional so as to produce chainlike structures in the composite, no electrical conductivity was measured until well after the structuring field was turned off at the gel point. In situations where complex, rotating fields were used to generate complex, three-dimensional structures in a composite, very small, but measurable, conductivity was observed prior to the gel point. Responsive, sensitive prototype chemical sensors were developed based on this technology with initial tests showing very promising results.

  18. Dependency Structures for Statistical Machine Translation

    ERIC Educational Resources Information Center

    Bach, Nguyen

    2012-01-01

    Dependency structures represent a sentence as a set of dependency relations. Normally the dependency structures from a tree connect all the words in a sentence. One of the most defining characters of dependency structures is the ability to bring long distance dependency between words to local dependency structures. Another the main attraction of…

  19. Composite structural materials. [aircraft applications

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1981-01-01

    The development of composite materials for aircraft applications is addressed with specific consideration of physical properties, structural concepts and analysis, manufacturing, reliability, and life prediction. The design and flight testing of composite ultralight gliders is documented. Advances in computer aided design and methods for nondestructive testing are also discussed.

  20. Advanced technology composite aircraft structures

    NASA Technical Reports Server (NTRS)

    Ilcewicz, Larry B.; Walker, Thomas H.

    1991-01-01

    Work performed during the 25th month on NAS1-18889, Advanced Technology Composite Aircraft Structures, is summarized. The main objective of this program is to develop an integrated technology and demonstrate a confidence level that permits the cost- and weight-effective use of advanced composite materials in primary structures of future aircraft with the emphasis on pressurized fuselages. The period from 1-31 May 1991 is covered.

  1. A fishery-dependent based study of fish species composition and associated catch rates around oil and gas structures off Louisiana

    SciTech Connect

    Stanley, D.R.; Wilson, C.A. )

    1990-01-01

    The impact of oil and gas development on fish populations off Louisiana is presumed significant but poorly understood. This study was undertaken to determine the applicability of a logbook program in developing a long-term database of species composition and relative abundance of fish associated with oil and gas structures. A pilot logbook program involving 120 private vessel owners and 25 charterboat operators was conducted between March 1987 and December 1988. Participants recorded date, fishing time, fishing method, number of anglers, and catch composition at each structure fished. Logbooks from a total of 55 private vessel owners and 10 charterboat operators were used in the analysis. Data collected included 15,780 angler hours of fishing effort and 61,227 fish caught over the study period. A total of 1,719 trips were made to 589 different oil and gas structures with at least 46 different species of fish caught. Red snapper and spotted seatrout were the most commonly caught species and had the highest catch rates. Results differed from past logbook programs and creel surveys, possibly indicating a change in the community of fish associated with oil and gas structures.

  2. The dependence of phase change enthalpy on the pore structure and interfacial groups in hydrated salts/silica composites via sol-gel.

    PubMed

    Wu, Yuping; Wang, Tao

    2015-06-15

    It was found that the procedures for incorporating hydrated salts into silica, including mixing with sol in an instant (S1 procedure), mixing with sol via drop by drop (S2 procedure) and mixing until the sol forming the gel (S3 procedure), had pronounced effects on the phase change enthalpy of hydrated salts/silica composite via sol-gel process. The discrepancy of phase change enthalpies of the composites with the same content of hydrated salts can be as high as 40 kJ/kg. To unveil the mechanism behind, the pore structure of silica matrix and interfacial functional groups were investigated extensively. It was revealed that different incorporation procedures resulted in distinct pore structure of silica matrix and different intensities of interfacial Si-OH groups. The S3 procedure was beneficial to induce the silica matrix with bigger pore size and fewer Si-OH groups. Consequently, the phase change enthalpy of the hydrated salts/silica composite prepared by this procedure was the highest because of its lower size confinement effects and weaker adsorption by Si-OH groups. This study will provide insight into the preparation of shape-stabilized phase change materials for thermal energy storage applications.

  3. Composition dependence of the optical properties and band structure of the zinc-blende ZnS1-xOx: a first principles study

    NASA Astrophysics Data System (ADS)

    Gueddim, A.; Zerroug, S.; Bouarissa, N.

    2015-08-01

    We present first principles calculations of structural, electronic and optical properties of ZnS1-xOx in the zinc-blende phase. We employ the full potential linearized augmented plane wave method within the density functional theory in the generalized gradient approximation and Engel-Vosko generalized gradient approximation. Features such as the lattice constant, the bulk modulus and its pressure derivative are reported. The agreement between our calculated results and available experimental and theoretical data is generally good. Direct and indirect energy band gaps as a function of the oxygen composition in the material of interest are presented and discussed. The material under investigation is found to remain a direct band gap semiconductor over all the alloy composition range (0-1). Furthermore, the optical properties such as the dielectric function, the refractive index, the reflectivity and the electron loss energy have also been reported and analysed.

  4. Load Diffusion in Composite Structures

    NASA Technical Reports Server (NTRS)

    Horgan, Cornelius O.; Simmonds, J. G.

    2000-01-01

    This research has been concerned with load diffusion in composite structures. Fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures. Analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and assessing results from finite element analyses. The decay behavior of stresses and other field quantities provides a significant aid towards this process. The results are also amendable to parameter study with a large parameter space and should be useful in structural tailoring studies.

  5. Linear dependencies between composite fermion states

    NASA Astrophysics Data System (ADS)

    Meyer, M. L.; Liabøtrø, O.; Viefers, S.

    2016-09-01

    The formalism of composite fermions (CFs) has been one of the most prominent and successful approaches to describing the fractional quantum Hall effect, in terms of trial many-body wave functions. Testing the accuracy of the latter typically involves rather heavy numerical comparison to exact diagonalization results. Thus, optimizing computational efficiency has been an important technical issue in this field. One generic (and not yet fully understood) property of the CF approach is that it tends to overcount the number of linearly independent candidate states for fixed sets of quantum numbers. Technically speaking, CF Slater determinants that are orthogonal before projection to the lowest Landau level, may lead to wave functions that are identical, or possess linear dependencies, after projection. This leads to unnecessary computations, and has been pointed out in the literature both for fermionic and bosonic systems. We here present a systematic approach that enables us to reveal all linear dependencies between bosonic compact states in the lowest CF ‘cyclotron energy’ sub-band, and almost all dependencies in higher sub-bands, at the level of the CF Slater determinants, i.e. before projection, which implies a major computational simplification. Our approach is introduced for so-called simple states of two-species rotating bosons, and then generalized to generic compact bosonic states, both one- and two-species. Some perspectives also apply to fermionic systems. The identities and linear dependencies we find, are analytically exact for ‘brute force’ projection in the disk geometry.

  6. Structural Qualification of Composite Airframes

    NASA Technical Reports Server (NTRS)

    Kedward, Keith T.; McCarty, John E.

    1997-01-01

    The development of fundamental approaches for predicting failure and elongation characteristics of fibrous composites are summarized in this document. The research described includes a statistical formulation for individual fiber breakage and fragmentation and clustered fiber breakage, termed macrodefects wherein the aligned composite may represent a structural component such as a reinforcing bar element, a rebar. Experimental work conducted in support of the future exploitation of aligned composite rebar elements is also described. This work discusses the experimental challenges associated with rebar tensile test evaluation and describes initial numerical analyses performed in support of the experimental program.

  7. Composition-dependent structural and electronic properties of Mg(95-x)Zn(x)Ca5 metallic glasses: an ab initio molecular dynamics study.

    PubMed

    Li, S N; Liu, J B; Li, J H; Wang, J; Liu, B X

    2015-02-26

    Recent progress in the synthesis of Mg-based metallic glasses (MGs) has allowed them to be considered as potential candidates for biodegradable and bioabsorbable implant materials. In this work, we use the Mg-Zn-Ca system as a representative to investigate the effect of composition on the atomic-level structure and local chemical environment in Mg-based MGs from ab initio molecular dynamics simulations. The results suggest that the short-range order of Mg(95-x)Zn(x)Ca5 (x = 21, 25, 29, and 33) MGs is characterized by Zn-centered icosahedral and icosahedral-like clusters, which show an increasing number and a rising tendency to interpenetrate each other with the enrichment of Zn constituents. A considerable degree of charge transfer between Zn and the surrounding Mg/Ca atoms is observed through electronic structure and bonding character analysis. At Zn-rich compositions, a percolated Zn-Zn network extended throughout the entire sample is formed, upon which the accumulated charges around Zn atoms are associated into a continuous conductivity path. Such results may shed light on the improved corrosion resistance of the Zn-rich Mg-Zn-Ca MGs.

  8. Advanced strategic interceptor composite structures

    SciTech Connect

    Ennis, D.H.; Patty, C.E. Jr.

    1993-12-31

    Launch mass reduction, stiffness increase, and primary bending mode frequency increase remain the prime focus of the US Army Strategic Defense Command (USASDC) advanced composite material development and testing program. The initial activity was directed toward fabrication of a demonstration structure consistent with the Ground-Based Interceptor (GBI) ERIS flight design. The objectives of this phase of the work were three-fold: selection of the optimum composite materials; concurrent bonding and joining technology development; evaluation of the performance of each test structure relative to its metal counterpart and relative to alternative composites. The effort exceeded model predictions. The resin matrix composite structure mass was 52% lower than the metal design. Modal testing demonstrated a 200% increase in stiffness and a 41% gain in first mode bending frequency. Given the demonstrated level of success, an additional element was added to the task focus: cost-effective, mass quantity fabrication techniques. Single step technology has been successfully applied to a relatively simple thermoset based bridge structure. Two step molding and assembly have been demonstrated for a GBI-X class thermoplastic structure. Preliminary testing has been completed to isolate and resolve problems associated with single step fabrication of the more complex GBI-X class structure. Fabrication of an appropriate test article as preparation for modal survey evaluation of the latter is in progress. Results are presented. Future program directions are summarized.

  9. Structural behavior of composites with progressive fracture

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon; Chamis, Christos C.; Murthy, Pappu L. N.

    1990-01-01

    Structural characteristics such as natural frequencies and buckling loads with corresponding mode shapes were investigated during progressive fracture of multilayer, angle-plied polymer matrix composites. A computer program was used to generate the numerical results for overall mechanical response of damaged composites. Variations in structural characteristics as a function of the previously applied loading were studied. Results indicate that most of the overall structural properties were preserved throughout a significant proportion of the ultimate fracture load. For the cases studied, changes in structural behavior began to occur after 70 percent of the ultimate fracture load was applied. However, the individual nature of the structural change was rather varied depending on the laminate configuration, fiber orientation, and the boundary conditions.

  10. Progressive Fracture of Composite Structures

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon

    2001-01-01

    This report includes the results of a research in which the COmposite Durability STRuctural ANalysis (CODSTRAN) computational simulation capabilities were augmented and applied to various structures for demonstration of the new features and verification. The first chapter of this report provides an introduction to the computational simulation or virtual laboratory approach for the assessment of damage and fracture progression characteristics in composite structures. The second chapter outlines the details of the overall methodology used, including the failure criteria and the incremental/iterative loading procedure with the definitions of damage, fracture, and equilibrium states. The subsequent chapters each contain an augmented feature of the code and/or demonstration examples. All but one of the presented examples contains laminated composite structures with various fiber/matrix constituents. For each structure simulated, damage initiation and progression mechanisms are identified and the structural damage tolerance is quantified at various degradation stages. Many chapters contain the simulation of defective and defect free structures to evaluate the effects of existing defects on structural durability.

  11. From Homogeneous to Segregated Structure of Poly(dimethylsiloxane)/Cellulose Derivative Mixed Langmuir Films Depending on Composition: An in Situ Neutron Reflectivity Study.

    PubMed

    El Haitami, Alae; Goldmann, Michel; Cousin, Fabrice; Dosseh, Gilberte; Cantin, Sophie

    2015-06-16

    The mixing behavior of deuterated polydimethylsiloxane (PDMSd) and cellulose acetate butyrate (CAB) spread as Langmuir films at the air-water interface was studied by means of surface pressure-area isotherms, Brewster angle microscopy (BAM) observations, and in situ neutron reflectivity. The contrast variation method was used with different D2O/H2O mixtures as subphase, allowing contrast matching to either CAB, PDMSd, or PDMSd/CAB mixed film if homogeneous. At PDMSd volume fractions Φ lower than 0.6, the mixed film is a homogeneous monolayer throughout the film compression, in agreement with the monophasic film observed by BAM and the attractive interactions between PDMSd and CAB evidenced from the isotherm measurements. In contrast, at PDMSd volume fractions Φ higher than 0.6, a vertically segregated structure of the mixed film is highlighted. Indeed, whatever the surface pressure, a bilayer structure is observed with a PDMSd layer in contact with the air over a thin CAB layer in contact with the subphase. These results show that the structure of the film is mainly driven by the PDMSd volume fraction which allows obtaining either a homogeneous membrane which composition can be tuned or a vertically segregated system. In contrast, only the thickness of the layers varies with the surface pressure while the structure of the film is not affected.

  12. Textile composite fuselage structures development

    NASA Technical Reports Server (NTRS)

    Jackson, Anthony C.; Barrie, Ronald E.; Chu, Robert L.

    1993-01-01

    Phase 2 of the NASA ACT Contract (NAS1-18888), Advanced Composite Structural Concepts and Materials Technology for Transport Aircraft Structures, focuses on textile technology, with resin transfer molding or powder coated tows. The use of textiles has the potential for improving damage tolerance, reducing cost and saving weight. This program investigates resin transfer molding (RTM), as a maturing technology for high fiber volume primary structures and powder coated tows as an emerging technology with a high potential for significant cost savings and superior structural properties. Powder coated tow technology has promise for significantly improving the processibility of high temperature resins such as polyimides.

  13. Composite Crew Module: Primary Structure

    NASA Technical Reports Server (NTRS)

    Kirsch, Michael T.

    2011-01-01

    In January 2007, the NASA Administrator and Associate Administrator for the Exploration Systems Mission Directorate chartered the NASA Engineering and Safety Center to design, build, and test a full-scale crew module primary structure, using carbon fiber reinforced epoxy based composite materials. The overall goal of the Composite Crew Module project was to develop a team from the NASA family with hands-on experience in composite design, manufacturing, and testing in anticipation of future space exploration systems being made of composite materials. The CCM project was planned to run concurrently with the Orion project's baseline metallic design within the Constellation Program so that features could be compared and discussed without inducing risk to the overall Program. This report discusses the project management aspects of the project including team organization, decision making, independent technical reviews, and cost and schedule management approach.

  14. Drawing dependent structures, mechanical properties and cyclization behaviors of polyacrylonitrile and polyacrylonitrile/carbon nanotube composite fibers prepared by plasticized spinning.

    PubMed

    Li, Xiang; Qin, Aiwen; Zhao, Xinzhen; Liu, Dapeng; Wang, Haiye; He, Chunju

    2015-09-14

    Drawing to change the structural properties and cyclization behaviors of the polyacrylonitrile (PAN) chains in crystalline and amorphous regions is carried out on PAN and PAN/carbon nanotube (CNT) composite fibers. Various characterization methods including Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and thermal gravimetric analysis are used to monitor the structural evolution and cyclization behaviors of the fibers. With an increase of the draw ratio during the plasticized spinning process, the structural parameters of the fibers, i.e. crystallinity and planar zigzag conformation, are decreased at first, and then increased, which are associated with the heat exchange rate and the oriented-crystallization rate. A possible mechanism for plasticized spinning is proposed to explain the changing trends of crystallinity and planar zigzag conformation. PAN and PAN/CNT fibers exhibit various cyclization behaviors induced by drawing, e.g., the initiation temperature for the cyclization (Ti) of PAN fibers is increased with increasing draw ratio, while Ti of PAN/CNT fibers is decreased. Drawing also facilitates cyclization and lowers the percentage of β-amino nitrile for PAN/CNT fibers during the stabilization.

  15. Commercial transport aircraft composite structures

    NASA Technical Reports Server (NTRS)

    Mccarty, J. E.

    1983-01-01

    The role that analysis plays in the development, production, and substantiation of aircraft structures is discussed. The types, elements, and applications of failure that are used and needed; the current application of analysis methods to commercial aircraft advanced composite structures, along with a projection of future needs; and some personal thoughts on analysis development goals and the elements of an approach to analysis development are discussed.

  16. Designing a New Class of Electrocatalysts for Polymer Electrolyte Membrane Fuel Cells: Probing Size, Composition, and Structure Dependent Electrocatalytic Performance in High-Quality, One-Dimensional Noble Metal Nanostructures

    NASA Astrophysics Data System (ADS)

    Koenigsmann, Christopher

    A key challenge in the practical commercialization of PEMFCs is the extremely high cost and relatively poor durability of carbon supported Pt nanoparticle (Pt NP/C) electrocatalysts utilized in both the anode and cathode half-cells. Herein, we synthesize and characterize a new class of high-quality one-dimensional noble metal nanostructures as a potentially new and promising structural paradigm for the next generation of electrocatalyst materials. Specifically, we investigate the nature of the complex interplay amongst size, chemical composition, and electrocatalytic performance in high-quality elemental and bimetallic 1D noble metal nanowire systems with an emphasis on achieving efficient and sustainable methods for catalyst preparation. In terms of nanowire dimensions and composition, an interesting and measureable size-dependent enhancement in performance emerges in the case of elemental Pt, Pd, and Pd1-xAux nanowires possessing diameters ranging from the submicron (d = ˜200 nm) to the ultrathin regime (d = ˜1 nm). In a similar context, we have considered the role of chemical composition in 1D electrocatalysts and noted significant composition-dependent enhancements in activity and durability in high-quality, bimetallic Pd1-xAux and Pd1-xPtx NWs. A key finding that is apparent from these experimental results is that widely seen behavioral trends in the composition- and size-dependent performance for 0D nanoparticle-based catalysts do not hold in the case of 1D architectures, because of the patently unique structural and electronic effects, associated with their anisotropic structures. As a culmination of our efforts to take advantage of these intrinsic structure-activity correlations, our group has developed a morphology-, size-, and composition-optimized Pd9Au NW possessing a Pt monolayer shell (PtML˜Pd9Au NWs) electrocatalyst with an ultrathin 2 nm diameter, which yielded outstanding Pt mass and platinum group metal activities of 2.56 A/mgPt and 0.64 A

  17. Compositional dependence of the local structure of Se{sub x}Te{sub 1-x} alloys: Electron energy-loss spectra, real-space multiple-scattering calculations, and first-principles molecular dynamics

    SciTech Connect

    Katcho, N. A.; Lomba, E.; Urones-Garrote, E.; Otero-Diaz, L. C.; Landa-Canovas, A. R.

    2006-06-01

    In this work we present an investigation on the composition dependence of the local structure in Se{sub x}Te{sub 1-x} crystalline alloys analyzing their experimental energy-loss spectra with the aid of a real-space multiple-scattering modeling approach and first-principles molecular dynamics. The concourse of this latter technique is essential for a proper modeling of the alloy spectra. From our results, it can be inferred that Se{sub x}Te{sub 1-x} alloys exhibit a high degree of substitutional disorder ruling out the existence of fully ordered alternating copolymer chains of Se and Te atoms.

  18. Application of Composite Mechanics to Composites Enhanced Concrete Structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Gotsis, Pascal K.

    2006-01-01

    A new and effective method is described to design composites to repair damage or enhance the overload strength of concrete infrastructures. The method is based on composite mechanics which is available in computer codes. It is used to simulate structural sections made from reinforced concrete which are typical in infrastructure as well as select reinforced concrete structures. The structural sections are represented by a number of layers through the thickness where different layers are used in concrete, and for the composite. The reinforced concrete structures are represented with finite elements where the element stiffness parameters are from the structural sections which are represented by composite mechanics. The load carrying capability of the structure is determined by progressive structural fracture. Results show up to 40 percent improvements for damage and for overload enhancement with relatively small laminate thickness for the structural sections and up to three times for the composite enhanced select structures (arches and domes).

  19. ACEE Composite Structures Technology: Review of selected NASA research on composite materials and structures

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program was designed to develop technology for advanced composites in commercial aircraft. Research on composite materials, aircraft structures, and aircraft design is presented herein. The following parameters of composite materials were addressed: residual strength, damage tolerance, toughness, tensile strength, impact resistance, buckling, and noise transmission within composite materials structures.

  20. Composition dependences of crystal structure and electrical properties of epitaxial Pb(Zr,Ti)O3 films grown on Si and SrTiO3 substrates

    NASA Astrophysics Data System (ADS)

    Okamoto, Shoji; Okamoto, Satoshi; Yokoyama, Shintaro; Akiyama, Kensuke; Funakubo, Hiroshi

    2016-10-01

    {100}-oriented Pb(Zr x ,Ti1- x )O3 (PZT) thin films of approximately 2 µm thickness and Zr/(Zr + Ti) ratios of 0.39-0.65 were epitaxially grown on (100)cSrRuO3//(100)SrTiO3 (STO) and (100)cSrRuO3//(100)cLaNiO3//(100)CeO2//(100)YSZ//(100)Si (Si) substrates having different thermal expansion coefficients by pulsed metal-organic chemical vapor deposition (MOCVD). The effects of Zr/(Zr + Ti) ratio and type of substrate on the crystal structure and dielectric, ferroelectric and piezoelectric properties of the films were systematically investigated. The X-ray diffraction measurement showed that both films changed from having a tetragonal symmetry to rhombohedral symmetry through the coexisting region with increasing Zr/(Zr + Ti) ratio. This region showed the Zr/(Zr + Ti) ratios of 0.45-0.59 for the films on the STO substrates that were wider than the films on the Si substrates. Saturation polarization values were minimum at approximately Zr/(Zr + Ti) = 0.50 for the films on the STO substrates, and no obvious Zr/(Zr + Ti) ratio dependence was detected in the films on the Si substrates. On the other hand, the maximum field-induced strain values measured by scanning force microscopy at approximately Zr/(Zr + Ti) = 0.50 at 100 kV/cm were about 0.5 and 0.1% in the films on the Si and STO, respectively.

  1. Composition-dependent structural and Raman spectroscopic studies on Y{sub 1-x}Ho{sub x}CrO{sub 3} (0≤x≤0.1)

    SciTech Connect

    Mall, Ashish Kumar; Garg, Ashish; Gupta, Rajeev

    2015-06-24

    In this paper we report the synthesis and structural characterization of polycrystalline holmium doped YCrO{sub 3} samples prepared by solid state reaction method. X-ray diffraction studies confirm the formation of single phase pure materials. Increasing Holmium substitution in Y{sub 1-x}Ho{sub x}CrO{sub 3} (0≤x≤0.1) allows a quasi-continuous tuning of the lattice in this multiferroic chromite without any magnetic interference effects of rare-earth ions. The composition dependent Raman scattering studies at room temperature reveal decreasing Raman mode frequencies with increasing holmium content consistent with the X-ray data. Decreasing phonon frequency shifts with increasing holmium content occurs, depending on the average rare-earth ion radius determined by the concentration of Y{sup +3} and Ho{sup +3}.

  2. Desmosome structure, composition and function.

    PubMed

    Garrod, David; Chidgey, Martyn

    2008-03-01

    Desmosomes are intercellular junctions of epithelia and cardiac muscle. They resist mechanical stress because they adopt a strongly adhesive state in which they are said to be hyper-adhesive and which distinguishes them from other intercellular junctions; desmosomes are specialised for strong adhesion and their failure can result in diseases of the skin and heart. They are also dynamic structures whose adhesiveness can switch between high and low affinity adhesive states during processes such as embryonic development and wound healing, the switching being signalled by protein kinase C. Desmosomes may also act as signalling centres, regulating the availability of signalling molecules and thereby participating in fundamental processes such as cell proliferation, differentiation and morphogenesis. Here we consider the structure, composition and function of desmosomes, and their role in embryonic development and disease.

  3. Hybrid Composite Cryogenic Tank Structure

    NASA Technical Reports Server (NTRS)

    DeLay, Thomas

    2011-01-01

    A hybrid lightweight composite tank has been created using specially designed materials and manufacturing processes. The tank is produced by using a hybrid structure consisting of at least two reinforced composite material systems. The inner composite layer comprises a distinct fiber and resin matrix suitable for cryogenic use that is a braided-sleeve (and/or a filamentwound layer) aramid fiber preform that is placed on a removable mandrel (outfitted with metallic end fittings) and is infused (vacuum-assisted resin transfer molded) with a polyurethane resin matrix with a high ductility at low temperatures. This inner layer is allowed to cure and is encapsulated with a filamentwound outer composite layer of a distinct fiber resin system. Both inner and outer layer are in intimate contact, and can also be cured at the same time. The outer layer is a material that performs well for low temperature pressure vessels, and it can rely on the inner layer to act as a liner to contain the fluids. The outer layer can be a variety of materials, but the best embodiment may be the use of a continuous tow of carbon fiber (T-1000 carbon, or others), or other high-strength fibers combined with a high ductility epoxy resin matrix, or a polyurethane matrix, which performs well at low temperatures. After curing, the mandrel can be removed from the outer layer. While the hybrid structure is not limited to two particular materials, a preferred version of the tank has been demonstrated on an actual test tank article cycled at high pressures with liquid nitrogen and liquid hydrogen, and the best version is an inner layer of PBO (poly-pphenylenebenzobisoxazole) fibers with a polyurethane matrix and an outer layer of T-1000 carbon with a high elongation epoxy matrix suitable for cryogenic temperatures. A polyurethane matrix has also been used for the outer layer. The construction method is ideal because the fiber and resin of the inner layer has a high strain to failure at cryogenic

  4. Global Failure Modes in Composite Structures

    NASA Technical Reports Server (NTRS)

    Knauss, W. G.; Gonzalez, Luis

    2001-01-01

    . The question of "scaling" is an essential concern in any structural materials investigation. For example, experiments in the past have shown that the "strength" of a composite depends on hole size. As a consequence the validity of traditional fracture mechanics concepts applied to composite materials failure must be questioned. The size of the fibers, the dimensions of the laminae, etc. together with the fact that, because of the layered anisotropy, the stress field is no longer two-dimensional, prevent the otherwise obviously confident use of "similarity concepts". Therefore, the question needs to be raised of whether in composites "size matters or not", i.e., whether the results obtained in a laboratory using small coupons are truly representative of the situation involving a full scale component.

  5. Microstructure and Crystal Structure in TAGS Compositions

    SciTech Connect

    Thompson, A. J.; Sharp, J; Rawn, Claudia J

    2009-01-01

    GeTe, a small bandgap semiconductor that has native p-type defects due to Ge vacancies, is an important constituent in the thermoelectric material known as TAGS. TAGS is an acronym for alloys of GeTe with AgSbTe{sub 2}, and compositions are normally designated as TAGS-x, where x is the fraction of GeTe. TAGS-85 is the most important with regard to applications, and there is also commercial interest in TAGS-80. The crystal structure of GeTe{sub 1+{delta}} has a composition-dependent phase transformation at a temperature ranging from 430 C ({delta} = 0) to {approx}400 C ({delta} = 0.02). The high-temperature form is cubic. The low-temperature form is rhombohedral for {delta} < 0.01, as is the case for good thermoelectric performance. Addition of AgSbTe{sub 2} shifts the phase transformation to lower temperatures, and one of the goals of this work is a systematic study of the dependence of transformation temperature on the parameter x. We present results on phase transformations and associated instabilities in TAGS compositions in the range of 70 at.% to 85 at.% GeTe.

  6. Multiscale Multifunctional Progressive Fracture of Composite Structures

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Minnetyan, L.

    2012-01-01

    A new approach is described for evaluating fracture in composite structures. This approach is independent of classical fracture mechanics parameters like fracture toughness. It relies on computational simulation and is programmed in a stand-alone integrated computer code. It is multiscale, multifunctional because it includes composite mechanics for the composite behavior and finite element analysis for predicting the structural response. It contains seven modules; layered composite mechanics (micro, macro, laminate), finite element, updating scheme, local fracture, global fracture, stress based failure modes, and fracture progression. The computer code is called CODSTRAN (Composite Durability Structural ANalysis). It is used in the present paper to evaluate the global fracture of four composite shell problems and one composite built-up structure. Results show that the composite shells. Global fracture is enhanced when internal pressure is combined with shear loads. The old reference denotes that nothing has been added to this comprehensive report since then.

  7. Composite structures for commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Vosteen, L. F.

    1978-01-01

    The development of graphite-epoxy composite structures for use on commercial transport aircraft is considered. Six components, three secondary structures, and three primary structures, are presently under development. The six components are described along with some of the key features of the composite designs and their projected weight savings.

  8. Interfacial chemistry and structure in ceramic composites

    SciTech Connect

    Jones, R.H.; Saenz, N.T.; Schilling, C.H.

    1990-09-01

    The interfacial chemistry and structure of ceramic matrix composites (CMCs) play a major role in the properties of these materials. Fiber-matrix interfaces chemistries are vitally important in the fracture strength, fracture toughness, and fracture resistance of ceramic composites because they influence fiber loading and fiber pullout. Elevated-temperature properties are also linked to the interfacial characteristics through the chemical stability of the interface in corrosive environments and the creep/pullout behavior of the interface. Physical properties such as electrical and thermal conductivity are also dependent on the interface. Fiber-matrix interfaces containing a 1-{mu}m-thick multilayered interface with amorphous and graphitic C to a 1-nm-thick SiO{sub 2} layer can result from sintering operations for some composite systems. Fibers coated with C, BN, C/BC/BN, and Si are also used to produce controlled interface chemistries and structures. Growth interfaces within the matrix resulting from processing of CMCs can also be crucial to the behavior of these materials. Evaluation of the interfacial chemistry and structure of CMCs requires the use of a variety of analytical tools, including optical microscopy, scanning electron microscopy, Auger electron spectroscopy, and transmission electron microscopy coupled with energy dispersive x-ray analysis. A review of the interfacial chemistry and structure of SiC whisker- and fiber-reinforced Si{sub 3}N{sub 4} and SiC/SiC materials is presented. Where possible, correlations with fracture properties and high-temperature stability are made. 94 refs., 10 figs.

  9. Effect of stress concentrations in composite structures

    NASA Technical Reports Server (NTRS)

    Babcock, C. D.; Waas, A. M.

    1985-01-01

    Composite structures have found wide use in many engineering fields and a sound understanding of their response under load is important to their utilization. An experimental program is being carried out to gain a fundamental understanding of the failure mechanics of multilayered composite structures at GALCIT. As a part of this continuing study, the performance of laminated composite plates in the presence of a stress gradient and the failure of composite structures at points of thickness discontinuity is assessed. In particular, the questions of initiation of failure and its subsequent growth to complete failure of the structure are addressed.

  10. Rapid Prototyping of Composite Structures

    NASA Technical Reports Server (NTRS)

    Colton, Jonathan S.

    1998-01-01

    This final report for the project Rapid Production of Composite Structures covers the period from July 14, 1997 to September 30, 1998. It will present a short overview of the project, followed by the results to date and plans for the future. The goal of this research is to provide a minimum 100x reduction in the time required to produce arbitrary, laminated products without the need for a separate mold or an autoclave. It will accomplish this by developing the science underlying the rapid production of composite structures, specifically those of carbon fiber-epoxy materials. This scientific understanding will be reduced to practice in a demonstration device that will produce a part on the order of 12in. by 12in. by 6in. Work in the past year has focussed on developing an understanding of the materials issues and of the machine design issues. Our initial goal was to use UV cureable resins to accomplish full cure on the machine. Therefore, we have centered our materials work around whether or not UV cureable resins will work. Currently, the answer seems to be that they will not work, because UV light cannot penetrate the carbon fibers, and because no "shadow" curing seems to occur. As a result, non-UV cureable resins are being investigated. This has resulted in a change in the machine design focus. We are now looking into a "dip and place" machine design, whereby a prepreg layer would have one side coated with a curing agent, and then would be placed onto the previous layer. This would lead to cure at the interface, but not to the top of the layer. The formulation of the resins to accomplish this task at room or slightly elevated temperatures is being investigated, as is the machine design needed to apply the curing agent and then cure or partially cure the part. A final, out-of-autoclave, post-cure may be needed with this strategy, as final cure on the machine may not be possible, as it was for the initial UV cure strategy. The remainder of this report details the

  11. Composition Dependence of Bulk Alloy Properties

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1994-01-01

    We introduce an approximate expression for the direct calculation of properties of alloys in terms of the pure components. This rule can be obtained as a particular case from the Bozzolo-Ferrante-Smith (BFS) method, a recently developed semiempirical method for alloys. In particular, we examine the application of this rule to several examples of the concentration dependence of the lattice parameter of binary and ternary alloys.

  12. Rapid Prototyping of Composite Structures

    NASA Technical Reports Server (NTRS)

    Colton, Jonathan S.

    1998-01-01

    This progress report for the project Rapid Production of Composite Structures covers the period from July 14, 1997 to June 30, 1998. It will present a short overview of the project, followed by the results to date and plans for the future. The goal of this research is to provide a minimum 100x reduction in the time required to produce arbitrary, laminated products without the need for a separate mold or an autoclave. It will accomplish this by developing the science underlying the rapid production of composite structures, specifically those of carbon fiber-epoxy materials. This scientific understanding will be reduced to practice in a demonstration device that will produce a part on the order of 12" by 12" by 6". Work in the past year has focussed on developing an understanding of the materials issues and of the machine design issues. Our initial goal was to use UV cureable resins to accomplish full cure on the machine. Therefore, we have centered our materials work around whether or not UV cureable resins will work. Currently, the answer seems to be that they will not work, because UV light cannot penetrate the carbon fibers, and because no "shadow" curing seems to occur. As a result, non-UV cureable resins are being investigated. This has resulted in a change in the machine design focus. We are now looking into a "dip and place" machine design, whereby a prepreg layer would have one side coated with a curing agent, and then would be placed onto the previous layer. This would lead to cure at the interface, but not to the top of the layer. The formulation of the resins to accomplish this task at room or slightly elevated temperatures is being investigated, as is the machine design needed to apply the curing agent and then cure or partially cure the part. A final, out-of-autoclave, post-cure may be needed with this strategy, as final cure on the machine may not be possible, as it was for the initial UV cure strategy. The remainder of this report details the progress

  13. Impact analysis of composite aircraft structures

    NASA Technical Reports Server (NTRS)

    Pifko, Allan B.; Kushner, Alan S.

    1993-01-01

    The impact analysis of composite aircraft structures is discussed. Topics discussed include: background remarks on aircraft crashworthiness; comments on modeling strategies for crashworthiness simulation; initial study of simulation of progressive failure of an aircraft component constructed of composite material; and research direction in composite characterization for impact analysis.

  14. Composite structures for magnetosphere imager spacecraft

    NASA Technical Reports Server (NTRS)

    Chu, Tsuchin

    1994-01-01

    Results of a trade study addressing the issues and benefits in using carbon fiber reinforced composites for the Magnetosphere Imager (MI) spacecraft are presented. The MI mission is now part of the Sun/Earth Connection Program. To qualify for this category, new technology and innovative methods to reduce the cost and size have to be considered. Topics addressed cover: (1) what is a composite, including advantages and disadvantages of composites and carbon/graphite fibers; and (2) structural design for MI, including composite design configuration, material selection, and analysis of composite structures.

  15. Computational composite mechanics for aerospace propulsion structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    1987-01-01

    Specialty methods are presented for the computational simulation of specific composite behavior. These methods encompass all aspects of composite mechanics, impact, progressive fracture and component specific simulation. Some of these methods are structured to computationally simulate, in parallel, the composite behavior and history from the initial frabrication through several missions and even to fracture. Select methods and typical results obtained from such simulations are described in detail in order to demonstrate the effectiveness of computationally simulating: (1) complex composite structural behavior in general, and (2) specific aerospace propulsion structural components in particular.

  16. Computational composite mechanics for aerospace propulsion structures

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1986-01-01

    Specialty methods are presented for the computational simulation of specific composite behavior. These methods encompass all aspects of composite mechanics, impact, progressive fracture and component specific simulation. Some of these methods are structured to computationally simulate, in parallel, the composite behavior and history from the initial fabrication through several missions and even to fracture. Select methods and typical results obtained from such simulations are described in detail in order to demonstrate the effectiveness of computationally simulating (1) complex composite structural behavior in general and (2) specific aerospace propulsion structural components in particular.

  17. Durability of Composite Materials and Structures

    DTIC Science & Technology

    2009-11-02

    Michigan State University Composite Materials and Structures Center 2100 Engineering Building , East Lansing, MI 48824-1226 6.1 Objectives The...DATES COVERED (From - To) February 7, 2005 - January 31. 2009 4. TITLE AND SUBTITLE DURABILITY OF COMPOSITE MATERIALS AND STRUCTURES 5a...Manager: Dr. Yapa D.S. Rajapakse Office of Naval Research 875 N. Randolph Street Arlington, VA 22203-1995 DURABILITY OF COMPOSITE MATERIALS AND

  18. Time-dependent response of filamentary composite spherical pressure vessels

    NASA Technical Reports Server (NTRS)

    Dozier, J. D.

    1983-01-01

    A filamentary composite spherical pressure vessel is modeled as a pseudoisotropic (or transversely isotropic) composite shell, with the effects of the liner and fill tubes omitted. Equations of elasticity, macromechanical and micromechanical formulations, and laminate properties are derived for the application of an internally pressured spherical composite vessel. Viscoelastic properties for the composite matrix are used to characterize time-dependent behavior. Using the maximum strain theory of failure, burst pressure and critical strain equations are formulated, solved in the Laplace domain with an associated elastic solution, and inverted back into the time domain using the method of collocation. Viscoelastic properties of HBFR-55 resin are experimentally determined and a Kevlar/HBFR-55 system is evaluated with a FORTRAN program. The computed reduction in burst pressure with respect to time indicates that the analysis employed may be used to predict the time-dependent response of a filamentary composite spherical pressure vessel.

  19. Composition Dependence of the Properties of Noble-metal Nanoalloys

    NASA Astrophysics Data System (ADS)

    Fernández Seivane, Lucas; Barrón, Héctor; Benson, James; Weissker, Hans-Christian; López-Lozano, Xochitl

    2012-03-01

    Bimetallic nanostructured materials are of greater interest both from the scientific and technological points of view due to their potential to improve the catalytic properties of novel materials. Their applicability as well as the performance depends critically on their size, shape and composition, either as alloy or core-shell. In this work, the structural, electronic, magnetic and optical properties of bimetallic Au-Ag nanoclusters have been investigated through density-functional-theory-based calculations with the Siesta and Octopus codes. Different symmetries -tetrahedral, bipyramidal, decahedral and icosahedral- of bimetallic nanoparticles of 4-, 5-, 7- and 13-atoms, were taken into account including all the possibly different Au:Ag ratio concentrations. In combination with a statistical analysis of the performed calculations and the concepts of the Enthalpy of Mixing and Energy Excess, we have been able to predict the most probable gap and magnetic moment for all the composition stoichiometries. This approach allows us to understand the energy differences due to cluster shape effects, the stoichiometry and segregation. In addition, we can also obtain the bulk energy and surface energy of Au-Ag nanoalloys by looking at fixed number of atoms and fixed morphologies.

  20. The design of repairable advanced composite structures

    NASA Technical Reports Server (NTRS)

    Hart-Smith, L. J.

    1985-01-01

    This paper addresses the repair of advanced composite structures by mechanical fasteners or by adhesive bonding. It is shown that many of today's composite designs are unreasonably difficult to repair. Conversely, the knowledge to design repairable structures is already available, if only it is applied during the initial design stage. Bolted or riveted repairs require only the avoidance of extremely orthotropic composite fiber patterns; those near the quasi-isotropic layup are the most suitable. Mildly orthotropic fiber patterns are appropriate for structures in which there is a dominant load direction. Thick composite structures are shown to require bolted or riveted repairs while thin structures favor adhesively bonded permanent repairs, although provisions can be easily made for temporary mechanical repairs. The reasons why integrally stiffened cocured composite designs are usually impractical to repair are explained and alternative repairable design concepts are presented.

  1. Rate Dependent Deformation and Strength Analysis of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Stouffer, Donald C.

    1999-01-01

    A research program is being undertaken to develop rate dependent deformation and failure models for the analysis of polymer matrix composite materials. In previous work in this program, strain-rate dependent inelastic constitutive equations used to analyze polymers have been implemented into a mechanics of materials based composite micromechanics method. In the current work, modifications to the micromechanics model have been implemented to improve the calculation of the effective inelastic strain. Additionally, modifications to the polymer constitutive model are discussed in which pressure dependence is incorporated into the equations in order to improve the calculation of constituent and composite shear stresses. The Hashin failure criterion is implemented into the analysis method to allow for the calculation of ply level failure stresses. The deformation response and failure stresses for two representative uniaxial polymer matrix composites, IM7/977-2 and AS4-PEEK, are predicted for varying strain rates and fiber orientations. The predicted results compare favorably to experimentally obtained values.

  2. Creep of Structural Nuclear Composites

    SciTech Connect

    Will Windes; R.W. Lloyd

    2005-09-01

    A research program has been established to investigate fiber reinforced ceramic composites to be used as control rod components within a Very High Temperature Reactor (VHTR) design. Two candidate systems have been identified, carbon fiber reinforced carbon (Cf/C) and silicon carbide fiber reinforced silicon carbide (SiCf/SiC) composites. One of the primary degradation mechanisms anticipated for these core components is high temperature thermal and irradiation enhanced creep. As a consequence, high temperature test equipment, testing methodologies, and test samples for very high temperature (up to 1600º C) tensile strength and long duration creep studies have been established. Actual testing of both tubular and flat, "dog-bone"-shaped tensile composite specimens will begin next year. Since there is no precedence for using ceramic composites within a nuclear reactor, ASTM standard test procedures are currently being established from these high temperature mechanical tests.

  3. Quantification of Energy Release in Composite Structures

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon; Chamis, Christos C. (Technical Monitor)

    2003-01-01

    Energy release rate is usually suggested as a quantifier for assessing structural damage tolerance. Computational prediction of energy release rate is based on composite mechanics with micro-stress level damage assessment, finite element structural analysis and damage progression tracking modules. This report examines several issues associated with energy release rates in composite structures as follows: Chapter I demonstrates computational simulation of an adhesively bonded composite joint and validates the computed energy release rates by comparison with acoustic emission signals in the overall sense. Chapter II investigates the effect of crack plane orientation with respect to fiber direction on the energy release rates. Chapter III quantifies the effects of contiguous constraint plies on the residual stiffness of a 90 deg ply subjected to transverse tensile fractures. Chapter IV compares ICAN and ICAN/JAVA solutions of composites. Chapter V examines the effects of composite structural geometry and boundary conditions on damage progression characteristics.

  4. Quantification of Energy Release in Composite Structures

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon

    2003-01-01

    Energy release rate is usually suggested as a quantifier for assessing structural damage tolerance. Computational prediction of energy release rate is based on composite mechanics with micro-stress level damage assessment, finite element structural analysis and damage progression tracking modules. This report examines several issues associated with energy release rates in composite structures as follows: Chapter I demonstrates computational simulation of an adhesively bonded composite joint and validates the computed energy release rates by comparison with acoustic emission signals in the overall sense. Chapter II investigates the effect of crack plane orientation with respect to fiber direction on the energy release rates. Chapter III quantifies the effects of contiguous constraint plies on the residual stiffness of a 90 ply subjected to transverse tensile fractures. Chapter IV compares ICAN and ICAN/JAVA solutions of composites. Chapter V examines the effects of composite structural geometry and boundary conditions on damage progression characteristics.

  5. Fluid Structure Interaction Effect on Sandwich Composite Structures

    DTIC Science & Technology

    2011-09-01

    14. SUBJECT TERMS Fluid Structure Interaction, FSI, composite, balsa, low velocity impact, sandwich composites, VARTM , Vacuum Assisted Resin Transfer...11 1. Vacuum Assisted Resin Transfer Molding ( VARTM ) ...................11 2. Procedure...required equipment for VARTM composite production. ..............10 Figure 4. VARTM Lay-up (From [8

  6. Multi-functional composite structures

    SciTech Connect

    Mulligan, Anthony C.; Halloran, John; Popovich, Dragan; Rigali, Mark J.; Sutaria, Manish P.; Vaidyanathan, K. Ranji; Fulcher, Michael L.; Knittel, Kenneth L.

    2004-10-19

    Fibrous monolith processing techniques to fabricate multifunctional structures capable of performing more than one discrete function such as structures capable of bearing structural loads and mechanical stresses in service and also capable of performing at least one additional non-structural function.

  7. Multi-functional composite structures

    DOEpatents

    Mulligan, Anthony C.; Halloran, John; Popovich, Dragan; Rigali, Mark J.; Sutaria, Manish P.; Vaidyanathan, K. Ranji; Fulcher, Michael L.; Knittel, Kenneth L.

    2010-04-27

    Fibrous monolith processing techniques to fabricate multifunctional structures capable of performing more than one discrete function such as structures capable of bearing structural loads and mechanical stresses in service and also capable of performing at least one additional non-structural function.

  8. Certification of damage tolerant composite structure

    NASA Technical Reports Server (NTRS)

    Rapoff, Andrew J.; Dill, Harold D.; Sanger, Kenneth B.; Kautz, Edward F.

    1990-01-01

    A reliability based certification testing methodology for impact damage tolerant composite structure was developed. Cocured, adhesively bonded, and impact damaged composite static strength and fatigue life data were statistically analyzed to determine the influence of test parameters on the data scatter. The impact damage resistance and damage tolerance of various structural configurations were characterized through the analysis of an industry wide database of impact test results. Realistic impact damage certification requirements were proposed based on actual fleet aircraft data. The capabilities of available impact damage analysis methods were determined through correlation with experimental data. Probabilistic methods were developed to estimate the reliability of impact damaged composite structures.

  9. Structural Composites With Tuned EM Chirality

    DTIC Science & Technology

    2014-12-23

    AFRL-OSR-VA-TR-2015-0018 STRUCTURAL COMPOSITES WITH TUNED EM CHIRALITY Siavouche Nemat Nasser UNIVERSITY OF CALIFORNIA SAN DIEGO Final Report 12/23...REPORT Grant/Contract  Title:        STRUCTURAL  COMPOSITES  WITH  TUNED  EM   CHIRALITY     Grant  No.:  FA9550-­‐09-­‐1...structural   composites  with   tunable   chiral   elements   has   produced   some   impressive   results   in   the

  10. The Structure and Composition of Io's Atmosphere

    NASA Astrophysics Data System (ADS)

    Smyth, W. H.; Marconi, M. L.

    2011-12-01

    Io's atmosphere is thought to be generated principally by sublimation on the dayside and by multiple volcanoes scattered throughout its surface and more concentrated near the equator. While SO2 seems to be the principle product of these sources, many other chemical species are placed into the atmosphere by these sources, including substantial amounts of SO and S2 as well as smaller but observationally significant amounts of Na bearing molecules. These species in turn interact strongly with the torus plasma generating additional species such as O2, S, O, and Na. The strong interaction of the torus plasma with the neutral atmosphere not only exerts a profound effect on the composition of Io's atmosphere but also strongly affects the dynamics and thermodynamics of Io's atmosphere, particularly at higher altitudes. In addition, as Io orbits Jupiter, the change in location of the sublimation region and the eclipse of Io as it passes through Jupiter's shadow result in substantial variation in the atmosphere. A complex time-dependent three-dimensional atmosphere with strong spatial compositional variation is created. Here we extend the two-dimensional multispecies Navier-Stokes model of Smyth and Wong (2004) to three-dimensions, include two volcanic sources similar to Pele and Loki, and include the effect of Io's movement around Jupiter on sublimation. The effects of the torus plasma are also included as in Smyth and Wong. We will present the overall composition and structure of the atmosphere, O to S ratios in the upper atmosphere, and discuss a potential issue with the O2 abundance. Smyth, W.H. and M.C. Wong, Icarus 171, 171-182, 2004.

  11. Mechanical Model Development for Composite Structural Supercapacitors

    NASA Technical Reports Server (NTRS)

    Ricks, Trenton M.; Lacy, Thomas E., Jr.; Santiago, Diana; Bednarcyk, Brett A.

    2016-01-01

    Novel composite structural supercapacitor concepts have recently been developed as a means both to store electrical charge and to provide modest mechanical load carrying capability. Double-layer composite supercapacitors are often fabricated by impregnating a woven carbon fiber fabric, which serves as the electrodes, with a structural polymer electrolyte. Polypropylene or a glass fabric is often used as the separator material. Recent research has been primarily limited to evaluating these composites experimentally. In this study, mechanical models based on the Multiscale Generalized Method of Cells (MSGMC) were developed and used to calculate the shear and tensile properties and response of two composite structural supercapacitors from the literature. The modeling approach was first validated against traditional composite laminate data. MSGMC models for composite supercapacitors were developed, and accurate elastic shear/tensile properties were obtained. It is envisioned that further development of the models presented in this work will facilitate the design of composite components for aerospace and automotive applications and can be used to screen candidate constituent materials for inclusion in future composite structural supercapacitor concepts.

  12. Probabilistic assessment of smart composite structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Shiao, Michael C.

    1994-01-01

    A composite wing with spars and bulkheads is used to demonstrate the effectiveness of probabilistic assessment of smart composite structures to control uncertainties in distortions and stresses. Results show that a smart composite wing can be controlled to minimize distortions and to have specified stress levels in the presence of defects. Structural responses such as changes in angle of attack, vertical displacements, and stress in the control and controlled plies are probabilistically assessed to quantify their respective uncertainties. Sensitivity factors are evaluated to identify those parameters that have the greatest influence on a specific structural response. Results show that smart composite structures can be configured to control both distortions and ply stresses to satisfy specified design requirements.

  13. Advanced textile structural composites -- status and outlook

    SciTech Connect

    Arendts, F.J.; Drechsler, K.; Brandt, J.

    1993-12-31

    Composites with 3D woven, braided or knitted fiber reinforcement offer a high potential for the cost-effective manufacturing of structures featuring an interesting mechanical performance, for example with regard to damage tolerance or energy absorption capability. In this paper, the properties of various textile structural composites with regard to stiffness, strength, damage tolerance, energy absorption capability as well as the respective manufacturing processes (RTM or thermoplastic hybrid-yarn technique) are presented in comparison to conventional ud tape based composites. The influence of the fiber architecture on the mechanical performance (tensile stiffness and strength, compression strength, interlaminar shear strength, compression strength after impact, fracture mechanical properties, through-penetration resistance) of monolithic and composite sandwich structures has been evaluated in an experimental study. It has been shown that composites involving new 3D weavings with minimum fiber crimp can compete with tape-based laminates as far as stiffness and strength are concerned. Using knittings makes it possible to manufacture composites having superior through-penetration resistance. The specific feature of the 3D braiding process is the ability to produce complex shaped structures having a high degree of freedom with regard to fiber geometry. Finally, the application of various textile structural composites will be presented on the basis of three demonstrator components (automotive engine mount, aircraft leading edge and motor cycle helmet), and the potential for further developments will be discussed.

  14. Rate dependent constitutive models for fiber reinforced polymer composites

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.

    1990-01-01

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

  15. Development of stitched/RTM composite primary structures

    NASA Technical Reports Server (NTRS)

    Kullerd, Susan M.; Dow, Marvin B.

