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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 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Comparative Analysis of the Effects of Severe Plastic Deformation and Thermomechanical Training on the Functional Stability of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy

We compare the effectiveness of a conventional thermomechanical training procedure and severe plastic deformation via equal channel angular extrusion to achieve improved functional stability in a Ti50.5Ni24.5Pd25 high-temperature shape memory alloy. Thermomechanical testing indicates that both methods result in enhanced shape memory characteristics, such as reduced irrecoverable strain and thermal hysteresis. The mechanisms responsible for the improvements are discussed in light of microstructural findings from transmission electron microscopy.

Atli, K. C.↗
NASA NTRS2011

Shape Memory Characteristics of Ti(sub 49.5)Ni(sub 25)Pd(sub 25)Sc(sub 0.5) High-Temperature Shape Memory Alloy After Severe Plastic Deformation

A Ti(49.5)Ni25Pd25Sc(0.5) high-temperature shape memory alloy is thermomechanically processed to obtain enhanced shape-memory characteristics: in particular, dimensional stability upon repeated thermal cycles under constant loads. This is accomplished using severe plastic deformation via equal channel angular extrusion (ECAE) and post-processing annealing heat treatments. The results of the thermomechanical experiments reveal that the processed materials display enhanced shape memory response, exhibiting higher recoverable transformation and reduced irrecoverable strain levels upon thermal cycling compared with the unprocessed material. This improvement is attributed to the increased strength and resistance of the material against defect generation upon phase transformation as a result of the microstructural refinement due to the ECAE process, as supported by the electron microscopy observations.

Atli, K. C.↗
NASA NTRS2004

Embedded Heaters for Joining or Separating Plastic Parts

A proposed thermal-bonding technique would make it possible to join or separate thermoplastic parts quickly and efficiently. The technique would eliminate the need for conventional welding or for such conventional fastening components as bolted flanges or interlocking hooks. The technique could be particularly useful in the sign industry (in which large quantities of thermoplastics are used) or could be used to join plastic pipes. A thin sheet of a suitable electrically conductive material would be formed to fit between two thermoplastic parts to be joined (see figure). The electrically conductive sheet and the two parts would be put together tightly, then an electrical current would be sent through the conductor to heat the thermoplastic locally. The magnitude of the current and the heating time would be chosen to generate just enough heat to cause the thermoplastic to adhere to both sides of the electrically conductive sheet. Optionally, the electrically conductive sheet could contain many small holes to provide purchase or to increase electrical resistance to facilitate the generation of heat. After thermal bonding, the electrically conductive sheet remains as an integral part of the structure. If necessary, the electrically conductive sheet can be reheated later to separate the joined thermoplastic parts.

Bryant, Melvin A., III↗
NASA NTRS2012

Validation of a Crystal Plasticity Model Using High Energy Diffraction Microscopy

High energy diffraction microscopy is used to measure the crystallographic orientation and evolution of lattice strain in an Al Li alloy. The relative spatial arrangement of the several pancake-shaped grains in a tensile sample is determined through in situ and ex situ techniques. A model for crystal plasticity with continuity of lattice spin is posed, where grains are represented by layers in a finite element mesh following the arrangement indicated by experiment. Comparison is drawn between experiment and simulation.

Beaudoin, A. J.↗
NASA NTRS2014

Multiscale Analysis of Structurally-Graded Microstructures Using Molecular Dynamics, Discrete Dislocation Dynamics and Continuum Crystal Plasticity

A multiscale modeling methodology is developed for structurally-graded material microstructures. Molecular dynamic (MD) simulations are performed at the nanoscale to determine fundamental failure mechanisms and quantify material constitutive parameters. These parameters are used to calibrate material processes at the mesoscale using discrete dislocation dynamics (DD). Different grain boundary interactions with dislocations are analyzed using DD to predict grain-size dependent stress-strain behavior. These relationships are mapped into crystal plasticity (CP) parameters to develop a computationally efficient finite element-based DD/CP model for continuum-level simulations and complete the multiscale analysis by predicting the behavior of macroscopic physical specimens. The present analysis is focused on simulating the behavior of a graded microstructure in which grain sizes are on the order of nanometers in the exterior region and transition to larger, multi-micron size in the interior domain. This microstructural configuration has been shown to offer improved mechanical properties over homogeneous coarse-grained materials by increasing yield stress while maintaining ductility. Various mesoscopic polycrystal models of structurally-graded microstructures are generated, analyzed and used as a benchmark for comparison between multiscale DD/CP model and DD predictions. A final series of simulations utilize the DD/CP analysis method exclusively to study macroscopic models that cannot be analyzed by MD or DD methods alone due to the model size.

