| 1. |
- Kao-Walter, Sharon, et al.
(författare)
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A Comparison of 2-zone and 3-zone Models in Tearing based on Essential Work of Fracture
- 2009
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Konferensbidrag (refereegranskat)abstract
- Two different models (2-zone and 3-zone) for describing the deformation and fracture behavior of tearing ligament was compared and discussed based on the experimental results made by Kim et al. The models are based on the Essential Work of Fracture approach for predicting the specific total work of fracture along the tear path across plastic zones. The experiment and analysis were based on 2-leg trousers tear specimen. The materials chosen in this work were PET (0.508 mm). The results showed that the accuracy of 3-zone model was higher than 2-zone model. It was found that this difference is because the 2-zone model did not consider the plastic deformation caused by loading prior to tearing. Also a finite element model was created to simulate the behavior around the crack tip.
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| 2. |
- Kao-Walter, Sharon, et al.
(författare)
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Acoustic imaging internal microstructure of a packaging material
- 2008
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Konferensbidrag (refereegranskat)abstract
- Microstructure of a paper-based packaging material was studied by acoustic microscopy method. The laminate structure of the packaging material contains paperboard, polymer and aluminium, which are widely used for aseptic liquid food package. The method has also been used to detect delaminations inside the material. The results show the possibility to study the micro structural features of paperboard, polymer and aluminium foil layered materials by applying the high-resolution ultrasonic acoustic microscopy. The potential for visualization defects in the body of this kind of materials is discussed in order to further develop the Non-Destructive Testing (NDT) method in food packaging industries.
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| 3. |
- Kao-Walter, Sharon, et al.
(författare)
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Tearing and Delaminating of a Polymer Laminate
- 2011
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Ingår i: Key Engineering Materials. - : @scientific.net. - 1013-9826. ; 465, s. 169-174
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Tidskriftsartikel (refereegranskat)abstract
- The fracture behaviour of laminated materials was studied in this work. The materials used in this work were low-density polyethylene (LDPE) laminated on polyethylene (PET). The thickness of the LDPE was 27 μm and the PET was 100 μm. Experiments were performed by using a 2-leg trousers specimen to analyse the tearing behaviour of the laminate in relation to the delamination. A clear delamination zone was observed during the crack propagation by tearing. Furthermore, a finite element calculation was performed to simulate the behavior around the crack tip during the tearing. A correlation between adhesion and crack propagation was discussed. Finally, the theory of Essential Work of Fracture (EWF) was used for predicting the specific total work of fracture along the tear path across the plastic zones.
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| 4. |
- Kao-Walter, Sharon, et al.
(författare)
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Tensile and Tearing Fracture Behaviour of Food Packaging Laminate
- 2007
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fracture behaviour of laminated food packaging materials is studied. The materials used in this work were the single layer of Aluminium foil (Al-foil), Low density polyethylene (LDPE) and the lamination of these single layers. Experiments were performed by applying the centred crack specimen as well as the 2-leg trousers specimen. It was observed that the load carrying capacity increased for the tensile and decreased for the tearing specimen when the two layers are laminated together. It was also found that in the case of tearing the crack growth was not only initiated by shear stress but also by normal stress. A modified strip yield model and the essential work of fracture theory were used to analyze the deformation and the fracture behaviour. The initial crack growth of the single layers and the laminate during the tensile and tearing were compared and investigated.
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| 5. |
- Andreasson, Eskil, et al.
(författare)
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Experimental and Numerical fracture of cracks emanating from different types of flaws in thin polymer films
- 2013
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Konferensbidrag (refereegranskat)abstract
- Fracture mechanical Mode I tensile testing has been performed on an oriented polyproplyne film used in packaging industry. Physical Tensile testing for the continuum material has been performed to observe the material strength and to extract continuum material properties for numerical analysis. Fracture mechanical testing of different shaped notches is performed to observe the failure initiation in the material. A brittle-like failure was shown in the polypropylene film while the low density polyethylene presented a highly ductile behavior. A finite element method (FEM) strategy has been successfully developed to perform numerical analysis of polymer films. The developed FEM model gives an accurate and approximate method to compare and analyze the experimental and numerical results. The obtained results have shown a very fine similarity under theoretical, experimental and numerical analysis. Depending on crack geometry different shape crack effects showed the transferability of localized stresses at different points around the crack. Fracture surface and fracture process is analyzed using scanning electron microscope (SEM). Brittle failure with small deformation and presence of small voids and their coalescence has also been shown in SEM micrographs for LDPE material. The methods discussed will help classify different groups of materials and can be used as a predictive tool for the crack initiation and crack propagation path in packaging material, especially thin polymer films.
