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Agarwal, Shubham

University of British Columbia

Creped tissue papers are lightweight products widely used as paper towels, facial tissues, napkins, and toilet tissues. They are characterized by high failure strain (stretch) and a nonlinear tensile response due to their low areal density and bonded fiber networks. Their manufacturing involves depositing a dilute suspension of wood fibers onto a moving fabric (wire), consolidating it into a network, and adhering it to a heated, rotating cylinder. The dried network is then scraped off with a stationary blade in a process called creping, which creates micro-folds and ruptures inter-fiber bonds. These steps significantly influence the network architecture and tensile properties. For instance, jet and wire speeds impact anisotropy, fiber deposition on the wire introduces out-of-plane topography (wiremark), and creping forms a microfolded structure with a nonlinear tensile response. The aim of this thesis is to investigate the tensile response of tissue paper networks across various manufacturing stages using modelling at two scales. At the macroscale, the impact of the crepe structure on tensile properties is studied with a Discrete Elastoplastic Model, where the creped sheet is idealized as a segmented triangular wave deforming via extension and bending. The Crepe Index is introduced as a measure of folding, highlighting the roles of material and geometric nonlinearities in determining tensile behavior. At the network level (mesoscale), a Discrete Element Method (DEM)-based model is developed to explore the effects of areal density, fiber orientation, fiber size, and out-of-plane topography on pre-creped sheets. This approach reveals distinct features of tissue fiber networks, such as high non-affinity, anisotropy, unique scaling exponents, and the importance of bending and twisting deformations. A 3D creping model is also used to investigate how adhesive and network properties interact during creping, causing transitions in structural and tensile characteristics. These models provide valuable insights into the structure-property relationships of creped tissue papers, enabling a better understanding of their unique mechanical behavior and the influence of manufacturing processes.

Text

2024-11-21

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89697

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/