Saether, Erik↗
NASA NTRS2014

Lightweight Inexpensive Ozone Lidar Telescope Using a Plastic Fresnel Lens

An inexpensive lightweight ozone lidar telescope was designed, constructed and operated during an ozone lidar field campaign. This report summarizes the design parameters and performance of the plastic Fresnel lens telescope and shows the ozone lidar performance compared to Zemax calculations.

DeYoung, Russell J.↗
NASA NTRS2022

Methane Bioreactor System Offers Sustainable Plastic Alternative for Earth and Space

Mango Materials partnered with the Colorado School of Mines on NASA STTR awards to adapt a bioreactor system to convert methane into bioplastic for low-gravity environments. In space, methane from carbon dioxide conversion systems and waste treatment can be used to 3D print objects and provide polymers for construction and regolith binding. On Earth, the system can convert methane—a greenhouse gas—into environmentally conscious bioplastic. Mango Materials received $6 million through NASA CCRPP, including funds from fashion investors seeking alternatives to plastic-based textiles.

SBIR/STTR↗
NASA NTRS2022

Effects of Debulking on the Fiber Microstructure and Void Distribution in Carbon Fiber Reinforced Plastics

Carbon Fiber Reinforced Plastics (CFRPs) are widely used due to their high stiffness to weight ratios. A common process manufacturers use to increase the strength to weight ratio is debulking. Debulking is the process of compacting a dry fibrous reinforcement prior to resin infusion. This process is meant to decrease the average inter-fiber distance, effectively increasing the fiber volume fraction of the sample. While this process is widely understood macroscopically its effects on fibrous microstructures have not yet been well characterized. The aim of this work is to compare the microstructures of three CFRP laminates, varying only the debulking step in the manufacturing process. High resolution serial sections of all three laminates were taken for analysis. Using these scans, the fiber positions were reconstructed. Statistical descriptors such as local fiber and void volume fractions, fiber orientation, and void distribution and morphology were then generated for each sample. Fiber clusters present within the material were identified and analyzed for each level of debulking applied. Using these descriptors, the effects of debulking on the morphology and organization of the composite microstructure was evaluated.

carbon fiber↗
NASA NTRSDate not supplied

Experimental Characterization of Non-Associative Plasticity Flow Rule Coefficients and Post-Peak Stress Degradation for the LS-DYNA MAT213 Model

This project is focused on developing an experimental framework for characterizing non-associative plasticity flow rule coefficients through coupon-scale tests for the LS-DYNA MAT213 model. The main objective is to characterize these coefficients based on the multi-scale (i.e., both microscopic and macroscopic) full-field measurement of the evolution of strain and stress fields. This paper focuses on presenting the experimental work on characterizing the full-scale stress-strain curves of T700/LM-PAEK composites under tension, compression, and shear loads. The experimental data set was intended to build a deformation sub-model in the MAT213 model for the material. The strain data were collected using both microscopic and macroscopic digital image correlation techniques. The microscopic technique was particularly useful for fracture cases under small strains. A preliminary simulation result obtained from the MAT213 model is also presented in the paper. The experimental framework herein will be extended to characterize post-peak stress degradation in the composite material and to develop a damage sub-model for the material. This project will contribute to developing a simulation tool based on the MAT213 model for simulating the rate-dependent impact damage in composites under multi-axial loading.

