Effects of substrate materials on fatigue crack propagation rate of adhesively bonded DCB joints

摘要

The effect of substrate materials on the fatigue crack propagation rate was investigated by using adhesively bonded DCB specimens with CFRP and aluminum substrates. The experimental results showed that the fatigue threshold for the aluminum joint was over three times as higher as that for the CFRP joint whose flexural rigidity was nearly equal to the corresponding aluminum joint, and that the increase m the thickness of the adherend lowered the fatigue threshold, irrespective of the substrate materials. To elucidate the fatigue crack propagation behavior, fracture surface observation and finite element analysis were conducted. Besides, Gurson's model was applied to the adhesive layer. The SEM images showed that numerous voids formed in the fracture surface for the joints with aluminum subsfrate, whereas appearance and growth of the voids were suppressed for the joints with CFRP substrate. The FEM results also showed that the high void-fraction area for the joint with aluminum subsfrate was greater than that with CFRP subsfrate. Thus, the above experimental and analytical characteristics of the voids evolution corresponded to the frends of the fatigue crack propagation behavior.