Damage mechanics of polypropylene‐based composites using progressive‐ and constant‐load scratching

Abstract Polypropylene (PP)‐based composites with reinforcements of CaCO₃and rice husk ash (RHA, agricultural waste) are extensively used in textile industry and manufacturing of plastic yarns, tapes, etc. Tribological properties of the PP‐CaCO₃‐RHA based composite are studied using constant‐ and progressive‐load scratching. The progressive load scratching depicts a transient‐state interaction, whereas, constant load scratching depicts steady‐state of wear, hence, both modes of scratching are reported to highlight the aspects of damage initiation and damage tolerance on PP‐based composites. The average scratch hardness and toughness of the PP composites improved with reinforcement in both modes of scratching. The reinforcement of 20 wt% RHA and 10 wt% RHA with 10 wt% CaCO₃ in PP matrix, marginally improves (0.8%‐1.6%) the wear resistance (wear rate, W_R of 12.1‐12.2 mm³ N⁻¹ m⁻¹) during the progressive load scratching compared to that of pure PP (12.3 mm³ N⁻¹ m⁻¹). Poor wear resistance (W_R = 12.6 mm³ N⁻¹ m⁻¹) with the addition of 20 wt% CaCO₃ in PP matrix during the progressive wear is attributed to poor adhesion (adhesion factor: 0.61) of CaCO₃ with PP. Also, an over estimation (3.4‐4.6 times) of wear rate is attributed to high recovery (0.63‐0.77) and the plastic deformation ahead of the scratch tip in the PP‐based composite with viscoelastic nature. High‐wear rate with CaCO₃ agglomerate with poor sinterability at 200 °C can be substituted with the strong adhesive nature of RHA (bimodal pore distribution) in PP matrix to achieve optimal hardness, elastic modulus, and scratch resistance.