Modified double cantilever beam test method for mode-I energy release rate of elastic adhesive layers

This study proposes a Mode I double cantilever beam (DCB) test method for debonding thick elastic adhesive layers. The approach integrates Bernoulli–Euler beams connected via spring elements akin to Winkler's foundation. Energy release rate determination considers crack length correlation with elastic deformation in the crack-front region, accounting for both beam rotation and lateral movement. Evaluation of Ti6Al4V samples bonded with FM 309 adhesive revealed higher initial energy release rates with the conventional beam theory and conservative values with the modified beam theory. The proposed method offered improved consistency, and less conservative energy release rate values compared to the modified theory.