Hygrothermal Behavior of Carbon Fiber Fabric Reinforced Vinylester Resin Composite Structures

The hygrothermal aging of vinylester resin and its carbon fiber fabric-reinforced composite structures is examined here, focusing on moisture absorption and the consequent degradation of mechanical properties. Specifically, resin casting and CFRP (carbon fiber reinforced polymer) specimens were prepared and immersed into the deionized water and artificial seawater, respectively, at a temperature of 70 °C. Regular weight measurements were taken, accompanied by surface morphology observations using scanning electron microscopy (SEM) and identification of variations in functional groups through Fourier-transform infrared (FTIR) spectroscopy. Meanwhile, the mechanical properties of resin and CFRP were periodically checked. The gravimetric analysis results indicate that resin immersed in deionized water exhibits non-Fickian diffusion due to strong hydrolysis, while CFRP obeys approximately Fickian diffusion because of the embedded carbon fiber inhibiting the hydrolysis. The examination of mechanical properties for CFRP reveals that moisture absorption significantly influences interlaminar shear strength, resulting in a maximum reduction of 13.5%.