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Properties of Single- and Double-Lap Polymeric Joints Welded by a Diode Laser

Single-lap and double-lap polymeric joints of ultrahigh molecular weight polyethylene (UHMWPE) sheets, opportunely overlapped, were realized and studied. One of the polymer sheets was doped with carbon nanomaterials as a laser-absorbent filler. The joints were irradiated by a diode laser operating at 970 nm with maximum pulse energy of 200 mJ. Four types of weld seam geometries were realized in the overlapped area. Optical microscopy observations and mechanical shear and hardness tests were performed in order to characterize all the prepared joints. The maximum shear load was ≈210 N, reached generally in the double-lap joints. High loads in the single-lap joints were reached if high surface area of the welding and high filler amount in the polymer were present. Three parameters influenced the joint resistance: the joint configuration (single or double lap), the welding geometry, and the filler amount. The absorption of diode laser energy at the sheet interface induces a melting process that softens the polymeric sheets in the laser contact area. Finally, a comparison between the welding ability of the diode laser and of the Nd:Yag laser upon the polyethylene sheets is presented.