Effects of multi-functional surface-texturing on the ice friction and abrasion characteristics of hybrid composite materials for footwear

Abstract

There is growing demand for composite materials for use with slip-resistant footwear. This paper reports on the optimization of a surface-textured hybrid composite material with good slip-resistance on ice. Our material has a unique design consisting of a soft rubber compound reinforced with a combination of soft and hard microscopic fibers embedded within it that protrude out from its surface. These fibers can penetrate icy surfaces, while the soft rubber component deforms to mold against hard substrates resulting in mechanical interlocking.Our previous work has shown our initial formulations of this composite has superior slip-resistance and abrasion resistance compared to other materials on the market. The objective of this work was to systematically vary manufacturing (fiber content and molding temperature) and testing parameters (normal load and sliding velocity) to evaluate the effects on slip-resistance before and after abrasion.Our hybrid thermoplastic polyurethane (TPU) composites composed of carbon fiber (CF) and poly (p-phenylene-2,6-benzobisoxazole) (PBO) fibers were fabricated by means of compounding followed by ablation. The coefficient of friction on ice was measured before and after simulated wear using SATRA STM 603 slip-resistance testing machine (SATRA). The surface morphology of each composite was also characterized visually using scanning electron microscopy (SEM). The set of experiments used was derived by applying the Taguchi method for robust design.The optimal combination of parameters maximizing the coefficient of friction on ice after abrasion was determined. Before abrasion, the only control factor that affected the ice friction properties of the composite was fiber content (p = 0.024). After abrasion, ice friction was independent of all control factors with no interaction effects and no sensitivity to the testing parameters, indicating the capability of the material to retain its slip-resistance even after extensive wear (COF = 0.61 ± 0.05). The SEM images indicated that there was significant fiber protrusion from the textured surfaces after abrasion. These findings suggest that our hybrid composite material has good potential for use in applications such as winter footwear for providing traction on icy surfaces even after extended use.