Statistical distribution of mechanical properties and energy absorption of laminated cotton fabric reinforced epoxy composites

In this work, the statistical distribution of mechanical properties and energy absorption at break of laminated cotton fabric reinforced epoxy composites was determined. The static mechanical tests showed that the cotton fabric significantly influenced the mechanical performance of epoxy resin, where tensile strength, tensile modulus, tensile elongation at break, flexural modulus, and impact strength increased significantly, while flexural strength decreased. The energy absorption behaviors in the tensile tests were investigated, where more energy at tensile break was absorbed when cotton fabric was incorporated, as shown by the 684% to 2707% increase. The similar increases were observed in the flexural and impact tests, which were 92% to 355% and 309% to 833%, in different directions, respectively. The statistical distribution patterns of the mechanical properties parameters in variously direction of cotton fabric reinforced laminate were mapped. The results showed the distribution patterns of tensile modulus, flexural modulus, tensile strength, flexural strength, and energy absorption before maximum stress in the flexural test correlated with fiber angle in the laminate, while the distribution patterns of tensile elongation, impact strength, and energy absorption in the flexural and tensile tests agreed well with distribution of fiber content in the test cross section. With the incorporation of cotton fabric, the breakage behavior of epoxy transitioned from brittle fracture to toughened fracture as shown in distribution patterns of fracture energy absorption. The viscoelastic properties of the cotton fiber-reinforced laminates were investigated via DMA. The cotton fiber-reinforced laminates possessed higher transition temperatures, the storage modulus (E') and loss modulus (E"), compared to epoxy.