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  • 1.
    Björk, Elisabeth
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Muhic, Dino
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Hagman, Anton
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Halonen, Helena
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Stock Preparation as a Key Operation for Making High-Quality Wet Moulded Fibre Products2022In: TAPPICon Conference 2022, TAPPI Press , 2022Conference paper (Refereed)
    Abstract [en]

    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. 

  • 2.
    Hagman, Anton
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Evaluation of moulded pulp trays using compression test and novel twist test2019In: 29th IAPRI Symposium on packaging, 2019: Serving society innovative perspectives on packaging, 2019Conference paper (Other academic)
    Abstract [en]

    Within the industry there exists great experience of producing moulded pulp trays,this includes adjusting process parameters to achieve a consistent output from thetray making machines. However, the evaluation of the results is at this point based onhands on methods that ultimately relies on subjective opinions of what makes a goodtray. This includes visual inspection of the trays, as well as a twisting the trays by handto evaluate stiffness. Such methods might suffice to achieve a consistent output, butare not suited for structured development work, which requires objective measures.One obvious measurement is a compression test, like a box compression test. However, this test does not tell the whole story, and differs from the hands-on tests usedtoday. Because of this a twist test was developed to emulate the hands-on testingpresently used to assess the quality of moulded pulp trays. The test is performed in atensile tester, by putting the tray in a sample holder which supports two diagonal bottom corners while a beam is pressing against the opposite upper diagonal corners.This forces the tray to bend.Plotting the results from these two tests against each other, results in a practicalgraph that can be used to evaluate both pulp and process properties, as well as trayweights. This plot reveals that some information remains hidden if only compressiontests are performed.Finally, such a graph lends itself to define boundaries for what is an acceptable tray.

  • 3.
    Hagman, Anton
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Mechanical and repulpability assessment of four recycled demo streams, a study2023In: Rock the Roll: Unleashing the Harmonies of the Paper Industry, Cleveland, USA: TAPPI Press , 2023Conference paper (Refereed)
    Abstract [en]

    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. 

  • 4.
    Hagman, Anton
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Strength development during drying: possibilities with a different wet strength testing approach2019In: International Paper Physics Conference 2019, Indianapolis, IN, USA, 5-8 May 2019: preprint proceedings, TAPPI Press, 2019, p. 117-126Conference paper (Other academic)
    Abstract [en]

    A new method has been proposed for mapping the tensile behaviour of paper during drying without the need for large amounts of material. Three pulps were used to make handsheets: a long fibre pulp (softwood) and a short fibre pulp (hardwood), as well as softwood pulp mixed with microfibrillated cellulose (MFC). Comparative testing was undertaken with rewetted commercial blotting papers. Strips were produced from never dried laboratory sheets using die cutting and tested using pneumatic clamps typically used for short span tensile tests. Using the span length of 30mm, four sample points could be sequentially measured on each strip, enabling faster testing while using less material. It was found that the strength levels were different, but that the general behaviour was very similar for all three pulps. In addition, the strength increase associated with the addition of MFC was found to be present during the whole drying process. It has been concluded that the proposed new method could enable the differences between short and long fibre pulps to be examined, as well as to characterise the effect of addition of MFC.

  • 5.
    Hagman, Anton
    et al.
    KTH Royal Institute of Technology, Sweden; BiMaC Innovation, Sweden.
    Considine, J M
    USDA Forest Service, USA.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy. BiMaC Innovation, Sweden.
    Stiffness heterogeneity of multiply paperboard examined with VFM2017In: Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems. Conference Proceedings of the Society for Experimental Mechanics Series (CPSEMS) vol. 9, 2017, 2017, Vol. 9, p. 151-159Conference paper (Refereed)
    Abstract [en]

    Mechanical heterogeneity of a multiply paperboard was characterized in uniaxial tension using DIC and VFM. The specimen was divided into three subregions based on axial strain magnitude. VFM analysis showed that the subregions had stiffnesses and Poisson’s ratio’s that varied in a monotonically decreasing fashion, but with the stiffness differences between subregions increasing with applied tensile stress. An Equilibrium Gap analysis showed improved local equilibrium when comparing a homogeneous analysis with the subregion analysis. Although only a single specimen was examined, results suggest that high stiffness regions provide only marginal improvement of mechanical behavior. The analysis also showed that even though the subregions themselves were non-contiguous, their mechanical behavior was similar.

