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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Ultrasonic stress wave characterization of composite materials

The work reported covers three simultaneous projects. The first project was concerned with: (1) establishing the sensitivity of the acousto-ultrasonic method for evaluating subtle forms of damage development in cyclically loaded composite materials, (2) establishing the ability of the acousto-ultrasonic method for detecting initial material imperfections that lead to localized damage growth and final specimen failure, and (3) characteristics of the NBS/Proctor sensor/receiver for acousto-ultrasonic evaluation of laminated composite materials. The second project was concerned with examining the nature of the wave propagation that occurs during acoustic-ultrasonic evaluation of composite laminates and demonstrating the role of Lamb or plate wave modes and their utilization for characterizing composite laminates. The third project was concerned with the replacement of contact-type receiving piezotransducers with noncontacting laser-optical sensors for acousto-ultrasonic signal acquisition.

Duke, J. C., Jr.↗
NASA NTRS1993

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

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

Levit, R.↗
NASA NTRS2017

Fabrication of Lightweight Radiation Shielding Composite Materials by Field Assisted Sintering Technique (FAST)

Advances in radiation shielding technologies are needed to protect humans and electronic components from all threats of space radiation over long durations. In this paper, we report on the use of the innovative and novel fabrication technology known as Field Assisted Sintering Technology (FAST) to fabricate lightweight material with enhanced radiation shielding strength to safeguard humans and electronics suitable for next generation space exploration missions. The base materials we investigated were aluminum (Al), the current standard material for space hardware, and Ultra-High Molecular Weight Polyethylene (UHMWPE), which has high hydrogen content and resistance to nuclear reaction from neutrons, making it a good shielding material for both gamma radiation and particles. UHMWPE also has high resistance to corrosive chemicals, extremely low moisture sensitivity, very low coefficient of friction, and high resistance to abrasion. We reinforced the base materials by adding high density (ie, high atomic weight) metallic material into the composite. These filler materials included: boron carbide (B4C), tungsten (W), tungsten carbide (WC) and gadolinium (Gd).

Prasad, Narasimha↗
NASA NTRS1987

Energy absorption in composite materials for crashworthy structures

Crash energy-absorption processes in composite materials have been studied as part of a research program aimed at the development of energy absorbing subfloor beams for crashworthy military helicopters. Based on extensive tests on glass/epoxy, graphite/epoxy, and Kevlar/epoxy composites, it is shown that the energy-absorption characteristics and crushing modes of composite beams are similar to those exhibited by tubular specimens of similar material and architecture. The crushing mechanisms have been determined and related to the mechanical properties of the constituent materials and specimen architecture. A simple and accurate method for predicting the energy-absorption capability of composite beams has been developed.

Farley, Gary L.↗
NASA NTRS1995

NDE Elastic Properties of Fiber-Reinforced Composite Materials

Fiber-reinforced composites are increasingly replacing metallic alloys as structural materials for primary components of fracture-critical structures. This trend is a result of the growing understanding of material behavior and recognition of the desirable properties of composites. A research program was conducted on NDE methods for determining the elastic properties of composites.

Composites NDE ultrasonic plate waves laminates↗
NASA NTRS1988

Global/local finite element analysis of composite materials

The motivation for performing global/local finite element analysis in composite materials is described. An example of such an analysis of a composite plate with a central circular hole is presented. Deformed finite element grids and interlaminar normal stress distributions are presented to aid understanding of the plate response. Such distribution at the plate edge is shown to be basically unaffected, although transverse displacements of the edge were slightly different from an analysis of a similar plate with no hole.

Griffin, O. Hayden, Jr.↗
NASA NTRS2014

Verification and Validation of a Three-Dimensional Generalized Composite Material Model

A general purpose orthotropic elasto-plastic computational constitutive material model has been developed to improve predictions of the response of composites subjected to high velocity impact. The three-dimensional orthotropic elasto-plastic composite material model is being implemented initially for solid elements in LS-DYNA as MAT213. In order to accurately represent the response of a composite, experimental stress-strain curves are utilized as input, allowing for a more general material model that can be used on a variety of composite applications. The theoretical details are discussed in a companion paper. This paper documents the implementation, verification and qualitative validation of the material model using the T800- F3900 fiber/resin composite material.

Finite Element Method↗
NASA NTRS1984

Space exposure of composite materials for large space structures (A0134)

The objective of this experiment is to evaluate the effects of the near-Earth orbital environment on the physical and chemical properties of laminated continuous-filament composites and composites resin films for use in large space structures and advanced spacecraft. The experiment is passive and occupies about one-half of a 6-in.-deep peripheral tray. Specimens of composite materials and polymeric and resin films are arranged above and below the experiment mounting plate to enable both exposure and nonexposure to sunlight. This provides a comparison of the effects of ultraviolet plus vacuum plus thermal cycling and those of vacuum plus thermal cycling on these materials. The experiment tray is thermally isolated from the Long Duration Exposure Facility structure to allow the material specimens to experience a wide range of thermal cycles. Tensile and compression specimens will be used to evaluate the laminated composite materials. A number of the specimens are precut and ready for testing after space exposure, whereas other specimens will be prepared from larger samples.

