BENCHMARK TESTS ON ADHESIVE STRENGTHS IN BUTT, SINGLE AND DOUBLE LAP JOINTS AND DOUBLE-CANTILEVER BEAMS

The RC99 committee of the Japan Society for Mechanical Engineers condu cted the benchmark tests on strengths of adhesive joints using differe nt testing methods. The effects of joint configuration, loading mode, adherend yield strength and so on, on the strength and data scatter we re investigated using two typical epoxy adhesives. The strengths obtai ned by various tests were compared with each other. The relationships among strengths of butt, single lap and double lap joints and fracture toughness were given. Thirteen member institutes of the committee par ticipated in this project. The benchmark results allow us to recognize that the joint strengths are strongly affected by the curing process. The key to obtaining the appropriate joint strength, is precise tempe rature control inside the adhesive layer for curing. Toughened adhesiv es do not always give higher joint strengths than untoughened adhesive s. The yield strength of adherends much affects the observed lap joint strength of adhesives.