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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Metallized Nanotube Polymer Composite (MNPC) and Methods for Making Same

A novel method to develop highly conductive functional materials which can effectively shield various electromagnetic effects (EMEs) and harmful radiations. Metallized nanotube polymer composites (MNPC) are composed of a lightweight polymer matrix, superstrong nanotubes (NT), and functional nanoparticle inclusions. MNPC is prepared by supercritical fluid infusion of various metal precursors (Au, Pt, Fe, and Ni salts), incorporated simultaneously or sequentially, into a solid NT-polymer composite followed by thermal reduction. The infused metal precursor tends to diffuse toward the nanotube surface preferentially as well as the surfaces of the NT-polymer matrix, and is reduced to form nanometer-scale metal particles or metal coatings. The conductivity of the MNPC increases with the metallization, which provides better shielding capabilities against various EMEs and radiations by reflecting and absorbing EM waves more efficiently. Furthermore, the supercritical fluid infusion process aids to improve the toughness of the composite films significantly regardless of the existence of metal.

Park, Cheol↗
NASA NTRS1994

The effect of water on thermal stresses in polymer composites

The fundamentals of the thermodynamic theory of mixtures and continuum thermochemistry are reviewed for a mixture of condensed water and polymer. A specific mixture which is mechanically elastic with temperature and water concentration gradients present is considered. An expression for the partial pressure of water in the mixture is obtained based on certain assumptions regarding the thermodynamic state of the water in the mixture. Along with a simple diffusion equation, this partial pressure expression may be used to simulate the thermostructural behavior of polymer composite materials due to water in the free volumes of the polymer. These equations are applied to a specific polymer composite material during isothermal heating conditions. The thermal stresses obtained by the application of the theory are compared to measured results to verify the accuracy of the approach.

Sullivan, Roy M.↗
NASA NTRS2016

Multifunctional Hybrid Carbon Nanotube/Carbon Fiber Polymer Composites

For aircraft primary structures, carbon fiber reinforced polymer (CFRP) composites possess many advantages over conventional aluminum alloys due to their light weight, higher strengthand stiffness-to-weight ratio, and low life-cycle maintenance costs. However, the relatively low electrical and thermal conductivities of CFRP composites fail to provide structural safety in certain operational conditions such as lightning strikes. Despite several attempts to solve these issues with the addition of carbon nanotubes (CNT) into polymer matrices, and/or by interleaving CNT sheets between conventional carbon fiber (CF) composite layers, there are still interfacial problems that exist between CNTs (or CF) and the resin. In this study, hybrid CNT/CF polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel® IM7/8852 prepreg. Resin concentrations from 1 wt% to 50 wt% were used to infuse the CNT sheets prior to composite fabrication. The interlaminar properties of the resulting hybrid composites were characterized by mode I and II fracture toughness testing (double cantilever beam and end-notched flexure test). Fractographical analysis was performed to study the effect of resin concentration. In addition, multi-directional physical properties like thermal conductivity of the orthotropic hybrid polymer composite were evaluated. Interleaving CNT sheets significantly improved the in-plane (axial and perpendicular direction of CF alignment) thermal conductivity of the hybrid composite laminates by 50 - 400%.

Kang, Jin Ho↗
NASA NTRS2009

Prediction of Material Properties of Nanostructured Polymer Composites Using Atomistic Simulations

Atomistic models of epoxy polymers were built in order to assess the effect of structure at the nanometer scale on the resulting bulk properties such as elastic modulus and thermal conductivity. Atomistic models of both bulk polymer and carbon nanotube polymer composites were built. For the bulk models, the effect of moisture content and temperature on the resulting elastic constants was calculated. A relatively consistent decrease in modulus was seen with increasing temperature. The dependence of modulus on moisture content was less consistent. This behavior was seen for two different epoxy systems, one containing a difunctional epoxy molecule and the other a tetrafunctional epoxy molecule. Both epoxy structures were crosslinked with diamine curing agents. Multifunctional properties were calculated with the nanocomposite models. Molecular dynamics simulation was used to estimate the interfacial thermal (Kapitza) resistance between the carbon nanotube and the surrounding epoxy matrix. These estimated values were used in a multiscale model in order to predict the thermal conductivity of a nanocomposite as a function of the nanometer scaled molecular structure.

