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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Evaluation of spacecraft materials and processes for optical degradation potential

A Wide Field Planetary Camera instrument with wide wavelength sensitive Charged Coupled Device detectors has been designed and built for employment in space. The contamination potential of the spacecraft hardware is determined by the outgassing characteristics of the selected materials and the effect of the performed processing procedures. An investigation was conducted to provide for more selective material screening with respect to contamination potential and to develop an optical effects data base. In the investigation, a series of thermogravimetric, residual gas, Micro-Volatile Condensible Material (VCM), and Vacuum Optical Degradation tests were performed. The results of the Micro-VCM testing of four epoxy adhesive systems are presented in tables.

Odonnell, T.↗
NASA NTRS1986

Adhesive evaluation of thin films of LARC-TPI and LARC-TPI with 5 mol % ODA

A commercially available LARC-TPI film and an experimentally prepared film of LARC-TPI with 5 mol % of 4,4'-oxydianiline (ODA), designated as LARC-TPI/ODA in the report, supplied by Mitsui Toatsu Chemicals, Incorporated (MTCI), Japan, were evaluated as thermoplastic adhesive films for bonding Ti-6Al-4V. The LARC-TPI/ODA had been shown by MTCI to possess more flow than thermoplastic LARC-TPI and was, therefore, evaluated and compared to the LARC-TPI. Lap shear strength was used to evaluate the materials as adhesives. They were characterized after fracture by determining the glass transition temperature, Tg. The mode of failure was also reported. Thermal exposure at 204C for 500 and 1000 hrs and a 72-hour water-boil were conducted on lap shear specimens prepared with the two adhesive films. Lap shear tests were conducted at RT, 177C, 204C, and 232C before and after exposures.

Progar, D. J.↗
NASA NTRS1987

Evaluation of polyimide films as adhesives

A commercially available LARC-TPI film and an experimentally prepared film of LARC-TPI with 5 mol pct of 4,4-prime-oxydianiline (ODA), designated as LARC-TPI/ODA, were evaluated as thermoplastic adhesive films for bonding Ti-6Al-4V. Lap shear strength was used to evaluate the materials as adhesives. They were characterized after fracture by determining the glass transition temperature, T(g). The mode of failure is also reported. Thermal exposure at 240 C for 500 and 1000 h and a 72-h water-boil were conducted on lap shear specimens prepared with the two adhesive films. Lap shear tests were conducted at room temperature, 177 C, 204 C, and 232 C before and after exposures.

Progar, Donald J.↗
NASA NTRS1982

Ion Beam Sputtered Coatings of Bioglass

The ion beam sputtering technique available at the NASA-Lewis was used to apply coatings of bioglass to ceramic, metallic, and polymeric substrates. Experiments in vivo and in vitro described investigate these coatings. Some degree of substrate masking was obtained in all samples although stability and reactivity equivalent to bulk bioglass was not observed in all coated samples. Some degree of stability was seen in all coated samples that were reacted in vitro. Both metallic and ceramic substrates coated in this manner failed to show significantly improved coatings over those obtained with existing techniques. Implantation of the coated ceramic substrate samples in bone gave no definite bonding as seen with bulk glass; however, partial and patchy bonding was seen. Polymeric substrates in these studies showed promise of success. The coatings applied were sufficient to mask the underlying reactive test surface and tissue adhesion of collagen to bioglass was seen. Hydrophilic, hydrophobic, charged, and uncharged polymeric surfaces were successfully coated.

Hench, Larry L.↗
NASA NTRS1993

Method of continuously determining crack length

The determination of crack lengths in an accurate and straight forward manner is very useful in studying and preventing load created flaws and cracks. A crack length sensor according to the present invention is fabricated in a rectangular or other geometrical form from a conductive powder impregnated polymer material. The long edges of the sensor are silver painted on both sides and the sensor is then bonded to a test specimen via an adhesive having sufficient thickness to also serve as an insulator. A lead wire is connected to each of the two outwardly facing silver painted edges. The resistance across the sensor changes as a function of the crack length in the specimen and sensor. The novel aspect of the present invention includes the use of relatively uncomplicated sensors and instrumentation to effectively measure the length of generated cracks.