    1992-01-01

    The goal of the NASA Advanced Composites Technology (ACT) Program is to provide the technology required to gain the full benefit of weight savings and performance offered by composite primary structures. Achieving the goal is dependent on developing composite materials and structures which are damage tolerant and economical to manufacture. Researchers at NASA LaRC and Douglas Aircraft Company are investigating stitching reinforcement combined with resin transfer molding (RTM) to create structures meeting the ACT program goals. The Douglas work is being performed under a NASA contract entitled Innovative Composites Aircraft Primary Structures (ICAPS). The research is aimed at materials, processes and structural concepts for application in both transport wings and fuselages. Empirical guidelines are being established for stitching reinforcement in primary structures. New data are presented in this paper for evaluation tests of thick (90-ply) and thin (16-ply) stitched laminates, and from selection tests of RTM composite resins. Tension strength, compression strength and post-impact compression strength data are reported. Elements of a NASA LaRC program to expand the science base for stitched/RTM composites are discussed.

  16. On the structural analysis of textile composites

    NASA Astrophysics Data System (ADS)

    Bogdanovich, Alexander E.; Pastore, Christopher M.

    The local structural inhomogeneities which distinguish textile composites from laminated materials are discussed. Techniques for quantifying these inhomogeneities through three dimensional geometric modelling are introduced and methods of translating them into elastic properties are presented. Some basic ideas on application of spline functions to the stress field analysis in textile composites are proposed. The significance of internal continuity conditions for these materials is emphasized. Several analytical techniques based on the concept of a meso-volume are discussed. An example is presented to demonstrate the application of the method to structural analysis of textile composites.

  17. Strain Rate Dependent Modeling of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Stouffer, Donald C.

    1999-01-01

    A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. Strain rate dependent inelastic constitutive equations have been developed to model the polymer matrix, and have been incorporated into a micromechanics approach to analyze polymer matrix composites. The Hashin failure criterion has been implemented within the micromechanics results to predict ply failure strengths. The deformation model has been implemented within LS-DYNA, a commercially available transient dynamic finite element code. The deformation response and ply failure stresses for the representative polymer matrix composite AS4/PEEK have been predicted for a variety of fiber orientations and strain rates. The predicted results compare favorably to experimentally obtained values.

  18. Composite blade structural analyzer (COBSTRAN) user's manual

    NASA Technical Reports Server (NTRS)

    Aiello, Robert A.

    1989-01-01

    The installation and use of a computer code, COBSTRAN (COmposite Blade STRuctrual ANalyzer), developed for the design and analysis of composite turbofan and turboprop blades and also for composite wind turbine blades was described. This code combines composite mechanics and laminate theory with an internal data base of fiber and matrix properties. Inputs to the code are constituent fiber and matrix material properties, factors reflecting the fabrication process, composite geometry and blade geometry. COBSTRAN performs the micromechanics, macromechanics and laminate analyses of these fiber composites. COBSTRAN generates a NASTRAN model with equivalent anisotropic homogeneous material properties. Stress output from NASTRAN is used to calculate individual ply stresses, strains, interply stresses, thru-the-thickness stresses and failure margins. Curved panel structures may be modeled providing the curvature of a cross-section is defined by a single value function. COBSTRAN is written in FORTRAN 77.

  19. Compression Strength of Composite Primary Structural Components

    NASA Technical Reports Server (NTRS)

    Johnson, Eric R.; Starnes, James H., Jr. (Technical Monitor)

    2000-01-01

    The focus of research activities under NASA Grant NAG-1-2035 was the response and failure of thin-walled structural components. The research is applicable to the primary load carrying structure of flight vehicles, with particular emphasis on fuselage and wing'structure. Analyses and tests were performed that are applicable to the following structural components an aft pressure bulkhead, or a composite pressure dome, pressure cabin damage containment, and fuselage frames subject to crash-type loads.

  20. Integrating electrostatic adhesion to composite structures

    NASA Astrophysics Data System (ADS)

    Heath, Callum J. C.; Bond, Ian P.; Potter, Kevin D.

    2015-04-01

    Additional functionality within load bearing components holds potential for adding value to a structure, design or product. We consider the adaptation of an established technology, electrostatic adhesion or electroadhesion, for application in glass fibre reinforced polymer (GFRP) composite materials. Electroadhesion uses high potential difference (~2-3 kV) between co-planar electrodes to generate temporary holding forces to both electrically conductive and nonconductive contact surfaces. Using a combination of established fabrication techniques, electroadhesive elements are co-cured within a composite host structure during manufacture. This provides an almost symbiotic relationship between the electroadhesive and the composite structure, with the electroadhesive providing an additional functionality, whilst the epoxy matrix material of the composite acts as a dielectric for the high voltage electrodes of the device. Silicone rubber coated devices have been shown to offer high shear load (85kPa) capability for GFRP components held together using this technique. Through careful control of the connection interface, we consider the incorporation of these devices within complete composite structures for additional functionality. The ability to vary the internal connectivity of structural elements could allow for incremental changes in connectivity between discrete sub-structures, potentially introducing variable stiffness to the global structure.

  1. Titanium-silicon carbide composite lattice structures

    NASA Astrophysics Data System (ADS)

    Moongkhamklang, Pimsiree

    Sandwich panel structures with stiff, strong face sheets and lightweight cellular cores are widely used for weight sensitive, bending dominated loading applications. The flexural stiffness and strength of a sandwich panel is determined by the stiffness, strength, thickness, and separation of the face sheets, and by the compressive and shear stiffness and strength of the cellular core. Panel performance can be therefore optimized using cores with high specific stiffness and strength. The specific stiffness and strength of all cellular materials depends upon the specific elastic modulus and strength of the material used to make the structure. The stiffest and strongest cores for ambient temperature applications utilize carbon fiber reinforced polymer (CFRP) honeycombs and lattice structures. Few options exist for lightweight sandwich panels intended for high temperature uses. High temperature alloys such as Ti-6A1-4V can be applied to SiC monofilaments to create very high specific modulus and strength fibers. These are interesting candidates for the cores of elevated temperature sandwich structures such as the skins of hypersonic vehicles. This dissertation explores the potential of sandwich panel concepts that utilize millimeter scale titanium matrix composite (TMC) lattice structures. A method has been developed for fabricating millimeter cell size cellular lattice structures with the square or diamond collinear truss topologies from 240 mum diameter Ti-6A1-4V coated SiC monofilaments (TMC monofilaments). Lattices with relative densities in the range 10% to 20% were manufactured and tested in compression and shear. Given the very high compressive strength of the TMC monofilaments, the compressive strengths of both the square and diamond lattices were dominated by elastic buckling of the constituent struts. However, under shear loading, some of the constituent struts of the lattices are subjected to tensile stresses and failure is then set by tensile failure of the

  2. Quantitative NDE of Composite Structures at NASA

    NASA Technical Reports Server (NTRS)

    Cramer, K. Elliott; Leckey, Cara A. C.; Howell, Patricia A.; Johnston, Patrick H.; Burke, Eric R.; Zalameda, Joseph N.; Winfree, William P.; Seebo, Jeffery P.

    2015-01-01

    The use of composite materials continues to increase in the aerospace community due to the potential benefits of reduced weight, increased strength, and manufacturability. Ongoing work at NASA involves the use of the large-scale composite structures for spacecraft (payload shrouds, cryotanks, crew modules, etc). NASA is also working to enable the use and certification of composites in aircraft structures through the Advanced Composites Project (ACP). The rapid, in situ characterization of a wide range of the composite materials and structures has become a critical concern for the industry. In many applications it is necessary to monitor changes in these materials over a long time. The quantitative characterization of composite defects such as fiber waviness, reduced bond strength, delamination damage, and microcracking are of particular interest. The research approaches of NASA's Nondestructive Evaluation Sciences Branch include investigation of conventional, guided wave, and phase sensitive ultrasonic methods, infrared thermography and x-ray computed tomography techniques. The use of simulation tools for optimizing and developing these methods is also an active area of research. This paper will focus on current research activities related to large area NDE for rapidly characterizing aerospace composites.

  3. Lithographically defined microporous carbon-composite structures

    SciTech Connect

    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.

  4. Thermostructural tailoring of fiber composite structures

    NASA Technical Reports Server (NTRS)

    Acquaviva, Thomas H.

    1992-01-01

    A significant area of interest in design of complex structures involves the study of multidisciplined problems. The coordination of several different intricate areas of study to obtain a particular design of a structure is a new and pressing area of research. In the past, each discipline would perform its task consecutively using the appropriate inputs from the other disciplines. This process usually required several time-consuming iterations to obtain a satisfactory design. The alternative pursued here is combining various participating disciplines and specified design requirements into a formal structural computer code. The main focus of this research is to develop a multidiscipline structural tailoring method for select composite structures and to demonstrate its application to specific areas. The development of an integrated computer program involves the coupling of three independent computer programs using an excutive module. This module will be the foundation for integrating a structural optimizer, a composites analyzer and a thermal analyzer. With the completion of the executive module, the first step was taken toward the evolution of multidiscipline software in the field of composite mechanics. Through the use of an array of cases involving a variety of objective functions/constraints and thermal-mechanical load conditions, it became evident that simple composite structures can be designed to a combined loads environment.

  5. Hierarchical Simulation of Hot Composite Structures

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Murthy, P. L. N.; Singhal, S. N.

    1993-01-01

    Computational procedures are described to simulate the thermal and mechanical behavior of high temperature metal matrix composites (HT-MMC) in the following three broad areas: (1) Behavior of HT-MMC's from micromechanics to laminate via Metal Matrix Composite Analyzer (METCAN), (2) tailoring of HT-MMC behavior for optimum specific performance via Metal Matrix Laminate Tailoring (MMLT), and (3) HT-MMC structural response for hot structural components via High Temperature Composite Analyzer (HITCAN). Representative results from each area are presented to illustrate the effectiveness of computational simulation procedures. The sample case results show that METCAN can be used to simulate material behavior such as strength, stress-strain response, and cyclic life in HTMMC's; MMLT can be used to tailor the fabrication process for optimum performance such as that for in-service load carrying capacity of HT-MMC's; and HITCAN can be used to evaluate static fracture and fatigue life of hot pressurized metal matrix composite rings.

  6. Shock Wave Structure in Particulate Composites

    NASA Astrophysics Data System (ADS)

    Rauls, Michael; Ravichandran, Guruswami

    2015-06-01

    Shock wave experiments are conducted on a particulate composite consisting of a polymethyl methacrylate (PMMA) matrix reinforced by glass beads. Such a composite with an impedance mismatch of 4.3 closely mimics heterogeneous solids of interest such as concrete and energetic materials. The composite samples are prepared using a compression molding process. The structure and particle velocity rise times of the shocks are examined using forward ballistic experiments. Reverse ballistic experiments are used to track how the interface density influences velocity overshoot above the steady state particle velocity. The effects of particle size (0.1 to 1 mm) and volume fraction of glass beads (30-40%) on the structure of the leading shock wave are investigated. It is observed that the rise time increases with increasing particle size and scales linearly for the range of particle sizes considered here. Results from numerical simulations using CTH are compared with experimental results to gain insights into wave propagation in heterogeneous particulate composites.

  7. Global Failure Modes in High Temperature Composite Structures

    NASA Technical Reports Server (NTRS)

    Knauss, W. G.

    1998-01-01

    Composite materials have been considered for many years as the major advance in the construction of energy efficient aerospace structures. Notable advances have been made in understanding the special design considerations that set composites apart from the usual "isotropic" engineering materials such as the metals. As a result, a number of significant engineering designs have been accomplished. However, one shortcoming of the currently favored composites is their relatively unforgiving behavior with respect to failure (brittleness) under seemingly mild impact conditions and large efforts are underway to rectify that situation, much along the lines of introducing thermoplastic matrix materials. Because of their relatively more pronounced (thermo) viscoelastic behavior these materials respond with "toughness" in fracture situations. From the point of view of applications requiring material strength, this property is highly desirable. This feature impacts several important and distinct engineering problems which have been' considered under this grant and cover the 1) effect of impact damage on structural (buckling) stability of composite panels, the 2) effect of time dependence on the progression of buckling instabilities, and the 3) evolution of damage and fracture at generic thickness discontinuities in structures. The latter topic has serious implications for structural stability problems (buckling failure in reinforced shell structures) as well as failure progression in stringer-reinforced shell structures. This grant has dealt with these issues. Polymer "toughness" is usually associated with uncrosslinked or thermo-plastic polymers. But, by comparison with their thermoset counterparts they tend to exhibit more pronounced time dependent material behavior; also, that time dependence can occur at lower temperatures which places restriction in the high temperature use of these "newer and tougher" materials that are not quite so serious with the thermoset matrix

  8. Damage Tolerance Characterisitics of Composite Sandwich Structures

    DTIC Science & Technology

    2000-02-01

    and very simplified modelling Unit of the EH-101 helicopter is made of a composite skeleton of the damage introduced by impact; second, the evaluation...the delamination boundary. The Multi Point Constraint If the delamination growth data from the teflon strip element of NASTRAN is used for modelling ...component level. These kinds of tests are composite sandwich structures used by the helicopter industry, carried out not only to verify load paths and

  9. Structure of weakly 2-dependent siphons

    NASA Astrophysics Data System (ADS)

    Chao, Daniel Yuh; Chen, Jiun-Ting

    2013-09-01

    Deadlocks arising from insufficiently marked siphons in flexible manufacturing systems can be controlled by adding monitors to each siphon - too many for large systems. Li and Zhou add monitors to elementary siphons only while controlling the rest of (called dependent) siphons by adjusting control depth variables of elementary siphons. Only a linear number of monitors are required. The control of weakly dependent siphons (WDSs) is rather conservative since only positive terms were considered. The structure for strongly dependent siphons (SDSs) has been studied earlier. Based on this structure, the optimal sequence of adding monitors has been discovered earlier. Better controllability has been discovered to achieve faster and more permissive control. The results have been extended earlier to S3PGR2 (systems of simple sequential processes with general resource requirements). This paper explores the structures for WDSs, which, as found in this paper, involve elementary resource circuits interconnecting at more than (for SDSs, exactly) one resource place. This saves the time to compute compound siphons, their complementary sets and T-characteristic vectors. Also it allows us (1) to improve the controllability of WDSs and control siphons and (2) to avoid the time to find independent vectors for elementary siphons. We propose a sufficient and necessary test for adjusting control depth variables in S3PR (systems of simple sequential processes with resources) to avoid the sufficient-only time-consuming linear integer programming test (LIP) (Nondeterministic Polynomial (NP) time complete problem) required previously for some cases.

  10. Composite electrode/electrolyte structure

    DOEpatents

    Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

    2004-01-27

    Provided is an electrode fabricated from highly electronically conductive materials such as metals, metal alloys, or electronically conductive ceramics. The electronic conductivity of the electrode substrate is maximized. Onto this electrode in the green state, a green ionic (e.g., electrolyte) film is deposited and the assembly is co-fired at a temperature suitable to fully densify the film while the substrate retains porosity. Subsequently, a catalytic material is added to the electrode structure by infiltration of a metal salt and subsequent low temperature firing. The invention allows for an electrode with high electronic conductivity and sufficient catalytic activity to achieve high power density in ionic (electrochemical) devices such as fuel cells and electrolytic gas separation systems.

  11. Density of biogas digestate depending on temperature and composition.

    PubMed

    Gerber, Mandy; Schneider, Nico

    2015-09-01

    Density is one of the most important physical properties of biogas digestate to ensure an optimal dimensioning and a precise design of biogas plant components like stirring devices, pumps and heat exchangers. In this study the density of biogas digestates with different compositions was measured using pycnometers at ambient pressure in a temperature range from 293.15 to 313.15K. The biogas digestates were taken from semi-continuous experiments, in which the marine microalga Nannochloropsis salina, corn silage and a mixture of both were used as feedstocks. The results show an increase of density with increasing total solid content and a decrease with increasing temperature. Three equations to calculate the density of biogas digestate were set up depending on temperature as well as on the total solid content, organic composition and elemental composition, respectively. All correlations show a relative deviation below 1% compared to experimental data.

  12. Compositional dependence of the band gap in Ga(NAsP) quantum well heterostructures

    SciTech Connect

    Jandieri, K. Ludewig, P.; Wegele, T.; Beyer, A.; Kunert, B.; Springer, P.; Baranovskii, S. D.; Koch, S. W.; Volz, K.; Stolz, W.

    2015-08-14

    We present experimental and theoretical studies of the composition dependence of the direct band gap energy in Ga(NAsP)/GaP quantum well heterostructures grown on either (001) GaP- or Si-substrates. The theoretical description takes into account the band anti-crossing model for the conduction band as well as the modification of the valence subband structure due to the strain resulting from the pseudomorphic epitaxial growth on the respective substrate. The composition dependence of the direct band gap of Ga(NAsP) is obtained for a wide range of nitrogen and phosphorus contents relevant for laser applications on Si-substrate.

  13. Structural evolution of chitosan-palygorskite composites and removal of aqueous lead by composite beads

    NASA Astrophysics Data System (ADS)

    Rusmin, Ruhaida; Sarkar, Binoy; Liu, Yanju; McClure, Stuart; Naidu, Ravi

    2015-10-01

    This paper investigates the structural evolution of chitosan-palygorskite (CP) composites in relation to variable mass ratios of their individual components. The composite beads' performance in lead (Pb) adsorption from aqueous solution was also examined. The composite beads were prepared through direct dispersion of chitosan and palygorskite at 1:1, 1:2 and 2:1 mass ratios (CP1, CP2 and C2P, respectively). Analyses by Fourier transform Infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the dependence of the composites' structural characteristics on their composition mass ratio. The chitosan-palygorskite composite beads exhibited a better Pb adsorption performance than the pristine materials (201.5, 154.5, 147.1, 27.7 and 9.3 mg g-1 for CP1, C2P, CP2, chitosan and palygorskite, respectively). Adsorption of Pb by CP1 and CP2 followed Freundlich isothermal model, while C2P fitted to Langmuir model. Kinetic studies showed that adsorption by all the composites fitted to the pseudo-second order model with pore diffusion also acting as a major rate governing step. The surface properties and specific interaction between chitosan and palygorskite in the composites were the most critical factors that influenced their capabilities in removing toxic metals from water.

  14. Annealing and structural properties of composite films

    NASA Astrophysics Data System (ADS)

    Kotov, L. N.; Ustyugov, V. A.; Vlasov, V. S.; Turkov, V. K.; Dianov, M. Yu; Antonets, I. V.; Kalinin, Yu E.; Sitnikov, A. V.; Golubev, E. A.

    2017-02-01

    The composite films were investigated by AFM methods before and after annealing. Topographic and phase-contrast AFM images of the composite films at different annealing temperature were obtained. The separate metal granules and larger-scale labyrinth-like formations were described. These formations appear by the process of the film growth, also by film annealing. Strong changes of the structural properties of the films are observed after the percolation transition. The significant changes of the structural properties are connected with nanostructural transformations in the metal granules topology and presence of metal crystal phase.

  15. Computational modeling and impact analysis of textile composite structures

    NASA Astrophysics Data System (ADS)

    Hur, Hae-Kyu

    response analyses of 2-D plain woven, 2-D braided and 3-D orthogonal woven composite structures featuring matrix cracking and exposed to time-dependent ballistic loads, (III) determination of the structural characteristics of the textile-layered composites and their degraded features under smeared and discrete cracks, and assessment of the implications of stiffness degradation on dynamic response to impact loads, and finally, (IV) the study of the micro-crack propagation in the textile/ceramic layered plates. A number of numerical models have been carried out to investigate the mechanical behavior of 2-D plain woven, 2-D braided and 3-D orthogonal woven textile composites with several geometrical representations, and study also the dynamic responses of multi-layered or textile layered composite structures subjected to ballistic impact penetrations with a developed in-house code.

  16. Investigation of Buckling Behavior of Composite Shell Structures with Cutouts

    NASA Astrophysics Data System (ADS)

    Arbelo, Mariano A.; Herrmann, Annemarie; Castro, Saullo G. P.; Khakimova, Regina; Zimmermann, Rolf; Degenhardt, Richard

    2015-12-01

    Thin-walled cylindrical composite shell structures can be applied in space applications, looking for lighter and cheaper launcher transport system. These structures are prone to buckling under axial compression and may exhibit sensitivity to geometrical imperfections. Today the design of such structures is based on NASA guidelines from the 1960's using a conservative lower bound curve generated from a database of experimental results. In this guideline the structural behavior of composite materials may not be appropriately considered since the imperfection sensitivity and the buckling load of shells made of such materials depend on the lay-up design. It is clear that with the evolution of the composite materials and fabrication processes this guideline must be updated and / or new design guidelines investigated. This need becomes even more relevant when cutouts are introduced to the structure, which are commonly necessary to account for access points and to provide clearance and attachment points for hydraulic and electric systems. Therefore, it is necessary to understand how a cutout with different dimensions affects the buckling load of a thin-walled cylindrical shell structure in combination with other initial geometric imperfections. In this context, this paper present some observations regarding the buckling load behavior vs. cutout size and radius over thickness ratio, of laminated composite curved panels and cylindrical shells, that could be applied in further recommendations, to allow identifying when the buckling of the structure is dominated by the presence of the cutout or by other initial imperfections.

  17. Enhanced Composites Integrity Through Structural Health Monitoring

    NASA Astrophysics Data System (ADS)

    Giurgiutiu, Victor; Soutis, Constantinos

    2012-10-01

    This paper discusses the topic of how the integrity of safety-critical structural composites can be enhanced by the use of structural health monitoring (SHM) techniques. The paper starts with a presentation of how the certification of flight-critical composite structures can be achieved within the framework of civil aviation safety authority requirements. Typical composites damage mechanisms, which make this process substantially different from that for metallic materials are discussed. The opportunities presented by the use of SHM techniques in future civil aircraft developments are explained. The paper then focuses on active SHM with piezoelectric wafer active sensors (PWAS). After reviewing the PWAS-based SHM options, the paper follows with a discussion of the specifics of guided wave propagation in composites and PWAS-tuning effects. The paper presents a number of experimental results for damage detection in simple flat unidirectional and quasi-isotropic composite specimens. Calibrated through holes of increasing diameter and impact damage of various energies and velocities are considered. The paper ends with conclusions and suggestions for further work.

  18. Composites technology for transport primary structure

    NASA Technical Reports Server (NTRS)

    Chen, Victor; Hawley, Arthur; Klotzsche, Max; Markus, Alan; Palmer, Ray

    1991-01-01

    The ACT contract activity being performed by the McDonnell Douglas Corporation is divided into two separate activities: one effort by Douglas Aircraft in Long Beach, California with a focus on Transport Primary Wing and Fuselage Structure, and the other effort by McDonnell Aircraft in St. Louis, Missouri with a focus on Advanced Combat Aircraft Center Wing-Fuselage Structure. This presentation is on the Douglas Aircraft Transport Structure portion of the ACT program called ICAPS - Innovative Composite Aircraft Primary Structure.

  19. Improved Joining of Metal Components to Composite Structures

    NASA Technical Reports Server (NTRS)

    Semmes, Edmund

    2009-01-01

    Systems requirements for complex spacecraft drive design requirements that lead to structures, components, and/or enclosures of a multi-material and multifunctional design. The varying physical properties of aluminum, tungsten, Invar, or other high-grade aerospace metals when utilized in conjunction with lightweight composites multiply system level solutions. These multi-material designs are largely dependent upon effective joining techAn improved method of joining metal components to matrix/fiber composite material structures has been invented. The method is particularly applicable to equipping such thin-wall polymer-matrix composite (PMC) structures as tanks with flanges, ceramic matrix composite (CMC) liners for high heat engine nozzles, and other metallic-to-composite attachments. The method is oriented toward new architectures and distributing mechanical loads as widely as possible in the vicinities of attachment locations to prevent excessive concentrations of stresses that could give rise to delaminations, debonds, leaks, and other failures. The method in its most basic form can be summarized as follows: A metal component is to be joined to a designated attachment area on a composite-material structure. In preparation for joining, the metal component is fabricated to include multiple studs projecting from the aforementioned face. Also in preparation for joining, holes just wide enough to accept the studs are molded into, drilled, or otherwise formed in the corresponding locations in the designated attachment area of the uncured ("wet') composite structure. The metal component is brought together with the uncured composite structure so that the studs become firmly seated in the holes, thereby causing the composite material to become intertwined with the metal component in the joining area. Alternately, it is proposed to utilize other mechanical attachment schemes whereby the uncured composite and metallic parts are joined with "z-direction" fasteners. The

  20. Durability-based design criteria for an automotive structural composite

    SciTech Connect

    Corum, J.M.; Battiste, R.L.; Brinkman, C.R.; Ren, W.; Ruggles, M.B.; Yahr, G.T.

    1998-11-01

    Before composite structures can be widely used in automotive applications, their long-term durability must be assured. The Durability of Lightweight Composite Structures Project at Oak Ridge National Laboratory was established by the US Department of Energy to help provide that assurance. The project is closely coordinated with the Automotive Composites Consortium. The experimentally-based, durability-driven design criteria described in this paper are the result of the initial project thrust. The criteria address a single reference composite, which is an SRIM (Structural Reaction Injection Molded) polyurethane, reinforced with continuous strand, swirl-mat E-glass fibers. The durability issues addressed include the effects of cyclic and sustained loadings, temperature, automotive fluid environments, and low-energy impacts (e.g., tool drops and roadway kickups) on strength, stiffness, and deformation. The criteria provide design analysis guidance, a multiaxial strength criterion, time-independent and time-dependent allowable stresses, rules for cyclic loading, and damage tolerance design guidance. Environmental degradation factors and the degrading effects of prior loadings are included. Efforts are currently underway to validate the criteria by application to a second random-glass-fiber composite. Carbon-fiber composites are also being addressed.

  1. Advanced composite structures. [metal matrix composites - structural design criteria for spacecraft construction materials

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A monograph is presented which establishes structural design criteria and recommends practices to ensure the design of sound composite structures, including composite-reinforced metal structures. (It does not discuss design criteria for fiber-glass composites and such advanced composite materials as beryllium wire or sapphire whiskers in a matrix material.) Although the criteria were developed for aircraft applications, they are general enough to be applicable to space vehicles and missiles as well. The monograph covers four broad areas: (1) materials, (2) design, (3) fracture control, and (4) design verification. The materials portion deals with such subjects as material system design, material design levels, and material characterization. The design portion includes panel, shell, and joint design, applied loads, internal loads, design factors, reliability, and maintainability. Fracture control includes such items as stress concentrations, service-life philosophy, and the management plan for control of fracture-related aspects of structural design using composite materials. Design verification discusses ways to prove flightworthiness.

  2. Lightning Protection for Composite Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Olson, G. O.

    1985-01-01

    Lightning protection system consisting of two layers of aluminum foil separated by layer of dielectric material protects graphite/epoxy composite structures on aircraft. Protective layer is secondarily applied lightning protection system, prime advantage of which is nullification of thermal and right angle effect of lightning arc attachment to graphite/epoxy laminate.

  3. Variable Complexity Optimization of Composite Structures

    NASA Technical Reports Server (NTRS)

    Haftka, Raphael T.

    2002-01-01

    The use of several levels of modeling in design has been dubbed variable complexity modeling. The work under the grant focused on developing variable complexity modeling strategies with emphasis on response surface techniques. Applications included design of stiffened composite plates for improved damage tolerance, the use of response surfaces for fitting weights obtained by structural optimization, and design against uncertainty using response surface techniques.

  4. Automated Tape Laying Machine for Composite Structures.

    DTIC Science & Technology

    The invention comprises an automated tape laying machine, for laying tape on a composite structure. The tape laying machine has a tape laying head...neatly cut. The automated tape laying device utilizes narrow width tape to increase machine flexibility and reduce wastage.

  5. Structure and Composition of the Grain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a crop with a wide range of genetic diversity, sorghum grain composition and structure can vary widely. Such variability can be of great benefit in supplying a diversity of uses but can also be a negative when viewed from the standpoint of uniformity. Despite sharing similarities to other cereals...

  6. Structural Design of Ares V Interstage Composite Structure

    NASA Technical Reports Server (NTRS)

    Sleigh, David W.; Sreekantamurthy, Thammaiah; Kosareo, Daniel N.; Martin, Robert A.; Johnson, Theodore F.

    2011-01-01

    Preliminary and detailed design studies were performed to mature composite structural design concepts for the Ares V Interstage structure as a part of NASA s Advanced Composite Technologies Project. Aluminum honeycomb sandwich and hat-stiffened composite panel structural concepts were considered. The structural design and analysis studies were performed using HyperSizer design sizing software and MSC Nastran finite element analysis software. System-level design trade studies were carried out to predict weight and margins of safety for composite honeycomb-core sandwich and composite hat-stiffened skin design concepts. Details of both preliminary and detailed design studies are presented in the paper. For the range of loads and geometry considered in this work, the hat-stiffened designs were found to be approximately 11-16 percent lighter than the sandwich designs. A down-select process was used to choose the most favorable structural concept based on a set of figures of merit, and the honeycomb sandwich design was selected as the best concept based on advantages in manufacturing cost.

  7. THERMAL SHADOWS AND COMPOSITIONAL STRUCTURE IN COMET NUCLEI

    SciTech Connect

    Guilbert-Lepoutre, Aurelie; Jewitt, David E-mail: jewitt@ucla.edu

    2011-12-10

    We use a fully three-dimensional thermal evolution model to examine the effects of a non-uniform surface albedo on the subsurface thermal structure of comets. Surface albedo markings cast 'thermal shadows' with strong lateral thermal gradients. Corresponding compositional gradients can be strong, especially if the crystallization of amorphous water ice is triggered in the hottest regions. We show that the spatial extent of the structure depends mainly on the obliquity, thermal conductivity, and heliocentric distance. In some circumstances, subsurface structure caused by the thermal shadows of surface features can be maintained for more than 10 Myr, the median transport time from the Kuiper Belt to the inner solar system. Non-uniform compositional structure can be an evolutionary product and does not necessarily imply that comets consist of building blocks accumulated in different regions of the protoplanetary disk.

  8. Temperature dependent spin structures in Hexaferrite crystal

    NASA Astrophysics Data System (ADS)

    Chao, Y. C.; Lin, J. G.; Chun, S. H.; Kim, K. H.

    2016-01-01

    In this work, the Hexaferrite Ba0.5Sr1.5Zn2Fe12O22 (BSZFO) is studied due to its interesting characteristics of long-wavelength spin structure. Ferromagnetic resonance (FMR) is used to probe the magnetic states of BSZFO single crystal and its temperature dependence behavior is analyzed by decomposing the multiple lines of FMR spectra into various phases. Distinguished phase transition is observed at 110 K for one line, which is assigned to the ferro(ferri)-magnetic transition from non-collinear to collinear spin state.

  9. Multidisciplinary tailoring of hot composite structures

    NASA Technical Reports Server (NTRS)

    Singhal, Surendra N.; Chamis, Christos C.

    1993-01-01

    A computational simulation procedure is described for multidisciplinary analysis and tailoring of layered multi-material hot composite engine structural components subjected to simultaneous multiple discipline-specific thermal, structural, vibration, and acoustic loads. The effect of aggressive environments is also simulated. The simulation is based on a three-dimensional finite element analysis technique in conjunction with structural mechanics codes, thermal/acoustic analysis methods, and tailoring procedures. The integrated multidisciplinary simulation procedure is general-purpose including the coupled effects of nonlinearities in structure geometry, material, loading, and environmental complexities. The composite material behavior is assessed at all composite scales, i.e., laminate/ply/constituents (fiber/matrix), via a nonlinear material characterization hygro-thermo-mechanical model. Sample tailoring cases exhibiting nonlinear material/loading/environmental behavior of aircraft engine fan blades, are presented. The various multidisciplinary loads lead to different tailored designs, even those competing with each other, as in the case of minimum material cost versus minimum structure weight and in the case of minimum vibration frequency versus minimum acoustic noise.

  10. Multidisciplinary tailoring of hot composite structures

    NASA Technical Reports Server (NTRS)

    Singhal, Surendra N.; Chamis, Christos C.

    1992-01-01

    A computational simulation procedure is described for multidisciplinary analysis and tailoring of multilayered multimaterial hot composite engine structural components subjected to simultaneous multiple discipline-specific thermal, structural, vibration, and acoustic loadings including the effect of aggressive environments. The simulation is based on a 3D finite element analysis technique in conjunction with structural mechanics codes, thermal/acoustic analysis methods, and tailoring procedures. The integrated multidisciplinary simulation procedure is general-purpose including the coupled effects of nonlinearities in structure geometry, material, loading, and environmental complexities. The composite material behavior is assessed at all composite scales, i.e., the laminate/ply/constituents (fiber/matrix), via a nonlinear material characterization hygro-thermomechanical model. Sample tailoring cases exhibiting nonlinear material/loading/environmental behavior of aircraft engine fan blades, are presented. The various multidisciplinary loadings lead to different tailored designs, even those opposite of each other, as in the case of minimum material cost versus minimum structure weight and in the case of minimum vibration frequency versus minimum acoustic noise.

  11. Cost-efficient manufacturing of composite structures

    NASA Technical Reports Server (NTRS)

    Freeman, W. Tom; Davis, John G.; Johnston, Norman J.

    1991-01-01

    The Advanced Composites Technology (ACT) program is seeking research breakthroughs that will allow structures made of graphite epoxy materials to replace metals in the wings and fuselages of future aircrafts. NASA's goals are to reduce acquisition cost by 20 to 25 percent, structural weight for a resized aircraft by 40 to 50 percent, and the number of parts by half compared to current production aluminum aircraft. The innovative structural concepts, materials, and fabrication techniques emerging from the ACT program are described, and the relationship between aerospace developments and industrial, commercial, and sporting goods applications are discussed.

  12. Health monitoring of a composite wingbox structure.

    PubMed

    Grondel, S; Assaad, J; Delebarre, C; Moulin, E

    2004-04-01

    This work was devoted to the development of a health monitoring system assigned to aerospace applications. Those applications concerned the detection of damaging impacts and debonding between stiffeners and composite skins, since they are the major causes of in-service damage of aircraft structures. The chosen health monitoring system was first based on the excitation and reception of Lamb waves along the structure by using thin piezoelectric transducers (active mode) and secondly on a continuous monitoring taking the same transducers used as acoustic emission sensors (passive mode). The composite specimen used was consistent with aircraft wingbox in terms of structure and loading. Several impacts with increasing energy increments were applied on the composite specimen. In passive mode, the study showed the ability of using the acoustic signature of an impact to detect possible damage. Moreover, the damage emergence in the case of damaging impact was confirmed in active mode. Further measurements during fatigue testing were performed. The aim was to demonstrate the ability of the system to monitor disbond growth between the stiffener and the composite skin. The sensitivity of the health monitoring system to the disbond growth was further demonstrated.

  13. Analysis of Smart Composite Structures Including Debonding

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Aditi; Seeley, Charles E.

    1997-01-01

    Smart composite structures with distributed sensors and actuators have the capability to actively respond to a changing environment while offering significant weight savings and additional passive controllability through ply tailoring. Piezoelectric sensing and actuation of composite laminates is the most promising concept due to the static and dynamic control capabilities. Essential to the implementation of these smart composites are the development of accurate and efficient modeling techniques and experimental validation. This research addresses each of these important topics. A refined higher order theory is developed to model composite structures with surface bonded or embedded piezoelectric transducers. These transducers are used as both sensors and actuators for closed loop control. The theory accurately captures the transverse shear deformation through the thickness of the smart composite laminate while satisfying stress free boundary conditions on the free surfaces. The theory is extended to include the effect of debonding at the actuator-laminate interface. The developed analytical model is implemented using the finite element method utilizing an induced strain approach for computational efficiency. This allows general laminate geometries and boundary conditions to be analyzed. The state space control equations are developed to allow flexibility in the design of the control system. Circuit concepts are also discussed. Static and dynamic results of smart composite structures, obtained using the higher order theory, are correlated with available analytical data. Comparisons, including debonded laminates, are also made with a general purpose finite element code and available experimental data. Overall, very good agreement is observed. Convergence of the finite element implementation of the higher order theory is shown with exact solutions. Additional results demonstrate the utility of the developed theory to study piezoelectric actuation of composite

  14. A Nonlinear Theory for Smart Composite Structures

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Aditi

    2002-01-01

    The paper discusses the following: (1) Development of a completely coupled thermo-piezoelectric-mechanical theory for the analysis of composite shells with segmented and distributed piezoelectric sensor/actuators and shape memory alloys. The higher order displacement theory will be used to capture the transverse shear effects in anisotropic composites. The original theory will be modified to satisfy the stress continuity at ply interfaces. (2) Development of a finite element technique to implement the mathematical model. (3) Investigation of the coupled structures/controls interaction problem to study the complex trade-offs associated with the coupled problem.

  15. Fabrication of graphite/polyimide composite structures.

    NASA Technical Reports Server (NTRS)

    Varlas, M.

    1972-01-01

    Selection of graphite/polyimide composite as a prime candidate for high-temperature structural applications involving long-duration temperature environments of 400 to 600 F. A variety of complex graphite/polyimide components has been fabricated, using a match-metal die approach developed for making fiber-reinforced resin composites. Parts produced include sections of a missile adapter skin flange, skin frame section, and I-beam and hat-section stringers, as well as unidirectional (0 deg) and plus or minus 45 deg oriented graphite/polyimide tubes in one-, two-, and six-inch diameters.

  16. Elastic waves in structurally chiral composites

    SciTech Connect

    Yang, Shiuhkuang.

    1990-01-01

    Elastic wave propagation through structurally chiral (handed) media was studied. The primary objectives are to construct structurally chiral composites and to characterize their properties. Structurally chiral composites are constructed by stacking identical uniaxial plates, whose consecutive symmetric axes describe either a right- or a left-handed spiral. A matrix representation method is used to solve the elastic wave propagation in such layered composites. Numerical computation of the plane wave reflection and transmission characteristics for chiral arrangements are compared with those for the non-chiral one. It is concluded that the co-polarized characteristics are unaffected by the structural chirality, while the cross-polarized reflected and transmitted fields are greatly influenced by it. Numerical modeling is also applied for the real samples. The polarization ellipse of the transmitted field of each sample is calculated. To verify the form chirality, four glass-reinforced chiral and non-chiral composite samples are made from helix tape, molded, debulked, and cured individually under identical temperature and pressure histories. The spiral composites are characterized using shear and longitudinal wave transducers in ultrasonic experiments. Both the material properties and the polarization ellipse of the transmitted field of each sample are measured. It is proved conclusively that left and right handedness in the microstructures of a material rotates the plane of polarization of a propagating shear wave in the opposite directions. Thus it is now possible to say that by reducing the length scale of the handed microstructures tone more appropriate to its propagating wavelength, a medium is obtained that gives rise to effects similar to optical radar and optical dichroism.

  17. Load Diffusion in Composite and Smart Structures

    NASA Technical Reports Server (NTRS)

    Horgan, Cornelius O.; Ambur, D. (Technical Monitor); Nemeth, M. P. (Technical Monitor)

    2003-01-01

    The research carried out here builds on our previous NASA supported research on the general topic of edge effects and load diffusion in composite structures. Further fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for the multi-functional large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures. Some specific problems recently considered were those of end effects in smart materials and structures, study of the stress response of pressurized linear piezoelectric cylinders for both static and steady rotating configurations, an analysis of the effect of pre-stressing and pre-polarization on the decay of end effects in piezoelectric solids and investigation of constitutive models for hardening rubber-like materials. Our goal in the study of load diffusion is the development of readily applicable results for the decay lengths in terms of non-dimensional material and geometric parameters. Analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and assessing results from finite element analyses.

  18. Composite Blade Structural Analyzer (COBSTRAN) demonstration manual

    NASA Technical Reports Server (NTRS)

    Aiello, Robert A.

    1989-01-01

    The input deck setup is described for a computer code, composite blade structural analyzer (COBSTRAN) which was developed for the design and analysis of composite turbofan and turboprop blades and also for composite wind turbine blades. This manual is intended for use in conjunction with the COBSTRAN user's manual. Seven demonstration problems are described with pre- and postprocessing input decks. Modeling of blades which are solid thru-the-thickness and also aircraft wing airfoils with internal spars is shown. Corresponding NASTRAN and databank input decks are also shown. Detail descriptions of each line of the pre- and post-processing decks is provided with reference to the Card Groups defined in the user's manual. A dictionary of all program variables and terms used in this manual may be found in Section 6 of the user's manual.

  19. Self Healing Composite for Aircraft's Structural Application

    NASA Astrophysics Data System (ADS)

    Teoh, S. H.; Chia, H. Y.; Lee, M. S.; Nasyitah, A. J. N.; Luqman, H. B. S. M.; Nurhidayah, S.; Tan, Willy. C. K.

    When one cuts himself, it is amazing to watch how quickly the body acts to mend the wound. Immediately, the body works to pull the skin around the cut back together. The concept of repair by bleeding of enclosed functional agents serves as the biomimetic inspiration of synthetic self repair systems. Such synthetic self repair systems are based on advancement in polymeric materials; the process of human thrombosis is the inspiration for the application of self healing fibres within the composite materials. Results based on flexural 3 point bend test on the prepared samples have shown that the doubled layer healed hollow fibre laminate subjected to a healing regime of 3 weeks has a healed strength increase of 27% compared to the damaged baseline laminate. These results gave us confidence that there is a great potential to adopt such self healing mechanism on actual composite parts like in aircraft's composite structures.

  20. Automated web service composition supporting conditional branch structures

    NASA Astrophysics Data System (ADS)

    Wang, Pengwei; Ding, Zhijun; Jiang, Changjun; Zhou, Mengchu

    2014-01-01

    The creation of value-added services by automatic composition of existing ones is gaining a significant momentum as the potential silver bullet in service-oriented architecture. However, service composition faces two aspects of difficulties. First, users' needs present such characteristics as diversity, uncertainty and personalisation; second, the existing services run in a real-world environment that is highly complex and dynamically changing. These difficulties may cause the emergence of nondeterministic choices in the process of service composition, which has gone beyond what the existing automated service composition techniques can handle. According to most of the existing methods, the process model of composite service includes sequence constructs only. This article presents a method to introduce conditional branch structures into the process model of composite service when needed, in order to satisfy users' diverse and personalised needs and adapt to the dynamic changes of real-world environment. UML activity diagrams are used to represent dependencies in composite service. Two types of user preferences are considered in this article, which have been ignored by the previous work and a simple programming language style expression is adopted to describe them. Two different algorithms are presented to deal with different situations. A real-life case is provided to illustrate the proposed concepts and methods.

  1. Advanced Technology Composite Fuselage-Structural Performance

    NASA Technical Reports Server (NTRS)

    Walker, T. H.; Minguet, P. J.; Flynn, B. W.; Carbery, D. J.; Swanson, G. D.; Ilcewicz, L. B.

    1997-01-01

    Boeing is studying the technologies associated with the application of composite materials to commercial transport fuselage structure under the NASA-sponsored contracts for Advanced Technology Composite Aircraft Structures (ATCAS) and Materials Development Omnibus Contract (MDOC). This report addresses the program activities related to structural performance of the selected concepts, including both the design development and subsequent detailed evaluation. Design criteria were developed to ensure compliance with regulatory requirements and typical company objectives. Accurate analysis methods were selected and/or developed where practical, and conservative approaches were used where significant approximations were necessary. Design sizing activities supported subsequent development by providing representative design configurations for structural evaluation and by identifying the critical performance issues. Significant program efforts were directed towards assessing structural performance predictive capability. The structural database collected to perform this assessment was intimately linked to the manufacturing scale-up activities to ensure inclusion of manufacturing-induced performance traits. Mechanical tests were conducted to support the development and critical evaluation of analysis methods addressing internal loads, stability, ultimate strength, attachment and splice strength, and damage tolerance. Unresolved aspects of these performance issues were identified as part of the assessments, providing direction for future development.

  2. Performance analysis of bonded composite doublers on aircraft structures

    SciTech Connect

    Roach, D.

    1995-08-01

    Researchers contend that composite repairs (or structural reinforcement doublers) offer numerous advantages over metallic patches including corrosion resistance, light weight, high strength, elimination of rivets, and time savings in installation. Their use in commercial aviation has been stifled by uncertainties surrounding their application, subsequent inspection and long-term endurance. The process of repairing or reinforcing airplane structures is time consuming and the design is dependent upon an accompanying stress and fatigue analysis. A repair that is too stiff may result in a loss of fatigue life, continued growth of the crack being repaired, and the initiation of a new flaw in the undesirable high stress field around the patch. Uncertainties in load spectrums used to design repairs exacerbates these problems as does the use of rivets to apply conventional doublers. Many of these repair or structural reinforcement difficulties can be addressed through the use of composite doublers. Primary among unknown entities are the effects of non-optimum installations and the certification of adequate inspection procedures. This paper presents on overview of a program intended to introduce composite doubler technology to the US commercial aircraft fleet. In this project, a specific composite application has been chosen on an L-1011 aircraft in order to focus the tasks on application and operation issues. Through the use of laboratory test structures and flight demonstrations on an in-service L-1011 airplane, this study is investigating composite doubler design, fabrication, installation, structural integrity, and non-destructive evaluation. In addition to providing an overview of the L-1011 project, this paper focuses on a series of fatigue and strength tests which have been conducted in order to study the damage tolerance of composite doublers. Test results to-date are presented.

  3. Crashworthiness simulation of composite automotive structures

    SciTech Connect

    Botkin, M E; Johnson, N L; Simunovic, S; Zywicz, E

    1998-06-01

    In 1990 the Automotive Composites Consortium (ACC) began the investigation of crash worthiness simulation methods for composite materials. A contract was given to Livermore Software Technology Corporation (LSTC) to implement a new damage model in LS-DYNA3DTM specifically for composite structures. This model is in LS-DYNA3DTM and is in use by the ACC partners. In 1994 USCAR, a partnership of American auto companies, entered into a partnership called SCAAP (Super Computing Automotive Applications Partnership) for the express purpose of working with the National Labs on computational oriented research. A CRADA (Cooperative Research and Development Agreement) was signed with Lawrence Livermore National Laboratory, Oak Ridge National Laboratory, Sandia National Laboratory, Argonne National Laboratory, and Los Alamos National Laboratory to work in three distinctly different technical areas, one of which was composites material modeling for crash worthiness. Each Laboratory was assigned a specific modeling task. The ACC was responsible for the technical direction of the composites project and provided all test data for code verification. All new models were to be implemented in DYNA3D and periodically distributed to all partners for testing. Several new models have been developed and implemented. Excellent agreement has been shown between tube crush simulation and experiments.

  4. Coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures

    NASA Technical Reports Server (NTRS)

    Mcknight, R. L.; Huang, H.; Hartle, M.

    1992-01-01

    Accomplishments are described for the third years effort of a 5-year program to develop a methodology for coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures. These accomplishments include: (1) structural analysis capability specialized for graded composite structures including large deformation and deformation position eigenanalysis technologies; (2) a thermal analyzer specialized for graded composite structures; (3) absorption of electromagnetic waves by graded composite structures; and (4) coupled structural thermal/electromagnetic analysis of graded composite structures.

  5. Thermal inspection of composite honeycomb structures

    NASA Astrophysics Data System (ADS)

    Zalameda, Joseph N.; Parker, F. Raymond

    2014-05-01

    Composite honeycomb structures continue to be widely used in aerospace applications due to their low weight and high strength advantages. Developing nondestructive evaluation (NDE) inspection methods are essential for their safe performance. Pulsed thermography is a commonly used technique for composite honeycomb structure inspections due to its large area and rapid inspection capability. Pulsed thermography is shown to be sensitive for detection of face sheet impact damage and face sheet to core disbond. Data processing techniques, using principal component analysis to improve the defect contrast, are presented. In addition, limitations to the thermal detection of the core are investigated. Other NDE techniques, such as computed tomography X-ray and ultrasound, are used for comparison to the thermography results.

  6. Computational Simulation of Composite Structural Fatigue

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon; Chamis, Christos C. (Technical Monitor)

    2005-01-01

    Progressive damage and fracture of composite structures subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via computational simulation. Constituent material properties, stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for composites. Damage initiation, growth, accumulation, and propagation to fracture due to monotonically increasing static and cyclic loads are included in the simulations. Results show the number of cycles to failure at different temperatures and the damage progression sequence during different degradation stages. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

  7. Out of plane analysis for composite structures

    NASA Technical Reports Server (NTRS)

    Paul, P. C.; Saff, C. R.; Sanger, Kenneth B.; Mahler, M. A.; Kan, Han Pin; Kautz, Edward F.

    1990-01-01

    Simple two dimensional analysis techniques were developed to aid in the design of strong joints for integrally stiffened/bonded composite structures subjected to out of plane loads. It was found that most out of plane failures were due to induced stresses arising from rapid changes in load path direction or geometry, induced stresses due to changes in geometry caused by buckling, or direct stresses produced by fuel pressure or bearing loads. While the analysis techniques were developed to address a great variety of out of plane loading conditions, they were primarily derived to address the conditions described above. The methods were developed and verified using existing element test data. The methods were demonstrated using the data from a test failure of a high strain wingbox that was designed, built, and tested under a previous program. Subsequently, a set of design guidelines were assembled to assist in the design of safe, strong integral composite structures using the analysis techniques developed.

  8. Thermal Inspection of Composite Honeycomb Structures

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Parker, F. Raymond

    2014-01-01

    Composite honeycomb structures continue to be widely used in aerospace applications due to their low weight and high strength advantages. Developing nondestructive evaluation (NDE) inspection methods are essential for their safe performance. Pulsed thermography is a commonly used technique for composite honeycomb structure inspections due to its large area and rapid inspection capability. Pulsed thermography is shown to be sensitive for detection of face sheet impact damage and face sheet to core disbond. Data processing techniques, using principal component analysis to improve the defect contrast, are presented. In addition, limitations to the thermal detection of the core are investigated. Other NDE techniques, such as computed tomography X-ray and ultrasound, are used for comparison to the thermography results.

  9. Computational Simulation of Composite Structural Fatigue

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon

    2004-01-01

    Progressive damage and fracture of composite structures subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via computational simulation. Constituent material properties, stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for composites. Damage initiation, growth, accumulation, and propagation to fracture due to monotonically increasing static and cyclic loads are included in the simulations. Results show the number of cycles to failure at different temperatures and the damage progression sequence during different degradation stages. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

  10. Time-dependent deformation of titanium metal matrix composites

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.; Bahei-El-din, Y. A.; Mirdamadi, M.

    1995-01-01

    A three-dimensional finite element program called VISCOPAC was developed and used to conduct a micromechanics analysis of titanium metal matrix composites. The VISCOPAC program uses a modified Eisenberg-Yen thermo-viscoplastic constitutive model to predict matrix behavior under thermomechanical fatigue loading. The analysis incorporated temperature-dependent elastic properties in the fiber and temperature-dependent viscoplastic properties in the matrix. The material model was described and the necessary material constants were determined experimentally. Fiber-matrix interfacial behavior was analyzed using a discrete fiber-matrix model. The thermal residual stresses due to the fabrication cycle were predicted with a failed interface, The failed interface resulted in lower thermal residual stresses in the matrix and fiber. Stresses due to a uniform transverse load were calculated at two temperatures, room temperature and an elevated temperature of 650 C. At both temperatures, a large stress concentration was calculated when the interface had failed. The results indicate the importance of accuracy accounting for fiber-matrix interface failure and the need for a micromechanics-based analytical technique to understand and predict the behavior of titanium metal matrix composites.

  11. Failure Analysis of Composite Structure Materials.

    DTIC Science & Technology

    1986-05-01

    listed in order of preference, based on applicability, reliability, cost , and sample requirements. Figure 5-4. Failure Analysis Technique...development of a methodology in which optical analysis is used to increase the time and cost effectiveness of analyzing failed composite material struc...regarding the integrity of the bond. Accurate bondline defect information was achieved in such structures utilizing a transportable californium -252 (2 5 2

  12. Bioinspired twisted composites based on Bouligand structures

    NASA Astrophysics Data System (ADS)

    Pinto, F.; Iervolino, O.; Scarselli, G.; Ginzburg, D.; Meo, M.

