Instabilities in Braided Textile Composites Under Uniaxial Compressive and Biaxial Loadings

Abstract

This paper discusses the results of a finite element (FE) based study of the multiaxial compressive instabilities in braided glass fiber composites. The micro mechanics study was carried out on a 2-unitcell size 3-D FE model. Computational tests were carried out to first determine the elastic moduli of the system. Once the computational model was validated with experimental data for the elastic moduli, the uniaxial compressive response of the micromodel was established using the RIKS option available in the ABAQUS commercial FE code. Subsequently, the response of the micromodel to biaxial loading was investigated. The present approach is different from those reported in the literature where classical methods based on the technique of homogenization is used to model the elastic and inelastic response of braided composites. In this work, explicit account of the braid microstructure (geometry and packing) and the inelastic properties of the matrix are accounted for via the use of the FE method. The macromechanical data pertaining to the braided composites were obtained through traditional means. Tensile tests were performed on the composites through the use of ASTM D 3039 standard to obtain the macroscopic orthotropic moduli and macroscopic response. For each test, the average data is reported in this paper. A separate test was conducted to obtain the in-situ matrix properties of the braided glass composites. The computational model provides a means to assess the compressive and biaxial strength of the braided composites and its dependence on various microstructural parameters. It also serves as a tool to assess the most significant parameter that affects compressive strength.