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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Workshop on Scaling Effects in Composite Materials and Structures

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.

Karen E Jackson↗
NASA NTRS1997

Thermal Conductivity Database of Various Structural Carbon-Carbon Composite Materials

Advanced thermal protection materials envisioned for use on future hypersonic vehicles will likely be subjected to temperatures in excess of 1811 K (2800 F) and, therefore, will require the rapid conduction of heat away from the stagnation regions of wing leading edges, the nose cap area, and from engine inlet and exhaust areas. Carbon-carbon composite materials are candidates for use in advanced thermal protection systems. For design purposes, high temperature thermophysical property data are required, but a search of the literature found little thermal conductivity data for carbon-carbon materials above 1255 K (1800 F). Because a need was recognized for in-plane and through-the-thickness thermal conductivity data for carbon-carbon composite materials over a wide temperature range, Langley Research Center (LaRC) embarked on an effort to compile a consistent set of thermal conductivity values from room temperature to 1922 K (3000 F) for carbon-carbon composite materials on hand at LaRC for which the precursor materials and thermal processing history were known. This report documents the thermal conductivity data generated for these materials. In-plane thermal conductivity values range from 10 to 233 W/m-K, whereas through-the-thickness values range from 2 to 21 W/m-K.

Ohlhorst, Craig W.↗
NASA NTRS1973

Composite materials in space structures

The use of composite materials in space vehicle structures offers significant advantages in reduction of structural weight fractions and in obtaining improved dynamic characteristics. Recent studies and developments include inertial booms for scientific satellites, structural components for future space shuttle applications, and pressurized tanks. Future applications could include major portions of vehicle primary structures as well as many secondary structural components. A number of problems still exist regarding achievement of the objectives, including development of sufficient environmental data, reliable design techniques, and general user confidence. These will be attacked in future R&D programs.

Mayer, N. J.↗
NASA NTRS1975

Industry technology assessment of graphite-polymide composite materials

An assessment of the current state of the art and the future prospects for graphite polyimide composite material technology is presented. Presentations and discussions given at a minisymposium of major issues on the present and future use, availability, processing, manufacturing, and testing of graphite polyimide composite materials are summarized.

Source record↗
NASA NTRS2001

Finite Element Analysis of Active and Sensory Thermopiezoelectric Composite Materials

Analytical formulations are developed to account for the coupled mechanical, electrical, and thermal response of piezoelectric composite materials. The coupled response is captured at the material level through the thermopiezoelectric constitutive equations and leads to the inherent capability to model both the sensory and active responses of piezoelectric materials. A layerwise laminate theory is incorporated to provide more accurate analysis of the displacements, strains, stresses, electric fields, and thermal fields through-the-thickness. Thermal effects which arise from coefficient of thermal expansion mismatch, pyroelectric effects, and temperature dependent material properties are explicitly accounted for in the formulation. Corresponding finite element formulations are developed for piezoelectric beam, plate, and shell elements to provide a more generalized capability for the analysis of arbitrary piezoelectric composite structures. The accuracy of the current formulation is verified with comparisons from published experimental data and other analytical models. Additional numerical studies are also conducted to demonstrate additional capabilities of the formulation to represent the sensory and active behaviors. A future plan of experimental studies is provided to characterize the high temperature dynamic response of piezoelectric composite materials.

Lee, Ho-Jun↗
NASA NTRS1994

The Influence of SiC on the Ablation Response of Advanced Refractory Composite Materials

In continuing our studies of advanced refractory composite materials we have recently completed an arc-jet test series of a diverse group of ceramics and ceramic matrix composites. The compositions range from continuous fiber reinforced ceramics to monoliths. Many of these materials contain SiC and one objective of this test series was to identify the influence of SiC oxidation mechanisms on material performance. Hence the arc heater was operated at two conditions; one in which the passive oxidation of SiC would be dominant and the other where the active oxidation of SiC would be dominant. It is shown here that the active oxidation mechanism of SiC does not dominate material performance when it is present at levels equal to or below 20 volume percent.

Bull, Jeffrey D.↗
NASA NTRS1991

Environmental exposure effects on composite materials for commercial aircraft

A study was conducted to determine the effects of long term flight and ground exposure on three commercially available graphite-epoxy material systems: T300/5208, T300/5209, and T300/934. Sets of specimens were exposed on commercial aircraft and ground racks for 1, 2, 3, 5, and 10 years. Inflight specimen sites included both the interior and exterior of aircraft based in Hawaii, Texas, and New Zealand. Ground racks were located at NASA-Dryden and the above mentioned states. Similar specimens were exposed to controlled lab conditions for up to 2 years. After each exposure, specimens were tested for residual strength and a dryout procedure was used to measure moisture content. Both room and high temperature residual strengths were measured and expressed as a pct. of the unexposed strength. Lab exposures included the effects of time alone, moisture, time on moist specimens, weatherometer, and simulated ground-air-ground cycling. Residual strengths of the long term specimens were compared with residual strengths of the lab specimens. Strength retention depended on the exposure condition and the material system. Results showed that composite materials can be successfully used on commercial aircraft if environmental effects are considered.

