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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Control of sound radiation with active/adaptive structures

Recent research is discussed in the area of active structural acoustic control with active/adaptive structures. Progress in the areas of structural acoustics, actuators, sensors, and control approaches is presented. Considerable effort has been given to the interaction of these areas with each other due to the coupled nature of the problem. A discussion is presented on actuators bonded to or embedded in the structure itself. The actuators discussed are piezoceramic actuators and shape memory alloy actuators. The sensors discussed are optical fiber sensors, Nitinol fiber sensors, piezoceramics, and polyvinylidene fluoride sensors. The active control techniques considered are state feedback control techniques and least mean square adaptive algorithms. Results presented show that significant progress has been made towards controlling structurally radiated noise by active/adaptive means applied directly to the structure.

Fuller, C. R.↗
NASA NTRS1992

Polymer matrix composites on LDEF experiments M0003-9 and M0003-10

Over 250 polymer matrix composites were exposed to the natural space environment on Long Duration Exposure Facility (LDEF) experiments M0003-9 and 10. The experiments included a wide variety of epoxy, thermoplastic, polyimide, and bismalimide matrix composites reinforced with graphite, glass, or organic fibers. A review of the significant observations and test results obtained to date is presented. Estimated recession depths from atomic oxygen exposure are reported and the resulting surface morphologies are discussed. The effects of the LDEF exposure on the flexural strength and modulus, short beam shear strength, and coefficient of thermal expansion of several classes of bare and coated composites are reviewed. Lap shear data are presented for composite-to-composite and composite-to-aluminum alloy samples that were prepared using different bonding techniques and subsequently flown on LDEF.

Steckel, Gary L.↗
NASA NTRS2002

Acoustic Emission and Damage Accumulation for Various Woven C/SiC Composites Tested in Tension at Room Temperature

Modal acoustic emission (AE) has proven to be an excellent technique to monitor damage accumulation in ceramic matrix composites. In this study, AE was used to monitor tensile load-unload-reload hysteresis tests for a variety of C fiber reinforced, SiC matrix composites. C/SiC composites were reinforced with T300 and IM7 fibers, had C, multilayer, or pseudo-porous C interphases, and had chemical vapor infiltrated SiC or melt-infiltrated SiC matrices. All of the composites exhibited considerable AE during testing. The extent and nature of the AE activity will be analyzed and discussed in light of matrix cracking and the variety of composite constituents. It is hoped that understanding the nature of stress dependent damage accumulation in these materials can be of use in life modeling for these types of composites.

Morscher, Gregory N.↗
NASA NTRS2002

Acoustic Emission and Damage Accumulation for Various Woven C/SiC Composites Tested in Tension at Room Temperature

Modal acoustic emission (AE) has proven to be an excellent technique to monitor damage accumulation in ceramic matrix composites. In this study, AE was used to monitor tensile load-unload-reload hysteresis tests for a variety of C fiber reinforced, Sic matrix composites. C/SiC composites were reinforced with T-300 and IM7 fibers, had C, multilayer, or pseudo-porous C interphases, and had chemical vapor infiltrated Sic or melt-infiltrated SiC matrices. All of the composites exhibited considerable AE during testing. The extent and nature of the AE activity will be analyzed and discussed in light of matrix cracking and the variety of composite constituents. It is hoped that understanding the nature of stress-dependent damage accumulation in these materials can be of use in life-modeling for these types of composites.

Morscher, Gregory↗
NASA NTRS1995

Multipurpose Prepregging Machine

Machine designed and built for variety of uses involving coating or impregnating ("prepregging") fibers, tows, yarns, or webs or tapes made of such fibrous materials with thermoplastic or thermosetting resins. Prepreg materials produced used to make matrix/fiber composite materials. Comprises modules operated individually, sequentially, or simultaneously, depending on nature of specific prepreg material and prepregging technique used. Machine incorporates number of safety features.

