Water absorption behavior and its effect on the mechanical properties of kenaf natural fiber unsaturated polyester composites

Treated kenaf fiber reinforced unsaturated polyester composites at different weight fractions (0, 10, 20, 30 and 40wt %) are fabricated and evaluated by their immersion in tap water at two different temperatures of 25 ºC and 50 ºC. The results showed that the percentage of water absorption increases with increasing of fiber weight fractions and environmental temperature. The process of absorption of water was found to approach the Fickian diffusion behavior for both various temperatures. Water diffusion coefficients were evaluated and the results showed that they increase with the increasing environmental temperature and fiber weight fractions. Furthermore the results indicate that the flexural properties of the composites decreased drastically on exposure to moisture results due to degradation of the fibermatrix interface. A scan electron microscopy SEM shows that at high environmental temperatures a deboning developed between the fiber and matrix, which is causing a majority of fiber to fail by fiber pull out mode failure. In addition microcracks developed at the interface between the fiber and the matrix