On the out-of-plane mechanical behaviour of paper materials

Abstract: This thesis deals with the through-thickness mechanicalbehaviour of paper materials. The material response undercombined normal and shear through-thickness loadings isfundamental for analysis and understanding of many end-use andconverting operations, such as folding, creasing, printing,calandering and cutting. Therefore, this thesis addressesissues of importance in product development within thepackaging and printing industries.The objective of the thesis is to develop a constitutivemodel for paper that, in combination with appropriate in-planemodels, enables three-dimensional structural analysis using forexample the finite element method.Constitutive modelling requires data from carefully executedexperiments. This types of data for the through-thicknessproperties of paper are not generally available in theliterature, and therefore a novel device for through-thicknesstesting of paper materials is developed. The experimentalinvestigation includes through-thickness tension andcompression testing, shear testing and testing under differentcombinations of normal and shear loadings. Furthermore, theout-of-plane Poisson’s ratios are examined.An elastic-plastic constitutive model for combined normaland shear through-thickness loadings is developed. To capturethe experimental observations, a model based on nonlinearelasticity and bounding surface plasticity is proposed.Keywords:Paper, Paperboard, Biaxial, Tension,Compression, Shear, Z-direction, Out-of-plane, Poisson’sratio, Testing, Model, Bounding surface, Yield surface,Elastic, Plastic