Design And Mechanism Of Resistance Welding Interface Enhancement Of Thermoplastic Aerospace Composites

Thermoplastic composites are becoming more and more widely used in the aerospace industry,and their effective and reliable connection is a key factor in their application to aircraft.Resistance welding technology has become one of the main directions for the development and application of thermoplastic composite materials in the future due to its design and reliability.In this paper,glass fiber reinforced polyetherimide(GF/PEI)composites were selected as welding objects.The influence of welding parameters on the welding quality of GF/PEI composites was studied and the best welding process was determined.The welding interface was enhanced from the two aspects of material and process,and the interface enhancement mechanism was revealed.First,a thermoplastic composite resistance welding platform was built,and thermocouples and pressure sensors were used to monitor and record welding parameters in real time to ensure the accuracy and repeatability of the welding process.The best process for resistance welding of GF/PEI composites was determined through a series of comparative tests:a stainless-steel mesh with a porosity of 25%was considered the best choice for heating element,the welding voltage and current were 20V and 12A,the welding time was 120s,and0.2MPa was selected as the best welding pressure.The welded interface was reinforced from a material perspective.Firstly,the enhanced design of the welding interface of the GF/PEI composite material was realized by the carbon nanotube(CNT)modified heating element grown by the flame method.The strength of the welded joint increased first and then decreased with the growth time of CNT(t_g),and reached a maximum shear strength of 39.2MPa at t_g=10min.Secondly,the GF/PEI composite welding interface was strengthened by using chopped aramid fiber(AF),glass fiber(GF)and carbon fiber(CF)co-cured with PEI resin to form a composite film.When CF was used as the interface reinforcing material,the welded joint has a maximum shear strength of 35.97MPa.The welding interface was enhanced from a process perspective.The strengthening of the welding interface of the GF/PEI composite material was mainly achieved by etching the heating element.When etching time(t_e)and welding time(t_w)were 30min and 150s,respectively,the joint strength reached a maximum of 35.44MPa.Therefore,the addition of interface reinforcing materials and surface treatment of heating elements are effective methods to improve the mechanical properties of composite resistance welding.