The transition from out-of-plane to in-plane kinking due to off-axis loading

A comprehensive test campaign has been performed on coupon level to gain fundamental understanding of compressive failure in unidirectional NCF composites for aerospace applications. A subset of this study is focusing on the effect of off-axis loading, where a number of laminates have been tested with fibres oriented in off-axis angles in the interval 0-20\ub0 in steps of 5\ub0. Our hypothesis is that 0\ub0 laminates fail by kinking out-of-plane and as the off-axis angle is increased, there is a shift to in-plane kinking as the in-plane shear component increases. The contribution from this shear component on kinking will have little effect on the compressive strength until in-plane kinking becomes "dominant" over out-of-plane kinking. Preliminary results indicate a transition from out-of-plane to in-plane governed kinking to occur at an off-axis angle between 10\ub0 and 15\ub0