Mechanical performance of single lap polymeric joints welded by a portable diode laser

Abstract

The polymer laser welding can be successfully used to join two or more parts of plastic surfaces and it can be used in several fields, such as the biomaterials and microelectronics. Thermoplastic materials are welded by a localized energy input without the use of any organic solvents and formation of particulate.The employment of a portable diode laser can personalize the welding joint area and it let to draw the welding geometry, like a pen in a very easy and fast process. In this research, we studied single lap joints made by biomedical grade polyethylene (UHMWPE) pure and filled with carbon nanomaterials, necessary to make the polymer laser absorbent, added in amount of 0,2% in weight.The joints were irradiated by a diode laser operating at 970 nm (fundamental harmonic), in repetition rate of 10Hz, with a maximum pulse energy of 200 mJ and a laser spot of . 4 mm2 (no focusing lens were employed). The portable laser was employed to realize four types of welding geometries (points, continuous and discontinuous lines, cross lines) in the overlapped area. The joints were characterized by mechanical shear tests and hardness Shore D test and observed by a morphological analysis (optical microscopy). The results suggested that the welding strength depends not only on the welded area, but also on the continuity of the welded geometry and on the stress direction. The points welding exhibits the worse mechanical performance, while is the cross lines welding the best one among these investigated.