Analysis of mechanical properties of hemp fibre reinforced unsaturated polyester composites

Different chemically treated hemp fibre reinforced unsaturated polyester composites were investigated over a range of fibre content (0-60 wt%). Although Young's modulus of all the short fibre reinforced unsaturated polyester composites was found to be higher than that of unreinforced unsaturated polyester; however, tensile strength of the composites exceeded that of the unsaturated polyester matrix only for the combined alkali- and silane-treated fibre composites at 40 wt% fibre content. The decrease in tensile strength of the composites could be attributed to stress concentrations caused by the fibres in conjunction with the brittle matrix. Impact strength of all the treated fibre composites was higher than that of the untreated fibre composites at all fibre contents. K-Ic and G(Ic) of the composites decreased initially and then increased as the fibre content increased because more and more fibres being available to pull-out. The mechanical properties of the composites were increased further due to the alignment of long fibres.