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- Johansson, S., et al.
(author)
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3D Strain Field Evolution and Failure Mechanisms in Anisotropic Paperboard
- 2021
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In: Experimental Mechanics. - : Springer Science and Business Media LLC. - 0014-4851 .- 1741-2765. ; 61:3, s. 581-608
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Journal article (peer-reviewed)abstract
- Background: Experimental analyses of the 3D strain field evolution during loading allows for better understanding of deformation and failure mechanisms at the meso- and microscale in different materials. In order to understand the auxetic behaviour and delamination process in paperboard materials during tensile deformation, it is essential to study the out-of-plane component of the strain tensor that is, in contrast to previous 2D studies, only achievable in 3D. Objective: The main objective of this study is to obtain a better understanding of the influence of different out-of-plane structures and in-plane material directions on the deformation and failure mechanisms at the meso- and microscale in paperboard samples. Methods: X-ray tomography imaging during in-situ uniaxial tensile testing and Digital Volume Correlation analysis was performed to investigate the 3D strain field evolution and microscale mechanical behaviour in two different types of commercial paperboards and in two material directions. The evolution of sample properties such as the spatial variation in sample thickness, solid fraction and fibre orientation distribution were also obtained from the images. A comprehensive analysis of the full strain tensor in paperboards is lacking in previous research, and the influence of material directions and out-of-plane structures on 3D strain field patterns as well as the spatial and temporal quantification of the auxetic behaviour in paperboard are novel contributions. Results: The results show that volumetric and deviatoric strain, dominated by the out-of-plane normal strain component of the strain tensor, localize in the out-of-plane centre already in the initial linear stress-strain regime. In-plane strain field patterns differ between samples loaded in the Machine Direction (MD) and Cross Direction (CD); in MD, strain localizes in a more well-defined zone close to the notches and the failure occurs abruptly at peak load, resulting in angular fracture paths extending through the stiffer surface planes of the samples. In CD, strain localizes in more horizontal and continuous bands between the notches and at peak load, fractures are not clearly visible at the surfaces of CD-tested samples that appear to fail internally through more well-distributed delamination. Conclusions: In-plane strain localization preceded a local increase of sample thickness, i.e. the initiation of the delamination process, and at peak load, a dramatic increase in average sample thickening occurred. Different in-plane material directions affected the angles and continuity of the in-plane strain patterns as well as the sample and fracture properties at failure, while the out-of-plane structure affected how the strain fields distributed within the samples.
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| 3. |
- Girlanda, O., et al.
(author)
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Defect sensitivity and strength of paperboard in out-of-plane tension and shear
- 2005
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In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 31:2, s. 100-104
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Journal article (peer-reviewed)abstract
- This paper considers the effects of defects in the form of cracks on the failure properties in the thickness direction of multilayered board. The objective was to study how the peak stress value changes with various crack lengths under various load conditions. Specimens with manufactured cracks cut parallel to the machine-direction-cross-machine-direction plane were glued in the Arcan device and tested under pure tensile stress and mixed shear-tensile stress. The lower peak out-of-plane tensile stress measured in damaged samples indicates a defect sensitivity in multilayered board. The results for one type of board show that the loss in tensile strength is independent of the crack length. On the other hand, mixed shear and tensile stress behaviour does not appear to be influenced by the presence of cracks.
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| 8. |
- Nygårds, Mikael, et al.
(author)
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Experimental and numerical studies of creasing of paperboard
- 2009
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In: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 46:11-12, s. 2493-2505
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Journal article (peer-reviewed)abstract
- A laboratory creasing device to capture the most important properties of a commercial rotary creasing tool was designed. Finite element analysis of the creasing of a multiply paperboard in the laboratory crease device was presented. The multiply paperboard was modeled as a multilayered structure with cohesive softening interface model connecting the paperboard plies. The paperboard plies were modeled by an anisotropic elastic-plastic material model. The purpose of the analysis of the laboratory creasing device was to present material models that represent paperboard, and to investigate how well the analysis captured the multiply paperboard behavior during laboratory creasing. And to increase the understanding of what multiply paperboard properties that influence the laboratory crease operation. The result of the simulations showed very good correlations with the experimental obtained results. The results indicated that the paperboard properties that have the most influence is the out-of-plane shear, out-of-plane compression and the friction between the laboratory creasing device and the paperboard. © 2009 Elsevier Ltd. All rights reserved.
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