| 1. |
- Marin, Gustav, et al.
(author)
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Box compression strength of packages in different climates
- 2019
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In: 29th IAPRI Symposium on packaging, 2019.
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Conference paper (other academic/artistic)abstract
- Packages made of five folding box boards made on the same paperboard machinehave been analysed. The paperboards were from the same product series but had different grammage (235, 255, 270, 315, 340 g/m2) and different bending stiffness. Thepaperboards are normally used to make packages, and since the bending stiffnessand grammage varies the packages performance will be different. In this study, twodifferent load cases were defined and Box Compression Tests (BCT) were performedat different levels of relative humidity (30, 50, 70, 90 % RH) and were evaluated as afunction of moisture ratio.The result showed a linear relation between the box compression strength and themoisture ratio. In addition, when the data was normalized with the measurements forthe standard climate (50 % RH) and was evaluated as a function of moisture ratio, theresult indicated that the normalized box compression strength for all the paperboardsand both of the load cases could be expressed as a linear function of moisture, dependent of two constants a and b.Consequently, the study indicates that it is possible to estimate the Box compressionstrength at different climates of a package made of paperboard, by knowing the boxcompression strength for the standard climate (50 % RH and 23 °C) and the constantsa and b.
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| 2. |
- Marin, Gustav, et al.
(author)
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Elastic-plastic model for the mechanical properties of paperboard as a function of moisture
- 2020
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In: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 35:3, s. 353-361
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Journal article (peer-reviewed)abstract
- To verify a linear relation between normalized mechanical property and moisture ratio, in-plane tensile tests were performed on four types of paperboard from different manufacturers. Tensile properties were normalized with respect to the property at standard climate (50 % RH, 23 °C). Short-span Compression Tests were also performed to investigate if the relation was linear also for in-plane compression. The tests were performed at different relative humidity (20, 50, 70 and 90 % RH) but with constant temperature (23 °C) in MD and CD, respectively. The linear relation was confirmed for the normalized mechanical properties investigated. In fact, when also the moisture ratio was normalized with the standard climate, all paperboards coincided along the same line. Therefore, each mechanical property could be expressed as a linear function of moisture ratio and two parameters. Moreover, an in-plane bilinear elastic-plastic material model was suggested, based on four parameters: Strength, stiffness, yield strength and hardening modulus, where all parameters could be expressed as linear functions of moisture ratio. The model could predict the elastic-plastic behavior for any moisture content from the two parameters in the linear relations and the mechanical properties at standard climate.
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| 3. |
- Marin, Gustav, et al.
(author)
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Experimental and finite element simulated box compression tests on paperboard packages at different moisture levels
- 2020
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In: Packaging technology & science. - 0894-3214 .- 1099-1522.
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Journal article (peer-reviewed)abstract
- Finite element (FE) analyses can be used as a powerful tool in the package design process to study for instance stress and strain fields that arise during loading.An orthotropic linear elastic material model with a stress-based failure criterion was used to simulate box compression tests (BCT) of a paperboard package in the FE-solver LS-DYNA. Physical experiments were performed at 50, 70 and 90 % relative humidity (RH), respectively. The input parameters required for the simulations were calculated based on material characterization at standard climate (50 % RH and 23 °C) and a linear relation between mechanical material properties and moisture ratio established in earlier studies.The result showed that it was possible to accurately predict the load-compression curve of a BCT when moisture was accounted for. Furthermore, it was found that modelling of the mechanical properties of the creases are important for capturing the stiffness response of the package.To conclude, it was possible to predict the box compression strength and the linear stiffness response prior to the peak in the load-compression response at relevant moisture levels, by using the previously established linear relationship between moisture ratio and material properties. In addition to the moisture ratio at the preferred moisture level, the only material properties required were the in-plane strengths and stiffnesses, and the out-of-plane shear moduli at standard climate.
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| 4. |
- Marin, Gustav, et al.
