United Technologies Corporation

Robert L Faiz

Donald L Ferris

Nestor J Diaz

Edward S Hibyan

Philip J Ramey

William C Reinfelder

David J Parker

Nicholas P Flonc

Dean Nguyen

Kenneth M Adams

William J Walker

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.

Method for stabilized cutting of fibrous 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

A helicopter rotor having one or more blades mounted for rotation with the rotor hub and each supported therefrom by an elastomeric bearing, and having a lead-lag damper connected to the blade and the hub and extending substantially parallel to the blade axis, and including the improvement of apparatus for preventing tension loading of the elastomeric bearing as the blade moves radially inwardly as a result of rotor braking.

Elastomeric helicopter rotor load reaction system

Pitch control linkage for the upper rotor of coaxial counterrotating rotors utilizes conventional swashplate, control rod and servomotor elements for changing blade pitch but without the conventional rotating and non-rotating scissors for reacting swashplate torque. This is accomplished by the use of rotating and non-rotating walking beams and combination torque reacting control rods between the walking beams and the rotatable and non-rotatable swashplate elements. Means are also disclosed for shimming the rotatable walking beams to achieve pre-track adjustment of the pitch of individual blades.

Growing community of inventors

Sandy Hook, CT, United States of America

Robert L Faiz