The overmoulding process for thermoplastic fibre composites combines the excellent mechanical properties of continuous fibre reinforced laminates with the high degrees of geometric freedom and short process times of injection moulding. Continuous fibre composites can be stiffened or functionalized by overmoulding with a short fibre reinforced thermoplastic. The compound strength of these hybrid structures, is determined primarily by the interface between the continuous fibre-reinforced insert and the injection moulding compound.

The use of this technology for highly stressed components or safety-critical parts is currently prevented mainly by an incomplete understanding of the process and resulting properties, as well as a lack of process and quality assurance.

The formation of the interface is influenced by a multitude of process parameters. As a result of these parameters, certain process variables occur in the mould cavity during the filling process, which are decisive for the bond forming between insert and injection moulding compound as well as the resulting component properties and should therefore be used for monitoring the process.

For this purpose an overmoulding tool with an array of sensors within the cavity was developed. This tool allows the fabrication of test specimen, with which the bonding properties at the interface can be determined as a function of the process variables. By using 8 individual sensors, the temperatures of mould, insert and melt can be measured. All sensors were provided by the FOS Messtechnik GmbH as part of a cooperation in the research project QuaSimOdo.

A statistical test plan was carried out to evaluate the tool and the sensor system. The effects of various machine and process parameters on the process variables measured in the cavity and the resulting bonding properties were determined for a material system of PP-GF inserts and compound.