Abstract
Laser welding experiments involving amorphous thermoplastic polymer (PMMA) and 304 austenitic stainless steel plates were conducted to explore the influence of laser welding process parameters on plastic–metal joints. A high-speed camera was applied to record the dynamics of the molten pool and the formation of bubbles to reveal the bonding mechanisms of the hybrid joints. The influence of process parameters on the joints was analyzed using temperature measurements performed with thermocouples. The microstructure morphology of joints was observed using SEM. The mechanical characterization of the hybrid joints was carried out to understand the effect of the welding conditions on the weld morphology, flaws and shear stress. Different interface temperatures resulted in two types of bubbles and led to different weld morphology characteristics. A stable hybrid joint with the best shear stress was produced with a laser line energy of 20.16 J/mm2, a temperature of 305 °C and small bubbles. The shear stress of the effective joint under the maximum mechanical resistance was 4.17 MPa. The chemical bonds (M-O, M-C) and mechanical anchoring that formed on the steel’s surface contributed to the joint bonding. Range analysis provided guidance for identifying the impact of individual factors in the shear stress for the laser welding of plastic–metal.
Highlights
Recent developments regarding the connection of dissimilar materials, especially in the aerospace, automotive and medical industries, have drawn attention from various areas [1]
It must be noted that the temperature measured during the resulting direct welding process was lower than measured in the performed tests
Bubbles were formed near the boundary layer and adhered to the 304 austenitic stainless steel surfaces since, in the pyrolysis process, gaseous products could not escape from the molten layer
Summary
Recent developments regarding the connection of dissimilar materials, especially in the aerospace, automotive and medical industries, have drawn attention from various areas [1]. PMMA (polymethyl methacrylate) is an amorphous thermoplastic polymer with a light transmission of 92%; it has seen rapid growth in the number of applications in agriculture, aviation, construction, optical instruments and lighting decoration due to its excellent transparency, better formability than thermosetting resins, recyclability, good machinability and low cost [3] Metals, such as 304 austenitic stainless steel, which have good formability, a combination of low yield strength with high elongation, excellent corrosion resistance and good weldability, are commonly used in manufacturing [4]. Friction stir welding relies on a more rigid stirring head and produces defects, such as holes [13] These joining methods have many inherent drawbacks. The heat input of laser welding can be controlled and applied to a variety of joint forms [14]
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