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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

700 F properties of autoclave cured PMR-II composites

Studies were conducted to develop autoclave processing parameters for graphite reinforced PMR-2 resin composite materials intended for use in applications at temperatures up to 371 degrees (700 F). The effect of resin composition on autoclaveability was investigated. The effect of various graphite fibers and resin composition on 343 C (650 F) and 371 C (700 F) thermo-oxidative stability and mechanical properties was also investigated. The results of the processing studies show that PMR-2 resin composites can be easily fabricated under autoclave conditions. Autoclaved laminates exposed to 1 atm of air at 343 C (650 F) and 371 C (700 F) exhibited less than 5 percent weight loss after 750 hr exposure to 650 F air and 8 percent weight loss during exposure to 700 F air for 500 hr. After 500 hr exposure, autoclaved laminates exhibited greater than 90 percent retention of initial 650 and 700 F flexural and interlaminar shear strengths. The effect of resin formulated molecular weight and postcure conditions on laminate glass transition temperature is also discussed.

Cifani, Diane↗
NASA NTRS1988

The acousto-ultrasonic approach

The nature and underlying rationale of the acousto-ultrasonic approach is reviewed, needed advanced signal analysis and evaluation methods suggested, and application potentials discussed. Acousto-ultrasonics is an NDE technique combining aspects of acoustic emission methodology with ultrasonic simulation of stress waves. This approach uses analysis of simulated stress waves for detecting and mapping variations of mechanical properties. Unlike most NDE, acousto-ultrasonics is less concerned with flaw detection than with the assessment of the collective effects of various flaws and material anomalies. Acousto-ultrasonics has been applied chiefly to laminated and filament-wound fiber reinforced composites. It has been used to assess the significant strength and toughness reducing effects that can be wrought by combinations of essentially minor flaws and diffuse flaw populations. Acousto-ultrasonics assesses integrated defect states and the resultant variations in properties such as tensile, shear, and flexural strengths and fracture resistance. Matrix cure state, porosity, fiber orientation, fiber volume fraction, fiber-matrix bonding, and interlaminar bond quality are underlying factors.

Vary, Alex↗
DOE OSTI2022

Multiple Stream Low-Cost Recycling Method

The global composite industry generates large quantities of waste and which mostly end as landfill due to lack of meaningful end-use applications for the multiple waste streams. In a recent report by the Electric Power Research Institute (EPRI), waste generated by the wind industry could reach 370,000 tons a year of composite wind energy blades being decommissioned and scrapped. Wind energy is just one major industry utilizing composite materials. The waste generated by industry includes End-of-Life (EoL) materials and manufacturing process scrap. GreenTex Solutions has developed a unique and innovative technology to recycle the composite waste streams in a range of forms made from production waste and EoL materials. This includes manufacturing waste materials such as dry chopped fiber tow, loose fibers, shredded fibers from reinforcement fabrics, cured/semi-cured prepregs, and it also includes fully-cured composite structure waste (such as edge trims from cured parts) from manufacturing aircraft, automobiles, wind blades, boats, and composite cylinders (tanks). Current recycling methods involve recovering the structural fiber by removing the matrix resin through methods such as pyrolysis. The resulting fibers are used in injection molding or wet laid nonwoven mats and other usable forms. The GreenTex technology bypasses these intermediate steps to create the lowest possible recycling processing costs and the lowest embodied energy/CO2 emissions. The end-product from the GreenTex technology is a finished industrial composite part/application versus intermediate fibers or fabrics. The GreenTex manufacturing process enables cross-industry reuse of recycled feedstock by taking waste from multiple industries (wind energy, aerospace, marine, etc.) and recycles the waste into a product used in other industries. The initial target market application is structural flooring for intermodal shipping containers and truck bodies. One of the team’s key partners is Wabash National which produced 29,000 truck bodies in 2019. The current flooring system is comprised of solid oak “butcher board” laminated panels. Additionally, Mediterranean Shipping Containers (MSC) transports over 1.8 million twenty-foot equivalent units per year in intermodal shipping containers. The current container floor is laminated hardwood that is harvested from the rain forests of Central and South America. The project is to develop a flooring system made from recycled composites that can be qualified for both companies (Wabash and MSC). Initial prototypes validated that the recycled composites panels are lighter and thinner with much higher mechanical strength. These results suggest a typical truck trailer would have 20% lower tare weight. The GreenTex technology is not limited to flooring and is widely applicable to other transportation elements such as walls, roof elements, cab areas and related structural components. Under this project different composite waste streams were evaluated and then combined to develop a formulation that would meet the targeted performance criteria for a flooring system. Wet compression molding was used to fabricate plaques at different tonnage using various composite waste streams. The plaques were tested for flexure and impact.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Recycled Glass Polypropylene Composites from Transportation Manufacturing Waste

