S. Hirt
V. Wippo
P. Jäschke
S. Kaierle
L. Overmeyer

Laser-based welding for repair of thermoplastic CFRP composites

Proc. International Congress on Applications of Lasers & Electro-Optics (ICALEO)
Type: Zeitschriftenaufsatz (non-reviewed)
Carbon fiber reinforced plastics (CFRP) have become standard in the lightweight industry due to their high strength-to-weight ratio. CFRP with a thermoplastic matrix material is more attractive for many applica-tions as a thermosetting matrix material. That is be-cause it offers new processing possibilities such as welding and thermoforming. Due to the high amount of resources required for the production of CFRP parts in combination with high production costs, there is an interest in repairing components instead of replacing them completely. Currently, the repair process is mostly done manually. In order to reduce repair costs, an automated, reliable, and fast process is needed. Therefore, a repair procedure will be developed at LZH using laser welding. For the new welding-based repair process, first a scarf joint is prepared in a CFRP laminate consisting of a thermoplastic matrix material. After that, a CFRP patch with the same matrix material is laser welded into the prepared area. For the joining process, heat conduction welding is applied. In this process, the la-ser radiation is absorbed on the top of the material and transferred into heat, which reaches the lower part by heat conduction. For the welding process a diode laser with a maximum power of PL = 300 W and a wave-length of λ = 940 nm was utilized. A homogenizer op-tic was installed to generate a tophat intensity distribu-tion with a laser beam geometry of A = 11 x 43 mm². In order to develop a welding process for obtaining a high joining quality, the laser power, welding time, and clamping pressure were varied. For the analysis of the joining quality, overlap samples were welded and tested in order to determine the tensile force. In addi-tion, cross sections were prepared and analysed with a microscope. Finally, the measured results will be com-pared to find out which parameter set generates a great weld seam.