Mechanical Performance of Hemp Fiber Polypropylene Composites at Different Operating Temperatures

In order to quantify the effect of temperature on the mechanical properties of hemp fiber polypropylene composites, formulations containing 25% and 40% (by weight) hemp fiber were produced and tested at three representative temperatures of 256, 296, and 336 K. Flexural, tensile, and impact tests, as well as dynamic mechanical analysis, were performed and the reduction in mechanical properties were evaluated. Impact resistance was independent of temperature, whereas flexural and tensile properties were strongly affected. The highest reductions were observed in stiffness (modulus) values and flexural properties were reduced to a higher degree. The reductions in mechanical properties were well explained by a simple quadratic curve-fitting procedure applied to experimental data. Dynamic mechanical analysis revealed no change in glass transition temperature when the fiber content was increased but the composite material had better temperature resistance at higher fiber content. The results of the present study will be helpful in determining the end-use application of these composite materials.