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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Electrical Conductivity in Textiles

Copper is the most widely used electrical conductor. Like most metals, though, it has several drawbacks: it is heavy, expensive, and can break. Fibers that conduct electricity could be the solutions to these problems, and they are of great interest to NASA. Conductive fibers provide lightweight alternatives to heavy copper wiring in a variety of settings, including aerospace, where weight is always a chief concern. This is an area where NASA is always seeking improved materials. The fibers are also more cost-effective than metals. Expenditure is another area where NASA is always looking to make improvements. In the case of electronics that are confined to small spaces and subject to severe stress, copper is prone to breaking and losing connection over time. Flexible conductive fibers eliminate that problem. They are more supple and stronger than brittle copper and, thus, find good use in these and similar situations. While clearly a much-needed material, electrically conductive fibers are not readily available. The cost of new technology development, with all the pitfalls of troubleshooting production and the years of testing, and without the guarantee of an immediate market, is often too much of a financial hazard for companies to risk. NASA, however, saw the need for electrical fibers in its many projects and sought out a high-tech textile company that was already experimenting in this field, Syscom Technology, Inc., of Columbus, Ohio. Syscom was founded in 1993 to provide computer software engineering services and basic materials research in the areas of high-performance polymer fibers and films. In 1999, Syscom decided to focus its business and technical efforts on development of high-strength, high-performance, and electrically conductive polymer fibers. The company developed AmberStrand, an electrically conductive, low-weight, strong-yet-flexible hybrid metal-polymer YARN.

Source record↗
NASA NTRS1999

Automated quality control for stitching of textile articles

Quality control for stitching of a textile article is performed by measuring thread tension in the stitches as the stitches are being made, determining locations of the stitches, and generating a map including the locations and stitching data derived from the measured thread tensions. The stitching data can be analyzed, off-line or in real time, to identify defective stitches. Defective stitches can then be repaired. Real time analysis of the thread tensions allows problems such as broken needle threads to be corrected immediately.

Miller, Jeffrey L.↗
NASA NTRS2009

Tough Textiles Protect Payloads and Public Safety Officers

In order to create the Mars Pathfinder s mission-critical airbags in the 1990s, NASA s Jet Propulsion Laboratory collaborated with New Ipswich, New Hampshire s Warwick Mills Inc. to weave multi-layer textiles for the airbags for both Pathfinder and the Mars Exploration Rovers. Warwick Mills applied techniques from the collaboration to its puncture- and impact-resistant TurtleSkin product line. The company's metal flex armor (MFA) vests offer stab protection comparable with rigid steel plates and over 50,000 of the vests have sold. The SoftPlate body armor offers protection from handgun bullets, and like the MFA, is designed to be more comfortable than rigid vests. International public safety and military customers are now benefiting from the TurtleSkin products.

Source record↗
NASA NTRS2013

Material Property Characterization of AS4/VRM-34 Textile Laminates

Several material properties (modulus, strengths, and fracture toughness) of a textile composite have been evaluated to provide input data to analytical models of Pultruded Rod Stiffened Efficient Unitized Structure (PRSEUS). The material system is based on warp-knitted preforms of AS4 carbon fibers and VRM-34 epoxy resin, which have been processed via resin infusion and oven curing. Tensile, compressive, shear, and fracture toughness properties have been measured at ambient and elevated temperatures. All specimens were tested in as-fabricated (dry) condition. Specimens were tested with and without through-thickness stitching.

Grenoble, Ray W.↗
NASA NTRS2013

Notched Strength Allowables and Inplane Shear Strength of AS4/VRM-34 Textile Laminates

Notched and unnotched strength allowables were developed for a textile composite to provide input data to analytical structural models based on the Pultruded Rod Stiffened Efficient Unitized Structure (PRSEUS) concept. Filled-hole tensile strength, filled-hole compressive strength, and inplane shear strength along stitch lines have been measured. The material system evaluated in this study is based on warp-knitted preforms of AS4 carbon fibers and VRM-34 epoxy resin, which have been processed via resin infusion and oven curing. All specimens were tested in as-fabricated (dry) condition. Filled-hole strengths were evaluated with and without through-thickness stitching. The effects of scaling on filled-hole tensile strength were evaluated by testing specimens in two widths, but with identical width / hole-diameter ratios. Inplane shear specimens were stitched in two configurations, and two specimen thicknesses were tested for each stitch configuration.