MAT213↗
DOE OSTI2022

Co-Gasification of Waste Plastic and Coal Refuse for Thermochemical Upcycling

This study investigated behavior of different mixtures of waste plastics and coal refuse and their potential synergy in steam co-gasification. Co-gasification is an interesting alternative technology to recycle under-utilized waste streams and generate syngas that can be used to produce energy and valuable fuels/chemicals.

Means, Nicholas C.↗
DOE OSTI2022

Apparatus, system, and method for radiation hardened plastic and flexible elastomer scintillator

A scintillating material that is a radiation hardened plastic and flexible elastomer is disclosed. The material is useful in a wide range of high energy particle environments and can be used to create detectors. Such detectors can be used in physics experiments or in medical treatment or imaging. The scintillator can be radiation hardened so as to allow for an extended lifetime over other materials.

Akgun, Ugur↗
DOE OSTI2022

High luminescence plastic scintillators

A plastic scintillator includes a polymeric matrix comprising a primary fluorophore capable of forming an amorphous glass in its pure form. The primary fluorophore is also capable of generating luminescence in the presence of ionizing radiation and includes: a central species including silicon; a luminescent organic group bonded to the central species or to an optional organic linker group, the luminescent organic group including fluorene or an analog thereof; and the optional organic linker group, if present, is bonded to the central species and the luminescent organic group.

Myllenbeck, Nicholas↗
DOE OSTI2023

High luminescence plastic scintillators

A plastic scintillator includes a polymeric matrix comprising a primary fluorophore capable of forming an amorphous glass in its pure form. The primary fluorophore is also capable of generating luminescence in the presence of ionizing radiation and includes: a central species including silicon; a luminescent organic group bonded to the central species or to an optional organic linker group, the luminescent organic group including fluorene or an analog thereof; and the optional organic linker group, if present, is bonded to the central species and the luminescent organic group.

Myllenbeck, Nicholas↗
DOE OSTI2023

Temperature-based reactive flow model for TATB plastic bonded explosives

A new reactive flow model is presented for TATB-based plastic bonded explosives, applicable to shock initiation and detonation problems of differing initial temperature. Temperature disequilibrium is assumed between unreacted explosive, material in the vicinity of compressed defects (called hot spots), and detonation products. The model incorporates temperature-dependent decomposition reaction rates. Arrhenius model parameters were derived from subscale quantum-based molecular dynamics simulations of shock-induced TATB decomposition. Further, a model of detonation carbon aggregation is incorporated, describing the late-time slow release of energy inherent to detonation in TATB-based materials. The predictive ability of the model in the shock initiation regime is tested against recent thin pulse experiments on PBX 9502. Here, the model is found to perform equally well in predicting the size effect curve of ambient, cold, and hot PBX 9502 rate sticks.

Chemistry - Chemical explosives↗
DOE OSTI2024

Microwave-Assisted Co-Gasification of Mixed Plastics and Corn Stover to Produce Clean Hydrogen Using Fe-Based Catalyst

Microwave-assisted gasification is an energy-efficient alternative to conventional gasification in which known feedstocks can be converted into syngas, char, and other byproducts to produce clean hydrogen at lower temperatures (~550 °C) through selective heating. Fe oxides are well-known gasification catalysts that can reduce in-situ to activate the methyl radicals by supplying surface oxygen and promoting H2 formation. This study introduces Fe2O3 as a microwave-active catalyst to enhance H2 production and tar reduction for plastic-corn stover co-gasification. The results found that the microwave reaction at 800 °C produced 24 times more mmol of hydrogen per kWh energy as compared to the conventional run at 900 °C. The X-ray diffraction results show the presence of Fe3O4 and FeO peaks indicating reduction of Fe2O3 to help devolatize reaction intermediates; while the appearance of metallic Fe in the microwave run at 800 °C indicates that Fe2O3 achieves full reduction at the microwave gasification temperature yielding maximum hydrogen production.

Abedin, Ashraf↗
DOE OSTI2024

Sorting of plastics

Systems and methods for classifying and sorting of plastic materials utilizing a vision system and one or more sensor systems, which may implement a machine learning system in order to identify or classify each of the materials, which may then be sorted into separate groups based on such an identification or classification.

Kumar, Nalin↗