The United States of America As Represented by the Administrator of the

The United States of America As Represented by the United States

Robert M Baucom

Joseph M Marchello

John J Snoha

Terry L St Clair

Norman J Johnston

Donald A Sandusky

John R Gleason

Tan-Hung Hou

Paul W Kidder

Darleen A Druyun

Erik S Weiser

Rakasi M Reddy

This invention improves upon a method for molding structural parts from preform material. Preform material to be used for the part is provided. A silicone rubber composition containing entrained air voids is prepared. The silicone rubber and preform material assembly is situated within a rigid mold cavity used to shape the preform material to the desired shape. The entire assembly is heated in a standard heating device so that the thermal expansion of the silicone rubber exerts the pressure necessary to force the preform material into contact with the mold container. The introduction of discrete air voids into the silicone rubber allows for accurately controlled pressure application on the preform material at the cure temperature.

Method for molding structural parts utilizing modified silicone rubber

A shaped towpreg ribbon having a cross-sectional geometry which promotes intimate lateral contact between adjacent composite tows was prepared. The cross-sectional geometry is non-rectangular and promotes intimate lateral contact between adjacent towpreg ribbons during normal processing.

Non-rectangular towpreg architectures

A low pressure process was developed for preparing a well-consolidated polyimide composite laminate. Prepreg plies were formed from unidirectional fibers and a polyamic acid resin solution. Molding stops were placed at the sides of a matched metal die mold. The prepreg plies were cut shorter than the length of the mold in the in-plane lateral direction and were stacked between the molding stops to a height which was higher than the molding stops. The plies were then compressed to the height of the stops and heated to allow the volatiles to escape and to start the imidization reaction. After removing the stops from the mold, the heat was increased and 0-500 p.s.i. pressure was applied to complete the imidization reaction. The heat and pressure were further increased to form a consolidated polyimide composite laminate.

Low pressure process for continuous fiber reinforced polyamic acid resin

This invention is a process for the uniform application of polymer powder particles to a filamentary material in a continuous manner to form a uniform composite prepreg material. A tow of the filamentary material is fed under carefully controlled tension into a spreading unit, where it is spread pneumatically into an even band. The spread filamentary tow is then coated with polymer particles from a fluidized bed, after which the coated filamentary tow is fused before take-up on a package for subsequent utilization. This process produces a composite prepreg uniformly without imposing severe stress on the filamentary material, and without requiring long, high temperature residence times for the polymer.

Process for application of powder particles to filamentary materials

Composite materials with matrices of tough, thermoplastic aromatic polyimides are obtained by blending semi-crystalline polyimide powders with polyamic acid solutions to form slurries, which are used in turn to prepare prepregs, the consolidation of which into finished composites is characterized by excellent melt flow during processing.

Preparing composite materials from matrices of processable aromatic

An X-ray transparent and biological inert medical clip for treating aneurisms and the like and process for producing same wherein a graphite reinforced composite film 15, 16, 20 and 21 (FIGS. 1a-1d) is molded into a unitary structure having a pair of 'hourglass' like cavities 30, 31 (FIG. 2) hinged together (33) with a pair of jaws 27 and 28 for grasping the aneurism extending from the wall of one cavity and a silicone rubber pellet 35 (FIG. 3) disposed in the other cavity to exert a spring force through the hinge area 33 to normally bias the jaws into contact with each other.

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Newport News, VA, United States of America

Robert M Baucom