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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Amine terminated bisaspartimide polymer

Novel amine terminated bisaspartimides are prepared by a Michael-type reaction of an aromatic bismalteimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers cross-lined through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures, e.g., as lightweight laminates with graphite cloth, molding material prepregs, adhesives and insulating material.

Kumar, D.↗
NASA NTRS1986

Tribological properties of graphite-fiber-reinforced, partially fluorinated polyimide composites

Graphite-fiber-reinforced polyimide (GFRPI) composites were formulated from three new partially fluorinated polyimides and three types of graphite fiber. Nine composites were molded into pins and evaluated in a pin-on-disk tribometer. Friction coefficients, wear rates, pin wear surface morphology, and transfer film formation were assessed at 25 and 300 C. Also assessed was the effect of sliding speed on friction. Wear was up to two orders of magnitude lower at 25 C and up to one order of magnitude lower at 300 C than with previously formulated NASA GFRPI composites.

Fusaro, R. L.↗
NASA NTRS1985

The aerodynamics of rotor blades with ice shapes accreted in hover and in level flight

Through a series of flights in artificial clouds, ice accretions on the main rotor of a UH-1H helicopter were documented in detail upon landing by silicone-rubber molds for both hover and level flights. Full scale reproductions of typical accretions in hover were fabricated by means of epoxy castings and used for a wind-tunnel test program. Surface static pressure distributions were recorded and used to evaluate lift and pitching moment increments while drag was determined by wake surveys. For comparison, accreted ice shapes are presented for two level flight cases as well as preliminary analytical predictions.

Lee, J. D.↗
NASA NTRS1985

Methods for improving reliability in ceramic turbine rotors

Evaluation of Carborundum (CBO) injection-molded sintered alpha silicon carbide (SiC) AGT 100 gasifier turbine rotors by spin testing established a baseline for material strength characteristics. Spin test results of a subsequent group of rotors demonstrated a reduction in average failure speed. Post-test fracture analysis identified surface and near-surface flaws in the back face region to be the typical failure origins. Corrective actions were initiated to address the elimination of the strength controlling flaws. Initial evaluation of rotors fabricated to these process modifications indicates improvements in overall surface quality and average burst speed.

Turner, D. A.↗
NASA NTRS1987

Polyenamines for Films, Coatings, and Adhesives

Easy process makes polymers with good mechanical properties. Synthesis involves Michael-type addition polymerization of two diacetylenic diketones, with various aromatic diamines in m-cresol at 60 to 130 degrees C. Technique provides synthetic route to high-molecular-weight polyenamines with moderate thermal stability and good mechanical properties. Polyenamines produced exhibit potential for use as films, coatings, adhesives, molding compounds, and composite matrices.

Hergenrother, Paul M.↗
NASA NTRS1987

Copolyimides With Flexibilizing Groups

Copolymers improved flexibility, processability and melt-flow characteristics. Copolyimide of new type exhibits synergistic improvements in flow properties due to flexibilized diamine-derived units incorported into polymer backbone. Technique produces copolyimides with combination of flexible linkage that cause polymers to exhibit flow properties particularly well suited for use in wide range of products including adhesives, molding resins, laminating resins, dielectric and protective coatings. Improved properties make copolymers especially useful as thermoplastic hot-melt adhesives.

St. Clair, Terry L.↗
NASA NTRS1987

Polyimides Containing Carbonyl and Ether Connecting Groups

Semicrystallinity gives rise to tough, solvent-resistant polymers. New polyimides prepared from reaction of aromatic dianhydrides with new diamines containing carbonyl and ether connecting groups between aromatic rings. Damines prepared from reaction of 4-aminophenol with activated aromatic difluoro compounds in presence of potassium carbonate. These types of polymers have potential applications in molded products, films, adhesives, and composites.

Hergenrother, Paul M.↗
NASA NTRS1987

Filament-Winding Technique for Concave Parts

Dummy mold and vacuum bagging yield accurate part girth. Proposed method of filament winding facilitates accurate fabrication of fiber/matrix composite parts having closed sections with concave surfaces. Parts laid up by hand now wound with filaments; reducing time and cost of fabrication and improving quality of parts.

