CFRP/合金叠层结构制孔界面缺陷物理建模与数值仿真研究

This project aims to perform the physical modeling and numerical simulation of interface defects in drilling CFRP/Ti and CFRP/Al stacks which have been widely used in the modern aerospace manufacturing industry. The fundamental physical properties of CFRP/alloy stacks will be firstly determined using the mechanical testing. Then, the constitutive models of CFRP/alloy stacks based on the thermo-mechanical coupling effects and damage accumulation will be established using the theory of composite mechanics, interface mechanics, heat transfer, continuum damage theory, etc. Based on the re-development technique of finite element simulation and solid modeling technology, the micro-macro mechanical orthogonal cutting models and three-dimensional drilling models of CFRP/alloy stacks will be developed with the aim to reveal the activated mechanisms dominating the interface damage formation under four different stacking sequences (CFRP→Ti, Ti→CFRP, CFRP→Al and Al→CFRP) in a micro-scale level, and the predictive models of interface defects will also be proposed. Moreover, the established constitutive models, FE cutting models and simulation results will be rigorously verified by the CFRP/alloy cutting experiments. A comprehensive evaluation system of interface defects and a damage-free drilling process of CFRP/alloy stacks will be eventually put forward. The research results of the present project can provide theoretical guidance and technical support for realizing the standardization of high-quality drilling and assembly of large-scale aircraft structures in the aerospace industry.

本项目以航空制造领域常用CFRP/Ti和CFRP/Al叠层结构为研究对象，开展叠层结构制孔界面缺陷物理建模与数值仿真的研究；首先通过材料力学实验获得叠层结构基本物理力学性能参数，然后基于复合材料力学、界面力学、传热学及连续介质损伤等理论建立基于力热耦合效应与损伤累积的叠层结构切削本构模型；应用有限元二次开发及实体建模技术，建立CFRP/合金正交切削微宏观模型和三维钻削有限元模型，从微细观尺度揭示四种叠层顺序模式下（CFRP→Ti、Ti→CFRP、CFRP→Al和Al→CFRP）界面缺陷形成机理并建立叠层界面缺陷预测模型；最后应用CFRP/合金切削实验对叠层切削力热损伤本构模型、切削有限元模型及数值仿真结果进行可靠性验证，提出叠层制孔界面缺陷综合评价体系并制定低缺陷制孔工艺方案。本项目研究成果可为航空制造领域实现大型飞机叠层结构件高质量制孔装配工艺规范化提供理论指导与技术支持。

本项目针对当前航空航天制造领域存在的有关叠层结构制孔工艺适配性差，界面切削缺陷本构与预测模型缺乏及界面缺陷综合评价体系缺失等技术问题，以常用CFRP/钛合金为研究对象，开展叠层制孔界面缺陷物理建模与数值仿真的研究，建立了基于力热耦合效应与损伤累积的叠层结构切削本构模型；并应用有限元二次开发及实体建模技术，构建了CFRP/钛合金正交切削微宏观模型和三维钻削有限元模型，揭示了不同叠层顺序和切削参数影响下的界面缺陷形成机理并完成了叠层结构界面切削缺陷评价研究。结果表明：叠层结构的材料去除机制主要由脆性断裂和弹塑性变形所主导，绝热剪切的热塑性失稳与第一变形区内裂纹的形成和扩展主导了钛合金切屑的形成过程。纤维铺层方向和切削顺序是影响叠层结构切屑分离过程的关键因素。叠层界面为最具挑战性的切削区域，该区域损伤主要受叠层顺序影响，其缺陷形式为底层钛合金高温高硬切屑排出过程中对界面区域的机械刮擦和热侵蚀作用；同时，界面切屑分离模式的快速转变极易引起切削力的急剧变化，从而导致加工缺陷的产生并降低刀具使用寿命。为降低叠层界面切削损伤，提高叠层结构制孔表面质量，应选用由钛合金切向CFRP的钻削顺序、异型结构钻头以及优化的切削工艺参数。本项目研究结果为航空航天制造领域实现飞行器叠层结构件高质量制孔工艺规范化提供了理论指导与技术支撑。