Effects of Defects on Effective Material Properties of Triaxial Braided Textile Composite

In this study, the effects of defects in a triaxial braided textile composite was studied at unit cell level using three-dimensional finite element analysis. The manufacturing defects such as void defect and tow misalignments were considered in the model and the effect of their presence at different scale on the effective material properties were studied. The configuration of the finite element model was based on the geometric data extracted from an experimental test specimen. The representative unit cells (RUC) that repeat itself to build the whole braid were sliced out from the full interlaced geometry of axial and bias tows. Periodic boundary condition (PBC) was used to simulate the repeating nature of the unit cells. Then, numerical tests were performed to compute three-dimensional effective material properties for triaxial braided RUCs with predetermined void volume fractions and axial tow misalignment under uniaxial tension and shear loadings in different directions. It was observed that the void defects severely affected the out-of-plane properties of the material, while the tow misalignments influenced the axial modulus mostly.