Cyclic-dynamic properties of particle foams (continuation application)

• Applicants: Professor Dr.-Ing. Maik Gude; Professor Dr.-Ing. Holger Ruckdäschel
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Materials in Sintering Processes and Generative Manufacturing Processes ; Mechanical Properties of Metallic Materials and their Microstructural Origins ; Polymer Materials
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437872031

Particle foams are characterized by a unique combination of low density, high mechanical energy absorption under load, great design freedom and low manufacturing costs. They are therefore predestined for a wide range of applications, which currently include sports shoes and safety-relevant vehicle interior components. By selecting the processing parameters during foaming, the properties of the cell structure and thus the behavior of the molded parts can be adapted to the respective application. According to the current state of research, however, there are significant uncertainties regarding the structure-property relationships of particle foams. Although simulation methods are available that are suitable for predicting the macroscopic material behavior under any multiaxial load conditions, they are based on substantial simplifications, such as the neglect of local stress and distortion maxima on the micro and meso scale of the foam. For example, global compressive loading within the cell structure results in local bending, buckling or tensile failure. The mechanical behavior is also significantly influenced by the enclosed cell gas and its compression. If the molded parts are subjected to oscillating loads over a longer period of time, empirical findings show that the molded part undergoes cyclical creep. Both the interaction between cell gas and cell structure and the phenomenology of cyclic creep have not yet been sufficiently clarified. The focus of the project is the experimental and numerical investigation of the mechanical behavior of particle foams under multiaxial cyclic loading. With the help of a test methodology to be developed in the project for carrying out ambient pressure-dependent multiaxial tests and the application of X-ray tomographic analyses, the interactions between cell gas, cell structure and base polymer on the one hand and the time-dependent mechanical properties of the particle foam on the other are to be analyzed. The focus is on determining the relationship between the mesostructural parameters and the multiaxial properties of the particle foam. In order to reduce the effort required to analyze the complex structural descriptors, ML-based image analysis methods are to be developed that allow the gusset volumes and particle wall thicknesses to be determined efficiently. The mechanical tests are aimed at determining the multiaxial viscoelastic properties including the transverse contraction number as well as investigating the influence of the cell gas on the deformation and failure behavior in the case of large multiaxial deformations. Finally, a modeling and simulation methodology is developed to describe the mechanical behavior of rate-dependent multiaxial loading and unloading.

• DFG Programme: Research Grants