Study On Drilling Damage Mechanism Of Carbon Fiber Reinforced Plastic Pipe

Carbon fiber reinforced plastic(CFRP)is a new type of composite material with resin as matrix and carbon fiber as reinforcing phase.It has a series of excellent properties,such as lightweight,high strength,corrosion resistance,fatigue resistance,designable performance,and so on.The pipeline components made of CFRP have become the preferred material to effectively reduce the structural weight of conveying systems in aviation,aerospace,and other engineering fields.In the assembly process of CFRP pipeline components,it is necessary to make holes for small-diameter CFRP pipes with different radii of curvature.However,most of the existing machining methods are drilling holes on the upper and lower arc surfaces respectively,which is difficult to ensure the coaxiality of the upper and lower holes,thus affecting the assembly accuracy.And in the processing process,the entrance and exit are prone to delamination,burr,tear,and other damage defects.Because of the above problems,this paper makes theoretical analysis,finite element modeling and simulation,and experimental research on CFRP pipes with different drilling methods(reverse and forward curvature)and different radius of curvature.Based on clarifying the drilling damage mechanism of CFRP pipe,the influence of machining parameters on drilling axial force,delamination,burr,and other machining damage defects is discussed,and reasonable suggestions on the selection of machining parameters are put forward.Furthermore,the suppression of drilling damage and defects of CFRP pipe is studied using support and air cooling.The main research contents are as follows:(1)Based on the single-hole drilling method of small diameter CFRP pipe,a finite element simulation model of CFRP pipe’s reverse and curvature drilling is established.The material removal process under different drilling methods is discussed.The contact relationship between twist drill and CFRP pipe in the process of drilling with reverse and clockwise curvature is discussed.The formation mechanism of the entry and exit delamination defects in the two drilling processes and the time-dependent characteristics of drilling axial force is emphatically analyzed.(2)Four three-dimensional finite element simulation models of CFRP pipe drilling with different radii of curvature are established to explore the drilling process of CFRP pipe with different radii of curvature.The influence of curvature radius on the axial force of CFRP pipe drilling is studied and analyzed,the drilling quality of CFRP pipe under different curvature radii is discussed,and the simulation model is verified by experiments.(3)This paper discusses the influence of processing parameters on the drilling of small-diameter CFRP pipe,focuses on the influence law of processing parameters on the inlet and exit morphology and hole wall quality of reverse and forward curvature drilling,explores the influence of processing parameters on the drilling quality of CFRP pipe with different curvature,reveals the influence of processing parameters on the formation of material processing damage and defects,and puts forward reasonable suggestions on the selection of drilling processing parameters of CFRP pipe.(4)The methods of support,air cooling,and support + air cooling are used to suppress the drilling damage defects,and the drilling quality is compared with that without the suppression method.It is found that the support method can provide constraints for the exit side,the air cooling method can reduce the accumulation of cutting heat in the drilling area,and the support + air cooling method can better inhibit the delamination and burr damage on the exit side,and have better hole wall quality.