Carter, Donald↗
NASA NTRS1987

Pressure-Localizing Inserts for Bagging Laminations

Devices compress composite laminates to conform to tight inside corners of molds. Proposed use of pressure-localizing insert allows composite laminates to be compacted into tight corners by conventional pressure or vacuum-bagging techniques. Because of manufacturing technique, larger selection of part shapes becomes amenable to lamination.

Schmaling, Dave↗
NASA NTRS1987

Thermosetting Fluoropolymer Foams

New process makes fluoropolymer foams with controllable amounts of inert-gas fillings in foam cells. Thermosetting fluoropolymers do not require foaming additives leaving undesirable residues and do not have to be molded and sintered at temperatures of about 240 to 400 degree C. Consequently, better for use with electronic or other parts sensitive to high temperatures or residues. Uses include coatings, electrical insulation, and structural parts.

Lee, Sheng Yen↗
NASA NTRS1987

Polyphenylquinoxalines Containing Alkylenedioxy Groups

New polyphenylquinoxalines (PPQ's) prepared from reaction of novel bis(alpha-diketones) with aromatic bis(o-diamines). Contain alkylenedioxy groups in repeating units. Lower glass-transition temperatures and melt viscosities and better processability than all-aromatic PPQ's. Tensile strength, modulus, elongation, adhesive strength, fracture energy, and solvent resistance of new polymers comparable with properties of known PPQ's. Useful as adhesives, coatings, films, and molded products, particularly for aerospace applications.

Hergenrother, Paul M.↗
NASA NTRS1986

Fabrication of cooled radial turbine rotor

A design and fabrication program was conducted to evaluate a unique concept for constructing a cooled, high temperature radial turbine rotor. This concept, called split blade fabrication was developed as an alternative to internal ceramic coring. In this technique, the internal cooling cavity is created without flow dividers or any other detail by a solid (and therefore stronger) ceramic plate which can be more firmly anchored within the casting shell mold than can conventional detailed ceramic cores. Casting is conducted in the conventional manner, except that the finished product, instead of having finished internal cooling passages, is now a split blade. The internal details of the blade are created separately together with a carrier sheet. The inserts are superalloy. Both are produced by essentially the same software such that they are a net fit. The carrier assemblies are loaded into the split blade and the edges sealed by welding. The entire wheel is Hot Isostatic Pressed (HIPed), braze bonding the internal details to the inside of the blades. During this program, two wheels were successfully produced by the split blade fabrication technique.

Hammer, A. N.↗
NASA NTRS1987

PMR polyimide compositions for improved performance at 371 deg C

Studies were conducted to identify matrix resins which have potential for use at 371 C (700 F). Utilizing PMR methodology, neat resin moldings were prepared with various monomer reactants and screened for thermo-oxidative stability at 371 C (700 F) under both ambient and a four-atmosphere air pressure. The results of the resin screening studies indicate that high molecular weight (HMW) formulated resins of first (PMR-15) and second (PMR-II) generation PMR materials exhibit lower levels of weight loss at 371 C (700 F) than PMR-15 and PMR-II resins. The resin systems which exhibited the best overall balance of processability, Tg and thermo-oxidative stability at 371 C were used to prepare unidirectional Celion 6000 and T-40R graphite fiber laminates. Laminates were evaluated for thermo-oxidative stability and 371 C mechanical properties. Results of the laminate evaluation studies indicate that two of the resin compositions have potential for use in 371 C applications. The most promising resin composition provided laminates which exhibited no drop in 371 C mechanical properties and only 11 percent weight loss after 200 hr exposure to 4 atmospheres of air at 371 C.

