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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Effects of Contamination and Cleaning on Parachute Structural Textile Elements

Throughout their lifecycle, parachute textiles come into contact with various other substances. This contact may occur during manufacturing and repair, storage and transportation, packing, or actual use. While this interaction does not always result in negative repercussions, it may cause a loss in material strength. This paper examines the strength degradation due to several contaminants as well as the effects of cleaning agents on common parachute materials. Materials tested were: Kevlar cord and webbing, Nylon broadcloth and webbing, and Vectran cord; all of these constitute the major structural elements for CPAS (Capsule Parachute Assembly System), the parachute system for the NASA Orion Crew Module. Contaminants tested were: sewing machine oil, dried stamping ink, dirt, basting glue, Sergene, and rust. Recommendations for cleaning (or not cleaning) these materials with respect to each of the contaminants are given in this paper, as well as recommendations for future tests.

Mollmann, Catherine↗
NASA NTRS1993

A bilinear failure criterion for mixed-mode delamination

Many different failure criteria have been suggested for mixed-mode delamination toughness, but few sets of mixed-mode data exist that are consistent over the full range of Mode 1 opening load to Mode 2 shear load range. The mixed-mode bending (MMB) test was used to measure the delamination toughness of a brittle epoxy composite, a state-of-the-art toughened epoxy composite, and a tough thermoplastic composite over the full mixed-mode range. To gain insight into the different failure responses of the different materials, the delamination fracture surfaces were also examined. An evaluation of several failure criteria that have been reported in the literature was performed, and the range of responses modeled by each criterion was analyzed. A bilinear failure criterion was introduced based on a change in the failure mechanism observed from the delamination surfaces. The different criteria were compared to the failure response of the three materials tested. The responses of the two epoxies were best modeled with the new bilinear failure criterion. The failure response of the tough thermoplastic composite could be modeled well with the bilinear criterion but could also be modeled with the more simple linear failure criterion. Since the materials differed in their mixed-mode failure response, mixed-mode delamination testing will be needed to characterize a composite material. This paper presents consistent sets of mixed-mode data, provides a critical evaluation of the mixed-mode failure criteria, and should provide general guidance for selecting an appropriate criterion for other materials.

Reeder, James R.↗
NASA NTRS2017

Flow-Tube Reactor Experiments on the High Temperature Oxidation of Carbon Weaves

Under entry conditions carbon weaves used in thermal protection systems (TPS) decompose via oxidation. Modeling this phenomenon is challenging due to the different regimes encountered along a flight trajectory. Approaches using equilibrium chemistry may lead to over-estimated mass loss and recession at certain conditions. Concurrently, there is a shortcoming of experimental data on carbon weaves to enable development of improved models. In this work, a flow-tube test facility was used to measure the oxidation of carbon weaves at temperatures up to 1500 K. The material tested was the 3D carbon weave used for the heat shield of the NASA Adaptive Deployable Entry and Placement Technology, ADEPT. Oxidation was characterized by quantifying decomposition gases (CO and CO2), by mass measurements, and by microscale surface analysis. The current set of measurements contributes to the development of finite rate chemistry models for carbon fabrics used in woven TPS materials.

Woven TPS↗
NASA NTRS2014

Thermal Testing of Thermal Protection System (TPS) Materials

High temperature testing of thermal protection system (TPS) materials is a critical aspect of heat-shield materials development, as it determines the suitability and performance envelope of the materials. The present talk provides an overview of different high temperature test facilities that are available for conducting thermal tests for TPS materials. The facilities include arcjet testing, solar tower testing facilities and laser test facility. The facilities are selected based on the requirements and objectives of the tests and each have their benefits and limitations. The paper also describes the process of determining the test environments based on mission profiles and requirements. Some of the recent thermal tests of TPS materials are discussed in this paper. These tests have helped improve the TRL (Technology Readiness Level) level of novel TPS materials and make them viable TPS material candidates for future missions.