(author)
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Experimental and finite element simulated box compression tests on paperboard packages at different moisture levels
- 2021
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In: Packaging technology & science. - : Wiley. - 0894-3214 .- 1099-1522. ; 34:4, s. 229-243
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Journal article (peer-reviewed)abstract
- Finite element (FE) analyses can be used as a powerful tool in the package design process to study for instance stress and strain fields that arise during loading. An orthotropic linear elastic material model with a stress-based failure criterion was used to simulate box compression tests (BCTs) of a paperboard package in the FE solver LS-Dyna. Physical experiments were performed at 50%, 70%, and 90% relative humidity (RH). The input parameters required for the simulations were calculated based on material characterization at standard climate (50% RH and 23°C) and a linear relation between mechanical material properties and moisture ratio established in earlier studies. The result showed that it was possible to accurately predict the load–compression curve of a BCT when moisture was accounted for. Furthermore, it was found that modelling of the mechanical properties of the creases are important for capturing the stiffness response of the package. To conclude, it was possible to predict the box compression strength and the linear stiffness response prior to the peak in the load–compression response at relevant moisture levels, by using the previously established linear relationship between moisture ratio and material properties. In addition to the moisture ratio at the preferred moisture level, the only material properties required were the in-plane strengths and stiffnesses, and the out-of-plane shear moduli at standard climate.
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| 5. |
- Marin, Gustav, et al.
(author)
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Experimental quantification of differences in damage due to in-plane tensile test and bending of paperboard
- 2022
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In: Packaging technology & science. - : Wiley. - 0894-3214 .- 1099-1522. ; 35:1, s. 69-80
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Journal article (peer-reviewed)abstract
- Creasing is an essential process to convert paperboards into packages since it enables folding along well-defined lines. The creasing process relies on purpose-made damage that is initiated in the paperboard structure: delamination. However, creasing might also cause in-plane cracks, which must be avoided. In this laboratory study, three paperboards were creased at six different depths, respectively. Two mechanical tests were performed to characterize the creases at standard climate (23°C and 50% RH): 2-point folding, to examine the bending force and short-span in-plane tensile test to evaluate the strength. The results were normalized with the values for the uncreased boards, which gave the relative strength ratios: relative creasing strength (RCS) and relative tensile strength (RTS). When the relative strengths were evaluated against the normative shear strains, a creasing window was formed. This window has an upper limit given by the RTS values, corresponding to the in-plane cracks, and a lower limit given by the RCS values, corresponding to the delamination damage initiated in the paperboard during creasing. It was observed that both the RCS and RTS values exhibit a linear relation against normative shear strain. From this, it was concluded that performing tests at two creasing depths might be sufficient to estimate the lower, and upper, limits for the creasing window in future studies. Finally, the effect of moisture was investigated by creasing, folding and tensile testing at 23°C and 90% RH, which showed that moisture had no clear effect on the RCS or the RTS values.
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| 6. |
- Marin, Gustav
(author)
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Impact of paperboard deformation and damage mechanisms on packaging performance
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Paper-based materials, such as paperboard, are commonly used as packaging materials. In addition to the fact that paper is renewable, there are also many other benefits of paperboard. From a mechanical point of view, paperboard has a high bending stiffness compared to its relatively low weight and high foldability, which are properties of significance in the design of packages. However, a distinct drawback of paperboard is its significant sensitivity to moisture. The moisture reduces the mechanical properties of the paperboard and consequently reduces the performance of the package. This thesis addresses the impact of paperboard deformation and damage mechanisms on packaging performance, with the characterization of the material properties as a starting point. Initially, the relations between moisture and different mechanical properties on a continuum material level were investigated. Then, experimental testing and finite element (FE) simulations were applied to evaluate these relations at the packaging design level.In Paper A, a material characterization was performed on five commercial paperboards with different basis weights, from the same producer. Five types of mechanical tests to characterize the paperboards material properties were performed:In-plane tensile test,Out-of-plane tensile test,Short-span Compression Test (SCT),Two-point folding,Double-notch shear test.All tests were performed at several levels of relative humidity (RH). Linear relations between the mechanical properties normalized with their respective value at 50 % RH and moisture ratio were found. Paper B examined whether the linear relationships discovered in Paper A are also valid for other paperboard series. Therefore, this study investigated 15 paperboards from four producers at the same RH levels as in Paper A. The paperboards were chosen to be different in furnish and construction, where four recycled boards were included. Here, the in-plane stiffnesses, strengths and SCT values were evaluated as a function of moisture. When the investigated paperboards’ moisture ratios were also normalized, all paperboards followed a linear master curve between normalized mechanical property and normalized