Micro-CT based trans-scale damage analysis of 3D braided composites with pore defects

Pore defects that inevitably produce during the manufacturing process, have distinct effects on the mechanical properties of 3D braided composites. A trans-scale method coupled with Micro-CT is developed to investigate the strength and damage behavior of 3D braided composites with pore defects. Pore defects and yarns are measured by Micro-CT and reconstructed. Then, the trans-scale finite element models are established on the Micro-CT data. The progressive damage model and cohesive-zone model are applied to simulate the damage behavior of braided composites, and effects of interface strength are also investigated. Effective properties of yarns are predicted by the micro-scale analysis and then transferred to conduct the meso-scale analysis. The meso-scale finite element model can predict the stress-strain response well, which has been validated by experiments. The failure modes of yarn damage, matrix cracking and interface debonding are recognized and correspond well with the final failure morphology of the sample. The damage appears around the pore defects and then develops to the weak region in the matrix. The interface properties show diverse influences on yarns and braided composites under different loading conditions. As experimentally demonstrated, the present research scheme can well capture the void features, and therefore efficiently predict the tensile behavior of 3D braided composites considering pore defects.