Pulsed laser welding of metal-polymer sandwich materials using pulse shaping

Increasing interest has been expressed in the application of hybrid metal/polymer materials for automotive applications, both to reduce weight and to improve performance. To date, the only joining methods available are mechanical fastening and adhesive bonding, both requiring an overlapping joint configuration to generate sufficient bond strength. This article describes how laser spot-welding and SHADOW™ (stepless high speed accurate and discrete one pulse welding) welding can be used to minimize degradation of the polymer while making fusion welds in the metal layers. The thickness of the external layers in metal polymer laminates is approximately $0.25 mm$⁠. Laser spot welds on such thin materials are very susceptible to cracking due to high cooling rates causing large stresses. These high cooling rates are necessary to avoid excessive thermal degradation of the central polymer layer. This article addresses a technique to provide such high cooling rates while preventing cracking in AA5182 thin sheet during pulsed laser welding.