PSI - Issue 28

Shayan Eslami et al. / Procedia Structural Integrity 28 (2020) 659–666 Shayan Eslami/ Structural Integrity Procedia 00 (2019) 000–000

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(b)

Figure 2- a) welding temperature evaluation of using PEEK stationary shoulder tool, and b) effect of different welding parameters and their contributions on the weld strength.

A newly developed welding tool made of H13 steel (Figure 3a) was tested to analyze how thermoplastic composites behave using this tool concept. This tool designed in a way to benefit from both welding tool concepts, rotary shoulder and stationary shoulder. As illustrated in Figure 3a, a rotary shoulder was located inside the copper sleeve attached to the stationary shoulder to generate frictional heat on the surface of the base material, while probe is string the plasticized materials. Then, the stationary shoulder forges the plasticized materials inside the weld seam to avoid formation of flash defects presented by conventional welding tool. Due to the size of the H13 welding tool and capacity of the available machine, it takes time just for the tool to heat up to the desired temperature during the dwelling stage. However, when the desired temperature was reached, the welding temperature is much more stable in compared to the PEEK tool. The welds produced using this tool had rough surface quality (Figure 3b) when compared to the PEEK stationary shoulder, which this issue can be solved by ceramic coating of the bottom surface of the shoulder, creating smooth surface quality. This tool demands more torque as the contact area between the tool stand and copper sleeve were increased significantly in order to compensate lack of the generated heat. For this reason, the welding parameters range that could be tested was very narrow as the spindle was unable to apply enough torque. However, after some trials the maximum tensile strength of 58.8% was achieved, which was a significant improvement from the previous tool design. This joint efficiency was obtained without any parameter optimization, as it can be noticed from the Figure 3b that the produced weld suffers from inadequate probe penetration and good surface quality.