A new integrated modeling method for investigating the impact of cure process on the compressive response of z-pinned CFRP laminates

The application of z-pinning significantly enhances the interlaminar performance of carbon fiber reinforced polymer (CFRP) composites. However, the insertion of z-pins can induce fiber distortion with the formation of resin-rich regions, which may compromise in-plane mechanical properties. This study considers the influence of the cure process on the in-plane compressive behavior of z-pinned laminates. A novel micromechanical model is proposed that incorporates temporal material curing properties. The model employs a cohesive element approach with a bilinear constitutive law to accurately simulate interactions within the z-pins and resin-rich regions. As a consequence of pronounced discrepancies in thermal expansion and chemical shrinkage, substantial residual stresses develop around the z-pins following curing. Under compressive loading, the interface with reduced mechanical integrity is prone to initial crack formation, with progressive damage that is propagated into adjacent resin-rich areas. In addition, a parametric analysis has been conducted to evaluate the effects of various z-pin diameters and z-pin densities on the in-plane compressive characteristics, offering valuable insights for optimizing high in-plane mechanical performance.