In recent years there has been growing interest in developing recycling technologies for composites manufacturing scrap, process waste and end-of-life parts. The focus of this work was to establish processing routes and mechanical property bounds for glass-polypropylene (PP-GF) scrap from the production of parts for truck trailers, automobiles, and rail cars. This study considered PP-GF scrap and demonstrated extrusion-compression molding (ECM) as a viable route for the closed-loop manufacture of composite parts. The results were promising in terms of the strength and modulus retention of the PP-GF recyclate. The tensile strength and modulus was the highest for 50% and 66% recycled content, compared with 100% and 83% recycle content. The flexural strength and modulus of the 100% and 83% recycled compositions was higher than the 66% and 50% recycled content, respectively. The impact energy absorption of the PP-GF recyclate at at all fiber loadings was superior in absorbing energy compared with the incumbent (benchmark) plywood. This work is useful to designers seeking to incorporate recycled materials in their products.

Vaidya, Uday↗
NASA NTRS1980

High Temperature Resin Matrix Composites for Aerospace Structures

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.

Davis, J. G., Jr.↗
NASA NTRS1992

Mechanical energy flow models of rods and beams

It has been proposed that the flow of mechanical energy through a structural/acoustic system may be modeled in a manner similar to that of flow of thermal energy/in a heat conduction problem. If this hypothesis is true, it would result in relatively efficient numerical models of structure-borne energy in large built-up structures. Fewer parameters are required to approximate the energy solution than are required to model the characteristic wave behavior of structural vibration by using traditional displacement formulations. The energy flow hypothesis is tested in this investigation for both longitudinal vibration in rods and transverse flexural vibrations of beams. The rod is shown to behave approximately according to the thermal energy flow analogy. However, the beam solutions behave significantly differently than predicted by the thermal analogy unless locally-space-averaged energy and power are considered. Several techniques for coupling dissimilar rods and beams are also discussed. Illustrations of the solution accuracy of the methods are included.

Wohlever, J. C.↗
DOE OSTI2021

MXene Reinforced Thermosetting Composite for Lightning Strike Protection of Carbon Fiber Reinforced Polymer

Ti 3 C 2 – a member of the MXenes (2D transition metal carbides and nitrides) family, is investigated as an effective filler to improve the electrical, mechanical, and thermal properties of divinylbenzene (DVB) thermosetting resin. Consequently, its performance as a lightning strike protection (LSP) coating for carbon fiber reinforced polymer (CFRP) is evaluated. Polyaniline (PANI) – dodecylbenzene sulfonic acid (DBSA) complex is used to cure the DVB resin. The synergic effect of MXenes (with surface that is negatively charged) with polyaniline (positive charge) shows electrostatic bonding and improved electrical conductivity in the composite. We also find that the addition of MXenes at 2 wt% into the PANI-DVB composite shows ≈139%, 10%, and 9% improvement in electrical conductivity, flexural strength, and flexural modulus, respectively, compared to the neat PANI-DVB composite. The composites are investigated using various material characterization techniques including Fourier transforms infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Furthermore, MXenes-DVB is utilized to create a conductive thermosetting coating on top of a CFRP substrate and tested against a lightning strike of 100 kA. CFRP with MXenes-DVB coating reduced the surface damage from 40.61 cm 2 (reference CFRP panel) to 13.29 cm 2 (CFRP coated with MXenes-DVB).

