Investigation of sample-size effects on in-plane tensile testing of paperboard

Abstract The impact of sample size on in-plane strain behavior in paperboard was investigated, with the aim to explore the differences between local and global properties in paperboard, and try to pinpoint the mechanisms behind such differences. The local properties are of interest in converting as well as for future 3D forming of paperboard. It is important to identify differences in behavior between local and global properties since most paperboards are evaluated against the latter. The methods used for evaluation were tensile tests in controlled environment and speckle photography. The results show that there is a difference in strain behavior that is dependent of the length to width ratio of the sample, that this behavior cannot be predicted by standard tensile tests and that it depends on the board composition. The speckle analysis revealed that the behavior is a result of the activation of strain zones in the sample. These zones are relatively constant in size and therefore contribute differently to total strain in samples of different size.