United Technologies Corporation

Nestor J Diaz

Robert L Faiz

William C Reinfelder

David J Parker

James H Ewen

A method for fabricating composite structures wherein a single mold is used to preform a foam core between fiber reinforcement plies that are subsequently subjected to resin transfer molding to form an integrated foam core composite structure having the formed foam core mechanically interlocked to the composite skins. Fiber reinforcement plies are layed up on contoured molding surfaces of dies to define a core cavity with the mold closed. Foam is injected into the core cavity, concomitantly penetrating the fiber reinforcement plies, and allowed to cure to form the foam core. Heat and pressure generated during foam cure compresses the fiber reinforcement plies to provide debulking therefor. A resin binder is injected into the mold plenum to impregnate the layed-up fiber reinforcement plies, and the formed foam core/resin-impregnated layed-up fiber reinforcement plies are subsequently cured to form the integrated foam core composite structure. Film barriers may be formed in the fiber reinforcement plies to limit penetration of the injected foam to a predetermined number of fiber reinforcement plies. The film barriers may be melted and fused with the injected resin to provide an adhesive bond between the formed foam core and the composite skins, in addition to the mechanical interlock therebetween, to provide an integrated foam core composite structure with superior integrity.

In-situ molding of fiber reinforced composites to net shape

A method is disclosed for the stabilized cutting of a stack of fibrous composite sheets (1) assembled into a preform (3). The method includes the steps of providing a plurality of fiber sheets; applying a binder (2) to each sheet, with the binder comprising a low weight fraction of the sheet and being noninhibitive to resin flow during molding; and stacking the sheets in a particular orientation and cutting the sheets to a desired pattern using a laser cutting system (5) which may include a computer control module (8) loaded with a digitized pattern of the desired contour. As the laser cuts the fabric sheets, the cut ends fuse with the binder rather than with each other, thereby preventing cross-fusing of the fibers and maintaining resin permeability at the sheet ends. With this method, a low cost, highly automated and repeatable process may be provided for producing fiber preforms without labor intensive multiple sheet cutting and cross-stitching, while avoiding frayed or unraveled sheet edges.

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Seymour, CT, United States of America

Nestor J Diaz