36 MATERIALS SCIENCE↗
NASA NTRS1990

An experimental study of compression failure of fibrous laminated composites in the presence of stress gradients

Mechanisms of failure in laminates in the presence of a stress raiser were experimentally studied. The damage initiation and propagation throughout the entire load history were examined via real-time holographic interferometry and photomicrography of the hole surface. Multilayered composite flat plates made of T300/BP907 and IM7/8551-7 were tested. It is shown that the failure is initiated as a localized instability in the 0-deg plies at the hole surface approximately at right angles to the loading direction. A series of events is described which culminates in the complete loss of flexural stiffness of each of the delaminated portions, leading to catastrophic failure of the plate.

Waas, A. M.↗
NASA NTRS1998

Waveform Analysis of AE in Composites

Advanced, waveform based acoustic emission (AE) techniques have been developed to evaluate damage mechanisms in the testing of composite materials. This approach, more recently referred to as Modal AE, provides an enhanced capability to discriminate and eliminate noise signals from those generated by damage mechanisms. Much more precise source location can also be obtained in comparison to conventional, threshold crossing arrival time determination techniques. Two successful examples of the application of Modal AE are presented in this work. In the first, the initiation of transverse matrix cracking in cross-ply, tensile coupons was monitored. In these tests, it was documented that the same source mechanism, matrix cracking, can produce widely different AE signal amplitudes dependent on laminate stacking sequence and thickness. These results, taken together with well known propagation effects of attenuation and dispersion of AE signals in composite laminates, cast further doubt on the validity of simple amplitude or amplitude distribution analysis for AE source determination. For the second example, delamination propagation in composite ring specimens was monitored. Pressurization of these composite rings is used to simulate the stresses in a composite rocket motor case. AE signals from delamination propagation were characterized by large amplitude flexural plate mode components which have long signal durations because of the large dispersion of this mode.

Prosser, William H.↗
DOE OSTI2026

Effect of fiber sizing and glass fiber laminate hybridization on vibration damping and mechanical properties of banana fiber reinforced polypropylene composites

Modern automotive applications demand lightweight, multifunctional materials to reach mileage goals and natural fiber reinforced composites (NFRCs) are one of the classes of materials proposed as a solution. NFRCs exhibit good vibration damping properties and have low density, but are often limited by processing challenges, poor-fiber matrix compatibility and variable performance. Herein, we investigate non-woven wet-lay of comingled banana fiber (BF), recycled glass fiber (rGF), and polypropylene (PP) fibers to in situ sizing and preparation of composite feedstocks for compression molding. BF and rGF hybrids were prepared by stacking rGF layers during compression molding to produce composites with various fiber ratios. The effect of fiber content, in-situ sizing and ratio of BF to rGF on tensile, flexural and vibration damping performance are investigated. Key results are the significant increase in tensile strength by in situ sizing (40 % sized at 60 wt% BF) and in flexural modulus (+58 % sized at 60 wt% BF) and flexural strength (+41 % sized 60 wt% BF) compared to the unsized equivalent. For BF-rGF hybrid composites with40 wt% total fiber content, flexural strength and modulus were improved by 51 % and 231 % respectively for a 1:1 ratio BF:rGF compared to BF reinforced system. Lastly, identifying the cross-over point where damping and stiffness are optimized for a hybrid composite. These findings demonstrate that these composites can be used as alternative to synthetic fiber or mineral filled composites in automotive applications, particularly where weight reduction, vibration damping and stiffness are desired.