Thermal Protection Materials↗
NASA NTRS1971

Mishaps with Oxygen in NASA Operations

Data from a substantial number of oxygen mishaps obtained from NASA and contractor records are presented. Information from several Air Force records, concerning oxygen accidents involving aircraft operations, are also included. Descriptions of the mishaps and their causes, for both liquid and gaseous oxygen in ground test facilities and space vehicle systems, are given. A number of safety regulations aimed at reducing the accident probability is discussed. The problems related to material compatibility and materials testing are considered, and the limited information on factors affecting the ignition of materials in oxygen is presented. In addition, details are given of several of the accident/incidents listed in order to define the combination of conditions causing the mishap. In addition to propellant system mishaps, accident/incidents which occurred in space and ground system structures were included, as well as those in electrical systems, ground support facilities, ordnance, and related operations.

Ordin, Paul M.↗
NASA NTRS1978

The development of methods for the prediction of primary creep behavior in metals

The applicability of a thermodynamic constitutive theory of deformation to the prediction of primary creep and creep strain relaxation behavior in metals is examined. Constitutive equations derived from the theory are subjected to a parametric analysis in order to determine the influence of several parameters on the curve forms generated by the equations. A computer program is developed which enables the solution of a generalized constitutive equation using experimental data as input. Several metals were tested to form a data base of primary creep and relaxation behavior. The extent to which these materials conformed to the constitutive equation showed wide variability, with the alloy Ti-6Al-4V exhibiting the most consistent results. Accordingly, most of the analysis is concentrated upon data from that alloy, although creep and relaxation data from all the materials tested are presented. Experimental methods are outlined as well as some variations in methods of analysis. Various theoretical and practical implications of the work are discussed.

Zerwekh, R. P.↗
NASA NTRS1994

A Comparison of Atomic Oxygen Erosion Yields of Carbon and Selected Polymers Exposed in Ground Based Facilities and in Low Earth Orbit

A comparison of the relative erosion yields (volume of material removed per oxygen atom arriving) for FEP Teflon, polyethylene, and pyrolytic graphite with respect to Kapton HN was performed in an atomic oxygen directed beam system, in a plasma asher, and in space on the EOIM-III (Evaluation of Oxygen Interaction with Materials-III) flight experiment. This comparison was performed to determine the sensitivity of material reaction to atomic oxygen flux, atomic oxygen fluence, and vacuum ultraviolet radiation for enabling accurate estimates of durability in ground based facilities. The relative erosion yield of pyrolytic graphite was found not to be sensitive to these factors, that for FEP was sensitive slightly to fluence and possibly ions, and that for polyethylene was found to be partially VUV and flux sensitive but more sensitive to an unknown factor. Results indicate that the ability to use these facilities for material relative durability prediction is great as long as the sensitivity of particular materials to conditions such as VUV, and atomic oxygen flux and fluence are taken into account. When testing materials of a particular group such as teflon, it may be best to use a witness sample made of a similar material that has some available space data on it. This would enable one to predict an equivalent exposure in the ground based facility.

Rutledge, Sharon K.↗
NASA NTRS1998

Ultrasonic Attenuation Results of Thermoplastic Resin Composites Undergoing Thermal and Fatigue Loading