Grenoble, Ray W.↗
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 NTRS2017

Integral Textile Structure for 3-D CMC Turbine Airfoils

An integral textile structure for 3-D CMC turbine airfoils includes top and bottom walls made from an angle-interlock weave, each of the walls comprising warp and weft fiber tows. The top and bottom walls are merged on a first side parallel to the warp fiber tows into a single wall along a portion of their widths, with the weft fiber tows making up the single wall interlocked through the wall's thickness such that delamination of the wall is inhibited. The single wall suitably forms the trailing edge of an airfoil; the top and bottom walls are preferably joined along a second side opposite the first side and parallel to the radial fiber tows by a continuously curved section in which the weave structure remains continuous with the weave structure in the top and bottom walls, the continuously curved section being the leading edge of the airfoil.

Marshall, David B.↗
NASA NTRS2019

Textile Material Lessons Learned During the Design and Qualification of the NASA Orion Capsule Parachute Assembly System

The NASA Orion Capsule Parachute Assembly System (CPAS) development and qualification testing was completed in September 2018. Over the course of the airdrop and ground testing campaign, the team benefited from the ability to design, test, and adjust the design based on observations and inspection results. While the design team used the best knowledge available and attempted to utilize best practices, a number of lessons were learned that should be documented for consideration by future designers. This paper describes these lessons learned including the use of textile reefing loops, the importance of performing joint tests, the impact of using bight sleeves on parachute deployment, and a surprising number of design changes required in the CPAS system after the decision was made to change the suspension line braid to save system mass.

Anderson, Brian P.↗
NASA NTRSDate not supplied

Process Modeling of Woven Textiles

Woven polymer matrix composites offer numerous advantages over traditional unidirectional laminates. Processing conditions affect residual stress that builds up during manufacturing. This work proposes the analysis of three curing parameters on the local residual stress distribution of a plain weave textile architecture, including chemical shrinkage, the temperature cool down, and the evolution of matrix properties as a function of curing. Virtual curing is applied to the inter-tow matrix material of the plain weave Repeating Unit Cell (RUC) modeled in TexGen. Curing is implemented through user-written subroutines within the commercial software suite Abaqus. Results from process modeling are compared with a linear-elastic thermal cool down in Abaqus. A boundary conditions study is also conducted to compare the residual stress build up predicted by Flat(FBCs) and Periodic Boundary Conditions (PBCs). Preliminary results indicate that a thermal cool down over-estimates the end-of-cure stresses in the matrix. Process modeling is conducted with and without chemical shrinkage, then compared with a thermal cool down. Results show that 11.32% of the final stress state is due to chemical shrinkage. Material property evolution during curing also has a non-negligible effect on the end stress.

woven composites↗
NASA NTRSDate not supplied

Multiscale Prediction of Yarn Pullout Failure Mode in Unreinforced Textile Fabrics

