Additively Manufactured Sandwich Structures with Surface-Based Lattice Cores: Analysis, Simulation and Test

• Applicant: Professor Dr.-Ing. Christian Mittelstedt
• Subject Area: Lightweight Construction, Textile Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 535913617

This project deals with analysis, simulation and testing of additively manufactured sandwich structures made of AlSi10Mg under mechanical load, where the core consists of surface-based lattices. In the case of the surface-based lattice sandwich cores to be considered, effects will become apparent which are not known from isotropic structures and which must be taken into account in the modeling and analysis. In particular, transverse shear strains and the coupling effects caused by functionally graded cores must be mentioned here, which requires the use of a higher-order sandwich theory. This newly developed theory will be implemented and prepared in such a way that it can be directly used by engineers in practice. The state of research shows that while a significant number of publications are available discussing higher-order sandwich theories, the number of studies using strut-based lattice cores is surprisingly small in comparison, the more so for surface-based lattices, so there is a significant need for research in this area. It can be expected that modeling within the framework of a higher-order sandwich theory will show orders of magnitude lower computation times than comparable simulations with commercial FEM software systems, which justifies a detailed consideration. In addition to static analysis, the buckling behaviour must also be considered. A review of the literature shows that, in particular with regard to phenomena such as plate buckling, but also with regard to the buckling of the face sheets in the presence of surface-based lattice cores, there is no knowledge available, so that there is also a very clear need for research in this area. In addition to simple cases such as buckling of plate strips, which can be derived easily from the developed sandwich theory, attention must be paid to plate buckling for different types of boundary conditions and load cases. It is foreseeable that analytical solutions are possible here only for very elementary types of boundary conditions, so that one must resort instead to energy-based approximation methods with suitable series expansions for the state variables. It is particularly important to also deal in detail with the buckling of the face sheets, which can be addressed, for example, in terms of modeling a plate on an elastic foundation, and to make it accessible to analysis. The theoretical findings of this project are to be validated by adequate tests. For this end, the experimental setup needs to be defined, and an experimental programme needs to be developed. Specimens will be manufactured on the additive manufacturing system available at the institute of the applicant, and static tests on core specimens as well as on sandwich specimens will be performed.

• DFG Programme: Research Grants