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碳纤维增强树脂基复合材料(CFRP)在细观上呈现纤维、树脂及界面组成的混合态,其切削加工过程的实质为刀具作用下材料细观层面的破坏至切屑宏观形成的演化过程。为了揭示CFRP切削加工过程中材料的细观破坏,建立了CFRP切削的细观有限元模型。该模型在几何上包含了纤维、基体及界面等组成相,而不是使用传统的等效均质建模方法。各组成相不仅考虑了各自不同的材料本构,而且为了能够模拟材料破坏,还将各组成相材料的失效及演化准则考虑其中。该模型可从细观层面更真实地模拟不同纤维角度CFRP单向板切削过程中纤维/基体断裂、界面开裂及演化的过程。仿真结果表明:不同纤维角度下CFRP细观破坏不同,切削0°CFRP时以界面开裂和纤维弯断为主;切削45°/90°CFRP时主要是刀具侵入工件,纤维基体被压断;切削135°CFRP时则以纤维弯曲断裂为主,断裂面往往在加工面以下。通过实验显微在线观测手段验证了模拟结果的正确性。
Carbon fiber reinforced resin matrix composite (CFRP) presents a mixed state of fibers, resins and interfaces in the meso. The essence of the cutting process is the fracture of the material micromechanical plane under the action of cutting tools, and the evolution of chip macroscopic formation. In order to reveal the meso-damage of CFRP material, a micro-finite element model of CFRP cutting was established. Instead of using the traditional equivalent homogenization modeling method, the model geometrically contains the constituent phases such as fiber, matrix and interface. The compositional facies consider not only their different material constitutive states, but also the failure and evolutionary criteria of each constituent phase material in order to be able to simulate material failure. The model can simulate the process of fiber / matrix fracture, interface cracking and evolution in the cutting process of CFRP unidirectional slabs at different fiber angles more accurately from the microscopic level. The simulation results show that the microscopic destruction of CFRP at different fiber angles is different. When cutting 0 ° CFRP, interfacial cracking and fiber bending are dominant. When cutting 45 ° / 90 ° CFRP, the main part is the tool intruding into the workpiece and the fiber matrix is crushed. At 135 ° CFRP, the fiber is mainly bent and fractured, and the fracture surface is often below the working surface. The correctness of the simulation results is verified by experimental microscopic online observation.