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Bridging mechanisms of through-thickness reinforcement in dynamic mode I&II delamination Part A Applied science and manufacturing

Cui, Hao, Yasaee, Mehdi, Kalwak, Gordon, Pellegrino, Antonio, Partridge, Ivana K., Hallett, Stephen R., Allegri, Giuliano, Petrinic, Nik
Composites 2017 v.99 pp. 198-207
composite materials, delamination, energy, friction, thermodynamics
Z-pin through-thickness reinforcement is used to improve the impact resistance of composite structures; however, the effect of loading rate on Z-pin behaviour is not well understood. The dynamic response of Z-pins in mode I and II delamination of quasi-isotropic IM7/8552 laminates was characterized experimentally in this work. Z-pinned samples were loaded at both quasi-static and dynamic rates, up to a separation velocity of 12m/s. The efficiency of Z-pins in mode I delamination decreased with loading rate, which was mainly due to the change in the pin misalignment, the failure surface morphology and to inertia. The Z-pins failed at small displacements in the mode II loading experiments, resulting in much lower energy dissipation in comparison with the mode I case. The total energy dissipation decreased with increasing loading rate, while enhanced interfacial friction due to failed pins may be largely responsible for the higher energy dissipation in quasi-static experiments.