Banana fiber↗
DOE OSTI2021

In situ observation of the deformation and fracture of an alumina-alumina ceramic-matrix composite at elevated temperature using x-ray computed tomography

The deformation and fracture of a 0/90° Nextel 720 mullite fibre / alumina matrix ceramic-matrix composite material has been observed by in situ synchrotron x-ray computed micro-tomography at ambient temperature and at 1100 °C. A three-point loading configuration was used and samples were loaded monotonically until final fracture. Here, the flexural strength was found to be unaffected by temperature. 3D visualisation of the microstructure showed fracture occurred by propagation of internal cracks at stresses close to the flexural strength. Shear fractures propagated across fibre bundles that were oriented perpendicular to the flexural stress at both room temperature and 1100 °C. At the higher temperature, an additional failure mode of delamination was observed, that may arise from relaxation of thermal residual stresses and creep.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Evaluation of some scale effects in the response and failure of composite beams

The feasibility of using scale model testing for predicting full-scale behavior of composite beams loaded in tension and flexure was investigated. Classical laws of similitude were applied to fabricate and test replica model beams to identify scaling effects in the load response, strength, and mode of failure. Experiments were conducted using graphite-epoxy composite beams having different laminate stacking sequences and a range of scaled sizes. Results indicated that the elastic response of scaled composite beams was independent of specimen size. However, a significant scale effect in strength was observed. In addition, a transition in failure mode was observed among scaled beams of certain laminate stacking sequences. Weibull statistical and fracture mechanics based models were applied to predict the strength scale effect since standard failure criteria cannot account for the influence of absolute specimen size in failure.

Jackson, Karen E.↗
DOE OSTI2025

Extremely Durable Concrete using Methane Decarbonization Nanofiber Co-products with Hydrogen

This project successfully developed a scalable, low-cost co-production process for hydrogen (H₂) and carbon nanofibers (CNFs) using methane through catalytic chemical vapor deposition (CVD). CNFs are high-value materials with exceptional mechanical, electrical, and chemical properties, while hydrogen is a critical clean energy resource. By leveraging vapor deposition to create highly dispersed metal catalysts, this work addressed the dual challenge of producing low-cost hydrogen and enhancing the durability of concrete using co-produced CNFs. Unlike prior approaches, which required separating the carbon product from the catalyst, this innovative method integrated the carbon product, catalyst, and silica support as a crack-bridging additive for Portland cement. This novel application aimed to advance the performance of high-performance concrete (HPC) by improving its flexural toughness, durability, and resistance to environmental degradation.

08 HYDROGEN↗
NASA NTRS2015

Actuators Using Piezoelectric Stacks and Displacement Enhancers

Actuators are used to drive all active mechanisms including machines, robots, and manipulators to name a few. The actuators are responsible for moving, manipulating, displacing, pushing and executing any action that is needed by the mechanism. There are many types and principles of actuation that are responsible for these movements ranging from electromagnetic, electroactive, thermo-mechanic, piezoelectric, electrostrictive etc. Actuators are readily available from commercial producers but there is a great need for reducing their size, increasing their efficiency and reducing their weight. Studies at JPL’s Non Destructive Evaluation and Advanced Actuators (NDEAA) Laboratory have been focused on the use of piezoelectric stacks and novel designs taking advantage of piezoelectric’s potential to provide high torque/force density actuation and high electromechanical conversion efficiency. The actuators/motors that have been developed and reviewed in this paper are operated by various horn configurations as well as the use of pre-stress flexures that make them thermally stable and increases their coupling efficiency. The use of monolithic designs that pre-stress the piezoelectric stack eliminates the use of compression stress bolt. These designs enable the embedding of developed solid-state motors/actuators in any structure with the only macroscopically moving parts are the rotor or the linear translator. Finite element modeling and design tools were used to determine the requirements and operation parameters and the results were used to simulate, design and fabricate novel actuators/motors. The developed actuators and performance will be described and discussed in this paper.

