Content: The research on Collagen that possesses unique fibre structure are reported frequently. In this paper, the cross image of leather fibre of dried wet blue cowhide embedded with and without epoxy resin were investigated with micro computed topography(MCT). The images obtained by MCT of leather fibre are original status without any damage, while the embedded leather can emerge distortion because the fibre was fixed during the solidifying and immersing of the resin. In this research, 2357 images of leather fibre were investigated on wet blue leather(original fibre) and the same piece of leather embedded by epoxy resin(embedded fibre). The area ratio of the sections from the original fibre and the embedded fibre was examined for each image. The statistic results showed that the mode of area ratio of the original fibre section to the entire fibre section is 75%, and the mode of area ratio of the embedded fibre section to the embedded fibre entire section is only 48%. The mode of the area ratio of the original fibre is obviously higher than the mode of the area ratio of the embedded fibre, that is diverse with the anticipation of fibre swelling caused by resin. The reason might be the expansion of interval space among the fibre filled with epoxy resin, otherwise the conglutination of fibre caused by the evaporation of solvent(acetone used in embedding) in the course of the resion solidifying. Likewise, it can be the adhesion of the tiny fibre with the larger fibre that will diminish the area caculated. The factors will be studied further on embedding to achieve a method with minimum deformation on cross image of fibre. Take-Away: The area ratio of cross section on embedded fibre shrunk comparing with the original fibre, that is out of anticipation of the probable swelling created by resin.

The main objective of this thesis was to improve the understanding of some aspects on wood and fibre mechanics related to conditions in the thermomechanical pulping process. Another objective was to measure the power distribution between the rotating plates in a refiner.   The thesis comprises the following parts: –A literature review aimed at describing fracture in wood and fibres as related to the thermomechanical pulping process –An experimental study of fracture in wood under compression, at conditions similar to those in feeding of chips into preheaters and chip refiners –An experimental study of the effect of impact velocity on the fracture of wood, related to conditions of fibre separation in the breaker bar zone in a chip refiner –A micromechanical model of the deterioration of wood fibres, related to the development of fibre properties during the intense treatment in the small gap in the refining zone –Measurements of the power distribution in a refiner.   The fracture in wood under compression was investigated by use of acoustic emission monitoring. The wood was compressed in both lateral and longitudinal directions to predict preferred modes of deformation in order to achieve desired irreversible changes in the wood structure. It was concluded that the most efficient compression direction in this respect is longitudinal. Preferable temperature at which the compression should be carried out and specific energy input needed in order to achieve substantial changes in the wood structure were also given.   The fibre separation step and specifically the effect of impact velocity on the fracture energy were studied by use of a falling weight impact tester. The fracture surfaces were also examined under a microscope. An increase in impact velocity resulted in an increase in fracture energy. In the thermomechanical pulping process the fibres are subjected to lateral compression, tension and shear which causes the creation of microcracks in the fibre wall. This damage reduces the fibre wall stiffness. A simplified analytical model is presented for the prediction of the stiffness degradation due to the damage state in a wood fibre, loaded in uni-axial tension or shear. The model was based on an assumed displacement field together with the minimum total potential energy theorem. For the damage development an energy criterion was employed. The model was applied to calculate the relevant stiffness coefficients as a function of the damage state. The energy consumption in order to achieve a certain damage state in a softwood fibre by uniaxial tension or shear load was also calculated. The energy consumption was found to be dependent on the microfibril angle in the middle secondary wall, the loading case, the thicknesses of the fibre cell wall layers, and conditions such as moisture content and temperature. At conditions, prevailing at the entrance of the gap between the plates in a refiner and at relative high damage states, more energy was needed to create cracks at higher microfibril angles. The energy consumption was lower for earlywood compared to latewood fibres. For low microfibril angles, the energy consumption was lower for loading in shear compared to tension for both earlywood and latewood fibres. Material parameters, such as initial damage state and specific fracture energy, were determined by fitting of input parameters to experimental data. Only a part of the electrical energy demand in the thermomechanical pulping process is considered to be effective in fibre separation and developing fibre properties. Therefore it is important to improve the understanding of how this energy is distributed along the refining zone. Investigations have been carried out in a laboratory single-disc refiner. It was found that a new developed force sensor is an effective way of measuring the power distribution within the refining zone. The collected data show that the tangential force per area and consequently also the power per unit area increased with radial position. The results in this thesis improve the understanding of the influence of some process parameters in thermomechanical pulping related wood and fibre mechanics such as loading rate, loading direction, moisture content and temperature to separate the fibres from the wood and to achieve desired irreversible changes in the fibre structure. Further, the thesis gives an insight of the spatial energy distribution in a refiner during thermomechanical pulping.