Effects of heat accumulation on the characteristics of hole wall temperature and damages in drilling of UD CFRP

Application of carbon fiber reinforced plastic (CFRP) in aircraft load-carrying structure makes the component become thicker and damage tolerance get stricter. The heat accumulation highly increases the hole wall temperature along feeding direction during thicker CFRP component drilling due to the low thermal conductivity, which highly deteriorates the hole quality. Therefore, this paper proposed a hole wall temperature measurement experiment at various fiber cutting angles with different measuring distances to investigate the effects of heat accumulation on the cutting temperature and damages. Results show hole wall temperature in the vicinity of hole-exit increases by almost 20⁓40 °C and 30⁓65 °C separately for S=3000 rpm and S=5000 rpm. The fiber shearing and bending when against fiber cutting seriously increases temperature near the hole wall by increasing the fiber-rich regions and contact time between workpiece and cutting lip. Moreover, the maximum temperature distribution maps along feeding direction and radial direction were separately drawn for the first time to analyze the heat accumulation and overheating areas. The hole wall along the hole edge and feeding direction were detected, and severe matrix cracking, fiber bending, and fiber-matrix debonding occurred at the position where maximum temperature was located. In the future, the findings of borehole temperature characteristics can be used to refine the existing temperature model of CFRP drilling.