No abstract

Mixed-Materials parts have great light-weight potential for the automotive application to reduce the carbon footprint. But the joining of fibre composite plastic sheets to metal sheets is in practical application limited to adhesive bonding or mechanical joining with additional fastener elements due to the large differences in physical properties. A new process chain based on plastic joining without fastener elements is proposed and first results on the mechanism and on the achievable strength of the new joints are shown. The process chain consists of three steps: First joining pins are added to the sheet metal by an additive manufacturing process. In a second step these pins are pierced through the fibre composite sheet with a local heating of the thermoplastic in an overlap setup. In the third and last step the joint is created by forming the pins with the upsetting process to create a shape lock. The shear strength of the joined specimens was tested in a tensile testing machine. The paper shows that even with a non-optimized initial setup joints can be realised and that the new process chain is a possible alternative to adhesive bonding.

Abstract A new hybrid process for fiber-reinforced plastics based on thermosets combining master-forming and forming in one tool is currently undergoing development. The advantage of this technique is the integrated forming and overmolding of a thermoset-based continuous fiber-reinforced sheet in one step. Although both components are epoxy based, the resin formulations slightly differ and thus require individual curing parameters. For successful combination into one process, it is essential to investigate both components in relation to the processing parameters and their influence on the degree of cure. Besides the influence on the forming and filling behavior, the degree of cure also has an effect on the resulting mechanical properties. In this investigation, the influence of curing time and temperature on the degree of cure of epoxy-based materials was investigated with regard to identifying a process window for a process combination of master-forming and forming.

Thermoplastic matrix composites enable production in short cycle times suitable for high volume production of lightweight design parts. While heating fully consolidated semi-finished products (“organo-sheets”) internal stresses from their production emerge, thus causing voids. Such de-consolidation must be undone or obviated for void-free parts. In this article the influence of moisture and the laminate setup on the de-consolidation behavior of twill-weave PA6/GF laminates is investigated. The results show that moisture leads to a higher void content during de-consolidation. The laminate setup in terms of fiber-volume content preponderances the influence of moisture on the de-consolidation.