A novel interface constitutive model for prediction of stiffness and strength in 3D braided composites

Owing to the excellent integrated mechanical properties, 3D braided composites have a broad range of engineering applications in aeronautics and astronautics industry. The interface is a critical constituent of 3D braided composites, which plays an important role in the control of mechanical properties of the composites. In this paper, a meso-scale finite element model considering the interface is established to numerically predict the stiffness and strength properties of 3D braided composites. A novel damage-friction combination interface constitutive model is utilized to capture the interface debonding behavior, while 3D Hashin criteria with maximum stress criteria and a gradual degradation scheme are applied to predict the damage evolution of yarns and matrix. A user-material subroutine VUMAT based on finite element package ABAQUS/Explicit is developed for these constitutive models. The stiffness and strength properties of 3D braided composites are derived from the calculated stress-strain curves under typical loading cases. The damage mechanism of constituents especially the interface is revealed in these simulation processes. The effects of the interface parameters on the mechanical properties of composites are investigated, which provides a reference for optimizing design and control of the interface properties of 3D braided composites.