The effect of piercing and drilling processes on burr formation and delamination of aged carbon and aramid fiber-reinforced polymer composites

There are two major problems with fiber-reinforced polymer (FRP) composites during their machining that need to be ad-dressed. The first concern is the delamination and formation of burrs at machined edges, and the second is the effects of aging leading to mechanical deterioration. In this study, carbon FRP (CFRP) and aramid FRP (AFRP) composites were manufac-tured by vacuum infusion method and aged for 2 years under natural environmental conditions. Piercing with three different clearances (1%, 5%, and 10% of sheet thickness) and speed of 4 m/s were performed. Additionally, conventional drilling was carried out at a feed rate of 0.2 m/min. The highest delamination factor difference between piercing and drilling processes was calculated as 7.3% and 13.9% for CFRP and AFRP, respectively. The highest burr amounts for AFRP and CFRP composites were obtained as 91.5% and 39% at 10% clearance for piercing process and 123% and 32.1% for drilling process, respectively. Compared with drilling, piercing generates less burr formation except for CFRP composites in the case of 10% clearance and more precise hole production. It is understood that piercing results significantly improve when smaller clearances up to 5% of the sheet thickness are utilized.