As part of an effort to obtain the required information about new composites for aviation use, materials and NDE researchers at NASA are jointly performing mechanical and NDE measurements on new composite materials. The materials testing laboratory at NASA is equipped with environmental chambers mounted on load frames that can expose composite materials to thermal and loading cycles representative of flight protocols. Applying both temperature and load simultaneously will help to highlight temperature and load interactions during the aging of these composite materials. This report highlights our initial ultrasonic attenuation results from thermoplastic composite samples that have undergone over 4000 flight cycles to date. Ultrasonic attenuation measurements are a standard method used to assess the effects of material degradation. Recently, researchers have shown that they could obtain adequate contrast in the evaluation of thermal degradation in thermoplastic composites by using frequencies of ultrasound on the order of 24 MHz. In this study, we address the relationship of attenuation measured at lower frequencies in thermoplastic composites undergoing both thermal and mechanical loading. We also compare these thermoplastic results with some data from thermoset composites undergoing similar protocols. The composite s attenuation is reported as the slope of attenuation with respect to frequency, defined as b = Da(f)/Df. The slope of attenuation is an attractive parameter since it is quantitative, yet does not require interface corrections like conventional quantitative attenuation measurements. This latter feature is a consequence of the assumption that interface correction terms are frequency independent. Uncertainty in those correction terms can compromise the value of conventional quantitative attenuation data. Furthermore, the slope of the attenuation more directly utilizes the bandwidth information and in addition, the bandwidth can be adjusted in the post processing stage to compensate for the loss of dynamic range of the signal as the composites age.

Madaras, Eric I.↗
NASA NTRS2016

Information Management Workflow and Tools Enabling Multiscale Modeling Within ICME Paradigm

With the increased emphasis on reducing the cost and time to market of new materials, the need for analytical tools that enable the virtual design and optimization of materials throughout their processing - internal structure - property - performance envelope, along with the capturing and storing of the associated material and model information across its lifecycle, has become critical. This need is also fueled by the demands for higher efficiency in material testing; consistency, quality and traceability of data; product design; engineering analysis; as well as control of access to proprietary or sensitive information. Fortunately, material information management systems and physics-based multiscale modeling methods have kept pace with the growing user demands. Herein, recent efforts to establish workflow for and demonstrate a unique set of web application tools for linking NASA GRC's Integrated Computational Materials Engineering (ICME) Granta MI database schema and NASA GRC's Integrated multiscale Micromechanics Analysis Code (ImMAC) software toolset are presented. The goal is to enable seamless coupling between both test data and simulation data, which is captured and tracked automatically within Granta MI®, with full model pedigree information. These tools, and this type of linkage, are foundational to realizing the full potential of ICME, in which materials processing, microstructure, properties, and performance are coupled to enable application-driven design and optimization of materials and structures.

Materials Engineering↗
NASA NTRS1995

Standard methods for filled hole tension testing of textile composites

The effects of two test specimen geometry parameters, the specimen width and W/D ratio, on filled-hole tensile strength were determined for textile composite materials. Test data generated by Boeing and Lockheed on 2-D and 3-D braids, and 3-D weaves were used to make these evaluations. The investigation indicated that filled-hole tensile-strength showed little sensitivity to either parameter. Test specimen configurations used in open-hole tension tests, such as those suggested by ASTM D5766 - Standard Test Method for Open Hole Tensile Strength of Polymer Matrix Composite Laminates or those proposed by MIL-HDBK-17-lD should provide adequate results for material comparisons studies. Comparisons of the materials' open-hole and filled-hole tensile strengths indicated that the latter were generally lower than the former. The 3-D braids were the exception; their filled-hole strengths were unexpected larger than their open-hole strengths. However, these increases were small compared to the scatter in the data. Thus, filled hole tension may be a critical design consideration for textile composite materials.

Portanova, M. A.↗
NASA NTRS1965

Testing device subjects elastic materials to biaxial deformations

Testing device stretches elastic materials biaxially over large deformation ranges and varies strain ratios in two perpendicular directions. The device is used in conjunction with a tensile testing machine, which holds the specimen and permits control over the direction and magnitude of the stresses applied.

Becker, G. W.↗
NASA NTRS2005

Correlating PMC-MMC Bonded Joint 3D FEA with Test

A viewgraph presentation on the correlation of Polymer Matrix Composites (PMC) and Metal Matrix Composites (MMC) bonded joints using three dimensional finite element analyses with materials tests is shown.

