Effect of assembly pre-stress on the scratch behavior of polycarbonate

Scratch damage can reduce both the aesthetic appearance and structural integrity of polymer surfaces. To optimize and enhance the scratch resistance of polycarbonate, this study investigates the influence of assembly pre-tensile and pre-compressive stresses, with scratch experiments being conducted under both linearly increasing and constant normal load modes. Experimental results and finite element simulations are used to analyze scratch resistance and visibility. The results indicate that the application of 20% pre-compressive stress increases the critical normal load for onset of scratch visibility by 42% compared with the case in which no assembly pre-stress is applied, and it effectively decreases residual scratch depth, shoulder height, shoulder width, and tangential load. This is because assembly pre-compressive stress can effectively counteract the extrusion of material at the front and sides caused by the sliding scratch tip. Pre-compressive stress hinders scratch groove formation, improving the scratch resistance of polycarbonate. By contrast, pre-tensile stress weakens these characteristics. This study provides valuable insights for enhancing the surface damage resistance of polycarbonate materials.