EFFECTS OF THE ENVIRONMENT AND CURING ON THE STRENGTH OF ADHESIVE JOINTS

The influences of four parameters - pretreatment of the adherend, curi ng cycle, time before testing, and humidity - on the strength of adhes ively-bonded single lap joints were investigated for aluminium 2024-T3 adherend and modified epoxy FM73M adhesive. The importance of conditi oning the aluminium surface prior to bonding was confirmed. Furthermor e, the pretreatment should be attuned to the environmental conditions under which the joint will be used. We found that roughening the alumi nium surface gave a poorer joint strength. Cooling joints in normal en vironmental conditions after the curing procedure gave satisfactory st rengths if a relaxation period of 30 days was allowed before loading. The fitting of the experiments to a statistical distribution was exami ned to allow use of the experimental results for finite element techni ques with probabilistic models. The same statistical behaviour as that for joints submitted to cyclic loading was found for joints submitted to humidity.