Jacobson, Mindy↗
NASA NTRS1992

Indentation flaw formation and strength response of silicon nitride ceramics at low indentation loads

The configuration and the strength response of indentation flaws in silicon nitrides are described as a function of indentation loads primarily near the threshold level. Test materials under consideration include 30 vol percent SiC whisker-reinforced composite silicon nitride and similar monolithic silicon nitride. The results of strength testing show that, at indentation loads less than or equal to 1.96, a number of the specimens fail from the intrinsic flaws of the materials rather than from the indent sites, causing a distinct trend to reach a plateau, at a level corresponding to the as-received strength of the material. The ratio of the mirror constant to the fracture toughness for the composite and monolithic materials is found to be 1.44 and 1.51, respectively.

Choi, Sung R.↗
DOE OSTI2024

Elevated Temperature Graphite Mechanical Testing

High purity graphite will be used for core components within most High Temperature Reactor (HTR) designs. Several "high tech” industries currently utilize synthetic, high-purity, commercially available graphite components to fabricate photovoltaic cells, semi-conductors, optical fibers, and other high value electronic industry products. New advanced HTR designs are also interested in using these graphite grades for long-term, internal core component applications. Consequently, the US Department of Energy, Advanced Reactor Technologies (DOE-ART) program has spent several years testing different high purity graphite grades for potential use within these new nuclear reactor designs. A significant part of that effort has been in the development and improvement of American Society for Testing and Materials (ASTM) test standards specifically for nuclear graphite grades. Nearly all ASTM test standards have either been developed or improved by the DOE-ART program over the past 25 years. The ART program continues to assist in the development of new ASTM test standards in support of the future commercial HTR fleet currently being designed and built in the USA. The newest effort undertaken by ART is the development of high temperature mechanical testing practices that may be acceptable for a future ASTM test standard (or guide) for this critical material property measurement.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Swelling of TPX

The hygroscopic swelling and the thermal expansion behavior of TPX showed anomalous behavior relative to our observations for several other materials tested in the last few years. The hygroscopic swelling showed no correlation to the change in humidity, i.e., the material didn’t necessarily always swell when humidity was increased, it sometime shrank as well. In response to increase in temperature, the material consistently expanded. However, the rate of expansion with temperature changed between experiments. Hence, it was difficult to extract any reliable parameter values for this material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1983

Ablation of carbonaceous materials in a hydrogen-helium arc-jet flow

The stagnation-point ablation rates of a graphite, a carbon-carbon composite, and four carbon-phenolic materials are measured in an arc-jet wind tunnel with a 50% hydrogen-50% helium mixture as the test gas. Flow environments are determined through measurements of static and impact pressures, heat-transfer rates to a calorimeter, and radiation spectra, and through numerical calculation of the flow through the wind tunnel, spectra, and heat-transfer rates. The environments so determined are: impact pressure approx. 3 atm, Mach number approx. 2.1, convective heat-transfer rate approx. 14 kw/sq cm, and radiative heat-transfer rate approx. 7 kw/sq cm in the absence of ablation. Ablation rates are determined from the measured rates of mass loss and recession of the ablation specimens. Compared with the predicted ablation rates obtained by running RASLE and CMA codes, the measured rates are higher by about 15% for all tested materials.

Park, C.↗
NASA NTRS1997

Test Report: Direct and Indirect Lightning Effects on Composite Materials

Lightning tests were performed on composite materials as a part of an investigation of electromagnetic effects on the materials. Samples were subjected to direct and remote simulated lightning strikes. Samples included various thicknesses of graphite filament reinforced plastic (GFRP), material enhanced by expanded aluminum foil layers, and material with an aluminum honeycomb core. Shielding properties of the material and damage to the sample surfaces and joints were investigated. Adding expanded aluminum foil layers and increasing the thickness of GFRP improves the shielding effectiveness against lightning induced fields and the ability to withstand lightning strikes. A report describing the lightning strike tests performed by the U.S. Army Redstone Technical Test Center, Redstone Arsenal, AL, STERT-TE-E-EM, is included as an appendix.

Composite materials↗