Numerical modelling of woven composites: Biaxial loading

A numerical model of a 2 × 2 twill reduced Unit Cell was developed. The elasto-plastic response of the matrix and possibility of tow/matrix debonding were modelled. The material is assumed to fail after failure of the tows is detected using maximum-stress and/or physically-based failure criteria. The support provided by the adjacent layers was accounted for considering two idealised cases of support: In-Phase (IP) and Out-of-Phase (OP); which bound the support a given layer can have within a laminate.The difference in results between IP and OP provides an estimate of the expected variation in strength due to the support. Additionally, the failure strength predictions obtained averaging the IP and OP results agree well with experimental results for uniaxial tension/compression.The in-plane biaxial failure envelope was also determined. A strong correlation was found between the loading ratio and the effect of support provided by the adjacent layers on the failure strength.