System improvement for laser-based tape placement to directly manufacture metal / thermoplastic composite parts

The possibility to manufacture economic efficiently structural functionalized parts using high-volume suited processes is crucial to implement lightweight strategies and fulfil the economic and ecologic needs for responsible use of energy and resources. One key strategy to overcome current obstacles of long cycle times and high material costs is to combine metal and thermoplastic composites within one part. Thus, the advantage of having the right material in the right place to fulfil all requirements to the part is used. However, applied solutions to manufacture these kind of multi-material structures still lack in terms of flexibility, productivity, quality and ideal material utilization. One solution for overcoming these current obstacles is the application of the selective diode laser-based tape placement process to locally reinforce metallic parts aiming to generate an optimum weight, reinforcement and cost profile within the part. Key requirement to establish in-situ a sufficient joint between a textured metallic surface and the applied thermoplastic composite tape is the generation of a sufficient heat distribution in both joining partners. Achieving these required conditions becomes even more challenging as both joining partners have completely different thermo-physical and optical properties. Especially, the latter leads to difficulties when using conventional diode laser-based tape placement systems to consolidate tape locally on metal parts, as a local heat input into the metallic component cannot be sufficiently achieved by the diode laser system of these placement units. The present work deals with initial trials to locally reinforce textured metal surfaces using conventional diode laser-based tape placement. Based on these findings the work derives the concept for a novel laser-based tape placement system which considers the use of Philips VCSEL (Vertical cavity surface emitting laser) technology.