Process-structure-performance modelling and progressive damage analysis of 3D rotary-four-directional rectangular braided composites under tensile load

Abstract

The mechanical properties of braided composites are sensitive to the braiding process. However, the relations between process parameters, yarn structures and mechanical properties of three-dimensional (3D) rotary braided composites have not been investigated. In this study, we aim to establish a model capable of characterizing the yarn structures and mechanical properties of 3D rotary braided composites by treating braiding angles as primary variables. Carrier motions on the bedplate were traced by mathematical functions, where corresponding yarn spatial paths within a representative volume element (RVE) were explored. A parametric finite element model (FEM) of 3D rotary-four-directional (3DR4d) braided composites was established considering realistic yarn cross-sections. A progressive damage model was used to predict the mechanical performance of the composites. Experiments were conducted to verify the proposed model. The results show that the ideal yarn topology of the rotary braided composites is similar to the lattice structure. In addition, the longitudinal tensile modulus and strength of 3DR4d braided composites increase with the decreased braiding angles, while increasing with the increased fiber volume fractions. According to damage analysis, longitudinal tension and transverse shear are the dominant failure modes of 3DR4d composites with small and large braiding angles, respectively.