Crack propagation in lap shear joints

Abstract

A theory has been developed to explain crack propagation through a long elastic lap joint held under constant load. Verification of the theory has been achieved by direct observation of cracks through lap joints made from smooth, transparent rubber strips pressed together to give reproducible autohesion. Lap-joint strength was found to depend in the theoretically predicted manner on the adhesive energy of the bonded surfaces, measured by peeling tests, and on the thickness, width and elastic modulus of the adherend sheets. Application of these results to the design of practical lap joints has been discussed.