Exposure to natural weathering changes the mechanical properties of unsaturated polyester composites. These changes can negatively affect the mechanical properties of natural fibre composites, through UV radiation and relative humidity. The idea of this study was to determine the durability of kenaf unsaturated polyester composites (KFUPC) in natural conditions, and in addition, to determine the effects of weathering on the performance of these composites and the biodegradability possessed by the composite when exposed to natural weather. KFUPC composites were exposed to the atmosphere for four months. Humidity up-take tests were performed on composite specimens containing (10%, 20% and 30%) weight percentage of fibre content. The tensile properties of exposed specimens were evaluated, and compared alongside dry composite specimens. A decrease in tensile properties of the weather exposed composites was demonstrated, compared with the dry samples. The percentage of moisture uptake increased as the weight percentage of fibre increased, due to the high cellulose content.
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