  • 6.
    Hagman, Anton
    et al.
    RISE, Innventia. KTH Royal Institute of Technology, Sweden.
    Nygårds, Mikael
    RISE, Innventia.
    Short compression testing of multi-ply paperboard, influence from shear strength2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 1, p. 123-134Article in journal (Refereed)
    Abstract [en]

    The influence of the through-thickness shear strength profiles on the short span compression test was examined. This was done both with experiments and finite element simulations on five industrial produced paperboards. It was concluded that the short span compression test is governed by in-plane stiffness and through thickness delamination. The delamination damage was in turn dependent on the local transverse shear strength and in-plane stiffness gradients. Furthermore, it was concluded that the pre-delamination mechanisms were elastic. Finally it was possible to alter the results from the test by altering the shear strength of the paperboard; this should be done uniformly over the entire middle ply of the board if an increased SCT value was what was sought after.

  • 7.
    Hagman, Anton
    et al.
    KTH Royal Institute of Technology, Sweden.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy. RISE, Innventia.
    Thermographical Analysis of Paper During Tensile Testing and Comparison to Digital Image Correlation2017In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 57, no 2, p. 325-339Article in journal (Refereed)
    Abstract [en]

    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
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Rydefalk, Cecilia
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging. KTH, Sweden.
    ZD – Directional Testing of Paperboard, Using Refined Methods to Revisit Out of Plane Properties2022In: TAPPICon 2022 Proceedings, 2022Conference paper (Refereed)
    Abstract [en]

    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. 

  • 9.
    Hagman, Anton
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy. BiMaC Innovation, Sweden.
    Timmermann, Brita
    Holmen-Iggesund, Sweden.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy. BiMaC Innovation, Sweden.
    Lundin, Andreas
    Barbier, Christophe
    Billerud-Korsnäs, Sweden.
    Fredlund, Mats
    Stora Enso, Sweden.
    Östlund, Sören
    KTH Royal Institute or Technology, Sweden.
    Experimental and numerical verification of 3D forming2017In: 16th Fundamental research symposium, 2017, p. 3-26Conference paper (Refereed)
  • 10.
    Hagman, Anton
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Trost, Thomas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Perforations on Boxes - Technical Aspects2022Conference paper (Other academic)
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  • 11.
    Hagman, Anton
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Trost, Thomas
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Perforations on boxes: some fundamental facts2019In: 29th IAPRI Symposium on packaging, 2019: Serving society innovative perspectives on packaging, 2019Conference paper (Other academic)
    Abstract [en]

    The grocery retail industry is striving with low margins and an ever-increasing competition from e-commerce applications. Therefore, as a mean to save time, money andincrease the efficiency in the supply chain, perforated shelf-ready packages (SRP) hassince a long time been used. However, there is also problems related to this perforation; it weakens the transport packaging and makes it more sensitive to damage onthe way to the shelf. The current guidelines are focused on appearance of the box onthe shelf, e.g. how much of the product is seen and evenness of perforate edge, andnot on the mechanical properties of the box.Today there exist much knowledge about perforations inhouse in the die cutting industry. This knowledge is however unattainable for outsiders. Further the questionarises about how well founded said knowledge is. The scientific literature offers littleinformation about the basics of perforation and how it affects the mechanical properties of the board and box. This study is an attempt to build knowledge, useful toconverters and industrial users, in a systematic way.In this paper several different perforations patterns have been studied from a mechanical point of view. The experiments were designed to answer some basic questionsabout how different nick lengths and distances affects the strength of the perforatione.g. at different cut/uncut ratios. Among methods studied were tensile testing, bending stiffness, compression testing and edge compression test. The different methodswere compared regarding sensitivity to discriminate between different perforationpatterns and give a useful classification of the perforation.

  • 12.
    Hagman, Anton
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Trost, Thomas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Perforations on different corrugated flute grades and their effect on packaging performance2023Conference paper (Other academic)
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  • 13.
    Marin, Gustav
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Hagman, Anton
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Östlund, Sören
    KTH Royal Institute of Technology, Sweden.
    Nygårds, Mikael
    KTH Royal Institute of Technology, Sweden; BillerudKorsnäs, Sweden.
    Torsional and compression loading of paperboard packages: Experimental and FE analysis2023In: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 36, no 1, p. 31-44Article in journal (Refereed)
    Abstract [en]

    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. 

