Influence of fiber orientation on the moisture adsorption of continuous bamboo fiber composites

Abstract

Recently, a considerable interest is being shown in the use of plant fibers as reinforcement for polymer composites. Indeed, researchers and scientists are trying to overcome the environmental bias by using bio-composites in several engineering applications. Their attractive specific mechanical properties, low cost, lightness and biodegradability may promote them to substitute expensive and non-renewable fibers such as carbon, kevlar and glass fibers. However, the hydrophilic behavior of natural fibers is of a great concern for their possible outdoor applications. Indeed, the entrapment of water molecules at the fiber lumen, voids and porosities may reduce the tensile strength and modulus of plant fiber composites. Hence, this work aims to evaluate the moisture adsorption behavior of bamboo fiber epoxy composites at different fiber orientations (tangential and radial directions). Firstly, bamboo fibers are extracted using a combination of compression and manual techniques. Morphological and thermogravimetric analyses are carried out to deeply understand the physical properties of the extracted fibers. The findings show that the fibers consist of parallel microfibrils enclosed by some impurities and amorphous constituents. The moisture content of bamboo fibers at 50RH% is deduced from the moisture evaporation stage in the thermogravimetric curve and is about 8.07%. Thereafter, hand layup and compression techniques are used to manufacture the composite samples for the moisture adsorption test. The obtained results show that the equilibrium moisture capacity and diffusion rate values are higher along the fiber direction, which is mainly due to the exposure of the fiber lumen and interfacial voids. The mechanism of moisture transport into composites is found to follow Fick’s law.