Effect of ocean water absorption on flexural properties of Cannabis sativa L. hemp fibre reinforced polymer composites for marine applications

Abstract

Hemp is one of the strongest and most durable commercially available natural fibre. Its biodegradability, low density, high fibre length, availability, low weight-to-strength ratio and more yield per acre makes it an ideal fibre for marine applications. Water absorption behaviour of any material is very important which mainly limits their use specifically in marine applications. The present work aims to study the absorption of ocean water, its kinetics and effects on the flexural properties of hemp reinforced composites. Absorption effects for epoxy and unsaturated polyester (UPE) reinforced with short hemp fibre, unidirectional and bidirectional hemp fabric were investigated by immersing samples in ocean and distilled water. The absorption of all composites followed Fickian diffusion with slight deviation due to swelling of fibres and formation of microcracks. It is observed that the water uptake of samples increased with increasing weight fraction. The flexural strength and modulus of composites degraded by approximately 10% and 20% for epoxy and UPE composites respectively, due to water absorption. The results indicated that hemp fibre based composites could be used for many lightweight components in marine applications.