The Cutting Process Technology And Its Application Of Carbon Fiber-Reinforced Plastic

Carbon fiber reinforced plastics(CFRPs)have a wide application prospect in aviation,aerospace and national defense industries due to their high specific strength,high specific modulus etc.Usually,various kinds of afterprocessing are necessary to meet the assembly requirements after the composite components forming.However,a variety of machining problems,such as burrs,delamination and cutting tool wearing etc,are easily caused during machining.This thesis regards the applications of the processing technologies of the shell surface of the missile as the research object.And around the influences of the process,such as the machining mechanism,the wear of the tool,the tool materials and tool geometry,the machining parameters etc.,the cutting process technologies of CFRP composite have been studied by experimental and theoretical analysis.Taking the milling of the CFRP as the research object,the machining mechanism of CFRP materials were studied by experimental observation.The results shown that the typical types of the chips were powder-block and curl in the milling method when the fiber fabric stood horizontally.In the milling method when the fiber fabric stood vertically,the typical types of the chips were long-powder.Using the up milling way in actual production,the machining defects can be decreased.In the cutting process,the fracture of the fiber presented brittle characteristic,and under different stress the types of the fiber micro-fractographs were different.The typical types of the fiber micro-fractographs were smooth planar,oblique,mult-plane,irregular,corrugate,long oblique with irregular,etc.A tungsten carbide uncoated end milling cutter(YG6X,uncoated),a DLC coated end milling cutter and a PCD end milling cutter were used to do the slot milling tests of the CFRP.respectively.And the wear character and the wear mechanism of the tools have been analyzed.The results shown that there were abrasive wear and epoxy-bonded on these three kinds of cutters.But the coating break off was the peculiar wear patterns to the DLC coated cutter,and the largely wastage was the peculiar wear patterns to the PCD cutter.In addition,the drilling tests results and the milling tests results of the CFRP shown that the DLC coated cutter and the PCD cutter were both the ideal tools for the machining of CFRP.The drilling tests were carried out with different structure bits and the results noticed that the drilling defects and the drilling forces would increase greatly when the bit diameter exceeded 10 mm.Using a mult-chisel-edge bit or a tapered drill-reamer to drill on the CFRP.the drilling defects could be obviously decreased.And the defect factor of the tapered drill-reamer was the least.For a more particular knowledge of the drilling process of the tapered drill-reamer,the drilling model and the thrust force thresholds model of it were built,and the forming process of the defects on the hole exit was analyzed,the reasons for lesser defects on the hole exit also was analyzed,and the values of the thrust force thresholds at the onset and at the propagation of the delamination were obtained.The influences of the tool material,of the tool structure and of the milling way etc to the cutting forces and to the machining defects were analyzed in the milling tests of CFRP.In order to reduce the cutting force and the delamination factor,the orthogonal experiment,in which the range of the cutting speed Vc,of the feed rate f and of the cutting depth ap were 63～109m/min,0.02～0.18mm/r and 1～3mm respectively,was carried out with a PCD end milling cutter.And the optimal combination of Vc,f and ap was obtained when they were 63m/min,0.02 mm/r and 1mm respectively.To investigate the cutting process and the slotting defects,the slotting tests of the CFRP were carried out,using the T-slot cutters.Based on the theoretical analysis and the experimental research,the formation and the change rule of the slotting defects were analyzed.Then the range of the appropriate feed rate per tooth was obtained.Based on these studies,the influences of the tool material,of the tool structure,of the milling way and of the processing parameter etc to the slotting defects and to the cutting forces were analyzed in the further slotting experiments.Some experiments of the CFRP composite components were carried out.And the machining process parameters(cutting speed Vc,feed rate f and cutting depth ap)of the turning,of the boring and of the slotting in the hole were determined.The reasonable selection of the blade and of the tool path was obtained.And.then,on the basis of the studies of the drilling,of the milling,of the turning and of the boring,the machining of the 120°flanks,the faces,the outer circle,the deep hole and the slots in the hole of the component were finished under the machining processing route determined.In the processing of the composite components,the tool performance and the processing quality were effectively protected.