Study On Stress Regulation And Properties Of High Performance Thermoplastic Composite/Metal Bonding

Due to excellent mechanical properties,high toughness,impact resistance,high damage tolerance,short production cycle,high efficiency,weldability,robust design,reusable and other characteristics,thermoplastic composites are widely used in aerospace,military electronics,automotive and chemical industries.However,the connection between structural parts is essential due to structural design and technology limitations.There are mainly three ways:mechanical connection,adhesive connection,and mixed connection.Among them,the adhesive structure has the advantages of lightweight,high strength,uniform stress distribution,corrosion resistance,and fatigue resistance,and the application range is more comprehensive than the mechanical connection.The thermoplastic composite bonded metal is a hot research topic,but the thermoplastic matrix material has low surface energy and is difficult to bond.Therefore,surface treatment is significant for the performance of thermoplastic composite bonded structural parts,and proper surface treatment can improve the substrate’s surface wettability and bonding strength.In addition,the surface roughness can be increased by grinding the surface of the substrate.The convex and convex structure produced after grinding can not only form a mechanical interlock structure between the adhesive layer but also increase the contact area between the adhesive and the substrate and improve the interface bonding strength between the substrate and the adhesive layer from many aspects.When the thermoplastic composite is bonded to metal,it is necessary to perform surface treatment on the thermoplastic composite and metal and overcome the mismatch problem between the thermoplastic composite and metal thermal expansion coefficient(CTE).Otherwise,the internal stress concentration of the joint will be caused,and the performance of the joint will be decreased after the heating and curing.Because adhesives are generally polymers,polymers expand in a non-linear manner with temperature.Metal materials have isotropy.When the temperature changes,the size changes in different directions are consistent;Thermoplastic composites have anisotropy,and their responses to temperature change vary greatly.If you encounter temperature changes,you must consider the effects of this difference.This paper uses poly(aryl ether ketone)based thermoplastic composite,steel,and aluminum alloy as substrate plates,and the form of a single lap joint is made.First,thermoplastic composites were bonded with the same thermoplastic composites to explore the best surface treatment technology of thermoplastic composites.At the same time,on the basis of the best surface treatment technology of thermoplastic cladding,the work of metal bonding is carried out to improve the surface treatment of metal so that the interface bonding of metal-adhesive layer is no longer the weak point in the whole bonding structure.Surface treatment using sandpaper grinding or sandblasting physical treatment,after acetone and ultrasonic cleaning surface,the use of plasma to treat the bonded area,according to the production standard adhesive adhesive adhesive joint.Put it into the press to increase pressure and heat curing,and finally test its shear strength by improving the surface treatment process to improve the strength of the adhesive and detect the change of the internal stress during the curing of the adhesive.In this process,a 3D microscope,scanning electron microscope(SEM),contact Angle measuring instrument,energy dispersive spectrometer(EDS),X-ray photoelectron spectroscopy(XPS),and universal testing machine were used to test the surface roughness,microstructure,surface tension,surface chemical composition and bonding strength of the bonding structure of the substrate.Then the differential scanning calorimeter(DSC)was used to explore adhesives’ curing reaction kinetics and improve adhesives’ curing process.Fiber Bragg grating(FBG)was used to analyze the internal stress of the bonded structure.According to the characterization results,the relationship between the curing process and the internal stress in the bonded structure was investigated.Then the stress concentration problem in the joint caused by the mismatch of thermal expansion coefficient between the thermoplastic cladding and the metal was regulated.