    2016-04-01

    The coupling between structural support and protection makes biological systems an important source of inspiration for the development of advanced smart composite structures. In particular, some particular material configurations can be implemented into traditional composites in order to improve their impact resistance and the out-of-plane properties, which represents one of the major weakness of commercial carbon fibres reinforced polymers (CFRP) structures. Based on this premise, a three-dimensional twisted arrangement shown in a vast multitude of biological systems (such as the armoured cuticles of Scarabei, the scales of Arapaima Gigas and the smashing club of Odontodactylus Scyllarus) has been replicated to develop an improved structural material characterised by a high level of in-plane isotropy and a higher interfacial strength generated by the smooth stiffness transition between each layer of fibrils. Indeed, due to their intrinsic layered nature, interlaminar stresses are one of the major causes of failure of traditional CFRP and are generated by the mismatch of the elastic properties between plies in a traditional laminate. Since the energy required to open a crack or a delamination between two adjacent plies is due to the difference between their orientations, the gradual angle variation obtained by mimicking the Bouligand Structures could improve energy absorption and the residual properties of carbon laminates when they are subjected to low velocity impact event. Two different bioinspired laminates were manufactured following a double helicoidal approach and a rotational one and were subjected to a complete test campaign including low velocity impact loading and compared to a traditional quasi-isotropic panel. Fractography analysis via X-Ray tomography was used to understand the mechanical behaviour of the different laminates and the residual properties were evaluated via Compression After Impact (CAI) tests. Results confirmed that the biological

  13. Structural dynamic analysis of composite beams

    NASA Astrophysics Data System (ADS)

    Suresh, J. K.; Venkatesan, C.; Ramamurti, V.

    1990-12-01

    In the treatment of the structural dynamic problem of composite materials, two alternate types of formulations, based on the elastic modulus and compliance quantities, exist in the literature. The definitions of the various rigidities are observed to differ in these two approaches. Following these two types of formulation, the structural dynamic characteristics of a composite beam are analyzed. The results of the analysis are compared with those available in the literature. Based on the comparison, the influence of the warping function in defining the coupling terms in the modulus approach and also on the natural frequencies of the beam has been identified. It is found from the analysis that, in certain cases, the difference between the results of the two approaches is appreciable. These differences may be attributed to the constraints imposed on the deformation and flexibility of the beam by the choice of the description of the warping behaviour. Finally, the influence of material properties on the structural dynamic characteristics of the beam is studied for different composites for various angles of orthotropy.

  14. Development of thermoplastic composite aircraft structures

    NASA Technical Reports Server (NTRS)

    Renieri, Michael P.; Burpo, Steven J.; Roundy, Lance M.; Todd, Stephanie A.; Kim, H. J.

    1992-01-01

    Efforts focused on the use of thermoplastic composite materials in the development of structural details associated with an advanced fighter fuselage section with applicability to transport design. In support of these designs, mechanics developments were conducted in two areas. First, a dissipative strain energy approach to material characterization and failure prediction, developed at the Naval Research Laboratory, was evaluated as a design/analysis tool. Second, a finite element formulation for thick composites was developed and incorporated into a lug analysis method which incorporates pin bending effects. Manufacturing concepts were developed for an upper fuel cell cover. A detailed trade study produced two promising concepts: fiber placement and single-step diaphragm forming. Based on the innovative design/manufacturing concepts for the fuselage section primary structure, elements were designed, fabricated, and structurally tested. These elements focused on key issues such as thick composite lugs and low cost forming of fastenerless, stiffener/moldine concepts. Manufacturing techniques included autoclave consolidation, single diaphragm consolidation (SDCC) and roll-forming.

  15. Sensor devices comprising field-structured composites

    DOEpatents

    Martin, James E.; Hughes, Robert C.; Anderson, Robert A.

    2001-02-27

    A new class of sensor devices comprising field-structured conducting composites comprising a textured distribution of conducting magnetic particles is disclosed. The conducting properties of such field-structured materials can be precisely controlled during fabrication so as to exhibit a large change in electrical conductivity when subject to any environmental influence which changes the relative volume fraction. Influences which can be so detected include stress, strain, shear, temperature change, humidity, magnetic field, electromagnetic radiation, and the presence or absence of certain chemicals. This behavior can be made the basis for a wide variety of sensor devices.

  16. The Effect of Temperature Dependent Material Nonlinearities on the Response of Piezoelectric Composite Plates

    NASA Technical Reports Server (NTRS)

    Lee, Ho-Jun; Saravanos, Dimitris A.

    1997-01-01

    Previously developed analytical formulations for piezoelectric composite plates are extended to account for the nonlinear effects of temperature on material properties. The temperature dependence of the composite and piezoelectric properties are represented at the material level through the thermopiezoelectric constitutive equations. In addition to capturing thermal effects from temperature dependent material properties, this formulation also accounts for thermal effects arising from: (1) coefficient of thermal expansion mismatch between the various composite and piezoelectric plies and (2) pyroelectric effects on the piezoelectric material. The constitutive equations are incorporated into a layerwise laminate theory to provide a unified representation of the coupled mechanical, electrical, and thermal behavior of smart structures. Corresponding finite element equations are derived and implemented for a bilinear plate element with the inherent capability to model both the active and sensory response of piezoelectric composite laminates. Numerical studies are conducted on a simply supported composite plate with attached piezoceramic patches under thermal gradients to investigate the nonlinear effects of material property temperature dependence on the displacements, sensory voltages, active voltages required to minimize thermal deflections, and the resultant stress states.

  17. Advanced composite combustor structural concepts program

    NASA Technical Reports Server (NTRS)

    Sattar, M. A.; Lohmann, R. P.

    1984-01-01

    An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.

  18. Temperature and composition dependence of crystal structures and magnetic and electronic properties of the double perovskites La2-xSrxCoIrO6 (0≤x≤2)

    NASA Astrophysics Data System (ADS)

    Narayanan, N.; Mikhailova, D.; Senyshyn, A.; Trots, D. M.; Laskowski, R.; Blaha, P.; Schwarz, K.; Fuess, H.; Ehrenberg, H.

    2010-07-01

    X-ray, synchrotron, and neutron powder diffraction techniques were combined to investigate the evolution of crystal structure and physical properties of La2-xSrxCoIrO6 with temperature and composition x . The following sequence of first- and second-order phase transitions is observed in this system, induced by increasing Sr content and temperature: P21/n↔P21/n+I2/m↔I2/m↔I4/m↔Fm3¯m . The low-temperature magnetic structures are characterized by the propagation vector k=(0,0,0) for x=0 , k=(1/2,0,1/2) for x=1 , and k=(0,1/2,1/2) or k=(1/2,0,1/2) for 1.5 and 2. Different noncollinear magnetic structures are concluded from the combination of magnetization measurements and neutron powder diffraction. Resistivity measurements reveal that the whole series behaves like nonmetals with electronic transport described by a combination of thermal activation and variable range hopping. Band gaps determined by electronic structure calculations agree very well with the experimental data for x=0 and 1, and the calculated occupation of the d bands of Co and Ir are in good agreement with a transition IS/HS-Co2+/LS-Ir4+→HS-Co3+/LS-Ir5+ with increasing Sr content.

  19. Thick-walled carbon composite multifunctional structures

    NASA Astrophysics Data System (ADS)

    Haake, John M.; Jacobs, Jack H.; McIlroy, Bruce E.

    1997-06-01

    Satellite programs are moving in the direction of smaller and lighter structures. Technological advances have permitted more sophisticated equipment to be consolidated into compact spaces. Micro-satellites, between 10 and 100 kg, will incorporate micro-electric devices into the lay-up of the satellite structure. These structures will be designed to carry load, provide thermal control, enhance damping, and include integrated passive electronics. These multifunctional structures offer lighter weight, reduced volume, and a 'smarter' overall package for incorporation of sensors, electronics, fiber optics, powered appendages or active components. McDonnell Douglas Corporation (MDC) has applied technology from the synthesis and processing of intelligent cost effective structures (SPICES) and independent research and development (IRAD) programs to the modular instrument support system (MISS) for multifunctional space structures and micro-satellites. The SPICES program was funded by the Defense Advanced Research Projects Agency (DARPA) to develop affordable manufacturing processes for smart materials to be used in vibration control, and the MISS program was funded by NASA-Langley. The MISS program was conceived to develop concepts and techniques to make connections between different multifunctional structures. MDA fabricated a trapezoidal carbon composite structure out of IM7/977-3 tape prepreg. Flex circuits, thermal and optical conduits were embedded to realize a utility modular connector. These provide electrical, thermal, optical and mechanical connections between micro- satellite components. A quick disconnect mount was also developed to accommodate a variety of devices such as solar arrays, power sources, thermal transfer and vibration control modules.

  20. 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

  1. Cooled Ceramic Matrix Composite Propulsion Structures Demonstrated

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Dickens, Kevin W.

    2005-01-01

    NASA's Next Generation Launch Technology (NGLT) Program has successfully demonstrated cooled ceramic matrix composite (CMC) technology in a scramjet engine test. This demonstration represented the world s largest cooled nonmetallic matrix composite panel fabricated for a scramjet engine and the first cooled nonmetallic composite to be tested in a scramjet facility. Lightweight, high-temperature, actively cooled structures have been identified as a key technology for enabling reliable and low-cost space access. Tradeoff studies have shown this to be the case for a variety of launch platforms, including rockets and hypersonic cruise vehicles. Actively cooled carbon and CMC structures may meet high-performance goals at significantly lower weight, while improving safety by operating with a higher margin between the design temperature and material upper-use temperature. Studies have shown that using actively cooled CMCs can reduce the weight of the cooled flow-path component from 4.5 to 1.6 lb/sq ft and the weight of the propulsion system s cooled surface area by more than 50 percent. This weight savings enables advanced concepts, increased payload, and increased range. The ability of the cooled CMC flow-path components to operate over 1000 F hotter than the state-of-the-art metallic concept adds system design flexibility to space-access vehicle concepts. Other potential system-level benefits include smaller fuel pumps, lower part count, lower cost, and increased operating margin.

  2. Measuring time-dependent diffusion in polymer matrix composites

    SciTech Connect

    Pilli, Siva Prasad; Smith, Lloyd V.; Shutthanandan, V.

    2014-11-01

    Moisture plays a significant role in influencing the mechanical behavior and long-term durability of polymer matrix composites (PMC’s). The common methods used to determine the moisture diffusion coefficients of PMCs are based on the solution of Fickian diffusion in the one-dimensional domain. Fick’s Law assumes that equilibrium between the material surface and the external vapor is established instantaneously. A time dependent boundary condition has been shown to improve correlation with some bulk diffusion measurements, but has not been validated experimentally. The surface moisture content in a Toray 800S/3900-2B toughened quasi-isotropic laminate system, [0/±60]s, was analyzed experimentally using Nuclear Reaction Analysis (NRA). It was found that the surface moisture content showed a rapid increase to an intermediate concentration C0, followed by a slow linear increase to the saturation level.

  3. Measuring time-dependent diffusion in polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Pilli, Siva P.; Smith, Lloyd V.; Vaithiyalingam, Shutthanandan

    2014-11-01

    Moisture plays a significant role in influencing the mechanical behavior and long-term durability of polymer matrix composites (PMCs). The common methods used to determine the moisture diffusion coefficients of PMCs are based on the solution of Fickian diffusion in the one-dimensional domain. Fick's Law assumes that equilibrium between the material surface and the external vapor is established instantaneously. A time-dependent boundary condition has been shown to improve correlation with some bulk diffusion measurements, but has not been validated experimentally. The surface moisture content in a Toray 800S/3900-2B toughened quasi-isotropic laminate system, [0/±60] s , was analyzed experimentally using Nuclear Reaction Analysis (NRA). It was found that the surface moisture content showed a rapid increase to an intermediate concentration C 0, followed by a slow linear increase to the saturation level.

  4. Assembly induced delaminations in composite structures

    NASA Technical Reports Server (NTRS)

    Goering, J.; Bohlmann, R.; Wanthal, S.; Kautz, E.; Neri, Lawrence M.

    1992-01-01

    Experimental and analytical studies of the development of delaminations around fastener holes in composite structures are presented. This type of delamination is known to occur in composite skins that are mechanically fastened to a poorly mating substructure. Results of an experimental study to determine the resistance of laminates to the initiation of assembly induced delaminations and the residual strength of assembly damaged coupons are presented for AS4/3501-6, IM7/8551-7A, and AS4/PEEK material systems. A survey of existing analytical models for predicting the residual strength and stability of delaminations is presented, and the development of a new model for predicting the initiation of delaminations around a fastener hole is outlined. The fastener hole damage initiation model utilizes a finite element based Fourier series solution, and is validated through comparisons of analytical and experimental results.

  5. Size-Dependent Structure Relations between Nanotubes and Encapsulated Nanocrystals.

    PubMed

    Eliseev, Andrei A; Falaleev, Nikolay S; Verbitskiy, Nikolay I; Volykhov, Andrei A; Yashina, Lada V; Kumskov, Andrei S; Zhigalina, Victoria G; Vasiliev, Alexander L; Lukashin, Alexey V; Sloan, Jeremy; Kiselev, Nikolay A

    2017-02-08

    The structural organization of compounds in a confined space of nanometer-scale cavities is of fundamental importance for understanding the basic principles for atomic structure design at the nanolevel. Here, we explore size-dependent structure relations between one-dimensional PbTe nanocrystals and carbon nanotube containers in the diameter range of 2.0-1.25 nm using high-resolution transmission electron microscopy and ab initio calculations. Upon decrease of the confining volume, one-dimensional crystals reveal gradual thinning, with the structure being cut from the bulk in either a <110> or a <100> growth direction until a certain limit of ∼1.3 nm. This corresponds to the situation when a stoichiometric (uncharged) crystal does not fit into the cavity dimensions. As a result of the in-tube charge compensation, one-dimensional superstructures with nanometer-scale atomic density modulations are formed by a periodic addition of peripheral extra atoms to the main motif. Structural changes in the crystallographic configuration of the composites entail the redistribution of charge density on single-walled carbon nanotube walls and the possible appearance of the electron density wave. The variation of the potential attains 0.4 eV, corresponding to charge density fluctuations of 0.14 e/atom.

  6. Optimal design of a composite structure

    NASA Technical Reports Server (NTRS)

    Graesser, D. L.; Zabinsky, Z. B.; Tuttle, M. E.; Kim, G. I.

    1993-01-01

    This paper presents a design methodology for a laminated composite stiffened panel, subjected to multiple in-plane loads and bending moments. Design variables include the skin and stiffener ply orientation angles and stiffener geometry variables. Optimum designs are sought which minimize structural weight and satisfy mechanical performance requirements. Two types of mechanical performance requirements are placed on the panel, maximum strain and minimum strength. Minimum weight designs are presented which document that the choice of mechanical performance requirements cause changes in the optimum design. The effects of lay-up constraints which limit the ply angles to user specified values, such as symmetric or quasi-isotropic laminates, are also investigated.

  7. Anisotropic fiber alignment in composite structures

    DOEpatents

    Graham, Alan L.; Mondy, Lisa A.; Guell, David C.

    1993-01-01

    High strength material composite structures are formed with oriented fibers to provide controlled anisotropic fibers. Fibers suspended in non-dilute concentrations (e.g., up to 20 volume percent for fibers having an aspect ratio of 20) in a selected medium are oriented by moving an axially spaced array of elements in the direction of desired fiber alignment. The array elements are generally perpendicular to the desired orientation. The suspension medium may also include sphere-like particles where the resulting material is a ceramic.

  8. Load Diffusion in Composite and Smart Structures

    NASA Technical Reports Server (NTRS)

    Horgan, C. O.

    2003-01-01

    The research carried out here builds on our previous NASA supported research on the general topic of edge effects and load diffusion in composite structures. Further fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for the multi-functional large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures. Some specific problems recently considered were those of end effects in smart materials and structures, study of the stress response of pressurized linear piezoelectric cylinders for both static and steady rotating configurations, an analysis of the effect of pre-stressing and pre-polarization on the decay of end effects in piezoelectric solids and investigation of constitutive models for hardening rubber-like materials. Our goal in the study of load diffusion is the development of readily applicable results for the decay lengths in terms of non-dimensional material and geometric parameters. Analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and assessing results from finite element analyses. The decay behavior of stresses and other field quantities provides a significant aid towards this process. The analysis is also amenable to parameter study with a large parameter space and should be useful in structural tailoring studies. Special purpose analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and in assessing results from general purpose finite element analyses. For example, a rational basis is needed in choosing where to use three-dimensional to two-dimensional transition finite elements in analyzing stiffened plates and shells. The decay behavior of stresses and other field quantities furnished by

  9. Photospheric composition and structure in white dwarfs

    NASA Astrophysics Data System (ADS)

    Barstow, M. A.

    1993-12-01

    One of the central mysteries of white dwarf studies has been the nature and abundance of trace elements in the atmospheres of these stars. It had been thought that the dominant trace element in otherwise pure hydrogen DA white dwarf atmospheres was helium. However, some spectroscopic and theoretical evidence suggested that, at least in some stars, heavier elements may be important. Prior to the launch of ROSAT the questions regarding the atmospheric composition of DA white dwarfs in general remained unresolved. The ROSAT mission has provided EUV and X-ray data for a large sample of DA white dwarfs with which we can study their photospheric composition and structure through the effect of trace opacity sources on the emergent fluxes. Contrary to expectations little (if any) helium is found and the main sources of opacity appear to be trace heavy elements. Support for these conclusions is found in recent EUV and far-UV spectra of several stars. However, photometric data do not allow us to determine the abundance of the individual elements and observations with the extreme ultraviolet explorer satellite (EUVE) spectrometers will be essential for detailed composition measurements.

  10. Dynamic Probabilistic Instability of Composite Structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2009-01-01

    A computationally effective method is described to evaluate the non-deterministic dynamic instability (probabilistic dynamic buckling) of thin composite shells. The method is a judicious combination of available computer codes for finite element, composite mechanics and probabilistic structural analysis. The solution method is incrementally updated Lagrangian. It is illustrated by applying it to thin composite cylindrical shell subjected to dynamic loads. Both deterministic and probabilistic buckling loads are evaluated to demonstrate the effectiveness of the method. A universal plot is obtained for the specific shell that can be used to approximate buckling loads for different load rates and different probability levels. Results from this plot show that the faster the rate, the higher the buckling load and the shorter the time. The lower the probability, the lower is the buckling load for a specific time. Probabilistic sensitivity results show that the ply thickness, the fiber volume ratio and the fiber longitudinal modulus, dynamic load and loading rate are the dominant uncertainties in that order.

  11. Structure and Composition of the Lunar Crust

    NASA Astrophysics Data System (ADS)

    Spudis, P. D.; Bussey, D. B. J.; Hawke, B. R.

    1999-01-01

    Since the first return of lunar samples indicated that global differentiation of the Moon had occurred, numerous models of crustal structure have been proposed. With the completion of the first global reconnaissance mapping by Clementine and Lunar Prospector, we are now in position to re-evaluate crustal structure and composition at a global scale. Although this is a difficult and complex task, and one requiring significant study, some first-order results are apparent now and are quite telling. We here summarize our current view of crustal structure and identify some required knowledge to better understand the origin and evolution of the lunar crust. Wood et al. attempted to estimate the amount of plagioclase in the crust, based on the average elevation difference between mare and highlands and some simple assumptions about anorthosite and basalt as responsible for the principal lunar rock types. Later, more complex models emerged, involving layered crusts of feldspathic material over more basaltic material or a laterally variable crust, with Mg-suite plutons intruding a grossly anorthositic crust. Later models attempted to reconcile these contrasting styles by incorporating both features. In part, crustal structure was inferred by the envisioned mode of crustal formation. A decade-long debate on the reality of the lunar "magma ocean," stimulated by the provocative notion of Walker that the Moon never had a magma ocean, and the recognition that the anorthosites and Mg suite probably recorded different and unrelated magmatic events. Such a scenario leaves much about crustal structure an open question, but allows for both lateral and vertical heterogeneity, thus accommodating both principal crustal models. Global maps of Fe , Ti, and Th both confirm old ideas and create new problems. It is clear that vast areas of the lunar highlands are extremely low in Fe, consistent with a significant amount of anorthosite. Such a distribution supports the magma ocean. However

  12. NDE of composite structures using microwave time reversal imaging

    NASA Astrophysics Data System (ADS)

    Mukherjee, Saptarshi; Tamburrino, Antonello; Udpa, Lalita; Udpa, Satish

    2016-02-01

    Composite materials are being increasingly used to replace metals, partially or completely, in aerospace, shipping and automotive industries because of their light weight, corrosion resistance, and mechanical strength. Integrity of these materials may be compromised during manufacturing or due to impact damage during usage, resulting in defects such as porosity, delamination, cracks and disbonds. Microwave NDE techniques have the ability to propagate through composite materials, without suffering much attenuation. The scattered fields depend on the dielectric properties of the medium, and hence provide information about the structural integrity of these materials. Time Reversal focusing is based on the fact that when a wave solution is reversed in time and back propagated it refocuses back at the source. This paper presents a model based parametric study of time reversal principles with microwave data in composite materials. A two dimensional FDTD model is developed to implement the forward and time reversed electromagnetic wave propagation in a test geometry comprising metal-composite structures. Simulation results demonstrate the feasibility of this approach to detect and characterize different defects.

  13. Critical joints in large composite aircraft structure

    NASA Technical Reports Server (NTRS)

    Nelson, W. D.; Bunin, B. L.; Hart-Smith, L. J.

    1983-01-01

    A program was conducted at Douglas Aircraft Company to develop the technology for critical structural joints of composite wing structure that meets design requirements for a 1990 commercial transport aircraft. The prime objective of the program was to demonstrate the ability to reliably predict the strength of large bolted composite joints. Ancillary testing of 180 specimens generated data on strength and load-deflection characteristics which provided input to the joint analysis. Load-sharing between fasteners in multirow bolted joints was computed by the nonlinear analysis program A4EJ. This program was used to predict strengths of 20 additional large subcomponents representing strips from a wing root chordwise splice. In most cases, the predictions were accurate to within a few percent of the test results. In some cases, the observed mode of failure was different than anticipated. The highlight of the subcomponent testing was the consistent ability to achieve gross-section failure strains close to 0.005. That represents a considerable improvement over the state of the art.

  14. Chemical compositions, methods of making the chemical compositions, and structures made from the chemical compositions

    DOEpatents

    Yang, Lei; Cheng, Zhe; Liu, Ze; Liu, Meilin

    2015-01-13

    Embodiments of the present disclosure include chemical compositions, structures, anodes, cathodes, electrolytes for solid oxide fuel cells, solid oxide fuel cells, fuel cells, fuel cell membranes, separation membranes, catalytic membranes, sensors, coatings for electrolytes, electrodes, membranes, and catalysts, and the like, are disclosed.

  15. Natural Kenaf Fiber Reinforced Composites as Engineered Structural Materials

    NASA Astrophysics Data System (ADS)

    Dittenber, David B.

    theory, finite element method, and Castigliano's method in unidirectional tension and compression, but are less accurate for the more bond-dependent flexural and shear properties. With the acknowledged NFRP matrix bonding issues, the over-prediction of these theoretical models indicates that the flexural stiffness of the kenaf composite may be increased by up to 40% if a better bond between the fiber and matrix can be obtained. The sustainability of NFRPs was examined from two perspectives: environmental and socioeconomic. While the kenaf fibers themselves possess excellent sustainability characteristics, costing less while possessing a lesser environmental impact than the glass fibers, the vinyl ester resin used in the composites is environmentally hazardous and inflated the cost and embodied energy of the composite SIPs. Consistent throughout all the designs was a correlation between the respective costs of the raw materials and the respective environmental impacts. The socioeconomic study looked at the sustainability of natural fiber reinforced composite materials as housing materials in developing countries. A literature study on the country of Bangladesh, where the fibers in this study were grown, showed that the jute and kenaf market would benefit from the introduction of a value-added product like natural fiber composites. The high rate of homeless and inadequately housed in Bangladesh, as well as in the US and throughout the rest of the world, could be somewhat alleviated if a new, affordable, and durable material were introduced. While this study found that natural fiber composites possess sufficient mechanical properties to be adopted as primary structural members, the two major remaining hurdles needing to be overcome before natural fiber composites can be adopted as housing materials are the cost and sustainability of the resin system and the moisture resistance/durability of the fibers. (Abstract shortened by UMI.)

  16. Time-Dependent Deformation Modelling for a Chopped-Glass Fiber Composite for Automotive Durability Design Criteria

    SciTech Connect

    Ren, W

    2001-08-24

    Time-dependent deformation behavior of a polymeric composite with chopped-glass-fiber reinforcement was investigated for automotive applications, The material under stress was exposed to representative automobile service environments. Results show that environment has substantial effects on time-dependent deformation behavior of the material. The data were analyzed and experimentally-based models developed for the time-dependent deformation behavior as a basis for automotive structural durability design criteria.

  17. Compositional dependence of sulfur speciation in Terrestrial and Martian magmas

    NASA Astrophysics Data System (ADS)

    Nash, William; Wood, Bernard; Smythe, Duane

    2016-04-01

    The capacity of magmas to transport sulfur from mantle to crust strongly influences a planet's surface chemistry. Sulfur is perhaps exceptional among the elements in the diversity of it's chemical speciation, exhibiting four redox species at geologically relevant conditions: sulfide (2-), elemental sulfur (0), sulfite (4+) and sulphate (6+). Furthermore, the solubility of sulfur in a magma (and hence the magma's capacity for delivering mantle-derived sulfur to the crust) depends critically on it's oxidation state. Our aim with this experimental study was to quantitatively determine the chemical speciation of sulfur within several common magmas, as a function of oxygen fugacity (fO2). We have performed a series of experiments on six sulfur-bearing silicate melts, which together represent a broad range of naturally occurring compositions: two putative Martian basalts, two terrestrial MORBs (one primitive, one evolved), an andesite, and a dacite. These melts were equilibrated together (at one-atmosphere pressure, 1300°C) with various CO-CO2-SO2 gas mixtures, which imposed a range of fO2s. This range spanned -2 to +1.6 log units (relative to the Quartz-Fayalite-Magnetite or QFM buffer), and the step-size was 0.25 log units. The quenched glasses were analyzed by X-ray Absorption Spectroscopy (specifically XANES) at the Diamond synchrotron (UK), and the spectra obtained were used to determine the species of sulfur present in each glass. The chemical composition of each glass (including their sulfur contents) was characterized by electron-probe microanalysis. Despite the generally low concentrations of sulfur in our glasses (never exceeding 0.24 wt%), we have clearly resolved the crossover between reduced (S2-) and oxidized (S6+) species for three of our basalts. The other three melts yielded more noisy XANES spectra, and as a result their redox crossovers are visible, but less clearly resolved. For every melt composition, the redox crossover is a continuous (though

  18. Capacitance-based damage detection sensing for aerospace structural composites

    NASA Astrophysics Data System (ADS)

    Bahrami, P.; Yamamoto, N.; Chen, Y.; Manohara, H.

    2014-04-01

    Damage detection technology needs improvement for aerospace engineering application because detection within complex composite structures is difficult yet critical to avoid catastrophic failure. Damage detection is challenging in aerospace structures because not all the damage detection technology can cover the various defect types (delamination, fiber fracture, matrix crack etc.), or conditions (visibility, crack length size, etc.). These defect states are expected to become even more complex with future introduction of novel composites including nano-/microparticle reinforcement. Currently, non-destructive evaluation (NDE) methods with X-ray, ultrasound, or eddy current have good resolutions (< 0.1 mm), but their detection capabilities is limited by defect locations and orientations and require massive inspection devices. System health monitoring (SHM) methods are often paired with NDE technologies to signal out sensed damage, but their data collection and analysis currently requires excessive wiring and complex signal analysis. Here, we present a capacitance sensor-based, structural defect detection technology with improved sensing capability. Thin dielectric polymer layer is integrated as part of the structure; the defect in the structure directly alters the sensing layer's capacitance, allowing full-coverage sensing capability independent of defect size, orientation or location. In this work, capacitance-based sensing capability was experimentally demonstrated with a 2D sensing layer consisting of a dielectric layer sandwiched by electrodes. These sensing layers were applied on substrate surfaces. Surface indentation damage (~1mm diameter) and its location were detected through measured capacitance changes: 1 to 250 % depending on the substrates. The damage detection sensors are light weight, and they can be conformably coated and can be part of the composite structure. Therefore it is suitable for aerospace structures such as cryogenic tanks and rocket

  19. Structural Health Monitoring for Impact Damage in Composite Structures.

    SciTech Connect

    Roach, Dennis P.; Raymond Bond; Doug Adams

    2014-08-01

    Composite structures are increasing in prevalence throughout the aerospace, wind, defense, and transportation industries, but the many advantages of these materials come with unique challenges, particularly in inspecting and repairing these structures. Because composites of- ten undergo sub-surface damage mechanisms which compromise the structure without a clear visual indication, inspection of these components is critical to safely deploying composite re- placements to traditionally metallic structures. Impact damage to composites presents one of the most signi fi cant challenges because the area which is vulnerable to impact damage is generally large and sometimes very dif fi cult to access. This work seeks to further evolve iden- ti fi cation technology by developing a system which can detect the impact load location and magnitude in real time, while giving an assessment of the con fi dence in that estimate. Fur- thermore, we identify ways by which impact damage could be more effectively identi fi ed by leveraging impact load identi fi cation information to better characterize damage. The impact load identi fi cation algorithm was applied to a commercial scale wind turbine blade, and results show the capability to detect impact magnitude and location using a single accelerometer, re- gardless of sensor location. A technique for better evaluating the uncertainty of the impact estimates was developed by quantifying how well the impact force estimate meets the assump- tions underlying the force estimation technique. This uncertainty quanti fi cation technique was found to reduce the 95% con fi dence interval by more than a factor of two for impact force estimates showing the least uncertainty, and widening the 95% con fi dence interval by a fac- tor of two for the most uncertain force estimates, avoiding the possibility of understating the uncertainty associated with these estimates. Linear vibration based damage detection tech- niques were investigated in the

  20. Delamination Assessment Tool for Spacecraft Composite Structures

    NASA Astrophysics Data System (ADS)

    Portela, Pedro; Preller, Fabian; Wittke, Henrik; Sinnema, Gerben; Camanho, Pedro; Turon, Albert

    2012-07-01

    Fortunately only few cases are known where failure of spacecraft structures due to undetected damage has resulted in a loss of spacecraft and launcher mission. However, several problems related to damage tolerance and in particular delamination of composite materials have been encountered during structure development of various ESA projects and qualification testing. To avoid such costly failures during development, launch or service of spacecraft, launcher and reusable launch vehicles structures a comprehensive damage tolerance verification approach is needed. In 2009, the European Space Agency (ESA) initiated an activity called “Delamination Assessment Tool” which is led by the Portuguese company HPS Lda and includes academic and industrial partners. The goal of this study is the development of a comprehensive damage tolerance verification approach for launcher and reusable launch vehicles (RLV) structures, addressing analytical and numerical methodologies, material-, subcomponent- and component testing, as well as non-destructive inspection. The study includes a comprehensive review of current industrial damage tolerance practice resulting from ECSS and NASA standards, the development of new Best Practice Guidelines for analysis, test and inspection methods and the validation of these with a real industrial case study. The paper describes the main findings of this activity so far and presents a first iteration of a Damage Tolerance Verification Approach, which includes the introduction of novel analytical and numerical tools at an industrial level. This new approach is being put to the test using real industrial case studies provided by the industrial partners, MT Aerospace, RUAG Space and INVENT GmbH

  1. Compression Strength of Composite Primary Structural Components

    NASA Technical Reports Server (NTRS)

    Johnson, Eric R.

    1998-01-01

    Research conducted under NASA Grant NAG-1-537 focussed on the response and failure of advanced composite material structures for application to aircraft. Both experimental and analytical methods were utilized to study the fundamental mechanics of the response and failure of selected structural components subjected to quasi-static loads. Most of the structural components studied were thin-walled elements subject to compression, such that they exhibited buckling and postbuckling responses prior to catastrophic failure. Consequently, the analyses were geometrically nonlinear. Structural components studied were dropped-ply laminated plates, stiffener crippling, pressure pillowing of orthogonally stiffened cylindrical shells, axisymmetric response of pressure domes, and the static crush of semi-circular frames. Failure of these components motivated analytical studies on an interlaminar stress postprocessor for plate and shell finite element computer codes, and global/local modeling strategies in finite element modeling. These activities are summarized in the following section. References to literature published under the grant are listed on pages 5 to 10 by a letter followed by a number under the categories of journal publications, conference publications, presentations, and reports. These references are indicated in the text by their letter and number as a superscript.

  2. Development of a composite satellite structure for FORTE

    SciTech Connect

    Grastataro, C.I.; Butler, T.A.; Smith, B.G.; Thompson, T.C.

    1995-04-01

    The Los Alamos National Laboratory (LANL) in partnership with Composite Optics Incorporated (COI) has advanced the development of low-cost, lightweight, composite technology for use in small satellite structures, in this case, for the Fast On-Orbit Recording of Transient Events (FORTE) satellite mission. The use of advanced composites in space applications is well developed, but the application of an all-composite satellite structure has not been achieved until now. This paper investigates the application of composite technology in the design of an all-composite spacecraft structure for small satellites. Engineering analysis and test results obtained from the development of the spacecraft engineering model are also presented.

  3. Compositional dependence of hematopoietic stem cells expansion on bioceramic composite scaffolds for bone tissue engineering.

    PubMed

    Mishra, Sarika; Rajyalakshmi, A; Balasubramanian, K

    2012-09-01

    Bioceramics are although well known for their osteoinductive and osseointegrative properties in bone tissue regeneration, yet, they are inappropriate for load bearing applications due to inadequate mechanical strength. In this article, the authors report the expansion of hematopoietic stem cells (HSCs) on as-synthesized composite scaffolds from hydroxyapatite and β-tricalcium phosphate for bone tissue engineering, in an adequate load-bearing application. The physical, structural, and mechanical properties of the composite scaffolds have been examined and correlated with the in vitro adhesion pattern of HSCs. The results indicated that the response of HSCs varies with change in the stoichiometry of composite scaffolds. The H2T2 scaffolds have exhibited the highest expansion of CD34+ cells and long-term culture initiating cells when compared with other stoichiometries. The results suggest that H2T2 composite can be a potential strategic bone-graft substitute in contrast with monolithic bioceramics, serving a dual role of bioresorbability and enhanced load-bearing capacity.

  4. Structural integrity of engineering composite materials: a cracking good yarn.

    PubMed

    Beaumont, Peter W R; Soutis, Costas

    2016-07-13

    Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a 'fracture safe design' is immense. Fitness considerations for long-life implementation of large composite structures include understanding phenomena such as impact, fatigue, creep and stress corrosion cracking that affect reliability, life expectancy and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined, and takes service duty into account. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.

  5. Structural integrity of engineering composite materials: a cracking good yarn

    PubMed Central

    Beaumont, Peter W. R.

    2016-01-01

    Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a ‘fracture safe design’ is immense. Fitness considerations for long-life implementation of large composite structures include understanding phenomena such as impact, fatigue, creep and stress corrosion cracking that affect reliability, life expectancy and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined, and takes service duty into account. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242293

  6. Advances in Computational Stability Analysis of Composite Aerospace Structures

    SciTech Connect

    Degenhardt, R.; Araujo, F. C. de

    2010-09-30

    European aircraft industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents different advances from the area of computational stability analysis of composite aerospace structures which contribute to that field. For stringer stiffened panels main results of the finished EU project COCOMAT are given. It investigated the exploitation of reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. For unstiffened cylindrical composite shells a proposal for a new design method is presented.

  7. Composition dependence of the structural chemistry and magnetism of Ca{sub 2.5}Sr{sub 0.5}(Ga,Co){sub 1+} {sub x} Mn{sub 2-} {sub x} O{sub 8}

    SciTech Connect

    Allix, Mathieu; Battle, Peter D. . E-mail: peter.battle@chem.ox.ac.uk; Frampton, Philip P.C.; Rosseinsky, Matthew J.; Ruiz-Bustos, Rocio

    2006-03-15

    Polycrystalline samples of bilayered brownmillerite-like Ca{sub 2.5}Sr{sub 0.5}GaCo{sub 0.15}Mn{sub 1.85}O{sub 8} and Ca{sub 2.5}Sr{sub 0.5}Ga{sub 1.2}Mn{sub 1.8}O{sub 8} have been prepared and characterised by magnetometry and neutron diffraction over a wide temperature range. The structural chemistry and magnetic properties are compared to those of Ca{sub 2.5}Sr{sub 0.5}GaMn{sub 2}O{sub 8}. Ga enrichment has a significant effect on the former but not on the latter, whereas changes in both occur when paramagnetic Co{sup 3+} cations enter the parent phase on the 4-coordinate sites. The coupling between the environment around the 4-coordinate cations and the transition to an antiferromagnetic ordered state that was observed in Ca{sub 2.5}Sr{sub 0.5}GaMn{sub 2}O{sub 8} is not apparent in the cation-substituted compositions, although both show long-range antiferromagnetic order at low temperatures.

  8. Growth phase-dependent composition of the Helicobacter pylori exoproteome.

    PubMed

    Snider, Christina A; Voss, Bradley J; McDonald, W Hayes; Cover, Timothy L

    2016-01-01

    Helicobacter pylori colonizes the human stomach and is associated with an increased risk of gastric cancer and peptic ulcer disease. Analysis of H. pylori protein secretion is complicated by the occurrence of bacterial autolysis. In this study, we analyzed the exoproteome of H. pylori at multiple phases of bacterial growth and identified 74 proteins that are selectively released into the extracellular space. These include proteins known to cause alterations in host cells, antigenic proteins, and additional proteins that have not yet been studied in any detail. The composition of the H. pylori exoproteome is dependent on the phase of bacterial growth. For example, the proportional abundance of the vacuolating toxin VacA in culture supernatant is higher during late growth phases than early growth phases, whereas the proportional abundance of many other proteins is higher during early growth phases. We detected marked variation in the subcellular localization of putative secreted proteins within soluble and membrane fractions derived from intact bacteria. By providing a comprehensive view of the H. pylori exoproteome, these results provide new insights into the array of secreted H. pylori proteins that may cause alterations in the gastric environment.

  9. Probabilistic Assessment of Fracture Progression in Composite Structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Minnetyan, Levon; Mauget, Bertrand; Huang, Dade; Addi, Frank

    1999-01-01

    This report describes methods and corresponding computer codes that are used to evaluate progressive damage and fracture and to perform probabilistic assessment in built-up composite structures. Structural response is assessed probabilistically, during progressive fracture. The effects of design variable uncertainties on structural fracture progression are quantified. The fast probability integrator (FPI) is used to assess the response scatter in the composite structure at damage initiation. The sensitivity of the damage response to design variables is computed. The methods are general purpose and are applicable to stitched and unstitched composites in all types of structures and fracture processes starting from damage initiation to unstable propagation and to global structure collapse. The methods are demonstrated for a polymer matrix composite stiffened panel subjected to pressure. The results indicated that composite constituent properties, fabrication parameters, and respective uncertainties have a significant effect on structural durability and reliability. Design implications with regard to damage progression, damage tolerance, and reliability of composite structures are examined.

  10. Fuselage structure using advanced technology fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Robinson, R. K.; Tomlinson, H. M. (Inventor)

    1982-01-01

    A fuselage structure is described in which the skin is comprised of layers of a matrix fiber reinforced composite, with the stringers reinforced with the same composite material. The high strength to weight ratio of the composite, particularly at elevated temperatures, and its high modulus of elasticity, makes it desirable for use in airplane structures.

  11. Age-dependent morphological and compositional variations on Ceres

    NASA Astrophysics Data System (ADS)

    Jaumann, Ralf

    2016-04-01

    Extended smooth plains cover the interior of a number of craters on Ceres. Smooth plains appear on different topographic levels associated with pits and flow-like features that overrun crater rims. The material forming these plains also ponds in depressions and smaller craters and cover the pre-existing surface creating distinct geological boundaries. Ikapati crater shows smooth plains on different topographic levels associated with pits and flow-like features that overrun crater rims. The material forming these plains, ponds in depressions and smaller craters and cover the pre-existing surface creating a distinct geological boundary. The interior of Occator also exhibits extended plains of ponded material, multiple flows originating from the center overwhelming the mass wasting deposits from the rim, dome-like features, vents cracks and fissures. Furthermore, crater densities on Occator's floor are lower than those on the ejecta blanket indicating a post-impact formation age of the flows. The flows to the northeast appear to originate from the central region and move slightly uphill. This indicates either a feeding zone that pushes the flows forward by supplying low-viscosity material or a depression of the crater center, possibly after discharging a subsurface reservoir. The plains and flows as well as some areas surrounding the craters appear spectrally blue. Both plains and flow material are characterized in camera and spectrometer visible spectra by a slightly negative slope with a gradual drop off up to 10% in reflectance from 0.5μm to 1μm. Although the spectral variations in the visible are subtle, they are clearly expressed in the color ratio composite. The crater densities of 20 locations across the surface of Ceres with different spectral behavior were analyzed in order to investigate the age dependence of spectral surface features. The results indicate that bluish material is mainly associated with the youngest impact craters on Ceres (< 0.5 Ga) while

  12. Advanced fiber-composite hybrids--A new structural material

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    Introduction of metal foil as part of matrix and fiber composite, or ""sandwich'', improves strength and stiffness for multidirectional loading, improves resistance to cyclic loading, and improves impact and erosion resistance of resultant fiber-composite hybrid structure.

  13. Progress in patch repair of aerospace composite structures

    NASA Astrophysics Data System (ADS)

    Hou, Weiguo; Zhang, Weifang; Tang, Qingyun

    2011-11-01

    With the rapid application of the composite structure in the aerospace industry, more load-bearing structures and components are used with composites instead of conventional engineering materials. However, the composite structures are inevitably suffered damages in the complex environment, the composites structures repair become more important in the airplane maintenance. This paper describes the composites patch repair progress. Firstly, the flaws and damages concerned to composite structures are concluded, and also the repair principles are presented. Secondly, the advantages and disadvantages for different repair methods are analyzed, as well as the different bonded repair and their applicability to different structures is discussed. According the recent research in theory and experiment, the scarf repair effects under different parameters are analyzed. Finally, the failure mechanisms of repair structure are discussed, and some prospects are put forward.

  14. Progress in patch repair of aerospace composite structures

    NASA Astrophysics Data System (ADS)

    Hou, Weiguo; Zhang, Weifang; Tang, Qingyun

    2012-04-01

    With the rapid application of the composite structure in the aerospace industry, more load-bearing structures and components are used with composites instead of conventional engineering materials. However, the composite structures are inevitably suffered damages in the complex environment, the composites structures repair become more important in the airplane maintenance. This paper describes the composites patch repair progress. Firstly, the flaws and damages concerned to composite structures are concluded, and also the repair principles are presented. Secondly, the advantages and disadvantages for different repair methods are analyzed, as well as the different bonded repair and their applicability to different structures is discussed. According the recent research in theory and experiment, the scarf repair effects under different parameters are analyzed. Finally, the failure mechanisms of repair structure are discussed, and some prospects are put forward.

  15. A new rate-dependent unidirectional composite model - Application to panels subjected to underwater blast

    NASA Astrophysics Data System (ADS)

    Wei, Xiaoding; de Vaucorbeil, Alban; Tran, Phuong; Espinosa, Horacio D.

    2013-06-01

    In this study, we developed a finite element fluid-structure interaction model to understand the deformation and failure mechanisms of both monolithic and sandwich composite panels. A new failure criterion that includes strain-rate effects was formulated and implemented to simulate different damage modes in unidirectional glass fiber/matrix composites. The laminate model uses Hashin's fiber failure criterion and a modified Tsai-Wu matrix failure criterion. The composite moduli are degraded using five damage variables, which are updated in the post-failure regime by means of a linear softening law governed by an energy release criterion. A key feature in the formulation is the distinction between fiber rupture and pull-out by introducing a modified fracture toughness, which varies from a fiber tensile toughness to a matrix tensile toughness as a function of the ratio of longitudinal normal stress to effective shear stress. The delamination between laminas is modeled by a strain-rate sensitive cohesive law. In the case of sandwich panels, core compaction is modeled by a crushable foam plasticity model with volumetric hardening and strain-rate sensitivity. These constitutive descriptions were used to predict deformation histories, fiber/matrix damage patterns, and inter-lamina delamination, for both monolithic and sandwich composite panels subjected to underwater blast. The numerical predictions were compared with experimental observations. We demonstrate that the new rate dependent composite damage model captures the spatial distribution and magnitude of damage significantly more accurately than previously developed models.

  16. Reliability and life prediction of ceramic composite structures at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Duffy, Stephen F.; Gyekenyesi, John P.

    1994-01-01

    Methods are highlighted that ascertain the structural reliability of components fabricated of composites with ceramic matrices reinforced with ceramic fibers or whiskers and subject to quasi-static load conditions at elevated temperatures. Each method focuses on a particular composite microstructure: whisker-toughened ceramics, laminated ceramic matrix composites, and fabric reinforced ceramic matrix composites. In addition, since elevated service temperatures usually involve time-dependent effects, a section dealing with reliability degradation as a function of load history has been included. A recurring theme throughout this chapter is that even though component failure is controlled by a sequence of many microfailure events, failure of ceramic composites will be modeled using macrovariables.

  17. On the design of structural components using materials with time-dependent properties

    NASA Technical Reports Server (NTRS)

    Rodriguez, Pedro I.

    1993-01-01

    The application of the elastic-viscoelastic correspondence principle is presented as a design tool for structural design engineers for composite material applications. The classical problem of cantilever beams is used as the illustration problem. Both closed-form and approximate numerical solutions are presented for several different problems. The application of the collocation method is presented as a viable and simple design tool to determine the time-dependent behavior and response of viscoelastic composite beams under load.

  18. A Design Tool for Robust Composite Structures

    DTIC Science & Technology

    2010-06-01

    related goal is to compare the blast response of Dyneema® laminates with that of a carbon fiber reinforced polymer ( CFRP ) composite. (iii) To identify...embedded Dyneema® composite layers, both below and above the ballistic limit. 16 6. Hybrid Dyneema®/Carbon Fiber Reinforced Polymer Matrix Composites...of Dyneema® fibers to carbon fiber reinforced polymer ( CFRP ) composites. The study focuses specifically on 3D orthogonal weaves with carbon employed

  19. Braided Composite Technologies for Rotorcraft Structures

    NASA Technical Reports Server (NTRS)

    Jessie, Nathan

    2015-01-01

    A&P Technology has developed a braided material approach for fabricating lightweight, high-strength hybrid gears for aerospace drive systems. The conventional metallic web was replaced with a composite element made from A&P's quasi-isotropic braid. The 0deg, +/-60deg braid architecture was chosen so that inplane stiffness properties and strength would be nearly equal in all directions. The test results from the Phase I Small Spur Gear program demonstrated satisfactory endurance and strength while providing a 20 percent weight savings. (Greater weight savings is anticipated with structural optimization.) The hybrid gears were subjected to a proof-of-concept test of 1 billion cycles in a gearbox at 10,000 revolutions per minute and 490 in-lb torque with no detectable damage to the gears. After this test the maximum torque capability was also tested, and the static strength capability of the gears was 7x the maximum operating condition. Additional proof-of-concept tests are in progress using a higher oil temperature, and a loss-of-oil test is planned. The success of Phase I led to a Phase II program to develop, fabricate, and optimize full-scale gears, specifically Bull Gears. The design of these Bull Gears will be refined using topology optimization, and the full-scale Bull Gears will be tested in a full-scale gear rig. The testing will quantify benefits of weight savings, as well as noise and vibration reduction. The expectation is that vibration and noise will be reduced through the introduction of composite material in the vibration transmission path between the contacting gear teeth and the shaft-and-bearing system.

  20. Braided Composite Technologies for Rotorcraft Structures

    NASA Technical Reports Server (NTRS)

    Jessie, Nathan

    2014-01-01

    A&P Technology has developed a braided material approach for fabricating lightweight, high-strength hybrid gears for aerospace drive systems. The conventional metallic web was replaced with a composite element made from A&P's quasi-isotropic braid. The 0deg, plus or minus 60 deg braid architecture was chosen so that inplane stiffness properties and strength would be nearly equal in all directions. The test results from the Phase I Small Spur Gear program demonstrated satisfactory endurance and strength while providing a 20 percent weight savings. (Greater weight savings is anticipated with structural optimization.) The hybrid gears were subjected to a proof-of-concept test of 1 billion cycles in a gearbox at 10,000 revolutions per minute and 490 in-lb torque with no detectable damage to the gears. After this test the maximum torque capability was also tested, and the static strength capability of the gears was 7x the maximum operating condition. Additional proof-of-concept tests are in progress using a higher oil temperature, and a loss-of-oil test is planned. The success of Phase I led to a Phase II program to develop, fabricate, and optimize full-scale gears, specifically Bull Gears. The design of these Bull Gears will be refined using topology optimization, and the full-scale Bull Gears will be tested in a full-scale gear rig. The testing will quantify benefits of weight savings, as well as noise and vibration reduction. The expectation is that vibration and noise will be reduced through the introduction of composite material in the vibration transmission path between the contacting gear teeth and the shaft-and-bearing system.

  1. Development of Damped Metal Matrix Composites for Advanced Structural Applications

    DTIC Science & Technology

    1990-04-01

    DTIP FiLE COPY Applied Research Laboratory (Dto 00 CD Technical Report NO DEVELOPMENT OF DAMPED METAL MATRIX COMPOSITES FOR ADVANCED STRUCTURAL...DEVELOPMENT OF DAMPED METAL MATRIX COMPOSITES FOR ADVANCED STRUCTURAL APPLICATIONS by Clark A. Updike Ram B. Bhagat Technical Report No. TR 90-004 April 1990... Metal Matrix Composites for Advanced Structural Applications 12 PERSONAL AUTHOR(S) C.A. Updike, R. Bhagat 1 3a TYPE OF REPORT 13b TIME COVERED 14. DATE

  2. Characterization and Detection of Delamination in Smart Composite Structures

    DTIC Science & Technology

    2006-12-31

    H., 1994. New higher-order plate theory in modeling delamination buckling of composite laminates . AIAA Journal 32(8) 1709-1716. Chattopadhyay, A...Goldberg, R.K., 2000. Implementation of Laminate Theory Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites . NASA/TM... theories for composite laminates , judged against experimental evidence. Composites Science and Technology 62 (12-13), 1725-1797. Hsu, Y.S., Reddy, J.N

  3. Metallic layered composite materials produced by explosion welding: Structure, properties, and structure of the transition zone

    NASA Astrophysics Data System (ADS)

    Mal'tseva, L. A.; Tyushlyaeva, D. S.; Mal'tseva, T. V.; Pastukhov, M. V.; Lozhkin, N. N.; Inyakin, D. V.; Marshuk, L. A.

