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Micromechanical Modelling of Wood and Fibre Properties
Wood is a material with mechanical properties that vary markedly, both within a tree and among trees. Moisture changes lead to shrinkage or swelling and modify the mechanical properties. In the present study both experimental and numerical work concerning the stiffness and the hygroexpansion properties of wood and of fibres and variations in them is presented. The experimental work involves both characterizing the structure of wood at the microstructural level and the testing of clear-wood specimens. The experiments at the microstructural level provide valuable information concerning the cellular structure of wood, information needed for modelling wood on the basis of its microstructure. Deformations in the microstructure due to loading, as characterized by use of a SEM, was also studied. The longitudinal modulus of elasticity, three hygroexpansion coefficients and the density along the radius from pith to bark in the stem were determined by the testing of clear wood specimens. The longitudinal modulus of elasticity and the three shrinkage coefficients were shown to vary considerably along the radial direction of the stem. Models based on the microstructure for determining the stiffness and shrinkage properties of wood are proposed. The models investigated include the chain of modelling from the mechanical properties of the chemical constituents of the cell wall to the average mechanical properties of a growth ring. The models are based mainly on results of the experiments that were performed. Models of the microfibril in the cell wall as well as models of the cellular structure of wood were developed with the aim of determining the stiffness and shrinkage properties of wood from simply a few key parameters. Two models of the cellular structure of wood were investigated. In one of these, the structure was composed of irregular hexagonal cells, whereas in the other the cell structures were obtained from micrographs. Parametric studies performed by use of the hexagonal cell model are presented. The results of ...
Micromechanical Modelling of Wood and Fibre Properties
Wood is a material with mechanical properties that vary markedly, both within a tree and among trees. Moisture changes lead to shrinkage or swelling and modify the mechanical properties. In the present study both experimental and numerical work concerning the stiffness and the hygroexpansion properties of wood and of fibres and variations in them is presented. The experimental work involves both characterizing the structure of wood at the microstructural level and the testing of clear-wood specimens. The experiments at the microstructural level provide valuable information concerning the cellular structure of wood, information needed for modelling wood on the basis of its microstructure. Deformations in the microstructure due to loading, as characterized by use of a SEM, was also studied. The longitudinal modulus of elasticity, three hygroexpansion coefficients and the density along the radius from pith to bark in the stem were determined by the testing of clear wood specimens. The longitudinal modulus of elasticity and the three shrinkage coefficients were shown to vary considerably along the radial direction of the stem. Models based on the microstructure for determining the stiffness and shrinkage properties of wood are proposed. The models investigated include the chain of modelling from the mechanical properties of the chemical constituents of the cell wall to the average mechanical properties of a growth ring. The models are based mainly on results of the experiments that were performed. Models of the microfibril in the cell wall as well as models of the cellular structure of wood were developed with the aim of determining the stiffness and shrinkage properties of wood from simply a few key parameters. Two models of the cellular structure of wood were investigated. In one of these, the structure was composed of irregular hexagonal cells, whereas in the other the cell structures were obtained from micrographs. Parametric studies performed by use of the hexagonal cell model are presented. The results of ...
Micromechanical Modelling of Wood and Fibre Properties
Persson, Kent (author)
2000-10-01
other:ISRN: LUTVDG/TVSM--00/1013--SE
TVSM-1000; (TVSM-1013) (2000) ; ISSN: 0281-6679
Theses
Electronic Resource
English
DDC:
690
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