Abstract 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.

中文翻译：

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厚碳纤维增强塑料复合板双光束激光钻孔工艺

摘要 激光烧蚀已被证明是加工碳纤维增强塑料复合材料（CFRPs）的有效方法。以前对 CFRP 激光钻孔的实验研究通常仅限于薄板。对于厚（10 毫米以上）CFRPs 板，激光钻孔工艺的可行性、效率和尺寸精度的研究仍然缺失。本研究提出了一种为厚 CFRP 加工开发的新型双光束对向位错 (DBOD) 激光钻孔工艺。首次采用DBOD工艺，CFRPs试样厚度达到10mm，与其他研究相比有了显着提高。为了研究激光钻孔过程的材料去除机制和热影响区（HAZ）效应，采用有限元法(FEM)建立三维热流模型。对 CFRP 纤维层进行了综合烧蚀实验以验证理论模型。此外，在厚 CFRPs 板上进行了两种类型的钻孔实验，以研究与单光束工艺相比，DBOD 工艺激光钻孔的可行性、效率和质量。研究发现，对于单光束工艺，材料去除效率可分为三个阶段：快速去除阶段（Stage I）、静止去除阶段（Stage II）、慢速去除阶段（Stage III），以及 DBOD 激光钻孔工艺可以保持前两个阶段（第一阶段和第二阶段）的钻孔过程，从而提高了制造效率。实验结果表明，与单光束工艺相比，DBOD钻孔工艺可以将加工效率提高近两倍，孔入口或出口处的热影响区要小得多。因此，DBOD 激光钻孔具有在厚 CFRP 钻孔过程中实施的潜力。