Transverse Tensile Deformation and Failure of Three-dimensional Five-directional Braided Carbon Fiber Composites

Accurate characterisation of transverse tensile deformation and damage evolution is of importance for evaluating the failure behaviors of three-dimensional (3D) braided composites. In the present study, a finite element method (FEM) and several non-destructive testing methods including acoustic emission, digital image correlation, and infrared thermography are developed to investigate the transverse tensile deformation and damage evolution of 3D five-directional braided composites. In the finite element approach, a matrix-impregnated fiber bundles (MIFB) model and a representative volume cell (RVC) model, which take into account the fiber bundles and matrix, are respectively established to predict the effective mechanical properties of fiber bundles and simulate the deformation and progressive damage of such composites. The damaged locations and the failure modes including matrix crack, fiber debonding and shear fracture of fiber are predicted and verified by experimental tests. The non-destructive tests show that the transverse tensile fracture process can be divided into four stages which correspond to acoustic emission signals severally. The combination of the FEM based numerical modeling and multiple non-destructive characterisation methods can accurately monitor the deformation and damage behaviors of 3D braided composites under transverse tensile loads and thus provide a reference for structural health monitoring of composites in practical application.