| 1. |
- Hassel, B. I., et al.
(författare)
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Single cube apparatus - Shear properties determination and shear strain variation in natural density gradient materials
- 2009
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Ingår i: ICCM-17 17th International Conference on Composite Materials. - : International Committee on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- Transversal shear of softwoods was studied with the single cube apparatus (SCA). Full field strain data and FEA were used to validate the device. Once a close to pure shear strain region was confirmed, the relationship between shear strain and radial density gradient was obtained; finally an improved FE model was created.
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| 2. |
- Andersson, B., et al.
(författare)
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Micro- and meso-level residual stresses in glass-fiber/vinyl-ester composites
- 2000
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Ingår i: Composites Science And Technology. - : Elsevier Science Ltd, Exeter, United Kingdom. - 0266-3538 .- 1879-1050. ; 60:10, s. 2011-2028
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Tidskriftsartikel (refereegranskat)abstract
- Residual stresses in glass-fiber composites were studied on the micro and meso scales by computational and experimental methods. Transmitted polarized light images of thin sections were compared with 3D finite-element solutions of a sample containing 1410 fibers. Calculated point-wise stresses were derived from a linear thermoelastic model with negligibly small numerical errors. Regions with calculated maximum compressive stresses showed good agreement with experimentally observed optical bands. A material with poor interfacial adhesion showed weaker optical effects indicating fiber/matrix debonding. On the basis of these results it stems likely that irreversible matrix deformation and debonding can take place in the curing phase.
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| 3. |
- Bjurhager, Ingela, et al.
(författare)
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Towards improved understanding of PEG-impregnated waterlogged archaeological wood : A model study on recent oak
- 2010
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 64:2, s. 243-250
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Tidskriftsartikel (refereegranskat)abstract
- To prevent deformation and cracking of waterlogged archaeological wood, polyethylene glycol (PEG) as a bulk impregnation agent is commonly applied. PEG maintains the wood in a swollen state during drying. However, swelling of wood can reduce its mechanical properties. In this study, the cellular structure of oak and cell wall swelling was characterized by scanning electron microscopy (SEM) of transverse cross-sections, and the microfibril angle of oak fibers was determined by wide angle X-ray scattering (WAXS). Samples of recent European oak (Quercus robur L) impregnated with PEG (molecular weight of 600) were tested in axial tension and radial compression. Mechanical tests showed that axial tensile modulus and strength were only slightly affected by PEG, whereas radial compressive modulus and yield strength were reduced by up to 50%. This behavior can be explained by the microstructure and deformation mechanisms of the material. Microfibril angles in tensile test samples were close to zero. This implies tensile loading of cellulose microfibrils within the fiber cell walls without almost any shear in the adjacent amorphous matrix. These results are important because they can help separate the impact of PEG on mechanical properties from that of chemical degradation in archaeological artifacts, which display only small to moderate biological degradation.
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| 4. |
- Nilsson, G., et al.
(författare)
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Strain field inhomogeneities and stiffness changes in GMT containing voids
- 2002
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Ingår i: Composites. Part A, Applied science and manufacturing. - 1359-835X .- 1878-5840. ; 33:1, s. 75-85
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Tidskriftsartikel (refereegranskat)abstract
- During compression moulding of glass mat thermoplastics (GMT), voids may form. However, it is not clear whether voids are as critical to mechanical performance in GMT as in thermoset composites. The present investigation also considers the general problem of damage mechanisms in GMT. Conventional tensile tests, acoustic emission, a stiffness degradation test and a speckle technique for strain field measurements are used as well as optical microscopy of polished cross-sections. The void content (up to 5%) does not significantly influence the strength or stiffness degradation process. The reason is the large inhomogeneity of the strain fields in GMT. Failure occurs in locally soft regions and void effects are of secondary importance. Details of the failure process are discussed, emphasising the large local strains in matrix-rich regions.
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| 5. |
- Oksman, Kristiina, et al.
(författare)
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Morphology and mechanical properties of unidirectional sisal-epoxy composites
- 2002
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 84:13, s. 2358-2365
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Tidskriftsartikel (refereegranskat)abstract
- Plant fibers are of increasing interest for use in composite materials. They are renewable resources and waste management is easier than with glass fibers. In the present study, longitudinal stiffness and strength as well as morphology of unidirectional sisal-epoxy composites manufactured by resin transfer molding (RTM) were studied. Horseshoe-shaped sisal fiber bundles (technical fibers) were nonuniformly distributed in the matrix, In contrast to many wood composites, lumen was not filled by polymer matrix. Technical sisal fibers showed higher effective modulus when included in the composite material than in the technical fiber test (40 GPa as compared with 24 GPa). In contrast, the effective technical fiber strength in the composites was estimated to be around 400 MPa in comparison with a measured technical fiber tensile strength of 550 MPa. Reasons for these phenomena are discussed.
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| 6. |
- Salajkova, Michaela, et al.
(författare)
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Nanostructured composite materials from microfibrillated cellulose and carbon nanotubes
- 2009
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Ingår i: ICCM-17 17th International Conference on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- Thin composite films were prepared from the mixture of the aqueous suspension of microfibrillated cellulose (MFC) and multi-walled carbon nanotubes (MWCNTs). The morphology, electrical conductivity, and mechanical properties of the composites were characterized. Good electrical properties were obtained when the MWCNTs content was higher than 2 wt%.
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| 7. |
- Sehaqui, Houssine, et al.
(författare)
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Biomimetic aerogels from microfibrillated cellulose and xyloglucan
- 2009
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Ingår i: ICCM-17 17th International Conference on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- Cellulose aerogels with density of 7-100 kg/m3 were prepared by freeze drying from microfibrillated cellulose water suspensions, and biomimetic aerogels were prepared with the addition of xyloglucan. Their microstructures and physical properties were characterized by scanning electron microscopy, nitrogen adsorption measurements, and tensile tests.
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| 8. |
- Ansari, Farhan, et al.
(författare)
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Tensile Properties of Wood Cellulose Nanopaper and Nanocomposite Films
- 2016
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Ingår i: Multifunctional Polymeric Nanocomposites Based on Cellulosic Reinforcements. - : Elsevier Inc.. - 9780323442480 ; , s. 115-130
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The nanocellulose fibril is the major load-bearing component in the wood cell wall. It is readily disintegrated from wood pulp, and of great interest as a component in new materials. It can be used to form 100% cellulose nanofiber (CNF) nanopaper films or polymer matrix nanocomposite films of high cellulose content, where the CNF network controls most physical properties. Here, the uniaxial tensile properties of CNF nanopaper and composite films are discussed, together with the deformation mechanisms. The CNF network and most types of nanocomposite films are prepared by a scalable filtration process akin to paper-making. The effects of intrinsic CNF properties, degree of CNF dispersion, CNF-CNF adhesion, CNF-polymer matrix interaction, CNF orientation, and humidity are also discussed.
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| 9. |
- Berglund, Lars A., et al.
(författare)
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Bioinspired clay nanocomposites of very high clay content
- 2012
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Ingår i: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials. - : European Conference on Composite Materials, ECCM. - 9788888785332
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Konferensbidrag (refereegranskat)abstract
- It is difficult to prepare clay nanocomposites of high volume fraction clay. Layer-by-layer methods have been successful, but are difficult to use in large-scale production. In the present study, papermaking techniques are used for fabrication of oriented clay platelet nanocomposites. Materials are characterized by TEM, SEM, XRD and mechanical and barrier properties are measured and fire retardance performance is demonstrated. High strength and stiffness is demonstrated and the potential for bionanocomposites is discussed, in particular with moisture durability in mind.
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| 10. |
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