Hemp fibre as alternative to glass fibre in sheet moulding compound. Part 1: influence of fibre content and surface treatment on mechanical properties

Hemp fibre mat reinforced unsaturated polyester composites were fabricated using a conventional sheet moulding compound process. The influence of fibre and CaCO3 filler content on strength and stiffness of these hemp fibre reinforced sheet moulding compounds is reported and compared with data for chopped glass fibre reinforced sheet moulding compounds. In addition the influence of alkaline and silane treatments of the hemp fibres is evaluated. The experimental data are compared to modified versions of the Cox-Krenchel and Kelly-Tyson models, supplemented with parameters of composite porosity to improve the prediction of composite tensile properties. A good agreement was found between the modified models and experimental data for strenght and stiffness. The results indicate that hemp fibre reinforced sheet moulding compounds are of interest for low cost engineering applications that require high stiffness to weight ratios.