Wrinkling in packaging material: Experiments and thermo-mechanical stochastic modeling

Sammanfattning: As one of the world leaders in food packaging, it is in the interest of Tetra Pak⃝R to increase the understanding of packaging material and how it can better be virtually modeled, using finite element (FE) simulations. The aim of this thesis is to evaluate whether a stochastic approach can be taken to generate a more realistic response than a purely deterministic one, in the aforementioned models. To accomplish this, a load case involving the exposure of packaging material to excessive heating is investigated, physically as well as virtually. The physical experiments consist of thermally loading small samples of packaging material with the in-plane dimensions 3 mm × 25 mm using a heat gun and analyz- ing the results, both by ocular inspection and by using X-ray computed tomography. The virtual experiments consist of pre-processing in the computer software Hyper- Mesh, using Abaqus as an FE-solver and HyperView and Abaqus as post-processors, to replicate the results, by implementing a realistic paperboard surface topography. The conclusion from the virtual results is that the chosen stochastic approach in this thesis can be used to capture microstructural phenomena, such as the buckling of the thin thermally expanded aluminum foil of the packaging material. The different virtual experiments do, however, not always match the physical ones, and may need further improvement. Future works could include a more systematic and controlled environment for the experiments, i.e. a testing rig with greater repeatability and with the possibility of easily varying the parameters of the system.