Experimental Study Of Rotary Ultrasonic Vibration Core Drilling For SiC/GFRP Laminate Composite Plate

Ceramic composite armor components made of which engineering ceramics and fiber reinforced polymer(FRP),it has the advantages of low density,high specific strength and large elastic modulus.Because of its light weight and high protection capability,it has been widely used in the field of armor protection.A large number of holes are required to be process after manufacturing in order to manufacture fitting and joining surfaces.However,the armor ceramic and FRP are all difficult-to-machine and their performances are distinct,so using traditional technology processing,serious drilling damages such as ceramic collapse edge,fiber fracture,etc.frequently occur at drilling-exit area,so it is more difficult to process composite components which restrict the application in armor protection field.Therefore,this paper adopts diamond trepanning bit and rotary ultrasonic vibration machining technology to carry out experimental research on the core drilling process of SiC ceramics,glass fiber reinforced polymer(GFRP)and SiC/GFRP laminated composite plate.Firstly,the removal mechanism and damage evolution form of each component material in the machining process were analyzed.The influence mechanism of thrusting force on hole making damage was studied by establishing the hole exit defect model of SiC ceramics and GFRP.Based on the analysis of process characteristics of rotary ultrasonic vibration core drilling,the reason that it can reduce axial force is revealed.Through comparative experiments,the influence rules of machining parameters on axial force were summarized,and the thrusting force prediction model of SiC ceramics and GFRP was established.The results show that the axial force of SiC ceramics and GFRP decreased by 30.3% and 21.9%,respectively.Increasing the spindle speed or decreasing the feed speed can reduce the axial force.The average error of axial force prediction model is 4.1% and 8.78%,respectively.Secondly,the wear patterns and characteristics of diamond abrasive particles and the body materials of the drill head were observed by SEM,the wear mechanism of end and side abrasive particles was studied,the influence of technological methods on groove scratches on the surface of the body was analyzed,and the cause of small gap on the end face of the drill bit in the process of drilling was explained.The results show that most of the abrasive particles on the end face are broken and peeled off,while the abrasive particles on the side are worn in the form of slight erosion,edging and equalization.The abrasive edges are seriously worn and slightly ablated during conventional processing.Ultrasonic vibration can avoid the abrasive debris on the body to continue to scratch,to prevent the end surface of the deep groove.Under the combined action of alternating stresses such as extrusion and friction,tiny cracks are formed on the surface of drill bit,which gradually expand until fracture occurs.Finally,the hole making experiments of SiC/GFRP laminated composite plate were carried out to study the inhibition mechanism of ultrasonic vibration on the damage of backplane hump and laminated interface separation,and the influence of machining methods on the micro-morphology of hole walls was discussed.The change rule of the influence of technological parameters on the surface roughness of hole walls was summarized.The experimental results show that the rotary ultrasonic vibration core drilling technology can ensure the close bonding of the laminated interface at the hole entry,greatly reduce the height of the uplift,and improve the integrity of the hole surface.A large number of cracks and pits remain on the surface of SiC ceramic materials.Conventional processing is easy to cause the material internal collapse.However,ultrasonic vibration increases the proportion of plastic removal,so that the surface of SiC ceramic materials only forms small pits like fish scales.The removal methods of GFRP mainly include fiber fracture and resin crushing.Compared with conventional processing,additional ultrasonic vibration makes the fiber fracture smooth and tidy,each layer is clearly recognizable,and the resin matrix does not have a large area of fragmentation and coating.Increasing the spindle speed is beneficial to reducing the hole roughness of composite components.Through the above researches,the influence law of ultrasonic vibration on axial force and machining quality is revealed,the material removal method and diamond bit wear mechanism in the machining process are illustrated,and the damage of SiC/GFRP laminated composite plate is effectively inhibited.It provides theoretical and technical support for solving the problem of high efficiency and low damage hole machining of SiC/GFRP laminated composite armor components,and has important engineering application value.