Bonding performance after aging of fusion bonded hybrid joints

The investigations of this article are showing the bonding performance after aging of hybrid fusion bonds in combination with a laser pre-treatment. The investigated materials are a galvanized steel (HX340 LAD Z100MB) and two glass fiber reinforced Polyamide 6 materials. In order to achieve a structural strength of the fusion bond a laser pre-treatment is used. The investigation is focusing on the changes from the laser pre-treatment to the galvanized surface by analyzing the steel surface with a scanning electron microscope, energy disperse X-ray spectroscopy, micro sections and surface roughness measurements. The composition of the applied thermoplastic materials is not in the focus of the article which is why different manufacturers for the fiber reinforced thermoplastic material have been chosen. The aging of the samples is done by a climate change (PV1200) and a salt spray (PV1210) test in order to evaluate different aging mechanisms. Furthermore the investigation is providing a crucial finding by showing the impact of a batch change on the achievable lap-shear strength by comparing two batches from the same manufacturer. The results of the laser surface pre-treatment show that the zinc coating of the steel adherend is reduced significantly and does not provide a closed coating. The climate change test after 100 cycles showed no decrease of lap-shear strength compared to the reference when the highest investigated pre-treatment intensity is applied to the surface. The salt spray test showed a corrosion of the pre-treated area for laser pre-treatment settings which generate a low amount of oxygen on the surface. The pre-treatment settings generating a more oxidized surface (medium and high intensity) showed only a minor influence on the achievable lap-shear strength after 90 cycles.