Hygrothermal aging behavior and mechanical properties of modified ramie fiber reinforced polyethylene terephthalate glycol composites

In this work, the hygrothermal aging behavior, finite element analysis and mechanical properties of the ramie fiber (RF) reinforced polyethylene terephthalate glycol (PETG) composites modified with silane coupling agent and carbon nanotubes (CNTs) were investigated. The results show that after 90-days hygrothermal aging, the RF/PETG composites with untreated, KH550-treated, 0.5% CNT-treated and 1.0% CNT-treated modifications have the low water uptakes of 4.55%, 4.36%, 4.30% and 4.15%, respectively. The surface modifications of ramie fibers have no obvious influence on the water uptakes of the RF/PETG composites, which is related to the hydrophilicity difference of surface and cross sections of the RF/PETG composites. The moisture absorption behaviors of the RF/PETG composites conform to Fick's water diffusion law. The results of the finite element analysis of the RF/PETG composites show a good consistency with the experimental results of the water absorption. As compared with untreated composites, the bending strengths of RF/PETG composites modified with silane coupling agent, 0.5 wt% CNTs and 1.0 wt% CNTs increased with 8.5%, 16.9%, and 20.5%, respectively. The bending strength and modulus of the RF/PETG composites first rapidly decrease and then slowly decrease with the increase of aging time. The RF/PETG composites show different bending fracture behaviors before and after 90-days hygrothermal aging. The developed RF/PETG composites have low water absorption and good mechanical properties, which can broaden the research and application of ramie fiber reinforced composites.