Peridynamics Modelling Method Of Carbon Fiber Reinforced Polymer Materials And Its Applications In Cutting Process

Carbon Fiber Reinforced Polymer(CFRP)has been widely used in the aircraft industry for its light weight,high strength,anti-corrosion and excellent fatigue-resistant properties.In order to meet the assembly requirements,much cutting process need to be conducted in the practical assembly,such as hole-making,trimming and milling.However,due to the heterogeneity and anisotropy characteristic,the cutting mechanism of CFRP is complicated and its machining quality is difficult to meet the requirements.With the development of computer technology,numerical analysis method become the most important ways to research CFRP cutting mechanism and optimize cutting parameters.At present,most of the numerical method based on continuum mechanics in which the continuity assumption is necesary.However,there are limitations in continuum mechanics when it is applied to analysis large deformation and discontinuity problems in CFRP cutting process.In recent years,a meshless method,Peridynamic(PD),which based on the nonlocal theory,gradually becomes a research hotspot.This method is no longer based on the continuity hypothesis,but applies integral equation instead of differential equation to describe the motion of material points,so it has advantages in the analysis of large deformation,fracture and damage problems.However,there are few researches focused on the analysis of PD based CFRP cutting process,and there is no effective PD analysis method been proposed for CFRP cutting process.Aimed at above problems,four parts of specific contents are presented as follows:Based on the analysis of the CFRP machined surface morphology under different fiber orientation,the fiber fracture mechanism in the cutting process was determined.By applying the energy method and microscopic cutting force model,the influence of fiber orientation on CFRP cutting force is revealed.The above results provide the theoretical basis for PD model for CFRP cutting process.Based on the anisotropy and heterogeneity of CFRP materials,a BB-PD CFRP model was established by introducing fiber bond and matrix bond,and the failure criteria of fiber bond and matrix bond during CFRP cutting were proposed based on the fiber fracture mechanism during the cutting process.The mechanism of materials removal and surface defects formation in the CFRP orthogonal cutting process are presented,and the accuracy of the model is verified by the corresponding expriments.For optimize PD CFRP model,the BB-PD modelling method is extended to the CFRP non-ordinary state PD model.The mathematical relationship between bond parameters and CFRP engineering parameters in the model was established,and the failure criteria of fiber and matrix bonds were established based on Maximum stress and Hashin failure criteria.The contact model between the tool and the workpiece material is established according to the punishment algorithm,and the contact constant is optimized to make the model applicable for the non-local contact problem.Finally,the accuracy of the model in the prediction of cutting force and machining surface defects is verified based on tensile and cutting experiments.Considering the structural characteristics of multidirectional laminates CFRP,the interlamination normal and shear bonds were introduced in unidirectional CFRP nonordinary state PD model.Critical elongation of normal and shear bonds has been obtioned by experiments.The multidirectional CFRP PD model is established,the accuracy of this model is verified by a series of experiments.The cutting damage and cutting force of in CFRP cutting process can be accurately predictied by this model.Based on the above researches,the fiber fracture mechanism has been revealed in the cutting process of CFRP,and the CFRP PD model has been built.The outcomes of this paper have important reference value for CFRP numerical simulation method and improvement CFRP machining efficiency and quality.