CLEAN JOINING TECHNOLOGIES FOR FUTURE MULTI-MATERIAL DESIGNED PARTS USING PULSED LASER

Change from metallic materials to fiber-reinforced plastics (FRP) is progressing steadily, for its resource saving capacities. Along goes the adaption of production processes. One approach to produce high loadable lightweight structures is the FuPro-Design. Hollow thermoplastic composites (TPC) profiles are combined with TPC sheets, metallic parts and functionalized using the injection molding process. However, there is a R&D need in combining the diverse requirements of complex components in an environmentally compatible way. The Multi Material Design for Recycling (MM4R) project aims at the eco-balance: reducing variety of materials, improving separability and avoiding contamination. Besides the weight reduction compared to aluminum, the objective is the avoidance of additional adhesive promoter materials. Here, the pulsed laser technology is the chosen approach. This work offers insight into the possibilities of pulsed laser processing of compound lightweight materials. Selective processing of the temperature-sensitive FRP becomes possible since non-contact processing prevents any mechanical stress and thermal damage can be prohibited. The joining mechanism bases on a surface structuring resp. the exposure of the fiber reinforcement on the surface of the composite with the effect of achieving high joining strength when the structure is further processed. With no adhesion promoters, laser processing is a clean technology for surface pretreatment for joining processes like injection molding/over molding, 3D printing, bonding or metallization. The presented studies show the advantages of the laser technology in two applications. TPC sheets were pretreated using laser radiation in order to improve the pull-off strength of over-moulded rib-parts. Laser pre-treatment could significantly improve the bonding strength of over molded solid TPC-sheets, showing an improvement of 713 % compared to the untreated samples and 128 % compared to hot over molding. Secondly, the laser pre-treatment was performed before hot pressing TPC and FRP sheet, which were evaluated in single-lab sheer tests.