United Technologies Corporation

Nicholas P Flonc

Michael W Brace

Philip J Ramey

Robert L Faiz

Dean Nguyen

Kenneth M Adams

William J Walker

A method for forming stabilized preforms for complex composite articles is disclosed using a solid meltable uncatalyzed thermosetting resin as the stabilizing agent. The resin is applied to each layer of the preform and heated to melt the resin and bond the layers together. After cooling, the resin resolidifies but does not set and thereby holds the layers in the desired preform shape. The layers can be first formed into a flat sheet as a raw material from which shaped preforms can be made by cutting the sheet into sections which are placed over a mandrel and reheating to thereby remelt the solid resin to allow the preform to conform to the shape of the mandrel. Utilizing this process allows complex composite parts to be easily preformed and assembled prior to placement in a mold for resin injection molding, without inhibiting part strength as the resin is compatible with the injection resin and is cocatalyzed by the catalyst contained in the injection resin.

Stabilized complex composite preforms

Method for stabilizing complex composite preforms

A shrinkable foam mandrel that can be easily removed and composite resin transfer molding process that uses the foam mandrel. The foam is dimensionally stable at a first temperature that typically corresponds to the cure temperature of the composite resin. The foam is capable of irreversibly shrinking to less than about 0.5 said foam's original size at a second tempertaure that is above said first tempertaure. The foam is encapsulated by a non-stick elastomer skin and covered with fibers. The fiber covered elastomer encapsulated foam is disposed in a female mold cavity and resin is injected into the female mold cavity. The resin and fibers are cured and the resulting composite component is removed from the female mold. The temperature is raised to the second temperature and the elastomer encapsulated foam male mandrel irreversibly shrink to less than about 0.5 its original size. Finally the shrunken male mandrel is removed from said composite component. These mandrels are a solution to the aerospace industry's flyaway mandrel problem as they are lightweight and can easily be removed from the composite component.

Removable irreversibly shrinking male mandrel

Growing community of inventors

E. Haven, CT, United States of America

Nicholas P Flonc