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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Development of Aluminum Composites for a Rocket Engine's Lightweight Thrust Cell

The Aerospike liquid fueled rocket engine for the X-33 aerospace vehicle consists of several thrust cells, which can comprise as much as 25% of the engine weight. The interior wall of the thrust cell chamber is exposed to high temperature combustion products and must be cooled by using liquid hydrogen. Ultimately, reducing engine weight would increase vehicle performance and allow heavier payload capabilities. Currently, the thrust cell's structural jacket and manifolds are made of stainless steel 347, which can potentially be replaced by a lighter material such as an Aluminum (Al) Metal Matrix Composites (MMC). Up to 50% weight reduction can be expected for each of the thrust cell chambers using particulate SiC reinforced Al MMC. Currently, several Al MMC thrust cell structural jackets have been produced, using cost-effective processes such as gravity casting and plasma spray deposition, to demonstrate MMC technology readiness for NASA's advanced propulsion systems.

Lee, Jonathan A.↗
NASA NTRS2001

Development of Metal Matrix Composites for NASA's Advanced Propulsion Systems

The state-of-the-art development of several Metal Matrix Composites (MMC) for NASA's advanced propulsion systems will be presented. The goal is to provide an overview of NASA-Marshall Space Flight Center's on-going activities in MMC components for advanced liquid rocket engines such as the X-33 vehicle's Aerospike engine and X-34's Fastrac engine. The focus will be on lightweight, low cost, and environmental compatibility with oxygen and hydrogen of key MMC materials, within each of NASA's new propulsion application, that will provide a high payoff for NASA's Reusable Launch Vehicles and space access vehicles. In order to fabricate structures from MMC, effective joining methods must be developed to join MMC to the same or to different monolithic alloys. Therefore, a qualitative assessment of MMC's welding and joining techniques will be outlined.

Lee, J.↗
NASA NTRS2001

Metal Matrix Composite Materials for Aerospace Applications

Metal matrix composites (MMC) are attractive materials for aerospace applications because of their high specific strength, high specific stiffness, and lower thermal expansion coefficient. They are affordable since complex parts can be produced by low cost casting process. As a result there are many commercial and Department of Defense applications of MMCs today. This seminar will give an overview of MMCs and their state-of-the-art technology assessment. Topics to be covered are types of MMCs, fabrication methods, product forms, applications, and material selection issues for design and manufacture. Some examples of current and future aerospace applications will also be presented and discussed.

Bhat, Biliyar N.↗
NASA NTRS2001

Spin Forming of Aluminum Metal Matrix Composites

An exploratory effort between NASA-Marshall Space Flight Center (MSFC) and SpinCraft, Inc., to experimentally spin form cylinders and concentric parts from small and thin sheets of aluminum Metal Matrix Composites (MMC), successfully yielded good microstructure data and forming parameters. MSFC and SpinCraft will collaborate on the recent technical findings and develop strategy to implement this technology for NASA's advanced propulsion and airframe applications such as pressure bulkheads, combustion liner assemblies, propellant tank domes, and nose cone assemblies.

Lee, Jonathan A.↗
NASA NTRS2005

Effects of Control Mode and R-Ratio on the Fatigue Behavior of a Metal Matrix Composite

Composite Because of their high specific stiffness and strength at elevated temperatures, continuously reinforced metal matrix composites (MMC's) are under consideration for a future generation of aeropropulsion systems. Since components in aeropropulsion systems experience substantial cyclic thermal and mechanical loads, the fatigue behavior of MMC's is of great interest. Almost without exception, previous investigations of the fatigue behavior of MMC's have been conducted in a tension-tension, load-controlled mode. This has been due to the fact that available material is typically less than 2.5-mm thick and, therefore, unable to withstand high compressive loads without buckling. Since one possible use of MMC's is in aircraft skins, this type of testing mode may be appropriate. However, unlike aircraft skins, most engine components are thick. In addition, the transient thermal gradients experienced in an aircraft engine will impose tension-compression loading on engine components, requiring designers to understand how the MMC will behave under fully reversed loading conditions. The increased thickness of the MMC may also affect the fatigue life. Traditionally, low-cycle fatigue (LCF) tests on MMC's have been performed in load control. For monolithic alloys, low-cycle fatigue tests are more typically performed in strain control. Two reasons justify this choice: (1) the critical volume from which cracks initiate and grow is generally small and elastically constrained by the larger surrounding volume of material, and (2) load-controlled, low-cycle fatigue tests of monolithics invariably lead to unconstrained ratcheting and localized necking--an undesired material response because the failure mechanism is far more severe than, and unrelated to, the fatigue mechanism being studied. It is unknown if this is the proper approach to composite testing. However, there is a lack of strain-controlled data on which to base any decisions. Consequently, this study addresses the isothermal, LCF behavior of a [0]_32 MMC tested under strain- and load-controlled conditions for both zero-tension and tension-compression loading conditions. These tests were run at 427 C on thick specimens of SiC-reinforced Ti-15-3. For the fully-reversed tests, no difference was observed in the lives between the load- and strain-controlled tests. However, for the zero-tension tests, the strain-controlled tests had longer lives by a factor of 3 in comparison to the load-controlled tests. This was due to the fact that under strain-control the specimens cyclically softened, reducing the cracking potential. In contrast, the load-controlled tests ratcheted toward larger tensile strains leading to an eventual overload of the fibers. Fatigue tests revealed that specimens tested under fully-reversed conditions had lives approximately an order of magnitude longer than for those specimens tested under zero tension. When examined on a strain-range basis, the fully reversed specimens had similar, but still shorter lives than those of the unreinforced matrix material. However, the composite had a strain limitation at short lives because of the limited strain capacity of the brittle ceramic fiber. The composite also suffered at very high lives because of the lack of an apparent fatigue limit in comparison to the unreinforced matrix. The value of adding fibers to the matrix is apparent when the fatigue lives are plotted as a function of stress range. Here, the composite is far superior to the unreinforced matrix because of the additional load-carrying capacity of the fibers.

