Experimental Study On Composite Hole-making Of Thick Plate CFRP With Picosecond Laser And Mechanical Method

Carbon fiber composite material(CFRP),as a high-performance composite material,has an increasingly wide range of applications.A large number of holes need to be processed during the connection process.At present,the processing method is mainly mechanical hole making,which has defects such as delamination,and the rapid tool wear leads to high cost of use,so it is gradually replaced by new processing methods.As a new method,CFRP laser drilling overcomes the delamination defects of mechanical drilling because there is no force,but there are defects such as heat-affected zone and taper when laser drilling.This paper proposes a combined processing path of laser and mechanical methods for the preparation of large holes in thick plate CFRP.First,the prefabricated bottom holes are cut by laser ring,and then the metamorphic layer is removed and the taper is reduced by mechanical hole expansion.Design and build a test platform for laser ring cutting hole making and mechanical hole reaming,explore the relationship between process parameters and processing quality during laser ring cutting hole making,calculate the T800 ablation threshold and analyze the formation mechanism of various damages.After the prefabricated holes of the thick plate CFRP material were prefabricated,the dynamic simulation of the mechanical holemaking process was carried out.The main research contents of this experiment are as follows:(1)The advantages of laser processing CFRP holes are listed and their feasibility is verified.The mechanism of the cold working effect of the pulsed laser with a pulse width of 10 ps was revealed.The reason for the formation of the taper in the process of cutting the thick plate CFRP ring was established from the shielding effect and the spot dispersion.The bottom bowl shape processed by the two-dimensional galvanometer The reason for the formation of the cross section is explained.(2)The carbon fiber ablation threshold in CFRP-T800 material was calculated by the heat transfer calculation model,which confirmed the high efficiency of laser processing fiber reinforced materials.By fitting and predicting the cut-off inner diameter threshold value of the blind hole of CFRP,the inner diameter value of the ring cut with different plate thicknesses and different apertures is obtained,and the optimal laser prefabricated hole scanning path is provided.The relationship between bottom surface and sidewall roughness is analyzed theoretically.(3)The relationship between laser process parameters and HAZ(heat affected zone)and taper during blind hole processing was investigated in orthogonal experiments,and better power and repetition frequency were obtained.The optimal scanning speed was obtained through exploration,and the prefabricated hole test was carried out using the optimal scanning path and processing parameters to obtain three groups of prefabricated holes with different plate thicknesses and diameters,and their tapers were compared.(4)After using the optimal laser prefabrication parameters for laser prefabrication,the dynamic simulation of hole reaming was carried out,the reasons for the change of axial force in the reaming stage were analyzed,the exit damage of reaming by different tools was compared,and the optimal expansion was determined.Hole cutters,single-factor hole reaming experiments were carried out on prefabricated holes with different rotational speeds and feed speeds,and the optimal mechanical hole reaming process parameters were obtained by comparing the orifice morphology of different parameters.A qualitative analysis was performed.