moisture ratio. Additionally, a bilinear elastic-plastic in‑plane model was developed to predict the stress-strain relation of an arbitrary paperboard at an arbitrary moisture level without requiring mechanical testing except at standard conditions (50% RH, 23 °C).In Paper C, the master curve developed in Paper B was used to estimate material input parameters for simulating a Box Compression Test (BCT) at different moisture levels by using an orthotropic material model with a stress-based failure criterion, i.e., a relatively simple material model with few input parameters. The result showed that it was possible to accurately predict the load-compression curve of a BCT when accounting for moisture. Furthermore, it was concluded that modeling the creases’ mechanical properties is vital for capturing the stiffness response of the package. Here, a measurable approach for reducing the creases’ mechanical properties was suggested, based on a folding test to obtain the relative creasing strength (RCS) and a short-span tensile test to obtain the relative tensile strength (RTS). It should be emphasized that the model does not include any fitting parameters. All input data is based on measured values. Due to the importance of creases, the RCS and RTS ratios were investigated further in Paper D. When evaluated against normative shear strength during creasing, the RCS and RTS values together formed a creasing window, where the RTS values corresponded to in-plane cracks (upper limit) and the RCS values corresponded to delamination damage (lower limit). It was observed that both the lower and upper limits exhibit linear relations as functions of shear strain. Since creases have an evident effect on the packaging performance from a stacking point of view, it was interesting to investigate a load case exposing the package to shear. Therefore, an additional load case was investigated in Paper E: torsion of paperboard packages, where the experimental data was accurately predicted. Additionally, the effect of bending stiffness was investigated by developing two FE models. Model 1 (used in Paper C) treated the paperboard as a homogeneous material, and Model 2 considered the paperboard a three-ply laminate structure. No significant effect was noted, and it was concluded that the strength has a more significant effect on the BCT than the bending stiffness. It should also be mentioned that there were no problems with cracks when the paperboards were creased and mounted to packages used in Papers C and E. This correlates to the creasing window developed in Paper D since the creasing depth used for the packages is located within the creasing window.To conclude, the primary procedure in this thesis is developing an easy-to-use model with few material parameters that demonstrably can predict the load-deformation curves for two different load cases. The purpose of the model is not to be used for the precise prediction of failure loads but to gain knowledge about damage mechanisms during the testing procedures. A clear advantage of this approach is that the model can be used to either change the package’s geometry or perform a parametric study on the ingoing material parameters. This can also be varied for each ply separately, which helps converters and paperboard producers. It has also been shown that the model can account for different moisture levels if the master curve developed within this thesis is applied. Finally, it should be emphasized again that the model does not include any fitting parameters. All input data is based on measured values.
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| 7. |
- Marin, Gustav
(author)
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On the relation between paperboard properties and packaging performance
- 2020
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Licentiate thesis (other academic/artistic)abstract
- Paper-based materials, such as paperboard, are commonly used as packaging materials. Inaddition to the advantage that wood as a raw material is renewable, there are also many otherbenefits of paperboard. From a mechanical point of view, paperboard has a high bendingstiffness compared to its relatively low weight and has a high foldability, which both areproperties of significance in the design of packages. However, a distinct drawback withpaperboard is its significant sensitivity to moisture. The moisture reduces the mechanicalproperties of the paperboard and consequently reduces the performance of the package. Thisthesis is starting with an investigation of the relation between moisture and differentmechanical properties on a continuum material level, and then these relations are applied onthe packaging design level through experimental testing and simulations.In Paper A, a material characterization was performed on a series of five paperboards withdifferent grammages from the same producer. Five types of mechanical tests to characterizethe paperboards’ material properties were performed:• In-plane tensile test,• Out-of-plane tensile test,• Short-span Compression Test (SCT),• Bending stiffness test,• Double-notch shear test.All tests were performed at several levels of relative humidity (RH). Linear relations betweenthe mechanical properties normalized with their respective value at 50 % RH and moistureratio were found.Paper B examined whether the linear relationships discovered in Paper A are true also forother paperboard series as well. Therefore, 15 paperboards from four producers wereinvestigated in this study, at the same levels of RH as before. Here, the in-plane stiffnessesand strengths and SCT-values were evaluated as a function of moisture. When also themoisture ratios in the investigated paperboards were normalized, it turned out that allpaperboards followed the same linear relationship between normalized mechanical propertyand normalized moisture ratio. Additionally, a bilinear elastic-plastic in-plane model wasdeveloped, that can predict the stress-strain relation of an arbitrary paperboard at an arbitrarymoisture level, and without requiring any mechanical testing except at standard condition(50% RH, 23 °C).In Paper C, this relation was used to estimate input material parameters for simulating a BoxCompression Test (BCT) at different moisture levels. The result showed that it was possibleto accurately predict the load-compression curve of a BCT when moisture was accountedfor.
