Multiscale mechanical modeling of paperboard

Sammanfattning: This thesis considers an investigation into the possibilities of creating a reasonably accurate multiscale material model for paperboard, with geometry based on X-ray scans of small paperboard samples. The modeling takes place in the software Multiscale Designer by Altair Engineering Inc. A representative volume element (RVE) is used to capture the X-ray geometry and represent macroscopic mechanical properties. The RVE consists of fiber and air phases, perfect fiber-fiber bonding assumed, where the fiber phase is assigned transversely isotropic linear elasticity and isotropic hardening plasticity. This model is considered to behave consistently across different tested X-ray geometries. The results show that it is possible to achieve a reasonably good model fit for in-plane uniaxial tensile tests in MD, CD and 45 degree loading directions. Further, the model is also exported as a user material in Abaqus, where simulations are performed to compare the multiscale model with a previously established continuum based model. Although the simulation results do not agree completely, there are some similarities, which is promising for further model development. The multiscale modeling workflow can be automatized to some degree. For this, one needs to ensure the correct content and format of text files used as input in the modeling analyses. The model may be further developed with additional features such as fiber-fiber bonds, and calibrated towards other and more complex load cases.