碳纤维增强复合材料紫外皮秒激光铣削机理与工艺规划研究

In order to meet the urgent need for high-precision machining of Carbon Fiber Reinforced Plastics (CFRP) In aerospace application, a novel UV picosecond pulsed laser processing theory and technology is studied in this project. CFRP consists of reinforced carbon fibers and resin matrix which feature the material by serious anisotropy and heterogeneity. The energy absorption by porous carbon framework is calculated considering the mobile laser source. The mechanical erosion of thermal decomposition gases is described by an established porous flow model to analyze the material removal mechanism. The micro-scale thermodynamic finite element simulation is conducted to study the temperature difference at the fiber-matrix interface and stress concentration phenomenon caused by different thermal expansion coefficients. Though the simulation, the heat affected defects including cracks, resin thermal degradation are predicted and the relationship between the thermal damage and structural strength decrease is obtained. Based on the mapping from the scanning path to the energy density distribution, the processing strategy for complicated geometry on the milling layer is generated which can achieve minimum thermal damage, controllable machining precision and high efficiency. Research results from this project will enrich the theory of laser ablation of carbon fiber, resins and other dielectric materials and promote the application of picosecond pulsed UV laser composite materials processing technology. Meanwhile, it develops the ultra-short pulse laser processing technology and has great theoretical and engineering value.

面向航空航天领域对碳纤维增强复合材料(CFRP)高效高精度加工的迫切需求，本项目将系统研究复合材料紫外皮秒激光加工理论和方法。针对复合材料异质性和各向异性，研究多孔隙碳骨架结构对移动激光的能量吸收规律，探索树脂热解气体对断裂纤维的力学剥蚀行为，阐明紫外皮秒激光加工的材料去除机理。开展CFRP微观组织热力学特性有限元仿真，分析热膨胀系数不同与界面温差引起的热应力集中现象，揭示纤维熔胀、树脂退化等热力缺陷形成过程，探明热力损伤与结构力学性能衰减的映射关系。分析铣削层扫描路径对激光能量分布的影响规律，建立加工精度和热力损伤约束下的激光扫描策略，形成材料损伤小、加工质量可控的高效高精度激光加工工艺。研究成果将充实和发展碳纤维、树脂等电介质材料的激光烧蚀理论，促进紫外皮秒脉冲激光加工复合材料工艺的推广与应用，拓展超短脉冲激光加工技术的应用领域，具有重要的理论意义和工程实用价值。

围绕短脉冲激光铣削碳纤维复合材料的能量吸收、材料去除机理、工艺规划等关键问题展开研究，提出了紫外皮秒激光铣削加工CFRP的新工艺方法，实现CFRP的高效高精度加工。首先，研究了碳纤维复合材料对激光的吸收行为特征，建立了单根碳纤维表面吸收率模型与光线追迹模型，揭示了材料微观组织结构和激光光源特性对激光能量吸收的影响规律。第二，建立了短脉冲激光与材料相互作用的均质材料数值仿真模型，分析了热解气体流动压力随激光辐照与脉冲宽度的变化特征，揭示了材料力学剥蚀效应产生机理。第三，建立了短脉冲激光铣削过程三维数值仿真模型，揭示了树脂基体热解以及材料气化烧蚀动态过程，建立了脉冲序列加工形貌以及热影响区预测模型，激光铣削实验验证了预测模型。第四，建立了CFRP的微观异质材料仿真模型，分析了单脉冲和双脉冲分别烧蚀下CFRP的去除过程以及热影响区形成过程，揭示了脉冲持续作用时间和光斑水平间距对微坑形貌的影响规律；开展了短脉冲激光加工实验和力学测试实验，建立了激光加工CFRP的热力损伤与力学性能的关系。最后，开展了短脉冲激光加工CFRP的工艺实验研究，分析皮秒激光对CFRP盲孔的质量影响因素，提出了变填充间距和变扫描速度加工策略，获得理想的材料去除率和盲孔底面质量。研究成果拓展了超短脉冲激光精细加工技术的应用领域，具有重要的理论意义和工程实用价值。