Mechanics Modeling And Optimization Of Technological Parameters For Cutting Process Of CFRP Composites

Carbon fiber reinforced polymer(CFRP)composites has rapidly develop into the main materials in aeronautical structures due to its excellent mechanical properties.However,CFRP composites is a typical difficult to cut materials,which easily produce the defects and tool wearing fast in the machining process.Based on the method of multiscale analysis in the paper,the mechanism of material removal and damage formation was studied in the machining of CFRP composites.These provide the theoretical guidance for the performance evaluation of composite materials,and present the great meaning to apply CFRP composites with high level and low defects in aerospace industry.Overall,the main contents of this paper are pointed as follows:(1)The unidirectional CFRP composite with long fiber was taken as the research object,and the relationship between the mechanical properties of CFRP composites and its constituents was study.With considering the interphase,the representative volume element(RVE)of single fiber was established,which composed by fiber,interphase and matrix.By using the modeling method of the bridge model,the static mechanical model of unidirectional CFRP composite was then established.And the effect of interphase parameters on the macro-mechanical properties of composites was analyzed by using the model.Furthermore,the Maxwell element was introduced into the interphase,the dynamic mechanics model was established and the effectiveness of this model was done for unidirectional CFRP composites.These two models can be taken as the theoretical and material foundation for the finite element analysis of CFRP composites machining.(2)For the unidirectional CFRP composites included interphase,the mechanism of material removal,machine damage and heat generation was respectively studied by using the numerical simulation combined with the experiment.Based on the geometric characterization of CFRP composites,the three-dimensional geometric model composed by fiber,interphase and matrix was conducted.After the material constitutive model,initial damage and evolution criterion of these constituents were defined in the ABAQUS,the dynamic simulation of finite element cutting model for four typical fiber orientations of CFRP composites was then performed.By using the morphology of machined surface chip,the accuracy of the simulation results was verified.Based on the simulation results,it is found that the chip formation,machining damage,surface quality and cutting temperature have obvious directivity.(3)A multicale prediction model of cutting force was established for the unidirectional CFRP composites included interphase,and then a cutting force model of multidirectional CFRP composites was further obtained.Based on the RVE,the type of fiber fracture was analyzed under different fiber orientation angles,which can be divided into crushing-dominated and bending-dominated fracture.By using the contact mechanics,mechanics theory of composite materials and other related theories,the multicale prediction model of cutting force for the unidirectional CFRP composites was established,and the experimental test was done to verify the model.Based on the experimental data of unidirectional CFRP composites,a milling force model of multidirectional CFRP composites was further obtained,in which the effect of fiber orientation and the equivalent thickness of chip on cutting force was considered.And the accuracy of the prediction model was then verified by the experimental data.(4)Based on the anisotropy of unidirectional CFRP composites,the effect of various technological parameters on the cutting force and subsurface damage was comprehensive investigated by the experiment and simulation methods.The variations of the cutting force and subsurface damage were analyzed by experiment and simulation firstly.By using the finite element cutting model,the change of material parameters(fiber orientation and fiber volume fraction),cutting parameters(cutting speed and depth of cut)and tool parameters(rake angle and edge radius)influence on the cutting force and subsurface damage were then discussed in detail.Furthermore,the multiple factors analysis of the technological parameters was conducted to quantitatively obtain the effect of various parameters and their coupling on the cutting force and the subsurface damage.All these results provide a strategy for optimizing the technological parameters.