Research On Laser Joining Technology Of Aluminum Alloy And CFRTP Based On Surface Etching

The contemporary aircraft manufacturing industry puts forward practical requirements for new materials and new technologies with the rapid development of advanced technology.Carbon fiber reinforced thermoplastic composite(CFRTP)has the advantages of high specific strength,excellent corrosion resistance and heat resistance and has been widely used in aircraft components.Meanwhile,compared with mechanical joining and adhesive bonding,the laser joining technology between aluminum alloy and CFRTP has lots of advantages of flexible process,fast processing efficiency and high precision.Due to the differences of properties between aluminum alloy and CFRTP,there are many challenges in laser joining technology when it is used to join aluminum alloy and CFRTP.In this work,the laser joining experiments of single lap structures were carried out between 6061 aluminum alloy and CFRTP.More attention has been paid to the effects of surface etching structures of 6061 aluminum alloy on the joint interface fusion characteristics and joint strength.Firstly,the finite element model of laser joining process between non etched 6061 aluminum alloy and CFRTP was built.The simulation of temperature field in laser joining process was carried out.The accuracy and applicability of the composite heat source model of “Gaussian surface heat source and exponential rotating parabola heat source” were verified by comparing the simulation results with the experimental results.The effects of different process parameters on the molten pool morphology of aluminum alloy and joint interface forming have been studied to obtain a better process parameter range with the laser power from 1200 W to 2200 W and the welding speed from0.01m/s to 0.02m/s.Secondly,the laser joining experiments of single lap structures of non-etched 6061 aluminum alloy and CFRTP were carried out based on the better range of process parameters obtained by temperature field simulation.The effects of different process parameters on aluminum alloy weld seam forming,microstructure,interface morphology and elements distribution have been studied to determine better laser joining process parameters with laser power of 2000 W and welding speed of0.015m/s.Thirdly,the orthogonal experiments of laser etching on the 6061 aluminum alloy surface were designed and performed to obtain the samples with different surface micro groove sizes.The laser joining experiments of single lap structures of surface etched 6061 aluminum alloy and CFRTP were carried out by adopting the optimized laser joining parameters.The effects of surface etched structures on the interface fusion morphology and element distribution of the joint were explored.The temperature field simulation of the laser joining process of surface etched aluminum alloy and CFRTP was performed to study the effects of different micro groove structures on the interface forming of joints.The results show that there is a mechanical interlock between the micro groove structure of the aluminum alloy surface and the filling resin,which increases the bonding area between the resin and the aluminum alloy surface.When the micro groove depth is large,the defects such as bubbles and incomplete fusion are produced in the joint interface easily.Finally,the joint tensile properties of surface etched 6061 aluminum alloy and CFRTP were tested to explore the effects of the etched structure parameters such as the depth,width and distribution density of the micro grooves on the failure load,shear strength and fracture surface morphology of joints.Experimental results indicate that the width of the micro groove is more critical to the shear strength.When the size of the micro groove is 0.3mm in width,0.5mm in depth and 1.5mm in groove spacing,the higher shear strength can be obtained.