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UBC Theses and Dissertations

Simulation of the mechanical behaviour of low density paper and an individual inter-fibre bond Targhagh, Majid


The strength of paper is a multi-scale problem. Although paper is a thin product, its strength depends on the characteristics of the microstructure in the thickness direction as well as the orientation of each fiber. Characterizing the effect of these morphological properties of the papermaking fibres on the strength of paper is a vital step in understanding the behaviour of paper handsheets. Numerical simulation methods, such as the Finite Element Method (FEM) enable us to simulate the mechanical behaviour of paper using the actual geometry of the papermaking fibres. In this work, two groups of FE simulations were performed to study the pre-failure behaviour of an individual inter-fibre bond as well as the response of the low density paper geometries, formed based on the Northern Bleached Softwood Kraft (NBSK) fibres, to uni-axial tensile deformation. The simulation geometries were formed based on the actual geometry of the NBSK fibres that were extracted from the µCT scan of the paper handsheets. The results of the simulations were used to study the effect of the morphological properties of NBSK fibres such as length and diameter on the peeling strength of the bond, and the effect of the properties of the geometry, such as basis weight, mixture of hardwood and softwood fibres, and length and thickness of the NBSK fibres, on the tensile index of the geometry. These results showed that the simulation geometries with a higher basis weight and smaller fibre’s elastic modulus lead to a lower tensile index. Further, it is shown that the increase in the softwood content of the hardwood/softwood mixed geometries increased the bulk tensile index of paper. Finally, the results of the tensile strength simulations were compared to the results of the experimental tensile strength tests that were performed on the actual paper handsheets. The results of these simulations provide a new insight into the mechanical behaviour of paper and interaction of fibres under deformation of paper.

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