A COMPOSITE PREFORM
Publication Date: 2002-Mar-14
The IP.com Prior Art Database
The paper discloses a molding material of one or more layers which has a discontinuous resin layer on at least one surface of the reinforcement and which has a porous separator between the reinforcement and the resin layer.
The invention comprises a molding material having a reinforcement material of one or more layers and having a discontinuous resin on at least one surface of the reinforcement and having a porous separator between the reinforcement and the resin. The separation of the resin layer from the reinforcement layer using a porous separator provides improved resin content control, better removal of gases during the curing process and the ability to incorporate a porous separator having characteristics which provide unique properties to the final composite structure.
The present invention relates to a fiber-reinforced composite and method of making. In particular it relates to a preform which is partially impregnated and with heat and pressure is subsequently cured to form a composite structure. In particular, the invention relates to the use of a partially impregnated preform comprising a porous separator and a resin layer on one or both faces of a reinforcement layer.
The use of resin reinforced fibers has been used for many years especially in the aircraft, aerospace and other industries where weight savings are particularly needed. Fiber reinforced composites have traditionally been cured sheets or multiple sheets to form a laminate which have been created using fabrics preimpregnated with a resin. The preimpregnated sheets are commonly referred to as a “prepreg” and are usually stacked as separate sheets on a tool and heat and pressure are applied to produce a cured composite structure. The heat and pressure can be applied with an autoclave, a heated flat or contoured forming tool or a combination of methods including the use of a vacuum bag. The fibrous material can be a woven, non -woven and are typically glass, carbon or polyaramid.
Although having been used for some time, the lay-up of prepreg has certain disadvantages. The placement of each sheet in a multiple ply lay-up is a costly and labor intensive process. In addition, the removal of gases trapped between the individual plies during the lay-up process and the gasses produced in the lay-up during the curing process are difficult to remove. These gases produce voids in the cured laminate and result in reduced mechanical properties of the composite structure. The removal of gases during cure is sometimes referred to as devolatilization and has been addressed using various techniques. One such technique is to minimize the B-staging or partial curing of the prepreg so that a lower viscosity of the resin during the initial stages of final curing will allow the gasses or volatile materials to pass from the inner plies of a multi-ply laminate to the laminate surface more easily. This often results in too low initial resin viscosity and allows the resin to flow out of the laminate sandwich resulting in a low resin content which results in poor mechanical properties of the cured composite. Another attempt to address devolatilization of a prepreg material is to modify t...