Denim fabric-reinforced unsaturated polyester: effect of different fabrication methods on mechanical properties and water absorption properties

The present research study aims to produce unsaturated polyester composite made of denim fabric and unsaturated polyester by using three different fabrication methods, such as compression moulding, resin vacuum infusion and hand lay-up techniques. The average unsaturated polyester-to-composite weight ratio was strongly affecting the mechanical properties of the unsaturated polyester composite. The hand lay-up technique showed the highest unsaturated polyester-to-composite weight ratio at 70.63%, 55% in resin vacuum infusion technique, and 51.62% in compression moulding. The results showed that the higher the unsaturated polyester-to-composite weight ratio, the lower the mechanical properties. Nonetheless, the overall mechanical properties of denim fabric-reinforced unsaturated polyester composite were enhanced in comparison with the neat unsaturated polyester. In details, among all the composites samples, the compression moulded composite exhibited maximum tensile strength, modulus of elasticity, impact strength, flexural strength, and flexural modulus whereas resin vacuum infusion composite showed the highest elongation at break and average percentage in water absorption test. Moreover, the hand lay-up composites were found to have the lowest values in majority of mechanical properties, mainly due to their high unsaturated polyester weight ratio and poor interfacial interaction between denim and unsaturated polyester. The hand lay-up composite absorbed the least water molecules as compared to another two unsaturated polyester composites due to the highest unsaturated polyester-to-composite weight ratio as compared to two other fabrication methods. The morphological study has been investigated and the results in line with the mechanical properties of the unsaturated polyester composites.