Johnston, N. J.↗
NASA NTRS2002

Efficient Nondestructive Evaluation of Prototype Carbon Fiber Reinforced Structures

Thermography inspection is an optic based technology that can reduce the time and cost required to inspect propellant tanks or aero structures fabricated from composite materials. Usually areas identified as suspect in the thermography inspection are examined with ultrasonic methods to better define depth, orientation and the nature of the anomaly. This combination of nondestructive evaluation techniques results in a rapid and comprehensive inspection of composite structures. Examples of application of this inspection philosophy to prototype will be presented. Methods organizing the inspection and evaluating the results will be considered.

Russell, Samuel S.↗
NASA NTRS2013

3D Guided Wave Motion Analysis on Laminated Composites

Ultrasonic guided waves have proved useful for structural health monitoring (SHM) and nondestructive evaluation (NDE) due to their ability to propagate long distances with less energy loss compared to bulk waves and due to their sensitivity to small defects in the structure. Analysis of actively transmitted ultrasonic signals has long been used to detect and assess damage. However, there remain many challenging tasks for guided wave based SHM due to the complexity involved with propagating guided waves, especially in the case of composite materials. The multimodal nature of the ultrasonic guided waves complicates the related damage analysis. This paper presents results from parallel 3D elastodynamic finite integration technique (EFIT) simulations used to acquire 3D wave motion in the subject laminated carbon fiber reinforced polymer composites. The acquired 3D wave motion is then analyzed by frequency-wavenumber analysis to study the wave propagation and interaction in the composite laminate. The frequency-wavenumber analysis enables the study of individual modes and visualization of mode conversion. Delamination damage has been incorporated into the EFIT model to generate "damaged" data. The potential for damage detection in laminated composites is discussed in the end.

Tian, Zhenhua↗
NASA NTRS1983

Etching of moldavities under natural conditions

The hypothesis that a part of the lechatellierites which originated by etching from a basic moldavite mass became broken off after deposition of moldavite in the sedimentation layer is advanced. Those found close to the original moldavite were measured for statistical averaging of length. The average length of lechatelierite fibers per cubic mm of moldavite mass volume was determined by measurement under a microscope in toluene. The data were used to calculate the depth of the moldavite layer that had to be etched to produce the corresponding amount of lechatelierite fragments. The calculations from five "fields" of moldavite surface, where layers of fixed lechatelierite fragments were preserved, produced values of 2.0, 3.1, 3.5, 3.9 and 4.5. Due to inadvertent loss of some fragments the determined values are somewhat lower than those found in references. The difference may be explained by the fact that the depth of the layer is only that caused by etching after moldavite deposition.

Knobloch, V.↗
NASA NTRS1987

In situ deposits of copper and copper oxide containing condensation polyimide films

Novel copper-polyimide composites have been synthesized via simultaneous thermal decomposition of solid solutions of bis (trifluoroacetylacetonato) copper (II) and thermal cyclodehydration of polyimide acid. In contrast to conventional filled polymer composites which are prepared by dispersion of particles or fibers in a polymer matrix this study has yielded in general uniform Cu or CuO dispersions of very small particle size that reside near the film surface that was exposed to the atmosphere during curing. The nature of the copper deposit, the thickness of the copper deposit, and the polyimide overlayer which bonds the copper to the polymer substrate depend on the curing atmosphere used. A variety of analytical surface methods along with thermogravimetric analysis and variable temperature (surface and volume) electrical resistivity measurements have been used to characterize these thin, flexible copper doped polyimide films.

Porta, G. M.↗
NASA NTRS1990

Surface-crack growth: Models, experiments, and structures; Proceedings of the Symposium, Sparks, NV, Apr. 25, 1988

The present volume on surface-crack growth modeling, experimental methods, and structures, discusses elastoplastic behavior, the fracture analysis of three-dimensional bodies with surface cracks, optical measurements of free-surface effects on natural surfaces and through cracks, an optical and finite-element investigation of a plastically deformed surface flaw under tension, fracture behavior prediction for rapidly loaded surface-cracked specimens, and surface cracks in thick laminated fiber composite plates. Also discussed are a novel study procedure for crack initiation and growth in thermal fatigue testing, the growth of surface cracks under fatigue and monotonically increasing load, the subcritical growth of a surface flaw, surface crack propagation in notched and unnotched rods, and theoretical and experimental analyses of surface cracks in weldments.

