EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In search of lower emissions in the transportation sector, the focus shifts to alternative energy storage systems. By switching from fossil fuels with a high gravimetric and volumetric energy density and easy storability to battery systems or hydrogen tanks, a new demand for lightweight and multifunctional designs arises. Fiber reinforced materials help to fulfill these requirements, due to low restrictions on shape and a high specific strength. Load bearing structurally integrated battery casings or hydrogen tanks could benefit from composite materials. In both applications, feedthroughs are necessary either for sensors and cables or for operating fluids. In case of hydrogen tanks, it is obvious that a leak proof design is mandatory. However, for battery casings it is also essential to keep water or any kind of pollution away from sensitive equipment. However, the usefulness of metallic feedthroughs in composite structures offers the best compatibility to piping and wiring demands. Therefore, a hybrid solution of a composite tank or casing in combination with a metallic insert is needed.
The aim of the presented research is the formulation of general design guidelines for metallic feedthroughs fully integrated in fiber-reinforced laminates. Typical solutions to achieve a leak proof feedthrough make use of sealings, threaded fittings or bonding. From injection molded electrical housings the concept of in-mold integration of the feedthrough in the final part is common practice. This is also true for load introduction points in continuous fiber reinforced thermoset laminates. However, the mechanisms for optimal load transfer are different to those leading to leakage at the metallic interface. A newly developed testing procedure is presented as well as the findings for different insert alloys, reinforcement types and measures to enhance the durability with respect to media tightness.