Hybrid compounds made of metal and fiber reinforced plastics, e.g. carbon-based, are used today across all industries. That is why innovative joining processes are being researched to produce hybrid structures that contribute significantly to resource efficiency in various sectors such as the automotive and aircraft industries by reducing weight. For such innovative multi-material designs the assembling of the different materials is critical because for each of the different material combinations a specially adapted and efficient joining technology is required. For state-of-the-art joining technologies, such as mechanical joining by screws or rivets and adhesive bonding, specific restrictions can be found with the use of additional material, limitations in the geometric flexibility or comparable long bonding times. For mobile applications, the long-term resistance of hybrid multi-material systems such as those made of metal and CFRP is a decisive criterion for ruling out premature failure under operating conditions.
Prior to joining, different surface topographies with a characteristic aspect ratio range of 0.1 to 2.0 were created on the aluminum by using a short pulse near-IR-beam laser. The surface conditions achieved were characterized by optical as well as chemical methods and correlated with the mechanical properties of the single-lap joints produced. The results indicate that by usage of a specific range of N-IR-laser parameters the shear strength under tensile load can be increased up to a maximum value corresponding to the interlaminar shear strength value of the starting CFR-PA12. This means that the composite failure no longer takes place in the interface between the materials but in the CFR-PA12. In addition, the hybrid compounds produced in this way were exposed to different artificial ageing regimes such as temperature conditioning at T = 40 °C and r.H. > 95 %. It can be shown that high strength in the initial state of approx. 14 MPa can be maintained over a long period of up to 1,500 h. A critical influence is shown during the neutral salt spray test according to DIN EN ISO 9227, which leads to a decrease of the bond strength depending on the structuring. To summarize, it has been shown that the manufacturing of hybrid compounds using IR emitters leads to compounds that have a strength that corresponds to the material strength of the CFR-PA12 used. Secondly, these hybrid compounds have shown different strength degradation under varying climatic and corrosive stress.