Prabhakaran, Ramamurthy↗
NASA NTRS2007

Space Environment's Effects on Seal Materials

A Low Impact Docking System (LIDS) is being developed by the NASA Johnson Space Center to support future missions of the Crew Exploration Vehicle (CEV). The LIDS is androgynous, such that each system half is identical, thus any two vehicles or modules with LIDS can be coupled. Since each system half is a replica, the main interface seals must seal against each other instead of a conventional flat metal surface. These sealing surfaces are also expected to be exposed to the space environment when vehicles are not docked. The NASA Glenn Research Center (NASA GRC) is supporting this project by developing the main interface seals for the LIDS and determining the durability of candidate seal materials in the space environment. In space, the seals will be exposed to temperatures of between 50 to 50 C, vacuum, atomic oxygen, particle and ultraviolet radiation, and micrometeoroid and orbital debris (MMOD). NASA GRC is presently engaged in determining the effects of these environments on our candidate elastomers. Since silicone rubber is the only class of seal elastomer that functions across the expected temperature range, NASA GRC is focusing on three silicone elastomers: two provided by Parker Hannifin (S0-899-50 and S0-383-70) and one from Esterline Kirkhill (ELA-SA-401). Our results from compression set, elastomer to elastomer adhesion, and seal leakage tests before and after various simulated space exposures will be presented.

deGroh, Henry C., III↗
NASA NTRS2017

Picosecond Pulsed Laser Ablation for the Surface Preparation of Epoxy Composites

As part of a technical challenge under the Advanced Composites Program, methods for improving pre-bond process control for aerospace composite surface treatments and inspections, in conjunction with Federal Aviation Administration guidelines, are under investigation. The overall goal is to demonstrate high fidelity, rapid and reproducible surface treatment and surface characterization methods to reduce uncertainty associated with the bonding process. The desired outcomes are reliable bonded airframe structure, and reduced timeline to certification. In this work, laser ablation was conducted using a q-switched Nd:YVO4 laser capable of nominal pulse durations of 8 picoseconds (ps). Aerospace structural carbon fiber reinforced composites with an epoxy resin matrix were laser treated, characterized, processed into bonded assemblies and mechanically tested. The characterization of ablated surfaces were conducted using scanning electron microscopy (SEM), water contact angle (WCA) goniometry, micro laser induced breakdown spectroscopy (uLIBS), and electron spin resonance (ESR). The bond performance was assessed using a double cantilever beam (DCB) test with an epoxy adhesive. The surface characteristics and bond performance obtained from picosecond ablated carbon fiber reinforced plastics (CFRPs) are presented herein.

Palmieri, Frank↗
NASA NTRS2011

Temperature Effects on Adhesive Bond Strengths and Modulus for Commonly Used Spacecraft Structural Adhesives

A study was performed to observe how changes in temperature and substrate material affected the strength and modulus of an adhesive bondline. Seven different adhesives commonly used in aerospace bonded structures were tested. Aluminum, titanium and Invar adherends were cleaned and primed, then bonded using the manufacturer's recommendations. Following surface preparation, the coupons were bonded with the adhesives. The single lap shear coupons were then pull tested per ASTM D 1002 Standard Test Method for Apparent Shear Strength of Single- Lap-Joint over a temperature range from -150 deg C up to +150 deg C. The ultimate strength was calculated and the resulting data were converted into B-basis design allowables. Average and Bbasis results were compared. Results obtained using aluminum adherends are reported. The effects of using different adherend materials and temperature were also studied and will be reported in a subsequent paper. Dynamic Mechanical Analysis (DMA) was used to study variations in adhesive modulus with temperature. This work resulted in a highly useful database for comparing adhesive performance over a wide range of temperatures, and has facilitated selection of the appropriate adhesive for spacecraft structure applications.