Reuter, Walter G.↗
NASA NTRS1991

A statistical model of carbon/carbon composite failure

A failure model which considers the stochastic nature of the damage accumulation process is essential to assess reliability and to accurately scale the results from standard test specimens to composite structures. A superior filamentary composite for high temperature applications is composed of carbon fibers in a carbon matrix. Carbon-carbon composites are the strongest known material at very high temperatures. Since there appears to be a significant randomness in C-C material strength which cannot be controlled or detected with current technology, a better model of the material failure based upon statistical principles should be used. Simple applications of the model based upon the limited data provide encouraging results that indicate that better design of test specimens would provide a substantially higher prediction for the design strength of C-C composites. An A-basis strength for the C-C tensile rings from a first stage D-5 billets was estimated. A statistical failure model was developed for these rings which indicates that this strength may be very conservative for larger C-C parts. The analysis may be improved by use of a heterogeneous/noncontinuum finite element approach on the minimechanical level.

Slattery, Kerry T.↗
NASA NTRS1975

The use of Whatman-41 filters for high volume air sampling

The feasibility of using W41 filter media on a routine TSP high-volume monitoring network was determined by comparison with glass fiber (GF) filtering. Results indicate that suspended particulate samples from GF filters averaged slightly, but not significantly, higher than those from Whatman-41 filters. Some extra handling procedures were required to avoid errors due to the hygroscopic nature of W41 filters; these added procedures are not overly burdensome, however, and they allow the performance of analytical work, thus extending the capabilities of high-volume sampling. It was demonstrated that W41 filters are practical for air quality monitoring and elemental analysis in environments similar to Cleveland's.

Neustadter, H. E.↗
NASA NTRS1990

Initial evaluation of commercially available InGaAsP DFB laser diodes for use in high-speed digital fiber optic transceivers

NASA has been pursuing the development of high-speed fiber-optic transceivers for use in a number of space data system applications. Current efforts are directed toward a high-performance all-integrated-circuit transceiver operating up to the 3-5 Gb/s range. Details of the evaluation and selection of candidate high-speed optical sources to be used in the space-qualified high-performance transceiver are presented. Data on the performance of commercially available DFB (distributed feedback) lasers are presented, and their performance relative to each other and to their structural design with regard to their use in high-performance fiber-optic transceivers is discussed. The DFB lasers were obtained from seven commercial manufacturers. The data taken on each laser included threshold current, differential quantum efficiency, CW side mode suppression radio, wavelength temperature coefficient, threshold temperature coefficient, natural linewidth, and far field pattern. It was found that laser diodes with buried heterostructures and first-order gratings had, in general, the best CW operating characteristics. The modulated characteristics of the DFB laser diodes are emphasized. Modulated linewidth, modulated side mode suppression ratio, and frequency response are discussed.

Cook, Anthony L.↗
NASA NTRS2019

Effect of Processing on Morphology of Hydroxyapatites: Bioactive Glasses and Crystalline Composites

Recent studies on multinary oxides for applications as laser hosts and high dielectric capacitors have shown that processing at high temperature provides glassy or crystalline materials based on thermal treatments and cooling rates. Since hydroxyapatites are now subject of great interests due to their bioactivity, interest in producing soft and hard materials with glassy and crystalline nature by processing parameters has become very important. Crystalline materials by using Bridgman, Czochralski and flux growth methods are costly and require huge investment. We have observed that even low temperature solidification in organic flux produced oriented fibers. This organic treated material has different characteristics than in situ oxide materials prepared by sintering and grain growth. Examples of phosphate and silicate-based systems will be presented to demonstrate soft and hard materials. Effect of TiO2 and other hardening elements will be also reported.

