Comparison between 2D and 3D fiber-matrix debonding simulation for inverse identification of interface fracture properties

Fiber-matrix debonding in single fiber specimen is studied experimentally and numerically based on the coupled criterion for which various 2D and one 3D configurations are used. Debonding initiation and propagation are mainly due to normal opening stresses in a 3D model whereas shear stresses play a minor role contrary to a 2D front model, i.e. in a plane normal to the fiber main axis. The 3D model enables describing the free surface singularity similarly to a 2D side model, i.e. along the fiber main axis. The latter cannot represent the debonding arrest and stable propagation after initiation. Overall, a 2D front model under plane strain assumption provides the best description of debonding initiation loading level compared to the 3D model, yet for a larger debonding opening. Experimental debonding openings are determined using DIC, providing the debonding initiation remote loading and corresponding opening. Tensile strengths and critical energy release rates respectively slightly higher and in the same order of magnitude are identified in 3D, based on the debonding opening, compared to a 2D front model.