  • 14.
    Srinivasa, Prashanth
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Hagman, Anton
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Pendergraph, Samuel
    RISE - Research Institutes of Sweden.
    Sundström, Jonas
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    On the torsion method for measurement of out-of-plane shear properties2019In: International Paper Physics Conference 2019: preprint proceedings, TAPPI Press, 2019, p. 8-13Conference paper (Other academic)
    Abstract [en]

    Torsional loading with combined out-of-plane compressive loading has been studied for its viability in measurement of out-of-plane shear properties. Paperboards of two qualities were evaluated, namely paperboard A, which was a multiply, while paperboard B was a single ply. Both paperboards were produced on commercial paperboard machines. A total of 24 samples were prepared, 12 of each quality, which were tested under four different load levels. Three different out-of-plane compressive load levels were tested in addition to test without compressive load. Results have been presented from the successful tests in terms of torque versus angle of torsion and shear stress versus shear strain plots. It has been demonstrated that the technique was suitable for out-of-plane shear measurements. An order of magnitude agreement in the values of the properties was obtained in the torsional test method and the rigid block shear tests. Results indicated a possible stable post-peak response in shear loading at sample sizes that would provide material properties comparable with that of a homogeneous test. The torsional setup offered benefit of ease of applying out-of-plane axial loads, both in compression and tension.

  • 15.
    Thorman, Sofia
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Rydefalk, Cecilia
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Hagman, Anton
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Granlöf, Lars
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Dynamic out-of-plane compression of paperboard — Influence of impact velocity on the surface2024In: TAPPI Journal, ISSN 0734-1415, Vol. 2024-February, p. 113-122Article in journal (Refereed)
    Abstract [en]

    Processes that convert paperboard into finished products include, for example, printing, where the paperboard is subjected to rapid Z-directional (ZD) compression in the print nip. However, measuring and evaluating the relevant properties in the thickness direction of paperboard are not necessarily straightforward or easy. Measuring at relevant, millisecond deformation rates further complicates the problem. The aim of the present work is to elucidate some of the influences on the compressive stiffness. Both the initial material response and the overall compressibility of the paperboard is studied. In this project, the effect on the material response from the surface structure and the millisecond timescale recovery is explored. The method utilized is a machine called the Rapid ZD-tester. The device drops a probe in freefall on the substrate and records the probe position, thus acquiring the deformation of the substrate. The probe is also allowed to bounce several times on the surface for consecutive impacts before being lifted for the next drop. To investigate the time dependent stiffness behavior, the probe is dropped several times at the same XY position on the paperboard from different heights, thus achieving different impact velocities. The material response from drops and bounces combined allows study of the short-term recovery of the material. The material in the study is commercial paperboard. The paperboard samples are compared to material where the surface has been smoothed by grinding it. Our study shows that there is a non-permanent reduction in thickness and a stiffening per bounce of the probe, indicating a compaction that has not recovered in the millisecond timescale. Additionally, a higher impact velocity has an initial stiffening effect on the paperboard, and this is reduced by smoothing the surface.

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  • 16.
    Thorman, Sofia
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Rydefalk, Cecilia
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Hagman, Anton
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Granlöf, Lars
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Rapid, Out-Of-Plane Compression of Paperboard – Influence of Impact Velocity on The Surface2023In: TAPPICon 2023 - "Rock the Roll: Unleashing the Harmonies of the Paper Industry", TAPPI Press , 2023Conference paper (Refereed)
    Abstract [en]

    Industry processes, such as printing, subjects paperboard to rapid, Z-directional compression. However, measuring and evaluating the relevant properties in the thickness direction are not necessarily straight forward or easy. Measuring at relevant, millisecond, deformation rates complicate the problem further. The aim of the present work is to elucidate on some of the influences on the compressive stiffness. Both the initial material response and the overall compressibility of the paperboard is studied. In this project the effect on the material response from the surface structure and the millisecond time-scale recovery is explored. The method utilized is a machine called the Rapid ZD-tester. The device drops a probe in free fall on the substrate and records the probe-position, thus acquiring the deformation of the substrate. To investigate the time dependent stiffness behavior the probe is dropped several times at the same xy-position on the paperboard from different heights, thus achieving different impact velocities. The probe is also allowed to bounce several times on the surface before lifted for consecutive drops. The drop-bounce cycle allows study of the short-term recovery of the material. The material in the study is commercial paperboard. The paperboard samples are compared to material where the surface has been smoothed by grinding it. Our study shows that there is a non-permanent reduction in thickness and a stiffening per bounce of the probe, indicating a compaction that has not recovered in the millisecond timescale. Additionally, a higher impact velocity has an initial stiffening effect on the paperboards, and that this is reduced by smoothing the surface.

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