rotary devices↗
NASA NTRS2004

Programmable 2-D Addressable Cryogenic Aperture Masks

We are developing a two-dimensional array of square microshutters (programmable aperture mask) for a multi-object spectrometer for the James Webb Space Telescope (JWST). This device will provide random access selection of the areas in the field to be studied. The device is in essence a close packed array of square slits, each of which can be opened independently to select areas of the sky for detailed study.The device is produced using a 100-micron thick silicon wafer as a substrate with 0.5-micron thick silicon nitride shutters on top of it. Silicon nitride has been selected as the blade and flexure material because its stiffness allows thinner and lighter structures than single crystal Si, the chief alternative, and because of its ease of manufacture. The 100 micron silicon wafer is backetched in a high aspect ratio Deep Reactive Ion Etching (Deep RIE) to leave only a support grid for the shutters and the address electronics. The shutter actuation is done magnetically whereas addressing is electrostatic. 128x128 format microshutter arrays have been produced. Their operation has been demostarted on 32x32 subarrays. Good reliability of the fabrication process and good quality of the microshutters has been achieved. The mechanical behavior and optical performance of the fabricated arrays at cryogenic temperature are being studied.

Kutyrev, A. S.↗
DOE OSTI2026

Why Firn Quakes

Snow dampens sounds, but anecdotal reports concisely describe audible propagating collapse events—firnquakes—in Antarctic and Arctic snowfields. We propose combining granular and continuum mechanics to form a testable theory for conditioning, triggering, and propagation of firnquakes consistent with scarce data. A central condition for collapse events is unconsolidated firn at depth. As firn grains compact, stresses are transmitted along force chains which carry the overburden and transition into a continuous medium by pressure sintering. This granular legacy creates solid-like supports of denser layers that keep the material below unconsolidated. Dynamic amplification triggers local brittle failure of the supports, which induces a cascade of collapse propagation. Using bulk density from ice cores as proxy for stiffness, we find the flexural wave speed by collapsing supports matches the recorded firnquake velocities on the order of 100 m/s. Our theory is to be tested in firn sheets and other compacting granular materials.

Voigtländer, A. [Lawrence Berkeley National Labora↗
NASA NTRS1982

Ultrasonic and mechanical characterizations of fatigue states of graphite epoxy composite laminates

Results of an exploration of the relationship between ultrasonic attenuation and fatigue survivability of graphite fiber epoxy composites fabricated under different cure conditions are reported. A total of 9 27 x 40 cm eight-ply graphite epoxy laminated specimens were formed, and fatigue tests were run on five partial samples at 73.5 N varying at 30 Hz, with tests ending at a 1.27 cm deflection. A pulsed oscillator generated sinusoidal waves and transducers recorded the passage of the ultrasonic waves for display on oscilloscopes. Cure pressures ranged from 0.52-0.85 MPa and cure temperatures were in the 150-200 C interval. Ultrasonic through-transmission at 4 MHz was performed prior to and during fatigue testing. The minimum void volume fraction occurred at 175 C and 0.86 MPa. The flexural stiffness decreased with the number of fatigue cycles past 10,000, when the attenuation also increased. Correlations were found between the 4.0 MHz signal attenuation and the void volume fraction, and between the number of fatigue cycles to failure and the 4.0 MHz signal attenuation.

Williams, J. H., Jr.↗
NASA NTRS1996

Development of Torsional and Linear Piezoelectrically Driven Motors

The development of rotary and linear inchworm-motors using piezoelectric actuators is presented. The motors' design has the advantage of a macro and micro stepper motor with high load and speed. The torsional design is capable of fast angular positioning with micro level accuracy. Additionally, the rotary motor, as designed, can be used as a clutch/brake mechanism. Constructed prototype motors of both types along with their characteristics are presented. The torsional motor consists of a torsional section that provides angular displacement and torque, and two alternating clamping sections which provide the holding force. The motor relies on the principal piezoelectric coupling coefficient (d33) with no torsional elements, increasing its torque capability. The linear motor consists of a longitudinal vibrator that provides displacement and load, and two alternating clamping sections which provide the holding force. This design eliminates bending moment, tension and shear applied to the actuator elements, increase its load capability and life. Innovative flexure designs have been introduced for both motor types. Critical issues that affect the design and performance of the motors are explored and discussed. Experiments are performed demonstrating the motor prototypes based on the aforementioned design considerations.

Duong, Khanh↗