Chip Formation Mechanism And Machining Defects Suppression Of CFRP Composites

With the continuous development of science and technology and the increasingly harsh working conditions,metal and non-metallic materials of single structure cannot meet the actual engineering needs.Therefore the composite materials came into being.CFRP composites have been widely used in aerospace,national defense industry,energy transportation and other fields because of their corrosion resistance,high strength,high specific modulus and low thermal expansion coefficient.Taking aircraft design as an example,the use of composite materials has become an important index to evaluate international competitiveness of aircraft.The application range has gradually developed from the secondary structure to the main structure.As the assembly process of CFRP composite materials is mostly in the form of riveting or bolting,therefore the hole making quality of composite materials has become a key factor affecting the life and strength of the composite members.The composite material features anisotropy,low interlayer bonding strength and non-uniformity,so is prone to tearing defects,burr defect and delamination defects and other defects in the drilling process,making it typically difficult to process.Aiming at the above problems,this paper uses the combined method of theoretical analysis and experiment to study the drilling process of CFRP composite.The paper investigates the relationship between composite materials and cutting tool,the removal mechanism of composite materials and the mechanism of its machining defects,which provides a reference for the CFRP processing parameters the selection of composite materials and the design of drilling tools.The main research contents are as follows:Firstly,construct the analytical model of drilling forces and use the contact theory in the process of analysis of the horizontal edge top pressure effect.In accordance with the oblique cutting process,divide the main cutting edge area into three parts to consider respectively and combine with the cutter geometry parameters,fiber orientation and process parameters influence on cutting force.Secondly,use diamond coated drill and PCD drill straight groove respectively for the CFRP composite materials drilling experiment.Analyze these two kinds of drilling process,generalize how drilling process parameters influences drilling axial force and compare the above two kinds of drilling axial force produced in the cutting process.Thirdly,analyze the causes of tearing defects on the two kinds of drill hole entrance in the drilling process.Analyzes how process parameters influence tearing defects.Observe and analyze the morphology of these two kinds of drill hole entrance.Observe the wall shape of two drills and analyze in what way fiber direction and cutting drill angle influences the surface roughness of the hole wall.Compare the surface roughness of these two drill holes and measure their roundness.