Melioration of the Tensile Shearing Strength Test Method for Polypropylene Joined Using Laser Transmission Welding (LTW)
Y-T. Cheng, Y-E. Wang, Z. Liu, Y-M. Wang and Y-J. Cao
In this paper an improved tensile-shearing test method for plastic of laser transmission welding (LTW) was proposed. Comparing with traditional single-lap welding test method, which needs two sheets lap and single welding seam, the improved double-lap welding test method is characterized by four symmetrical sheets lap with four welding seams. Transparent polypropylene and opaque polypropylene were joined together by two inter-comparable methods, single-lap joint and double-lap joint, respectively. The tensile-shearing strength of the resultant samples was examined respectively. The results show that, no deflection distortions are observed in the welding seam of double-lap specimens due to the absence of additional bending moments. And the contrast single-lap joint specimens display a certain deflection distortion angle, which is caused by additional bending moments in the tensile-shearing test process. The resultant testing values of shearing strength of double-lap joint specimens are generally higher than single-lap joint samples even at the same energy density level, due to the replacement of un-synchronous fracture of single-lap joint seam by synchronous fracture of double-lap joint seam.
Keywords: High power diode laser (HPDL), Laser transmission welding (LTW), polypropylene, double-lap joint, tensile shearing strength