Experimental and numerical investigations on the mode I delamination growth behavior of laminated composites with different z-pin fiber reinforcements

Z-pinning can effectively improve delamination growth resistance of fiber reinforcing laminated composites and attracts much attention. Material and geometrical characteristics of z-pins have effects on the delamination behavior. Numerous studies have been conducted to investigate the effect of volume fraction, diameter, shape, surface treatment and angle of z-pin, insertion length and areal density. However, the effect of elastic modulus of z-pins on the delamination behavior is still lack of investigation. In this work, the delamination behavior of two kinds of z-pinned laminates is experimentally and numerically studied. The laminates are reinforced by z-pins with different elastic moduli, including carbon fiber pin and polyimide fiber pin. It is found the elastic modulus of z-pins has effects on the steady-state fracture toughness, the bridging zone length and the micro failure mechanism. A bilinear cohesive zone model is applied for the simulation of delamination in composite laminates and discrete nonlinear spring elements are used for the characterization of the mechanical behavior of z-pins. The FE model is validated by comparing the predictions with the experimental results. Validated FE model is further applied to numerically investigate the density, the distribution distance and the distribution form of z-pins on the mode I delamination behavior.

Automated summary

This study experimentally and numerically investigates the effect of different elastic moduli of z-pins on the delamination behavior of laminated composites. It is found that the elastic modulus affects the steady-state fracture toughness, bridging zone length, and micro failure mechanism.