In cooperation with partners from science and industry, inpro researchers have developed a vehicle side door in the FOREL project SamPa, which demonstrates the diverse application possibilities of particle foams in a composite system. A new process chain for the combined processing of plastics in particle foaming and injection moulding was developed and implemented.

The aim of the joining research project SamPa was to demonstrate the great application potential of particle foams in the automotive industry, resulting from their good thermal properties and high energy absorption capacity, among other things. A comprehensive knowledge of the process-structure-property-relationships is necessary especially to meet the high requirements in automotive engineering. In order to investigate this, the project partners devoted themselves to various research focal points from material characterization, continuous process and structure simulation, process control, tool construction and quality assurance to material-oriented joining technology.

The developers of the SamPa consortium have characterized expanded polypropylene (EPP) using a variety of analytical methods. For example, the foam cell structure was extensively analyzed using computer tomography and depicted in the structure simulation in the form of representative volume elements. In this way, a unique virtual test method could be developed which allows density-dependent, mechanical material properties to be determined simulatively. In addition, the researchers were able to successfully test a new calculation method that virtually reproduces the mould filling process of particle foaming. In the future, this will make it possible to optimize the positions for filling the cavity and thus the quality of the components and the reproducibility of the process.

Using a total of seven moulds for processing in particle foaming and injection moulding, the toolmakers were able to successfully implement innovative concepts for functionalising particle foams. Among other things, new laser structuring of the mould surface was developed to increase the scratch resistance of the particle foam. In addition, the flat functionalization of the EPP by injection molding was successfully implemented on a door demonstrator in the handle area. In addition to process-adapted temperature control of the injection mold, this requires specially adapted process control in order to achieve a good connection between particle foam and injection molding compound.

To increase process understanding, quality assurance methods were developed and implemented which, among other things, monitor particle transport during mould filling and can detect any process fluctuations at an early stage.

The results of the project are presented in the SamPa technology demonstrator “Vehicle side door” (see picture). This multi-part concept demonstrates the enormous functionality of particle foam. To assemble the components, inserts adapted to the load have been foamed into the foam components. These include plastic inserts for assembly as well as metallic inserts that allow the load to be picked up directly from the handle into the door crossmember according to the material. The latter has been implemented here in the form of a bionically inspired aluminium support structure that can be foamed in, which allows the loads to be transferred to the vehicle body while maximising the lightweight design. In addition, the flexibility with regard to the integration of electronic elements in particle foam structures is demonstrated. The display, Mini-PC, lighting and cables thus find sufficient space in the basic EPP body of the door. The extensive flooding with polyurethane was also successfully implemented in a concept for the outside of the door.

In addition to inpro, the following partners were involved in the joint researach project SamPa: Arburg, Krallmann Pilot-Werkzeug, Michel-Formenbau, Ruch Novaplast, the Laboratorium für Werkstoff- und Fügetechnik (LWF) at the University of Paderborn and the Institut für Leichtbau und Kunststofftechnik (ILK) at the TU Dresden.

This research and development project was funded by the Federal Ministry of Education and Research in the framework concept “Innovations for tomorrow’s production, services and work” (funding code 02P15Z000 – 02P15Z006) and from the Energy and Climate Fund. It was supported by the project management agency Karlsruhe (PTKA).

Further information and the final report of the publicly funded project can be obtained at this year’s FOREL Colloquium on 28^th and 29^th August in Dresden. In addition, the SamPa demonstrator will be presented to a wide audience at the plastics trade fair in Düsseldorf in October 2019.