| 1. |
- Björk, Elisabeth, et al.
(författare)
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Stock Preparation as a Key Operation for Making High-Quality Wet Moulded Fibre Products
- 2022
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Ingår i: TAPPICon Conference 2022. - : TAPPI Press.
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Konferensbidrag (refereegranskat)abstract
- In the global pursuit for sustainable packaging solutions, usage of different paper raw material is one of the key components to fulfil the goal. Moulded fibre products allow usage of different fibre raw material, although for today, with some restrictions. For example, recycled fibre is of varying quality and can be a challenging material to use for thermoformed wet moulding applications. Further, CTMP strength potential should be further utilized for this application. In both cases, the stock preparation is crucial. The relationship between fibre type, stock preparation, processing and performance needs to be investigated to define how to best produce high-quality wet moulded fibre products using a specific fibre type. To be able to study this a laboratory equipment for manufacturing of high-quality wet moulded fibre products has been set up. Moreover, two test methods to evaluate properties important for trays have been developed; one to evaluate how much load the tray can take and one to evaluate how much the tray will warp during handling. Together with an optimised stock preparation for different fibre raw materials studies can be performed, which aim at increased usage of fibre qualities such as recycled fibre or CTMP for high-quality moulded fibre products.
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| 2. |
- Hagman, Anton, 1984-
(författare)
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Influence of inhomogeneities on the tensile and compressive mechanical properties of paperboard
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The in-plane properties of paperboard have always been of interest to paper scientists. Tensile properties are crucial when the board is fed through converting machines at high speeds. Compressive properties are essential in the later use. Inhomogeneities affect both the compressive and tensile properties. For the tensile properties, it is the inherent heterogeneity of the paperboard that might cause problems for the board-maker. Varying material properties, through the thickness of the paperboard, are on the other hand used to achieve high bending stiffness with low fiber usage. It is of interest to know how this practice affects the local compressive properties. Papers A and B aims to address this, while C, D and E focus on in-plane heterogeneities. Paper A investigates the mechanism that causes failure in the short span compression test (SCT). It was concluded that the main mechanism for failure in SCT is delamination due to shear damage. In paper B the effect of the through-thickness profiles on the local compression strength was examined. It was concluded that the local compression is governed by in-plane stiffness and through thickness delamination. The latter was in turn dependent on the local shear strength and in-plane stiffness gradients. In paper C the tensile test is investigated with focus on sample size and strain distributions. The strain behavior was dependent on the length to width ratio of the sample and was caused by activation of local zones with high strainability. Paper D focuses on the strain zones seen in C. The thermal response in paper was studied. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. It was concluded that the heat patterns observed coincided with the deformation patterns. It could be shown that the formation was the cause of the inhomogeneous deformation. In final paper, E, the virtual field method was applied on data from C.
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| 3. |
- Hagman, Anton, 1984-
(författare)
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Investigations of In-Plane Properties of Paperboard
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In-plane properties of paperboard have always been of interest to paper mechanical researchers. The reason for this is that they play a large role for the usability of the paperboard throughout its lifespan. Tensile properties are crucial when the board is fed through printing and converting machines at high speeds in the beginning of its life. While compressive properties are essential in the later use of e.g. packages. In this thesis some methods for evaluating in-plane properties are reinvestigated.In Paper A the tensile test was investigated with focus on sample size and strain distributions. Three different multiply paperboards were examined with varying sample sizes using speckle photography. Different strain behaviour was found for different sample sizes. This difference was dependent on the length to width ratio of the sample and was caused by the activation of strain zones in the sample. These zones were of a constant size and therefore occupied different amounts of the total sample area.Paper B investigates the mechanism that causes failure in the short span compression test (SCT). Three different multiply paperboards were examined, this time chosen to have distinctly different through-thickness profiles. The boards were characterized and the data was used to simulate a SCT test with the three different boards. The simulation was conducted with a finite element model consisting of layers of continuum elements with cohesive interfaces in-between. From the model it was concluded that the main mechanism for failure in SCT is delamination that was caused by shear damage.
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| 4. |
- Hagman, Anton, 1984-
(författare)
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Mechanical and repulpability assessment of four recycled demo streams, a study
- 2023
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Ingår i: Rock the Roll: Unleashing the Harmonies of the Paper Industry. - Cleveland, USA : TAPPI Press.
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Konferensbidrag (refereegranskat)abstract
- In this study, oriented lab-sheets were produced from four different streams of base material. The reference stream was a blend virgin hardwood and softwood fibers, 50% of each. The three other streams were made of recycled material. The first recycled stream was a pure stream of unused paperboard, corresponding to “clippings”. The second recycled stream was composed of a selection of used corrugated boxes as well as some test liner. The third and final recycled stream was made to match a “1.02 quality” and consisted of 30% each of the other recycled streams and 40% journal paper. The streams were assessed with respect to repulpability (rejects, yield, adhesiveness, and visual inhomogeneity). The lab-sheets produced from each stream were evaluated through extensive mechanical testing at standard climate 23°C and 50% RH. The tests included: tensile tests, SCT, ZD-tension and compression, BCT on converted boxes and bending. Tensile tests were also performed on dried out samples as well as samples that had been conditioned at 90% RH. The repulpability study indicated that all three recycled streams had a high yield, with low amounts of adhesiveness and inhomogeneities. The mechanical testing showed, as expected, that the sheets from all three recycled streams had, overall, much lower values for the measured properties then the sheets from the virgin stream. The sheets from the clippings-stream performed better from a mechanical perspective then the sheets from the other recycled streams which were quite similar in their performance. By testing three realistic but well-behaved recycled streams, a benchmark has been created which can be used as reference data for future assessments of recycled fibers from different sources.