Source record↗
NASA NTRS1998

Noncontact Determination of Antisymmetric Plate Wave Velocity in Ceramic Matrix Composites

High-temperature materials are of increasing importance in the development of more efficient engines and components for the aeronautics industry. In particular, ceramic matrix composite (CMC) and metal matrix composite (MMC) structures are under active development for these applications. The acousto-ultrasonic (AU) method has been shown to be useful for assessing mechanical properties in composite structures. In particular, plate wave analysis can characterize composites in terms of their stiffness moduli. It is desirable to monitor changes in mechanical properties that occur during thermomechanical testing and to monitor the health of components whose geometry or position make them hard to reach with conventional ultrasonic probes. In such applications, it would be useful to apply AU without coupling directly to the test surface. For a number of years, lasers have been under investigation as remote ultrasonic input sources and ultrasound detectors. The use of an ultrasonic transducer coupled through an air gap has also been under study. So far at the NASA Lewis Research Center, we have been more successful in using lasers as ultrasonic sources than as output devices. On the other hand, we have been more successful in using an air-coupled piezoelectric transducer as an output device than as an input device. For this reason, we studied the laser in/air-coupled-transducer out combination-using a pulsed NdYAG laser as the ultrasonic source and an air-coupled-transducer as the detector. The present work is focused on one of the AU parameters of interest, the ultrasonic velocity of the antisymmetric plate-wave mode. This easily identified antisymmetric pulse can be used to determine shear and flexure modulus. It was chosen for this initial work because the pulse arrival times are likely to be the most precise. The following schematic illustrates our experimental arrangement for using laser in/air-transducer out on SiC/SiC composite tensile specimens. The NdYAG pulse was directed downward by a 90 infrared prism to the top of the specimen, but at the edge of one end. An energy sensor measured a single pulse at 13 millijoules (mJ) before it passed through the prism, which attenuated 15 percent of its energy. It also provided an output trigger for the waveform time-delay synthesizer.

Kautz, Harold E.↗
NASA NTRS1993

Hierarchical Simulation of Hot Composite Structures

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.

Chamis, C. C.↗
NASA NTRS1993

Hierarchical nonlinear behavior of hot composite structures

Hierarchical computational procedures are described to simulate the multiple scale thermal/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 METCAN (Metal Matrix Composite Analyzer), (2) tailoring of HT-MMC behavior for optimum specific performance via MMLT (Metal Matrix Laminate Tailoring), and (3) HT-MMC structural response for hot structural components via HITCAN (High Temperature Composite Analyzer). Representative results from each area are presented to illustrate the effectiveness of computational simulation procedures and accompanying computer codes. The sample case results show that METCAN can be used to simulate material behavior such as the entire creep span; MMLT can be used to concurrently tailor the fabrication process and the interphase layer for optimum performance such as minimum residual stresses; and HITCAN can be used to predict the structural behavior such as the deformed shape due to component fabrication. These codes constitute virtual portable desk-top test laboratories for characterizing HT-MMC laminates, tailoring the fabrication process, and qualifying structural components made from them.

Murthy, P. L. N.↗
NASA NTRS1991

Combined thermal and bending fatigue of high-temperature metal-matrix composites: Computational simulation

The nonlinear behavior of a high-temperature metal-matrix composite (HT-MMC) was simulated by using the metal matrix composite analyzer (METCAN) computer code. The simulation started with the fabrication process, proceeded to thermomechanical cyclic loading, and ended with the application of a monotonic load. Classical laminate theory and composite micromechanics and macromechanics are used in METCAN, along with a multifactor interaction model for the constituents behavior. The simulation of the stress-strain behavior from the macromechanical and the micromechanical points of view, as well as the initiation and final failure of the constituents and the plies in the composite, were examined in detail. It was shown that, when the fibers and the matrix were perfectly bonded, the fracture started in the matrix and then propagated with increasing load to the fibers. After the fibers fractured, the composite lost its capacity to carry additional load and fractured.

