Experimental analysis of tensile, flexural, and tribological properties of walnut shell powder/polyester composites

Polyester composite specimens with varying wt% of walnut shell powder (WSP) were prepared and characterized for their mechanical and tribological properties. The results of mechanical testing showed that the specific tensile modulus increased with an increase in WSP wt%, whereas the specific flexural modulus slightly decreased at 30 wt%. However, the specific tensile and flexural strength of neat polyester specimen were found to be more than the doped specimens. The specific tensile strength decreased with an increase in WSP wt%, whereas the flexural strength substantially varied with wt%. The tribo-properties were investigated using a wear and friction-monitoring apparatus. It was found from the tribo study that the doped specimens offered higher wear resistance than the neat polyester specimen at all the sliding conditions. The friction coefficient of the doped specimens also remained higher than the neat polyester specimen at most of the sliding conditions. Based on these favorable properties, i.e., increased stiffness, lower specific wear rate, and higher friction coefficient, the WSP can be used as a potential bio-filler in friction composites where such properties are highly desirable.