Long-term strength of direct screw connections in thermosetting moulding compounds

Systematic investigation of the connection properties

Thermosets are materials that, unlike thermoplastics, cannot be joined by welding. Therefore, bolting, especially direct bolting, is a promising option for realising an economical and detachable connection of thermoset components. At IKV, the joining properties of direct bolting are being systematically investigated in order to be able to create and establish guidelines for the design of direct bolting of thermosets on this basis.

The connection properties of the direct screw connection have already been investigated under short-term load in a previous project. The project “Practice-relevant investigations into the long-term strength of direct screw connections in injection-moulded thermoset moulding compounds” (thermoset direct screw connection II), which was launched at the beginning of 2025, builds on these investigations and focuses on the long-term strength of the direct screw connection under dynamic load.

© IKV

The influence of both a static and a dynamic temperature load during the mechanical stressing of the direct screw connection is also to be analyzed. Furthermore, a numerical parameter study of the screw dome geometry is carried out using numerical simulations. The data from the short-term and long-term studies will be compared at the end of the project in order to derive mitigation factors. In this way, based on the short-term strength, conclusions can be drawn about the long-term strength of the direct screwing of thermoset components. Finally, the test results are used to derive general production and application recommendations for the direct screwing of thermosetting moulding compounds.

Funding and project data

We would like to thank the BMWK for funding the IGF project (funding code 23254 N) and the project partners for their cooperation.

Project duration: 1.5.2024 to 30.04.2026