Gotsis, Pascal K.↗
NASA NTRS1992

Combined bending and thermal fatigue of high-temperature metal-matrix composites - Computational simulation

The nonlinear behavior of a high-temperature metal-matrix composite (HT-MMC) was simulated by using the metal matrix composite analyzer (METCAN) computer code. The simulation started with the fabrication process, proceeded to thermomechanical cyclic loading, and ended with the application of a monotonic load. Classical laminate theory and composite micromechanics and macromechanics are used in METCAN, along with a multifactor interaction model for the constituents behavior. The simulation of the stress-strain behavior from the macromechanical and the micromechanical points of view, as well as the initiation and final failure of the constituents and the plies in the composite, were examined in detail. It was shown that, when the fibers and the matrix were perfectly bonded, the fracture started in the matrix and then propagated with increasing load to the fibers. After the fibers fractured, the composite lost its capacity to carry additional load and fractured.

Gotsis, Pascal K.↗
NASA NTRS1994

Process/composite concurrent tailoring of SiC/Ti composites

Recent work on the prediction of optimal processing and material characteristics for improved fatigue behavior of metal and intermetallic matrix composites (MMC's/IMC's) is summarized. The method is incorporated into the MMLT (Metal Matrix Laminate Tailoring) code. Excellent correlations between predictions for the isothermal fatigue life of the SCS-6/Ti-24Al-11Nb composite and experimental data are obtained at various temperatures and stress ranges. Finally, the optimal processing conditions for improved isothermal fatigue life of the composite are evaluated and the attained isothermal fatigue life improvements are shown.

Chamis, C. C.↗
DOE OSTI2022

A boundary-based approach to the multiscale microstructural characterization of a W-Ni-Fe tungsten heavy alloy

Here, a combination electron backscattered diffraction and transmission electron microscopy based approach has been implemented to study the effects of purposefully introduced anisotropy in a tungsten heavy alloy (WHA) through hot-rolling. Particular attention has been paid to changes in number and proportion of various boundary types from a quantitative standpoint; incorporating qualitative behavioral observations from prior analyses to generate experimentally-validated bases for the examination and application of a microstructure which exhibits an optimal balance of strength and ductility. It is asserted that a combination of increased temperatures during rolling and additional isothermal hold time for the post-rolling annealing steps may lead to a reduction in unfavorable textural components due to rolling in the W-phase and a decrease in premature fracture due to W-W microcracking respectively. This is expected to further increase the proportion of interphase boundaries and improve the ductility of these rolled structures, producing a superior rolled WHA microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Copper-Tantalum Metal Matrix Composites Consolidated from Powder Blends by Severe Plastic Deformation

We investigated the effectiveness of severe plastic deformation by equal channel angular extrusion (ECAE) for consolidation of metal powders into metal matrix composites. Equal volumes of copper (Cu) and tantalum (Ta) powders were consolidated at ambient temperature via different ECAE routes. Composites processed by ECAE routes 4E and 4Bc were also processed at 300 °C. The resulting materials were characterized by scanning electron microscopy (SEM) and compression testing. Processing by route 4Bc at 300 °C resulted in the highest compressive strength, lowest anisotropy, and least strain rate sensitivity. We conclude that the superior properties achieved by this route arise from mechanical bonding due to interlocking Cu and Ta phases as well as enhanced metallurgical bonds from contact of pristine metal surfaces when the material is sheared along orthogonal planes.

36 MATERIALS SCIENCE↗
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 NTRS1991

Computational simulation of high temperature metal matrix composite behavior

Computational procedures are described to simulate the thermal and mechanical behavior of high temperature metal matrix composite (HT MMC) in the following four broad areas: (1) behavior of HT MMC from micromechanics to laminate; (2) HT MMC structural response for simple and complex structural components; (3) HT MMC microfracture; and (4) tailoring of HT MMC behavior for optimum specific performance. Representative results from each area are presented to illustrate the effectiveness of the computational simulation procedures. Relevant reports are referenced for extended discussion regarding the specific area.

Murthy, Pappu L. N.↗
NASA NTRSDate not supplied

Metallic Powder Core Tubular Wire Development for Additive Manufacturing

NASA Langley Research Center (LaRC) in Hampton, VA, and the Center for Welding, Joining, and Coating Research (CWJCR) in the Department of Metallurgical and Materials Engineering at the Colorado School of Mines (CSM) in Golden, CO, have collaborated for nearly fifteen years to develop metallic powder core tubular wire (PCTW) feedstock for additive manufacturing (AM) using electron beam deposition. The motivation for this development was to offset dealloying observed during deposition of titanium and aluminum alloy solid wire feedstock in the LaRC electron beam freeform fabrication (EBF3) system and to explore novel alloy compositions by tailoring the powder fill. EBF3 is a fusion-based AM process that is performed under vacuum and is consequently prone to vaporization loss of low vapor pressure alloying elements. Research spanning four graduate student research projects succeeded in developing the basic methodology to fabricate PCTW, the mass balance equations used to define the powder fill, microstructure control through particulate inoculation, and the feasibility of producing metal matrix composite materials.

powder core tubular wire (PCTW)↗