Study on the interlaminar high/low temperature tensile properties and failure mechanisms of carbon fiber Z-pin reinforced high-temperature resistant bismaleimide composites

The Z-pin reinforcement technology can significantly improve the interlaminar properties of composite laminates. However, there is still a notable deficiency in current research on evaluating the interlaminar tensile strength of components at high/low temperatures based on the four-point bending test method. This paper investigates the influence of the diameter and volume content of Z-pins on the interlaminar tensile strength of BMI composite laminates at different temperatures. Additionally, it analyzes the interlaminar reinforcement mechanism and crack propagation mechanism of Z-pins in BMI composite laminates in conjunction with a finite element model. The research results indicate that the increase in Z-pin diameter and volume content significantly improves interlaminar tensile properties. In terms of temperature effects, the implantation of Z-pins at room temperature enhances interlaminar tensile strength by up to 3.52 times, demonstrating the most pronounced strengthening effect. Under low-temperature conditions, the strength increase is 191 %, with a reduced strengthening efficiency. Notably, high temperatures lead to a significant increase in material crack density, weakening the bridging effect of Z-pins. Additionally, based on finite element simulation results, the crack propagation path is predicted, and the multi-scale reinforcement mechanism of Z-pins in laminated plates is elucidated. The aforementioned research provides critical design guidelines for optimizing the interlaminar performance of Z-pin reinforced curved structural components under different temperature conditions.