Mechanical Stability of Carbon/Ramie Fiber Hybrid Composites Under Hygrothermal Aging

Hybrid composites containing carbon fibers and ramie fibers in an epoxy polymer matrix were prepared (denoted as CRFRP), after which the composites were immersed in distilled water at three different temperatures (20, 40, and 60 °C) for a period up to 2 months. Water absorption tests and static (tensile and flexural) and dynamic (low-velocity impact) mechanical tests were then conducted on the hygrothermally-treated composites to explore their hydrothermal aging mechanism. Results show that water uptake by CRFRP composites was enhanced by increasing the hygrothermal treatment temperature or aging time, with the water uptake obeying a Fickian diffusion model. Hygrothermal aging decreased the tensile strength, tensile modulus, flexural strength and flexural modulus of the CRFRP composites, though enhanced the impact absorption energy since the ramie fibers had greater plasticity and deformability after aging. Based on the experimental findings, a plausible mechanism was developed for the hydrothermal aging of the hybrid composites. Importantly, CRFRP composites were lighter than carbon fiber-reinforced composites (CFRP), whilst offering similar all-round performance, suggesting CRFRP composites may be useful in applications where CFRP composites have traditionally been used.