Dual-beam laser drilling process for thick carbon fiber reinforced plastic composites plates

The laser ablation has been proved to be an effective way to machine carbon fiber reinforced plastic composites (CFRPs). Previous experimental studies on laser drilling of CFRPs are usually limited to thin plates. For thick (above 10 mm) CFRPs plates, the studies on feasibility, efficiency and dimensional accuracy of laser drilling processes are still missing. This study presents a novel dual-beam opposite dislocation (DBOD) laser drilling process developed for thick CFRPs machining. By utilizing DBOD process, for the first time, the thickness of the CFRPs specimen reaches up to 10 mm, which has been significantly improved compared to other studies. In order to investigate the material removal mechanisms and heat-affected zone (HAZ) effect of laser drilling process, a three-dimensional heat flow model was established by using finite element method (FEM). Comprehensive ablation experiments on fiber layers of CFRPs were conducted to validate the theoretical models. In addition, two types of drilling experiments have been performed on thick CFRPs plates to study the feasibility, efficiency and quality of laser drilling by DBOD process as compared to the single-beam process. It was found that for single-beam process, material removal efficiency could be divided into three stages: rapid removal stage (Stage I), stationary removal stage (Stage II), slow removal stage (Stage III), and DBOD laser drilling process could maintain the drilling process on the first two stages (Stage I &II), which improve the manufacturing efficiency. The experimental results showed that DBOD drilling process can improve the processing efficiency by almost two times with a much smaller HAZ at the hole entrance or exit compared to single-beam process. Hence, the DBOD laser drilling has the potential to be implemented on thick CFRPs drilling process.