Xu Hebing, Hu Jun
School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Polymers (Basel). 2016 Aug 15;8(8):299. doi: 10.3390/polym8080299.
Short pulsed laser is preferred to avoid the thermal damage in processing the heat sensitive material, such as carbon fiber reinforced plastic (CFRP). In this paper, a numerical model capturing both the material ablation and polymer matrix pyrolysis processes in pulsed laser processing is established. The effect of laser pulse length from ns order to μs order is studied. It was found that with shorter pulse length, ablation depth is increased and heat affected zone is remarkably reduced. Moreover the pyrolysis gas transport analysis shows that shorter pulse length results in a larger internal pressure. At pulse length in ns order, maximum pressure as high as hundreds of times atmospheric pressure in CFRP could be produced and leads to mechanical erosion of material. The predicted ablation depth of a single short laser pulse conforms well to the experiment result of the CFRP laser milling experiment.
短脉冲激光更适合用于加工诸如碳纤维增强塑料（CFRP）这类热敏材料时避免热损伤。本文建立了一个数值模型，该模型可捕捉脉冲激光加工中材料烧蚀和聚合物基体热解过程。研究了从纳秒级到微秒级激光脉冲长度的影响。结果发现，随着脉冲长度缩短，烧蚀深度增加，热影响区显著减小。此外，热解气体传输分析表明，较短的脉冲长度会导致更大的内部压力。在纳秒级脉冲长度下，CFRP中可产生高达数百倍大气压的最大压力，并导致材料的机械侵蚀。单个短激光脉冲的预测烧蚀深度与CFRP激光铣削实验的实验结果吻合良好。