Vannucci, Raymond D.↗
NASA NTRS1986

Multi-path peristaltic pump

The instant invention is directed to a peristaltic pump for critical laboratory or hospital applications requiring precise flow rates over an extended period of time. Within the cylindrical barrel pump housing is a single-piece, molded, elastometric, cylindrical liner with a multiplicity of flattened helical channels created therein from one end of the liner to the other. Three cylindrical rollers rotate about the center axis of the pump around the inside surface of the liner selectively compressing the liner, and hence the helical channels between the rollers and the barrel housing, creating a pumping action by forcing trapped fluid in the helical channels axially from one end of the liner to the opposite end. The novelty of the invention appears to lie in the provision of the special liner with multiple helical channels as the pumping chamber, rather than the standard single elastomeric tubing which is squeezed repeatedly by rollers to move the liquid through a typical peristaltic pump. Large, repeated deflections on the standard tubing causes a permanent set in the tubing, thus either changing the flow rate, or requiring a new section of tubing to be positioned in the pump head. Further, this configuration minimizes the amount of outflow pulsation which is characteristic of a typical single tubing peristaltic pump.

Chandler, Joseph A.↗
NASA NTRS1987

Process for preparing phthalocyanine polymer from imide containing bisphthalonitrile

Imide-linked bisphthalonitrile compounds are prepared by combining a dicyano aromatic diamine and an organic dianhydride to produce an amic acid linked bisphthalonitrile compound. The amic acid linked bisphthalonitrile compound is dehydrocyclized to produce the imide-linked bisphthalonitrile compounds. The imide-linked bisphthalonitrile compounds may be polymerized to produce a phythalocyanine polymer by heating the imide-linked bisphthalonitrile compound, either alone or in the presence of a metal powder or a metal salt. These compounds are useful in the coating, laminating and molding arts. The polymers are useful in composite matrix resins where increased fire resistance, toughness and resistance to moisture are required, particularly as secondary structures in aircraft and spacecraft.

Achar, Bappalige N.↗
NASA NTRS1987

Method of making a flexible diaphragm

A diaphragm suitable for extreme temperature usage, such as encountered in critical aerospace applications, is fabricated by a unique method, and of a unique combination of materials, which include multilayered lay-ups of diaphragm materials sandwiched between layers of bleeder fabrics which, after being formed in the desired shape on a mold, are vacuum sealed and then cured under pressure, in a heated autoclave, to produce a bond capable of withstanding extreme temperatures.

Lerma, Guillermo↗
NASA NTRS1977

Aminophenoxycyclotriphosphazene cured epoxy resins and the composites, laminates, adhesives and structures thereof

Aminophenoxy cyclotriphosphazenes such as hexakis (4-aminophenoxy) cyclotriphosphazene and tris (4-aminophenoxy)-tris phenoxy cyclotriphosphazene are used as curing agents for epoxy resins. These 1,2-epoxy resins are selected from di- or polyepoxide containing organic moieties of the formula (CH2-CHO-CH2) m-W-R-W- (CH2CH-CH2O)m where R is diphenyl dimethylmethane, diphenylmethane; W is a nitrogen or oxygen atom; and m is 1 when W is oxygen and 2 when W is nitrogen. The resins are cured thermally in stages at between about 110 to 135 C for between about 1 and 10 min, then at between about 175 to 185 C for between 0.5 to 10 hr and post cured at between about 215 and 235 C for between 0.1 and 2 hr. These resins are useful for making fire resistant elevated temperature stable composites, laminates, molded parts, and adhesives and structures, usually for aircraft secondary structures and for spacecraft construction.

Kumar, Devendra↗
NASA NTRS1987

Optimal cure cycle design of a resin-fiber composite laminate

A unified computed aided design method was studied for the cure cycle design that incorporates an optimal design technique with the analytical model of a composite cure process. The preliminary results of using this proposed method for optimal cure cycle design are reported and discussed. The cure process of interest is the compression molding of a polyester which is described by a diffusion reaction system. The finite element method is employed to convert the initial boundary value problem into a set of first order differential equations which are solved simultaneously by the DE program. The equations for thermal design sensitivities are derived by using the direct differentiation method and are solved by the DE program. A recursive quadratic programming algorithm with an active set strategy called a linearization method is used to optimally design the cure cycle, subjected to the given design performance requirements. The difficulty of casting the cure cycle design process into a proper mathematical form is recognized. Various optimal design problems are formulated to address theses aspects. The optimal solutions of these formulations are compared and discussed.

Hou, Jean W.↗