Efficiency of double-lapped composite joints in bending

Abstract

An analytical and experimental study was conducted to examine the mechanical behaviour of double-lapped adhesive-bonded joints subjected to bending loads. Adherends consisted of a U-shaped high-strength steel hub and a unidirectional composite of either B/AI or B/epoxy. Adhesives with a range of moduli and peel strengths were evaluated with and without bolts in regions of high stress concentration. Finite element analyses indicated high shear and normal stress concentrations at the end of the steel hub legs. Experimental testing of sample joints revealed that failure modes are controlled by the composite adherend material. Joints incorporating a B/AI adherend failed by adhesive peel in the region of high stress concentration. Delamination of the B/epoxy composite was the predominant failure mode of joints utilizing a B/epoxy adherend. Failure by delamination was suppressed by the insertion of high-strength bolts into the stress concentration region.