Simulation of network shrinkage

Salminen, L.; Alava, MJ; Heyden, Susanne; Gustafsson, Peter; Niskanen, Kaarlo

doi:10.3183/npprj-2002-17-02-p105-110

Cited by 6 publications

(3 citation statements)

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“…The assembled experimental material is shared as open data and can be served as a verification or calibration material for the micromechanical models Bosco et al (2015), Motamedian and Kulachenko (2019), Salminen et al (2002), Sellén and Isaksson (2014) as well as for training the machine learning algorithms to identify the fibers in micro-CT datasets, which are among the emerging techniques for the analysis of paper products.…”

Section: Hygroexpansion Coefficient As a Function Of Drying Constraintsmentioning

confidence: 99%

Microstructure and mechanical properties of free and restrained dried paper: a comprehensive investigation

et al. 2020

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The influence of strain during drying is known to have a large effect on its mechanical properties like tensile strength, Young’s modulus and hygroexpansion. In this study we investigate free and restrained dried paper and investigate the relation between the paper microstructure and its mechanical properties. The first part of the work investigates the development of the mechanical properties as well as paper internal stresses and strains (elastic-, inelastic- and hygrostrain) at different moisture contents during the drying process. Emphasis is put on the changes of hygrostrains and the paper hygroexpansion coefficient during drying. One main finding was that in constrained drying the drying stresses are considerably below the yield stress and, as a consequence, the deformations are mainly inelastic (creep) and only marginally elastic. In the second part we are analyzing the microstructure of free and restrained dried sheets by X-ray microtomography ($$\mu$$ μ -CT). From the $$\mu$$ μ -CT analysis relevant network parameters such as number of contact points, fiber bond area, free fiber length and fiber curl were extracted. Also a novel method to investigate the interface angle of the fibers in the vicinity of the bond sites was established. The results showed that the major difference from the drying procedure manifests itself in the out-of-plane curl of the fibers. Statistically number of contact points, bond area and in-plane curl were not different whereas in-plane curl and free fiber length were different. The interface angle appears to be slightly affected by the drying procedure but is overall very low.

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Section: Hygroexpansion Coefficient As a Function Of Drying Constraintsmentioning

confidence: 99%

Microstructure and mechanical properties of free and restrained dried paper: a comprehensive investigation

et al. 2020

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“…The factor that dominates the elastic modulus of paper is the effect of drying stresses, which has a much larger effect than bonding degree [119]. The same can also be demonstrated by computer simulations [120]. It has been shown experimentally that the mechanical properties of a fibre depend on the axial stress applied on the fibre during drying [121].…”

Section: Elasticity Of Papermentioning

confidence: 99%

The physics of paper

2006

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Paper is a material known to everybody. It has a network structure consisting of wood fibres that can be mimicked by cooking a portion of spaghetti and pouring it on a plate, to form a planar assembly of fibres that lie roughly horizontal. Real paper also contains other constituents added for technical purposes.This review has two main lines of thought. First, in the introductory part, we consider the physics that one encounters when 'using' paper, an everyday material that exhibits the presence of disorder. Questions arise, for instance, as to why some papers are opaque and others translucent, some are sturdy and others sloppy, some readily absorb drops of liquid while others resist the penetration of water. The mechanical and rheological properties of paper and paperboard are also interesting. They are inherently dependent on moisture content. In humid conditions paper is ductile and soft, in dry conditions brittle and hard.In the second part we explain in more detail research problems concerned with paper. We start with paper structure. Paper is made by dewatering a suspension of fibres starting from very low content of solids. The processes of aggregation, sedimentation and clustering are familiar from statistical mechanics. Statistical growth models or packing models can simulate paper formation well and teach a lot about its structure.The second research area that we consider is the elastic and viscoelastic properties and fracture of paper and paperboard. This has traditionally been the strongest area of paper physics. There are many similarities to, but also important differences from, composite materials. Paper has proved to be convenient test material for new theories in statistical fracture mechanics. Polymer physics and memory effects are encountered when studying creep and stress relaxation in paper. Water is a 'softener' of paper. In humid conditions, the creep rate of paper is much higher than in dry conditions.The third among our topics is the interaction of paper with water. The penetration of water into paper is an interesting transport problem because wood fibres are hygroscopic and swell with water intake. The porous fibre network medium changes as the water first penetrates into the pore space between the fibres and then into the fibres. This is an area where relatively little systematic research has been done. Finally, we summarize our thoughts on paper physics.

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“…For other micrometric or nanometric brous systems where proper 3D images of the brous architectures are not available, analytical or numerical structure generators were developed to estimate the previously mentioned suitable descriptors. 27,[47][48][49][50][51] For NFCbased materials, Kulachenko et al 27 recently used a numerical generation procedure to evaluate the mechanical behavior of NFC nanopapers. However, the authors did not provide compact analytical descriptors to describe the brous nanostructures.…”

Section: Introductionmentioning

confidence: 99%