Optimization of machining parameters during end milling of carbon fiber-reinforced polypropylene textile composite

Carbon fiber-reinforced polypropylene (CFRPP) composites are being used at an increasing rate in lightweight mechanical applications. The reasons are their excellent strength-to-weight ratio, corrosion resistance, and recyclability. However, their anisotropic and heterogeneous structure holds considerable challenges during machining processes, such as end milling, often resulting in surface defects and dimensional inaccuracies. The present study focuses on the optimization of milling parameters for CFRPP composites using the VIKOR technique and systematically investigates the influence of critical process variables, including feed rate, depth of cut, and spindle speed, on key output responses. These responses included machining temperature, machining force, delamination factor, and surface roughness. To develop and understand these models, a Box-Behnken experimental design of Response Surface Methodology was employed. Spindle speed had the highest influence on machining temperature (43.36%), followed by feed rate (32.77%) and depth of cut (21.74%). Machining force was mainly affected by feed rate (55.02%), depth of cut (31.02%), and spindle speed (12.83%). For delamination factor, feed rate contributed the most (54.53%), followed by depth of cut (27.21%) and spindle speed (17.09%). Surface roughness was also primarily influenced by feed rate (43.49%), followed by depth of cut (30.86%) and spindle speed (24.45%). The SEM analysis helped in understanding the defects such as fiber fracture, fiber pullout, voids, and matrix smearing.