Progressive damage modeling of an adhesively bonded unidirectional composite single-lap joint in tension at the mesoscale level

This study investigates initiation and propagation of damage zones in the composite plates of an adhesively bonded single-lap joint in tension at the mesoscale level. A set of material degradation rules is applied to the mechanical properties of each failed ply of the plates based on the Hashin failure criterion. The von Mises stress concentrates along the free edges of the adhesive layer and the corresponding lower and upper plate regions and peaks along the free edges of the adhesive-plate interfaces. Consequently, the damage initiates at the lower plate interface to the adhesive layer and propagates in the first ply along this adhesive free edge, and then spreads through the neighboring plies of the lower plate in a similar failure mechanism. The damage in the lower plate occurs in the matrix, delamination, and fiber-matrix failure modes, and the first ply-failure loads decrease significantly with increasing ply fiber angle. Tension tests showed that the adhesive joints with ply lay-ups between [0](10) and [15](10) fails through the adhesive layer, and the lower plates with larger fiber angles break along the free edge of the lower plate-adhesive interface whereas the adhesive layer is still intact. The adhesive failure is interfacial around the adhesive free edges and is through the adhesive in the middle of the overlap region in the joints with the ply lay-ups [0](10). Although a similar failure mechanism is observed in the ply lay-up [15](10), the damage zones in the first ply of the lower plate in which the matrix and fibers are damaged, are distributed in the overlap region. The damage is initiated in the first ply of the lower plate of th