Engineering topics

Baucom, Robert M.

Publications and source records attributed to Baucom, Robert M..

28 records · Page 2

NASA NTRS1991

LaRC dry powder towpreg process

The dry powder towpreg process overcomes many of the difficulties associated with melt, solution and slurry prepregging of advanced composite materials. In the process, fluidized powder is deposited on spread tow bundles and melted on the fibers by radiant heating to adhere the polymer to the fiber. Bench scale design and operating data have been correlated for use in process scale up to commercial operation. Powdered towpreg has been woven and molded into preform material of good quality. Cost estimates suggest that processing costs are comparable to those of conventional hot melt prepreg. In the future, from a part fabrication point of view, powder coated prepreg tape, woven broad goods and woven and braided preforms may be considered as options to similar materials made by other methods.

Marchello, Joseph M.↗

NASA NTRS1991

Powder towpreg process development

The process for dry powder impregnation of carbon fiber tows being developed at LaRC overcomes many of the difficulties associated with melt, solution, and slurry prepregging. In the process, fluidized powder is deposited on spread tow bundles and fused to the fibers by radiant heating. Impregnated tows have been produced for preform, weaving, and composite materials applications. Design and operating data correlations were developed for scale up of the process to commercial operation. Bench scale single tow experiments at tow speeds up to 50 cm/sec have demonstrated that the process can be controlled to produce weavable towpreg. Samples were woven and molded into preform material of good quality.

Baucom, Robert M.↗

NASA NTRS1990

LARC powder prepreg system

Thermoplastic prepregs of LARC-TPI have been produced in a fluidized bed unit on spread continuous fiber tows. The powders are melted on the fibers by radiant heating to adhere the polymer to the fiber. This process produces tow prepreg uniformly without imposing severe stress on the fibers or requiring long high temperature residence times for the polymer. Unit design theory and operating correlations have been developed to provide the basis for scale up to commercial operation. Special features of the operation are the pneumatic tow spreader, fluidized bed and resin feed systems.

Baucom, Robert M.↗

NASA NTRS1990

NASA. Langley Research Center dry powder towpreg system

Dry powder polymer impregnated carbon fiber tows were produced for preform weaving and composite materials molding applications. In the process, fluidized powder is deposited on spread tow bundles and melted on the fibers by radiant heating to adhere the polymer to the fiber. Unit design theory and operating correlations were developed to provide the basis for scale up of the process to commercial operation. Special features of the operation are the pneumatic tow spreader, fluidized bed, resin feeder, and quality control system. Bench scale experiments, at tow speeds up to 50 cm/sec, demonstrated that process variables can be controlled to produce weavable LARC-TPI carbon fiber towpreg. The towpreg made by the dry powder process was formed into unidirectional fiber moldings and was woven and molded into preform material of good quality.

Baucom, Robert M.↗

NASA NTRS1990

Study of flexural rigidity of weavable powder-coated towpreg

An effort has been made to weave powder-impregnated tow into a two-dimensional preform, controlling process variables to obtain high flexural rigidity in the warp direction and greater flexibility in the fill direction. The resulting prepregs have been consolidated into laminates with LaRC-TPI matrices. Complementary SEM and DSC studies have been performed to deepen understanding of the relationship between tow flexibility and heat treatment. Attention is also given to the oven temperature and residence time variables' effects on power/fiber fusion.

Hirt, Douglas E.↗

NASA NTRS1989

Polyimide Matrix composites: Polyimidesulfone/LARC-TPI (1:1) blend

Polyimide matrix composites were fabricated from unidirectional unsized AS-4 carbon fiber and a doped 1:1 blend of two polyimides: benzophenone dianhydride-3,3'-diamino diphenylsulfone (PISO2) and benzophenone dianhydride-3,3'-diamino benzophenone (LARC-TPI). To enhance melt flow properties, the molecular weight of the PISO2 was controlled by end-capping with phthalic anhydride and addition of 5 percent by weight p-phenylene diamine-phthalic anhydride bisamic acid dopant. Prepreg was drum-wound using a diglyme slurry comprised of the soluble polyamideacid of PISO2, the soluble bisamideacid of the dopant, and the insoluble imidized LARC-TPI powder. Melt flow studies with a rotary rheometer and parallel plate plastometer on neat resin and prepreg helped develop an optimum cure cycle. Composite mechanical properties at room and elevated temperatures, dry and moisture-saturated, were evaluated, including short beam shear strength and flexure, tensile, shear, and compression properties. Two 18 in. x 24 in. skin-stringer panels were fabricated, one of which was tested in compression to failure.

