Friction press joining is an innovative joining process for the production of plastic-metal joints without additives, in an overlap configuration. In order to achieve a high bond strength, the metallic joining partner is pretreated with laser radiation. Subsequently, heat is induced by friction and pressure during the joining process, causing the thermoplastic material to melt and adhere to the metallic joining partner. In this work, the temperature distribution during the process in the composite is analyzed and characterized. It was found that the occurring temperatures and temperature differences are not only dependent on the rotational speed, but also on the feed rate. It is also shown that the friction surface temperature can be used as an indirect control variable for a model-based, closed-loop control. Based on these findings, various surface modifications for the metallic joining partner were investigated and analyzed with regard to the maximum strength of the joint. It was observed that the highest tensile shear strength can be achieved with a quasi-chaotic nano structure. In addition, the joining compound was characterized by a thin section, facilitating the identification of specific zones in the joint. These investigations show the high potential for friction press joining of plastics and metals, and form the basis for a model-based control of the joining zone temperature.
The importance of hybrid composites is increasing, particularly with regard to structural lightweight construction. Therefore, a joining process for the production of hybrid bonds using induction technology is examined in this paper. An appropriate test rig was developed, assembled, commissioned and characterized for this purpose. Heating tests with titanium Ti6Al4V were carried out with this device to determine the influence of the process parameters on the temperature level and the temperature field. This applies in particular to the feed rate, the sample geometry, the relative positioning between sample and inductor as well as to the inductor setting like induction frequency and pulse width modulation. Based on the results of these examinations, a two-stage heating process was developed, which allows the formation of a homogeneous temperature field in the range of the melting and degradation temperature of the used polymer (PPS; Ten-Cate Cetex TC1100) and thus to achieve optimized bond strengths. More specifically, a short phase with a high energy input was used for quick and intensive warming and a longer time period was deployed to reach an even distribution of temperature. Subsequently, joints with CFRP were produced with a specimen geometry suitable for tensile shear tests according to DIN EN 1465 (Adhesives-determination of tensile lap-shear strength of bonded assemblies; German version EN 1465:2009, 2009). The analysis of the tensile shear strength and the fractured surfaces shows that the metal is much more difficult to heat up due to the melting enthalpy of the plastic than preliminary tests indicated. Further tests were carried out, which revealed a threshold value for heating where the temperature was sufficiently high to achieve a complete coating of the plastic on the metal can be achieved. In summary, the investigations showed that the presented method as well as the design of the test rig is generally suitable for bonding metal to thermoplastic polymers. The influence of various parameters on heating and bond strength could be identified. Moreover a process has been established, which allows industrially useful bonding forces. This not only proves that further investigations are useful, but also laid the foundation for further experiments.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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