Understanding the effect of anisotropy in composite materials on the performance of cruciform specimens

The anisotropic nature of fibre-reinforced composite materials is often not accounted for during the design process of composite cruciform specimens. Here, the response of cruciform specimens depends on both - the layup configuration and the variations in the biaxial loading conditions. This work studies the effect of anisotropy in composite materials on the uniformity of the developed multi-axial stress state in cruciform specimens.

For that, a combination of 3D finite element and analytical models are used to analyze the behaviour of 12 different cruciform specimen geometries consisting of different layups and subjected to different biaxial loading conditions. In this study, it is shown how the shape of the gauge zone, the shape of the corners formed by the adjacent arms and the presence of slots in the arms can be used to design cruciform specimens with uniform stress states in the gauge zone, while accounting for the varying anisotropy.