Wayne S Slemp↗
NASA NTRS1981

Acoustic emission monitoring of polymer composite materials

The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

Bardenheier, R.↗
NASA NTRS2015

Verification and Validation of a Three-Dimensional Generalized Composite Material Model

A general purpose orthotropic elasto-plastic computational constitutive material model has been developed to improve predictions of the response of composites subjected to high velocity impact. The three-dimensional orthotropic elasto-plastic composite material model is being implemented initially for solid elements in LS-DYNA as MAT213. In order to accurately represent the response of a composite, experimental stress-strain curves are utilized as input, allowing for a more general material model that can be used on a variety of composite applications. The theoretical details are discussed in a companion paper. This paper documents the implementation, verification and qualitative validation of the material model using the T800-F3900 fiber/resin composite material

Plasticity↗
DOE OSTI2024

Convergent laser beam shapes: Unveiling the dynamics of Laser-induced elastic waves in composite materials

Overcoming the low signal-to-noise ratio (SNR) in laser ultrasonic testing of composite materials remains a significant challenge. Current efforts focus on enhancing SNR by inserting more energy into the material through temporal and/or spatial modulation of the laser beam. However, potential SNR improvements through wave convergence and wave energy manipulation have been overlooked. This paper addresses this gap by demonstrating the convergence of different wave types to a designated point and by showing the feasibility of directing absorbed laser energy into a specific wave type through spatial modulation of the laser beam. To achieve this, mathematical expressions for the convergent laser beams are derived. Various laser beam profiles are then introduced to the thermoelastic equations and solved using the finite element method. The sample under investigation is a transversely isotropic unidirectional carbon fiber reinforced plastic, characterized by anisotropic thermal expansion coefficients and thermal conductivities. Results reveal pronounced convergence of the intended wave type at the center due to laser beam shaping. This study showcases the ability to direct absorbed laser energy toward a specific wave type through spatial modulation of the laser beam and highlights the role of material anisotropy in energy focusing.

composite materials↗
NASA NTRS1988

Advanced composite materials for precision segmented reflectors

The objective in the NASA Precision Segmented Reflector (PSR) project is to develop new composite material concepts for highly stable and durable reflectors with precision surfaces. The project focuses on alternate material concepts such as the development of new low coefficient of thermal expansion resins as matrices for graphite fiber reinforced composites, quartz fiber reinforced epoxies, and graphite reinforced glass. Low residual stress fabrication methods will be developed. When coupon specimens of these new material concepts have demonstrated the required surface accuracies and resistance to thermal distortion and microcracking, reflector panels will be fabricated and tested in simulated space environments. An important part of the program is the analytical modeling of environmental stability of these new composite materials concepts through constitutive equation development, modeling of microdamage in the composite matrix, and prediction of long term stability (including viscoelasticity). These analyses include both closed form and finite element solutions at the micro and macro levels.

Stein, Bland A.↗
NASA NTRS1989

Five year ground exposure of composite materials used on the Bell Model 206L flight service evaluation

Part of the results of a U.S. Army/NASA-Langley sponsored research program to establish the long term-term effects of realistic ground based exposure on advanced composite materials is presented. Residual strengths and moisture absorption as a function of exposure time and exposure location are reported for four different composite material systems that were exposed for five years on the North American Continent.

Baker, Donald J.↗
NASA NTRS1988

The viscoplastic behavior of SCS6/Ti-15-3 metal matrix composite materials at elevated temperatures

Titanium-based metal matrix composite materials (MMC'S) are being considered for use in the National Aerospace Plane. It is expected that these materials will be subjected to temperatures ranging up to about 820 C (1500 F). The present study was a preliminary investigation intended to quantify the level of viscoplastic behavior exhibited by SCS6/Ti-15-3 MMC's at elevated temperatures. The study consisted of a series of uniaxial creep/creep recovery tests. These tests were conducted in air at a temperature of 535 C (1000 F). Three distinct types of specimens were tested: Ti-15-3 heat matrix specimens (O2/plus or minus 45) sub s composite specimens, and (90 sub 2/plus or minus 45) sub s composite specimens. Tensile loads were applied to the specimens using a lever-arm creep frame equipped with a high temperature furnace. Specimen creep stains were monitored using an LVDT-based extensometer.

Tuttle, Mark E.↗
NASA NTRS1979

Mechanical and thermophysical properties of graphite/polyimide composite materials

An on-going program to characterize advanced composites for up to 50,000 hours of exposure to simulated supersonic cruise environments is summarized. Results are presented for up to 25,000 hours of thermal exposure and 10,000 hours of flight simulation at temperatures up to 560K (550 F) with emphasis on HTS/710 graphite/polyimide composite material. Results to date indicate that the maximum use temperature for HTS/710 may be reduced to 505K (450 F) for long-time (1000 hours) application such as the supersonic transport. Preliminary thermophysical properties data for HTS/PMR15 graphite/polyimide were generated. These data include thermal conductivity, thermal expansion, and specific heat from 115K (-252 F) to 590K (600 F) and emittance at room temperature and 590K (600 F). The purpose in generating these data was to validate use of state-of-the-art property measurement methods for advanced graphite fiber reinforced resin matrix composites. Based on results to this point, thermal expansion measurements for composites are most difficult to perform. A high degree of caution in conducting thermal expansion tests and analyzing results is required to produce reliable data.

Rummler, D. R.↗