Biaxial tensile-compressive loading of unnotched and open-hole carbon epoxy crossply laminates

Although most tests on composites are conducted uniaxially, they are subjected to multi-axial loads in real-life applications. In this paper, the behavior of unnotched and open-hole unidirectional carbon epoxy crossply laminates under various off-axis biaxial tension-compression loadings is studied using a mixed experimental and numerical approach. Strain measurements made using digital image correlation technique in cruciform test specimens show overall good correlation with finite element predictions based on the micromechanics of failure theory and material property degradation method. It is shown that an aligned mesh concept where element edges are aligned with ply fiber direction is necessary for accurate prediction of progressive failure patterns. The finite element model is shown to be capable of predicting critical and sub-critical damage mechanisms governing failure in these laminates. Furthermore, the detrimental effect of off-axis loading and the introduction of an open-hole in carbon epoxy crossply laminates under the biaxial loading are investigated quantitatively.