Experimental Investigation and Artificial Neural Network Prediction of Heat-Affected Zone in Microwave-Induced Plasma Drilling of Kenaf/Polypropylene Composites

Conventional drilling of fiber-reinforced polymer composites often leads to severe hole damages, such as fiber pull-out, delamination, and micro-cracks. These damages arise from the intense tool and workpiece interaction which reduce the durability of fastenings. The non-conventional drilling techniques offer a promising alternative to produce good quality holes in FPRCs owing to the absence of harsh tool-workpiece contact. Microwave-induced plasma (MIP) drilling is one such technique that utilizes the microwave energy at 2.45 GHz to produce the holes in electrically conductive and non-conductive materials. Therefore, the current study delves into the MIP drilling of kenaf/polypropylene composites at five distinct levels of microwave power and feed rate. The drilled holes were characterized for heat-affected zone (HAZ). Stereo binocular microscopic images were used for the morphological analysis of HAZ around the holes. Moreover, thermal images of holes and differential scanning calorimetry of kenaf/polypropylene composites were utilized to understand the HAZ. On observation, the HAZ was found increasing with microwave power. However, the HAZ decreased at higher values of feed rate. The microwave power of 180 W and the feed rate of 145 mm/min were the optimum process parameters resulting in the minimum HAZ of 167 mm². Further, an artificial neural network model accurately predicted the HAZ values with the maximum deviation of 1.19% from experimental findings.