    2014-10-01

    The structure, morphology, and microhardness of the transition zone in multilayer metallic composite joints are studied, and the cohesion strength of the plates to be joined, the mechanical properties of the formed composite materials, and fracture surfaces are analyzed. The materials to be joined are plates (0.1-1 mm thick) made of D16 aluminum alloy, high-strength maraging ZI90-VI (03Kh12N9K4M2YuT) steel, BrB2 beryllium bronze, and OT4-1 titanium alloy. Composite materials made of different materials are shown to be produced by explosion welding. The dependence of the interface shape (smooth or wavelike) on the physicomechanical properties of the materials to be joined is found. The formation of a wavelike interface is shown to result in the formation of intense-mixing regions in transition zones. Possible mechanisms of layer adhesion are discussed.

  4. Study on voids of epoxy matrix composites sandwich structure parts

    NASA Astrophysics Data System (ADS)

    He, Simin; Wen, Youyi; Yu, Wenjun; Liu, Hong; Yue, Cheng; Bao, Jing

    2017-03-01

    Void is the most common tiny defect of composite materials. Porosity is closely related to composite structure property. The voids forming behaviour in the composites sandwich structural parts with the carbon fiber reinforced epoxy resin skins was researched by adjusting the manufacturing process parameters. The composites laminate with different porosities were prepared with the different process parameter. The ultrasonic non-destructive measurement method for the porosity was developed and verified through microscopic examination. The analysis results show that compaction pressure during the manufacturing process had influence on the porosity in the laminate area. Increasing the compaction pressure and compaction time will reduce the porosity of the laminates. The bond-line between honeycomb core and carbon fiber reinforced epoxy resin skins were also analyzed through microscopic examination. The mechanical properties of sandwich structure composites were studied. The optimization process parameters and porosity ultrasonic measurement method for composites sandwich structure have been applied to the production of the composite parts.

  5. Structural Durability of Damaged Metallic Panel Repaired with Composite Patches

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon; Chamis, Christos C.

    1997-01-01

    Structural durability/damage tolerance characteristics of an aluminum tension specimen possessing a short crack and repaired by applying a fiber composite surface patch is investigated via computational simulation. The composite patch is made of graphite/epoxy plies with various layups. An integrated computer code that accounts for all possible failure modes is utilized for the simulation of combined fiber-composite/aluminum structural degradation under loading. Damage initiation, growth, accumulation, and propagation to structural fracture are included in the simulation. Results show the structural degradation stages due to tensile loading and illustrate the use of computational simulation for the investigation of a composite patch repaired cracked metallic panel.

  6. Multi-material Preforming of Structural Composites

    SciTech Connect

    Norris, Robert E.; Eberle, Cliff C.; Pastore, Christopher M.; Sudbury, Thomas Z.; Xiong, Fue; Hartman, David

    2015-05-01

    Fiber-reinforced composites offer significant weight reduction potential, with glass fiber composites already widely adopted. Carbon fiber composites deliver the greatest performance benefits, but their high cost has inhibited widespread adoption. This project demonstrates that hybrid carbon-glass solutions can realize most of the benefits of carbon fiber composites at much lower cost. ORNL and Owens Corning Reinforcements along with program participants at the ORISE collaborated to demonstrate methods for produce hybrid composites along with techniques to predict performance and economic tradeoffs. These predictions were then verified in testing coupons and more complex demonstration articles.

  7. Magnetic behavior of NiCu nanowire arrays: Compositional, geometry and temperature dependence

    SciTech Connect

    Palmero, E. M. Bran, C.; Real, R. P. del; Vázquez, M.; Magén, C.

    2014-07-21

    Arrays of Ni{sub 100−x}Cu{sub x} nanowires ranging in composition 0 ≤ x ≤ 75, diameter from 35 to 80 nm, and length from 150 nm to 28 μm have been fabricated by electrochemical co-deposition of Ni and Cu into self-ordered anodic aluminum oxide membranes. As determined by X-ray diffraction and Transmission Electron Microscopy, the crystalline structure shows fcc cubic symmetry with [111] preferred texture and preferential Ni or Cu lattice depending on the composition. Their magnetic properties such as coercivity and squareness have been determined as a function of composition and geometry in a Vibrating Sample Magnetometer in the temperature range from 10 to 290 K for applied magnetic fields parallel and perpendicular to the nanowires axis. Addition of Cu into the NiCu alloy up to 50% enhances both parallel coercivity and squareness. For the higher Cu content, these properties decrease and the magnetization easy axis becomes oriented perpendicular to the wires. In addition, coercivity and squareness increase by decreasing the diameter of nanowires which is ascribed to the increase of shape anisotropy. The temperature dependent measurements reflect a complex behavior of the magnetic anisotropy as a result of energy contributions with different evolution with temperature.

  8. Composition, structure and chemistry of interstellar dust

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. G. M.; Allamandola, Louis J.

    1986-01-01

    The observational constraints on the composition of the interstellar dust are analyzed. The dust in the diffuse interstellar medium consists of a mixture of stardust (amorphous silicates, amorphous carbon, polycyclic aromatic hydrocarbons, and graphite) and interstellar medium dust (organic refractory material). Stardust seems to dominate in the local diffuse interstellar medium. Inside molecular clouds, however, icy grain mantles are also important. The structural differences between crystalline and amorphous materials, which lead to differences in the optical properties, are discussed. The astrophysical consequences are briefly examined. The physical principles of grain surface chemistry are discussed and applied to the formation of molecular hydrogen and icy grain mantles inside dense molecular clouds. Transformation of these icy grain mantles into the organic refractory dust component observed in the diffuse interstellar medium requires ultraviolet sources inside molecular clouds as well as radical diffusion promoted by transient heating of the mantle. The latter process also returns a considerable fraction of the molecules in the grain mantle to the gas phase.

  9. Advanced Composite Structures At NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Eldred, Lloyd B.

    2015-01-01

    Dr. Eldred's presentation will discuss several NASA efforts to improve and expand the use of composite structures within aerospace vehicles. Topics will include an overview of NASA's Advanced Composites Project (ACP), Space Launch System (SLS) applications, and Langley's ISAAC robotic composites research tool.

  10. Fire Response of Geopolymer Structural Composites.

    DTIC Science & Technology

    1996-01-01

    The fire response of a potassium aluminosilicate matrix ( geopolymer ) carbon fiber composite was measured and the results compared to organic matrix...laminates ignited readily and released appreciable heat and smoke, while carbon-fiber reinforced geopolymer composites did not ignite, burn, or release...any smoke even after extended heat flux exposure. The geopolymer matrix carbon fiber composite retains sixty-three percent of its original 245 MPa flexural strength after a simulated large fire exposure. (MM)

  11. Compression strength of composite primary structural components

    NASA Technical Reports Server (NTRS)

    Johnson, Eric R.

    1994-01-01

    The linear elastic response is determined for an internally pressurized, long circular cylindrical shell stiffened on the inside by a regular arrangement of identical stringers and identical rings. Periodicity of this configuration permits the analysis of a portion of the shell wall centered over a generic stringer-ring joint; i.e., a unit cell model. The stiffeners are modeled as discrete beams, and the stringer is assumed to have a symmetrical cross section and the ring an asymmetrical section. Asymmetery causes out-of-plane bending and torsion of the ring. Displacements are assumed as truncated double Fourier series plus simple terms in the axial coordinate to account for the closed and pressure vessel effect (a non-periodic effect). The interacting line loads between the stiffeners and the inside shell wall are Lagrange multipliers in the formulation, and they are also assumed as truncated Fourier series. Displacement continuity constraints between the stiffeners and shell along the contact lines are satisfied point-wise. Equilibrium is imposed by the principle of virtual work. A composite material crown panel from the fuselage of a large transport aircraft is the numerical example. The distributions of the interacting line loads, and the out-of-plane bending moment and torque in the ring, are strongly dependent on modeling the deformations due to transverse shear and cross-sectional warping of the ring in torsion. This paper contains the results from the semiannual report on research on 'Pressure Pillowing of an Orthogonally Stiffened Cylindrical Shell'. The results of the new work are illustrated in the included appendix.

  12. Composite Bus Structure for the SMEX/WIRE Satellite

    NASA Technical Reports Server (NTRS)

    Rosanova, Giulio G.

    1998-01-01

    In an effort to reduce the weight and optimize the structural design of the Small Explorer (SMEX) Wide-Field Infrared Explorer (WIRE) spacecraft, it has become desirable to change the material and construction from mechanically fastened aluminum structure to a fully bonded fiber-reinforced composite (FRC) structure. GSFC has developed the WIRE spacecraft structural bus design concept, including the instrument and launch vehicle requirements. The WIRE Satellite is the fifth of a series of SMEX satellites to be launched once per year. GSFC has chosen Composite Optics Inc. (COI) as the prime contractor for the development and procurement of the WIRE composite structure. The detailed design of the fully bonded FRC structure is based on COI's Short Notice Accelerated Production SATellite ("SNAPSAT") approach. SNAPSAT is a state of the art design and manufacturing technology for advanced composite materials which utilizes flat-stock detail parts bonded together to produce a final structural assembly. The structural design approach adopted for the WIRE structure provides a very viable alternative to both traditional aluminum construction as well as high tech. molded type composite structures. This approach to composite structure design is much less costly than molded or honeycomb sandwich type composite construction, but may cost slightly more than conventional aluminum construction on the subsystem level. However on the overall program level the weight saving achieved is very cost effective, since the primary objective is to allocate more mass for science payloads.

  13. Composites structures for bone tissue reconstruction

    NASA Astrophysics Data System (ADS)

    Neto, W.; Santos, João.; Avérous, L.; Schlatter, G.; Bretas, Rosario.

    2015-05-01

    The search for new biomaterials in the bone reconstitution field is growing continuously as humane life expectation and bone fractures increase. For this purpose, composite materials with biodegradable polymers and hydroxyapatite (HA) have been used. A composite material formed by a film, nanofibers and HA has been made. Both, the films and the non-woven mats of nanofibers were formed by nanocomposites made of butylene adipate-co-terephthalate (PBAT) and HA. The techniques used to produce the films and nanofibers were spin coating and electrospinning, respectively. The composite production and morphology were evaluated. The composite showed an adequate morphology and fibers size to be used as scaffold for cell growth.

  14. Composites structures for bone tissue reconstruction

    SciTech Connect

    Neto, W.; Santos, João; Avérous, L.; Schlatter, G.; Bretas, Rosario

    2015-05-22

    The search for new biomaterials in the bone reconstitution field is growing continuously as humane life expectation and bone fractures increase. For this purpose, composite materials with biodegradable polymers and hydroxyapatite (HA) have been used. A composite material formed by a film, nanofibers and HA has been made. Both, the films and the non-woven mats of nanofibers were formed by nanocomposites made of butylene adipate-co-terephthalate (PBAT) and HA. The techniques used to produce the films and nanofibers were spin coating and electrospinning, respectively. The composite production and morphology were evaluated. The composite showed an adequate morphology and fibers size to be used as scaffold for cell growth.

  15. Boron carbide: Consistency of components, lattice parameters, fine structure and chemical composition makes the complex structure reasonable

    NASA Astrophysics Data System (ADS)

    Werheit, Helmut

    2016-10-01

    The complex, highly distorted structure of boron carbide is composed of B12 and B11C icosahedra and CBC, CBB and B□B linear elements, whose concentration depends on the chemical composition each. These concentrations are shown to be consistent with lattice parameters, fine structure data and chemical composition. The respective impacts on lattice parameters are estimated and discussed. Considering the contributions of the different structural components to the energy of the overall structure makes the structure and its variation within the homogeneity range reasonable; in particular that of B4.3C representing the carbon-rich limit of the homogeneity range. Replacing in B4.3C virtually the B□B components by CBC yields the hypothetical moderately distorted B4.0C (structure formula (B11C)CBC). The reduction of lattice parameters related is compatible with recently reported uncommonly prepared single crystals, whose compositions deviate from B4.3C.

  16. Composition dependent valence band order in c-oriented wurtzite AlGaN layers

    SciTech Connect

    Neuschl, B. Helbing, J.; Knab, M.; Lauer, H.; Madel, M.; Thonke, K.; Feneberg, M.

    2014-09-21

    The valence band order of polar wurtzite aluminum gallium nitride (AlGaN) layers is analyzed for a dense series of samples, grown heteroepitaxially on sapphire substrates, covering the complete composition range. The excitonic transition energies, found by temperature dependent photoluminescence (PL) spectroscopy, were corrected to the unstrained state using input from X-ray diffraction. k∙p theory yields a critical relative aluminum concentration x{sub c}=(0.09±0.05) for the crossing of the uppermost two valence bands for strain free material, shifting to higher values for compressively strained samples, as supported by polarization dependent PL. The analysis of the strain dependent valence band crossing reconciles the findings of other research groups, where sample strain was neglected. We found a bowing for the energy band gap to the valence band with Γ₉ symmetry of b{sub Γ₉}=0.85eV, and propose a possible bowing for the crystal field energy of b{sub cf}=-0.12eV. A comparison of the light extraction efficiency perpendicular and parallel to the c axis of Al{sub x}Ga{sub 1-x}N/Al{sub y}Ga{sub 1-y}N quantum well structures is discussed for different compositions.

  17. Probabilistic evaluation of fuselage-type composite structures

    NASA Technical Reports Server (NTRS)

    Shiao, Michael C.; Chamis, Christos C.

    1992-01-01

    A methodology is developed to computationally simulate the uncertain behavior of composite structures. The uncertain behavior includes buckling loads, natural frequencies, displacements, stress/strain etc., which are the consequences of the random variation (scatter) of the primitive (independent random) variables in the constituent, ply, laminate and structural levels. This methodology is implemented in the IPACS (Integrated Probabilistic Assessment of Composite Structures) computer code. A fuselage-type composite structure is analyzed to demonstrate the code's capability. The probability distribution functions of the buckling loads, natural frequency, displacement, strain and stress are computed. The sensitivity of each primitive (independent random) variable to a given structural response is also identified from the analyses.

  18. Measuring Moisture Levels in Graphite Epoxy Composite Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Nurge, Mark; Youngquist, Robert; Starr, Stanley

    2011-01-01

    Graphite epoxy composite (GEC) materials are used in the construction of rocket fairings, nose cones, interstage adapters, and heat shields due to their high strength and light weight. However, they absorb moisture depending on the environmental conditions they are exposed to prior to launch. Too much moisture absorption can become a problem when temperature and pressure changes experienced during launch cause the water to vaporize. The rapid state change of the water can result in structural failure of the material. In addition, heat and moisture combine to weaken GEC structures. Diffusion models that predict the total accumulated moisture content based on the environmental conditions are one accepted method of determining if the material strength has been reduced to an unacceptable level. However, there currently doesn t exist any field measurement technique to estimate the actual moisture content of a composite structure. A multi-layer diffusion model was constructed with Mathematica to predict moisture absorption and desorption from the GEC sandwich structure. This model is used in conjunction with relative humidity/temperature sensors both on the inside and outside of the material to determine the moisture levels in the structure. Because the core materials have much higher diffusivity than the face sheets, a single relative humidity measurement will accurately reflect the moisture levels in the core. When combined with an external relative humidity measurement, the model can be used to determine the moisture levels in the face sheets. Since diffusion is temperaturedependent, the temperature measurements are used to determine the diffusivity of the face sheets for the model computations.

  19. Simplified design procedures for fiber composite structural components/joints

    NASA Technical Reports Server (NTRS)

    Murthy, P. L. N.; Chamis, Christos C.

    1990-01-01

    Simplified step-by-step design procedures are summarized, which are suitable for the preliminary design of composite structural components such as panels (laminates) and composite built-up structures (box beams). Similar procedures are also summarized for the preliminary design of composite bolted and adhesively bonded joints. The summary is presented in terms of sample design cases complemented with typical results. Guidelines are provided which can be used in the design selection process of composite structural components/joints. Also, procedures to account for cyclic loads, hygrothermal effects and lamination residual stresses are included.

  20. Composite isogrid structures for parabolic surfaces

    NASA Technical Reports Server (NTRS)

    Silverman, Edward M. (Inventor); Boyd, Jr., William E. (Inventor); Rhodes, Marvin D. (Inventor); Dyer, Jack E. (Inventor)

    2000-01-01

    The invention relates to high stiffness parabolic structures utilizing integral reinforced grids. The parabolic structures implement the use of isogrid structures which incorporate unique and efficient orthotropic patterns for efficient stiffness and structural stability.

  1. Composition and temperature-dependent phase transition in miscible Mo1−xWxTe2 single crystals

    PubMed Central

    Lv, Yang-Yang; Cao, Lin; Li, Xiao; Zhang, Bin-Bin; Wang, Kang; Bin Pang, B P; Ma, Ligang; Lin, Dajun; Yao, Shu-Hua; Zhou, Jian; Chen, Y. B.; Dong, Song-Tao; Liu, Wenchao; Lu, Ming-Hui; Chen, Yulin; Chen, Yan-Feng

    2017-01-01

    Transition metal dichalcogenides (TMDs) WTe2 and MoTe2 with orthorhombic Td phase, being potential candidates as type-II Weyl semimetals, are attracted much attention recently. Here we synthesized a series of miscible Mo1−xWxTe2 single crystals by bromine vapor transport method. Composition-dependent X-ray diffraction and Raman spectroscopy, as well as composition and temperature-dependent resistivity prove that the tunable crystal structure (from hexagonal (2H), monoclinic (β) to orthorhombic (Td) phase) can be realized by increasing W content in Mo1−xWxTe2. Simultaneously the electrical property gradually evolves from semiconductor to semimetal behavior. Temperature-dependent Raman spectroscopy proves that temperature also can induce the structural phase transition from β to Td phase in Mo1−xWxTe2 crystals. Based on aforementioned characterizations, we map out the temperature and composition dependent phase diagram of Mo1−xWxTe2 system. In addition, a series of electrical parameters, such as carrier type, carrier concentration and mobility, have also been presented. This work offers a scheme to accurately control structural phase in Mo1−xWxTe2 system, which can be used to explore type-II Weyl semimetal, as well as temperature/composition controlled topological phase transition therein. PMID:28294191

  2. Composition and temperature-dependent phase transition in miscible Mo1‑xWxTe2 single crystals

    NASA Astrophysics Data System (ADS)

    Lv, Yang-Yang; Cao, Lin; Li, Xiao; Zhang, Bin-Bin; Wang, Kang; Bin Pang; Ma, Ligang; Lin, Dajun; Yao, Shu-Hua; Zhou, Jian; Chen, Y. B.; Dong, Song-Tao; Liu, Wenchao; Lu, Ming-Hui; Chen, Yulin; Chen, Yan-Feng

    2017-03-01

    Transition metal dichalcogenides (TMDs) WTe2 and MoTe2 with orthorhombic Td phase, being potential candidates as type-II Weyl semimetals, are attracted much attention recently. Here we synthesized a series of miscible Mo1‑xWxTe2 single crystals by bromine vapor transport method. Composition-dependent X-ray diffraction and Raman spectroscopy, as well as composition and temperature-dependent resistivity prove that the tunable crystal structure (from hexagonal (2H), monoclinic (β) to orthorhombic (Td) phase) can be realized by increasing W content in Mo1‑xWxTe2. Simultaneously the electrical property gradually evolves from semiconductor to semimetal behavior. Temperature-dependent Raman spectroscopy proves that temperature also can induce the structural phase transition from β to Td phase in Mo1‑xWxTe2 crystals. Based on aforementioned characterizations, we map out the temperature and composition dependent phase diagram of Mo1‑xWxTe2 system. In addition, a series of electrical parameters, such as carrier type, carrier concentration and mobility, have also been presented. This work offers a scheme to accurately control structural phase in Mo1‑xWxTe2 system, which can be used to explore type-II Weyl semimetal, as well as temperature/composition controlled topological phase transition therein.

  3. Design considerations for composite fuselage structure of commercial transport aircraft

    NASA Technical Reports Server (NTRS)

    Davis, G. W.; Sakata, I. F.

    1981-01-01

    The structural, manufacturing, and service and environmental considerations that could impact the design of composite fuselage structure for commercial transport aircraft application were explored. The severity of these considerations was assessed and the principal design drivers delineated. Technical issues and potential problem areas which must be resolved before sufficient confidence is established to commit to composite materials were defined. The key issues considered are: definition of composite fuselage design specifications, damage tolerance, and crashworthiness.

  4. Structural characterization of high temperature composites

    NASA Technical Reports Server (NTRS)

    Mandell, J. F.; Grande, D. H.

    1991-01-01

    Glass, ceramic, and carbon matrix composite materials have emerged in recent years with potential properties and temperature resistance which make them attractive for high temperature applications such as gas turbine engines. At the outset of this study, only flexural tests were available to evaluate brittle matrix composites at temperatures in the 600 to 1000 C range. The results are described of an ongoing effort to develop appropriate tensile, compression, and shear test methods for high temperature use. A tensile test for unidirectional composites was developed and used to evaluate the properties and behavior of ceramic fiber reinforced glass and glass-ceramic matrix composites in air at temperatures up to 1000 C. The results indicate generally efficient fiber reinforcement and tolerance to matrix cracking similar to polymer matrix composites. Limiting properties in these materials may be an inherently very low transverse strain to failure, and high temperature embrittlement due to fiber/matrix interface oxidation.

  5. Micromechanical models for textile structural composites

    NASA Technical Reports Server (NTRS)

    Marrey, Ramesh V.; Sankar, Bhavani V.

    1995-01-01

    The objective is to develop micromechanical models for predicting the stiffness and strength properties of textile composite materials. Two models are presented to predict the homogeneous elastic constants and coefficients of thermal expansion of a textile composite. The first model is based on rigorous finite element analysis of the textile composite unit-cell. Periodic boundary conditions are enforced between opposite faces of the unit-cell to simulate deformations accurately. The second model implements the selective averaging method (SAM), which is based on a judicious combination of stiffness and compliance averaging. For thin textile composites, both models can predict the plate stiffness coefficients and plate thermal coefficients. The finite element procedure is extended to compute the thermal residual microstresses, and to estimate the initial failure envelope for textile composites.

  6. Analysis of SMA Hybrid Composite Structures using Commercial Codes

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Patel, Hemant D.

    2004-01-01

    A thermomechanical model for shape memory alloy (SMA) actuators and SMA hybrid composite (SMAHC) structures has been recently implemented in the commercial finite element codes MSC.Nastran and ABAQUS. The model may be easily implemented in any code that has the capability for analysis of laminated composite structures with temperature dependent material properties. The model is also relatively easy to use and requires input of only fundamental engineering properties. A brief description of the model is presented, followed by discussion of implementation and usage in the commercial codes. Results are presented from static and dynamic analysis of SMAHC beams of two types; a beam clamped at each end and a cantilevered beam. Nonlinear static (post-buckling) and random response analyses are demonstrated for the first specimen. Static deflection (shape) control is demonstrated for the cantilevered beam. Approaches for modeling SMAHC material systems with embedded SMA in ribbon and small round wire product forms are demonstrated and compared. The results from the commercial codes are compared to those from a research code as validation of the commercial implementations; excellent correlation is achieved in all cases.

  7. Dependence of methane sorption kinetics on coal structure

    SciTech Connect

    B. Kovaleva; E.A. Solov'eva

    2006-01-15

    The data of experimental laboratory studies into the methane sorption kinetics in samples of mineral coals of different metamorphism grade and petrographic composition are presented. Their relation to the character of gas emission from gas-saturated coal seams is considered. The dependence of the gas emission type on the size of undisturbed fragment of coal and methane diffusion coefficient is revealed.

  8. Progressive fracture of polymer matrix composite structures: A new approach

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Murthy, P. L. N.; Minnetyan, L.

    1992-01-01

    A new approach independent of stress intensity factors and fracture toughness parameters has been developed and is described for the computational simulation of progressive fracture of polymer matrix composite structures. The damage stages are quantified based on physics via composite mechanics while the degradation of the structural behavior is quantified via the finite element method. The approach account for all types of composite behavior, structures, load conditions, and fracture processes starting from damage initiation, to unstable propagation and to global structural collapse. Results of structural fracture in composite beams, panels, plates, and shells are presented to demonstrate the effectiveness and versatility of this new approach. Parameters and guidelines are identified which can be used as criteria for structural fracture, inspection intervals, and retirement for cause. Generalization to structures made of monolithic metallic materials are outlined and lessons learned in undertaking the development of new approaches, in general, are summarized.

  9. Size effect in composite materials and structures: Basic concepts and design considerations

    NASA Technical Reports Server (NTRS)

    Zweben, Carl

    1994-01-01

    Composite materials display strength characteristics that are similar to those of brittle ceramics, whose strengths are known to decrease with increasing volume for a uniform state of stress (size effect) and also are dependent on stress distribution. These similarities raise the question of whether there is also a size effect in composite materials and structures. There is significant, but inconclusive experimental evidence for the existence of a size effect in composites. Macroscopic and micromechanical statistical models have been developed which predict a size effect and are in general agreement with experimental data. The existence of a significant size effect in composites would be of great importance. For example, it would mean that use of standard test coupons to establish design allowables for large structures could be very nonconservative. Further, it would be necessary to analyze the strength of large composite structures using statistical methods, as is done for ceramics.

  10. Acoustic wave velocities in two-dimensional composite structures based on acousto-optical crystals

    NASA Astrophysics Data System (ADS)

    Mal'neva, P. V.; Trushin, A. S.

    2015-04-01

    Sound velocities in two-dimensional composite structures based on isotropic and anisotropic acousto-optical crystals have been determined by numerical simulations. The isotropic materials are represented by fused quartz (SiO2) and flint glass, while anisotropic materials include tetragonal crystals of paratellurite (TeO2) and rutile (TiO2) and a trigonal crystal of tellurium (Te). It is established that the acoustic anisotropy of periodic composite structures strongly depends on both the chemical composition and geometric parameters of components.

  11. Fiber Reinforced Composites for Insulation and Structures

    NASA Technical Reports Server (NTRS)

    Broughton, Roy M., Jr.

    2005-01-01

    The work involves two areas: Composites, optimum fiber placement with initial construction of a pressure vessel, and the general subject of insulation, a continual concern in harsh thermal environments. Insulation

  12. Development of Biobased Composites of Structural Quality

    NASA Astrophysics Data System (ADS)

    Taylor, Christopher Alan

    Highly biobased composites with properties and costs rivaling those consisting of synthetic constituents are a goal of much current research. The obvious material choices, vegetable oil based resins and natural fibers, present the challenges of poor resin properties and weak fiber/matrix bonding, respectively. Conventional methods of overcoming poor resin quality involve the incorporation of additives, which dilutes the resulting composite's bio-content and increases cost. To overcome these limitations while maintaining high bio-content and low cost, epoxidized sucrose soyate is combined with surface-treated flax fiber to produce biocomposites. These composites are fabricated using methods emphasizing scalability and efficiency, for cost effectiveness of the final product. This approach resulted in the successful production of biocomposites having properties that meet or exceed those of conventional pultruded members. These properties, such as tensile and flexural strengths of 223 and 253 MPa, respectively, were achieved by composites having around 85% bio-content.

  13. Structural Composites Corrosive Management by Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Minnetyan, Levon

    2006-01-01

    A simulation of corrosive management on polymer composites durability is presented. The corrosive environment is assumed to manage the polymer composite degradation on a ply-by-ply basis. The degradation is correlated with a measured Ph factor and is represented by voids, temperature, and moisture which vary parabolically for voids and linearly for temperature and moisture through the laminate thickness. The simulation is performed by a computational composite mechanics computer code which includes micro, macro, combined stress failure, and laminate theories. This accounts for starting the simulation from constitutive material properties and up to the laminate scale which exposes the laminate to the corrosive environment. Results obtained for one laminate indicate that the ply-by-ply managed degradation degrades the laminate to the last one or the last several plies. Results also demonstrate that the simulation is applicable to other polymer composite systems as well.

  14. Production of Be-10 in stony meteorites - Composition dependence

    NASA Technical Reports Server (NTRS)

    Moniot, R. K.; Tuniz, C.; Kruse, T. H.; Savin, W.; Pal, D. K.

    1988-01-01

    The relationship between the production rate of Be-10 in stony meteorites and its element composition was investigated by measuring the contents of Be-10 in 21 samples from 17 meteorites with known major-element composition, and comparing the experimental Be-10 values with those obtained by the regression analysis. The Be-10 production was modeled by the equation of Stauffer (1962). The measured Be-10 contents were found to range from 16 dpm/kg in the oxygen- and magnesium-poor eucrites and the Indarch meteorite to 28 dpm/kg in the oxygen- and magnesium-rich aubrites and the mineral separates from Bruderheim. Using the regression analyses and taking in account various corrections, an equation was obtained which reproduces the measured Be-10 content with an accuracy of about 10 percent.

  15. Composite Payload Fairing Structural Architecture Assessment and Selection

    NASA Technical Reports Server (NTRS)

    Krivanek, Thomas M.; Yount, Bryan C.

    2012-01-01

    This paper provides a summary of the structural architecture assessments conducted and a recommendation for an affordable high performance composite structural concept to use on the next generation heavy-lift launch vehicle, the Space Launch System (SLS). The Structural Concepts Element of the Advanced Composites Technology (ACT) project and its follow on the Lightweight Spacecraft Structures and Materials (LSSM) project was tasked with evaluating a number of composite construction technologies for specific Ares V components: the Payload Shroud, the Interstage, and the Core Stage Intertank. Team studies strived to address the structural challenges, risks and needs for each of these vehicle components. Leveraging off of this work, the subsequent Composites for Exploration (CoEx) effort is focused on providing a composite structural concept to support the Payload Fairing for SLS. This paper documents the evaluation and down selection of composite construction technologies and evolution to the SLS Payload Fairing. Development of the evaluation criteria (also referred to as Figures of Merit or FOMs), their relative importance, and association to vehicle requirements are presented. A summary of the evaluation results, and a recommendation of the composite concept to baseline in the Composites for Exploration (CoEx) project is presented. The recommendation for the SLS Fairing is a Honeycomb Sandwich architecture based primarily on affordability and performance with two promising alternatives, Hat stiffened and Fiber Reinforced Foam (FRF) identified for eventual program block upgrade.

  16. Recent advancement in optical fiber sensing for aerospace composite structures

    NASA Astrophysics Data System (ADS)

    Minakuchi, Shu; Takeda, Nobuo

    2013-12-01

    Optical fiber sensors have attracted considerable attention in health monitoring of aerospace composite structures. This paper briefly reviews our recent advancement mainly in Brillouin-based distributed sensing. Damage detection, life cycle monitoring and shape reconstruction systems applicable to large-scale composite structures are presented, and new technical concepts, "smart crack arrester" and "hierarchical sensing system", are described as well, highlighting the great potential of optical fiber sensors for the structural health monitoring (SHM) field.

  17. Effects of Fluid-Structure Interaction on Dynamic Response of Composite Structures: Experimental and Numerical Studies

    DTIC Science & Technology

    2013-08-01

    composite structures in water and air to enhance the understanding of the effects of fluid-structure interaction on marine composite structural...naval structures are in continuous contact with a water medium. As a result, proper understanding of fluid-structure interaction is important for a...Fluid-Structure Interaction (FSI) is more critical for the former structures. The objective of this study was to investigate the effect of water on

  18. Compositional dependence of in vitro response to commercial silicate glasses

    NASA Astrophysics Data System (ADS)

    Jedlicka, Amy B.

    Materials are often incorporated into the human body, interacting with surrounding fluids, cells and tissues. The reactions that occur between a material and this surrounding biological system are not fundamentally understood. Basic knowledge of material biocompatibility and the controlling processes is lacking. This thesis examines material biocompatibility of a series of silicate-based glasses on a primary level determining cell response to material composition and durability. The silicate glass system studied included two BioglassRTM compositions with known biologically favorable response, two fiberglass compositions, with demonstrated 'not-unfavorable' in vitro response, a ternary soda-lime-silicate glass, a binary alkali silicate glass, and pure silica. Chemical durability was analyzed in three different fluids through solution analysis and material characterization. In vitro response to the substrates was observed. Cell behavior was then directly correlated to the material behavior in cell culture medium under the same conditions as the in vitro test, yet in the absence of cells. The effect of several physical and chemical surface treatments on substrates with predetermined biocompatible behavior was subsequently determined. The chemically durable glasses with no added B2O3 elicited similar cell response as the control polystyrene substrate. The addition of B2O3 resulted in polygonal cell shape and restricted cell proliferation. The non-durable glasses presented a dynamic surface to the cells, which did not adversely affect in vitro response. Extreme dissolution of the binary alkali silicate glass in conjunction with increased pH resulted in unfavorable cell response. Reaction of the Bioglass RTM compositions, producing a biologically favorable calcium-phosphate surface film, caused enhanced cell attachment and spreading. Surface energy increase due to sterilization procedures did not alter cellular response. Surface treatment procedures influencing substrate

  19. Investigation on Temperature-Dependent Electrical Conductivity of Carbon Nanotube/Epoxy Composites for Sustainable Energy Applications.

    PubMed

    Njuguna, Michael K; Galpaya, Dilini; Yan, Cheng; Colwell, John M; Will, Geoffrey; Hu, Ning; Yarlagadda, Prasad; Bell, John M

    2015-09-01

    Composites with carbon nanotubes are becoming increasingly used in energy storage and electronic devices, due to incorporated excellent properties from carbon nanotubes and polymers. Although their properties make them more attractive than conventional smart materials, their electrical properties have been found to be temperature-dependent which is important to consider for the design of devices. To study the effects of temperature in electrically conductive multi-wall carbon nanotube/epoxy composites, thin films were prepared and the effect of temperature on the resistivity, thermal properties and Raman spectral characteristics of the composite films was evaluated. Resistivity-temperature profiles showed three distinct regions in as-cured samples and only two regions in samples whose thermal histories had been erased. In the vicinity of the glass transition temperature, the as-cured composites exhibited pronounced resistivity and enthalpic relaxation peaks, which both disappeared after erasing the composites' thermal histories by temperature cycling. Combined DSC, Raman spectroscopy, and resistivity-temperature analyses indicated that this phenomenon can be attributed to the physical aging of the epoxy matrix and that, in the region of the observed thermal history-dependent resistivity peaks, structural rearrangement of the conductive carbon nanotube network occurs through a volume expansion/relaxation process. These results have led to an overall greater understanding of the temperature-dependent behaviour of conductive carbon nanotube/epoxy composites, including the positive temperature coefficient effect.

  20. Structural Ceramic Composites for Nuclear Applications

    SciTech Connect

    William Windes; P.A. Lessing; Y. Katoh; L. L. Snead; E. Lara-Curzio; J. Klett; C. Henager, Jr.; R. J. Shinavski

    2005-08-01

    A research program has been established to investigate fiber reinforced ceramic composites to be used as control rod components within a Very High Temperature Reactor. Two candidate systems have been identified, carbon fiber reinforced carbon (Cf/C) and silicon carbide fiber reinforced silicon carbide (SiCf/SiC) composites. Initial irradiation stability studies to determine the maximum dose for each composite type have been initiated within the High Flux Isotope Reactor at Oak Ridge National Laboratory. Test samples exposed to 10 dpa irradiation dose have been completed with future samples to dose levels of 20 and 30 dpa scheduled for completion in following years. Mechanical and environmental testing is being conducted concurrently at the Idaho National Laboratory and at Pacific Northwest National Laboratory. High temperature test equipment, testing methodologies, and test samples for high temperature (up to 1600º C) tensile strength and long duration creep studies have been established. Specific attention was paid to the architectural fiber preform design as well as the materials used in construction of the composites. Actual testing of both tubular and flat, "dog-bone" shaped tensile composite specimens will begin next year. Since there is no precedence for using ceramic composites within a nuclear reactor, ASTM standard test procedures will be established from these mechanical and environmental tests. Close collaborations between the U.S. national laboratories and international collaborators (i.e. France and Japan) are being forged to establish both national and international test standards to be used to qualify ceramic composites for nuclear reactor applications.

  1. Modeling the Dependency Structure of Integrated Intensity Processes

    PubMed Central

    Ma, Yong-Ki

    2015-01-01

    This paper studies an important issue of dependence structure. To model this structure, the intensities within the Cox processes are driven by dependent shot noise processes, where jumps occur simultaneously and their sizes are correlated. The joint survival probability of the integrated intensities is explicitly obtained from the copula with exponential marginal distributions. Subsequently, this result can provide a very useful guide for credit risk management. PMID:26270638

  2. Continuation of tailored composite structures of ordered staple thermoplastic material

    NASA Technical Reports Server (NTRS)

    Santare, Michael H.; Pipes, R. Byron

    1992-01-01

    The search for the cost effective composite structure has motivated the investigation of several approaches to develop composite structure from innovative material forms. Among the promising approaches is the conversion of a planar sheet to components of complex curvature through sheet forming or stretch forming. In both cases, the potential for material stretch in the fiber direction appears to offer a clear advantage in formability over continuous fiber systems. A framework was established which allows the simulation of the anisotropic mechanisms of deformation of long discontinuous fiber laminates wherein the matrix phase is a viscous fluid. Predictions for the effective viscosities of a hyper-anisotropic medium consisting of collimated, discontinuous fibers suspended in viscous matrix were extended to capture the characteristics of typical polymers including non-Newtonian behavior and temperature dependence. In addition, the influence of fiber misorientation was also modeled by compliance averaging to determine ensemble properties for a given orientation distribution. A design tool is presented for predicting the effect of material heterogeneity on the performance of curved composite beams such as those used in aircraft fuselage structures. Material heterogeneity can be induced during manufacturing processes such as sheet forming and stretch forming of thermoplastic composites. This heterogeneity can be introduced in the form of fiber realignment and spreading during the manufacturing process causing radial and tangential gradients in material properties. Two analysis procedures are used to solve the beam problems. The first method uses separate two-dimensional elasticity solutions for the stresses in the flange and web sections of the beam. The separate solutions are coupled by requiring that forces and displacements match section boundaries. The second method uses an approximate Rayleigh-Ritz technique to find the solutions for more complex beams. Analyses

  3. Integrated mechanics for the passive damping of polymer-matrix composites and composite structures

    NASA Technical Reports Server (NTRS)

    Saravanos, D. A.; Chamis, Christos C.

    1991-01-01

    Some recent developments on integrated damping mechanics for unidirectional composites, laminates, and composite structures are reviewed. Simplified damping micromechanics relate the damping of on-axis and off-axis composites to constituent properties, fiber volume ratio, fiber orientation, temperature, and moisture. Laminate and structural damping mechanics for thin composites are summarized. Discrete layer damping mechanics for thick laminates, including the effects of interlaminar shear damping, are developed and semianalytical predictions of modal damping in thick simply supported specialty composite plates are presented. Applications show the advantages of the unified mechanics, and illustrate the effect of fiber volume ratio, fiber orientation, structural geometry, and temperature on the damping. Additional damping properties for composite plates of various laminations, aspect ratios, fiber content, and temperature illustrate the merits and ranges of applicability of each theory (thin or thick laminates).

  4. TEMPERATURE DEPENDENCE OF LINE STRUCTURE OF CADMIUM SULFIDE EDGE EMISSION

    DTIC Science & Technology

    The temperature dependence of the line structure in Cds edge emission stimulated by UV light was investigated from 4.2 K to 367 K. The spectral... dependence of the primary line groups is a linear function of temperature above 220 K with coefficients of change of 1.27 and 1.8 Angstroms degree K for the...lines observed. Below 220 K the dependence departs from linearity and approaches its limiting value more rapidly with decreasing temperature

  5. The dependence of lipid asymmetry upon phosphatidylcholine acyl chain structure[S

    PubMed Central

    Son, Mijin; London, Erwin

    2013-01-01

    Lipid asymmetry, the difference in inner and outer leaflet lipid composition, is an important feature of biomembranes. By utilizing our recently developed MβCD-catalyzed exchange method, the effect of lipid acyl chain structure upon the ability to form asymmetric membranes was investigated. Using this approach, SM was efficiently introduced into the outer leaflet of vesicles containing various phosphatidylcholines (PC), but whether the resulting vesicles were asymmetric (SM outside/PC inside) depended upon PC acyl chain structure. Vesicles exhibited asymmetry using PC with two monounsaturated chains of >14 carbons; PC with one saturated and one unsaturated chain; and PC with phytanoyl chains. Vesicles were most weakly asymmetric using PC with two 14 carbon monounsaturated chains or with two polyunsaturated chains. To define the origin of this behavior, transverse diffusion (flip-flop) of lipids in vesicles containing various PCs was compared. A correlation between asymmetry and transverse diffusion was observed, with slower transverse diffusion in vesicles containing PCs that supported lipid asymmetry. Thus, asymmetric vesicles can be prepared using a wide range of acyl chain structures, but fast transverse diffusion destroys lipid asymmetry. These properties may constrain acyl chain structure in asymmetric natural membranes to avoid short or overly polyunsaturated acyl chains. PMID:23093551

  6. Multifunctional Particulate Composites for Structural Applications (PREPRINT)

    DTIC Science & Technology

    2008-05-01

    strain rates were measured, it would most likely be found, as is the case with epoxy, that there is a bilinear dependance of yield stress on strain...variations in experimental measurements. Additional testing at several strain rates is underway to further elucidate the strain rate dependance of yield...MNML-8 6e-4 /s 2500 /s Tr ue S tre ss (M Pa ) Figure 4: Strain rate dependance of yield stress for MNML-2, 3, 5, and 8. Table 2: Mulliken

  7. Iterative solutions for one-dimensional diffusion with time varying surface composition and composition-dependent diffusion coefficient

    NASA Technical Reports Server (NTRS)

    Chow, M.; Houska, C. R.

    1980-01-01

    Solutions are given for one-dimensional diffusion problems with a time varying surface composition and also a composition dependent diffusion coefficient. The most general solution does not require special mathematical functions to fit the variation in surface composition or D(C). In another solution, a series expansion may be used to fit the time dependent surface concentration. These solutions make use of iterative calculations that converge rapidly and are highly stable. Computer times are much shorter than that required for finite difference calculations and can efficiently make use of interactive graphics terminals. Existing gas carburization data were used to provide an illustration of an iterative approach with a time varying carbon composition at the free surface.

  8. Composition dependent thermal annealing behaviour of ion tracks in apatite

    NASA Astrophysics Data System (ADS)

    Nadzri, A.; Schauries, D.; Mota-Santiago, P.; Muradoglu, S.; Trautmann, C.; Gleadow, A. J. W.; Hawley, A.; Kluth, P.

    2016-07-01

    Natural apatite samples with different F/Cl content from a variety of geological locations (Durango, Mexico; Mud Tank, Australia; and Snarum, Norway) were irradiated with swift heavy ions to simulate fission tracks. The annealing kinetics of the resulting ion tracks was investigated using synchrotron-based small-angle X-ray scattering (SAXS) combined with ex situ annealing. The activation energies for track recrystallization were extracted and consistent with previous studies using track-etching, tracks in the chlorine-rich Snarum apatite are more resistant to annealing than in the other compositions.

  9. Impact damage resistance of composite fuselage structure, part 2

    NASA Technical Reports Server (NTRS)

    Dost, Ernest F.; Finn, Scott R.; Murphy, Daniel P.; Huisken, Amy B.

    1993-01-01

    The strength of laminated composite materials may be significantly reduced by foreign object impact induced damage. An understanding of the damage state is required in order to predict the behavior of structure under operational loads or to optimize the structural configuration. Types of damage typically induced in laminated materials during an impact event include transverse matrix cracking, delamination, and/or fiber breakage. The details of the damage state and its influence on structural behavior depend on the location of the impact. Damage in the skin may act as a soft inclusion or affect panel stability, while damage occurring over a stiffener may include debonding of the stiffener flange from the skin. An experiment to characterize impact damage resistance of fuselage structure as a function of structural configuration and impact threat was performed. A wide range of variables associated with aircraft fuselage structure such as material type and stiffener geometry (termed, intrinsic variables) and variables related to the operating environment such as impactor mass and diameter (termed, extrinsic variables) were studied using a statistically based design-of-experiments technique. The experimental design resulted in thirty-two different 3-stiffener panels. These configured panels were impacted in various locations with a number of impactor configurations, weights, and energies. The results obtained from an examination of impacts in the skin midbay and hail simulation impacts are documented. The current discussion is a continuation of that work with a focus on nondiscrete characterization of the midbay hail simulation impacts and discrete characterization of impact damage for impacts over the stiffener.

  10. Flight service environmental effects on composite materials and structures

    NASA Technical Reports Server (NTRS)

    Dexter, H. Benson; Baker, Donald J.

    1992-01-01

    NASA Langley and the U.S. Army have jointly sponsored programs to assess the effects of realistic flight environments and ground-based exposure on advanced composite materials and structures. Composite secondary structural components were initially installed on commercial transport aircraft in 1973; secondary and primary structural components were installed on commercial helicopters in 1979; and primary structural components were installed on commercial aircraft in the mid-to-late 1980's. Service performance, maintenance characteristics, and residual strength of numerous components are reported. In addition to data on flight components, 10 year ground exposure test results on material coupons are reported. Comparison between ground and flight environmental effects for several composite material systems are also presented. Test results indicate excellent in-service performance with the composite components during the 15 year period. Good correlation between ground-based material performance and operational structural performance has been achieved.

  11. Design and Processing of Structural Composite Batteries

    DTIC Science & Technology

    2007-09-01

    The woven fabric, e is 72wt% LiFePO4 , 8wt% acetylene lack, and 20wt% poly(ethylene oxide) 200k as a binder. Acetylene black ensures electrical will...2.1.3 Cathode The composite cathode material utilizes LiFePO4 chemistry. The composition of the cathode material film deposited onto the metal substrat... LiFePO4 chemistry (over a 2.8-4.0V range (8)) including stainless steel and titanium. Stainless steel was evaluated in this udy due to its high

  12. A Review of Crashworthiness of Composite Aircraft Structures

    DTIC Science & Technology

    1990-02-01

    CRASHWORTHINESS OF COMPOSITE AIRCRAFT STRUCTURES ETUDE SUR LA RESISTANCE A L’ECRASEMENT DES STRUCTURES D’AERONEF EN MATERIAUX COMPOSITES by/par C. Poon...menses en Am~rique du Nord sur la resistance A l16crasement des structures d’a~ronef en materiaux composites a 06 effectude dans le but d’identifier les...dimension des a~ro-efs sur les exigences de conception relatives A la resistance A l-cras( , e ,_: l’implantation du code KRASH au Canada pour uniformiser

  13. Composition and growth procedure-dependent properties of electrodeposited CuInSe 2 thin films

    NASA Astrophysics Data System (ADS)

    Babu, S. Moorthy; Ennaoui, A.; Lux-Steiner, M. Ch.

    2005-02-01

    CuInSe 2 thin films were deposited on molybdenum-coated glass substrates by electrodeposition. Deposition was carried out with a variety of electrochemical bath compositions. The quality of the deposits depends very much on the source materials as well as the concentration of the same in the electrolyte. The deposition potential was varied from -0.4 to -0.75 V vs. SCE. The pH of the solution was adjusted to 1.5-2 using diluted sulphuric acid. Chloride salts containing bath yield good surface morphology, but there is always excess of the metallic content in the deposited films. Different growth procedures, like initial metallic layers of copper or indium, layers of copper selenide or indium selenide before the actual deposition of ternary chalcopyrite layers were attempted. Fabrication pathway, morphological and compositional changes due to the different precursor route has been analysed. The quality of the deposits prepared by one-step electrodeposition is better than the deposits with a two-stage process. The deposited films were characterized with XRD, SEM-EDAX, UV-visible spectroscopy and I- V characteristics. The deposited films were annealed in air as well as in nitrogen atmosphere. The influence of annealing temperature, environment and annealing time on the properties of the films are evaluated. Attempts were made to fabricate solar cell structure from the deposited absorber films. The structure of Mo/CuInSe 2/CdS/ZnO/Ni was characterized with surface, optical and electrical studies.

  14. Advanced organic composite materials for aircraft structures: Future program

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

  15. Health monitoring of composite structures throughout the life cycle

    NASA Astrophysics Data System (ADS)

    Chilles, James; Croxford, Anthony; Bond, Ian

    2016-04-01

    This study demonstrates the capability of inductively coupled piezoelectric sensors to monitor the state of health throughout the lifetime of composite structures. A single sensor which generated guided elastic waves was embedded into the stacking sequence of a large glass fiber reinforced plastic plate. The progress of cure was monitored by measuring variations in the amplitude and velocity of the waveforms reflected from the plate's edges. Baseline subtraction techniques were then implemented to detect barely visible impact damage (BVID) created by a 10 Joule impact, at a distance of 350 mm from the sensor embedded in the cured plate. To investigate the influence of mechanical loading on sensor performance, a single sensor was embedded within a glass fiber panel and subjected to tensile load. The panel was loaded up to a maximum strain of 1%, in increments of 0.1% strain. Guided wave measurements were recorded by the embedded sensor before testing, when the panel was under load, and after testing. The ultrasonic measurements showed a strong dependence on the applied load. Upon removal of the mechanical load the guided wave measurements returned to their original values recorded before testing. The results in this work show that embedded piezoelectric sensors can be used to monitor the state of health throughout the life-cycle of composite parts, even when subjected to relatively large strains. However the influence of load on guided wave measurements has implications for online monitoring using embedded piezoelectric transducers.

  16. Composite fuselage shell structures research at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Starnes, James H., Jr.; Shuart, Mark J.

    1992-01-01

    Fuselage structures for transport aircraft represent a significant percentage of both the weight and the cost of these aircraft primary structures. Composite materials offer the potential for reducing both the weight and the cost of transport fuselage structures, but only limited studies of the response and failure of composite fuselage structures have been conducted for transport aircraft. The behavior of these important primary structures must be understood, and the structural mechanics methodology for analyzing and designing these complex stiffened shell structures must be validated in the laboratory. The effects of local gradients and discontinuities on fuselage shell behavior and the effects of local damage on pressure containment must be thoroughly understood before composite fuselage structures can be used for commercial aircraft. This paper describes the research being conducted and planned at NASA LaRC to help understand the critical behavior or composite fuselage structures and to validate the structural mechanics methodology being developed for stiffened composite fuselage shell structure subjected to combined internal pressure and mechanical loads. Stiffened shell and curved stiffened panel designs are currently being developed and analyzed, and these designs will be fabricated and then tested at Langley to study critical fuselage shell behavior and to validate structural analysis and design methodology. The research includes studies of the effects of combined internal pressure and mechanical loads on nonlinear stiffened panel and shell behavior, the effects of cutouts and other gradient-producing discontinuities on composite shell response, and the effects of local damage on pressure containment and residual strength. Scaling laws are being developed that relate full-scale and subscale behavior of composite fuselage shells. Failure mechanisms are being identified and advanced designs will be developed based on what is learned from early results from

  17. Damage progression in mechanically fastened composite structural joints

    SciTech Connect

    Minnetyan, L.; Chamis, C.C.; Murthy, P.L.N.

    1994-12-31

    Progressive damage and fracture of a bolted graphite/epoxy composite laminate is evaluated via computational simulation. The objective of this paper is to demonstrate a new methodology that scales up constituent material properties, stress and strain limits to the structure level to evaluate the overall damage and fracture propagation for mechanically fastened composite structures. An integrated computer code is used for the simulation of structural degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulation. Results show the damage progression sequence and structural fracture resistance during different degradation stages. The effect of fastener spacing is investigated with regard to the structural durability of a bolted joint.

