Additively manufactured foam sandwich structures – a novel approach for the generative processing and characterization of foam based, three-dimensional graded materials for lightweight design

• Applicant: Dr.-Ing. Wilfried Liebig, since 11/2022
• Subject Area: Plastics Engineering
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 406069344

Aim of the project is the development of a manufacturing process for three-dimensional printed and foamed sandwich components. This process shall allow a manufacturing – similar integrated like foam injection moulded composites - of such components and at the same time facilitate the investigation of the relationship between processing, microstructure and properties of these composites. A manufacturing process for such components, which has not been realized so far, and which shall be implemented in the course of this project, is based on the Arburg Kunststoff Freiformen (AKF) technology. In contrast to conventional additive manufacturing processes - e.g. printing of filaments - standard granulates as used in injection moulding processes, are melted. If a foaming agent is added to the granulate a direct printing of foamed “droplets” can be achieved. The degree of foaming can thereby controlled through the process parameters. The additive manufacturing using two components (foamed/dense) allows for an additive manufacturing of sandwich structures which can be foamed and graded. Hence, it offers a high degree of design flexibility in context to transferability of two-dimensional structures to three-dimensional structural components. Hereby, layer thickness or gradation respectively, can be tailored in the required way and an optimum adaptation of cross-section geometry towards loading conditions of the component can be achieved. Further advantages can be found in high surface quality of the components, shrinking compensation due to the foaming and the possibility of integration of functional elements. In the planed project, this manufacturing route has to be developed based on preliminary work of the applicants. Therefore, suitable material systems shall be selected and adapted to foam printing. Subsequently, suitable process parameters will be determined and the manufactured samples will be characterized. Three-dimensional microstructural analyses will essentially be done by micro- computer tomography (µ-CT). Particularly, size and distribution of pores in the foam core and thickness of the sandwich components are in the focus of these investigations. The structural values shall then be correlated to the mechanical properties determined in subsequent material testing. This includes investigation of the sandwich behavior under component near loading conditions, like e.g. quasi static loading, impact loading, as well as of failure behavior under these various loading conditions. The basic correlations will be initially determined on two-dimensional structures and will then be transferred to more complex three-dimensional structures, when a sufficient process- and material understanding is achieved.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Kay A. Weidenmann
• Ehemaliger Antragsteller: Professor Dr.-Ing. Peter Elsner, until 11/2022 (†)