Numberical Analysis Of Damage Mechanism Of Carbon Fiber Reinforced Polymer In The Orthogonal Cutting Process

Carbon fiber reinforced polymer(CFRP)has been widely used in aviation,military,automotive and other industries because of its good mechanical properties and physical and mechanical properties.However,due to the mixed statement of reinforcement fiber,matrix resin and interface composition in the microstructure of CFRP,which can easily lead to fiber matrix debonding and matrix cracking,delamination and burrs and other defects,and accompanied by material surface damage.The failure of the material can lead to the expansion of the crack or the further destruction of the composite material.Therefore,it is of great practical significance to study the damage mechanism of CFRP cutting process.In this paper,based on the macro modeling and microscopic modeling of CFRP,the influence of multi-factors on the sub-surface damage in the cutting process is analyzed by using the orthogonal experiment.The surface damage is dynamically studied and the influence of ultrasonic vibration-assisted cutting on the CFRP cutting process is analyzed and compared.In the aspect of macro modeling,the sequence of influential factors to the depth of sub-surface damage(Dm)was as follows:fiber orientation angle>tool edge radius>depth of cut>tool rake angle.Fiber orientation angle and its interaction with the tool rake angle had significant effect on the depth of sub-surface damage.The contribution rate was 48.12%and 10.86%respectively.When the fiber orientation angle was 0°and 45°,the machined surface was smooth.When the fiber orientation angle was 90°andl35°,there were obvious processing crack defects and surface topography profile fluctuated greatly.The results obtained were consistent with the processing defect trends of experimental results.The depth of subsurface damage,matrix cracking and crushing damage under different cutting modes showed different trends with the vibration frequency and amplitude.When the fiber orientation angle was 90°and 135°,due to the special properties of the large fiber direction angle cutting,the subsurface damage depth at different frequencies in the CDVA cutting mode was much higher than that of conventional cutting.When the fiber orientation angle was 90°,under the action of the 40KHz frequency,the EVA mode also had the defects of cracking and damage.In the aspect of micro modeling,the CFRP of different fiber directions showed different damage failure modes under the action of cutting tools.When the fiber orientation angle was 0°,the main failure mode of fiber was bending fracture.When the fiber orientation angle was 0° and 45°,fiber was under compression stress effect in the near tip side and was subjected to tensile stress in the side away from the tip.When the fiber orientation angle wasl35°,the tip and rake angle of tool caused fiber and matrix extrusion and bending failure fracture,with the serious cutting defects.When the fiber direction angle was 0°,the destruction was all above the cutting surface in the three kinds of cutting modes with good cutting quality.When the fiber direction angle was 45°,under the action of the EVA mode,the defect of the edge was generated with the serrated surface.When the fiber direction angle was 90°,because of the front and rear vibration of the tool,the springback phenomenon of the material was relieved and no obvious damage was found.When the fiber direction angle was 135°,the workpiece had different degrees of surface damage in the three kinds of cutting modes.The results of this paper can provide theoretical basis for the further study on the sub-surface damage of CFRP cutting process and the mechanism of ultrasonic vibration-assisted maching.