Phase-field simulation of microscale crack propagation/deflection in SiCf/SiC composites with weak interphase

To understand the microscale toughening mechanism, the crack propagation, and stress-strain response of unidirectional SiCf/SiC composites with h-BN interphase under transverse and longitudinal tension are investigated by a promising micromechanical phase field (PF) method along with representative volume element. Of much interest, the calculation results are well consistent with the available experimental results. With a strong dependence on the interphase strength, the toughening mechanisms during crack propagation are well presented, for example, fiber pull-out, crack deflection, and interphase debonding. Furthermore, the longitudinal tensile strength of SiCf/SiC composites increases with decreasing the interphase strength, where only a weak enough interphase can result in a significant crack deflection by its cracking. In particular, the ratio of the interphase strength along fibers to the matrix strength should be less than 1.254 to ensure crack deflection in the interphase and fiber pull-out. Moreover, the transverse tensile strength of SiCf/SiC composites reaches a maximum with increasing the interphase thickness into the range of 0.25-0.5 mu m.

Automated summary

This study investigates the microscale toughening mechanism, crack propagation, and stress-strain response of unidirectional SiCf/SiC composites with h-BN interphase under transverse and longitudinal tension using a micromechanical phase field (PF) method and representative volume element. The calculated results are in good agreement with experimental results. Different toughening mechanisms, such as fiber pull-out, crack deflection, and interphase debonding, are observed depending on the interphase strength. The longitudinal tensile strength of SiCf/SiC composites increases with decreasing interphase strength, and a weak interphase is required for significant crack deflection. The transverse tensile strength reaches a maximum with increasing interphase thickness between 0.25-0.5 μm.