Unreinforced woven fabrics have been implemented in a variety of high performance applications, including body armor, deployable structures, and as the reinforcement material in composites. Multiscale modeling techniques have significantly improved the capabilities of simulation-based tools to capture fabric mechanics efficiently and accurately, but often lack in their prediction of failure and require pairing with finite element analysis (FEA) software, limiting their application to the design of ‘fit-for-purpose’ materials. NASA’s Multiscale Analysis Tool (NASMAT) is a standalone multiscale program that has been traditionally used in the analysis of reinforced composites materials. More recently, it has been amended to simulate unreinforced fabric behavior by allowing the geometric state of the tows to change with applied loading due to the lack of a reinforcement material, such as the matrix seen in composites. Previous work has shown the ability of NASMAT to capture nonlinear macroscale behavior by predicting geometric changes in the state of each subcell as a function of the applied loading and allowing each subcell in the analysis to rotate according to these predicted changes, as well as predict nonlinear behavior due to the fiber breakage failure mode. In this work, the capability of predicting the onset and propagation of failure in plain woven fabrics in NASMAT is presented for the yarn pullout failure mode, which occurs when a fabric is loaded at an off-axis angle relative to the warp of weft tow direction. Yarn pullout behavior is initiated by determining the applied load in which the shear resistance of the contact area between yarn families is overcome. When failure is initiated, yarn pullout is determined to have occurred when the applied displacement, calculated from global strain, exceeds the deformed position of a given contact points between yarn families, determined from pin-joint kinematics. Contact points where pullout has occurred contribute to a global damage parameter used to modify the homogenized stiffness of the fabric, resulting in nonlinear behavior observed at the macroscale. The off-axis loading behavior and yarn pullout failure theory have been developed and implemented into NASMAT such that users can simulate off-axis tensile behavior of fabrics in a single, standalone multiscale tool. Simulations are compared to uniaxial tensile tests at various off-axis angles to demonstrate the capability of the tool in its prediction of both the onset of failure at each off-axis angles and the stress-strain behavior as failure progresses.

Materials↗
NASA NTRS1974

A full-scale fire program to evaluate new furnishings and textile materials developed by the National Aeronautics and Space Administration

A program of experimental fires was carried out to establish the advantages offered by new materials for improved fire safety. Four full-scale bedrooms, differing only in the materials used to furnish them, were built and burned to provide comparative data on the fire hazards produced. Cost and availability differences were not considered. The visual evidence provided by TV and photographic coverage of the four experimental room fires showed clearly that the rooms responded very differently to a common ignition condition. Resistance to the ignition and spread of fire was substantially improved in the rooms furnished completely or partially with the new materials.

Hillenbrand, L. J.↗
NASA NTRS1988

Thermoplastic coated carbon fibers for textile preforms

A continuous process for producing prepreg from carbon fiber and thermoplastic matrix is described. After the tow has been spread using a pneumatic device, the process utilizes a fluidized bed to apply thermoplastic powder to the bundle. Finally, direct electrical heating of the coated fiber tow melts the polymer on the individual fibers, creating a uniform and extremely flexible prepreg. The efficiency of the process was evaluated during initial trials in which a thermoplastic polyimide, LaRC-TPI, was applied to T-300, 3K (3000 filament) carbon fiber tow. The physical properties of unidirectional composite specimens fabricated from this prepreg were measured, and the matrix uniformity and void content of the samples was determined. The results of these evaluations are detailed and discussed.

Allen, L. E.↗
NASA NTRS1992

Physical interpretation and development of ultrasonic nondestructive evaluation techniques applied to the quantitative characterization of textile composite materials

The development and implementation of advanced ultrasonic nondestructive evaluation methods applied to the characterization of composite materials requires a better understanding of the physics underlying the interaction of ultrasound with the material. The purpose of this investigation is to identify and characterize the features of complex, three dimensional materials that limit the ability of ultrasound to detect flaws in this broad class of emerging materials. In order to explore the interaction of ultrasound with such complex media, we investigate the characteristics of ultrasonic fields which have propagated through samples with complex geometries and/or internal architecture. We focus on the physics that underlies the detection of flaws in such materials.

Miller, James G.↗
NASA NTRS1993

Physical interpretation and development of ultrasonic nondestructive evaluation techniques applied to the quantitative characterization of textile composite materials

In this Progress Report, we describe our current research activities concerning the development and implementation of advanced ultrasonic nondestructive evaluation methods applied to the characterization of stitched composite materials and bonded aluminum plate specimens. One purpose of this investigation is to identify and characterize specific features of polar backscatter interrogation which enhance the ability of ultrasound to detect flaws in a stitched composite laminate. Another focus is to explore the feasibility of implementing medical linear array imaging technology as a viable ultrasonic-based nondestructive evaluation method to inspect and characterize bonded aluminum lap joints. As an approach to implementing quantitative ultrasonic inspection methods to both of these materials, we focus on the physics that underlies the detection of flaws in such materials.

Miller, James G.↗