碳纤维增强树脂基复合材料多刃微切削的细观断裂机理

Multi-cutter machining is one of important machining techniques to satisfy the requirements of low-damage and high-efficiency in machining carbon fiber reinforced composite load-carrying structures in aerospace and aircraft fields. The present project deals with the analysis and design optimization of multi-cutter machining tools and techniques. First, a meso-mechanical theoretical model describing the fracture modes of fibers during the machining process is established based on the elastic foundation beam theory, where the constraint effect of matrix on the deformation of fiber is considered. Analytical expressions are derived for evaluating the cutting forces and the debonding between the fiber and the matrix using the meso-mechanical model. Furthermore, a meso-mechanical numerical model of machining a lamina with considering explicitly the fiber, matrix and their interface as well as the interaction with the multi-point cutter is established. Based on this numerical model, the initiation and the evolution of the cutting process is studied via the dynamic approach with a stiffness reduction scheme, a cohesive law, and an explicit time-integration algorithm. The machining parameters and geometry of the multi-point cutter are optimized for improving the machining process. Experiments of machining typical composite laminates using traditional and optimized multi-point cutters are carried out to validate the proposed approaches. The research output of the project will build a theoretical foundation for high-efficient and low-damage machining composites using multi-point cutters.

多刃微切削是碳纤维增强树脂基复合材料空天承力构件低损伤高效加工的重要工艺。本项目围绕复合材料多刃微切削的细观断裂机理与刀具结构优化问题，首先，基于弹性地基梁理论建立受基体约束作用的纤维切削断裂理论模型，研究细观上纤维切削断裂机理和纤维基体界面开裂损伤成因，推导不同纤维角度下的切削力解析表达式，获得基体支撑作用强弱不同时纤维与基体界面开裂条件；进而，将纤维、基体和界面显式建模并耦合刀具作用，发展材料刚度退化方法、界面内聚力法则和显式时间积分算法，进行切削过程的细观动态数值模拟，阐明切削起始和切屑生成全过程的材料细观去除机理；同时基于数值模型，开展细观切削力和开裂损伤指标对单刃几何参数的敏度分析，针对典型多刃刃形开展特征几何参数优化设计，最后通过切削试验验证细观断裂机理和优化方法。项目研究成果可以为复合材料多刃微切削低损伤高效加工工艺和刀具优化提供理论基础。

碳纤维增强树脂基复合材料(CFRP)由于其优越的性能在航空航天等装备领域上得到广泛应用，而碳纤维复合材料的多界面、多相态等特征使其成为典型的难加工材料。本项目围绕碳纤维复合材料构件的多刃微齿切削的材料去除机理、切削力预测和刀具几何形状对加工质量的影响规律以及刀具结构优化开展研究，包括切削力预测模型、宏细观直角/斜角切削有限元仿真、不同几何结构的多刃微齿铣刀对比实验、以及考虑构件弹性变形的切削损伤预测等几个方面。首先，发展了细观层次碳纤维复合材料去除机理和纤维去除切削力理论模型，建立了复合材料多刃切削加工的铣削力预测模型与考虑未切削层弹性变形的钻削分层临界轴向力模型。第二，在有限元仿真方面，开展了复合材料宏观直角和斜角切削有限元分析，对比不同的复合材料损伤起始和演化准则对切削力的影响，得到了切削力系数随纤维角度的变化规律。建立同时考虑纤维、树脂及界面的细观直角和斜角切削加工有限元分析模型，得到了直角切削下不同角度纤维的失效形式和斜角切削下不同刃倾角对于各组成相失效形式的影响规律。第三，在切削实验和刀具结构优化方面，分别开展了单向复合材料直角和斜角切削实验、不同加工参数的铣削及钻削实验，实验测得的切削力与预测切削力对比结果令人满意。开展了不同刀具结构的铣削实验，通过不同刃形和切削刃旋向的铣刀对四种典型纤维角度的单向板铣削实验，获得轴向力和径向力随纤维角度的变化规律和刀具结构对加工表面粗糙度的影响规律。通过对比有无分屑槽多刃铣刀的切削性能，可以看出铣刀分屑槽不仅可以减小铣削轴向力，而且可以抑制铣削毛刺的产生。通过对不同几何结构的刀具进行仿真和实验对比，优化了多刃微齿铣刀的切削刃螺旋角与分屑槽螺旋角。本项目研究成果对碳纤维复合材料多刃切削加工提供理论基础和技术参考。