  18. Composite Grids for Reinforcement of Concrete Structures.

    DTIC Science & Technology

    1998-06-01

    composites has been the subject of investigation for a long time (Glaster et al. 1983, 1984; Budelman & Rostasy 1993). Tunik and Tomashevskii (1974...on Experimental Mechanics, Boston MA, pp 329-335. Budelman, H., and Rostasy , F.S., (1993). "Creep Rupture Behavior of FRP Elements for Prestressed

  19. Multifunctional Composite Nanofibers for Smart Structures

    DTIC Science & Technology

    2011-10-13

    demonstration 4.1 Nanofiber based supercapacitor, Lithium Ion battery and transparent electrodes for solar cell (student – Nicole Lee; collaborator...compensating power deficiencies of batteries or fuel cells in hybrid vehicles. Reducing their cost and increasing energy density are major...challenge for enabling next generation solar cell devices. High performance fibrous composite materials based on a carrier polymer with embedded functional

  20. Compositional dependence of charge carrier transport in kesterite Cu2ZnSnS4 solar cells

    NASA Astrophysics Data System (ADS)

    Just, Justus; Nichterwitz, Melanie; Lützenkirchen-Hecht, Dirk; Frahm, Ronald; Unold, Thomas

    2016-12-01

    Cu2ZnSnS4 solar cells deposited by thermal co-evaporation have been characterized structurally and electronically to determine the dependence of the electronic properties on the elemental composition of the kesterite phase, which can significantly deviate from the total sample composition. To this end, the kesterite phase content and composition were determined by a combination of X-ray fluorescence and X-ray absorption measurements. The electronic properties, such as carrier density and minority carrier diffusion length, were determined by electron beam induced current measurements and capacitance-voltage profiling. The charge-carrier transport properties are found to strongly depend on the Cu/(Sn+Zn) ratio of the kesterite phase. For the Cu-poor sample, a minority carrier diffusion length of 270 nm and a total collection length of approx. 500 nm are deduced, indicating that current collection should not be an issue in thin devices.

  1. Nano-structured polymer composites and process for preparing same

    DOEpatents

    Hillmyer, Marc; Chen, Liang

    2013-04-16

    A process for preparing a polymer composite that includes reacting (a) a multi-functional monomer and (b) a block copolymer comprising (i) a first block and (ii) a second block that includes a functional group capable of reacting with the multi-functional monomer, to form a crosslinked, nano-structured, bi-continuous composite. The composite includes a continuous matrix phase and a second continuous phase comprising the first block of the block copolymer.

  2. Robustness of composite pulse sequences to time-dependent noise

    NASA Astrophysics Data System (ADS)

    Kabytayev, Chingiz; Green, Todd J.; Khodjasteh, Kaveh; Viola, Lorenza; Biercuk, Michael J.; Brown, Kenneth R.

    2014-03-01

    Quantum control protocols can minimize the effect of noise sources that reduce the quality of quantum operations. Originally developed for NMR, composite pulse sequences correct for unknown static control errors . We study these compensating pulses in the general case of time-varying Gaussian control noise using a filter-function approach and detailed numerics. Three different noise models were considered in this work: amplitude noise, detuning noise and simultaneous presence of both noises. Pulse sequences are shown to be robust to noise up to frequencies as high as ~10% of the Rabi frequency. Robustness of pulses designed for amplitude noise is explained using a geometric picture that naturally follows from filter function. We also discuss future directions including new pulses correcting for noise of certain frequency. True J. Merrill and Kenneth R. Brown. arXiv:1203.6392v1. In press Adv. Chem. Phys. (2013)

  3. Stiff, Strong Splice For A Composite Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Schmaling, D.

    1991-01-01

    New type of splice for composite sandwich structure reduces peak shear stress in structure. Layers of alternating fiber orientation interposed between thin ears in adhesive joint. Developed for structural joint in spar of helicopter rotor blade, increases precision of control over thickness of adhesive at joint. Joint easy to make, requires no additional pieces, and adds little weight.

  4. Progressive failure analysis of fibrous composite materials and structures

    NASA Technical Reports Server (NTRS)

    Bahei-El-din, Yehia A.

    1990-01-01

    A brief description is given of the modifications implemented in the PAFAC finite element program for the simulation of progressive failure in fibrous composite materials and structures. Details of the memory allocation, input data, and the new subroutines are given. Also, built-in failure criteria for homogeneous and fibrous composite materials are described.

  5. Affordable, Lightweight, Highly Conductive Polymer Composite Electronic Packaging Structures

    DTIC Science & Technology

    1996-06-01

    matrix composite materials and how various material designs can be utilized in various structural/thermal configurations to produce electronic housings and...conductive polymer composite electronic packaging (i.e., electronic housings and heat sinks). The research will center on predominately polymer

  6. Material Distribution Optimization for the Shell Aircraft Composite Structure

    NASA Astrophysics Data System (ADS)

    Shevtsov, S.; Zhilyaev, I.; Oganesyan, P.; Axenov, V.

    2016-09-01

    One of the main goal in aircraft structures designing isweight decreasing and stiffness increasing. Composite structures recently became popular in aircraft because of their mechanical properties and wide range of optimization possibilities.Weight distribution and lay-up are keys to creating lightweight stiff strictures. In this paperwe discuss optimization of specific structure that undergoes the non-uniform air pressure at the different flight conditions and reduce a level of noise caused by the airflowinduced vibrations at the constrained weight of the part. Initial model was created with CAD tool Siemens NX, finite element analysis and post processing were performed with COMSOL Multiphysicsr and MATLABr. Numerical solutions of the Reynolds averaged Navier-Stokes (RANS) equations supplemented by k-w turbulence model provide the spatial distributions of air pressure applied to the shell surface. At the formulation of optimization problem the global strain energy calculated within the optimized shell was assumed as the objective. Wall thickness has been changed using parametric approach by an initiation of auxiliary sphere with varied radius and coordinates of the center, which were the design variables. To avoid a local stress concentration, wall thickness increment was defined as smooth function on the shell surface dependent of auxiliary sphere position and size. Our study consists of multiple steps: CAD/CAE transformation of the model, determining wind pressure for different flow angles, optimizing wall thickness distribution for specific flow angles, designing a lay-up for optimal material distribution. The studied structure was improved in terms of maximum and average strain energy at the constrained expense ofweight growth. Developed methods and tools can be applied to wide range of shell-like structures made of multilayered quasi-isotropic laminates.

  7. Composition and Temperature Dependence of Shear Viscosity of Hydrocarbon Mixtures

    DTIC Science & Technology

    1980-07-01

    model for viscosity of liquids , we feel that this is a very good correlation between molecular structure and viscosity, and it appears then that the...B. Thole, "The Viscosity of Liquids ," Longmans, Green and Co., London (1914). 15. W. R. Gambill, Chem. Eng, 66, 151 (1959) 16. P. K. Katti and M. M

  8. Structural arrangement trade study. Volume 3: Reusable Hydrogen Composite Tank System (RHCTS) and Graphite Composite Primary Structures (GCPS). Addendum

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This volume is the third of a 3 volume set that addresses the structural trade study plan that will identify the most suitable structural configuration for an SSTO winged vehicle capable of delivering 25,000 lbs to a 220 nm circular orbit at 51.6 deg inclination. The most suitable Reusable Hydrogen Composite Tank System (RHCTS), and Graphite Composite Tank System (GCPS) composite materials for intertank, wing and thrust structures are identified. Vehicle resizing charts, selection criteria and back-up charts, parametric costing approach and the finite element method analysis are discussed.

  9. Embedded Sensor Array Development for Composite Structure Integrity Monitoring

    SciTech Connect

    Kumar, A.; Bryan, W. L.; Clonts, L. G.; Franks, S.

    2007-06-26

    The purpose of this Cooperative Research and Development Agreement (CRADA) between UT-Battelle, LLC (the "Contractor") and Accellent Technologies, Inc. (the "Participant") was for the development of an embedded ultrasonic sensor system for composite structure integrity monitoring.

  10. Failure Analysis and Mechanisms of Failure of Fibrous Composite Structures

    NASA Technical Reports Server (NTRS)

    Noor, A. K. (Compiler); Shuart, M. J. (Compiler); Starnes, J. H., Jr. (Compiler); Williams, J. G. (Compiler)

    1983-01-01

    The state of the art of failure analysis and current design practices, especially as applied to the use of fibrous composite materials in aircraft structures is discussed. Deficiencies in these technologies are identified, as are directions for future research.

  11. Teaching Writing: The Underlying Structure of Composition Courses.

    ERIC Educational Resources Information Center

    Halpern, Jeanne W.

    This paper identifies and describes the five components that underlie the structure of any advanced composition course: audience, purpose, voice, organization, and polish. Each component is illustrated with examples from technical writing, business writing, journalism, and academic writing. (FL)

  12. Health Monitoring System for Composite Structures

    NASA Technical Reports Server (NTRS)

    Tang, S. S.; Riccardella, P. C.; Andrews, R. J.; Grady, J. E.; Mucciaradi, A. N.

    1996-01-01

    An automated system was developed to monitor the health status of composites. It uses the vibration characteristics of composites to identify a component's damage condition. The vibration responses are characterized by a set of signal features defined in the time, frequency and spatial domains. The identification of these changes in the vibration characteristics corresponding to different health conditions was performed using pattern recognition principles. This allows efficient data reduction and interpretation of vast amounts of information. Test components were manufactured from isogrid panels to evaluate performance of the monitoring system. The components were damaged by impact to simulate different health conditions. Free vibration response was induced by a tap test on the test components. The monitoring system was trained using these free vibration responses to identify three different health conditions. They are undamaged vs. damaged, damage location and damage zone size. High reliability in identifying the correct component health condition was achieved by the monitoring system.

  13. Fatigue Prediction for Composite Materials and Structures

    DTIC Science & Technology

    2005-10-01

    Eugenio OÑATE CIMNE (International Center for Numerical Methods in Engineering) Building C-1, Campus Nord UPC -C/ Gran Capitán s/n 08034 Barcelona...SPAIN * salomon@cimne.upc.edu ABSTRACT The objective of this paper is to present a new computational methodology for predicting the durability of... methodology is validated using experimental data from tests on CFRR composite material samples. 1.0 INTRODUCTION Fatigue is defined as "the process

  14. Composite Structures Damage Tolerance Analysis Methodologies

    NASA Technical Reports Server (NTRS)

    Chang, James B.; Goyal, Vinay K.; Klug, John C.; Rome, Jacob I.

    2012-01-01

    This report presents the results of a literature review as part of the development of composite hardware fracture control guidelines funded by NASA Engineering and Safety Center (NESC) under contract NNL04AA09B. The objectives of the overall development tasks are to provide a broad information and database to the designers, analysts, and testing personnel who are engaged in space flight hardware production.

  15. Self-healing sandwich composite structures

    NASA Astrophysics Data System (ADS)

    Fugon, D.; Chen, C.; Peters, K.

    2012-04-01

    Previous research demonstrated that a thin self-healing layer is effective in recovering partial sandwich composite performance after an impact event. Many studies have been conducted that show the possibility of using Fiber Bragg Grating (FBG) sensors to monitor the cure of a resin through strain and temperature monitoring. For this experiment, FBG sensors were used to monitor the curing process of a self-healing layer within a twelve-layer fiberglass laminate after impact. First, five self-healing sandwich composite specimens were manufactured. FBG sensors were embedded between the fiberglass and foam core. Then the fiberglass laminate was impacted with the use of a drop tower and the curing process was monitored. The collected data was used to compare the cure of the resin and fiberglass alone to the cure of the resin from a self-healing specimen. For the low viscosity resin system tested, these changes were not sufficiently large to identify different polymerization states in the resin as it cured. These results indicate that applying different resin systems might increase the efficiency of the self-healing in the sandwich composites.

  16. Brain Structural Substrates of Reward Dependence during Behavioral Performance

    PubMed Central

    Hamann, Janne M.; Averbeck, Bruno B.

    2014-01-01

    Interindividual differences in the effects of reward on performance are prevalent and poorly understood, with some individuals being more dependent than others on the rewarding outcomes of their actions. The origin of this variability in reward dependence is unknown. Here, we tested the relationship between reward dependence and brain structure in healthy humans. Subjects trained on a visuomotor skill-acquisition task and received performance feedback in the presence or absence of reward. Reward dependence was defined as the statistical trial-by-trial relation between reward and subsequent performance. We report a significant relationship between reward dependence and the lateral prefrontal cortex, where regional gray-matter volume predicted reward dependence but not feedback alone. Multivoxel pattern analysis confirmed the anatomical specificity of this relationship. These results identified a likely anatomical marker for the prospective influence of reward on performance, which may be of relevance in neurorehabilitative settings. PMID:25471581

  17. Echinococcus granulosus Antigen B Structure: Subunit Composition and Oligomeric States

    PubMed Central

    Monteiro, Karina M.; Cardoso, Mateus B.; Follmer, Cristian; da Silveira, Nádya P.; Vargas, Daiani M.; Kitajima, Elliot W.; Zaha, Arnaldo; Ferreira, Henrique B.

    2012-01-01

    Background Antigen B (AgB) is the major protein secreted by the Echinococcus granulosus metacestode and is involved in key host-parasite interactions during infection. The full comprehension of AgB functions depends on the elucidation of several structural aspects that remain unknown, such as its subunit composition and oligomeric states. Methodology/Principal Findings The subunit composition of E. granulosus AgB oligomers from individual bovine and human cysts was assessed by mass spectrometry associated with electrophoretic analysis. AgB8/1, AgB8/2, AgB8/3 and AgB8/4 subunits were identified in all samples analyzed, and an AgB8/2 variant (AgB8/2v8) was found in one bovine sample. The exponentially modified protein abundance index (emPAI) was used to estimate the relative abundance of the AgB subunits, revealing that AgB8/1 subunit was relatively overrepresented in all samples. The abundance of AgB8/3 subunit varied between bovine and human cysts. The oligomeric states formed by E. granulosus AgB and recombinant subunits available, rAgB8/1, rAgB8/2 and rAgB8/3, were characterized by native PAGE, light scattering and microscopy. Recombinant subunits showed markedly distinct oligomerization behaviors, forming oligomers with a maximum size relation of rAgB8/3>rAgB8/2>rAgB8/1. Moreover, the oligomeric states formed by rAgB8/3 subunit were more similar to those observed for AgB purified from hydatid fluid. Pressure-induced dissociation experiments demonstrated that the molecular assemblies formed by the more aggregative subunits, rAgB8/2 and rAgB8/3, also display higher structural stability. Conclusions/Significance For the first time, AgB subunit composition was analyzed in samples from single hydatid cysts, revealing qualitative and quantitative differences between samples. We showed that AgB oligomers are formed by different subunits, which have distinct abundances and oligomerization properties. Overall, our findings have significantly contributed to increase the

  18. Development of hybrid composite co-pultruded structural members

    NASA Astrophysics Data System (ADS)

    Honickman, Hart Noah

    Fibre reinforced polymer (FRP) materials offer many advantages over conventional metallic structural materials due to their high specific strength and stiffness, long fatigue life, and resistance to environmental corrosion. However, these materials present some unique engineering challenges due to their anisotropy and heterogeneity. The connection of these composite parts to adjacent components often results in complex and counter-intuitive states of stress that can be quite difficult to model. Furthermore, since these materials are, in a sense, synthesized during the fabrication of the final part, the mechanical properties that can be expected from FRP structures are largely dependent upon highly skilled workmanship. Pultrusion is a manufacturing technique that is intended for the mass-production of long FRP parts having continuous cross-sectional geometry. Although it has not yet been optimized for the aerospace industry, with some qualification research, pultrusion may prove to offer many benefits over conventional methods of manufacturing composite aircraft parts. The present dissertation investigates the possibility of co-pultruding FRP parts with embedded non-FRP materials (such as metallic materials), which could serve as integral hard points to facilitate serviceable mechanical connections to adjacent parts. It is shown that these hybrid co-pultruded members offer substantial light-weighting benefits over conventional metallic components, while retaining the ability to employ serviceable mechanical fasteners. Simple unidimensional beam models are of great value when validating the results of complex finite element analyses of aircraft wing-stringers, or other similar structural members. It is demonstrated in the present dissertation that classical unidimensional beam-type analytical models often yield unconservative predictions (over-predictions) of stiffness and elastic stability when used for the analyses of FRP beams and columns. In fact, specific

  19. Flight-service evaluation of composite structural components

    NASA Technical Reports Server (NTRS)

    Dexter, H. B.

    1973-01-01

    A review of programs aimed at flight-service evaluation of composite materials in various applications is presented. These flight-service programs are expected to continue for up to 5 years and include selective reinforcement of an airplane center wing box a helicopter tail cone, and composite replacements for commercial aircraft spoilers and fairings. These longtime flight-service programs will help provide the necessary information required by commercial airlines to commit advanced composites to aircraft structures with confidence. Results of these programs will provide information concerning the stability of composite materials when subjected to various flight environments.

  20. Structural health monitoring of co-cured composite structures using FBG sensors

    NASA Astrophysics Data System (ADS)

    Sundaram, Ramesh; Kamath, G. M.; Gupta, Nitesh; Rao, M. Subba

    2005-05-01

    Structural Health Monitoring (SHM) of aircraft structures, especially composite structures, has assumed increased significance on considerations of safety and costs. With the advent of co-cured structures, wherein bonded joints are replacing bolted joints there is a concern regarding skin-stiffener separation, which might not be detected unless a rigorous non-destructive testing (NDT) is done. It would hence be necessary to be able to detect and assess skin-stiffener separation in composite structures before it reaches the critical size. One of the health monitoring strategies is through strain monitoring using fibre optic strain sensors such as Fibre Bragg Grating (FBG) sensors. The first aspect that needs to be addressed is the characterization of the FBG sensors. Issues of embedment in composites have also to be addressed. Before evolving a damage detection strategy, the sensitivity of the structural strain to skin-stiffener separations must be clearly understood and quantified. This paper presents the analysis and experiments done with a composite test box to study the effect of skin-stiffener separation on the strain behaviour. The box consists of two skins stiffened with spars made of Bi-Directional (BD) glass-epoxy prepreg material. The spars are bolted to the skins and removing suitable number of bolts simulates 'de-bonds'. The strains of the healthy box are compared with the unhealthy box. The strains in the experiments are monitored using both strain gauges and Fibre Bragg Grating (FBG) sensors. The experimental results show that there is significant change in the measured strain near and away from the debond location. The finite element analysis of the box is done using ABAQUS and the analysis is validated with the experimental results. A neural network based methodology is developed here to detect skin-stiffener debonds in structures. A multi-layer perceptron (MLP) neural network with a feed forward back propagation algorithm is used to determine the

  1. Flexible ultrasonic array system for inspecting thick composite structures

    NASA Astrophysics Data System (ADS)

    Frankle, Robert S.; Rose, Douglas N.

    1995-06-01

    Composite materials, which have commonly been used in recreational boats, are now being applied to more challenging marine applications. The high specific stiffness and strength of composites translates into increased range and payload. Composites offer the added benefits of corrosion and erosion resistance, fatigue and wear resistance, reduced signature, and reduced maintenance and life cycle costs as compared to traditional metallic structures. Although ultrasonic techniques are typically used to inspect composite structures, thick composites, such as those used in marine applications, are difficult to inspect with ordinary ultrasonic methods. An ultrasonic inspection system is being developed for the US Army to inspect thick composite materials for future armored vehicles. This system is an extension of the existing PARIS flexible array ultrasonic inspection system, which was originally developed for inspecting thin composite aircraft structures. The extension is designed to increase ultrasonic penetration by 1) fabricating an array that operates at lower frequency and higher voltage, and 2) employing a synthetic pulse technique. The flexible array can rapidly inspect large areas and produce images of the inspection results that are easy to interpret. This paper describes the ultrasonic inspection system and presents examples of inspection results from both thick and thin composite materials.

  2. Simulated orbital impact of multi-wall composite structures

    NASA Technical Reports Server (NTRS)

    Walker, Eve J.; Schonberg, William P.

    1992-01-01

    This paper presents the results of an experimental investigation in which several different composite materials were tested for their ability to prevent the perforation of multiwall systems under hypervelocity projectile impact. The damage in the composite specimens is compared to the damage in aluminum specimens of similar geometry and weight caused by hypervelocity projectiles with similar impact energies. The analysis shows that using composite materials in combination with metallic materials in multiwall structures can increase the protection afforded a spacecraft against perforation by orbital debris over that provided by traditional, purely metallic multiwall structures.

  3. Nonlinear analyses of composite aerospace structures in sonic fatigue

    NASA Technical Reports Server (NTRS)

    Mei, Chuh

    1992-01-01

    The primary research effort of this project is the development of analytical methods for the prediction of nonlinear random response of composite aerospace structures subjected to combined acoustic and thermal loads. The progress, accomplishments, and future plans of three random response research topics are discussed, namely acoustics-structure interactions using boundary/finite element methods, nonlinear vibrations of beams and composite plates under harmonic and random excitations, and numerical simulation of the nonlinear response of composite plates under combined thermal and acoustic loading.

  4. Structural features of ZnxOy/nanosilica composites

    NASA Astrophysics Data System (ADS)

    Gun'ko, V. M.; Bogatyrov, V. M.; Oranska, O. I.; Borysenko, L. I.; Skubiszewska-Zięba, J.; Książek, A.; Leboda, R.

    2013-07-01

    Nanocomposites with nanosilica A380 (SBET = 378 m2/g) and grafted ZnO or/and zinc silicate were prepared using zinc acetate adsorbed onto nanosilica and then treated at 600-900 °C. The samples studied using a variety of methods demonstrated the dependences of the textural and structural characteristics and phase transformations on the amounts of adsorbed precursor and treatment conditions. Thermodestruction of zinc acetate Zn(ac)2 at 600 °C results in the formation of ZnO which is amorphous according to XRD data. However, HRTEM images show the presence of a small amount of ZnO crystallites of 2-5 nm in size. A portion of surface silanols interacts with adsorbed Zn-containing compounds to form Sisbnd Osbnd Zn bonds, a number of which increases with increasing Zn(ac)2 content and heating temperature. Heating at 800-900 °C leads to transformation of ZnO and other structures into crystalline zinc silicate β-Zn2SiO4 with larger particles more strongly packed in aggregates. The specific surface area of the composites decreases with increasing zinc content and heating temperature.

  5. Installation of adhesively bonded composites to repair carbon steel structure.

    SciTech Connect

    Roach, Dennis Patrick; Dunn, Dennis P.; Rackow, Kirk A.

    2003-02-01

    In the past decade, an advanced composite repair technology has made great strides in commercial aviation use. Extensive testing and analysis, through joint programs between the Sandia Labs FAA Airworthiness Assurance Center and the aviation industry, have proven that composite materials can be used to repair damaged aluminum structure. Successful pilot programs have produced flight performance history to establish the viability and durability of bonded composite patches as a permanent repair on commercial aircraft structures. With this foundation in place, efforts are underway to adapt bonded composite repair technology to civil structures. This paper presents a study in the application of composite patches on large trucks and hydraulic shovels typically used in mining operations. Extreme fatigue, temperature, erosive, and corrosive environments induce an array of equipment damage. The current weld repair techniques for these structures provide a fatigue life that is inferior to that of the original plate. Subsequent cracking must be revisited on a regular basis. It is believed that the use of composite doublers, which do not have brittle fracture problems such as those inherent in welds, will help extend the structure's fatigue life and reduce the equipment downtime. Two of the main issues for adapting aircraft composite repairs to civil applications are developing an installation technique for carbon steel structure and accommodating large repairs on extremely thick structures. This paper will focus on the first phase of this study which evaluated the performance of different mechanical and chemical surface preparation techniques. The factors influencing the durability of composite patches in severe field environments will be discussed along with related laminate design and installation issues.

  6. VARTM Process Modeling of Aerospace Composite Structures

    NASA Technical Reports Server (NTRS)

    Song, Xiao-Lan; Grimsley, Brian W.; Hubert, Pascal; Cano, Roberto J.; Loos, Alfred C.

    2003-01-01

    A three-dimensional model was developed to simulate the VARTM composite manufacturing process. The model considers the two important mechanisms that occur during the process: resin flow, and compaction and relaxation of the preform. The model was used to simulate infiltration of a carbon preform with an epoxy resin by the VARTM process. The model predicted flow patterns and preform thickness changes agreed qualitatively with the measured values. However, the predicted total infiltration times were much longer than measured most likely due to the inaccurate preform permeability values used in the simulation.

  7. In-service health monitoring of composite structures

    NASA Technical Reports Server (NTRS)

    Pinto, Gino A.; Ventres, C. S.; Ginty, Carol A.; Chamis, Christos C.

    1990-01-01

    The aerospace industry is witnessing a vast utilization of composites in critical structural applications and anticipates even more use of them in future aircraft. Therefore, a definite need exists for a composite health monitoring expert system to meet today's current needs and tomorrow's future demands. The primary goal for this conceptual health monitoring system is functional reliably for in-service operation in the environments of various composite structures. The underlying philosophy of this system is to utilize proven vibration techniques to assess the structural integrity of a fibrous composite. Statistical methods are used to determine if the variances in the measured data are acceptable for making a reliable decision on the health status of the composite. The flexible system allows for algorithms describing any composite fatigue or damage behavior characteristic to be provided as an input to the system. Alert thresholds and variances can also be provided as an input to this system and may be updated to allow for future changes/refinements in the composite's structural integrity behavior.

  8. Composite Blade Structural Analyzer (COBSTRAN) theoretical/programmer's manual

    NASA Technical Reports Server (NTRS)

    Aiello, Robert A.; Chamis, Christos C.

    1989-01-01

    This manual describes the organization and flow of data and analysis in the computer code, COBSTRAN (COmposite Blade STRuctural ANalyzer). This code combines composite mechanics and laminate theory with an internal data base of fiber and matrix properties and was developed for the design and analysis of composite turbofan and turboprop blades and composite wind turbine blades. Inputs to the code are constituent fiber and matrix material properties, factors reflecting the fabrication process, composite geometry and blade geometry. COBSTRAN performs the micromechanics and laminate analyses of these fiber composites and generates a NASTRAN finite element model of the blade. This manual describes the equations formulated and solved in the code and the function of each of the seventy-two subroutines. COBSTRAN is written in FORTRAN 77.

  9. Intrinsic manufacture of hollow thermoplastic composite/metal structures

    NASA Astrophysics Data System (ADS)

    Barfuss, Daniel; Grützner, Raik; Garthaus, Christian; Gude, Maik; Müller, Roland; Langrebe, Dirk

    2016-10-01

    In contrast to common and classical joining technologies for composite/metal hybrid structures such as bonding and riveting, profile and contour joints offer a promising potential for novel lightweight hybrid structures. First and foremost, joining systems with a form closure function enable to pass very high loads into rod- and tube-shaped fibre reinforced structures and achieve high degrees of material utilization for the composite part. This paper demonstrates the theoretical and technological principals for a resource efficient design and production of highly loaded thermoplastic composite profile structures with integrated metallic load introduction elements and a multi scale form closure. The hybrid structures are produced in an integral blow moulding process in which a braided tape-preform is simultaneously consolidated and formed into the metallic load introduction element. These metallic load introduction elements are manufactured in a two-stage process of external and internal hydroforming, after forming simulations have assured process stability for consistent quality.

  10. Quantification of uncertainties in the performance of smart composite structures

    NASA Technical Reports Server (NTRS)

    Shiao, Michael C.; Chamis, Christos C.

    1993-01-01

    A composite wing with spars, bulkheads, and built-in control devices is evaluated using a method for the probabilistic assessment of smart composite structures. Structural responses (such as change in angle of attack, vertical displacements, and stresses in regular plies with traditional materials and in control plies with mixed traditional and actuation materials) are probabilistically assessed to quantify their respective scatter. Probabilistic sensitivity factors are computed to identify those parameters that have a significant influence on a specific structural response. Results show that the uncertainties in the responses of smart composite structures can be quantified. Responses such as structural deformation, ply stresses, frequencies, and buckling loads in the presence of defects can be reliably controlled to satisfy specified design requirements.

  11. The scale dependence of single-nucleon shell structure

    SciTech Connect

    Somà, V.; Hergert, H.; Holt, J. D.

    2015-10-15

    We address the scale dependence of (effective) single-particle energies, non-observable quantities that are commonly used for interpreting nuclear structure observables measured in experiments and computed in many-body theories. We first demonstrate their scale dependence on a formal level, making them intrinsically theoretical objects, before illustrating this point via ab initio calculations in the oxygen isotopes. Finally, we consider a modified definition of effective single-particle energy and investigate its running properties.

  12. Structure analysis, fatigue testing, and lifetime prediction of composite steels

    NASA Astrophysics Data System (ADS)

    Sokolkin, Yu. V.; Chekalkin, A. A.; Babushkin, A. V.

    1998-05-01

    Composite steels prepared by technology of powder metallurgy are widely used as low cost parts with good resistance to wear, fracture, and corrosion. The development of powder composite steels is directly related to strength under vibration, fatigue stabilizing, and accurate lifetime prediction for actual composite topology. The fatigue behavior of powder steels was studied by experimental and numerical methods of composite mechanics and materials sciences. The chemical composition of composite steel is a pure iron powder as the base material and a handful of carbon, chromium, nickel, or phosphorus powders. The powder multi-component mixture is compacted by cold isostatic pressing to a rectangular form. The compactants are sintered in protective atmosphere. The microscale examination of the composite structure included an METAM-RV-21 metallographic optic microscope with a high-resolution ScanNexIIc scanner and an image processing package on the PC platform. The phase composition of powder steels has complex disordered topology with irregular ferrite/austenite grains, iron carbide inclusions, and pores. The microstructure images are treated according to the theory of stochastic processes as ergodic probability functions; statistical moments and a structural covariance function of the composite steels are given. The microscale stress-strain state of the composite steel is analyzed by finite element methods. The stiffness matrix of the composite steel is also presented together with stiffness matrices of ferrite/austenite grains, iron carbide inclusions, and pores as zero matrices. Endurance limits of the microstructural components are described by the Basquin or Coffin-Manson laws, respectively, as high and low cycle fatigue; cumulative microdamage in loading with a variable amplitude is taken from the Palmgren-Miner rule. Planar specimens were tested by console bending. Symmetric fatigue cycling was performed at a stable frequency of 20 Hz with endurance limits up

  13. Structural system identification of a composite shell

    SciTech Connect

    Red-Horse, J.R.; Carne, T.G.; James, G.H.; Witkowski, W.R.

    1991-01-01

    Structural system identification is undergoing a period of renewed interest. Probabilistic approaches to physical parameter identification in analysis finite element models make uncertainty in test results an important issue. In this paper, we investigate this issue with a simple, though in many ways representative, structural system. The results of two modal parameter identification techniques are compared and uncertainty estimates, both through bias and random errors, are quantified. The importance of the interaction between test and analysis is also highlighted. 25 refs.

  14. Structural system identification of a composite shell

    SciTech Connect

    Red-Horse, J.R.; Carne, T.G.; James, G.H.; Witkowski, W.R.

    1991-12-31

    Structural system identification is undergoing a period of renewed interest. Probabilistic approaches to physical parameter identification in analysis finite element models make uncertainty in test results an important issue. In this paper, we investigate this issue with a simple, though in many ways representative, structural system. The results of two modal parameter identification techniques are compared and uncertainty estimates, both through bias and random errors, are quantified. The importance of the interaction between test and analysis is also highlighted. 25 refs.

  15. Active Structural Fibers for Multifunctional Composite Materials

    DTIC Science & Technology

    2014-05-06

    1. Lin, Y., Zhi, Z. and Sodano, 2012, “Barium Titanate and Barium Strontium Titanate Coated Carbon Fibers for Multifunctional Structural Capacitors...Multifunctional Structural Capacitors Consisting of Barium Titanate and Barium Strontium Titanate Coated Carbon Fibers, 18 th International Conference on... Strontium Titanate Coated SiC Fibers,” Electronic Materials and Applications 2011, Jan. 19 th –21 st Orlando, FL (Invited). 9. Lin, Y., Shaffer

  16. Composition and carrier-concentration dependence of the electronic structure of InyGa1-yAs1-xNx films with nitrogen mole fraction of less than 0.012

    NASA Astrophysics Data System (ADS)

    Kang, Youn-Seon; Robins, Lawrence H.; Birdwell, Anthony G.; Shapiro, Alexander J.; Thurber, W. Robert; Vaudin, Mark D.; Fahmi, M. M. E.; Bryson, Damian; Mohammad, S. Noor

    2005-11-01

    The electronic structure of Si-doped InyGa1-yAs1-xNx films on GaAs substrates, grown by nitrogen-plasma-assisted molecular-beam epitaxy, was examined by photoreflectance (PR) spectroscopy at temperatures between 20 and 300 K. The films were approximately 0.5 μm thick and had nitrogen mole fraction between x=0.0014 and x=0.012, measured indirectly by a secondary-ion-mass spectrometry calibration; indium mole fraction between y=0.052 and y=0.075, measured by electron-dispersive x-ray spectroscopy; and carrier concentration between 2×1016 and 1.1×1018 cm-3, measured by Hall effect. Three critical-point transitions were identified by PR: the fundamental band gap (highest valence band to the lowest conduction band); the spin-orbit split valence band to the lowest conduction band; and the highest valence band to a nitrogen impurity band (above the lowest conduction band). The measured critical-point energies were described by a band anticrossing (BAC) model with the addition of a Burstein-Moss band-filling term. The fitted BAC parameters were similar to previously reported values. The N impurity level was located 0.3004+/-0.0101 eV above the conduction-band edge at 20 K and 0.3286+/-0.0089 eV above the conduction-band edge at 295 K. The BAC interaction parameter was 2.588+/-0.071 eV. From the small magnitude of the Burstein-Moss energy shift with increasing carrier concentration, it was inferred that the carrier concentration probed by PR is reduced from the bulk (Hall-effect) carrier concentration by a reduction factor of 0.266+/-0.145. The PR lines broadened with increasing carrier concentration; the line broadening tracked the predicted Burstein-Moss energy shift for the bulk carrier concentration. The surface-normal lattice constants of the films were measured by x-ray diffraction. Comparison of the measured lattice constants with Vegard's law showed the presence of tensile strain (in the surface-normal direction) with magnitude between 1.5×10-3 and 3.0×10

  17. Structural health monitoring of composite repair patches in bridge rehabilitation

    NASA Astrophysics Data System (ADS)

    Wu, Zhanjun; Ghosh, Kumar; Qing, Xinlin; Karbhari, Vistasp; Chang, Fu-Kuo

    2006-03-01

    In recent years, there are many issues involving safety on old bridges, aircrafts and other structures, which threaten the lives of the people using those structures, as well as the structures themselves. To prevent future failure, various measures are being taken. Structure rehabilitations with carbon fiber reinforced composite patches have been adopted and demonstrated to be an excellent way to enhance/repair the structures and prolong the service life. However, there are still many problems residing in this kind of technology that remain unsolved, for example, the failure of the interface between composite repair patches and their host structures. This is a critical issue that must be addressed in order to show the viability of composite patches. In order to study debond occurring between composite repair patches and their host structures, a structure health monitoring scheme was demonstrated on a concrete bridge model in the laboratory. The system is based on active sensing with diagnostic lamb waves, in which piezoelectric transducers are used as both sensors and actuators. In the test, six SMART Layers, each having eight piezoelectirc transducers, were integrated with two composite repair strips on the deck slab of the concrete bridge model. For the three diagnostic layers with each composite repair patch, two layers were bonded on the top surface of the patch, and the other is embedded at the interface between the composite repair patch and the deck slab of the concrete bridge model. The loading procedure of the test included three phases. First, the bridge model was preloaded to initiate cracks on the deck slabs and the repair patches were then implemented. Second, the load was raised to reach the shear capacity of the girders of the bridge model and then the repair patches were implemented on those girders. Lastly, the structure was loaded to damage the deck slabs. During the test, the initiation and development of debond between composite repair patches

  18. Large Composite Structures Processing Technologies for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Clinton, R. G., Jr.; Vickers, J. H.; McMahon, W. M.; Hulcher, A. B.; Johnston, N. J.; Cano, R. J.; Belvin, H. L.; McIver, K.; Franklin, W.; Sidwell, D.

    2001-01-01

    Significant efforts have been devoted to establishing the technology foundation to enable the progression to large scale composite structures fabrication. We are not capable today of fabricating many of the composite structures envisioned for the second generation reusable launch vehicle (RLV). Conventional 'aerospace' manufacturing and processing methodologies (fiber placement, autoclave, tooling) will require substantial investment and lead time to scale-up. Out-of-autoclave process techniques will require aggressive efforts to mature the selected technologies and to scale up. Focused composite processing technology development and demonstration programs utilizing the building block approach are required to enable envisioned second generation RLV large composite structures applications. Government/industry partnerships have demonstrated success in this area and represent best combination of skills and capabilities to achieve this goal.

  19. Self-healing structural composites with electromagnetic functionality

    NASA Astrophysics Data System (ADS)

    Plaisted, Thomas A.; Vakil Amirkhizi, Alireza; Arbelaez, Diego; Nemat-Nasser, Syrus C.; Nemat-Nasser, Sia

    2003-08-01

    We have incorporated arrays of conductive electromagnetic scattering elements such as straight copper wires and copper coils into fiber-reinforced polymer composites, resulting in materials with required structural and further electromagnetic functionality. The scattering elements provide controlled electromagnetic response for tasks such as filtering and may be used to tune the overall index of refraction of the composite. Integration of these metallic elements into traditional fiber-reinforced polymer composites has introduced other opportunities for multifunctionality in terms of self-healing, thermal transport and perhaps sensing applications. Such functionalities are the result of fiber/wire integration through textile braiding and weaving, combined with a new polymer matrix that has the ability to heal internal cracking through thermo-reversible covalent bonds. Multifunctional composites of this kind enhance the role of structural materials from mere load-bearing systems to lightweight structures of good thermo-mechanical attributes that also have electromagnetic and other functionalities.

  20. Kinetic-Impact Asteroid Defense: Dependence on Porosity and Composition

    NASA Astrophysics Data System (ADS)

    Gisler, G. R.; Ferguson, J. M.; Plesko, C. S.; Weaver, R.

    2015-12-01

    In this work we study the deflection of hazardous near-earth asteroids using a kinetic impactor. The momentum delivered to the asteroid can be greater than the momentum of the impactor because of the reaction force produced by ablation from the impact crater. We use an adaptive-mesh hydrocode to study the momentum-enhancement factor, or beta, varying the assumptions regarding the equation of state, strength, and porosity of the target. Spall from the back side of the asteroid, which partly counters the favorable effect of ablation, is also included in the calculations. The efficiency is shown to be most strongly dependent on the asteroid's porosity, which unfortunately is the most difficult quantity to obtain via remote observations. This study is applied both to the proposed deflection of the 150-meter diameter moon of the binary asteroid 65803 Didymos by the AIDA/DART mission, and to the potential deflection of the 492-meter diameter asteroid 101955 Bennu, which has some possible Earth impacts late in the 22nd century, and is the target of the planned OSIRIS-Rex mission. Figures of merit from both these studies include the bulk momentum imparted to the asteroid and the degree to which the asteroid is disrupted. (LA-UR-15-26214)

  1. On the Mechanical Behavior of Advanced Composite Material Structures

    NASA Astrophysics Data System (ADS)

    Vinson, Jack

    During the period between 1993 and 2004, the author, as well as some colleagues and graduate students, had the honor to be supported by the Office of Naval Research to conduct research in several aspects of the behavior of structures composed of composite materials. The topics involved in this research program were numerous, but all contributed to increasing the understanding of how various structures that are useful for marine applications behaved. More specifically, the research topics focused on the reaction of structures that were made of fiber reinforced polymer matrix composites when subjected to various loads and environmental conditions. This included the behavior of beam, plate/panel and shell structures. It involved studies that are applicable to fiberglass, graphite/carbon and Kevlar fibers imbedded in epoxy, polyester and other polymeric matrices. Unidirectional, cross-ply, angle ply, and woven composites were involved, both in laminated, monocoque as well as in sandwich constructions. Mid-plane symmetric as well as asymmetric laminates were studied, the latter involving bending-stretching coupling and other couplings that only can be achieved with advanced composite materials. The composite structures studied involved static loads, dynamic loading, shock loading as well as thermal and hygrothermal environments. One major consideration was determining the mechanical properties of composite materials subjected to high strain rates because the mechanical properties vary so significantly as the strain rate increases. A considerable number of references are cited for further reading and study for those interested.

  2. A procedure for utilization of a damage-dependent constitutive model for laminated composites

    NASA Technical Reports Server (NTRS)

    Lo, David C.; Allen, David H.; Harris, Charles E.

    1992-01-01

    Described here is the procedure for utilizing a damage constitutive model to predict progressive damage growth in laminated composites. In this model, the effects of the internal damage are represented by strain-like second order tensorial damage variables and enter the analysis through damage dependent ply level and laminate level constitutive equations. The growth of matrix cracks due to fatigue loading is predicted by an experimentally based damage evolutionary relationship. This model is incorporated into a computer code called FLAMSTR. This code is capable of predicting the constitutive response and matrix crack damage accumulation in fatigue loaded laminated composites. The structure and usage of FLAMSTR are presented along with sample input and output files to assist the code user. As an example problem, an analysis of crossply laminates subjected to two stage fatigue loading was conducted and the resulting damage accumulation and stress redistribution were examined to determine the effect of variations in fatigue load amplitude applied during the first stage of the load history. It was found that the model predicts a significant loading history effect on damage evolution.

  3. Transition from glass to graphite in manufacture of composite aircraft structure

    NASA Technical Reports Server (NTRS)

    Buffum, H. E.; Thompson, V. S.

    1978-01-01

    The transition from fiberglass reinforced plastic composites to graphite reinforced plastic composites is described. Structural fiberglass design and manufacturing background are summarized. How this experience provides a technology base for moving into graphite composite secondary structure and then to composite primary structure is considered. The technical requirements that must be fulfilled in the transition from glass to graphite composite structure are also included.

  4. Nonlinear analysis for high-temperature multilayered fiber composite structures. M.S. Thesis; [turbine blades

    NASA Technical Reports Server (NTRS)

    Hopkins, D. A.

    1984-01-01

    A unique upward-integrated top-down-structured approach is presented for nonlinear analysis of high-temperature multilayered fiber composite structures. Based on this approach, a special purpose computer code was developed (nonlinear COBSTRAN) which is specifically tailored for the nonlinear analysis of tungsten-fiber-reinforced superalloy (TFRS) composite turbine blade/vane components of gas turbine engines. Special features of this computational capability include accounting of; micro- and macro-heterogeneity, nonlinear (stess-temperature-time dependent) and anisotropic material behavior, and fiber degradation. A demonstration problem is presented to mainfest the utility of the upward-integrated top-down-structured approach, in general, and to illustrate the present capability represented by the nonlinear COBSTRAN code. Preliminary results indicate that nonlinear COBSTRAN provides the means for relating the local nonlinear and anisotropic material behavior of the composite constituents to the global response of the turbine blade/vane structure.

  5. Shoulder pain and time dependent structure in wheelchair propulsion variability.

    PubMed

    Jayaraman, Chandrasekaran; Moon, Yaejin; Sosnoff, Jacob J

    2016-07-01

    Manual wheelchair propulsion places considerable repetitive mechanical strain on the upper limbs leading to shoulder injury and pain. While recent research indicates that the amount of variability in wheelchair propulsion and shoulder pain may be related. There has been minimal inquiry into the fluctuation over time (i.e. time-dependent structure) in wheelchair propulsion variability. Consequently the purpose of this investigation was to examine if the time-dependent structure in the wheelchair propulsion parameters are related to shoulder pain. 27 experienced wheelchair users manually propelled their own wheelchair fitted with a SMARTWheel on a roller at 1.1m/s for 3min. Time-dependent structure of cycle-to-cycle fluctuations in contact angle and inter push time interval was quantified using sample entropy (SampEn) and compared between the groups with/without shoulder pain using non-parametric statistics. Overall findings were, (1) variability observed in contact angle fluctuations during manual wheelchair propulsion is structured (Z=3.15;p<0.05), (2) individuals with shoulder pain exhibited higher SampEn magnitude for contact angle during wheelchair propulsion than those without pain (χ(2)(1)=6.12;p<0.05); and (3) SampEn of contact angle correlated significantly with self-reported shoulder pain (rs (WUSPI) =0.41;rs (VAS)=0.56;p<0.05). It was concluded that the time-dependent structure in wheelchair propulsion may provide novel information for tracking and monitoring shoulder pain.

  6. Modeling the time-dependent flexural response of wood-plastic composite materials

    NASA Astrophysics Data System (ADS)

    Hamel, Scott E.

    Wood-plastic composites (WPCs) are moisture sensitive bimodal anisotropic nonlinear viscoelastic materials, with time and temperature having the greatest effect on mechanical behavior. As WPC producers seek to manufacture structural bending members, such as beams and joists, it is important that the material's time and temperature-dependent mechanical behavior be understood and characterized. The complicated time-dependent behavior means that WPC bending deflections cannot be adequately predicted for even practical design purposes using simple linear-elastic models. Instead, mechanics-based models that incorporate the observed time-dependent and nonlinear responses are necessary. This dissertation presents an experimental and modeling program used to test and characterize the axial and shear behaviors of seven different WPC products (primarily polyethylene and polypropylene) subjected to both quasi-static and creep loading at multiple temperatures. These data were used to develop a mechanics based model that can predict bending deflections of complex sections at any time or temperature. Additionally, a practical design method and standardized test procedures were created for use in typical long-term bending situations. A mechanical model for WPCs must combine time-dependent material characterization with a tool that can simulate mode dependence, temperature dependence, changing neutral axis location, and nonlinear axial stress distributions that vary over the length of a member and evolve with time. Finite-element (FE) modeling was chosen as the most practical way to satisfy these requirements. The model developed in this study uses an FE model with a custom-designed material model. Bending deflection predictions from the model were compared to experimental testing and the model showed some success despite the difficulties created by the material variability. The practical method created for designing WPC structural bending members utilizes four material constants

  7. Structure and thermophysical properties of aluminum-matrix composites

    NASA Astrophysics Data System (ADS)

    Pugacheva, N. B.; Michurov, N. S.; Senaeva, E. I.; Bykova, T. M.

    2016-11-01

    The microstructure and thermophysical properties of aluminum-matrix composites have been studied, in which a granulated Al-Zn-Mg-Cu alloy has been used as the matrix, and SiC particles taken in the amounts of 10, 20, and 30 vol % have bee used as the filler. It has been shown that, with an increase in the amount of the filler, the temperatures of the solidus and liquidus of the composites and the values of the thermal expansion coefficient and density increase, whereas the heat capacity, thermal conductivity, and thermal diffusivity decrease. The heat capacity of the composite depends on the amount of the filler: upon heating from 25 to 500°C, the heat capacity of the composite with 10 vol % SiC increases by only 16%, while that of the composite with 20 vol % SiC increases by 19%; and, at 39 vol % SiC, it increases by 36%.

  8. Structural characteristics of high temperature composites

    NASA Technical Reports Server (NTRS)

    Mandell, J. F.

    1985-01-01

    A progress report is presented for research carried from March 1984 through February 1985. A tensile test method has been developed which should give tensile and simulated shear (+ or - 45 deg) data for fiber composites up to 1000 C. Longitudinal and some transverse stress-strain data have been obtained for a glass matrix/Nicalon fiber system up to the matrix limiting temperature of 600 C. This demonstrates the functioning of the test method and the high temperature test facility which has been established on this grant. Transverse and longitudinal compression tests have been run, mostly in an end loaded configuration. A more satisfactory compression test is still required, and is under development.

  9. Composite S-layer lipid structures

    PubMed Central

    Schuster, Bernhard; Sleytr, Uwe B.

    2010-01-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state of the art survey how S-layer proteins, lipids, and polysaccharides may be used as basic building blocks for the assembly of S-layer supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas for application of composite S-layer membrane systems concern sensor systems involving specific membrane functions. PMID:19303933

  10. Complex refractive index of Martian dust - Wavelength dependence and composition

    NASA Technical Reports Server (NTRS)

    Pang, K.; Ajello, J. M.

    1977-01-01

    The size distribution and complex refractive index of Martian dust-cloud particles observed in 1971 with the Mariner 9 UV spectrometer are determined by matching the observed single-scattering albedo and phase function with Mie-scattering calculations for size distributions of spheres. Values of phase function times single-scattering albedo are presented for 12 wavelength intervals in the range from 190 to 350 nm, and best-fit values are obtained for the absorption index. It is found that the absorption index of the dust particles increases with decreasing wavelength from 350 to about 210 nm and then drops off shortward of 210 nm, with a structural shoulder occurring in the absorption spectrum between 240 and 250 nm. A search for a candidate material that can explain the strong UV absorption yields TiO2, whose anatase polymorph has an absorption spectrum matching that of the Martian dust. The TiO2 content of the dust particles is estimated to be a few percent or less.

  11. Cocured damped layers in composite structure

    SciTech Connect

    Rotz, C.A. ); Barrett, D.J. )

    1992-01-01

    A study was made on the feasibility of laminating and cocuring graphite fiber-epoxy prepreg with plies of commercially available damping materials for form beams and hat-stiffened panels. Experiments showed that cocuring did not adversely affect the damping materials and that excellent structural damping properties could be obtained. The construction of the hat-stiffened panels proved that complex parts containing damping materials could be fabricated. Dynamic testing of these components showed that internal architectural features could be designed to promote damping in primary structure.

  12. Probabilistic Evaluation of Advanced Ceramic Matrix Composite Structures

    NASA Technical Reports Server (NTRS)

    Abumeri, Galib H.; Chamis, Christos C.

    2003-01-01

    The objective of this report is to summarize the deterministic and probabilistic structural evaluation results of two structures made with advanced ceramic composites (CMC): internally pressurized tube and uniformly loaded flange. The deterministic structural evaluation includes stress, displacement, and buckling analyses. It is carried out using the finite element code MHOST, developed for the 3-D inelastic analysis of structures that are made with advanced materials. The probabilistic evaluation is performed using the integrated probabilistic assessment of composite structures computer code IPACS. The affects of uncertainties in primitive variables related to the material, fabrication process, and loadings on the material property and structural response behavior are quantified. The primitive variables considered are: thermo-mechanical properties of fiber and matrix, fiber and void volume ratios, use temperature, and pressure. The probabilistic structural analysis and probabilistic strength results are used by IPACS to perform reliability and risk evaluation of the two structures. The results will show that the sensitivity information obtained for the two composite structures from the computational simulation can be used to alter the design process to meet desired service requirements. In addition to detailed probabilistic analysis of the two structures, the following were performed specifically on the CMC tube: (1) predicted the failure load and the buckling load, (2) performed coupled non-deterministic multi-disciplinary structural analysis, and (3) demonstrated that probabilistic sensitivities can be used to select a reduced set of design variables for optimization.

  13. Composite Cocured Modular Eggcrate-Core Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Magurany, Charles J.

    1995-01-01

    Lightweight composite-material (e.g., graphite fiber/epoxy matrix) cocured sandwich panels with eggcratelike cores developed for use as principal components of optical benches and other structures that support precise optical instruments. Structures offer greater thermal and mechanical stability. Advantages include easier fabrication and better mechanical properties.

  14. Unibody Composite Pressurized Structure (UCPS) for In-Space Propulsion

    NASA Technical Reports Server (NTRS)

    Rufer, Markus

    2015-01-01

    Microcosm, Inc., in conjunction with the Scorpius Space Launch Company, is developing a UCPS (Unibody Composite Pressurized Structure )for in-space propulsion. This innovative approach constitutes a clean break from traditional spacecraft design by combining what were traditionally separate primary and secondary support structures and metal propellant tanks into a single unit.

