Machinability and surface integrity of adhesively bonded Ti/CFRP/Ti hybrid composite laminates under dry and cryogenic conditions

The current work compares the machinability of conventional drilling of hybrid titanium/carbon fiber reinforced plastics/titanium (Ti/CFRP/Ti) stack laminates in a single shot under dry and cryogenic conditions. Damage at metal-composite interface (MCI), thrust force, torque, burr height, surface roughness, average hole size, circularity error, and perpendicularity error are considered as experimental outcomes to investigate the influence of cryogenic cooling on the machinability of Ti/CFRP/Ti stacks. The experimental outcomes indicate that the hole quality significantly improved under cryogenic condition compared to dry drilling for the range of drilling parameters chosen. However, cryogenic cutting yields an increased thrust force due to increase in the hardness of Ti sheet at low temperatures. Scanning acoustic microscopy (SAM) was capable of capturing damage at MCI. Scanning electron microscope (SEM) and micro-computed tomography (μ-CT) are also used to assess the drilling induced damages on hole wall surface under both (dry and cryogenic) conditions.