Dynamic mechanical analysis and effects of moisture on mechanical properties of Interwoven Hemp/Polyethylene Terephthalate (PET) hybrid composites

To reduce the dependence towards the petroleum-based fibre, the natural fibre started to receive attention as reinforcement materials in composite due to their advantages such as non-toxic, easy to get, and less harmful to human health. However, one limitation is that the natural fibre has high moisture absorption compared to synthetic fibre. Thus to improve the moisture absorption in natural fibre composite, the natural fibres are hybridised with the synthetic materials. In this research, a dynamic mechanical analysis (DMA) was undertaken, and the influence of moisture on the mechanical properties of the woven and interwoven hybrid composites was investigated. The composites were manufactured using a vacuum infusion process with a volume fractions of 25 % fibre and 75 % epoxy resin. Hybrid composite laminates were fabricated using the interwoven between hemp and PET fibre reinforced epoxy resin. The composite specimens were subjected to thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Tensile, flexural, and impact tests were conducted at dry and wet condition specimens of the woven and interwoven hybrid composites according to their ASTM standards. Scanning electron microscopy (SEM) analysis was performed to examine the fracture behaviour and the effect of the water penetration through the fibre/matrix interface. The glass transition temperature for the woven hemp, woven PET, and interwoven hemp/PET hybrid composites were 64, 66, and 67 °C, respectively. This study shows that the water absorption uptake reduces by half for the interwoven hemp/PET hybrid composite. The hybridisation of PET fibre enhanced the interwoven hemp/PET hybrid composite tensile, flexural, and impact strength by 4, 22, and 5 % compared to the woven hemp composite, respectively. Those reductions attributed by matrix cracking, debonding, and plasticization effect. Lastly, it can be concluded that hybridisation of hemp with PET fibre improved the thermal and mechanical properties performance of the woven composite and reduce the rate of water uptake on the mechanical properties.