Mechanical properties of polypropylene structural foams with fiber-reinforced skins

This article reports on the effect of skin thickness, core density, and skin composition on the mechanical properties of sandwich structural foams. In this study, the skin layers are polypropylene reinforced by different amounts of hemp fibers while the core is the same polypropylene foamed using different amounts of chemical blowing agent. The sandwich structures are characterized mechanically in terms of tensile and flexural properties. The results show that fiber introduction in the skins not only improved the mechanical properties, but also produced finer cell structures in the core. Finally, a mechanical model including fiber concentration, skin thickness, and density profile in the core is proposed to predict with high accuracy the elastic modulus of the sandwich foams.