碳纤维增强树脂基复合材料（CFRP）的飞秒激光脉冲序列高精度可控加工机理研究

The use of carbon fiber reinforced plastics (CFRP) material has become widespread in various industries, due to its high strength-to-weight ratio and rigidity. As a two-phase-mixed (carbon fiber plus epoxy resin), anisotropy, inhomogeneous material, achievements of high-precision machining has become one of the deep concerns of promoting its application. Oriented towards the growing common demands of precision-machining for the national aerospace engineering, this study aims at solving two of the bottle-necked scientific problems for ultrafast laser-based high-precision machining: one is the lack of a comprehensive, theoretical/simulation model for guidance, another is the uncovered mechanisms for homogeneous etching of CFRP and highly selective removal of the epoxy resin. A multi-scale modeling is proposed by an organic consideration of the beam propagation/absorption model with dynamic optical and thermal descriptions, the phase change model and the radiation hydro-dynamical modeling. For each phase or CFRP itself, the modification/ablation thresholds, etching shape, as well as their evolutions with temporally and spatially shaped femtosecond laser pulse trains, will be studied, both experimentally and theoretically (based-on the multi-scale model proposed). The influence of wavelength will also be explored. The formation and control mechanisms of heat-affected- zone in CFRP will also be investigated with shaped femtosecond laser pulse irradiation. The theory and method for homogeneous etching of CFRP, or for highly selective removal of the epoxy resin, will be proposed or uncovered afterwards.

碳纤维增强树脂基复合材料(CFRP)因其轻质高强、高刚度的特性应用日益广泛。作为一种细观呈现基体相与增强相两相混合的各向异性、非均匀复合材料，实现其高精度加工成为促进其应用的重要关切内容。本项目面向我国重大航天工程领域日益增长的复合材料高精度加工共性需求，针对CFRP的超快激光高精度可控加工面临的两个瓶颈科学问题：指导高精度可控加工的理论/仿真模型尚未建立、CFRP各组分均匀刻蚀或高精度选择性蚀除机制尚未揭示，通过综合考虑激光束的传播与吸收过程中的瞬时局部光学、热学模型，以及材料相变和等离子体产生过程，建立起一个从飞秒到毫秒、从纳米到毫米的超快激光与CFRP相互作用的多尺度模型；拟通过研究材料和各相的改性蚀除阈值及微观蚀除形状随整形飞秒激光的演化规律、材料热影响区的形成及调控机制研究，揭示基于时/空/频域整形超快激光实现高精度可控加工（即高精度均匀刻蚀与高精度选择性刻蚀）的机理与方法。

碳纤维增强复合材料(CFRP)因其优异的力、热、电学性质，是航天领域不可或缺的关键材料。作为一种细观呈现基体相与增强相两相混合的非均匀材料，传统加工方法存在突出的加工损伤与精度问题，如分层、壁面粗糙、结构尺寸精度低。飞秒激光等超快激光具备解决传统加工问题的潜能，但因CFRP基体相（即树脂）和增强相（即碳纤维）迥异的光学、热学性质，一般既难以均质化去除也难以高选择性去除。. 本项目针对超快激光高精度可控加工CFRP面临的两个关键基础问题，即指导高精度可控加工的计算模型尚未建立、CFRP材料组织均匀刻蚀或高精度选择性蚀除的机制尚未揭示，开展了整形超快激光加工CFRP的机理、方法及应用基础研究。主要开展了三方面的工作：（1）建立了飞秒、皮秒等超快激光与CFRP相互作用的多尺度理论模型，揭示了光场作用下的材料瞬时局部光学、热学特性演变规律，提出了采用材料解离能作为其去除阈值理论判据的假设并得到了验证，在此基础上通过改进激光-物质相互作用过程中材料关键热力学参数的估算方法，提升了理论模型的预测精度；（2）揭示了非均质材料的整形飞秒激光整体均质化去除或高选择性去除的机制，系统地提出了一套利用超快激光实现CFRP高精度可控加工的新方法。具体地，提出了通过调控加工阈值和脉冲去除率两个关键参量实现材料组织整体均质化去除或组分选择性去除的策略，形成了以时域整形法、波长调控法、阈值孵化效应曲线求交法为代表的处理机制；（3）利用前述机理和方法研究成果，开展了利用整形超快激光实现复合材料精密可控加工的应用基础研究，并探索了整形激光精密可控去除机制在更多复合材料的适用性。项目研究形成的“非均质材料整体均质化去除加工方法”成果被鉴定为“国际先进”水平，成为相关科学技术奖励的重要支撑。利用本项目的机理、方法研究成果，通过成果转化与应用研究，形成了指导宇航产品复合材料整形激光加工的工艺规范。研究成果开始批量用于空间飞行器纤维复合材料产品的精密柔性制造。