Influence of various starch/hemp mixtures on mechanical and acoustical behavior of starch-hemp composite materials

Abstract

The starch-hemp composite materials are manufactured from the natural raw materials (water, starch and hemp shives) and a new durable material for construction and building. In this work, experimental investigation was carried out to study the mechanical and acoustical performance of starch-hemp composite materials. The starch-hemp composite materials specimens with five Hemp/Starch ratios (H/S = 6, 8, 10, 12 and 14), were manufactured by using the optimal binder and two hemp shives (0–15 mm and 0–20 mm). Density of the starch-hemp composite materials varies with the H/S ratio. The dry density for the starch-hemp composite materials is lower, between 163.6 kg/m3 and 169.1 kg/m3 in case of the hemp shives 0–15 mm and between 168.1 kg/m3 and 174.3 kg/m3 for the hemp shives 0–20 mm. The relation between stress and strain of the composite materials is not linear. The ultimate compressive stress can reach 0.55 MPa and the compressive strain is up to 30%. The results obtained by test show that the tensile strength depends strongly on the Hemp/Starch ratio and the hemp shives sizes. The variation of elasticity modulus and Poisson's ratio in function of the H/S ratio was also analyzed in this paper. The mechanism of the cracks or failure of the specimens was studied by using ARAMIS optical system. The study on acoustical behavior shows that the starch-hemp composite materials are a good sound absorber material for medium and high frequencies with a value around 0.7. The influence of the H/S ratio on the absorption coefficient is small. The results show that the starch-hemp composite materials have a good mechanical and acoustical performance and can be used as building materials.