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| 5. |
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| 6. |
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| 7. |
- Hagman, Anton, 1984-, et al.
(författare)
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Thermographical Analysis of Paper During Tensile Testing and Comparison to Digital Image Correlation
- 2017
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Ingår i: Experimental mechanics. - : Springer. - 0014-4851 .- 1741-2765. ; 57:2, s. 325-339
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Tidskriftsartikel (refereegranskat)abstract
- The thermal response in paper has been studied by thermography. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. In the plastic regime a pattern of warmer streaks could be observed in the samples. On the same samples digital image correlation (DIC) was used to study local strain fields. It was concluded that the heat patterns observed by thermography coincided with the deformation patterns observed by DIC. Because of its fibrous network structure, paper has an inhomogeneous micro-structure, which is called formation. It could be shown that the formation was the cause of the inhomogeneous deformations in paper. Finite element simulations was used to show how papers with different degrees of heterogeneity would deform. Creped papers, where the strain at break has been increased, were analysed. For these paper it was seen that an overlaid compaction of the paper was created during the creping process. During tensile testing this was recovered as the paper network structure was strained.
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| 8. |
- Hagman, Anton, 1984-, et al.
(författare)
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Thermographical analysis of paper during tensile testing and comparison to digital image correlation
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The thermal response in paper has been studied using thermography. It was observed that an inhomogenous deformation pattern arose in the paper samples during tensile testing. In the plastic regime a pattern of warmer streaks could be observed in the samples. On the same samples digital image correlation (DIC) was used to study local strain fields. It was concluded that the heat patterns observed by thermography coincided with the deformation patterns observed by DIC. Due to the fibrous network structure paper has an inhomogenous microstructure, called formation. It could be shown that the formation was the cause of the inhomogenous deformations in paper. Finite element simulations were used to show how papers with different amount of homogeneity would deform. Creped papers, where the strain at break has been increased, were analysed. For these paper it was seen that an overlaid permanent damage was created during the creping process. During tensile testing this was recovered as the paper network structure was strained.
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| 9. |
- Hagman, Anton, 1984-, et al.
(författare)
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ZD – Directional Testing of Paperboard, Using Refined Methods to Revisit Out of Plane Properties
- 2022
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Ingår i: TAPPICon 2022 Proceedings.
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Konferensbidrag (refereegranskat)abstract
- The ZD-tensile strength is tested by attaching the top and bottom sides of a paperboard to rigid blocks that are pulled apart. In a production laboratory the strength is recorded using a tape as an adhesive. In specialized laboratories a more thorough method is available that also measures the force-displacement curve of the sample. The advanced method involves laminating and gluing the paperboard sample to metal blocks which are mounted in a universal testing machine. In this study the advanced ZD-tensile method was refined by removing the glue step and laminating the paperboard directly to the blocks. The new method was validated against the regular method with adequate results. The limits of the refined method were explored with regards to ZD-strength and paper/paperboard thickness. In an attempt to unify the ZD-tensile and -compressive behaviour of paperboard, samples were laminated and tested in combined compression and tension testing. The compressive properties were compared to non-laminated samples. The laminated samples showed a different behaviour than the non-laminated samples. The flat slope seen in the initial part of the pure compression curve disappeared, replaced by a continuous response passing 0 N. The stiffness in this region resembled the response in tensile testing.
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| 10. |
- Marin, Gustav, et al.
(författare)
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Torsional and compression loading of paperboard packages : Experimental and FE analysis
- 2023
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Ingår i: Packaging technology & science. - : John Wiley and Sons Ltd. - 0894-3214 .- 1099-1522. ; 36:1, s. 31-44
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates torsional and compressive loading of a paperboard package. Finite element (FE) analyses simulating the tests were performed to improve understanding of the stresses and deformations in the paperboard during loading. A simple experimental characterization of the necessary material properties could be performed to represent the multi-ply paperboard as a single-ply structure. The results from the single-ply model were compared with a laminate model, and the differences between the models were small. Comparing experimental and FE simulations of box compression and torsion showed that the FE models could accurately predict the response curves. However, in the simulations, there was an overprediction of the maximum compressive force and maximum torque, which was expected since geometrical imperfections and the heterogeneous internal structure of the material were not accounted for in the material model or the FE model. Local yield lines formed at the onset of non-linearities in the package load–displacement curves. Therefore, the strength of the paperboard affects the maximum compressive strength and maximum torque, and the bending stiffness of the paperboard only had a minor effect. When a first local maximum was reached, the number of FE that reached the failure stress increased exponentially. The simulations also showed that box compression was not an effect of package height, but higher packages had a lower maximum torque. © 2022 The Authors.
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