The present work investigates friction and wear displayed by the scratch of low density polyethylene (LDPE) composites reinforced by unidirectional continuous copper wires of 0.3 mm diameter. This is a simulation of bearing material. Influence of heat treatment processes such as (annealing, hardening and tempering) on their friction and wear was studied.
It was found that friction coefficient displayed by the scratch of LDPE reinforced by copper wires increased as the load increased due to increased material removed during scratch. Friction coefficient decreased with increasing number of wires up to eight wires then started to increase at 10 wires. It seems that, the presence of copper wires decreased the hardness of the polymeric materials so that the material removed by the indenter was easier. At 10 wires, friction became between the scratching tool and wires themselves due to narrow area between wires that caused the increase of the friction coefficient. The influence of heat treatment on friction was investigated. As the unheated specimens showed the highest friction coefficient, Tempered LDPE composites reinforced by unidirectional continuous copper wires specimens displayed the lowest friction values followed by hardened and annealed specimens. Friction coefficient increased with increasing normal load by annealing and hardening while it decreased by tempering.
As the number of copper wires increase, wear scar width of the LDPE composites slightly decreased. The wear decrease of the tested specimens can be explained on the basis that presence of copper wire reinforcement can restrain the deformation of the polymer composites. Besides, plastic deformation, grooving and smearing of surface can be decreased by the strengthening effect of the reinforcement as well as the retarding action of the wire against the motion of the indenter. The heat treatment of tested composites investigate that Tempered specimens displayed the lowest wear scar width values while untreated ones showed the highest wear scar width values. Wear scar width increased with increasing normal load by annealing at 90 °C and hardening at 120 °C while it decreased by tempering at 110 °C. Annealed specimens displayed relatively higher wear scar width than hardened and tempered specimens.