Safe walking on the floor is evaluated by the static friction coefficient. Walking and creeping can generate electric static charge of intensity depends on the material of floor. Generation of electric static charge increases the adhesion between footwear and floor so that friction coefficient increases. The present paper discusses the effect of reinforcing epoxy by copper wires of different diameters on the generation of the electric static charge and friction coefficient when rubber sole slides against epoxy floor. Tests have been carried out at dry and water wet sliding. The effect of number of wires, location and wires diameter inside the matrix of the epoxy is studied. Based on the experimental observations, it has been found that at dry sliding, the electric static charge measured in volts significantly increased with increasing the number of wires. As the sliding distance increased voltage increased. Voltage decreased with increasing the distance of wire location from the sliding surface. When the wires were closer to the surface, the generated voltage increased. Besides, the increase in the wire diameter caused significant voltage increase. At water wetted sliding, voltage decreased due to the good water conductivity. As the sliding distance increased, the generated voltage decreased. Friction coefficient increased with increasing the number and diameter of copper wires. When the wires were closer to the surface, they were strongly influenced by the electric field and consequently the intensity of the electric charge increased leading to an increase in friction coefficient. At water wet sliding, the observed friction values were relatively higher due to the formation of the double layer of electric static charge on the two sliding surfaces causing an increase in the adhesion between the mating surfaces, where the water homogeneously distributed the electric static charge on the sliding surface.
Ali et al. (Thu,) studied this question.