Electron beam curable adhesives for out-of-autoclave bonding of large composite structures

Adhesive bonding coupled with autoclave curing is widely used in the aerospace industry to produce large composite structures with complex core structures. Electron beam (EB) curable adhesives have the potential to replace thermally cured aerospace adhesives in bonding large integrated structures in fewer steps, at reduced cost and without autoclave processing. The ability to bond large aerospace structures has been advanced by recent improvements in EB-curable adhesive systems, but additional development is needed to meet the most stringent primary structure strength, toughness and use-temperature requirements. This paper presents results of mechanical and environmental adhesive testing of EB-curable paste and film adhesives. Formulation information and electron beam cure conditions required for optimum adhesive performance is also discussed. Lap shear strengths of 27 to 39 MPa (3900 to 5600 psi) were attained with paste adhesives on primed aluminum and carbon fiber composites, as well as T-peel strengths on primed aluminum of 10-25 pli.