Theoretical analysis of crack propagation in composite DCB specimens

Based on the elastic foundation beam model, the bilinear cohesive constitutive relation was introduced through the relationship between the deflection and the relative displacement, unified description of interface damage state through the interface damage factor was used, and the damage cohesive zone was taken into account in the crack tip and the general solutions of each segment of double cantilever beam(DCB) specimen were found. The integral constant was solved with the continuity boundary conditions, and the load-displacement curve was obtained with of crack length and the cohesive zone range as the variables, thus DCB specimen crack propagation process was obtained. To verify presented theoretical analysis, in which the nonlinear phenomenon after elastic segment and the effect of the three cohesive parameters were considered simultaneously, some comparisons were made with the existing theoretical results. The effect of three interface parameters on the DCB specimen load-displacement curve was investigated, and the results provide the basis for the selection of interface parameters. The relationship between interface parameters and cohesive zone length was given.