Distribution characteristics of interface cracks in composite materials under mixed-mode loading

Current theoretical models exhibit limited predictive accuracy in describing interface debonding behavior under non-uniaxial loading conditions, primarily due to the omission of critical modeling parameters such as the characteristics of interface crack distribution. Consequently, obtaining comprehensive and detailed observation data of interface crack has become pivotal for addressing this challenge. This study employs off-axis tensile testing as a representative non-uniaxial loading scenario, using oblique cross-shaped specimens as research objects. Three dimensional image characterization of interfacial structures was conducted using Micro-CT technology. For specimens subjected to tensile-dominated or shear-dominated loading conditions, the area ratio of debonding zones on fiber surfaces was measured, with analysis focusing on axial and circumferential variation patterns. Experimental results demonstrate that the interface crack distribution under non-uniaxial loading is predominantly influenced by the load magnitude, loading mode, and fiber orientation. Subtle adjustments to the tensile-to-shear stress ratios may significantly alter the uniformity and randomness of the crack propagation patterns.