Hinkley, J.A.↗
NASA NTRS1993

Space environmental effects on polymer composites: Research needs and opportunities

The long-term performance of polymer-based composites in the space environment is discussed. Both thermoset and thermoplastic matrix composites are included in this discussion. Previous efforts on the space environmental effects on composites are briefly reviewed. Focus of this review is placed on the effects of hygrothermal stresses, atomic oxygen, ultraviolet (UV), and space debris/micrometeoroid impacts along with the potential synergism. Potential approaches to estimating the residual strength of polymer composites after exposure to atomic oxygen erosion or space debris/micrometeoroid impact are evaluated. New ground-based data are then utilized to illustrate the effects of atomic oxygen and thermal cycling on the failure behavior of polymer composites. Finally, research needs, challenges, and opportunities in the field of space environmental effects on composite materials are highlighted.

Jang, Bor Z.↗
NASA NTRS1974

Ultraviolet and thermally stable polymer compositions

A class of polymers is provided, namely, poly(diarylsiloxy) arylazines. These polymers have a basic chemical composition which has the property of stabilizing the optical and physical properties of the polymer against the degradative effect of ultraviolet light and high temperatures. This stabilization occurs at wavelengths including those shorter than found on the surface of the earth and in the absence or presence of oxygen, making the polymers of the present invention useful for high performance coating applications in extraterrestrial space as well as similar applications in terrestrial service. The invention also provides aromatic azines which are useful in the preparation of polymers such as those of the present invention.

Reinisch, R. F.↗
NASA NTRS1981

Acoustic emission monitoring of polymer composite materials

The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

Bardenheier, R.↗
NASA NTRS1990

High-temperature polymer matrix composites

Polymers research at the NASA Lewis Research Center has produced high-temperature, easily processable resin systems, such as PMR-15. In addition, the Polymers Branch has investigated ways to improve the mechanical properties of polymers and the microcracking resistance of polymer matrix composites in response to industry need for new and improved aeropropulsion materials. Current and future research in the Polymers Branch is aimed at advancing the upper use temperature of polymer matrix composites to 700 F and beyond by developing new resins, by examining the use of fiber reinforcements other than graphite, and by developing coatings for polymer matrix composites to increase their oxidation resistance.

Meador, Michael A.↗
NASA NTRS2014

Computational Reduction of Specimen Noise to Enable Improved Thermography Characterization of Flaws in Graphite Polymer Composites

Flaw detection and characterization with thermographic techniques in graphite polymer composites are often limited by localized variations in the thermographic response. Variations in properties such as acceptable porosity, fiber volume content and surface polymer thickness result in variations in the thermal response that in general cause significant variations in the initial thermal response. These result in a "noise" floor that increases the difficulty of detecting and characterizing deeper flaws. A method is presented for computationally removing a significant amount of the "noise" from near surface porosity by diffusing the early time response, then subtracting it from subsequent responses. Simulations of the thermal response of a composite are utilized in defining the limitations of the technique. This method for reducing the data is shown to give considerable improvement characterizing both the size and depth of damage. Examples are shown for data acquired on specimens with fabricated delaminations and impact damage.

Winfree, William P.↗
DOE OSTI2025

Halide perovskite-polymer composite film for bright and stable light-emitting devices

Stability is the primary hindrance for the application of halide perovskite material in light-emitting devices, solar cells, and other devices. In this work, halide perovskite and polymer composite film have been prepared for stable and bright light-emitting devices. Pure-phase Cs4PbBr6 crystals have been synthesized, and their photoluminescence (PL) properties and fluorescence lifetimes have been investigated. The Cs 4 PbBr 6 crystals exhibited high uniformity but underwent rapid photodegradation under light irradiation. To address this issue, we prepared bright light-emitting devices using composite of Cs 4 PbBr 6 crystals and polyethylene oxide (PEO) as the emission layer. The aim was to improve the optical and physical properties of halide perovskites, such as photodegradation and stability. PEO, with its excellent film-forming ability, created a uniform and dense film on the halide perovskite surface, filling microscopic defects and providing a protective barrier. FTIR, morphology, and PL analyses confirmed the protective role of the halide perovskite and polymer composite film. The composite film light-emitting devices demonstrated improved stability and higher PL brightness, with a peak brightness approaching 3 × 10 8 cd/m 2 , which was approximately 75% higher than the pure halide perovskite devices.