  15. Water Permeability of Aquaporin-4 Channel Depends on Bilayer Composition, Thickness, and Elasticity

    PubMed Central

    Tong, Jihong; Briggs, Margaret M.; McIntosh, Thomas J.

    2012-01-01

    Aquaporin-4 (AQP4) is the primary water channel in the mammalian brain, particularly abundant in astrocytes, whose plasma membranes normally contain high concentrations of cholesterol. Here we test the hypothesis that the water permeabilities of two naturally occurring isoforms (AQP4-M1 and AQP4-M23) depend on bilayer mechanical/structural properties modulated by cholesterol and phospholipid composition. Osmotic stress measurements were performed with proteoliposomes containing AQP4 and three different lipid mixtures: 1), phosphatidylcholine (PC) and phosphatidylglycerol (PG); 2), PC, PG, with 40 mol % cholesterol; and 3), sphingomyelin (SM), PG, with 40 mol % cholesterol. The unit permeabilities of AQP4-M1 were 3.3 ± 0.4 × 10−13 cm3/s (mean ± SE), 1.2 ± 0.1 × 10−13 cm3/s, and 0.4 ± 0.1 × 10−13 cm3/s in PC:PG, PC:PG:cholesterol, and SM:PG:cholesterol, respectively. The unit permeabilities of AQP4-M23 were 2.1 ± 0.2 × 10−13 cm3/s, 0.8 ± 0.1 × 10−13 cm3/s, and 0.3 ± 0.1 × 10−13 cm3/s in PC:PG, PC:PG:cholesterol, and SM:PG:cholesterol, respectively. Thus, for each isoform the unit permeabilities strongly depended on bilayer composition and systematically decreased with increasing bilayer compressibility modulus and bilayer thickness. These observations suggest that altering lipid environment provides a means of regulating water channel permeability. Such permeability changes could have physiological consequences, because AQP4 water permeability would be reduced by its sequestration into SM:cholesterol-enriched raft microdomains. Conversely, under ischemic conditions astrocyte membrane cholesterol content decreases, which could increase AQP4 permeability. PMID:23199918

  16. Water permeability of aquaporin-4 channel depends on bilayer composition, thickness, and elasticity.

    PubMed

    Tong, Jihong; Briggs, Margaret M; McIntosh, Thomas J

    2012-11-07

    Aquaporin-4 (AQP4) is the primary water channel in the mammalian brain, particularly abundant in astrocytes, whose plasma membranes normally contain high concentrations of cholesterol. Here we test the hypothesis that the water permeabilities of two naturally occurring isoforms (AQP4-M1 and AQP4-M23) depend on bilayer mechanical/structural properties modulated by cholesterol and phospholipid composition. Osmotic stress measurements were performed with proteoliposomes containing AQP4 and three different lipid mixtures: 1), phosphatidylcholine (PC) and phosphatidylglycerol (PG); 2), PC, PG, with 40 mol % cholesterol; and 3), sphingomyelin (SM), PG, with 40 mol % cholesterol. The unit permeabilities of AQP4-M1 were 3.3 ± 0.4 × 10(-13) cm(3)/s (mean ± SE), 1.2 ± 0.1 × 10(-13) cm(3)/s, and 0.4 ± 0.1 × 10(-13) cm(3)/s in PC:PG, PC:PG:cholesterol, and SM:PG:cholesterol, respectively. The unit permeabilities of AQP4-M23 were 2.1 ± 0.2 × 10(-13) cm(3)/s, 0.8 ± 0.1 × 10(-13) cm(3)/s, and 0.3 ± 0.1 × 10(-13) cm(3)/s in PC:PG, PC:PG:cholesterol, and SM:PG:cholesterol, respectively. Thus, for each isoform the unit permeabilities strongly depended on bilayer composition and systematically decreased with increasing bilayer compressibility modulus and bilayer thickness. These observations suggest that altering lipid environment provides a means of regulating water channel permeability. Such permeability changes could have physiological consequences, because AQP4 water permeability would be reduced by its sequestration into SM:cholesterol-enriched raft microdomains. Conversely, under ischemic conditions astrocyte membrane cholesterol content decreases, which could increase AQP4 permeability.

  17. Ink composition for making a conductive silver structure

    DOEpatents

    Walker, Steven B.; Lewis, Jennifer A.

    2016-10-18

    An ink composition for making a conductive silver structure comprises a silver salt and a complex of (a) a complexing agent and a short chain carboxylic acid or (b) a complexing agent and a salt of a short chain carboxylic acid, according to one embodiment. A method for making a silver structure entails combining a silver salt and a complexing agent, and then adding a short chain carboxylic acid or a salt of the short chain carboxylic acid to the combined silver salt and a complexing agent to form an ink composition. A concentration of the complexing agent in the ink composition is reduced to form a concentrated formulation, and the silver salt is reduced to form a conductive silver structure, where the concentrated formulation and the conductive silver structure are formed at a temperature of about 120.degree. C. or less.

  18. Chemical composition in relation with biomass ash structure

    NASA Astrophysics Data System (ADS)

    Holubcik, Michal; Jandacka, Jozef

    2014-08-01

    Biomass combustion can be more complicated like combustion of fossil fuels because it is necessary to solve problems with lower ash melting temperature. It can cause a lot of problems during combustion process. Chemical composition of biomass ash has great impact on sinters and slags creation in ash because it affects structure of heated ash. In this paper was solved relation between chemical composition and structure of heated ash from three types of biomass (spruce wood, miscanthus giganteus and wheat straw). Amount of SiO2, CaO, MgO, Al2O3 and K2O was determined. Structure of heated ash was optically determined after heating to 1000 °C or 1200 °C. Results demonstrated that chemical composition has strong effect on structure and color of heated ash.

  19. Ptah-socar fuel-cooled composite materials structure

    NASA Astrophysics Data System (ADS)

    Bouchez, M.; Beyer, S.

    2009-09-01

    One of the key points for the development of dual-mode ramjets operating up to Mach 8 or more is the mastery of fuel-cooled composite materials structures, which are needed, at least, for the combustion chamber. MBDA France and EADS ST have been working on the development of a particular technology for such structures taking advantage of the background of MBDA France in the field of dual-mode ramjet and fuel-cooled structures and of ASTRIUM-EADS ST in the field of high-temperature composite materials. They have developed an innovative technology for advanced monobloc cooled C/C/SiC structures. The paper gives an updated status of the development of Paroi Tissée Application Hypersonique - Simple Operational Composite for Advanced Ramjet (PTAH-SOCAR) technology, including test results, and presents some results obtained during system and demonstrator studies.

  20. Progressive Failure Analysis Methodology for Laminated Composite Structures

    NASA Technical Reports Server (NTRS)

    Sleight, David W.

    1999-01-01

    A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C(exp 1) shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure. The different failure criteria and material degradation methods are compared and assessed by performing analyses of several laminated composite structures. Results from the progressive failure method indicate good correlation with the existing test data except in structural applications where interlaminar stresses are important which may cause failure mechanisms such as debonding or delaminations.

  1. Research of structure, mechanical and operation properties of glass-metal composites

    NASA Astrophysics Data System (ADS)

    Lyubimova, O. N.; Lyubimov, E. V.; Solonenko, E. P.; Morkovin, A. V.; Dryuk, S. A.

    2016-11-01

    The technological bases for the creation of the new structural material—glass-metal composite—are explored in this paper. Properties of the new material: structure and properties of the contact zone of glass and steel, tensile strength under static and dynamic loading, corrosion resistance and abrasion resistance under abrasive wear in the corrosive environment are theoretically and experimentally studied. The limit of thermal stability for experimental composite specimens equals 440°C. Corrosion tests show that the corrosion acceleration is the same for all composite specimens and does not depend on the solution concentration and the initial specimen weight. Steel specimens show significant changes in geometrical characteristics in comparison with composite specimens. Its prospect and ability to compete with steel is proved. The practical application is proposed for glass-metal composite rods.

  2. Optimization of composite structures by estimation of distribution algorithms

    NASA Astrophysics Data System (ADS)

    Grosset, Laurent

    The design of high performance composite laminates, such as those used in aerospace structures, leads to complex combinatorial optimization problems that cannot be addressed by conventional methods. These problems are typically solved by stochastic algorithms, such as evolutionary algorithms. This dissertation proposes a new evolutionary algorithm for composite laminate optimization, named Double-Distribution Optimization Algorithm (DDOA). DDOA belongs to the family of estimation of distributions algorithms (EDA) that build a statistical model of promising regions of the design space based on sets of good points, and use it to guide the search. A generic framework for introducing statistical variable dependencies by making use of the physics of the problem is proposed. The algorithm uses two distributions simultaneously: the marginal distributions of the design variables, complemented by the distribution of auxiliary variables. The combination of the two generates complex distributions at a low computational cost. The dissertation demonstrates the efficiency of DDOA for several laminate optimization problems where the design variables are the fiber angles and the auxiliary variables are the lamination parameters. The results show that its reliability in finding the optima is greater than that of a simple EDA and of a standard genetic algorithm, and that its advantage increases with the problem dimension. A continuous version of the algorithm is presented and applied to a constrained quadratic problem. Finally, a modification of the algorithm incorporating probabilistic and directional search mechanisms is proposed. The algorithm exhibits a faster convergence to the optimum and opens the way for a unified framework for stochastic and directional optimization.

  3. Crystalline structure and symmetry dependence of acoustic nonlinearity parameters

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.

    1994-01-01

    A quantitative measure of elastic wave nonlinearity in crystals is provided by the acoustic nonlinearity parameters. The nonlinearity parameters are defined for arbitrary propagation modes for solids of arbitrary crystalline symmetry and are determined along the pure mode propagation directions for 33 crystals of cubic symmetry from data reported in the literature. The magnitudes of the nonlinearity parameters are found to exhibit a strong dependence on the crystalline structure and symmetries associated with the modal direction in the solid. Calculations based on the Born-Mayer potential for crystals having a dominant repulsive contribution to the elastic constants from the interatomic pair potential suggest that the origin of the structure dependence is associated with the shape rather than the strength of the potential. Considerations based on variations in crystal symmetry during loading along pure mode propagation directions of face-centered-cubic solids provide a qualitative explanation for the dependence of the acoustic nonlinearity parameters on modal direction.

  4. Structure and Properties of High Symmetry Composites

    DTIC Science & Technology

    1990-07-27

    utilizing a 4-directional reinforcement. Reducing the close-to-cubic symmetry concept into practice in our laboratory by a three-dimensional braiding...modelled by utilizing the different elastic strain energy expressions produced by different combinations of symmetry elements. Symmetry in Materials The...rings is insignmicant. Utilizing the above assumptions, numerous textile structures possess holosymmetric cubic symmetry. This symmetry state is found in

  5. Metal matrix composite structural panel construction

    NASA Technical Reports Server (NTRS)

    Mcwithey, R. R.; Royster, D. M. (Inventor); Bales, T. T.

    1983-01-01

    Lightweight capped honeycomb stiffeners for use in fabricating metal or metal/matrix exterior structural panels on aerospace type vehicles and the process for fabricating same are disclosed. The stiffener stringers are formed in sheets, cut to the desired width and length and brazed in spaced relationship to a skin with the honeycomb material serving directly as the required lightweight stiffeners and not requiring separate metal encasement for the exposed honeycomb cells.

  6. Structural study of surfactant-dependent interaction with protein

    SciTech Connect

    Mehan, Sumit; Aswal, Vinod K.; Kohlbrecher, Joachim

    2015-06-24

    Small-angle neutron scattering (SANS) has been used to study the complex structure of anionic BSA protein with three different (cationic DTAB, anionic SDS and non-ionic C12E10) surfactants. These systems form very different surfactant-dependent complexes. We show that the structure of protein-surfactant complex is initiated by the site-specific electrostatic interaction between the components, followed by the hydrophobic interaction at high surfactant concentrations. It is also found that hydrophobic interaction is preferred over the electrostatic interaction in deciding the resultant structure of protein-surfactant complexes.

  7. An ideal reinforcement for structural composites

    SciTech Connect

    Kevorkijan, V.M.

    1997-12-01

    Different criteria and accumulated data lead to the conclusion that discontinuously reinforced metal-matrix composites (DR MMCs) will become an engineering material of general use. At the end of 1970s, the automobile and transport industries had a strong interest in and high expectations for DR-MMCs because of their superior specific strength and rigidity when compared with conventional aluminum alloys. After two decades of development, the first DR-MMC application, an engine connecting-rod, is ready to market. Major applications in the automobile industry, such as brake rotors and drive shafts, are now in the later stages of development, and other engineering applications are well advanced. DR-MMC technology is now recognized worldwide, and research groups are able to introduce remarkable applications of these materials to the market. Three main problems must be solved to facilitate the expanding application of DR-MMCs with light-metal-alloy matrices. They are: (1) superior cost performances; (2) active implementation of environmental concerns; (3) improved ductility. The immediate solution of these problems is impossible. However, many researchers and managers firmly believe that solutions will be found if the same amount of energy is devoted to solving these problems as has been expended during the past two decades of DR-MMCs R and D.

  8. An integrated computer procedure for sizing composite airframe structures

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, J.

    1979-01-01

    A computerized algorithm to generate cross-sectional dimensions and fiber orientations for composite airframe structures is described, and its application in a wing structural synthesis is established. The algorithm unifies computations of aeroelastic loads, stresses, and deflections, as well as optimal structural sizing and fiber orientations in an open-ended system of integrated computer programs. A finite-element analysis and a mathematical-optimization technique are discussed.

  9. Experience-dependent structural synaptic plasticity in the mammalian brain.

    PubMed

    Holtmaat, Anthony; Svoboda, Karel

    2009-09-01

    Synaptic plasticity in adult neural circuits may involve the strengthening or weakening of existing synapses as well as structural plasticity, including synapse formation and elimination. Indeed, long-term in vivo imaging studies are beginning to reveal the structural dynamics of neocortical neurons in the normal and injured adult brain. Although the overall cell-specific morphology of axons and dendrites, as well as of a subpopulation of small synaptic structures, are remarkably stable, there is increasing evidence that experience-dependent plasticity of specific circuits in the somatosensory and visual cortex involves cell type-specific structural plasticity: some boutons and dendritic spines appear and disappear, accompanied by synapse formation and elimination, respectively. This Review focuses on recent evidence for such structural forms of synaptic plasticity in the mammalian cortex and outlines open questions.

  10. Time-dependent reliability analysis and condition assessment of structures

    SciTech Connect

    Ellingwood, B.R.

    1997-01-01

    Structures generally play a passive role in assurance of safety in nuclear plant operation, but are important if the plant is to withstand the effect of extreme environmental or abnormal events. Relative to mechanical and electrical components, structural systems and components would be difficult and costly to replace. While the performance of steel or reinforced concrete structures in service generally has been very good, their strengths may deteriorate during an extended service life as a result of changes brought on by an aggressive environment, excessive loading, or accidental loading. Quantitative tools for condition assessment of aging structures can be developed using time-dependent structural reliability analysis methods. Such methods provide a framework for addressing the uncertainties attendant to aging in the decision process.

  11. Structural Arrangement Trade Study. Volume 1: Reusable Hydrogen Composite Tank System (RHCTS) and Graphite Composite Primary Structures (GCPS). Executive summary

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This volume is the first of a three volume set that discusses the structural arrangement trade study plan that will identify the most suitable configuration for an SSTO winged vehicle capable of delivering 25,000 lbs to a 220 nm circular orbit at 51.6 deg inclination. The Reusable Hydrogen Composite Tank System (RHCTS), and Graphite Composite Primary Structures most suitable for intertank, wing and thrust structures are identified. This executive summary presents the trade study process, the selection process, requirements used, analysis performed and data generated. Conclusions and recommendations are also presented.

  12. Development of knife- and bullet-impact-resistant composite structures

    NASA Astrophysics Data System (ADS)

    Levinsky, A. A.; Sapozhnikov, S. B.; Grass, T. S.

    2012-09-01

    Two types of layered composite structures — based on an aramid fabric covered with alumina microparticles and on polycarbonate — have been considered. Experimental investigation of the mechanical properties and puncture resistance of the first material was carried out. The results of quasi-static, dynamic, and firearm tests of the composite plates are presented. The minimum distance from a first puncture where the stubbing protection is safe was found by using the digital image correlation method. A FEM analysis of bending and tension of composite plates with a defect of complex geometry was performed. The analytical results obtained are compared with test data.

  13. Structural applications of Avimid K3B LDF thermoplastic composites

    NASA Astrophysics Data System (ADS)

    Perrella, Andrew P.

    Composite applications on advanced aircraft require lightweight, high performance, tough material systems which are capable of operating at high service temperatures. These composite systems must also be producible and cost effective. Avimid K3B composite materials and related process and part manufacturing technologies offers a unique solutions to these requirements. The objective of this paper is to describe selected Avimid K3B processing approaches such as Long Discontinuous Fiber thermoforming and fusion bonding. A review of the Avimid K3B F-16 Strake Door Joint Development Program is presented. This program successfully developed, built and structurally validated a flight demonstration component using these materials and manufacturing methods.

  14. Material and structural studies of metal and polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

    1973-01-01

    Fiber-reinforced composites and design analysis methods for these materials are being developed because of the vast potential of composites for decreasing weight and/or increasing use temperature capability in aerospace systems. These composites have potential for use in airbreathing engine components as well as aeronautical and space vehicle structures. Refractory wire-superalloy composites for use up to 2200 F or more and metal-matrix composites for lower temperature applications such as aerospace structures and turbojet fan and compressor blades are under investigation and are discussed. The development of a number of resin systems, including the polyimides and polyphenylquinoxalines, is described and their potential for use at temperatures approaching 315 C (600 F) is indicated. Various molecular modifications that improve processability and/or increase thermal and oxidative resistance of the resins are also described. Structural analysis methods are discussed for determining the stresses and deformations in complex composite systems. Consideration is also given to residual stresses resulting from the curing process and to the foreign object damage problem in fan blade applications.

  15. Computational modeling of structure of metal matrix composite in centrifugal casting process

    SciTech Connect

    Zagorski, Roman

    2007-04-07

    The structure of alumina matrix composite reinforced with crystalline particles obtained during centrifugal casting process are studied. Several parameters of cast process like pouring temperature, temperature, rotating speed and size of casting mould which influent on structure of composite are examined. Segregation of crystalline particles depended on other factors such as: the gradient of density of the liquid matrix and reinforcement, thermal processes connected with solidifying of the cast, processes leading to changes in physical and structural properties of liquid composite are also investigated. All simulation are carried out by CFD program Fluent. Numerical simulations are performed using the FLUENT two-phase free surface (air and matrix) unsteady flow model (volume of fluid model - VOF) and discrete phase model (DPM)

  16. Topologically ordered magnesium-biopolymer hybrid composite structures.

    PubMed

    Oosterbeek, Reece N; Seal, Christopher K; Staiger, Mark P; Hyland, Margaret M

    2015-01-01

    Magnesium and its alloys are intriguing as possible biodegradable biomaterials due to their unique combination of biodegradability and high specific mechanical properties. However, uncontrolled biodegradation of magnesium during implantation remains a major challenge in spite of the use of alloying and protective coatings. In this study, a hybrid composite structure of magnesium metal and a biopolymer was fabricated as an alternative approach to control the corrosion rate of magnesium. A multistep process that combines metal foam production and injection molding was developed to create a hybrid composite structure that is topologically ordered in all three dimensions. Preliminary investigations of the mechanical properties and corrosion behavior exhibited by the hybrid Mg-polymer composite structures suggest a new potential approach to the development of Mg-based biomedical devices.

  17. Instability and Wave Propagation in Structured 3D Composites

    NASA Astrophysics Data System (ADS)

    Kaynia, Narges; Fang, Nicholas X.; Boyce, Mary C.

    2014-03-01

    Many structured composites found in nature possess undulating and wrinkled interfacial layers that regulate mechanical, chemical, acoustic, adhesive, thermal, electrical and optical functions of the material. This research focused on the complex instability and wrinkling pattern arising in 3D structured composites and the effect of the buckling pattern on the overall structural response. The 3D structured composites consisted of stiffer plates supported by soft matrix on both sides. Compression beyond the critical strain led to complex buckling patterns in the initially straight plates. The motivation of our work is to elaborate the formation of a system of prescribed periodic scatterers (metamaterials) due to buckling, and their effect to interfere wave propagation through the metamaterial structures. Such metamaterials made from elastomers enable large reversible deformation and, as a result, significant changes of the wave propagation properties. We developed analytical and finite element models to capture various aspects of the instability mechanism. Mechanical experiments were designed to further explore the modeling results. The ability to actively alter the 3D composite structure can enable on-demand tunability of many different functions, such as active control of wave propagation to create band-gaps and waveguides.

  18. Use of lightweight composites for GAS payload structures

    NASA Technical Reports Server (NTRS)

    Spencer, Mark B.

    1987-01-01

    A key element in the design of a small self-contained payload is the supporting structure. This structure must support the experiments and other components while using as little space and weight as possible. Hence, the structure material must have characteristics of being both strong and light. Aluminum was used for the structure on the first Purdue University payload, but consumed a relatively large percentage of the total payload weight. The current payload has a larger power supply requirement than did the previous payload. To allow additional weight for the batteries, a composite material has been chosen for the structure which has the required strength while being considerably lighter than aluminum. A radial fin design has been chosen for ease of composite material lay-up and its overall strength of design. A composite plate will connect the free ends of the fins and add strength and reduce vibration. The physical characteristics of the composite material and the method of open lay-up construction is described. Also discussed are the testing, modifications, and problems encountered during assembly of the experiments to the structure.

  19. Probabilistic and structural reliability analysis of laminated composite structures based on the IPACS code

    NASA Technical Reports Server (NTRS)

    Sobel, Larry; Buttitta, Claudio; Suarez, James

    1993-01-01

    Probabilistic predictions based on the Integrated Probabilistic Assessment of Composite Structures (IPACS) code are presented for the material and structural response of unnotched and notched, 1M6/3501-6 Gr/Ep laminates. Comparisons of predicted and measured modulus and strength distributions are given for unnotched unidirectional, cross-ply, and quasi-isotropic laminates. The predicted modulus distributions were found to correlate well with the test results for all three unnotched laminates. Correlations of strength distributions for the unnotched laminates are judged good for the unidirectional laminate and fair for the cross-ply laminate, whereas the strength correlation for the quasi-isotropic laminate is deficient because IPACS did not yet have a progressive failure capability. The paper also presents probabilistic and structural reliability analysis predictions for the strain concentration factor (SCF) for an open-hole, quasi-isotropic laminate subjected to longitudinal tension. A special procedure was developed to adapt IPACS for the structural reliability analysis. The reliability results show the importance of identifying the most significant random variables upon which the SCF depends, and of having accurate scatter values for these variables.

  20. Temporal Dependency and the Structure of Early Looking

    PubMed Central

    Messinger, Daniel S.; Mattson, Whitney I.; Todd, James Torrence; Gangi, Devon N.; Myers, Nicholas D.; Bahrick, Lorraine E.

    2017-01-01

    Although looking time is used to assess infant perceptual and cognitive processing, little is known about the temporal structure of infant looking. To shed light on this temporal structure, 127 three-month-olds were assessed in an infant-controlled habituation procedure and presented with a pre-recorded display of a woman addressing the infant using infant-directed speech. Previous individual look durations positively predicted subsequent look durations over a six look window, suggesting a temporal dependency between successive infant looks. The previous look duration continued to predict the subsequent look duration after accounting for habituation-linked declines in look duration, and when looks were separated by an inter-trial interval in which no stimulus was displayed. Individual differences in temporal dependency, the strength of associations between consecutive look durations, are distinct from individual differences in mean infant look duration. Nevertheless, infants with stronger temporal dependency had briefer mean look durations, a potential index of stimulus processing. Temporal dependency was evident not only between individual infant looks but between the durations of successive habituation trials (total looking within a trial). Finally, temporal dependency was evident in associations between the last look at the habituation stimulus and the first look at a novel test stimulus. Thus temporal dependency was evident across multiple timescales (individual looks and trials comprised of multiple individual looks) and persisted across conditions including brief periods of no stimulus presentation and changes from a familiar to novel stimulus. Associations between consecutive look durations over multiple timescales and stimuli suggest a temporal structure of infant attention that has been largely ignored in previous work on infant looking. PMID:28076362

  1. Implementation of Fiber Substructuring Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.

    2001-01-01

    A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to impact loads. Previously, strain rate dependent inelastic constitutive equations developed to model the polymer matrix were incorporated into a mechanics of materials based micromechanics method. In the current work, the micromechanics method is revised such that the composite unit cell is divided into a number of slices. Micromechanics equations are then developed for each slice, with laminate theory applied to determine the elastic properties, effective stresses and effective inelastic strains for the unit cell. Verification studies are conducted using two representative polymer matrix composites with a nonlinear, strain rate dependent deformation response. The computed results compare well to experimentally obtained values.

  2. Self-assembled hierarchically structured organic-inorganic composite systems.

    PubMed

    Tritschler, Ulrich; Cölfen, Helmut

    2016-05-13

    Designing bio-inspired, multifunctional organic-inorganic composite materials is one of the most popular current research objectives. Due to the high complexity of biocomposite structures found in nacre and bone, for example, a one-pot scalable and versatile synthesis approach addressing structural key features of biominerals and affording bio-inspired, multifunctional organic-inorganic composites with advanced physical properties is highly challenging. This article reviews recent progress in synthesizing organic-inorganic composite materials via various self-assembly techniques and in this context highlights a recently developed bio-inspired synthesis concept for the fabrication of hierarchically structured, organic-inorganic composite materials. This one-step self-organization concept based on simultaneous liquid crystal formation of anisotropic inorganic nanoparticles and a functional liquid crystalline polymer turned out to be simple, fast, scalable and versatile, leading to various (multi-)functional composite materials, which exhibit hierarchical structuring over several length scales. Consequently, this synthesis approach is relevant for further progress and scientific breakthrough in the research field of bio-inspired and biomimetic materials.

  3. Advanced aerospace composite material structural design using artificial intelligent technology

    SciTech Connect

    Sun, S.H.; Chen, J.L.; Hwang, W.C.

    1993-12-31

    Due to the complexity in the prediction of property and behavior, composite material has not substituted for metal widely yet, though it has high specific-strength and high specific-modulus that are more important in the aerospace industry. In this paper two artificial intelligent techniques, the expert systems and neural network technology, were introduced to the structural design of composite material. Expert System which has good ability in symbolic processing can helps us to solve problem by saving experience and knowledge. It is, therefore, a reasonable way to combine expert system technology to tile composite structural design. The development of a prototype expert system to help designer during the process of composite structural design is presented. Neural network is a network similar to people`s brain that can simulate the thinking way of people and has the ability of learning from the training data by adapting the weights of network. Because of the bottleneck in knowledge acquisition processes, the application of neural network and its learning ability to strength design of composite structures are presented. Some examples are in this paper to demonstrate the idea.

  4. Soil type-depending effect of paddy management: composition and distribution of soil organic matter

    NASA Astrophysics Data System (ADS)

    Urbanski, Livia; Kölbl, Angelika; Lehndorff, Eva; Houtermans, Miriam; Schad, Peter; Zhang, Gang-Lin; Rahayu Utami, Sri; Kögel-Knabner, Ingrid

    2016-04-01

    Paddy soil management is assumed to promote soil organic matter accumulation and specifically lignin caused by the resistance of the aromatic lignin structure against biodegradation under anaerobic conditions during inundation of paddy fields. The present study investigates the effect of paddy soil management on soil organic matter composition compared to agricultural soils which are not used for rice production (non-paddy soils). A variety of major soil types, were chosen in Indonesia (Java), including Alisol, Andosol and Vertisol sites (humid tropical climate of Java, Indonesia) and in China Alisol sites (humid subtropical climate, Nanjing). This soils are typically used for rice cultivation and represent a large range of soil properties to be expected in Asian paddy fields. All topsoils were analysed for their soil organic matter composition by solid-state 13C nuclear magnetic resonance spectroscopy and lignin-derived phenols by CuO oxidation method. The soil organic matter composition, revealed by solid-state 13C nuclear magnetic resonance, was similar for the above named different parent soil types (non-paddy soils) and was also not affected by the specific paddy soil management. The contribution of lignin-related carbon groups to total SOM was similar in the investigated paddy and non-paddy soils. A significant proportion of the total aromatic carbon in some paddy and non-paddy soils was attributed to the application of charcoal as a common management practise. The extraction of lignin-derived phenols revealed low VSC (vanillyl, syringyl, cinnamyl) values for all investigated soils, being typical for agricultural soils. An inherent accumulation of lignin-derived phenols due to paddy management was not found. Lignin-derived phenols seem to be soil type-dependent, shown by different VSC concentrations between the parent soil types. The specific paddy management only affects the lignin-derived phenols in Andosol-derived paddy soils which are characterized by

  5. Synthesis, structure and antimicrobial property of green composites from cellulose, wool, hair and chicken feather.

    PubMed

    Tran, Chieu D; Prosencyes, Franja; Franko, Mladen; Benzi, Gerald

    2016-10-20

    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 Staphylococcus 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.

  6. High efficiency tantalum-based ceramic composite structures

    NASA Technical Reports Server (NTRS)

    Stewart, David A. (Inventor); Leiser, Daniel B. (Inventor); DiFiore, Robert R. (Inventor); Katvala, Victor W. (Inventor)

    2010-01-01

    Tantalum-based ceramics are suitable for use in thermal protection systems. These composite structures have high efficiency surfaces (low catalytic efficiency and high emittance), thereby reducing heat flux to a spacecraft during planetary re-entry. These ceramics contain tantalum disilicide, molybdenum disilicide and borosilicate glass. The components are milled, along with a processing aid, then applied to a surface of a porous substrate, such as a fibrous silica or carbon substrate. Following application, the coating is then sintered on the substrate. The composite structure is substantially impervious to hot gas penetration and capable of surviving high heat fluxes at temperatures approaching 3000.degree. F. and above.

  7. Development of Textile Reinforced Composites for Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Dexter, H. Benson

    1998-01-01

    NASA has been a leader in development of composite materials for aircraft applications during the past 25 years. In the early 1980's NASA and others conducted research to improve damage tolerance of composite structures through the use of toughened resins but these resins were not cost-effective. The aircraft industry wanted affordable, robust structures that could withstand the rigors of flight service with minimal damage. The cost and damage tolerance barriers of conventional laminated composites led NASA to focus on new concepts in composites which would incorporate the automated manufacturing methods of the textiles industry and which would incorporate through-the-thickness reinforcements. The NASA Advanced Composites Technology (ACT) Program provided the resources to extensively investigate the application of textile processes to next generation aircraft wing and fuselage structures. This paper discusses advanced textile material forms that have been developed, innovative machine concepts and key technology advancements required for future application of textile reinforced composites in commercial transport aircraft. Multiaxial warp knitting, triaxial braiding and through-the-thickness stitching are the three textile processes that have surfaced as the most promising for further development. Textile reinforced composite structural elements that have been developed in the NASA ACT Program are discussed. Included are braided fuselage frames and window-belt reinforcements, woven/stitched lower fuselage side panels, stitched multiaxial warp knit wing skins, and braided wing stiffeners. In addition, low-cost processing concepts such as resin transfer molding (RTM), resin film infusion (RFI), and vacuum-assisted resin transfer molding (VARTM) are discussed. Process modeling concepts to predict resin flow and cure in textile preforms are also discussed.

  8. Stacking dependent electronic structures of transition metal dichalcogenides heterobilayer

    NASA Astrophysics Data System (ADS)

    Lee, Yea-Lee; Park, Cheol-Hwan; Ihm, Jisoon

    The systematic study of the electronic structures and optical properties of the transition metal dichalcogenides (TMD) heterobilayers can significantly improve the designing of new electronic and optoelectronic devices. Here, we theoretically study the electronic structures and optical properties of TMD heterobilayers using the first-principles methods. The band structures of TMD heterobilayer are shown to be determined by the band alignments of the each layer, the weak interlayer interactions, and angle dependent stacking patterns. The photoluminescence spectra are investigated using the calculated band structures, and the optical absorption spectra are examined by the GW approximations including the electron-hole interaction through the solution of the Bethe-Salpeter equation. It is expected that the weak interlayer interaction gives rise to the substantial interlayer optical transition which will be corresponding to the interlayer exciton.

  9. Structure dependent hydrogen induced etching features of graphene crystals

    NASA Astrophysics Data System (ADS)

    Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap; Papon, Remi; Sharma, Subash; Vishwakarma, Riteshkumar; Sharma, Kamal P.; Tanemura, Masaki

    2015-06-01

    H2 induced etching of graphene is of significant interest to understand graphene growth process as well as to fabricate nanoribbons and various other structures. Here, we demonstrate the structure dependent H2 induced etching behavior of graphene crystals. We synthesized graphene crystals on electro-polished Cu foil by an atmospheric pressure chemical vapor deposition process, where some of the crystals showed hexagonal shaped snowflake-dendritic morphology. Significant differences in H2 induced etching behavior were observed for the snowflake-dendritic and regular graphene crystals by annealing in a gas mixture of H2 and Ar. The regular graphene crystals were etched anisotropically creating hexagonal holes with pronounced edges, while etching of all the dendritic crystals occurred from the branches of lobs creating symmetrical fractal structures. The etching behavior provides important clue of graphene nucleation and growth as well as their selective etching to fabricate well-defined structures for nanoelectronics.

  10. Jovian deep magnetotail composition and structure

    NASA Astrophysics Data System (ADS)

    McComas, D. J.; Allegrini, F.; Bagenal, F.; Ebert, R. W.; Elliott, H. A.; Nicolaou, G.; Szalay, J. R.; Valek, P.; Weidner, S.

    2017-02-01

    We analyze plasma ion observations from the Solar Wind Around Pluto instrument on New Horizons as it traveled back through the dusk flank of the Jovian magnetotail from 600 to more than 2500 Jovian radii behind the planet. We find that at all distances, light ions (mostly protons) dominate the heavy ions (S++ and O+) that are far more abundant in the near Jupiter plasma disk and that were expected to be the primary ions filling the Jovian magnetotail. This key new observation might indicate that heavy ions are confined closer to the equator than the spacecraft trajectory or a substantial addition of light ions via reconnection and/or mixing along the magnetopause boundary. However, because we find no evidence for acceleration of the tail plasma with distance, a more likely explanation seems to be that the heavy ions are preferentially released down the dawn flank of the magnetotail. Perhaps, this occurs as a part of the process where flux tubes, after expanding as they rotate across the near-tail region, need to pull back inward in order to fit within the dawnside of the magnetopause. A second major finding of this study is that there are two dominant periods of the plasma structures in the Jovian magnetotail: 3.53 (0.18 full width at half maximum (FWHM)) and 5.35 (0.38 FWHM) days. Remarkably, the first of these is identical within the errors to Europa's orbital period (3.55 days). Both of these results should provide important new fodder for Jovian magnetospheric theories and lead to a better understanding of Jupiter's magnetosphere.

  11. Composite Structure Modeling and Analysis of Advanced Aircraft Fuselage Concepts

    NASA Technical Reports Server (NTRS)

    Mukhopadhyay, Vivek; Sorokach, Michael R.

    2015-01-01

    NASA Environmentally Responsible Aviation (ERA) project and the Boeing Company are collabrating to advance the unitized damage arresting composite airframe technology with application to the Hybrid-Wing-Body (HWB) aircraft. The testing of a HWB fuselage section with Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) construction is presently being conducted at NASA Langley. Based on lessons learned from previous HWB structural design studies, improved finite-element models (FEM) of the HWB multi-bay and bulkhead assembly are developed to evaluate the performance of the PRSEUS construction. In order to assess the comparative weight reduction benefits of the PRSEUS technology, conventional cylindrical skin-stringer-frame models of a cylindrical and a double-bubble section fuselage concepts are developed. Stress analysis with design cabin-pressure load and scenario based case studies are conducted for design improvement in each case. Alternate analysis with stitched composite hat-stringers and C-frames are also presented, in addition to the foam-core sandwich frame and pultruded rod-stringer construction. The FEM structural stress, strain and weights are computed and compared for relative weight/strength benefit assessment. The structural analysis and specific weight comparison of these stitched composite advanced aircraft fuselage concepts demonstrated that the pressurized HWB fuselage section assembly can be structurally as efficient as the conventional cylindrical fuselage section with composite stringer-frame and PRSEUS construction, and significantly better than the conventional aluminum construction and the double-bubble section concept.

  12. Weak morphology dependent valence band structure of boron nitride

    NASA Astrophysics Data System (ADS)

    Zhi, Chunyi; Ueda, Shigenori; Zeng, Haibo; Wang, Xuebin; Tian, Wei; Wang, Xi; Bando, Yoshio; Golberg, Dmitri

    2013-08-01

    We report a hard X-ray photoelectron spectroscopy (HX-PES) investigation on valence band structure of Boron Nitrides (BN) having different morphologies, including nanosheets, nanotubes, and micro-sized particles. Very weak morphology/valence band structure dependence was observed. For each case, the B-N π-band overlapping with σ-band between 0 to -12.5 eV and the s-band below -15 eV were identified. No obvious morphology-induced band shifts and intensity variations were observed. First-principles calculations based on density functional theory were performed and the results were compared with the experimental data. This theoretical analysis well explains the weak morphology dependent valence band spectra of BN nanomaterials obtained during HX-PES measurements.

  13. Measuring spin-dependent structure functions at CEBAF

    SciTech Connect

    Schaefer, A.

    1994-04-01

    The author analyses whether CEBAF with a 10 GeV beam could contribute significantly to the understanding of spin-dependent deep-inelastic scattering as well as semi-inclusive reactions. The main advantage of CEBAF is the much better attainable statistics, its great disadvantage its comparably low energy, which limits the accessible x-range to about 0.15 to 0.7. Within these constraints CEBAF could provide (1) high precision data which would be very valuable to understand the Q{sup 2} dependence of the spin-dependent structure functions g{sub 1}(x) and G{sub 2}(x) and (2) the by far most precise determination of the third moments of g{sub 1}(x) and g{sub 2}(x) the latter of which the author argues to be related to a fundamental property of the nucleon.

  14. Precision measurement of the neutron spin dependent structure functions

    SciTech Connect

    Kolomensky, Y.G.

    1997-02-01

    In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function g{sub 1}{sup n} (x, Q{sup 2}) of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized {sup 3}He target. The high beam energy allowed the author to extend the kinematic coverage compared to the previous SLAC experiments to 0.014 {le} x {le} 0.7 with an average Q{sup 2} of 5 GeV{sup 2}. The author reports the integral of the spin dependent structure function in the measured range to be {integral}{sub 0.014}{sup 0.7} dx g{sub 1}{sup n}(x, 5 GeV{sup 2}) = {minus}0.036 {+-} 0.004(stat.) {+-} 0.005(syst.). The author observes relatively large values of g{sub 1}{sup n} at low x that call into question the reliability of data extrapolation to x {r_arrow} 0. Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. The author performs a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions g{sub 1}{sup p} and g{sub 1}{sup n} paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, the author evolves the data to Q{sup 2} = 5 GeV{sup 2}, determines the first moments of the polarized structure functions of the proton and neutron, and finds agreement with the Bjorken sum rule.

  15. Thermo-compression of pyrope-grossular garnet solid solutions: non-linear compositional dependence

    NASA Astrophysics Data System (ADS)

    Clark, S. M.; Du, W.; Walker, D.

    2014-12-01

    Unit cell parameters of a series of synthetic garnets with the pyrope, grossular, and four intermediate compositions were measured up to about 900K and to 10 GPa using synchrotron X-ray powder diffraction. Coefficients of thermal expansion of pyrope-grossular garnets are in the range 2.10~ 2.74 x 10-5 K-1 and uniformly increase with temperature. Values for the two end members pyrope and grossular are identical within experimental error 2.74±0.05 x 10-5 K-1 and 2.73±0.01 x 10-5 K-1 respectively. Coefficients of thermal expansion for intermediate compositions are smaller than those of end members, and are not linearly dependent on composition. Bulk modulus of grossular is Κ0=164.3(1) GPa (with Κ0' the pressure derivative of the bulk modulus fixed to 5.92) and bulk modulus of pyrope is Κ0=169.2(2) GPa (with Κ0' fixed to 4.4) using a third order Birch-Murnaghan equation of state, which are consistent with previously reported values. The bulk moduli of garnets of intermediate composition are between ~155 and ~160 GPa, smaller than those of the end-members no matter which Κ0' is chosen. The compositional dependence of bulk modulus resembles the compositional dependence of thermal expansion. Intermediate garnets on this binary have large positive excess volume, which makes them more compressible. We find that excess volumes in the pyrope-grossular series remain relatively large even at high pressure (~6GPa) and temperature (~800K), supporting the observation of crystal exsolution on this garnet join. (Ref: Wei Du, Simon Martin Clark, and David Walker (2014) Thermo-compression of pyrope-grossular garnet solid solutions:non-linear compositional dependence. American Mineralogist, In Press).

  16. Low-Cost Composite Materials and Structures for Aircraft Applications

    NASA Technical Reports Server (NTRS)

    Deo, Ravi B.; Starnes, James H., Jr.; Holzwarth, Richard C.

    2003-01-01

    A survey of current applications of composite materials and structures in military, transport and General Aviation aircraft is presented to assess the maturity of composites technology, and the payoffs realized. The results of the survey show that performance requirements and the potential to reduce life cycle costs for military aircraft and direct operating costs for transport aircraft are the main reasons for the selection of composite materials for current aircraft applications. Initial acquisition costs of composite airframe components are affected by high material costs and complex certification tests which appear to discourage the widespread use of composite materials for aircraft applications. Material suppliers have performed very well to date in developing resin matrix and fiber systems for improved mechanical, durability and damage tolerance performance. The next challenge for material suppliers is to reduce material costs and to develop materials that are suitable for simplified and inexpensive manufacturing processes. The focus of airframe manufacturers should be on the development of structural designs that reduce assembly costs by the use of large-scale integration of airframe components with unitized structures and manufacturing processes that minimize excessive manual labor.

  17. Sensitivity and optimization of composite structures using MSC/NASTRAN

    NASA Technical Reports Server (NTRS)

    Nagendra, Gopal K.; Fleury, Claude

    1987-01-01

    Design sensitivity analysis for composites will soon be available in MSC/NASTRAN. The design variables for composites can be lamina thicknesses, orientation angles, material properties or a combination of all three. With the increasing use of composites in aerospace and automotive industries, this general capability can be used in its own right for carrying out sensitivity analysis of complicated real-life structures. As part of a research effort, the sensitivity analysis was coupled with a general purpose optimizer. This preliminary version of the optimizer is capable of dealing with minimum weight structural design with a rather general design variable linking capability at the element level or system level. Only sizing type of design variables (i.e., lamina thicknesses) can be handled by the optimizer. Test cases were run and validated by comparison with independent finite element packages. The linking of design sensitivity capability for composites in MSC/NASTRAN with an optimizer would give designers a powerful automated tool to carry out practical opitmization design of real-life complicated composite structures.

  18. Size-dependent structure of silver nanoparticles under high pressure

    SciTech Connect

    Koski, Kristie Jo

    2008-12-31

    Silver noble metal nanoparticles that are<10 nm often possess multiply twinned grains allowing them to adopt shapes and atomic structures not observed in bulk materials. The properties exhibited by particles with multiply twinned polycrystalline structures are often far different from those of single-crystalline particles and from the bulk. I will present experimental evidence that silver nanoparticles<10 nm undergo a reversible structural transformation under hydrostatic pressures up to 10 GPa. Results for nanoparticles in the intermediate size range of 5 to 10 nm suggest a reversible linear pressure-dependent rhombohedral distortion which has not been previously observed in bulk silver. I propose a mechanism for this transitiion that considers the bond-length distribution in idealized multiply twinned icosahedral particles. Results for nanoparticles of 3.9 nm suggest a reversible linear pressure-dependent orthorhombic distortion. This distortion is interpreted in the context of idealized decahedral particles. In addition, given these size-dependent measurements of silver nanoparticle compression with pressure, we have constructed a pressure calibration curve. Encapsulating these silver nanoparticles in hollow metal oxide nanospheres then allows us to measure the pressure inside a nanoshell using x-ray diffraction. We demonstrate the measurement of pressure gradients across nanoshells and show that these nanoshells have maximum resolved shear strengths on the order of 500 MPa to IGPa.

  19. Crystal structures of phosphoketolase: thiamine diphosphate-dependent dehydration mechanism.

    PubMed

    Suzuki, Ryuichiro; Katayama, Takane; Kim, Byung-Jun; Wakagi, Takayoshi; Shoun, Hirofumi; Ashida, Hisashi; Yamamoto, Kenji; Fushinobu, Shinya

    2010-10-29

    Thiamine diphosphate (ThDP)-dependent enzymes are ubiquitously present in all organisms and catalyze essential reactions in various metabolic pathways. ThDP-dependent phosphoketolase plays key roles in the central metabolism of heterofermentative bacteria and in the pentose catabolism of various microbes. In particular, bifidobacteria, representatives of beneficial commensal bacteria, have an effective glycolytic pathway called bifid shunt in which 2.5 mol of ATP are produced per glucose. Phosphoketolase catalyzes two steps in the bifid shunt because of its dual-substrate specificity; they are phosphorolytic cleavage of fructose 6-phosphate or xylulose 5-phosphate to produce aldose phosphate, acetyl phosphate, and H(2)O. The phosphoketolase reaction is different from other well studied ThDP-dependent enzymes because it involves a dehydration step. Although phosphoketolase was discovered more than 50 years ago, its three-dimensional structure remains unclear. In this study we report the crystal structures of xylulose 5-phosphate/fructose 6-phosphate phosphoketolase from Bifidobacterium breve. The structures of the two intermediates before and after dehydration (α,β-dihydroxyethyl ThDP and 2-acetyl-ThDP) and complex with inorganic phosphate give an insight into the mechanism of each step of the enzymatic reaction.

  20. Evolution of tertiary structure of viral RNA dependent polymerases.

    PubMed

    Černý, Jiří; Černá Bolfíková, Barbora; Valdés, James J; Grubhoffer, Libor; Růžek, Daniel

    2014-01-01

    Viral RNA dependent polymerases (vRdPs) are present in all RNA viruses; unfortunately, their sequence similarity is too low for phylogenetic studies. Nevertheless, vRdP protein structures are remarkably conserved. In this study, we used the structural similarity of vRdPs to reconstruct their evolutionary history. The major strength of this work is in unifying sequence and structural data into a single quantitative phylogenetic analysis, using powerful a Bayesian approach. The resulting phylogram of vRdPs demonstrates that RNA-dependent DNA polymerases (RdDPs) of viruses within Retroviridae family cluster in a clearly separated group of vRdPs, while RNA-dependent RNA polymerases (RdRPs) of dsRNA and +ssRNA viruses are mixed together. This evidence supports the hypothesis that RdRPs replicating +ssRNA viruses evolved multiple times from RdRPs replicating +dsRNA viruses, and vice versa. Moreover, our phylogram may be presented as a scheme for RNA virus evolution. The results are in concordance with the actual concept of RNA virus evolution. Finally, the methods used in our work provide a new direction for studying ancient virus evolution.

  1. Application of the self-diagnosis composite into concrete structure

    NASA Astrophysics Data System (ADS)

    Matsubara, Hideaki; Shin, Soon-Gi; Okuhara, Yoshiki; Nomura, Hiroshi; Yanagida, Hiroaki

    2001-04-01

    The function and performance of the self-diagnosis composites embedded in mortar/concrete blocks and concrete piles were investigated by bending tests and electrical resistance measurements. Carbon powder (CP) and carbon fiber (CF) were introduced in glass fiber reinforced plastics composites to obtain electrical conductivity. The CP composite has commonly good performances in various bending tests of block and pile specimens, comparing to the CF composite. The electrical resistance of the CP composite increases in a small strain to response remarkably micro-crack formation at about 200 (mu) strain and to detect well to smaller deformations before the crack formation. The CP composite possesses a continuous resistance change up to a large strain level near the final fracture of concrete structures reinforced by steel bars. The cyclic bending tests showed that the micro crack closed at unloading state was able to be evaluated from the measurement of residual resistance. It has been concluded that the self- diagnosis composite is fairly useful for the measurement of damage and fracture in concrete blocks and piles.

  2. Studies on structural properties of clay magnesium ferrite nano composite

    NASA Astrophysics Data System (ADS)

    Kaur, Manpreet; Singh, Mandeep; Jeet, Kiran; Kaur, Rajdeep

    2015-08-01

    Magnesium ferrite-bentonite clay composite was prepared by sol-gel combustion method employing citric acid as complexing agent and fuel. The effect of clay on the structural properties was studied with X-ray diffraction (XRD), Fourier transform infrared (FT-IR) Spectroscopy, Scanning electron microscopy (SEM), SEM- Energy dispersive Spectroscope (EDS) and BET surface area analyzer. Decrease in particle size and density was observed on addition of bentonite clay. The BET surface area of nano composite containing just 5 percent clay was 74.86 m2/g. Whereas porosity increased from 40.5 per cent for the pure magnesium ferrite to 81.0 percent in the composite showing that nano-composite has potential application as an adsorbent.

  3. Structural Analysis of Novel Lignin-derived Carbon Composite Anodes

    SciTech Connect

    McNutt, Nicholas W; Rios, Orlando; Feygenson, Mikhail; Proffen, Thomas E; Keffer, David J

    2014-01-01

    The development of novel lignin-based carbon composite anodes consisting of nanocrystalline and amorphous domains motivates the understanding of a relationship of the structural properties characterizing these materials, such as crystallite size, intracrystallite dspacing, crystalline volume fraction and composite density, with their pair distribution functions (PDF), obtained from both molecular dynamics simulation and neutron scattering. A model for these composite materials is developed as a function of experimentally measurable parameters and realized in fifteen composite systems, three of which directly match all parameters of their experimental counterparts. The accurate reproduction of the experimental PDFs using the model systems validates the model. The decomposition of the simulated PDFs provides an understanding of each feature in the PDF and allows for the development of a mapping between the defining characteristics of the PDF and the material properties of interest.

  4. Studies on structural properties of clay magnesium ferrite nano composite

    SciTech Connect

    Kaur, Manpreet Singh, Mandeep; Jeet, Kiran Kaur, Rajdeep

    2015-08-28

    Magnesium ferrite-bentonite clay composite was prepared by sol-gel combustion method employing citric acid as complexing agent and fuel. The effect of clay on the structural properties was studied with X-ray diffraction (XRD), Fourier transform infrared (FT-IR) Spectroscopy, Scanning electron microscopy (SEM), SEM- Energy dispersive Spectroscope (EDS) and BET surface area analyzer. Decrease in particle size and density was observed on addition of bentonite clay. The BET surface area of nano composite containing just 5 percent clay was 74.86 m{sup 2}/g. Whereas porosity increased from 40.5 per cent for the pure magnesium ferrite to 81.0 percent in the composite showing that nano-composite has potential application as an adsorbent.

  5. Design optimization of composite structures operating in acoustic environments

    NASA Astrophysics Data System (ADS)

    Chronopoulos, D.

    2015-10-01

    The optimal mechanical and geometric characteristics for layered composite structures subject to vibroacoustic excitations are derived. A Finite Element description coupled to Periodic Structure Theory is employed for the considered layered panel. Structures of arbitrary anisotropy as well as geometric complexity can thus be modelled by the presented approach. Damping can also be incorporated in the calculations. Initially, a numerical continuum-discrete approach for computing the sensitivity of the acoustic wave characteristics propagating within the modelled periodic composite structure is exhibited. The first- and second-order sensitivities of the acoustic transmission coefficient expressed within a Statistical Energy Analysis context are subsequently derived as a function of the computed acoustic wave characteristics. Having formulated the gradient vector as well as the Hessian matrix, the optimal mechanical and geometric characteristics satisfying the considered mass, stiffness and vibroacoustic performance criteria are sought by employing Newton's optimization method.