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| 6. |
- Andreasson, Eskil, 1976-
(författare)
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Mechanics and Failure in Thin Material Layers : Towards Realistic Package Opening Simulations
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The final goal of this PhD-work is an efficient and user-friendly finite element modelling strategy targeting an industrial available package opening application. In order to reach this goal, different experimental mechanical and fracture mechanical tests were continuously refined to characterize the studied materials. Furthermore, the governing deformation mechanisms and mechanical properties involved in the opening sequence were quantified with full field experimental techniques to extract the intrinsic material response. An identification process to calibrate the material model parameters with inverse modelling analysis is proposed. Constitutive models, based on the experimental results for the two continuum materials, aluminium and polymer materials, and how to address the progressive damage modelling have been concerned in this work. The results and methods considered are general and can be applied in other industries where polymer and metal material are present. This work has shown that it is possible to select constitutive material models in conjunction with continuum material damage models, adequately predicting the mechanical behaviour in thin laminated packaging materials. Finally, with a slight modification of already available techniques and functionalities in a commercial general-purpose finite element software, it was possible to build a simulation model replicating the physical behaviour of an opening device. A comparison of the results between the experimental opening and the virtual opening model showed a good correlation.The advantage with the developed modelling approach is that it is possible to modify the material composition of the laminate. Individual material layers can be altered, and the mechanical properties, thickness or geometrical shape can be changed. Furthermore, the model is flexible and a new opening design with a different geometry and load case can easily be implemented and changed in the simulation model. Therefore, this type of simulation model is prepared to simulate sustainable materials in packages and will be a useful tool for decision support early in the concept selection in technology and development projects.
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| 7. |
- Andreasson, Eskil, et al.
(författare)
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Micro-mechanisms of a laminated packaging material during fracture
- 2014
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Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 1873-7315 .- 0013-7944. ; 127, s. 313-326
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Tidskriftsartikel (refereegranskat)abstract
- The micro-mechanisms of fracture in a laminate composed of an aluminium foil and a polymer film are considered in this study. The laminates as well as the individual layers, with and without premade centre-cracks, were tensile tested. Visual inspection of the broken cross-sections shows that failure occurs through localised plasticity. This leads to a decreasing and eventually vanishing cross-section ahead of the crack tip for both the laminate and their single constituent layers. Experimental results are examined and analysed using a slip-line theory to derive the work of failure. An accurate prediction was made for the aluminium foil and for the laminate but not for the freestanding polymer film. The reason seems to be that the polymer material switches to non-localised plastic deformation with significant strain-hardening. (C) 2014 Elsevier Ltd. All rights reserved.
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| 8. |
- Andreasson, Eskil, et al.
(författare)
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Trouser tear tests of two thin polymer films
- 2013
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Konferensbidrag (refereegranskat)abstract
- Trouser tear testing has been concerned in this research work. A polypropylene film and a low density polyethylene film used in the packaging industry are considered. The experimental trouser tear tests showed different results for both materials when they were subjected to load in different material directions. Therefore the hypothesis was verified, that the in-plane material orientation/alignment induced during manufacturing, hence creating anisotropic in-plane mechanical properties, also affects the tearing behavior. A brittle-like failure was shown in the polypropylene film while the low density polyethylene presented a highly ductile behavior. The two polymer films can be classified as one low-extensible and one high-extensible material according to the test method utilized. Material parameters in the principal material directions i.e. manufacturing direction and cross direction were extracted from the experimental tests for further numerical studies. Scanning electron microscope was used for micromechanical and fractographical analysis of the crack tip and crack surfaces created during the tests. The methods discussed will help classify different groups of materials and can be used as a predictive tool for the crack initiation and crack propagation path in packaging material, especially thin polymer films.
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| 9. |
- Bjerkén, Christina, et al.
(författare)
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Fracture Mechanisms of a Thin Elastic Plastic Laminate
- 2006
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Konferensbidrag (refereegranskat)abstract
- The fracture toughness of a polymer-metal laminate composite is obtained by mechanical testing of a specimen containing a pre-crack. The laminate is a material used for packaging. It consists of a thin aluminium foil and a polymer coating. A centre cracked panel test geometry is used. Each of the layers forming the laminate is also tested separately. The result is compared with the measured fracture strength of the individual layers. It is observed that the load carrying capacity increases dramatically for the laminate. At the strain when peak load is reached for the laminate only aluminium is expected to carry any substantial load because of the low stiffness of the LDPE. However, the strength of the laminate is almost twice the strength of the aluminium foil. The reason seems to be that the aluminium forces the polymer to absorb large quantities of energy at small nominal strain. The toughness compares well with the accumulated toughness of all involved layers. Possible fracture of the interface between the layers is discussed.
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| 10. |
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