Mesoscale modelling of damage in single- and double-shear composite bolted joints

This paper presents the development and validation of a mesoscale numerical model for predicting damage and failure of bolted joints in laminated composites with different configurations and geometries. Double-shear and single-shear composite bolted joints with different widths and end distances were analyzed. The composite material model combined smeared crack models for all types of intralaminar failure mechanisms, and an interface discrete cohesive-zone model for interlaminar failure. Three dimensional (3D) phenomenological invariant-based failure criteria using in-situ ply strengths were used for the prediction of intralaminar damage onset, together with mechanism-based continuum damage models (longitudinal bi-linear damage model and transverse 3D smeared crack model) for intralaminar damage propagation. An interface cohesive-zone model with consistent initiation and evolution criteria based on the Benzeggagh-Kenane (B-K) law was used to simulate delamination. Particularly, for the first time, the model considered the inherent cohesive-frictional behavior in the intralaminar transverse failure and delamination, namely the frictional sliding in diffuse micro-cracks during damage propagation and in localized meso-cracks after complete fracture. In the 3D explicit finite element models, a fiber-aligned mesh was used for the discretization of composite plies. A multi-zone modelling strategy was used to make the computational cost acceptable for engineering applications. Detailed comparisons between the numerical results and the experimental data previously obtained were performed, with focus on the macroscopic mechanical behavior and mesoscale failure mechanisms. A good correlation between tests and analyses was found. Additionally, several complex failure mechanisms were revealed by the numerical simulations, which could not be clearly identified in previous experimental studies.