Interactions in laser joining of metals to polymers

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The joining of metals and plastics becomes more and more important due to the increasing use of plastics in many industrial sectors and an increased demand for lightweight structures. This trend is reinforced by a development towards miniaturization and functional integration in the electrical industry as well as by the utilization of specific lightweight potentials of materials that are used in the automotive sector. Such compounds are, however, procedurally not easy to realize as the materials have very different physical and mechanical properties. Within this context, flat, firmly bonded compounds are especially difficult to realize.It is the aim of this research project to investigate the adhesion mechanisms and composite properties of firmly bonded, laser beam joined plastic-metal composites that were subjected to physical / chemical surface pre-treatments. The metallic specimens will be directly joined to the plastic specimen by using two different configurations in a lap joint procedure, utilizing direct as well as indirect laser beam joining processes. In a first step, significant influencing factors on the bond strength of thermally joined metal-plastic joints will be determined. The correlation of the process parameters and the obtained bond strengths allows the determination of useful process windows for selected material combinations. For this purpose, the failure behavior of thermal joints is analyzed and evaluated. Subsequently, an examination of the bonding strength and adhesion mechanisms is conducted in relation to the plasma pretreatment /coating. Additionally, the influence of the plasma pretreatment /coating on the aging of the composite is investigated. Furthermore, metal-plastic composites with metallic interlayers will be produced and examined concerning their bond strength and adhesion mechanisms. The influence of the metallic interlayers on the aging of the composite will be investigated as well. In the part that is concerned with modeling, the thermal and thermo-mechanical images of the direct and indirect laser beam joining processes will be used to calculate the local temperature fields as well as the thermally induced stresses. Finally, the process variants with a plasma pretreatment / coating or with metallic interlayers will be compared and evaluated.