Characterization of fibre kinking behaviour in thin plate composites at different loading rates

This study investigates the fibre kinking behaviour of thin plate composites subjected to quasi-static and dynamic loading conditions, with particular emphasis on the influence of specimen dimensions and surface ply orientation. Small Compact Compression (SCC) specimens, featuring surface plies oriented at either 0° or 90°, were evaluated using an in-situ rig and an electromagnetic Hopkinson bar system. High-speed imaging and computed tomography (CT) scans revealed that dynamic loading significantly enhanced the fracture toughness to approximately 100 kJ/m², in contrast to roughly 30 kJ/m² observed under quasi-static loading. This increase in toughness is attributed to localized energy dissipation. The SCC specimens exhibited lower toughness under quasi-static loading but demonstrated superior toughness under dynamic conditions compared to the Compact Compression (CC) specimens, thereby underscoring the size effect. The 90° surface ply orientation facilitated earlier detection through matrix cracking, while the 0° ply orientation directly indicated fibre kinking. These findings underscore the importance of incorporating rate-dependent models and size considerations in the design of composite materials.