McAdams, Joel↗
NASA NTRS2003

Status on Technology Development of Optic Fiber-Coupled Laser Ignition System for Rocket Engine Applications

To pursue technology developments for future launch vehicles, NASA/Marshall Space Flight Center (MSFC) is examining vortex chamber concepts for liquid rocket engine applications. Past studies indicated that the vortex chamber schemes potentially have a number of advantages over conventional chamber methods. Due to the nature of the vortex flow, relatively cooler propellant streams tend to flow along the chamber wall. Hence, the thruster chamber can be operated without the need of any cooling techniques. This vortex flow also creates strong turbulence, which promotes the propellant mixing process. Consequently, the subject chamber concept: not only offer system simplicity, but also enhance the combustion performance. Test results have shown that chamber performance is markedly high even at a low chamber length-to-diameter ratio. This incentive can be translated to a convenience in the thrust chamber packaging.

Trinh, Huu P.↗
NASA NTRS1985

Investigation of the effects of NaOH dopant level on the physical and mechanical properties of carbon/phenolic composite material

The near-catastrophic erosion of the STS-8A solid rocket booster nozzle was the instigating factor in the recent, and on-going, intensive investigation of carbon/phenolic composite materials. Much of this effort has been focused on the effect of sodium contamination on the carbon fibers. It is known that sodium acts as a catalyst in the oxidation of the fibers at elevated temperatures. A study was undertaken to determine what changes were caused by variation in sodium content. Investigations were conducted in three areas: (1) phenolic resin; (2) carbon/phenolic prepreg; and (3) cured laminates. Due to the exploratory nature of the studies, a variety of tests in addition to those normally run in production facilities were considered. The experimental methodologies and results of these experiments are discussed, and recommendations for improving techniques and extending the research program are presented.

Clinton, R. G., Jr.↗
NASA NTRS1995

A study of the relationship between mineral content and mechanical properties of turkey gastrocnemius tendon

The vertebrate skeletal system undergoes adaptation in response to external forces, but the relation between the skeletal changes and such forces is not understood. In this context, the variation in the amount and location of calcification has been compared with changes in mechanical properties of the normally mineralizing turkey gastrocnemius tendon using ash weight measurements, X-ray radiography, and mechanical testing. Radiographic evidence from 12- to 17-week-old birds showed calcification in only portions of gastrocnemius tendons proximal to the tarsometatarsal joint. Mechanical testing of these dissected proximal regions demonstrated an increased ultimate stress and modulus and a decreased maximum strain that appeared to parallel calcification. Further, stress-strain curves of portions of uncalcified turkey gastrocnemius tendon were shaped similar to those of other typical unmineralized tendon curves while highly calcified tendons yielded curves resembling those of bone. The proximal portions of the gastrocnemius where mineralization begins were observed to have a decreased tendon cross-sectional area compared with distal portions which do not mineralize. Based on the resultant measures of mineral content and location and mechanical properties, it is hypothesized that increased calcification is a result of increased stresses at certain locations of the tendon, perhaps the consequence of the natural forces exerted by the large leg muscles of the bird into which the gastrocnemius inserts. More specifically, tendon calcification may be the result of stress-induced exposure of charged sites on the surfaces of collagen molecules, fibrils, or fibers so that deposition of mineral and subsequent mechanical reinforcement occur in the tissue.(ABSTRACT TRUNCATED AT 250 WORDS).

Non-NASA Center↗
NASA NTRS1991

NDE of ceramics and ceramic composites

Although nondestructive evaluation (NDE) techniques for ceramics are fairly well developed, they are difficult to apply in many cases for high probability detection of the minute flaws that can cause failure in monolithic ceramics. Conventional NDE techniques are available for monolithic and fiber reinforced ceramic matrix composites, but more exact quantitative techniques needed are still being investigated and developed. Needs range from flaw detection to below 100 micron levels in monolithic ceramics to global imaging of fiber architecture and matrix densification anomalies in ceramic composites. NDE techniques that will ultimately be applicable to production and quality control of ceramic structures are still emerging from the lab. Needs are different depending on the processing stage, fabrication method, and nature of the finished product. NDE techniques are being developed in concert with materials processing research where they can provide feedback information to processing development and quality improvement. NDE techniques also serve as research tools for materials characterization and for understanding failure processes, e.g., during thermomechanical testing.

Vary, Alex↗