Hygrothermal aging behavior and mechanical degradation of ramie/carbon fiber reinforced thermoplastic polymer hybrid composites

Hybrid multi-fibers reinforced thermoplastic polymer composites with reasonable structure design can maximize their physical or chemical properties to obtain outstanding comprehensive properties. To broaden the industrial applications and understand the properties of natural ramie fiber product, the hygrothermal aging behavior and flexural properties of the ramie fiber and carbon fiber (R/C) reinforced polyethylene terephthalate glycol hybrid composites with different lay-up sequences were investigated with 90-days water aging. The finite element analysis model was established to reveal the moisture diffusion evolution and the hygrothermal aging behavior. After 90-days aging, the water uptakes of the [R/R/C/C](s), [R/C/R/C](s), [C/R/C/R](s), [C/C/R/R](s) hybrid composites are 2.72%, 2.41%, 2.38%, 2.36%, respectively. The results simulated with the finite element analysis show good consistency with the experimental results of moisture absorption and reveal the different moisture diffusion evolution process of the R/C hybrid composites. The cross-sectional contact angles of the hybrid composites is obviously less than surface contact angles. According to change the lay-up sequences, the flexural modulus of the unaged [C/R/C/R](s) and [C/C/R/R](s) composites can improve 0.98 times and 1.43 times than that of the unaged [R/R/C/C](s) composite. After 90-days aging, the flexural strengths of the [R/R/C/C](s), [R/C/R/C](s), [C/R/C/R](s), [C/C/R/R](s) composites decrease with 34.2%, 36.9%, 25.2%, 25.8%, respectively. Furthermore, the fracture modes of the hybrid composites before and after hygrothermal aging vary from brittle fracture to ductile fracture. The knowledge gained in this study will benefit future design optimization of natural fibers hybrid composites and their engineering applications.