structural adhesives testing↗
NASA NTRS1988

Flexible backbone aromatic polyimide adhesives

Continuing research at Langley Research Center on the synthesis and development of new inexpensive flexible aromatic polyimides as adhesives has resulted in a material identified as LARC-F-SO2 with similarities to polyimidesulfone, PISO2, and other flexible backbone polyimides recently reported by Progar and St. Clair. Also prepared and evaluated was an endcapped version of PISO2. These two polymers were compared with LARC-TPI and LARC-STPI, polyimides research in our laboratory and reported in the literature. The adhesive evaluation, primarily based on lap shear strength (LSS) tests at RT, 177 C and 204 C, involved preparing adhesive tapes, conducting bonding studies and exposing lap shear specimens to 204 C air for up to 1000 hrs and to a 72-hour water boil. The type of adhesive failure as well as the Tg was determined for the fractured specimens. The results indicate that LARC-TPI provides the highest LSSs. LARC-F-SO2, LARC-TPI and LARC-STPI all retain their strengths after thermal exposure for 1000 hrs and PISO2 retains greater than 80 percent of its control strengths. After a 72-hr water boil exposure, most of the four adhesive systems showed reduced strengths for all test temperatures although still retaining a high percentage of their original strength (greater than 60 percent) except for one case. The predominant failure type was cohesive with no significant change in the Tgs.

Progar, Donald J.↗
NASA NTRS1989

Flexible backbone aromatic polyimide adhesives

Continuing research at Langley Research Center on the synthesis and development of new inexpensive flexible aromatic polyimides as adhesives has resulted in a material identified as LARC-F-SO2 with similarities to polyimidesulfone, PISO2, and other flexible backbone polyimides recently reported by Progar and St. Clair. Also prepared and evaluated was an endcapped version of PISO2. These two polymers were compared with LARC-TPI and LARC-STPI, polyimides research in our laboratory and reported in the literature. The adhesive evaluation, primarily based on lap shear strength (LSS) tests at RT, 177 C and 204 C, involved preparing adhesive tapes, conducting bonding studies and exposing lap shear specimens to 204 C air for up to 1000 hrs and to a 72-hour water boil. The type of adhesive failure as well as the Tg was determined for the fractured specimens. The results indicate that LARC-TPI provides the highest LSSs. LARC-F-SO2, LARC-TPI and LARC-STPI all retain their strengths after thermal exposure for 1000 hrs and PISO2 retains greater than 80 percent of its control strengths. After a 72-hr water boil exposure, most of the four adhesive systems showed reduced strengths for all test temperatures although still retaining a high percentage of their original strength (greater than 60 percent) except for one case. The predominant failure type was cohesive with no significant change in the Tgs.

Progar, Donald J.↗
NASA NTRS1974

Design guidelines for use of adhesives and organic coatings in hybrid microcircuits

A study was conducted to investigate the reliability of organic adhesives in hybrid microcircuits. The objectives were twofold: (1) to identify and investigate problem areas that could result from the use of organic adhesives and (2) to develop evaluation tests to quantify the extent to which these problems occur for commercially available adhesives. Efforts were focused on electrically conductive adhesives. Also, a study was made to evaluate selected organic coatings for contamination protection for hybrid microcircuits.

Caruso, S. V.↗
NASA NTRS1988

A comparison of pure mode I and mixed mode I-III cracking of an adhesive containing an open knit cloth carrier

Static and fatigue tests were carried out on two commercial modified epoxy film adhesives with a wide open knit polyester carrier in order to compare crack resistance in mode I and mixed mode I-III loading. The carrier cloth is found to have a significant influence on the cracking behavior of the adhesives. The open air net carrier used in this study separates from the adhesive in mode I cracking but shreds during mixed-mode crack extension. This decreases the opening mode toughness but increases the mixed-mode toughness as compared with results obtained earlier using a heavier knit carrier. The results suggest that the type of carrier may have a far larger influence on crack resistance than is generally recognized.

Ripling, E. J.↗
DOE OSTI2022

Effects of a composite flame retardant system on the flame retardancy and mechanical performance of epoxy resin adhesive

Abstract A flame‐retarded epoxy resin (ER) adhesive with strong flame retardancy and adhesion performance was prepared. The coated ammonium polyphosphate (MFAPP), melamine (MEL), and organic montmorillonite (OMMT) were mixed to prepare a composite flame retardant. It was subsequently blended with a toughened ER thoroughly and then the mixture was cured with polyamide. The resultant ER adhesive thermosets achieved UL‐94 V‐0 rating during vertical burning test, and the limiting oxygen index value was as high as 31.6%. The shear strength of the ER adhesive was 27.9 MPa when 25 wt% MFAPP/MEL/OMMT was introduced. Compared with the pure adhesive, the flame retardant epoxy adhesive maintained outstanding adhesion performance because of the good compatibility between the composite flame retardant additives and the toughened ER adhesive. Cone calorimetry tests indicated that the release of heat and smoke were obviously declined with the incorporation of the composite flame retardant system in comparison to pure ER adhesive thermoset. The investigation of flame retardant mechanism revealed that the composite MFAPP/MEL/OMMT flame retardant system stimulated the generation of highly expanded, integral, and strong char layer and the formed char layer exerted superior insulation effect during combusiton. The present work provided an alternative approach to prepare flame retardant ER adhesive with the similar excellent adhesive performance.