Hoffman, Daniel J.↗
NASA NTRS2003

The Application of Metal Matrix Composite Materials in Propulsion System Valves

Metal Matrix Composite (MMC) materials have been developed and used in many applications to reduce the weight of components where weight and deflection are the driving design requirement. MMC materials are being developed for use in some propulsion system components, such as turbo-pumps and thrust chambers. However, to date, no propulsion system valves have been developed that take advantage of the materials unique properties. The stiffness of MMC's could help keep valves light or improve life where deflection is the design constraint (such as seal and bearing locations). The low CTE of the materials might allow the designer to reduce tolerances and clearances producing better performance and lighter weight valves. Using unique manufacturing processes allow parts to be plated/coated for longer life and allow joining either by welding or threading/bolting. Additionally, casting of multi part pre-forms to form a single part can lead to designs that would be hard or impossible to manufacture with other methods. Therefore, NASA's Marshall Space Flight Center (MSFC) has developed and tested a prototype propulsion system valve that utilizes these materials to demonstrate these advantages. Through design and testing, this effort will determine the best use of these materials in valves designed to achieve the goal of a highly reliable and lightweight propulsion system. This paper is a continuation of the paper, The Application of Metal Matrix Composite Materials In Propulsion System Valves, presented at the JANNAF Conference held in April, 2002. Fabrication techniques employed, valve development, and valve test results will be discussed in this paper.

Laszar, John↗
NASA NTRS1982

Fatigue and fracture research in composite materials

The fatigue, fracture, and impact behavior of composite materials are investigated. Bolted and bonded joints are included. The solutions developed are generic in scope and are useful for a wide variety of structural applications. The analytical tools developed are used to demonstrate the damage tolerance, impact resistance, and useful fatigue life of structural composite components. Standard tests for screening improvements in materials and constituents are developed.

T. Kevin O'Brien↗
NASA NTRS1978

Deformation and failure information from composite materials via acoustic emission

The paper reviews some principles of applying acoustic emission (AE) to the study of fiber-composite materials and structures. This review covers the basics of using AE to monitor the deformation and fracture processes that occur when fiber-composite materials are stressed. Also, new results in some areas of current research interest are presented. The following areas are emphasized: study of couplants for AE testing of composites, evaluation of a special immersion-type AE transducer, and wave propagation complications and the development of techniques for locating AE sources in Kevlar 49/epoxy composite pre

Hamstad, M. A.↗
NASA NTRS1976

Composite materials research in support of supersonic propulsion systems

Two engine components, fan blades and exhaust systems, were selected for composite materials development efforts in support of the supersonic cruise aircraft research (SCAR) engine program. The materials selected were boron/aluminum for fan blades and silicon carbide/superalloy sheet for the exhaust system. The current status of the research into applying these two composite materials to SCAR engines is reviewed.

Signorelli, R. A.↗
NASA NTRS1994

Ultrasonic Inspection Of Composite-Material Paraboloid

Ultrasonic imaging system scanning three-dimensional curved surfaces developed. In original application, system used to determine integrity of composite-material paraboloidal reflector and its supporting structure. System also used to inspect composite-material structures with curved surfaces other than paraboloids, provided surfaces describable by mathematical functions. Position and orientation of transducer adjusted continuously to maintain normal incidence.

Chern, E. James↗
NASA NTRS2000

Pistons and Cylinders Made of Carbon-Carbon Composite Materials

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon---carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

H. Kevin Rivers↗
NASA NTRS1973

Finite element analysis of a composite material interface

A finite element model of a composite material interface is developed to study the influence of the interface on the thermal strain in the composite. A plane stress model is used with an axisymmetric model as a check. The interface thickness, thermal coefficient, modulus, Poisson's ratio and the percent of mineral in the composite are variables in the study. The results confirmed the usability of the finite element model in studying the polymer-mineral interface.

Murray, K. H.↗
NASA NTRS1988

Stress concentration around circular hole in a composite material specimen representative of the X-29A forward-swept wing aircraft

The theory of anisotropic elasticity was used to evaluate the anisotropic stress concentration factors of a composite laminated plate containing a small circular hole. This advanced composite material was used to manufacture the X-29A forward swept wing. Observe that the usual isotropic material stress concentration factor is three. However, for composite material, it was found that the anisotropic stress concentration factor is no longer constant, and that the locations of maximum tangential stress points could shift by changing the fiber orientation with respect to the loading axis. The analysis showed that through the lamination process, the stress concentration factor could be drastically reduced, and therefore the structural performance could be improved. Both the mixture rule approach and the constant strain approach were used to calculate the stress concentration factor. The results predicted by the mixture rule approach were about 20 percent deviate from the experimental data. However, the results predicted by the constant strain approach matched the testing data very well. This showed the importance of the inplane shear effect on the evaluation of stress concentration factor for the X-29A composite plate.

Yeh, Hsien-Yang↗