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| 8. |
- Marin, Gustav, et al.
(author)
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Relations Between Material Properties And Performance Of Paperboard Packages
- 2023
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In: TAPPICon 2023. - : TAPPI Press.
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Conference paper (peer-reviewed)abstract
- With material properties as a starting point, this study focuses on analyzing the performance of a paperboard package. Torsional and compressive loading of a paperboard package have been investigated through physical experiments and finite element (FE) simulations, where an orthotropic linear elastic material model with a stress-based failure criterion was used. Comparing physical experiments and FE simulations of box compression and torsion showed that the finite element models could accurately predict the response curves. Additionally, the model was utilized to investigate which impact variations in moisture, bending stiffness, and crease quality had on packaging performance. The effect of moisture was examined through an established master curve, where the necessary mechanical properties could be expressed as linear functions of moisture ratio. The impact of creases was evaluated by varying previously established ratios (relative crease strength, RCS, tensile strength, RTS) for reducing the creases’ mechanical properties in the simulations. Furthermore, the results showed that the strength of the paperboard affects the maximum compressive strength and maximum torque. Still, the bending stiffness of the paperboard only had a minor effect on box compression strength. To conclude, the model accurately predicted how moisture, crease quality, and bending stiffness affected packaging performance.
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| 9. |
- Marin, Gustav, et al.
(author)
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Stiffness and strength properties of five paperboards and their moisture dependency
- 2019
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In: International Paper Physics Conference 2019, Indianapolis, IN, USA, 5-8 May 2019. - : TAPPI Press. ; , s. 14-29
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Conference paper (other academic/artistic)abstract
- Research has been undertaken to characterise the in-plane and out-of-plane stiffness and strength properties of paperboards to enable data for use in determining constitutive parameters needed in finite element simulations. Paperboards with different bending stiffness were analysed, using five folding box boards of varying grammage (235, 255, 270, 315 and 340gsm). The stiffness and strength properties were determined at different relative humidity (RH), namely, 20, 50, 70 and 90%. As well as in-plane tensile test and out-of-plane tensile test, the short-span compression test (SCT) was carried out, together with bending stiffness test and double-notch shear test. The results revealed a linear relation between mechanical properties and moisture ratio for each paperboard. When the data were normalised with data for the standard climate (50% RH) and investigated as a function of moisture ratio, it was determined that the normalised mechanical properties for all paperboards coincided along one single line. Thus they could be expressed as a linear function of moisture ratio and two constants. It has been concluded that by knowing the structural properties for the preferred level of RH and the mechanical property for the standard climate, the mechanical properties of a paperboard could be obtained.
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| 10. |
- Marin, Gustav, et al.
(author)
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Stiffness and strength properties of five paperboards and their moisture dependency
- 2020
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In: TAPPI Journal. - : TAPPI Press. - 0734-1415. ; 19:2, s. 71-85
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Journal article (peer-reviewed)abstract
- Five commercial multiply folding boxboards made on the same paperboard machine have been analyzed. The paperboards were from the same product series but had different grammage (235, 255, 270, 315, 340 g/m2) and different bending stiffness. The paperboards are normally used to make packages, and because the bending stiffness and grammage varies, the performance of the packages will differ. Finite element simulations can be used to predict these differences, but for this to occur, the stiffness and strength properties need to be determined. For efficient determination of the three-dimensional properties in the machine direction (MD), cross direction (CD), and Z direction (ZD), it is proposed that the paperboard should be characterized using in-plane tension, ZD-tension, shear strength profiles, and two-point bending. The proposed setups have been used to determine stiffness and strength properties at different relative humidity (20,% 50%, 70%, and 90% RH), and the mechanical properties have been evaluated as a function of moisture ratio. There was a linear relation between mechanical properties and moisture ratio for each paperboard. When the data was normalized with respect to the standard climate (50% RH) and plotted as a function of moisture ratio, it was shown that the normalized mechanical properties for all paperboards coincided along one single line and could therefore be expressed as a linear function of moisture ratio and two constants. Consequently, it is possible to obtain the mechanical properties of a paperboard by knowing the structural properties for the preferred level of RH and the mechanical property for the standard climate (50% RH and 23°C).
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