  6. Effect of processing on Polymer/Composite structure and properties

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Advances in the vitality and economic health of the field of polymer forecasting are discussed. A consistent and rational point of view which considers processing as a participant in the underlying triad of relationships which comprise materials science and engineering is outlined. This triad includes processing as it influences material structure, and ultimately properties. Methods in processing structure properties, polymer science and engineering, polymer chemistry and synthesis, structure and modification and optimization through processing, and methods of melt flow modeling in processing structure property relations of polymer were developed. Mechanical properties of composites are considered, and biomedical materials research to include polymer processing effects are studied. An analysis of the design technology of advances graphite/epoxy composites is also reported.

  7. Dependence of dielectric properties on the crystallinity of ceramic/polymer composites.

    PubMed

    Kim, Eung Soo; Jeon, Chang Jun

    2011-09-01

    Effects of ZnNb(2)O(6) content and crystallinity of polymers on the dielectric properties of ZnNb(2)O(6)/polytetrafluoroethylene (PTFE), polypropylene (PP), and polystyrene (PS) composites were investigated at microwave frequencies. With increasing ZnNb(2)O(6) content, the dielectric constant (K) of the composites increased, whereas the dielectric loss (tanδ) and temperature coefficient of resonant frequency (TCF) decreased. The tanδ of the composites with amorphous PS was lower than those of the composites with semi-crystalline PP and PTFE. For the composites with semi-crystalline PTFE and PP, the tanδ was strongly dependent on the degree of crystallinity of composites. Several types of theoretical models were applied to predict the effective dielectric properties of the composites. Typically, K of 5.73, tan δ of 1.45 x 10(-3), and TCF of 2.66 ppm/°C were obtained for the PP composites with 0.5 volume fraction V(f) of ZnNb(2)O(6).

  8. Multi-scale modelling of strongly heterogeneous 3D composite structures using spatial Voronoi tessellation

    NASA Astrophysics Data System (ADS)

    El Said, Bassam; Ivanov, Dmitry; Long, Andrew C.; Hallett, Stephen R.

    2016-03-01

    3D composite materials are characterized by complex internal yarn architectures, leading to complex deformation and failure development mechanisms. Net-shaped preforms, which are originally periodic in nature, lose their periodicity when the fabric is draped, deformed on a tool, and consolidated to create geometrically complex composite components. As a result, the internal yarn architecture, which dominates the mechanical behaviour, becomes dependent on the structural geometry. Hence, predicting the mechanical behaviour of 3D composites requires an accurate representation of the yarn architecture within structural scale models. When applied to 3D composites, conventional finite element modelling techniques are limited to either homogenised properties at the structural scale, or the unit cell scale for a more detailed material property definition. Consequently, these models fail to capture the complex phenomena occurring across multiple length scales and their effects on a 3D composite's mechanical response. Here a multi-scale modelling approach based on a 3D spatial Voronoi tessellation is proposed. The model creates an intermediate length scale suitable for homogenisation to deal with the non-periodic nature of the final material. Information is passed between the different length scales to allow for the effect of the structural geometry to be taken into account on the smaller scales. The stiffness and surface strain predictions from the proposed model have been found to be in good agreement with experimental results. The proposed modelling framework has been used to gain important insight into the behaviour of this category of materials. It has been observed that the strain and stress distributions are strongly dependent on the internal yarn architecture and consequently on the final component geometry. Even for simple coupon tests, the internal architecture and geometric effects dominate the mechanical response. Consequently, the behaviour of 3D woven

  9. Development of a Subcell Based Modeling Approach for Modeling the Architecturally Dependent Impact Response of Triaxially Braided Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Sorini, Chris; Chattopadhyay, Aditi; Goldberg, Robert K.; Kohlman, Lee W.

    2016-01-01

    Understanding the high velocity impact response of polymer matrix composites with complex architectures is critical to many aerospace applications, including engine fan blade containment systems where the structure must be able to completely contain fan blades in the event of a blade-out. Despite the benefits offered by these materials, the complex nature of textile composites presents a significant challenge for the prediction of deformation and damage under both quasi-static and impact loading conditions. The relatively large mesoscale repeating unit cell (in comparison to the size of structural components) causes the material to behave like a structure rather than a homogeneous material. Impact experiments conducted at NASA Glenn Research Center have shown the damage patterns to be a function of the underlying material architecture. Traditional computational techniques that involve modeling these materials using smeared homogeneous, orthotropic material properties at the macroscale result in simulated damage patterns that are a function of the structural geometry, but not the material architecture. In order to preserve heterogeneity at the highest length scale in a robust yet computationally efficient manner, and capture the architecturally dependent damage patterns, a previously-developed subcell modeling approach where the braided composite unit cell is approximated as a series of four adjacent laminated composites is utilized. This work discusses the implementation of the subcell methodology into the commercial transient dynamic finite element code LS-DYNA (Livermore Software Technology Corp.). Verification and validation studies are also presented, including simulation of the tensile response of straight-sided and notched quasi-static coupons composed of a T700/PR520 triaxially braided [0deg/60deg/-60deg] composite. Based on the results of the verification and validation studies, advantages and limitations of the methodology as well as plans for future work

  10. A critical review of nanotechnologies for composite aerospace structures

    NASA Astrophysics Data System (ADS)

    Kostopoulos, Vassilis; Masouras, Athanasios; Baltopoulos, Athanasios; Vavouliotis, Antonios; Sotiriadis, George; Pambaguian, Laurent

    2017-03-01

    The past decade extensive efforts have been invested in understanding the nano-scale and revealing the capabilities offered by nanotechnology products to structural materials. Integration of nano-particles into fiber composites concludes to multi-scale reinforced composites and has opened a new wide range of multi-functional materials in industry. In this direction, a variety of carbon based nano-fillers has been proposed and employed, individually or in combination in hybrid forms, to approach the desired performance. Nevertheless, a major issue faced lately more seriously due to the interest of industry is on how to incorporate these nano-species into the final composite structure through existing manufacturing processes and infrastructure. This interest originates from several industrial applications needs that request the development of new multi-functional materials which combine enhanced mechanical, electrical and thermal properties. In this work, an attempt is performed to review the most representative processes and related performances reported in literature and the experience obtained on nano-enabling technologies of fiber composite materials. This review focuses on the two main composite manufacturing technologies used by the aerospace industry; Prepreg/Autoclave and Resin Transfer technologies. It addresses several approaches for nano-enabling of composites for these two routes and reports latest achieved results focusing on performance of nano-enabled fiber reinforced composites extracted from literature. Finally, this review work identifies the gap between available nano-technology integration routes and the established industrial composite manufacturing techniques and the challenges to increase the Technology Readiness Level to reach the demands for aerospace industry applications.

  11. A critical review of nanotechnologies for composite aerospace structures

    NASA Astrophysics Data System (ADS)

    Kostopoulos, Vassilis; Masouras, Athanasios; Baltopoulos, Athanasios; Vavouliotis, Antonios; Sotiriadis, George; Pambaguian, Laurent

    2016-07-01

    The past decade extensive efforts have been invested in understanding the nano-scale and revealing the capabilities offered by nanotechnology products to structural materials. Integration of nano-particles into fiber composites concludes to multi-scale reinforced composites and has opened a new wide range of multi-functional materials in industry. In this direction, a variety of carbon based nano-fillers has been proposed and employed, individually or in combination in hybrid forms, to approach the desired performance. Nevertheless, a major issue faced lately more seriously due to the interest of industry is on how to incorporate these nano-species into the final composite structure through existing manufacturing processes and infrastructure. This interest originates from several industrial applications needs that request the development of new multi-functional materials which combine enhanced mechanical, electrical and thermal properties. In this work, an attempt is performed to review the most representative processes and related performances reported in literature and the experience obtained on nano-enabling technologies of fiber composite materials. This review focuses on the two main composite manufacturing technologies used by the aerospace industry; Prepreg/Autoclave and Resin Transfer technologies. It addresses several approaches for nano-enabling of composites for these two routes and reports latest achieved results focusing on performance of nano-enabled fiber reinforced composites extracted from literature. Finally, this review work identifies the gap between available nano-technology integration routes and the established industrial composite manufacturing techniques and the challenges to increase the Technology Readiness Level to reach the demands for aerospace industry applications.

  12. Composite Structures and Materials Research at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Starnes, James H., Jr.; Dexter, H. Benson; Johnston, Norman J.; Ambur, Damodar R.; Cano, Roberto J.

    2001-01-01

    A summary of recent composite structures and materials research at NASA Langley Research Center is presented. Fabrication research to develop low-cost automated robotic fabrication procedures for thermosetting and thermoplastic composite materials, and low-cost liquid molding processes for preformed textile materials is described. Robotic fabrication procedures discussed include ply-by-ply, cure-on-the-fly heated placement head and out-of-autoclave electron-beam cure methods for tow and tape thermosetting and thermoplastic materials. Liquid molding fabrication processes described include Resin Film Infusion (RFI) Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). Results for a full-scale composite wing box are summarized to identify the performance of materials and structures fabricated with these low-cost fabrication methods.

  13. Composite Structures and Materials Research at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Starnes, James H., Jr.; Dexter, H. Benson; Johnston, Norman J.; Ambur, Damodar R.; Cano, roberto J.

    2003-01-01

    A summary of recent composite structures and materials research at NASA Langley Research Center is presented. Fabrication research to develop low-cost automated robotic fabrication procedures for thermosetting and thermoplastic composite materials, and low-cost liquid molding processes for preformed textile materials is described. Robotic fabrication procedures discussed include ply-by-ply, cure-on-the-fly heated placement head and out-of-autoclave electron-beam cure methods for tow and tape thermosetting and thermoplastic materials. Liquid molding fabrication processes described include Resin Film Infusion (RFI), Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). Results for a full-scale composite wing box are summarized to identify the performance of materials and structures fabricated with these low-cost fabrication methods.

  14. Nondestructive Evaluation (NDE) for Inspection of Composite Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Parker, F. Raymond

    2014-01-01

    Composite honeycomb structures are widely used in aerospace applications due to their low weight and high strength advantages. Developing nondestructive evaluation (NDE) inspection methods are essential for their safe performance. Flash thermography is a commonly used technique for composite honeycomb structure inspections due to its large area and rapid inspection capability. Flash thermography is shown to be sensitive for detection of face sheet impact damage and face sheet to core disbond. Data processing techniques, using principal component analysis to improve the defect contrast, are discussed. Limitations to the thermal detection of the core are investigated. In addition to flash thermography, X-ray computed tomography is used. The aluminum honeycomb core provides excellent X-ray contrast compared to the composite face sheet. The X-ray CT technique was used to detect impact damage, core crushing, and skin to core disbonds. Additionally, the X-ray CT technique is used to validate the thermography results.

  15. Better Finite-Element Analysis of Composite Shell Structures

    NASA Technical Reports Server (NTRS)

    Clarke, Gregory

    2007-01-01

    A computer program implements a finite-element-based method of predicting the deformations of thin aerospace structures made of isotropic materials or anisotropic fiber-reinforced composite materials. The technique and corresponding software are applicable to thin shell structures in general and are particularly useful for analysis of thin beamlike members having open cross-sections (e.g. I-beams and C-channels) in which significant warping can occur.

  16. Rapid detection and quantification of impact damage in composite structures

    NASA Technical Reports Server (NTRS)

    Smith, Barry T.

    1992-01-01

    It is shown that a multidisciplinary nondestructive evaluation approach for impact damage detection in composite structures can be used to produce a more efficient inspection. The multidisciplinary NDE approach relies on fast large area thermographic inspections along with detailed ultrasonic volumetric imaging. The thermal inspection technique rapidly identifies the impact damage. The ultrasonic volumetric imaging quantifies the impact generated delaminations through the volume of the structure.

  17. Rapid detection and quantification of impact damage in composite structures

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Farley, Gary; Smith, Barry T.

    1991-01-01

    NDE results from thermographic and volumetric ultrasonic techniques are presented to illustrate the multidisciplinary NDE approach to impact-damage detection in such composite structures as are increasingly prevalent in helicopters. Attention is given to both flat-panel and 'y-stiffened' panel specimens; these were fabricated either with kevlar or carbon fiber through-the-thickness reinforcements. While thermal inspection identifies impact damage, volumetric imaging quantifies the impact-generated delaminations through the volume of the structure.

  18. Resin transfer molding for advanced composite primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Markus, Alan; Palmer, Ray

    1991-01-01

    Resin Transfer Molding (RTM) has been identified by Douglas Aircraft Company (DAC) and industry to be one of the promising processes being developed today which can break the cost barrier of implementing composite primary structures into a commercial aircraft production environment. The RTM process developments and scale-up plans Douglas Aircrart will be conducting under the NASA ACT contract are discussed.

  19. ALL NATURAL COMPOSITE SANDWICH BEAMS FOR STRUCTURAL APPLICATIONS. (R829576)

    EPA Science Inventory

    As part of developing an all natural composite roof for housing application,
    structural panels and unit beams were manufactured out of soybean oil based resin
    and natural fibers (flax, cellulose, pulp, recycled paper, chicken feathers)
    using vacuum assisted resin tran...

  20. Design of a robust SHM system for composite structures

    NASA Astrophysics Data System (ADS)

    Beard, Shawn; Liu, Ching-Chao; Chang, Fu-Kuo

    2007-04-01

    Composites are becoming increasingly popular materials used in a wide range of applications on large-scale structures such as windmill blades, rocket motor cases, and aircraft fuselage and wings. For these large structures, using composites greatly enhances the operation and performance of the application, but also introduces extraordinary inspection challenges that push the limits of traditional NDE in terms of time and cost. Recent advances in Structural Health Monitoring (SHM) technologies offer a promising solution to these inspection challenges. But efficient design methodologies and implementation procedures are needed to ensure the reliability and robustness of SHM technologies for use in real-world applications. This paper introduces the essential elements of the design and implementation process by way of example. State-of-the-art techniques to optimize sensor placement, perform self-diagnostics, compensate for environmental conditions, and generate probability of detection (POD) curves for any application are discussed. The techniques are presented in relation to Acellent's recently developed SmartComposite System that is used to monitor the integrity of large composite structures. The system builds on the active sensor network technology of Acellent that is analogous to a built-in acousto-ultrasonic NDE system. Key features of the system include new miniaturized lightweight hardware, self-diagnostics and adaptive algorithm to automatically compensate for damaged sensors, reliable damage detection under different environmental conditions, and generation of POD curves. This paper will provide an overview of the system and demonstrate its key features.

  1. Composition, structure, physicochemical properties, and modifications of cassava starch.

    PubMed

    Zhu, Fan

    2015-05-20

    Cassava is highly tolerant to harsh climatic conditions and has great productivity on marginal lands. The supply of cassava starch, the major component of the root, is thus sustainable and cheap. This review summarizes the current knowledge of the composition, physical and chemical structures, physicochemical properties, nutritional quality, and modifications of cassava starch. Research opportunities to better understand this starch are provided.

  2. Materials research at Stanford University. [composite materials, crystal structure, acoustics

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Research activity related to the science of materials is described. The following areas are included: elastic and thermal properties of composite materials, acoustic waves and devices, amorphous materials, crystal structure, synthesis of metal-metal bonds, interactions of solids with solutions, electrochemistry, fatigue damage, superconductivity and molecular physics and phase transition kinetics.

  3. Application of Pi Preform Composite Joints in Fabrication of NASA Composite Crew Module Demonstration Structure

    NASA Technical Reports Server (NTRS)

    Higgins, John E.; Pelham, Larry

    2008-01-01

    This paper will describe unique and extensive use of pre-woven and impregnated pi cross-sections in fabrication of a carbon composite demonstration structure for the Composite Crew Module (CCM) Program. The program is managed by the NASA Safety and Engineering Center with participants from ten NASA Centers and AFRL. Multiple aerospace contractors are participating in the design development, tooling and fabrication effort as well. The goal of the program is to develop an agency wide design team for composite habitable spacecraft. The specific goals for this development project are: a) To gain hands on experience in design, building and testing a composite crew module. b) To validate key assumptions by resolving composite spacecraft design details through fabrication and testing of hardware. This paper will focus on the design and fabrication issues supporting selection of the Lockheed Martin patented Pi pre-form to provide sound composite joints a numerous locations in the structure. This abstract is based on Preliminary Design data. The final design will continue to evolve through the fall of 2007 with fabrication mostly completed by conference date.

  4. Negatively strain-dependent electrical resistance of magnetically arranged nickel composites: application to highly stretchable electrodes and stretchable lighting devices.

    PubMed

    Kim, Sangwoo; Byun, Junghwan; Choi, Seongdae; Kim, Donghyun; Kim, Taehoon; Chung, Seungjun; Hong, Yongtaek

    2014-05-21

    A novel property of the negatively strain-dependent electrical resistance change of nickel conductive composites is presented. The composite shows negatively strain-dependent resistance change when magnetically arranged, while most conductive materials show opposite behavior. This negative dependency is utilized to produce highly stretchable electrodes and to demonstrate a new conceptual resolution-sustainable stretchable lighting/display device.

  5. Virtual Testing of Large Composite Structures: A Multiple Length/Time-Scale Framework

    NASA Astrophysics Data System (ADS)

    Gigliotti, Luigi; Pinho, Silvestre T.

    2015-12-01

    This paper illustrates a multiple length/time-scale framework for the virtual testing of large composite structures. Such framework hinges upon a Mesh Superposition Technique (MST) for the coupling between areas of the structure modelled at different length-scales and upon an efficient solid-to-shell numerical homogenization which exploits the internal symmetries of Unit Cells (UCs). Using this framework, it is possible to minimize the areas of the structure modelled at the lowest- (and computationally demanding) scales and the computational cost required to calculate the homogenised to be used in the higher-scales subdomains of multiscale FE models, as well as to simulate the mechanical response of different parts of the structure using different solvers, depending on where they are expected to provide the most computationally efficient solution. The relevance and key-aspects of the multiple length/time-scale framework are demonstrated through the analysis of a real-sized aeronautical composite component.

  6. Significance tests for functional data with complex dependence structure

    PubMed Central

    Lahiri, Soumen N.; Carroll, Raymond J.

    2015-01-01

    We propose an L2-norm based global testing procedure for the null hypothesis that multiple group mean functions are equal, for functional data with complex dependence structure. Specifically, we consider the setting of functional data with a multilevel structure of the form groups–clusters or subjects–units, where the unit-level profiles are spatially correlated within the cluster, and the cluster-level data are independent. Orthogonal series expansions are used to approximate the group mean functions and the test statistic is estimated using the basis coefficients. The asymptotic null distribution of the test statistic is developed, under mild regularity conditions. To our knowledge this is the first work that studies hypothesis testing, when data have such complex multilevel functional and spatial structure. Two small-sample alternatives, including a novel block bootstrap for functional data, are proposed, and their performance is examined in simulation studies. The paper concludes with an illustration of a motivating experiment. PMID:26023253

  7. Task-dependency and structure-dependency in number interference effects in sentence comprehension

    PubMed Central

    Franck, Julie; Colonna, Saveria; Rizzi, Luigi

    2015-01-01

    We report three experiments on French that explore number mismatch effects in intervention configurations in the comprehension of object A’-dependencies, relative clauses and questions. The study capitalizes on the finding of object attraction in sentence production, in which speakers sometimes erroneously produce a verb that agrees in number with a plural object in object relative clauses. Evidence points to the role of three critical constructs from formal syntax: intervention, intermediate traces and c-command (Franck et al., 2010). Experiment 1, using a self-paced reading procedure on these grammatical structures with an agreement error on the verb, shows an enhancing effect of number mismatch in intervention configurations, with faster reading times with plural (mismatching) objects. Experiment 2, using an on-line grammaticality judgment task on the ungrammatical versions of these structures, shows an interference effect in the form of attraction, with slower response times with plural objects. Experiment 3 with a similar grammaticality judgment task shows stronger attraction from c-commanding than from preceding interveners. Overall, the data suggest that syntactic computations in performance refer to the same syntactic representations in production and comprehension, but that different tasks tap into different processes involved in parsing: whereas performance in self-paced reading reflects the intervention of the subject in the process of building an object A’-dependency, performance in grammaticality judgment reflects intervention of the object on the computation of the subject-verb agreement dependency. The latter shows the hallmarks of structure-dependent attraction effects in sentence production, in particular, a sensitivity to specific characteristics of hierarchical representations. PMID:25914652

  8. Task-dependency and structure-dependency in number interference effects in sentence comprehension.

    PubMed

    Franck, Julie; Colonna, Saveria; Rizzi, Luigi

    2015-01-01

    We report three experiments on French that explore number mismatch effects in intervention configurations in the comprehension of object A'-dependencies, relative clauses and questions. The study capitalizes on the finding of object attraction in sentence production, in which speakers sometimes erroneously produce a verb that agrees in number with a plural object in object relative clauses. Evidence points to the role of three critical constructs from formal syntax: intervention, intermediate traces and c-command (Franck et al., 2010). Experiment 1, using a self-paced reading procedure on these grammatical structures with an agreement error on the verb, shows an enhancing effect of number mismatch in intervention configurations, with faster reading times with plural (mismatching) objects. Experiment 2, using an on-line grammaticality judgment task on the ungrammatical versions of these structures, shows an interference effect in the form of attraction, with slower response times with plural objects. Experiment 3 with a similar grammaticality judgment task shows stronger attraction from c-commanding than from preceding interveners. Overall, the data suggest that syntactic computations in performance refer to the same syntactic representations in production and comprehension, but that different tasks tap into different processes involved in parsing: whereas performance in self-paced reading reflects the intervention of the subject in the process of building an object A'-dependency, performance in grammaticality judgment reflects intervention of the object on the computation of the subject-verb agreement dependency. The latter shows the hallmarks of structure-dependent attraction effects in sentence production, in particular, a sensitivity to specific characteristics of hierarchical representations.

  9. Optical Characterization of Temperature- and Composition-Dependent Microstructure in Asphalt Binders

    NASA Astrophysics Data System (ADS)

    Ramm, Adam; Nazmus, Sakib; Bhasin, Amit; Downer, Michael

    We introduce noncontact optical microscopy and optical scattering to characterize asphalt binder microstructure at temperatures ranging from 15 to 85°C for two compositionally different asphalt binders. We benchmark optical measurements against rheometric measurements of the magnitude of the temperature-dependent bulk complex shear modulus | G* (T) | . The main findings are: (1) Elongated (5 x 1 μm), striped microstructures (known from AFM studies as ''bees'' because they resemble bumble-bees) are resolved optically, found to reside primarily at the surface, and do not reappear immediately after a single heating-cooling cycle. (2) Smaller (1 μm2) microstructures with no observable internal structure (hereafter dubbed ``ants''), are found to reside primarily in the bulk, to persist after multiple thermal cycles and to scatter light strongly. Optical scattering from ''ants'' decreases to zero with heating from 15 to 65°C, but recovers completely upon cooling back to 15°C, albeit with distinct hysteresis. (3) Rheometric measurements of | G* (T) | reveal hysteresis that closely resembles that observed by optical scatter, suggesting that thermally-driven changes in microstructure volume fraction cause corresponding changes in | G* (T) | .

  10. Composition dependence of Si{sub 1-x}Ge{sub x} sputter yield

    SciTech Connect

    Tuboltsev, V.; Jalkanen, P.; Kolodyazhnaya, M.; Raeisaenen, J.

    2005-11-15

    Sputtering yields have been measured for unstrained Si{sub 1-x}Ge{sub x} (x=0-1) alloys when bombarded with Ar{sup +} ions within the linear cascade regime. Nonlinear S-shape dependence of the sputter yield as a function of the alloy composition has been revealed. The dependence is analyzed within the frameworks of the cascade theory conventionally accepted to be the most systematic to date theoretical approach in sputtering. In view of a linear composition dependence predicted for the sputter yield by the cascade theory adapted for polyatomic substrates, the nonlinearity observed in our experiments is shown to be related to the alloying effect on the surface binding energies of the alloy components. Based on this analysis, an interpretation is proposed for the experimentally observed nonlinear composition dependence of Si{sub 1-x}Ge{sub x} sputter yield. The yield is expressed by an equation derived from the cascade theory with additional terms of the composition parameter x. The form of the equation implies that for a polyatomic substrate the surface binding energy of an individual atom is determined not only by its own chemical identity but to a considerable degree by the identities of its neighbors.

  11. Composition, structure and properties of sediment thermal springs of Kamchatka

    NASA Astrophysics Data System (ADS)

    Shanina, Violetta; Smolyakov, Pavel; Parfenov, Oleg

    2016-04-01

    The paper deals with the physical and mechanical properties sediment thermal fields Mutnovsky, Lower Koshelevo and Bannyh (Kamchatka). This multi-component soils, mineral and chemical composition of which depends on the formation factors (pH, temperature, salinity of water, composition and structure of the host volcanic rocks). Samples Lower Koshelevo sediment thermal sources differ in the following composition: smectite, kaolinite, kaolinite-smectite mixed-mineral. Samples of sediment thermal springs Mutnovsky volcano in accordance with the X-ray analysis has the following composition: volcanic glass, crystalline sulfur, plagioclase, smectite, illite-smectite mixed, illite, chlorite, quartz, cristobalite, pyrite, melanterite, kaolinite. Natural moisture content samples of sediment thermal springs from 45 to 121%, hygroscopic moisture content of 1.3 to 3.7%. A large amount of native sulfur (up to 92%) and the presence of amorphous material gives low values of density of solid particles (up to 2.1 g/cm3) samples Mutnovskii thermal field. The values of the density of solids sediment Koshelevo and Bannyh hot springs close to those of the main components of mineral densities (up to 2.6-3.0 g/cm3). The results of the particle size distribution and microaggregate analysis of sediment thermal springs Lower Koshelevo field shows that the predominance observed of particles with a diameter from 0.05 mm to 0.25 mm, the coefficient of soil heterogeneity heterogeneous. In the bottom sediments of the thermal springs of the volcano Mutnovsky poorly traced predominance of one faction. Most prevalent fraction with particle size 0.01 - 0.05 mm. When analyzing the content in the soil microaggregates their content is shifted towards particles with a diameter of 0.25 mm. The contents of a large number of large (1-10 mm), porous rock fragments, due to the deposition of pyroclastic material from the eruptions of the last century. Present in large amounts rounded crystals of native sulfur

  12. Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

    NASA Astrophysics Data System (ADS)

    Dey, Vikram

    The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and

  13. Damage monitoring of aircraft structures made of composite materials using wavelet transforms

    NASA Astrophysics Data System (ADS)

    Molchanov, D.; Safin, A.; Luhyna, N.

    2016-10-01

    The present article is dedicated to the study of the acoustic properties of composite materials and the application of non-destructive testing methods to aircraft components. A mathematical model of a wavelet transformed signal is presented. The main acoustic (vibration) properties of different composite material structures were researched. Multiple vibration parameter dependencies on the noise reduction factor were derived. The main steps of a research procedure and new method algorithm are presented. The data obtained was compared with the data from a three dimensional laser-Doppler scanning vibrometer, to validate the results. The new technique was tested in the laboratory and on civil aircraft at a training airfield.

  14. Rate dependent response and failure of a ductile epoxy and carbon fiber reinforced epoxy composite

    SciTech Connect

    Brown, Eric N; Rae, Philip J; Dattelbaum, Dana M; Stahl, David B

    2010-01-01

    An extensive characterization suite has been performed on the response and failure of a ductile epoxy 55A and uniaxial carbon fiber reinforced epoxy composite of IM7 fibers in 55A resin from the quasistatic to shock regime. The quasistatic and intermediate strain rate response, including elastic modulus, yield and failure have are characterized by quasistatic, SHPB, and DMA measurements as a function of fiber orientation and temperature. The high strain rate shock effect of fiber orientation in the composite and response of the pure resin are presented for plate impact experiments. It has previously been shown that at lower impact velocities the shock velocity is strongly dependent on fiber orientation but at higher impact velocity the in-plane and through thickness Hugoniots converge. The current results are compared with previous studies of the shock response of carbon fiber composites with more conventional brittle epoxy matrices. The spall response of the composite is measured and compared with quasistatic fracture toughness measurements.

  15. Temperature-dependent Goos-Hänchen shift on the interface of metal/dielectric composites.

    PubMed

    Zhao, Bin; Gao, Lei

    2009-11-23

    The temperature-dependent Goos-Hänchen shift (GHS) for an electromagnetic wave reflected from a metal/dielectric composite material is investigated. With the stationary-phase method, we theoretically show that the effect of the temperature on GHS is significant near the Brewster angle for the dielectric composites and at the grazing angle for the metallic composites. For dielectric composites, the lateral shift can be negative as well as positive. And GHS may become much negative, much positive, and nonmonotonic variation with increasing the temperature under different conditions. Moreover, through the suitable adjustment of the temperature, one may realize the reversal of the GHS. To support the above results, numerical simulations for Gaussian incident beams based on the momentum method and COMSOL Multiphysics software are provided, and reasonable agreement between the theoretical results and numerical simulations is found.

  16. A Study of Flexible Composites for Expandable Space Structures

    NASA Technical Reports Server (NTRS)

    Scotti, Stephen J.

    2016-01-01

    Payload volume for launch vehicles is a critical constraint that impacts spacecraft design. Deployment mechanisms, such as those used for solar arrays and antennas, are approaches that have successfully accommodated this constraint, however, providing pressurized volumes that can be packaged compactly at launch and expanded in space is still a challenge. One approach that has been under development for many years is to utilize softgoods - woven fabric for straps, cloth, and with appropriate coatings, bladders - to provide this expandable pressure vessel capability. The mechanics of woven structure is complicated by a response that is nonlinear and often nonrepeatable due to the discrete nature of the woven fiber architecture. This complexity reduces engineering confidence to reliably design and certify these structures, which increases costs due to increased requirements for system testing. The present study explores flexible composite materials systems as an alternative to the heritage softgoods approach. Materials were obtained from vendors who utilize flexible composites for non-aerospace products to determine some initial physical and mechanical properties of the materials. Uniaxial mechanical testing was performed to obtain the stress-strain response of the flexible composites and the failure behavior. A failure criterion was developed from the data, and a space habitat application was used to provide an estimate of the relative performance of flexible composites compared to the heritage softgoods approach. Initial results are promising with a 25% mass savings estimated for the flexible composite solution.

  17. An Efficient Analysis Methodology for Fluted-Core Composite Structures

    NASA Technical Reports Server (NTRS)

    Oremont, Leonard; Schultz, Marc R.

    2012-01-01

    The primary loading condition in launch-vehicle barrel sections is axial compression, and it is therefore important to understand the compression behavior of any structures, structural concepts, and materials considered in launch-vehicle designs. This understanding will necessarily come from a combination of test and analysis. However, certain potentially beneficial structures and structural concepts do not lend themselves to commonly used simplified analysis methods, and therefore innovative analysis methodologies must be developed if these structures and structural concepts are to be considered. This paper discusses such an analysis technique for the fluted-core sandwich composite structural concept. The presented technique is based on commercially available finite-element codes, and uses shell elements to capture behavior that would normally require solid elements to capture the detailed mechanical response of the structure. The shell thicknesses and offsets using this analysis technique are parameterized, and the parameters are adjusted through a heuristic procedure until this model matches the mechanical behavior of a more detailed shell-and-solid model. Additionally, the detailed shell-and-solid model can be strategically placed in a larger, global shell-only model to capture important local behavior. Comparisons between shell-only models, experiments, and more detailed shell-and-solid models show excellent agreement. The discussed analysis methodology, though only discussed in the context of fluted-core composites, is widely applicable to other concepts.

  18. The Dependance of Damage Accumulation in Carbon Fibre Reinforced Epoxy Composites on Matrix Properties.

    DTIC Science & Technology

    1985-12-01

    Diguuibutiofl Unlimited 0- Contract U.S. AIR FORCE/ARMINES- Centre des Matdriaux No A.F.O.S.R. 84-0397 - Final Report December 1985 THE DEPENDANCE OF DAMAGE...61102F 2301 D1 185 11 TITLE (include Security Classification) THE DEPENDANCE OF DAMAGE ACCUMULATION IN CARBON FIBRE REINFORCED EPOXY COMPOSITES ON...ATN OF: LTS/Autovon 235-4299 26 March 1986 SUBJECT: EOARD-TR-86-04, Final Scientific Report, "The Dependance of Damage Accumu- lation in Carbon Fibre

  19. Linear and non-linear electrical dependency of carbon nanotube reinforced composites to internal damage

    NASA Astrophysics Data System (ADS)

    Bekas, D.; Grammatikos, S. A.; Kouimtzi, C.; Paipetis, A. S.

    2015-02-01

    Carbon nanotube (CNT) enhanced composite materials have attracted the interest of many scientists worldwide, especially in the aerospace industry. Fundamental to their qualification as materials in primary aircraft structures is the investigation of the relationship between their functional characteristics and their long-term behaviour under external combined loads. Conductive reinforcement at the nanoscale is by definition multifunctional as it may (i) enhance structural performance and (ii) provide structural health monitoring functionalities. It is now well established that reversible changes in the electrical resistance in nano composites are related to strain and irreversible monotonic changes are related to cumulative damage in the nano composite. In this study, the effect of damage in the hysteretic electrical behaviour of nano-enhanced reinforced composites was investigated. The nanocomposites were subjected to different levels of damage and their response to a cyclic electrical potential excitation was monitored as a function of frequency. Along with the dynamic electrical investigation, an Electrical Potential Mapping (EPM) technique was developed to pin-point artificial damage in CNT-enhanced matrix composite materials. The electrical potential field of the bulk material has shown to be characteristic of its internal structural state. The results of EPM technique were contradicted and validated with conventional C-scans.

  20. Mesoscopic structure of neuronal tracts from time-dependent diffusion.

    PubMed

    Burcaw, Lauren M; Fieremans, Els; Novikov, Dmitry S

    2015-07-01

    Interpreting brain diffusion MRI measurements in terms of neuronal structure at a micrometer level is an exciting unresolved problem. Here we consider diffusion transverse to a bundle of fibers, and show theoretically, as well as using Monte Carlo simulations and measurements in a phantom made of parallel fibers mimicking axons, that the time dependent diffusion coefficient approaches its macroscopic limit slowly, in a (ln t)/t fashion. The logarithmic singularity arises due to short range disorder in the fiber packing. We identify short range disorder in axonal fibers based on histological data from the splenium, and argue that the time dependent contribution to the overall diffusion coefficient from the extra-axonal water dominates that of the intra-axonal water. This dominance may explain the bias in measuring axon diameters in clinical settings. The short range disorder is also reflected in the asymptotically linear frequency dependence of the diffusion coefficient measured with oscillating gradients, in agreement with recent experiments. Our results relate the measured diffusion to the mesoscopic structure of neuronal tissue, uncovering the sensitivity of diffusion metrics to axonal arrangement within a fiber tract, and providing an alternative interpretation of axonal diameter mapping techniques.

  1. Health Monitoring of Composite Material Structures using a Vibrometry Technique

    NASA Technical Reports Server (NTRS)

    Schulz, Mark J.

    1997-01-01

    Large composite material structures such as aircraft and Reusable Launch Vehicles (RLVS) operate in severe environments comprised of vehicle dynamic loads, aerodynamic loads, engine vibration, foreign object impact, lightning strikes, corrosion, and moisture absorption. These structures are susceptible to damage such as delamination, fiber breaking/pullout, matrix cracking, and hygrothermal strain. To ensure human safety and load-bearing integrity, these structures must be inspected to detect and locate often invisible damage and faults before becoming catastrophic. Moreover, nearly all future structures will need some type of in-service inspection technique to increase their useful life and reduce maintenance and overall costs. Possible techniques for monitoring the health and indicating damage on composite structures include: c-scan, thermography, acoustic emissions using piezoceramic actuators or fiber-optic wires with gratings, laser ultrasound, shearography, holography, x-ray, and others. These techniques have limitations in detecting damage that is beneath the surface of the structure, far away from a sensor location, or during operation of the vehicle. The objective of this project is to develop a more global method for damage detection that is based on structural dynamics principles, and can inspect for damage when the structure is subjected to vibratory loads to expose faults that may not be evident by static inspection. A Transmittance Function Monitoring (TFM) method is being developed in this project for ground-based inspection and operational health monitoring of large composite structures as a RLV. A comparison of the features of existing health monitoring approaches and the proposed TFM method is given.

  2. Hybrid Composites for LH2 Fuel Tank Structure

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Cano, Roberto J.; Johnston, Norman J.; Loos, Alfred C.; McMahon, William M.

    2001-01-01

    The application of lightweight carbon fiber reinforced plastics (CFRP) as structure for cryogenic fuel tanks is critical to the success of the next generation of Reusable Launch Vehicles (RLV). The recent failure of the X-33 composite fuel tank occurred in part due to microcracking of the polymer matrix, which allowed cryogen to permeate through the inner skin to the honeycomb core. As part of an approach to solve these problems, NASA Langley Research Center (LaRC) and Marshall Space Flight Center (MSFC) are working to develop and investigate polymer films that will act as a barrier to the permeation of LH2 through the composite laminate. In this study two commercially available films and eleven novel LaRC films were tested in an existing cryogenics laboratory at MSFC to determine the permeance of argon at room temperature. Several of these films were introduced as a layer in the composite to form an interleaved, or hybrid, composite to determine the effects on permeability. In addition, the effects of the interleaved layer thickness, number, and location on the mechanical properties of the composite laminate were investigated. In this initial screening process, several of the films were found to exhibit lower permeability to argon than the composite panels tested.

  3. Composites for Cryotank Structures. Present and Future: MSFC Perspective

    NASA Technical Reports Server (NTRS)

    Vaughn, Timothy P.

    1999-01-01

    The development of reusable launch vehicle systems for a single stage to orbit vehicle requires vehicles at liftoff with 85% to 94% of its mass consisting exclusively of propellants. These dry mass requirements drive designs to utilize stronger, lighter weight materials for structures. This technology development focus has allowed the introduction of composite materials in lieu of conventional metallic materials due to their higher specific strengths. Composite materials were successfully used for the liquid hydrogen tanks for the DC-XA, and a multi-lobed liquid hydrogen tank will be employed for the X-33. Another potential non-traditional application for composite materials is for liquid oxygen tanks, which is still being investigated. Traditionally, organic materials have been avoided wherever possible, due the potential fire hazard and the fact that composites fail conventional oxygen compatibility requirements. However, the potential weight savings warrant the investigation of the use of polymeric composite materials in oxygen environments. Since composites fail the conventional, time-proven test methods because they are considered flammable by test, we have embarked on an innovative approach to oxygen compatibility testing and evaluation focused on the use environments and attempts to eliminate or "design away" all potential ignition sources. Oxygen compatibility is defined as the ability of a material to coexist with oxygen and potential ignition sources with an acceptable, manageable degree of risk.

  4. Local structure, composition, and crystallization mechanism of a model two-phase “composite nanoglass”

    SciTech Connect

    Chattopadhyay, Soma; Kelly, S. D.; Shibata, Tomohiro; Balasubramanian, M.; Srinivasan, S. G.; Du, Jincheng; Banerjee, Rajarshi; Ayyub, Pushan

    2016-02-14

    We report a detailed study of the local composition and structure of a model, bi-phasic nanoglass with nominal stoichiometry Cu55Nb45. Three dimensional atom probe data suggest a nanoscale-phase-separated glassy structure having well defined Cu-rich and Nb-rich regions with a characteristic length scale of ≈3 nm. However, extended x-ray absorption fine structure analysis indicates subtle differences in the local environments of Cu and Nb. While the Cu atoms displayed a strong tendency to cluster and negligible structural order beyond the first coordination shell, the Nb atoms had a larger fraction of unlike neighbors (higher chemical order) and a distinctly better-ordered structural environment (higher topological order). This provides the first experimental indication that metallic glass formation may occur due to frustration arising from the competition between chemical ordering and clustering. These observations are complemented by classical as well as ab initio molecular dynamics simulations. Our study indicates that these nanoscale phase-separated glasses are quite distinct from the single phase nanoglasses (studied by Gleiter and others) in the following three respects: (i) they contain at least two structurally and compositionally distinct, nanodispersed, glassy phases, (ii) these phases are separated by comparatively sharp inter-phase boundaries, and (iii) thermally induced crystallization occurs via a complex, multi-step mechanism. Such materials, therefore, appear to constitute a new class of disordered systems that may be called a composite nanoglass.

  5. Local structure, composition, and crystallization mechanism of a model two-phase “composite nanoglass”

    SciTech Connect

    Chattopadhyay, Soma; Shibata, Tomohiro; Kelly, S. D.; Balasubramanian, M.; Srinivasan, S. G.; Du, Jincheng; Banerjee, Rajarshi; Ayyub, Pushan

    2016-02-14

    We report a detailed study of the local composition and structure of a model, bi-phasic nanoglass with nominal stoichiometry Cu{sub 55}Nb{sub 45}. Three dimensional atom probe data suggest a nanoscale-phase-separated glassy structure having well defined Cu-rich and Nb-rich regions with a characteristic length scale of ≈3 nm. However, extended x-ray absorption fine structure analysis indicates subtle differences in the local environments of Cu and Nb. While the Cu atoms displayed a strong tendency to cluster and negligible structural order beyond the first coordination shell, the Nb atoms had a larger fraction of unlike neighbors (higher chemical order) and a distinctly better-ordered structural environment (higher topological order). This provides the first experimental indication that metallic glass formation may occur due to frustration arising from the competition between chemical ordering and clustering. These observations are complemented by classical as well as ab initio molecular dynamics simulations. Our study indicates that these nanoscale phase-separated glasses are quite distinct from the single phase nanoglasses (studied by Gleiter and others) in the following three respects: (i) they contain at least two structurally and compositionally distinct, nanodispersed, glassy phases, (ii) these phases are separated by comparatively sharp inter-phase boundaries, and (iii) thermally induced crystallization occurs via a complex, multi-step mechanism. Such materials, therefore, appear to constitute a new class of disordered systems that may be called a composite nanoglass.

  6. Transient thermographic technique for NDI of aerospace composite structures

    NASA Astrophysics Data System (ADS)

    McCullough, Robert W.

    2004-04-01

    Transient thermography is well established as a capable tool for non-destructive testing (NDT) in aerospace composite structures (see for example Favro, et. al 1995). The basic process involves altering the steady state thermal condition of a structure by adding or removing thermal energy (heat) and then observing the transient temperature patterns on a surface by means of a sensitive infrared imaging system. Many techniques for heat addition have been tried including most commonly convective and radiative transfer to external surfaces. As an NDT technique it is especially appealing for composite structures whose constituent thermal properties may vary considerably leading to interesting and illuminating transient patterns (Favro, et. al. 1993). We have developed a novel application of transient thermography with an application to detecting bonding flaws in boron/epoxy skinned aluminum honeycomb composite structures as found for example in the F14 and F15 aircraft. The technique described below uses induction to selectively heat the structure near the flaw region and has potential benefits in a range of applications.

  7. Noise transmission properties and control strategies for composite structures

    NASA Technical Reports Server (NTRS)

    Silcox, Richard J.; Beyer, Todd B.; Lester, Harold C.

    1991-01-01

    A study of several component technologies required to apply active control techniques to reduce interior noise in composite aircraft structures is described. The mechanisms of noise transmission in an all composite, large-scale, fuselage model are studied in an experimental program and found similar to mechanisms found in conventional aircraft construction. Two primary conditions of structural acoustic response are found to account for the dominant interior acoustic response. A preliminary study of active noise control in cylinders used piezoceramic actuators as force inputs for a simple aluminum fuselage model. These actuators provided effective control for the same two conditions of noise transmission found in the composite fuselage structure. The use of piezoceramic actuators to apply force inputs overcomes the weight and structural requirements of conventional shaker actuators. Finally, in order to accurately simulate these types of actuators in a cylindrical shell, two analytical models are investigated that apply either in-plane forces or bending moments along the boundaries of a finite patch. It is shown that the bending model may not be as effective as the force model for exciting the low order azimuthal modes that typically dominate the structural acoustic response in these systems. This result will affect the arrangement and distribution of actuators required for effective active control systems.

  8. End Effects and Load Diffusion in Composite Structures

    NASA Technical Reports Server (NTRS)

    Horgan, Cornelius O.; Ambur, D. (Technical Monitor); Nemeth, M. P. (Technical Monitor)

    2002-01-01

    The research carried out here builds on our previous NASA supported research on the general topic of edge effects and load diffusion in composite structures. Further fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures. Specific problems recently considered were focussed on end effects in sandwich structures and for functionally graded materials. Both linear and nonlinear (geometric and material) problems have been addressed. Our goal is the development of readily applicable design formulas for the decay lengths in terms of non-dimensional material and geometric parameters. Analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and assessing results from finite element analyses. The decay behavior of stresses and other field quantities provides a significant aid towards this process. The analysis is also amenable to parameter study with a large parameter space and should be useful in structural tailoring studies.

  9. Structural efficiency study of composite wing rib structures

    NASA Technical Reports Server (NTRS)

    Swanson, Gary D.; Gurdal, Zafer; Starnes, James H., Jr.

    1988-01-01

    A series of short stiffened panel designs which may be applied to a preliminary design assessment of an aircraft wing rib is presented. The computer program PASCO is used as the primary design and analysis tool to assess the structural efficiency and geometry of a tailored corrugated panel, a corrugated panel with a continuous laminate, a hat stiffened panel, a blade stiffened panel, and an unstiffened flat plate. To correct some of the shortcomings in the PASCO analysis when shear is present, a two step iterative process using the computer program VICON is used. The loadings considered include combinations of axial compression, shear, and lateral pressure. The loading ranges considered are broad enough such that the designs presented may be applied to other stiffened panel applications. An assessment is made of laminate variations, increased spacing, and nonoptimum geometric variations, including a beaded panel, on the design of the panels.

  10. Na/K-interdiffusion in alkali feldspar: new data on diffusion anisotropy and composition dependence

    NASA Astrophysics Data System (ADS)

    Schaeffer, Anne-Kathrin; Petrishcheva, Elena; Habler, Gerlinde; Abart, Rainer; Rhede, Dieter

    2013-04-01

    Exchange experiments between gem-quality alkali feldspar with an initial XOr of 0.85 or 0.72 and Na/K-salt melts have been conducted at temperatures between 800° and 1000° C. The crystals were prepared as crystallographically oriented plates, the polished surfaces corresponding to the (010) or (001) plane of the feldspar. The composition of the melts was varied systematically to induce a controlled shift of the feldspar towards more Na-rich or K-rich compositions (XOr 0.5 to 1). A molar excess of cations by a factor of 40 in the melt ensured constant concentration boundary conditions for cation exchange. Different geometries of diffusion profiles can be observed depending on the direction of the composition shift. For a shift towards more K-rich compositions the diffusion profile exhibits two plateaus corresponding to an exchanged rim in equilibrium with the melt and a completely unexchanged core, respectively. Between these plateaus an exchange front develops with an inflection point that progresses into the crystal with t1-2. The width of this diffusion front varies greatly with the extent of chemical shift and crystallographic direction. The narrowest profiles are always found in the direction normal to (010), i.e. b, marking the slowest direction of interdiffusion. A shift towards more Na-rich composition leads to the development of a crack system due to the composition strain associated with the substitution of the larger K+ion with the smaller Na+ion. The exchange front developing in this case lacks the inflection point observed for shifts towards more K-rich compositions. The observed geometry of the diffusion fronts can be explained by a composition dependence of the interdiffusion coefficient. We used the Boltzmann transformation to calculate the interdiffusion coefficient in dependence of composition from our data in a range between XOr 0.5 and 1 for profiles normal to both (010) and (001) and for different temperatures. As indicated by the different

  11. High temperature resin matrix composites for aerospace structures

    NASA Technical Reports Server (NTRS)

    Davis, J. G., Jr.

    1980-01-01

    Accomplishments and the outlook for graphite-polyimide composite structures are briefly outlined. Laminates, skin-stiffened and honeycomb sandwich panels, chopped fiber moldings, and structural components were fabricated with Celion/LARC-160 and Celion/PMR-15 composite materials. Interlaminar shear and flexure strength data obtained on as-fabricated specimens and specimens that were exposed for 125 hours at 589 K indicate that epoxy sized and polyimide sized Celion graphite fibers exhibit essentially the same behavior in a PMR-15 matrix composite. Analyses and tests of graphite-polyimide compression and shear panels indicate that utilization in moderately loaded applications offers the potential for achieving a 30 to 50 percent reduction in structural mass compared to conventional aluminum panels. Data on effects of moisture, temperature, thermal cycling, and shuttle fluids on mechanical properties indicate that both LARC-160 and PMR-15 are suitable matrix materials for a graphite-polyimide aft body flap. No technical road blocks to building a graphite-polyimide composite aft body flap are identified.

  12. Size- and composition-dependent radio frequency magnetic permeability of iron oxide nanocrystals.

    PubMed

    Yun, Hongseok; Liu, Xiyu; Paik, Taejong; Palanisamy, Duraivelan; Kim, Jungkwun; Vogel, William D; Viescas, Arthur J; Chen, Jun; Papaefthymiou, Georgia C; Kikkawa, James M; Allen, Mark G; Murray, Christopher B

    2014-12-23

    We investigate the size- and composition-dependent ac magnetic permeability of superparamagnetic iron oxide nanocrystals for radio frequency (RF) applications. The nanocrystals are obtained through high-temperature decomposition synthesis, and their stoichiometry is determined by Mössbauer spectroscopy. Two sets of oxides are studied: (a) as-synthesized magnetite-rich and (b) aged maghemite nanocrystals. All nanocrystalline samples are confirmed to be in the superparamagnetic state at room temperature by SQUID magnetometry. Through the one-turn inductor method, the ac magnetic properties of the nanocrystalline oxides are characterized. In magnetite-rich iron oxide nanocrystals, size-dependent magnetic permeability is not observed, while maghemite iron oxide nanocrystals show clear size dependence. The inductance, resistance, and quality factor of hand-wound inductors with a superparamagnetic composite core are measured. The superparamagnetic nanocrystals are successfully embedded into hand-wound inductors to function as inductor cores.

  13. Size- and Composition-Dependent Radio Frequency Magnetic Permeability of Iron Oxide Nanocrystals

    SciTech Connect

    Yun, H; Liu, XY; Paik, T; Palanisamy, D; Kim, J; Vogel, WD; Viescas, AJ; Chen, J; Papaefthymiou, GC; Kikkawa, JM; Allen, MG; Murray, CB

    2014-12-01

    We investigate the size- and composition-dependent ac magnetic permeability of superparamagnetic iron oxide nanocrystals for radio frequency (RF) applications. The nanocrystals are obtained through high-temperature decomposition synthesis, and their stoichiometry is determined by Mossbauer spectroscopy. Two sets of oxides are studied: (a) as-synthesized magnetite-rich and (b) aged maghemite nanocrystals. All nanocrystalline samples are confirmed to be in the superparamagnetic state at room temperature by SQUID magnetometry. Through the one-turn inductor method, the ac magnetic properties of the nanocrystalline oxides are characterized. In magnetite-rich iron oxide nanocrystals, size-dependent magnetic permeability is not observed, while maghemite iron oxide nanocrystals show clear size dependence. The inductance, resistance, and quality factor of hand-wound inductors with a superparamagnetic composite core are measured. The superparamagnetic nanocrystals are successfully embedded into hand-wound inductors to function as inductor cores.