Li, Sheng↗
DOE OSTI2021

Effects of Surface Energy on Adhesive Strength of Sylgard [Slides]

Previous tests showed large variation in measured separation load. Large variation may be attributed to the surface preparation. Surface preparation will be characterized by measuring the free surface energy of the adherents prior to sample assembly.

36 MATERIALS SCIENCE↗
NASA NTRS1976

Development of lightweight fire retardant, low-smoke, high-strength, thermally stable aircraft floor paneling

Fire resistance mechanical property tests were conducted on sandwich configurations composed of resin-fiberglass laminates bonded with adhesives to Nomex honeycomb core. The test results were compared to proposed and current requirements for aircraft floor panel applications to demonstrate that the fire safety of the airplane could be improved without sacrificing mechanical performance of the aircraft floor panels.

Arnold, D. B.↗
NASA NTRS1989

Effect of adhesive interleaving and discontinuous plies on failure of composite laminates subject to transverse normal loads

Results of a series of tests to determine the effects of adhesive interleaving and discontinuous plies (plies with end-to-end gaps) on the displacements, failure loads and failure modes of graphite-epoxy laminates subjected to transverse normal loads are presented. Adhesive interleaving can be used to contain local damage within a group of plies, i.e., to arrest crack propagation on the interlaminate level, and it can increase the amount of normal displacement the laminate can withstand before failure. However, the addition of adhesive interleaving to a laminate does not significantly increase its load carrying capability. A few discontinuous plies in a laminate can reduce the normal displacement and load at failure by 10 to 40 percent compared to a laminate with no discontinuous plies, but the presence of the ply discontinuities does not generally change the failure location or the failure mode of the laminate.

Jegley, Dawn C.↗
NASA NTRS2023

Protective Coatings for Lunar Dust Tolerance

Materials capable of withstanding the harsh lunar environment are critically needed to support long duration, sustainable missions on the Moon’s surface. Lunar dust significantly threatens the durability and reusability of components and vehicles due to possessing a fine, jagged morphology and highly abrasive nature. These characteristics result in the particles eroding, adhering and/or embedding onto component surfaces and into device confined geometries (e.g., gear housing, interlocking systems, etc.) potentially leading to premature failure. The aim of this study is to identify and characterize wear-resistant commercial-off-the-shelf (COTS) materials, including advanced ceramics, for use as protective coatings to minimize abrasion and adhesion caused by lunar dust. Preliminary testing that mimics various aspects of lunar dust degradation, such as abrasive wear and adhesion, suggests that COTS ceramic coatings can improve lunar dust tolerance and protect underlying metallic substrates.

Valerie. L. Wiesner↗
NASA NTRS1987

Adhesive evaluation of water-soluble LARC-TPI

The water-soluble polyimide, identified as TPI(MTC)/H2O, was evaluated as a high temperature thermoplastic adhesive for bonding Ti-6Al-4V and comparing those results primarily with results reported in earlier work with the polyamic-acid/diglyme material. The lap shear strength test was the primary test performed to evaluate the adhesive before (controls) and after thermal exposure in air at 204 C for up to 5000 hours and after a 72 hour water-boil exposure. Lap shear strengths were determined at RT, 177, 204, and 232 C. The adhesive was also characterized after fracture by determining the glass transition temperature as well as defining the mode of failure by visual observation. In general, the results indicate that the TPI(MTC)/H2O retains high lap shear strengths after thermal exposure but had reduced strengths after the water-boil exposure. All failures were cohesive. The TPI(MTC)/H2O compared very well with previous data reported for the standard polyamic-acid/diglyme LARC-TPI results, and therefore, shows promise as a water-soluble adhesive for use in various applications.

Progar, Donald J.↗