Adhesion promoting layer for composite assemblies

A method for making a composite part which comprises a composite material having a surface to which a gel coat is adhered, said method involving the use of an adhesion promoting layer to increase the adhesion between the gel coat and the composite material when said gel coat and composite material are cured at a temperature in the range of 60° C. to 90° C., said method comprising the steps of:

• providing a composite material having a first surface, said composite material comprising an uncured epoxy resin selected from the group consisting of diglycidyl ether of Bisphenol F and diglycidyl ether of Bisphenol A, a curing agent for said uncured epoxy resin comprising dicyandiamide and one or more accelerators for said uncured epoxy resin comprising, said one or more accelerators being selected from the group consisting of substituted ureas and substituted imidazoles, said composite material further comprising a fibrous reinforcement;
• providing a gel coat that is in a gelled state, said gel coat having a second surface and wherein said gel coat comprises a gelled epoxy resin;
• providing an adhesion promoting layer consisting of a fibrous element and a cure accelerating agent for said uncured epoxy resin selected from the group consisting of substituted imidazoles, salts of alkaline earth metals, azides, ureas, free radical initiators and amine salts of boron halogen complexes;
• placing said adhesion promoting layer between said gel coat and said composite material so that said adhesion promoting layer is sandwiched between said first and second surfaces;
• and
• curing said composite material and said gel coat at a temperature in the range of 60° C. to 90° C. wherein the uncured epoxy resin present in said composite material travels through said adhesion promoting layer to form an adhesion promoted epoxy resin that directly contacts the gelled epoxy resin of said gel coat in order to provide direct bonding of said gel coat to said adhesion promoted epoxy resin wherein the adhesion of said composite material to said gel coat is greater with said adhesion promoting layer being present than without said adhesion promoting layer being present.