  14. Optimization of SMA layers in composite structures to enhance damping

    NASA Astrophysics Data System (ADS)

    Haghdoust, P.; Cinquemani, S.; Lecis, N.; Bassani, P.

    2016-04-01

    The performance of lightweight structures can be severely affected by vibration. New design concepts leading to lightweight, slender structural components can increase the vulnerability of the components to failure due to excessive vibration. The intelligent approach to address the problem would be the use of materials which are more capable in dissipating the energy due to their high value of loss factor. Among the different materials available to achieve damping, much attention has been attached to the use of shape memory alloys (SMAs) because of their unique microstructure, leading to good damping capacity. This work describes the design and optimization of a hybrid layered composite structure for the passive suppression of flexural vibrations in slender and light structures. Embedding the SMA layers in composite structure allows to combine different properties: the lightness of the base composite (e.g. fiber glass), the mechanical strength of the insert of metallic material and the relevant damping properties of SMA, in the martensitic phase. In particular, we put our attention on embedding the CuZnAl in the form of thin sheet in a layered composite made by glass fiber reinforced epoxy. By appropriately positioning of the SMA sheets so that they are subjected to the maximum curvature, the damping of the hybrid system can be considerably enhanced. Accordingly analytical method for evaluating the energy dissipation of the thin sheets with different shapes and patterns is developed and is followed by a shape optimization based on genetic algorithm. Eventually different configurations of the hybrid beam structure with different patterns of SMA layer are proposed and compared in the term of damping capacity.

  15. Nonlinear analyses of composite aerospace structures in sonic fatigue

    NASA Technical Reports Server (NTRS)

    Mei, Chuh

    1993-01-01

    This report summarizes the semiannual research progress, accomplishments, and future plans performed under the NASA Langley Research Center Grant No. NAG-1-1358. The primary research effort of this project is the development of analytical methods for the prediction of nonlinear random response of composite aerospace structures subjected to combined acoustic and thermal loads. The progress, accomplishments, and future plates on four sonic fatigue research topics are described. The sonic fatigue design and passive control of random response of shape memory alloy hybrid composites presented in section 4, which is suited especially for HSCT, is a new initiative.

  16. Structural Health Monitoring of Composite Wound Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Grant, Joseph; Kaul, Raj; Taylor, Scott; Jackson, Kurt; Myers, George; Sharma, A.

    2002-01-01

    The increasing use of advanced composite materials in the wide range of applications including Space Structures is a great impetus to the development of smart materials. Incorporating these FBG sensors for monitoring the integrity of structures during their life cycle will provide valuable information about viability of the usage of such material. The use of these sensors by surface bonding or embedding in this composite will measure internal strain and temperature, and hence the integrity of the assembled engineering structures. This paper focuses on such a structure, called a composite wound pressure vessel. This vessel was fabricated from the composite material: TRH50 (a Mitsubishi carbon fiber with a 710-ksi tensile strength and a 37 Msi modulus) impregnated with an epoxy resin from NEWPORT composites (WDE-3D-1). This epoxy resin in water dispersed system without any solvents and it cures in the 240-310 degrees F range. This is a toughened resin system specifically designed for pressure applications. These materials are a natural fit for fiber sensors since the polyimide outer buffer coating of fiber can be integrated into the polymer matrix of the composite material with negligible residual stress. The tank was wound with two helical patterns and 4 hoop wraps. The order of winding is: two hoops, two helical and two hoops. The wall thickness of the composite should be about 80 mil or less. The tank should burst near 3,000 psi or less. We can measure the actual wall thickness by ultrasonic or we can burst the tank and measure the pieces. Figure 1 shows a cylinder fabricated out of carbon-epoxy composite material. The strain in different directions is measured with a surface bonded fiber Bragg gratings and with embedded fiber Bragg gratings as the cylinder is pressurized to burst pressures. Figure 2 shows the strain as a function of pressure of carbon-epoxy cylinder as it is pressurized with water. Strain is measured in different directions by multiple gratings

  17. Workshop on Scaling Effects in Composite Materials and Structures

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E. (Compiler)

    1994-01-01

    This document contains presentations and abstracts from the Workshop on Scaling Effects in Composite Materials and Structures jointly sponsored by NASA Langley Research Center, Virginia Tech, and the Institute for Mechanics and Materials at the University of California, San Diego, and held at NASA Langley on November 15-16, 1993. Workshop attendees represented NASA, other government research labs, the aircraft/rotorcraft industry, and academia. The workshop objectives were to assess the state-of-technology in scaling effects in composite materials and to provide guidelines for future research.

  18. Structure of a cyclin-dependent kinase from Giardia lamblia.

    PubMed

    Leibly, David J; Newling, Paul A; Abendroth, Jan; Guo, Wenjin; Kelley, Angela; Stewart, Lance J; Van Voorhis, Wesley

    2011-09-01

    Giardia lamblia is the etiologic agent of giardiasis, a water-borne infection that is prevalent throughout the world. The need for new therapeutics for the treatment of giardiasis is of paramount importance. Owing to the ubiquitous nature of kinases and their vital importance in organisms, they are potential drug targets. In this paper, the first structure of a cyclin-dependent kinase (CDK) from G. lamblia (GlCDK; UniProt A8BZ95) is presented. CDKs are cell-cycle-associated kinases that are actively being pursued as targets for anticancer drugs as well as for antiparasitic chemotherapy. Generally, a CDK forms a complex with its associated cyclin. This CDK-cyclin complex is active and acts as a serine/threonine protein kinase. Typically, CDKs are responsible for the transition to the next phase of the cell cycle. Although the structure of GlCDK with its associated cyclin was not solved, the 1.85 Å resolution structure of apo GlCDK and a 2.0 Å resolution structure of GlCDK in complex with adenosine monophosphate are presented and the structural differences from the orthologous human CDK2 and CDK3 are discussed.

  19. Three-axis distributed fiber optic strain measurement in 3D woven composite structures

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  20. 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

  1. Structural dependencies of protein backbone 2JNC' couplings.

    PubMed

    Juranić, Nenad; Dannenberg, J J; Cornilescu, Gabriel; Salvador, Pedro; Atanasova, Elena; Ahn, Hee-Chul; Macura, Slobodan; Markley, John L; Prendergast, Franklyn G

    2008-04-01

    Protein folding can introduce strain in peptide covalent geometry, including deviations from planarity that are difficult to detect, especially for a protein in solution. We have found dependencies in protein backbone (2)J(NC') couplings on the planarity and the relative orientation of the sequential peptide planes. These dependences were observed in experimental (2)J(NC') couplings from seven proteins, and also were supported by DFT calculations for a model tripeptide. Findings indicate that elevated (2)J(NC') couplings may serve as reporters of structural strain in the protein backbone imposed by protein folds. Such information, supplemented with the H-bond strengths derived from (h3)J(NC') couplings, provides useful insight into the overall energy profile of the protein backbone in solution.

  2. Structural dependencies of protein backbone 2JNC′ couplings

    PubMed Central

    Juranić, Nenad; Dannenberg, J.J.; Cornilescu, Gabriel; Salvador, Pedro; Atanasova, Elena; Ahn, Hee-Chul; Macura, Slobodan; Markley, John L.; Prendergast, Franklyn G.

    2008-01-01

    Protein folding can introduce strain in peptide covalent geometry, including deviations from planarity that are difficult to detect, especially for a protein in solution. We have found dependencies in protein backbone 2JNC′ couplings on the planarity and the relative orientation of the sequential peptide planes. These dependences were observed in experimental 2JNC′ couplings from seven proteins, and also were supported by DFT calculations for a model tripeptide. Findings indicate that elevated 2JNC′ couplings may serve as reporters of structural strain in the protein backbone imposed by protein folds. Such information, supplemented with the H-bond strengths derived from h3JNC′ couplings, provides useful insight into the overall energy profile of the protein backbone in solution. PMID:18305196

  3. Structural dependence of Mn complexation by siderophores: Donor group dependence on complex stability and reactivity

    NASA Astrophysics Data System (ADS)

    Harrington, James M.; Parker, Dorothy L.; Bargar, John R.; Jarzecki, Andrzej A.; Tebo, Bradley M.; Sposito, Garrison; Duckworth, Owen W.

    2012-07-01

    Siderophores traditionally have been viewed as solely being involved in the biogeochemical cycling of Fe(III). This paradigm, however, ignores the diverse roles siderophores may play in the cycling of other trace metals, such as Mn, Co, Mo, and V. Recent work has shown that siderophores form complexes with high stability constants with Mn(III), which are in some cases higher than that of the corresponding Fe(III) complex. Herein, we report on a structural analysis of the dissolved Fe(III)- and Mn(III)-siderophore complexes of rhizoferrin and two pyoverdin-type siderophores using X-ray spectroscopic techniques. Additionally, the stability constants of the Mn(III)-pyoverdinPaA and Mn(III)-rhizoferrin complexes have been quantified as log β111 = 47.5 ± 0.3 and log β110 = 29.8 ± 0.3, respectively. Comparisons of thermodynamic stability and solution structures of Fe(III)- and Mn(III)-complexes with a variety of siderophores demonstrate the relationship between donor group identity, siderophore structure, and strength of complex formation. Rhizoferrin and two mixed-moiety pyoverdins bind with a higher affinity for Mn(III) than Fe(III), possibly because of binding moiety composition which makes them better able to accommodate Jahn-Teller distortion. In contrast, Fe(III) forms complexes of higher relative stability with siderophores that contain hydroxamate and catecholate moieties, more rigid donor groups that form five-membered chelate rings.

  4. Structural brain differences in alcohol-dependent individuals with and without comorbid substance dependence

    PubMed Central

    Mon, Anderson; Durazzo, Timothy C.; Abe, Christoph; Gazdzinski, Stefan; Pennington, David; Schmidt, Thomas; Meyerhoff, Dieter J.

    2014-01-01

    Background Over 50% of individuals with alcohol use disorders (AUD) also use other substances. Therefore, brain structural abnormalities observed in alcohol dependent individuals may not be entirely related to alcohol consumption. This MRI study assessed differences in brain regional tissue volumes between short-term abstinent alcohol dependent individuals without (ALC) and with current substance use dependence (polysubstance users, PSU). Methods Nineteen, one-month-abstinent PSU and 40 ALC as well as 27 light-drinkers (LD) were studied on a 1.5 Tesla MR system. Whole brain T1-weighted images were segmented automatically into regional gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) volumes. MANOVA assessed group differences of intracranial volume-normalized tissue volumes of the frontal, parietal, occipital, and temporal lobes as well as regional subcortical GM volumes. The volumetric measures were correlated with neurocognitive measures to assess their functional relevance. Results Despite similar lifetime drinking and smoking histories, PSU had significantly larger normalized WM volumes than ALC in all lobes. PSU also had larger frontal and parietal WM volumes than LD, but smaller temporal GM volumes as well as smaller lenticular and thalamic nuclei than LD. By contrast, ALC had smaller frontal, parietal, and temporal GM, thalamic GM and cerebellar volumes than LD. ALC also had more sulcal CSF volumes than both PSU and LD. Conclusion One-month-abstinent ALC and PSU exhibited different patterns of gross brain structural abnormalities. The larger lobar WM volumes in PSU in the absence of widespread GM volume loss contrast with widespread GM atrophy in ALC. These structural differences between ALC and PSU may demand different treatment approaches to mitigate specific functionally relevant brain abnormalities. PMID:25263262

  5. Fabricating Composite-Material Structures Containing SMA Ribbons

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Cano, Roberto J.; Lach, Cynthia L.

    2003-01-01

    An improved method of designing and fabricating laminated composite-material (matrix/fiber) structures containing embedded shape-memory-alloy (SMA) actuators has been devised. Structures made by this method have repeatable, predictable properties, and fabrication processes can readily be automated. Such structures, denoted as shape-memory-alloy hybrid composite (SMAHC) structures, have been investigated for their potential to satisfy requirements to control the shapes or thermoelastic responses of themselves or of other structures into which they might be incorporated, or to control noise and vibrations. Much of the prior work on SMAHC structures has involved the use SMA wires embedded within matrices or within sleeves through parent structures. The disadvantages of using SMA wires as the embedded actuators include (1) complexity of fabrication procedures because of the relatively large numbers of actuators usually needed; (2) sensitivity to actuator/ matrix interface flaws because voids can be of significant size, relative to wires; (3) relatively high rates of breakage of actuators during curing of matrix materials because of sensitivity to stress concentrations at mechanical restraints; and (4) difficulty of achieving desirable overall volume fractions of SMA wires when trying to optimize the integration of the wires by placing them in selected layers only.

  6. Passive Cooling Enabled by Polymer Composite Coating: Dependence on Filler, Filler Size and Coating Thickness

    NASA Astrophysics Data System (ADS)

    Shao, Yue; Shi, Frank G.

    2017-02-01

    The effective passive radiation cooling that is enabled by silicone-based composites is investigated for its dependence on coating thickness and filler size in the range of nanometers to micrometers. It is established, contrary to prior reports, that the effective passive radiation cooling does not exhibit a filler size dependence, i.e., there is no optimal size at which a maximum cooling would be reached. However, the apparent cooling effect is filler type dependent and among the fillers investigated, Al2O3 exhibits the best apparent cooling effect. In addition, the apparent cooling effect is dependent on coating thickness: the thickness dependence is non-monotonic, and the maximum cooling occurs at an optimal thickness of 70 μm, regardless of filler type. Potential significant implications of the findings are also discussed.

  7. Composition-structure-function diagrams of Ti-Ni-Au thin film shape memory alloys.

    PubMed

    Buenconsejo, Pio John S; Ludwig, Alfred

    2014-12-08

    Ti-Ni-Au thin film materials libraries were prepared from multilayer precursors by combinatorial sputtering. The materials libraries were annealed at 500, 600, and 700 °C for 1 h and then characterized by high-throughput methods to investigate the relations between composition, structure and functional properties. The identified relations were visualized in functional phase diagrams. The goal is to identify composition regions that are suitable as high temperature shape memory alloys. Phase transforming compositions were identified by electrical resistance measured during thermal cycles in the range of -20 and 250 °C. Three phase transformation paths were confirmed: (1) B2-R, (2) B2-R-B19', and (3) B2-B19. For the materials library annealed at 500 °C only the B2-R transformation was observed. For the materials libraries annealed at 600 and 700 °C, all transformation paths were observed. High transformation temperatures (M(s) ≈ 100 °C) were only obtained by annealing at 600 or 700 °C, and with compositions of Ti ≈ 50 at. % and Au > 20 at. %. This is the composition range that undergoes B2-B19 transformation. The phase transformation behaviors were explained according to the compositional and annealing temperature dependence of phase/structure formation, as revealed by X-ray diffraction analysis of the materials libraries.

  8. 77 FR 4890 - Damage Tolerance and Fatigue Evaluation for Composite Rotorcraft Structures, and Damage Tolerance...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-01

    ... static strength of composite rotorcraft structures using a damage tolerance evaluation, or a fatigue... regulations to require evaluation of fatigue and residual static strength of composite rotorcraft...

  9. Nonlinearity and Strain-Rate Dependence in the Deformation Response of Polymer Matrix Composites Modeled

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.

    2000-01-01

    There has been no accurate procedure for modeling the high-speed impact of composite materials, but such an analytical capability will be required in designing reliable lightweight engine-containment systems. The majority of the models in use assume a linear elastic material response that does not vary with strain rate. However, for containment systems, polymer matrix composites incorporating ductile polymers are likely to be used. For such a material, the deformation response is likely to be nonlinear and to vary with strain rate. An analytical model has been developed at the NASA Glenn Research Center at Lewis Field that incorporates both of these features. A set of constitutive equations that was originally developed to analyze the viscoplastic deformation of metals (Ramaswamy-Stouffer equations) was modified to simulate the nonlinear, rate-dependent deformation of polymers. Specifically, the effects of hydrostatic stresses on the inelastic response, which can be significant in polymers, were accounted for by a modification of the definition of the effective stress. The constitutive equations were then incorporated into a composite micromechanics model based on the mechanics of materials theory. This theory predicts the deformation response of a composite material from the properties and behavior of the individual constituents. In this manner, the nonlinear, rate-dependent deformation response of a polymer matrix composite can be predicted.

  10. The factor structure of the DSM-III-R and ICD-10 concepts of alcohol dependence.

    PubMed

    Caetano, R

    1990-01-01

    This paper describes the factor structure of the concept of alcohol dependence as proposed in two psychiatric classifications, the DSM-III-R and the ICD-10. Subjects are 219 men and 162 women who were interviewed while in treatment for alcohol-related problems in nine different treatment programs in Contra Costa county, California. Tests of hypotheses supporting a single factor and a dual factor structure of dependence were rejected by confirmatory factor analysis. Results from exploratory factor analysis show a four factor structure for the concept of dependence in DSM-III-R. For ICD-10 there is a four factor solution among men and a three factor solution among women. The item composition of these factors vary by gender and across the two classifications. However, there is good agreement between dependence as measured by DSM-III-R and ICD-10 criteria. Since work on DSM-IV is now under way, the present research aims to provide some empirical base for how future changes should be made.

  11. Structural CNT Composites Part II: Assessment of CNT Yarns as Reinforcement for Composite Overwrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo; Sauti, Godfrey; Cano, Roberto J.; Wincheski, Russell A.; Ratcliffe, James G.; Czabaj, Michael; Siochi, Emilie J.

    2015-01-01

    Carbon nanotubes (CNTs) are one-dimensional nanomaterials with outstanding electrical and thermal conductivities and mechanical properties. This combination of properties offers routes to enable lightweight structural aerospace components. Recent advances in the manufacturing of CNTs have made bulk forms such as yarns, tapes and sheets available in commercial quantities to permit the evaluation of these materials for aerospace use, where the superior tensile properties of CNT composites can be exploited in tension dominated applications such as composite overwrapped pressure vessels (COPVs). To investigate their utility in this application, aluminum rings were overwrapped with thermoset/CNT yarn composite and their mechanical properties measured. CNT composite overwrap characteristics such as processing method, CNT/resin ratio, and applied tension during CNT yarn winding were varied to determine their effects on the mechanical performance of the CNT composite overwrapped Al rings (CCOARs). Mechanical properties of the CCOARs were measured under static and cyclic loads at room, elevated, and cryogenic temperatures to evaluate their mechanical performance relative to bare Al rings. At room temperature, the breaking load of CCOARs with a 10.8% additional weight due to the CNT yarn/thermoset overwrap increased by over 200% compared to the bare Al ring. The quality of the wound CNT composites was also investigated using x-ray computed tomography.

  12. Buckling Design and Imperfection Sensitivity of Sandwich Composite Launch-Vehicle Shell Structures

    NASA Technical Reports Server (NTRS)

    Schultz, Marc R.; Sleight, David W.; Myers, David E.; Waters, W. Allen, Jr.; Chunchu, Prasad B.; Lovejoy, Andrew W.; Hilburger, Mark W.

    2016-01-01

    shell. When compared with the current buckling design recommendations, the results suggest that the current recommendations are overly conservative and that the development of new recommendations could reduce the acreage areal mass of many composite sandwich shell designs by between 4% and 19%, depending on the structure.

  13. Physical disturbance to ecological niches created by soil structure alters community composition of methanotrophs.

    PubMed

    Kumaresan, Deepak; Stralis-Pavese, Nancy; Abell, Guy C J; Bodrossy, Levente; Murrell, J Colin

    2011-10-01

    Aggregates of different sizes and stability in soil create a composite of ecological niches differing in terms of physico-chemical and structural characteristics. The aim of this study was to identify, using DNA-SIP and mRNA-based microarray analysis, whether shifts in activity and community composition of methanotrophs occur when ecological niches created by soil structure are physically perturbed. Landfill cover soil was subject to three treatments termed: 'control' (minimal structural disruption), 'sieved' (sieved soil using 2 mm mesh) and 'ground' (grinding using mortar and pestle). 'Sieved' and 'ground' soil treatments exhibited higher methane oxidation potentials compared with the 'control' soil treatment. Analysis of the active community composition revealed an effect of physical disruption on active methanotrophs. Type I methanotrophs were the most active methanotrophs in 'sieved' and 'ground' soil treatments, whereas both Type I and Type II methanotrophs were active in the 'control' soil treatment. The result emphasize that changes to a particular ecological niche may not result in an immediate change to the active bacterial composition and change in composition will depend on the ability of the bacterial communities to respond to the perturbation.

  14. Cu−In−Ga−S quantum dot composition-dependent device performance of electrically driven light-emitting diodes

    SciTech Connect

    Kim, Jong-Hoon; Lee, Ki-Heon; Jo, Dae-Yeon; Yang, Heesun; Lee, Yangjin; Hwang, Jun Yeon

    2014-09-29

    Colloidal synthesis of ternary and quaternary quantum dots (QDs) of In/Ga ratio-varied Cu−In{sub 1−x}−Ga{sub x}−S (CIGS) with nominal x = 0, 0.5, 0.7, and 1 and their application for the fabrication of quantum dot-light-emitting diodes (QLEDs) are reported. Four QLEDs having CIGS QDs with different compositions are all solution-processed in the framework of multilayered structure, where QD emitting layer is sandwiched by hybrid charge transport layers of poly(9-vinlycarbazole) and ZnO nanoparticles. The device performance such as luminance and efficiency is found to be strongly dependent on the composition of CIGS QDs, and well interpreted by the device energy level diagram proposed through the determination of QD valence band minima by photoelectron emission spectroscopic measurement.

  15. Empirical expression for the composition and temperature dependence of the energy gap in InAlSb

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Sun, Weiguo; Lv, Yanqiu

    2017-03-01

    An empirical expression for the energy bandgap as a function of alloy composition x and temperature for In1-xAlxSb was reported. The In1-xAlxSb epitaxial layers were grown by molecular beam epitaxy (MBE) on InSb(1 0 0) substrate, utilizing a p+-p+-n-n+ structure. High resolution X-ray diffraction was used to characterize the epitaxial layers. The Al composition of 2.8% was obtained by assuming the Bragg's formula and Vegard's law. Spectral response measurement of the diodes has been employed to investigate the temperature dependence of the band gap of In1-xAlxSb alloys in the range between 77 K and 260 K. The calculated results for energy gap of InAlSb were in good agreement with the available data and our experimental observation.

  16. Use of microfasteners to produce damage tolerant composite structures

    PubMed Central

    Hallett, Stephen R.

    2016-01-01

    The paper concerns the mechanical performance of continuous fibre/thermosetting polymer matrix composites reinforced in the through-thickness direction with fibrous or metallic rods or threads in order to mitigate against low delamination resistance. Specific illustrations of the effects of microfasteners in reducing delamination crack growth are made for Z-pinned and tufted composites. Response to loading in such ‘structured materials’ is subject to multiple parameters defining their in-plane and out-of-plane properties. Single microfastener mechanical tests are well suited to establish the crack bridging laws under a range of loading modes, from simple delamination crack opening to shear, and provide the basis for predicting the corresponding response of microfastener arrays, within a given material environment. The fundamental experiments on microfasteners can be used to derive analytical expressions to describe the crack bridging behaviour in a general sense, to cover all possible loadings. These expressions can be built into cohesive element constitutive laws in a finite-element framework for modelling the effects of microfastener arrays on the out-of-plane mechanical response of reinforced structural elements, including the effects of known manufacturing imperfections. Such predictive behaviour can then be used to assess structural integrity under complex loading, as part of the component design process. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242299

  17. Concurrent Probabilistic Simulation of High Temperature Composite Structural Response

    NASA Technical Reports Server (NTRS)

    Abdi, Frank

    1996-01-01

    A computational structural/material analysis and design tool which would meet industry's future demand for expedience and reduced cost is presented. This unique software 'GENOA' is dedicated to parallel and high speed analysis to perform probabilistic evaluation of high temperature composite response of aerospace systems. The development is based on detailed integration and modification of diverse fields of specialized analysis techniques and mathematical models to combine their latest innovative capabilities into a commercially viable software package. The technique is specifically designed to exploit the availability of processors to perform computationally intense probabilistic analysis assessing uncertainties in structural reliability analysis and composite micromechanics. The primary objectives which were achieved in performing the development were: (1) Utilization of the power of parallel processing and static/dynamic load balancing optimization to make the complex simulation of structure, material and processing of high temperature composite affordable; (2) Computational integration and synchronization of probabilistic mathematics, structural/material mechanics and parallel computing; (3) Implementation of an innovative multi-level domain decomposition technique to identify the inherent parallelism, and increasing convergence rates through high- and low-level processor assignment; (4) Creating the framework for Portable Paralleled architecture for the machine independent Multi Instruction Multi Data, (MIMD), Single Instruction Multi Data (SIMD), hybrid and distributed workstation type of computers; and (5) Market evaluation. The results of Phase-2 effort provides a good basis for continuation and warrants Phase-3 government, and industry partnership.

  18. 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.

  19. Effects of thermal cycling on composite materials for space structures

    NASA Technical Reports Server (NTRS)

    Tompkins, Stephen S.

    1989-01-01

    The effects of thermal cycling on the thermal and mechanical properties of composite materials that are candidates for space structures are briefly described. The results from a thermal analysis of the orbiting Space Station Freedom is used to define a typical thermal environment and the parameters that cause changes in the thermal history. The interactions of this environment with composite materials are shown and described. The effects of this interaction on the integrity as well as the properties of GR/thermoset, Gr/thermoplastic, Gr/metal and Gr/glass composite materials are discussed. Emphasis is placed on the effects of the interaction that are critical to precision spacecraft. Finally, ground test methodology are briefly discussed.

  20. Activation and micropore structure of carbon-fiber composites

    SciTech Connect

    Jagtoyen, M.; Derbyshire, F.; Kimber, G.

    1997-12-01

    Rigid, high surface area activated carbon fiber composites have been produced with high permeabilities for environmental applications in gas and water purification. The project involves a collaboration between the Oak Ridge National Laboratory (ORNL) and the Center for Applied Energy Research (CAER), University of Kentucky. The main focus of recent work has been to find a satisfactory means to uniformly activate large samples of carbon fiber composites to produce controlled pore structures. Processes have been developed using activation in steam and CO{sub 2}, and a less conventional method involving oxygen chemisorption and subsequent heat treatment. Another objective has been to explore applications for the activated composites in environmental applications related to fossil energy production.

  1. Doubly responsive polymer-microgel composites: rheology and structure.

    PubMed

    Monti, Fabrice; Fu, Shang-Yi; Iliopoulos, Ilias; Cloitre, Michel

    2008-10-21

    Mixtures of alkali swellable microgels and linear PNIPAm chains exhibit doubly responsive properties both with pH and temperature. Below the lower critical solution temperature (LCST), the linear chains of PNIPAm are soluble and increase the osmotic pressure outside the microgels, which causes them to deswell. Above the LCST, the PNIPAm chains become insoluble and form spherical colloidal particles confined between the microgels that subsequently reswell. The swelling and deswelling of the microgels change the rheological properties of the composites, providing a unique way to tune the elasticity of the composites with temperature. The structure of the composites above the LCST is studied using multiple light scattering and fluorescence confocal microscopy. The phase separation of PNIPAm above the LCST is strongly affected by the confinement of the PNIPAm chains between the microgels.

  2. Structural investigation of carbon/carbon composites by neutron scattering

    NASA Astrophysics Data System (ADS)

    Prem, Manfred; Krexner, Gerhard; Peterlik, Herwig

    2006-11-01

    Carbon/carbon (C/C) composite material was investigated by means of small-angle as well as wide-angle elastic neutron scattering. The C/C-composites were built up from bi-directionally woven fabrics from PAN-based carbon fibers. Pre-impregnation with phenolic resin was followed by pressure curing and carbonization at 1000 °C and a final heat treatment at either 1800 or 2400 °C. Measurements of the samples were performed in orientations arranging the carbon fibers, respectively, parallel and perpendicular to the incoming beam. Structural features of the fibers as well as the inherently existing pores are presented and the influence of the heat treatment is discussed. The results are compared to earlier X-ray investigations of carbon fibers and C/C-composites.

  3. Material and structural studies of metal and polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

    1972-01-01

    The application of fiber composites to aeronautical and space vehicle systems indicates the following: It appears quite probable that resin/fiber composites can be developed for service at 315 C for several thousand hours and at 370 C for a few hundred hours. The retention of resin/fiber strength at these high temperatures can be achieved by modifying the polymer molecular structure or by developing new processing techniques, or both. Carbon monofilament with attractive strength values has been produced and fabrication studies to reinforce aluminum with such monofilaments have been initiated. Refractory wire-superalloy composites have demonstrated sufficiently high strength and impact values to suggest that they have potential for application to turbine blades at temperatures to 1200 C and above.

  4. Temperature-Dependent Transport of Composite Fermions at Exactly ν = 1/2 Landau Level Filling^**

    NASA Astrophysics Data System (ADS)

    Kang, Woowon

    1996-03-01

    We have studied the temperature dependent resistivity at exactly half Landau-level filling of a high-quality two-dimensional electron system in high magnetic field^1. The low-temperature transport at ν = 1/2 Landau-level filling is well parameterized by temperature dependent impurity and phonon scattering of a Fermi liquid of composite fermions with a mass m^*. The gauge field mediated composite fermion-phonon scattering contributes a T-3-dependence to the total mobility. The effective mass of composite fermions is obtained from the temperature dependence of composite fermion-impurity scattering and is somewhat larger than the the masses derived by Shubnikov-de Haas measurements away from half-filling^2,3. The resistivity at high temperatures can be well described by a softening of the composite fermion Fermi-edge. We also observe an anomalous increase in the effective mass under increased illumination at ν = 1/2. This can be understood as either resulting from a change in the effective interaction length between electrons or from decreased fluctuations which reduces the smearing of the divergence of the mass at exactly ν = 1/2. It is remarkable that the scattering behavior around ν = 1/2 can be described in such a simple single-particle picture. ^**Work done in collaboration with S. He, H.L. Stormer, L.N. Pfeiffer, K.W. West, and K.W. Baldwin, AT&T Bell Laboratories. ^1 W. Kang, S. He, H.L. Stormer, K.W. Baldwin, L.N. Pfeiffer, and K.W. West, Phys. Rev. Lett. 75, 4106 (1995). ^2H.C. Manoharan, M. Shayegan, and S.J. Klepper, Phys. Rev. Lett. 73, 3270 (1994). ^3 R.R. Du, H.L. Stormer, D.C. Tsui, A.S. Yeh, L.N. Pfeiffer, and K.W. West, Phys. Rev. Lett. 73, 3274 (1994).

  5. Stokes shift dynamics in (ionic liquid + polar solvent) binary mixtures: composition dependence.

    PubMed

    Daschakraborty, Snehasis; Ranjit, Biswas

    2011-04-14

    An approximate semimolecular theory has been developed to investigate the composition dependence of Stokes shift dynamics of a fluorescent dye molecule dissolved in binary mixtures of an ionic liquid (IL) with a conventional polar solvent at different mole fractions. The theory expresses the dynamic Stokes shift as a sum of contributions from the dye-IL and the dye-polar solvent interactions and suggests substantial solute-cation dipole-dipole interaction contribution to the solvation energy relaxation. The theory, when applied to aqueous mixtures of 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF(6)]) and tetrafluoroborate ([Bmim][BF(4)]), and binary mixtures of ([Bmim][BF(4)] + acetonitrile), predicts reduction of Stokes shift but acceleration of the dynamics upon increasing the polar solvent concentration for the most part of the mixture composition. The decrease in dynamic Stokes shift values has been found to occur due to decrease of the dye-IL interaction in the presence of the added polar solvent. For aqueous binary mixtures of IL, the predicted results are in semiquantitative agreement with the available experimental results. However, the calculated dynamics suggest much weaker composition dependence than that observed in experiments. In addition, the theory predicts a turn around for dynamic Stokes shift in its composition dependence for ([Bmim][BF(4)] + acetonitrile) mixtures at higher dilutions of the IL. Interestingly, effective dipolar medium calculations for Stokes shift dynamics in ([Bmim][BF(4)] + dichloromethane) binary mixtures predict a very weak or even nonexistent nonlinear composition dependence. These predictions should be reexamined in experiments.

  6. Communication: Striking dependence of diffusion kinetics in Ag–Cu nanoalloys upon composition and quantum effects

    SciTech Connect

    Asgari, Mehdi; Negreiros, Fabio R.; Sementa, Luca; Barcaro, Giovanni; Fortunelli, Alessandro; Behnejad, Hassan

    2014-07-28

    The kinetics of elemental inter-diffusion in Ag–Cu nanoalloys of 32–34 atoms around 80:20 composition is theoretically investigated by combining analytic-potential and first-principles calculations. An extremely varied behavior is found, with transformation times ranging from tens of nanoseconds to weeks at room temperature in a narrow interval of size and composition, also depending on quantum effects in magic clusters. Predictions are consistent with time-of-flight experiments and suggest their interpretation in a new light.

  7. Photoluminescence structure, and composition of laterally anodized porous Si

    NASA Technical Reports Server (NTRS)

    Jung, K. H.; Shih, S.; Kwong, D. L.; George, T.; Lin, T. L.; Liu, H. Y.; Zavada, J.

    1992-01-01

    We have studied the photoluminescence (PL), structure, and composition of laterally anodized porous Si. Broad PL peaks were observed centered between about 620-720 nm with strong intensities measured from 500 to 860 nm. Macroscopic variations in PL intensities and peak positions are explained in terms of the structure and anodization process. Structural studies suggest that the PL appears to originate from a multilayered porous Si structure in which the top two layers are amorphous. X-ray diffraction spectra also suggest the presence of a significant amorphous phase. In addition to high concentrations of B and N, we have measured extremely high concentrations much greater than 10 exp 20 cu cm of H, C, O, and F. Our results indicate that laterally anodized porous Si does not fit the crystalline Si quantum wire model prevalent in the literature suggesting that some other structure is responsible for the observed luminescence.

  8. Composite Panel Postbuckling Behavior and General Model of Joints in Composite Structures

    NASA Technical Reports Server (NTRS)

    Zamula, G. N.; Kutinov, V. F.; Vasilyev, V. V.; Grishin, V. I.; Ierusalimsky, K. M.; Azikov, N. S.; Begeyev, T. K.

    1996-01-01

    The present paper is a final technical report on the research programme NCCW-73 accomplished within co-operation between NASA of the USA and GOSKOMOBORONPROM of Russia in the field of aeronautics. The report contains basic results of studies in two areas, 'Analysis of postbuckling behavior of composite panels' and 'Development of general model of joints in composite structures'; these results were obtained in conformity with requirements of NCCW-73. In addition, consideration is given to some related issues, and proposals for further studies are formulated.

  9. Structural basis for proteolysis-dependent activation of the poliovirus RNA-dependent RNA polymerase

    PubMed Central

    Thompson, Aaron A; Peersen, Olve B

    2004-01-01

    The active RNA-dependent RNA polymerase of poliovirus, 3Dpol, is generated by cleavage of the 3CDpro precursor protein, a protease that has no polymerase activity despite containing the entire polymerase domain. By intentionally disrupting a known and persistent crystal packing interaction, we have crystallized the poliovirus polymerase in a new space group and solved the complete structure of the protein at 2.0 Å resolution. It shows that the N-terminus of fully processed 3Dpol is buried in a surface pocket where it makes hydrogen bonds that act to position Asp238 in the active site. Asp238 is an essential residue that selects for the 2′ OH group of substrate rNTPs, as shown by a 2.35 Å structure of a 3Dpol–GTP complex. Mutational, biochemical, and structural data further demonstrate that 3Dpol activity is exquisitely sensitive to mutations at the N-terminus. This sensitivity is the result of allosteric effects where the structure around the buried N-terminus directly affects the positioning of Asp238 in the active site. PMID:15306852

  10. Synthesis, Structural, and Adsorption Properties and Thermal Stability of Nanohydroxyapatite/Polysaccharide Composites.

    PubMed

    Skwarek, Ewa; Goncharuk, Olena; Sternik, Dariusz; Janusz, Wladyslaw; Gdula, Karolina; Gun'ko, Vladimir M

    2017-12-01

    A series of composites based on nanohydroxyapatite (nHAp) and natural polysaccharides (PS) (nHAp/agar, nHAp/chitosan, nHAp/pectin FB300, nHAp/pectin APA103, nHAp/sodium alginate) was synthesized by liquid-phase two-step method and characterized using nitrogen adsorption-desorption, DSC, TG, FTIR spectroscopy, and SEM. The analysis of nitrogen adsorption-desorption data shows that composites with a nHAp: PS ratio of 4:1 exhibit a sufficiently high specific surface area from 49 to 82 m(2)/g. The incremental pore size distributions indicate mainly mesoporosity. The composites with the component ratio 1:1 preferably form a film-like structure, and the value of S BET varies from 0.3 to 43 m(2)/g depending on the nature of a polysaccharide. Adsorption of Sr(II) on the composites from the aqueous solutions has been studied. The thermal properties of polysaccharides alone and in nHAp/PS show the influence of nHAp, since there is a shift of characteristic DSC and DTG peaks. FTIR spectroscopy data confirm the presence of functional groups typical for nHAp as well as polysaccharides in composites. Structure and morphological characteristics of the composites are strongly dependent on the ratio of components, since nHAp/PS at 4:1 have relatively large S BET values and a good ability to adsorb metal ions. The comparison of the adsorption capacity with respect to Sr(II) of nHAp, polysaccharides, and composites shows that it of the latter is higher than that of nHAp (per 1 m(2) of surface).

  11. Synthesis, Structural, and Adsorption Properties and Thermal Stability of Nanohydroxyapatite/Polysaccharide Composites

    NASA Astrophysics Data System (ADS)

    Skwarek, Ewa; Goncharuk, Olena; Sternik, Dariusz; Janusz, Wladyslaw; Gdula, Karolina; Gun'ko, Vladimir M.

    2017-02-01

    A series of composites based on nanohydroxyapatite (nHAp) and natural polysaccharides (PS) (nHAp/agar, nHAp/chitosan, nHAp/pectin FB300, nHAp/pectin APA103, nHAp/sodium alginate) was synthesized by liquid-phase two-step method and characterized using nitrogen adsorption-desorption, DSC, TG, FTIR spectroscopy, and SEM. The analysis of nitrogen adsorption-desorption data shows that composites with a nHAp: PS ratio of 4:1 exhibit a sufficiently high specific surface area from 49 to 82 m2/g. The incremental pore size distributions indicate mainly mesoporosity. The composites with the component ratio 1:1 preferably form a film-like structure, and the value of S BET varies from 0.3 to 43 m2/g depending on the nature of a polysaccharide. Adsorption of Sr(II) on the composites from the aqueous solutions has been studied. The thermal properties of polysaccharides alone and in nHAp/PS show the influence of nHAp, since there is a shift of characteristic DSC and DTG peaks. FTIR spectroscopy data confirm the presence of functional groups typical for nHAp as well as polysaccharides in composites. Structure and morphological characteristics of the composites are strongly dependent on the ratio of components, since nHAp/PS at 4:1 have relatively large S BET values and a good ability to adsorb metal ions. The comparison of the adsorption capacity with respect to Sr(II) of nHAp, polysaccharides, and composites shows that it of the latter is higher than that of nHAp (per 1 m2 of surface).

  12. Structural Health Monitoring of Composite Structures Using Fiber Optic Sensors

    NASA Astrophysics Data System (ADS)

    Williams, Charles Phillip Michael

    In an aircraft engine at high altitude, the low-pressure turbine (LPT) section can experience low-Reynolds number (Re) flows making the turbine blades susceptible to large separation losses. These losses are detrimental to the performance of the turbine and lead to a roadblock for "higher-lift" blade designs. Accurate prediction of the separation characteristics and an understanding of mitigation techniques are of the utmost importance. The current study conducts simulations of flow control techniques for the Air Force Research Laboratory (AFRL) L2A turbine blade at low-Re of 10,000 based on inlet velocity and blade axial chord. This blade was selected for its "high-lift" characteristics coupled with massive separation on the blade at low-Re which provides an excellent test blade for flow control techniques. Flow control techniques involved various configurations of vortex generator jets (VGJs) using momentum injection (i.e. jet blowing). All computations were executed on dual-topology, multi-block, structured meshes and incorporated the use of a parallel computing platform using the message passing interface (MPI) communications. A high-order implicit large eddy simulation (ILES) approach was used in the simulations allowing for a seamless transition between laminar, transitional, and turbulent flow without changing flow solver parameters. A validation study was conducted involving an AFRL L1A turbine blade which showed good agreement with experimental trends for cases which controlled separation in the experiments. The same cases showed good agreement between different grid sizes. The differences between experimental and numerical results are largely attributed to differences in the setup. That is, the simulation did not include freestream turbulence or wind-tunnel wall effects. The flow control study conducted for the L2A blade showed a small degree of separation control for jets placed just downstream (DS) of the separation point. A limited study was conducted

  13. Spreading rate dependence of three-dimensional structure in oceanic spreading centres

    NASA Astrophysics Data System (ADS)

    Parmentier, E. M.; Morgant, Jason Phipps

    1990-11-01

    SEGMENTATION by transform faults and other types of along-axis discontinuity1 is a well described but poorly explained characteristic of oceanic spreading centres. Here we use numerical experiments to explore the dynamics of mantle flow and melting beneath a mid-ocean ridge. Buoyant upwelling, driven by compositional density variations resulting from the extraction of the melt that forms the ocean crust, exhibits a spreading-rate-dependent transition between two-dimensional and three-dimensional upwelling structures. For low spreading rates and mantle viscosities an initial two-dimensional structure transforms into a three-dimensional one; at high spreading rates, an initially two-dimensional structure remains two-dimensional. These results suggest that the origin of spreading-centre segmentation may be different at fast and slow spreading rates.

  14. Solution to certain problems in the failure of composite structures

    NASA Astrophysics Data System (ADS)

    Goodsell, Johnathan

    The present work contains the solution of two problems in composite structures. In the first, an approximate elasticity solution for prediction of the displacement, stress and strain fields within the m-layer, symmetric and balanced angle-ply composite laminate of finite-width subjected anticlastic bending deformation is developed. The solution is shown to recover classical laminated plate theory predictions at interior regions of the laminate and thereby illustrates the boundary layer character of this interlaminar phenomenon. The results exhibit the anticipated response in congruence with the solutions for uniform axial extension and uniform temperature change, where divergence of the interlaminar shearing stress is seen to occur at the intersection of the free-edge and planes between lamina of +theta and -theta orientation. The analytical results show excellent agreement with the finite-element predictions for the same boundary-value problem and thereby provide an efficient and compact solution available for parametric studies of the influence of geometry and material properties. The solution is combined with previously developed solutions for uniform axial extension and uniform temperature change of the identical laminate and the combined solution is exercised to compare the relative magnitudes of free-edge phenomenon arising from the different loading conditions, to study very thick laminates and laminates where the laminate width is less than the laminate thickness. Significantly, it was demonstrated that the solution is valid for arbitrary stacking sequence and the solution was exercised to examine antisymmetric and non-symmetric laminates. Finally, the solution was exercised to determine the dimensions of the boundary layer for very large numbers of layers. It was found that the dimension of the boundary layer width in bending is approximately twice that in uniform axial extension and uniform temperature change. In the second, the intrinsic flaw concept is

  15. Structure and Properties of Teflon Composites with Natural Diamond Powders

    NASA Astrophysics Data System (ADS)

    Okhlopkova, A. A.; Shits, E. Yu.

    2004-03-01

    The results of experimental investigations of the structure and properties of composites based on polytetrafluorethylene (PTFE) containing natural diamond powders (NDP) of different dispersity are presented. To obtain diamond-containing compositions for antifrictional applications, we used a preliminary mechanical treatment of NDP (40 μm) in a planetary mill. It was stated that the formation of the maximum ordered small-spherulite structure of PTFE after injection of NDP significantly increased the wear resistance and deformational and strength characteristics of the polymer composite materials. To produce abrasive materials, PTFE was filled with NDP having a larger graininess (from 40 to 125 μm). It was found that the injection of NDP did not cause evident morphological changes in the binder — the bonds between diamond grains and the polymer are created by physicomechanical forces. To strengthen the adhesion interaction at the interface between the binder and diamond grains and to raise the wear resistance of the material, a complex modification of the polymer with inorganic and organic fillers was carried out. It is shown that the injection of the complex filler significantly improves the tribotechnical and operational properties of the diamond-containing composite material. The general laws of the influence of NDP on the formation of the supermolecular structure of PTFE are revealed. It is shown that, by varying the degree of dispersity and the content of NDP in PTFE, and by applying different methods of their injection into the polymer matrix, it is possible to control the operational properties of the composites and to produce materials of different functional application, from antifrictional to abrasive ones.

  16. Composition and grain size effects on the structural and mechanical properties of CuZr nanoglasses

    SciTech Connect

    Adibi, Sara; Branicio, Paulo S. Zhang, Yong-Wei; Joshi, Shailendra P.

    2014-07-28

    Nanoglasses (NGs), metallic glasses (MGs) with a nanoscale grain structure, have the potential to considerably increase the ductility of traditional MGs while retaining their outstanding mechanical properties. We investigated the effects of composition on the structural and mechanical properties of CuZr NG films with grain sizes between 3 to 15 nm using molecular dynamics simulations. Results indicate a transition from localized shear banding to homogeneous superplastic flow with decreasing grain size, although the critical average grain size depends on composition: 5 nm for Cu{sub 36}Zr{sub 64} and 3 nm for Cu{sub 64}Zr{sub 36}. The flow stress of the superplastic NG at different compositions follows the trend of the yield stress of the parent MG, i.e., Cu{sub 36}Zr{sub 64} yield/flow stress: 2.54 GPa/1.29 GPa and Cu{sub 64}Zr{sub 36} yield/flow stress: 3.57 GPa /1.58 GPa. Structural analysis indicates that the differences in mechanical behavior as a function of composition are rooted at the distinct statistics of prominent atomic Voronoi polyhedra. The mechanical behavior of NGs is also affected by the grain boundary thickness and the fraction of atoms at interfaces for a given average grain size. The results suggest that the composition dependence of the mechanical behavior of NGs follows that of their parent MGs, e.g., a stronger MG will generate a stronger NG, while the intrinsic tendency for homogeneous deformation occurring at small grain size is not affected by composition.

  17. Advanced Ceramic Matrix Composites with Multifunctional and Hybrid Structures

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Morscher, Gregory N.

    2004-01-01

    Ceramic matrix composites are leading candidate materials for a number of applications in aeronautics, space, energy, and nuclear industries. Potential composite applications differ in their requirements for thickness. For example, many space applications such as "nozzle ramps" or "heat exchangers" require very thin (< 1 mm) structures whereas turbine blades would require very thick parts (> or = 1 cm). Little is known about the effect of thickness on stress-strain behavior or the elevated temperature tensile properties controlled by oxidation diffusion. In this study, composites consisting of woven Hi-Nicalon (trademark) fibers a carbon interphase and CVI SiC matrix were fabricated with different numbers of plies and thicknesses. The effect of thickness on matrix crack formation, matrix crack growth and diffusion kinetics will be discussed. In another approach, hybrid fiber-lay up concepts have been utilized to "alloy" desirable properties of different fiber types for mechanical properties, thermal stress management, and oxidation resistance. Such an approach has potential for the C(sub I)-SiC and SiC(sub f)-SiC composite systems. CVI SiC matrix composites with different stacking sequences of woven C fiber (T300) layers and woven SiC fiber (Hi-Nicalon (trademark)) layers were fabricated. The results will be compared to standard C fiber reinforced CVI SiC matrix and Hi-Nicalon reinforced CVI SiC matrix composites. In addition, shear properties of these composites at different temperatures will also be presented. Other design and implementation issues will be discussed along with advantages and benefits of using these materials for various components in high temperature applications.

  18. Impact Testing and Simulation of Composite Airframe Structures

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E.; Littell, Justin D.; Horta, Lucas G.; Annett, Martin S.; Fasanella, Edwin L.; Seal, Michael D., II

    2014-01-01

    Dynamic tests were performed at NASA Langley Research Center on composite airframe structural components of increasing complexity to evaluate their energy absorption behavior when subjected to impact loading. A second objective was to assess the capabilities of predicting the dynamic response of composite airframe structures, including damage initiation and progression, using a state-of-the-art nonlinear, explicit transient dynamic finite element code, LS-DYNA. The test specimens were extracted from a previously tested composite prototype fuselage section developed and manufactured by Sikorsky Aircraft Corporation under the US Army's Survivable Affordable Repairable Airframe Program (SARAP). Laminate characterization testing was conducted in tension and compression. In addition, dynamic impact tests were performed on several components, including I-beams, T-sections, and cruciform sections. Finally, tests were conducted on two full-scale components including a subfloor section and a framed fuselage section. These tests included a modal vibration and longitudinal impact test of the subfloor section and a quasi-static, modal vibration, and vertical drop test of the framed fuselage section. Most of the test articles were manufactured of graphite unidirectional tape composite with a thermoplastic resin system. However, the framed fuselage section was constructed primarily of a plain weave graphite fabric material with a thermoset resin system. Test data were collected from instrumentation such as accelerometers and strain gages and from full-field photogrammetry.

  19. Polycaprolactone/starch composite: Fabrication, structure, properties, and applications.

    PubMed

    Ali Akbari Ghavimi, Soheila; Ebrahimzadeh, Mohammad H; Solati-Hashjin, Mehran; Abu Osman, Noor Azuan

    2015-07-01

    Interests in the use of biodegradable polymers as biomaterials have grown. Among the different polymeric composites currently available, the blend of starch and polycaprolactone (PCL) has received the most attention since the 1980s. Novamont is the first company that manufactured a PCL/starch (SPCL) composite under the trademark Mater-Bi®. The properties of PCL (a synthetic, hydrophobic, flexible, expensive polymer with a low degradation rate) and starch (a natural, hydrophilic, stiff, abundant polymer with a high degradation rate) blends are interesting because of the composite components have completely different structures and characteristics. PCL can adjust humidity sensitivity of starch as a biomaterial; while starch can enhance the low biodegradation rate of PCL. Thus, by appropriate blending, SPCL can overcome important limitations of both PCL and starch components and promote controllable behavior in terms of mechanical properties and degradation which make it suitable for many biomedical applications. This article reviewed the different fabrication and modification methods of the SPCL composite; different properties such as structural, physical, and chemical as well as degradation behavior; and different applications as biomaterials.

  20. Large Area Nondestructive Evaluation of a Fatigue Loaded Composite Structure

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Burke, Eric R.; Horne, Michael R.; Madaras, Eric I.

    2016-01-01

    Large area nondestructive evaluation (NDE) inspections are required for fatigue testing of composite structures to track damage initiation and growth. Of particular interest is the progression of damage leading to ultimate failure to validate damage progression models. In this work, passive thermography and acoustic emission NDE were used to track damage growth up to failure of a composite three-stringer panel. Fourteen acoustic emission sensors were placed on the composite panel. The signals from the array were acquired simultaneously and allowed for acoustic emission location. In addition, real time thermal data of the composite structure were acquired during loading. Details are presented on the mapping of the acoustic emission locations directly onto the thermal imagery to confirm areas of damage growth leading to ultimate failure. This required synchronizing the acoustic emission and thermal data with the applied loading. In addition, processing of the thermal imagery which included contrast enhancement, removal of optical barrel distortion and correction of angular rotation before mapping the acoustic event locations are discussed.