Study On Repeted Impact Performance Of Selfpiercing Riveted Joints With Foam Metal Sandwich Plates And AA5052/CFRP

With the continuous development of the engineering design field and the new energy industry,structural lightweighting has become a major trend,and more and more new lightweight materials are being used in industrial production,one of which is sandwich panels.The application of new materials has also put forward new requirements for connection methods,and self-piercing riveting has become a new choice for the connection of dissimilar panels due to its unique advantages.In order to study the repetitive impact performance of self-piercing riveted joints between foam metal sandwich panels and different materials,a series of studies on self-pierce riveted joints were carried out based on the preparation of sandwich panels with three different core materials and a comparison of their properties,and a nickel foam sandwich panel was selected for connection with different materials.The sandwich plates were prepared using AA5052 as the upper and lower substrates and three foam metals(nickel foam,iron-nickel foam and copper foam)as the cores,bonded using acrylate structural adhesive high strength structural adhesive.Thickness and mass measurements as well as impact tests were carried out on the three sandwich plates.The experiments show that the prepared sandwich plates have good impact resistance.The damage of nickel foam and iron-nickel foam sandwich plates is manifested by a dent at the impact location,i.e.a crater,while the damage of copper foam sandwich plates is manifested by a coupled deformation of a dent at the impact location and an overall bending of the upper and lower panels.The nickel foam sandwich plate was selected for a subsequent study and was self-punch riveted with 5052 aluminium alloy and Carbon fibre reinforced plastics(CFRP).The performance of the two joints was investigated at different energies and different numbers of impacts by combining the impact response curves and profile morphology changes.At 15 J,the impact force-displacement curve changed from a double-peak to a triple-peak pattern due to changes in the degree and extent of core densification and the propagation rate of impact damage from the second impact onwards.The higher the energy,the more pronounced the curve fluctuation and the more pronounced the impact damage.For the CFRP/nickel foam sandwich panel joint,the impact curve drops abruptly at 10 and 15 J energy as the structure reaches a critical damage threshold load.Both joints are roughly divided into three states during impact damage,but for the CFRP/nickel foam sandwich panel joints,repeated impacts account for more damage to the sheet itself and less damage to the interlocking properties of the joint.In addition,the joints were analysed statically before and after impact in terms of residual strength,energy absorption value and tensile failure form.The analysis revealed that for the nickel foam sandwich plate/AA5052 self-piercing riveted joint,the joint still had good residual strength with increasing number of impacts at 5J energy,while the residual strength decreased with increasing number of impacts at 10 J and 15 J energy.For the CFRP/nickel foam sandwich plate self-piercing riveted joints,the residual strength decreased with increasing number of impacts at all three energies,and to a lesser extent.In addition,the failure of the former is manifested by tearing of the lower panel of the sandwich panel,while the failure of the latter is manifested by multi-mode damage to the carbon fibre composite laminate.