Effect Of Modification Of Heterotype Structure Of The Surface Of Aluminum Alloy On Bonding Properties Of Aluminum Alloy To Epoxy

The bonding strength between metal and plastic is closely related to the structure and state of the bonding interface between them.In order to improve the connection performance between metal and plastic,aluminum alloy with microstructure on the surface was prepared by 3D printing technology,and then different surface modification treatments were carried out.Through mechanical interlocking and chemical bonding between aluminum alloy and epoxy resin,the bonding performance can be improved.The time process of different modification methods,chemical bonding of modified layer and shear strength,tensile strength and delamination resistance of modified composite plate were studied,and the influence of different modification methods on the connection performance of composite plate and the bonding fracture mechanism were discussed.The best time and process for aluminum alloy matrix modification in silane coupling agent KH-550,KH-570 and polydopamine solution are 3min,3min and 24 h,respectively.The surface defects of the modified layer prepared under this process are the least,there is no obvious hole gap,and it is completely covered on the surface of aluminum alloy matrix,with the best molding quality.The relative contents and chemical bonds of the elements on the surface of the aluminum alloy changed obviously after the modification.Al-O-Si and Si-O-Si chemical bonds were formed on the surfaces modified by coupling agents,and C-OH and C=O chemical bonds were formed on the surfaces modified by polydopamine.The shear test results show that the shear strength of the composite plates without modification and treated with polydopamine,KH-550 and KH-570 is about22 MPa.The failure mode of the four composite plates is mixed fracture.The tensile and three-point bending test results showed that the silane coupling agent KH-570 had the best modification effect among the three modification methods,and the tensile strength of the composite plate treated by KH-570 reached 39.5MPa.Compared with the unmodified aluminum alloy,it is increased by 76%.The failure mode is the cohesive fracture of epoxy resin.The maximum load before delamination reached 0.125 k N,which was 47% higher than that of the unmodified aluminum alloy.The failure and fracture modes are the cracking failure of epoxy resin matrix and the delamination failure of bonding interface.