The interface temperature and its influence on surface integrity in ultrasonic-assisted drilling of CFRP/Ti stacks

Abstract

Carbon fiber reinforced plastics (CFRP) /Titanium alloy (Ti) stacks are being extensively applied in aerospace area for superior mechanical properties. During drilling of CFRP/Ti stacks, irreparable thermal damage in CFRP at the stack interface can be easily induced by high interface temperature. This paper contributes to scientific understandings of cutting temperature characteristics, heat dissipation and resulting surface integrity in CFRP at the stack interface in both Ultrasonic Assisted Drilling (UAD) and Conventional Drilling (CD) of CFRP/Ti stacks. Results show that, similar to cutting temperature characteristics, a sudden drop of interface temperature occurs in UAD rather than a slight increase in CD. Compared with CD, the maximum interface temperature and duration of temperature beyond the glass transition temperature at stack interface in UAD are reduced by about 22.8% and 52.2% at n = 1000 rpm and f = 5 μm/rev respectively. With the aid of those findings, the relationships between temperature distribution in CFRP at the stack interface and drilling parameters have been discovered and temperature effects on CFRP hole exit damages have been elucidated. The findings of this paper can contribute to identifying the heat affected zone of CFRP and providing guidance for industrial practice to reduce the negative temperature effect in drilling of CFRP/Ti stacks.