Parametric characterisation of z-pin reinforcement using high-definition FE modelling

A high-fidelity model of a through-thickness reinforced composite with a z-pin was generated in order to study and characterise the increase in damage tolerance brought by this type of reinforcement. A coupled cohesive-friction interface model was developed and implemented to characterise the frictional behaviour between the z-pin’s surface and the composite during the different stages of damage propagation. A thermo-visco-plastic constitutive model is used to model the epoxy behaviour. Behaviour of the z-pin is captured considering a non-linear shear deformation formulation and failure is triggered by a maximum tensile failure and maximum longitudinal shear failure criteria. Highfidelity of the geometry of the model is achieved thanks to an automated script capable of reproducing all geometrical features of the through-thickness reinforcement. Different loading conditions (tension and/or shear) representing different mode-mixities were applied to the model and the apparent increase in toughness, as well as the different phenomena leading to this increase were captured. The study was repeated for different sets of parameters in the model so that the influence of each parameter could be identified. A more reliable design of experiments is envisaged with this information, especially in a high-rate testing regime.