Stiffness behaviour due to fracture in adhesively bonded composite-to-aluminum joints II. Experimental

Experimental testing of composite-to-aluminum single-lap joints has been performed to verify the theoretical model proposed in Part I. Using specimens bonded with a flexible and a rigid adhesive, tests were conducted at room temperature and −40°C. Results show that the joint stiffness is more affected by the response of the adherends to the test temperature than by the modulus of the thin adhesive layer. It is found that the theoretical model is able to predict the joint stiffness and the rate of stiffness loss with crack growth. The best correlation is found for the rigid adhesive joint tested at −40°C in which the fracture mode is pure adhesive cracking. Since the model does not account for other failure modes such as delamination and interfacial tearing, the stiffness loss due to such failures is underestimated.