Comprehensive review of drilling strategies for CFRP/Ti stacks in aircraft manufacturing

Single-shot drilling of carbon fiber-reinforced polymer/titanium alloy stacks in aerospace applications poses unique challenges. The interaction between the cutting tool and the composite-metal contact often leads to poor hole quality and increased tool wear. The review extensively examines research achievements and developments in drilling CFRP/Ti stacks to comprehensively assess the impact of various machining settings on hole quality. Contributing factors such as stack-up machining thrust force, temperature, chip form and tool wear characteristics are thoroughly investigated. Moreover, this article highlights manufacturing defects in metallic and composite panels during drilling operations, contributing to a higher rejection rate in the assembly process. Usually, the maximum delamination of 1 mm, diameter deviation of +/- 30 mu m, burr height of 150 mu m, metal part's surface roughness of 1.6 mu m and CFRP part's surface roughness of 3.2 mu m are allowed in the aerospace industry. Additionally, the research explores strategies to mitigate manufacturing defects, including measures to limit hole and tool damage. These tactics encompass tool structure, machining environment, machining parameters and machining technology. On the whole, this review study aims to fill the research gap regarding process enhancement and performance evaluation of single-shot drilling of CFRP/Ti stacks in aerospace applications.