Three-dimensional progressive damage and failure analysis of double-lap composite bolted joints under quasi-static tensile loading

Bolted joints are the dominant connection method in assembling composite structures. To investigate the failure mechanism of composite bolted joints under tensile loading, a three-dimensional progressive damage model for composite bolted joints was developed and implemented using the subroutine UMAT in Abaqus/Standard. This model considered several significant damage phenomena, such as the matrix crack orientation, the closure effect of matrix crack, and the longitudinal compressive responses of failed material under transversal constraints in the crush zone. The model utilized Hashin criterion for fiber fracture and Mohr–Coulomb based criterion for matrix cracking prediction separately. For validation of the model, a composite double-lap single-bolt joint configuration was adopted. The simulation results show high accuracy and precision compared with experimental results from the literature concerning inflection load, failure load, load–displacement response, and failure modes. Such a high-fidelity progressive damage model can overcome the inherent limitations of the experimental method. The bearing damage onset and propagation in the distinct plies and interfaces were investigated in detail at different load levels. It was found that matrix cracking initiates the joint damage onset and triggers fiber fracture. The initiation of interface delamination was identified as the mechanism by which the load–displacement response becomes nonlinear. The study revealed that matrix cracking is the dominant failure mode and induces the final rupture of the joints.