Advancing Hybrid Component Manufacturing: The Role of Pultrusion and Weldability in Fiber-Plastic Composites with Metal Joints

The utilisation of a hybrid lightweight design based on fibre-reinforced plastics (FRP) represents a promising methodology for addressing the increasing demands placed on components. Nevertheless, this field is confronted with significant challenges, particularly regarding the economic production of the materials and the development of efficient joining techniques.
This lecture is devoted to an investigation of innovative hybrid designs comprising fibre-plastic composites in conjunction with metallic components. The hybrid components are manufactured using the pultrusion process, which enables efficient production. A salient feature of the hybrid components developed at the Fraunhofer IWU is the design of the metal component as a protruding joining tongue. This is intended to facilitate the utilisation of welding processes. The primary objective is to render conventional welding techniques, such as arc welding, applicable, thereby markedly facilitating their deployment in novel applications. To guarantee the functionality and durability of the hybrid composite, it is essential to ensure a high level of adhesion between the FRP and metal components. A novel hybrid technology, based on special textile and welding techniques, was used for this purpose. Furthermore, an innovative die concept was developed for the manufacture of hybrid components using the pultrusion process. In essence, this is a self-sealing die concept with adjustable clamping forces, which serve to guarantee a bare metal profile that protrudes from the FRP base structure. This is intended to ensure that subsequent joining can be carried out without the necessity for time-consuming reworking (e.g. no uncovering of the metal profile). The functionality of the die system was validated for a range of materials and process parameters. Tensile tests were conducted to assess the bond strength of the developed hybrid components, while welding tests were performed to evaluate the weldability. Additionally, tensile tests were performed on welded samples to validate the residual strength.