Numerical analysis on interface damage mechanisms of 3D four-directional braided composites

Considering the effect on material interfacial mechanical properties caused by friction which appears on the debonding interface under compression stress, a damage-friction combination interface constitutive model was proposed. Then a user material subroutine VUMAT involved this constitutive model was developed and implemented in finite element software ABAQUS. In conjunction with the damage-friction interface combination constitutive model, a meso finite element model of 3D four-directional braided composites based on the periodic unit-cell was established. In the unit-cell model, the interface element was introduced in the yarn/matrix and yarn/yarn interfaces. The initiation and propagation of interface damage under typical loads were simulated, and the mechanisms of interface stress transfer and interface failure were revealed. The effect rule of interface properties on macro- and micro- mechanical properties of composites were studied, which provides a reference for optimizing design and control of the interface performance of 3D four-directional braided composites.