Influence of in-plane shear on kink-plane orientation in a unidirectional fibre composite

Journal article, 2019

Kink-band formation is the governing failure mechanism for compressive failure of fibre reinforced composites. Here, kink-plane orientation, describing the direction of kink-band formation, is studied using X-ray computed tomography (CT). Unnotched unidirectional specimens with off-axis angles ranging from 0° to 20° are tested in compression. The measured compressive strength is found practically constant for off-axis angles between 0° and 10°. For an off-axis angle of 15° the compressive strength drops dramatically. CT-results reveal this drop to be consistent with a transition from out-of-plane to in-plane dominated kinking. Furthermore, results show the kink-plane angle to be linearly dependant on off-axis angle, and hence in-plane shear stress. A three-dimensional finite element model considering measured fibre misalignment angles through its volume is generated for numerical analysis. Numerical predictions based on the LaRC05 kinking criterion are found to qualitatively capture the experimentally observed effects of off-axis angle on kink-plane orientation