On the influence of fabric layer shifts on the strain distributions in a multi-layer woven composite

The influence of the relative shift between fabric layers on the local strain distributions at the mesoscopic scale of a four-layer plain weave glass fiber/epoxy matrix composite is studied through Finite Element (FE) modeling. The surface strain fields of several representative unit cells, consisting of compacted and nested plain weave layups with different layer shifts and the matrix complement, are compared to strain fields measured experimentally by digital image correlation. The layer shifts only have a small impact on the calculated homogenized macroscopic mechanical properties. However, the local strain fields are influenced significantly. Good quantitative agreement is obtained between the measured surface strain distributions and the numerical results if the layer shifts of the tested specimen are used in the FE model. The most frequently used models without layer shifts or with maximum nesting do not provide satisfactory surface strain distributions.