Ageing Behavior of Thermally Joined Hybrids of Laser Pre-treated Metal and Thermoplastic Polymers

摘要

Cost-efficient, load bearing and chemically resistant hybrid joints are necessary for future applications within the automotive industry. Thermal joining can be applied to create a direct connection between thermoplastic polymers and metal components and is thus seen as a promising prospect. Yet, the ageing resistance and seal tightness of joints remains uncertain. Within this work, a pulsed laser system (λ=1064 nm, f=20 kHz) is used to create microscopic random structures on aluminum and copper surfaces. The surface topology is analyzed using optical focus variation. The metal is then connected to different thermoplastic polymers. Polymers are selected with a particular focus on chemical resistance to electrolytes used in modern automotive battery systems. Shear strength and seal tightness for helium gas are measured before and after exposing the joints to humidity and heat. The cause of failure is investigated using REM- and EDX-analysis and by comparing observations from different ageing tests. It is demonstrated that thermoplastic elastomers, such as TPC and TPU, enable long-term resistant hybrid joints (6 N/mm~2), with no tendency of a decreasing shear strength.