Investigation of the hygrothermal effects on in-plane failure mechanisms of fine Z-pinned laminates

Hygrothermal effect on the in-plane behavior of fine Z-pinned laminates were studied and the failure mechanisms were explained. Artificial seawater aging experiments were carried out on Z-pinned laminates prepared by ultrasonic vibration equipment. A compression progressive damage numerical model of fine Z-pinned laminates based on moisture-induced interface degradation was proposed to analyze the damage initialization and development of composites. The mechanical results show that the unpinned and Φ0.11 mm Z-pinned laminates have similar in-plane strength retention after 6 months of aging, and the tensile and compressive strengths decrease by 20% and 29%, respectively. EDS analysis confirms that Z-pin provides an additional moisture channel, leading to more elements with high relative atomic mass inside the laminates. It is found through the simulation studies that moisture leads to matrix compression and interlaminar interfacial damage regions to localized areas, weakening the interlayer effect of Z-pins and leading to the decrease of the ultimate bearing capacity of laminates. It denotes that Φ0.11 mm fine Z-pin has the potential to be used in composite marine structures.