Thesis--Physics--Turku--Åbo akademi, 2006. / Notes bibliogr. Annexes, 40 p.

This work investigates the effect of fibre irregularities on the mechanical behaviour of the irregular fibres using the finite element method (FEM). The first part of this work examines that the effect of fibre dimensional irregularities on the linear and non-linear tensile behaviour of the fibres, using a two-dimensional (2D) finite element models. In the linear simulation, a concept of method Young’s modulus is introduced. The method Young’s modulus, breaking load and breaking extension are affected by the magnitude and frequency of diameter variation in the fibre specimen. Fibre dimensional variation and the gauge length effect are also simulated. In the non-linear analysis, some additional information is obtained on changes in the yield and post-yield regions, which are clearly shown in the load-extension curves. Further investigation is focused on the flexural buckling behaviour of fibres with dimensional irregularities. A three-dimensional (3D) finite element model is used to simulate the buckling deformation of dimensionally irregular fibres, and the critical buckling load of the simulated fibre is calculated. Two parameters, the effective length and the average diameter within the effective length of an irregular fibre, are considered to be the key factors that influence the buckling behaviour of the fibre. An important aspect of this work is the calculation of the effective length of an irregular fibre specimen during buckling. This method has not been reported before. The third part of this work is on the combined tensile and torsional behaviour of fibres with dimensional irregularities, using a three-dimensional (3D) finite element model. Two types of fibres, polyester and wool, are simulated with sine waves of different level (magnitude) and frequency at different twist levels. For the polyester fibre, experiment verification of the simulation results has been carried out, and the results indicate the FE model is well acceptable for the simulation. The final part of this work examines the combined effect of dimensional and structural irregularities on the fibre tensile behaviour. Three-dimensional (3D) finite element models are used to simulate the cracks (transverse, longitudinal, combined transverse and longitudinal cracks) and cavities distributed in uniform fibres and fibres with 30% level of diameter variation, respectively. One of important conclusions is that under the simulated conditions, the dimensional irregularity of fibre influences the tensile behaviour of fibres more than the fibre structural irregularity. The fibre dimensional irregularity affects not only the values of the breaking load and breaking extension, but also the shape of load-extension curves. However, the fibre structural irregularity simulated in the study appears to have little effect on the shape of the load-extension curves. In addition, the effect of crack or cavity size, type and distribution on fibre tensile properties is also investigated.

Reproduction de : Thèse de doctorat : Biochimie : Clermont-Ferrand 2 : 2005. / Titre provenant de l'écran-titre. Bibliogr. p. 122-143.

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Investigations of the physical and chemical structure of archaeological fibresArchaeological fibres can be defined as natural fibres that belong to different time periods, which found in cemeteries or excavation sites. The preservation conditions cause degradation, mineralisation and sometimes a complete deterioration of these fibres, because the chemical and physical structure of the fibres changed over time in response to the specific burial environments. The ancient fibres from different archaeological sites were analysed by several non destructive analytical techniques such as optical Microscopy, Environmental Scanning Electron Microscopy, Attenuated Total Reflectance FTIR and Wide Angle X-Ray Scattering Analysis as well as destructive analytical techniques such as Scanning Electron Microscopy, Transmission Fourier Transform Infrared Spectroscopy, Energy Dispersive X-Ray Spectroscopy and Differential Scanning Calorimetry. These analytical techniques showed that keratin fibres from a central European climate have a larger damage at the fibre surface compared with frozen conditions. While bog conditions were the best in preserving the surface. FTIR analysis provides information about cystine oxidation changes in keratin fibres. For all ancient keratin fibres showed a silica peak at 1030 cm-1 which affected the symmetric cysteic acid peak at 1040 cm-1. For this reason the asymmetrical cysteic acid peak 1175 cm-1 was used for identification of cystine oxidation changes. Transmission FTIR gives a better view of the overall chemical changes in both cortex and cuticle compared to ATR analysis. All ancient wools and highly medullated Iceman deer hairs showed the highest concentration of cysteic acid compared with human hair and goat hair. Also it was shown that warm conditions have bigger effect on both the degree of oxidation of cystine and the ions uptake from the environment. The modulated DSC analysis gives a better view on the degree of degradation of hair proteins compared to WAXS analysis. To get a reliable result it is important to correct the DSC data according to the protein content of the fibre.

Thèse de doctorat : SCIENCES APPLIQUEES : Metz : 1999. / 1999METZ006S. 146 REF.

Thèse (Ph.D.)--Université Laval, 2002. / Bibliogr.: f. [138]-146. Publié aussi en version électronique.

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