Mechanical performance of pultruded kenaf/glass hybrid fiber reinforced unsaturated polyester under hygrothermal conditions

This study assesses the nature of absorbed moisture and the correlation with hygrothermal effects in fiber-reinforced polymer (FRP) performance. Three types of fiber arrangement which is kenaf fiber and unsaturated polyester (UPE) only, kenaf fiber roving co-reinforced glass fiber chopped strand mat with UPE and kenaf fiber roving co-reinforced with fiber glass-oriented mat with UPE. All specimens were fixed at 0.50 Vf to make a fair comparison and validity results of further testing. As aware, GFRP has the highest mechanical properties which are superior compared to other samples of composite and KFRP shows the lowest mechanical properties. Hygrothermal conditions were achieved by immersing samples at a constant temperature of distilled water at 70°C for 1, 4 and 7 days hence results in the same trend of performance with unconditioned tests. However, all samples have certain percentage retention of mechanical strength after re-dried in an oven at 70°C for 24 hours to remove all the moisture in the samples. Water absorption is then were analyzed to determine the diffusion parameters of all samples. The flexural test was conducted to determine the durability and to measure its mechanical strength under a hygrothermal environment. FTIR proves the presence of water within the UPE matrix. Morphological analysis using confocal laser imaging and field emission scanning electron microscopy FESEM showing evidence by a clear picture of samples that undergo deterioration.