Study on failure criterion and microscopic damage evolution mechanism of three-dimensional braided composites

Due to the complex meso-structure of three-dimensional multidirectional braided composites, capturing the process and mechanism of damage evolution through experiments alone is challenging. To address this, a finite element framework based on various failure criteria was developed to study the meso-scale progressive damage evolution of 3D four-directional braided composites under tensile and compressive loads. In this study, a three-unit cell model was employed to characterize the microstructure of the braided composites, which was established based on the braiding process parameters and yarn trace distribution. Three types of typical failure criteria and corresponding stiffness degradation models were integrated into the finite element framework to investigate the mesoscale progressive damage evolution of the braided composites. Uniaxial tensile and compression simulations on the representative cell of the braided composites revealed the evolution of strength and failure mechanisms. The simulation results indicate that the LaRC05 scheme effectively captures the shear nonlinearity and the interaction between fiber and matrix in braided composites under uniaxial compression load. For 3D four-directional braided composites, transitioning from a tensile state to a compressive state results in a shift in the failure mode of the material, from fiber fracture to fiber kinking and fiber splitting. Therefore, to establish a more accurate failure criterion, it is crucial to fully consider the influence of failure modes and physical mechanisms.