3D printing for maximum stability: design and post-processing as key factors

Kerstin Weinberg’s working group at the Chair of Solid Mechanics at the University of Siegen is investigating the innovative use of sponge rubber in high-tech products. Sponge rubber, an elastic foam with high compressive resilience and a smooth surface, is used in seals and housings. The university uses the inspekt duo universal testing machine from Hegewald & Peschke to test the material properties.

Sponge rubber, a mixed-cell rubber material, is used in various industries for seals, thermal insulation and soundproofing. The computer-aided development of these systems has increased the demands on the damping properties. In Prof. Weinberg’s new research project, the influence of the microstructure on the dynamic material behavior of elastomer foams is being investigated. The mechanical properties of a foamed elastomer depend heavily on the microstructure and the matrix material. With increasing porosity, the influence of the microstructure on the deformation behavior increases.

Experimental tests on industrial elastomers and additively manufactured foam structures help to determine material and structural parameters and to simulate the material behavior with computer support. Simple, practical material models are required for the simulations, which are widely used in medium-sized companies in the digitalized component design process. There is currently a lack of such models for sponge rubber in the industry. Two new modeling approaches are therefore being developed as part of the project. Finally, real component simulations will be carried out with the developed models and tested experimentally.

An inspekt duo 5 kN universal testing machine is used at the chair to test the foams. Compression tests and creep tests are carried out at room temperature. The latter are used to determine the creep behavior under constant load, whereby the strain is measured over the travel distance. The high resolution of the testing machine’s crosshead travel measurement system (<0.025 µm) ensures precise strain measurement.

In addition, relaxation tests are carried out in which the decrease in stress is measured at constant deformation. The LabMaster testing software makes it easy and convenient to carry out and evaluate these tests. It offers all the functions required to clearly organize creep and relaxation tests and enables reduced data acquisition in certain test phases.

The research project is being funded by the Federal Ministry for Economic Affairs and Climate Protection with 400,000 euros as part of the Industrial Collective Research (IGF). In addition to the scientists from Siegen, the German Institute for Rubber Technology (DIK) in Hanover is also involved. A special feature of the IGF projects is the involvement of small and medium-sized enterprises (SMEs), which facilitates their access to practice-oriented research and strengthens their competitiveness.