Johnston, Norman J.↗

NASA NTRS1989

Polyimide matrix composites - Polyimidesulfone/LARC-TPI (1:1) blend

Polyimide matrix composites were fabricated from unidirectional unsized AS-4 carbon fiber and a doped 1:1 blend of two polyimides: PISO2 and LARC-TPI. To enhance melt flow properties, the molecular weight of the PISO2 was controlled by end-capping with phthalic anhydride and addition of 5 percent by weight p-phenylenediamine-phthalic anhydride bisamic acid dopant. Prepreg was drum-wound using a diglyme slurry comprised of the soluble polyamideacid of PISO2, the soluble bisamideacid of the dopant, and the insoluble imidized LARC-TPI powder. Melt flow studies with a rotary rheometer and parallel plate plastometer on neat resin and prepreg helped develop an optimum cure cycle. Composite mechanical properties at room and elevated temperatures, dry and moisture-saturated, were evaluated, including short beam shear strength and flexure, tensile, shear, and compression properties. Two 18 x 24-inch skin-stringer panels were fabricated, one of which was tested in compression to failure.

Johnston, Norman J.↗

NASA NTRS1989

Combining LaRC-TPI powder with carbon fiber by electrostatic fluidized bed coating

Thermoplastic polyimide prepreg tow is produced rapidly and efficiently by applying the LaRC-TPI matrix as an electrostatically charged and fluidized powder to electrically grounded and spread carbon fiber tow. The powder is melted after coating to insure adhesion to the fibers and to reduce tow friction. Excellent wetout in towpreg samples is obtained resulting in very flexible prepregs. Processing conditions of this towpreg produced with LaRC-TPI powders from Rogers Corp. and Mitsui Toatsu Chemicals are described. Mechanical properties of the towpreg and unidirectional laminates are presented in detail.

Varughese, Babu↗

NASA NTRS1988

High performance composites research at NASA-Langley

Barriers to the more extensive use of advanced composites in heavily loaded structures on commercial transports are discussed from a materials viewpoint. NASA-Langley matrix development activities designed to overcome these barriers are presented. These include the synthesis of processible, tough, durable matrices, the development of resin property/composite property relationships which help guide the synthesis program, and the exploitation of new processing technology to effectively combine reinforcement filament with polymer matrices. Examples of five classes of polymers being investigated as matrix resins at NASA Langley are presented, including amorphous and semicrystalline thermoplastics, lightly crosslinked thermoplastics, semi-interpenetrating networks and toughened thermosets. Relationships between neat resin modulus, resin fracture energy, interlaminar fracture energy, composite compression strength, and post-impact compression strength are shown. Powder and slurry processing techniques are discussed.

Stclair, Terry L.↗

NASA NTRS1988

High performance composites research at NASA-Langley

Barriers to the more extensive use of advanced composites in heavily loaded structures on commercial transports are discussed from a materials viewpoint. NASA Langley matrix development activities designed to overcome these barriers are presented. These include the synthesis of processable, tough, durable matrices, the development of resin-property/composite-property relationships which help guide the synthesis program, and the exploitation of new processing technology to effectively combine reinforcement filaments with polymer matrices. Examples of five classes of polymers being investigated as matrix resins at NASA Langley are presented, including amorphous and semicrystalline thermoplastics, lightly crosslinked thermoplastics, semiinterpenetrating networks, and toughened thermosets. Relationships between neat resin modulus, resin fracture energy, interlaminar fracture energy, composite compression strength, and postimpact compression strength are shown. Powder and slurry processing techniques are discussed.

Saint Clair, Terry L.↗