Composite film↗
NASA NTRS2026

A Study of Space Environment Effect on Highly Thermally Conductive Hybrid Carbon Fiber Polymer Composites

A set of novel highly thermally conductive hybrid carbon fiber (CF) polymer composites has been developed for lightweight thermal radiator applications in space missions. This study investigates the effects of the space environment on these materials following exposure in low-Earth orbit (LEO) during the Materials International Space Station Experiment (MISSE)-17 flight mission, where samples experienced 159 days of combined atomic oxygen (AO), ultraviolet (UV) radiation, high vacuum, space radiation and thermal cycling. Post-flight characterization included weight loss, surface morphology, thermo-optical properties, molecular structures, glass transition temperature, thermal degradation and thermal conductivity analyses. The pyrolytic graphite sheet (PGS) samples exhibited negligible weight loss, stable thermo-optical property, and only minor oxidation signature on the exposed surface. Although AO erosion of the epoxy polymer matrix was evident, carbon nanotube (CNT)-infused PGS/CF epoxy composites retained high thermal emissivity and preserved their high thermal conductivities. These results demonstrate that the novel highly thermally conductive hybrid CF composites possess strong environmental resilience and are promising candidates for lightweight thermal radiators and thermal management components in future space exploration missions.

Space Environment↗
NASA NTRSDate not supplied

In-situ Lunar Launch and Landing Pad Construction with Regolith-Thermoset Polymer Composite Materials

Lunar launch and landing pads are necessary to mitigate risks to lander/ascent vehicles and surrounding surface assets from rocket plume ejected regolith. The current state of the art of landing and launching from the lunar surface is to land/launch on unprepared regolith surfaces. Though this has been a relatively successful approach, significant risks exist for the Artemis Program due to higher thrust levels leading to increased ejecta and cratering, presence of co-located assets in the ejecta path, and potential strict surface levelness requirements. Regolith-thermoset polymer composite materials were developed and evaluated for off Earth launch and landing pad applications. Performance under hot fire conditions was assessed for two simulated Starship lunar launch/landing environments, one targeting thermal conditions and the second targeting pressure conditions. Paver test articles were prepared at 20% and 11% polymer mass fractions. Sintered paver test articles were prepared with 20% polymer grouting filling the seams between pavers. Though significant erosion was experienced during the more extreme thermal testing conditions, all test articles successfully mitigated regolith ejecta from plume effects. A concept for preparing and emplacing the materials was developed and tested in laboratory conditions. The testing evaluated the feasibility of using twin and single screw extruder technology to mix, convey and deposit materials. Both the twin and single screw extruders were capable of processing and extruding the composite with a maximum of 90% mass fraction of regolith achieved by the twin screw extruder.A primary risk for application of regolith-thermoset polymer composites as lunar launch/landingpad is the mass of polymer required to be landed on the moon. Calculations were performed that show that a 100 m diameter, 0.025 m thick pad with polymer mass fraction of 15% will require a payload mass of 72 mt to the Lunar surface. This is below the planned Starship payload capacity to the lunar surface of 100 mt. The regolith-thermoset polymer composite based construction approach proved feasibility in three critical areas: performance under launch/landing conditions, demonstration of a mixing and depositing strategy, and fitting within the planned lunar payload capacity. It is recommended that materials and systems be developed to TRL 6 for a small-scale lunar demonstration of emplacement of a launch/landing pad via a CLPS mission to support Artemis Program roadmap gap closure activities.

ISRU↗
NASA NTRS2002

Constitutive Modeling of Nanotube-Reinforced Polymer Composites

In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties can no longer be determined through traditional micromechanical approaches that are formulated by using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube lengths, concentrations, and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyimide composite systems.

Odegard, G. M.↗
NASA NTRS2002

Constitutive Modeling of Nanotube-Reinforced Polymer Composites

In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties can no longer be determined through traditional micromechanical approaches that are formulated by using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube shapes, sizes, concentrations, and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/LaRC-SI (with a PmPV interface) composite systems, one with aligned SWNTs and the other with three-dimensionally randomly oriented SWNTs. The Young's modulus and shear modulus have been calculated for the two systems for various nanotube lengths and volume fractions.

Odegard, G. M.↗