This study examines the hypothesis that coniferous wood fibre origin is maintained even when purified pulps are subjected to severe mechanical (beating) and chemical (decrystallizing) treatments. Four to five intra-incremental sulphate pulps obtained from each of three species, eastern larch (Larix lariaina (Duroi) K. Koch), Douglas fir (Pseudotsuga menziessii (Mirb.) Franco) and balsam fir (Abies balsamea (L.) Mill), were purified and machined to one or three levels EL (170 ± 45 ml Csf), DF (615 + 90 ml Csf; 328 + 43 ml Csf; 168 ± 62 ml Csf) and BF (190 + 30 ml Csf). Thereafter, cellulose supermolecular structures were altered by monoethylamine swelling, with changes (48 ± 2% vs. 68 ± 2%) quantified as fibre crystallinity index measured by X-ray diffractometry. Paper sheet apparent densities and tensile parameters (maximum strength, "stretch," modulus of elasticity and rupture energy) were determined. Fibre surface areas and sheet bonded states were estimated by light scattering coefficient measurements. The effects of wood origin on paper sheet physical-mechanical properties reported by other researchers were reaffirmed in this study, with all factors decreasing progressively across growth increments. The differences of wood intra-incremental, as well as species origins, were not removed by conventional pulping and papermaking processes, or additional treatments such as severe beating or major alteration of the basic cellulose structures as practiced in the study. Paper sheet tensile properties were related directly to sheet apparent density. Correlation coefficients as high as 0.979 and 0.989 were obtained for 00% and 82% monoethylamine decrystallized fibre sheets, respectively. Sheet density was inversely related to wood specific gravity and was found to be independent of wood species, degree of beating and decrystallization treatments. It is shown that fibre bonding potential is not the only factor influencing paper sheet strength. Intrafibre characteristics, such as cellulose supermolecular structures, have a highly significant effect on paper sheet strength as well. In addition, specific energy of "bond failure" (irreversible energy consumed per unit sheet surface formed as result of tensile straining) was higher for earlywood than for latewood sheets. This energy quantity depends on beating degree and differs according to species, as well as intra-incremental origin. The paper sheet light scattering coefficient (L.S.C.)-density relationship also depended on wood fibre origin. Earlywood sheet L.S.C. decreased with increased beating and sheet density, but latewood sheet L.S.C. remained almost unaffected. This observation explains why whole-wood fibre sheet L.S.C.-density relationships vary with pulp types as recorded in the literature. / Forestry, Faculty of / Graduate

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In this work, we investigate several aspects of photonic crystal waveguides through modeling and simulation. We introduce a one-dimensional model for two-dimensional photonic crystal fibers (PCFs), analyze tapered PCFs, analyze planar photonic crystal waveguides and one-dimensional PCFs with infinite periodic cladding, and investigate transmission properties of a novel type of fiber, referred to as Fresnel fiber. A simple, fast, and efficient one-dimensional model is proposed. It is shown that the model is capable of predicting the normalized propagation constant, group-velocity dispersion, effective area, and leakage loss for PCFs of hexagonal lattice structure with a reasonable degree of accuracy when compared to published results that are based on numerical techniques. Using the proposed model, we investigate tapered PCFs by approximating the tapered section as a series of uniform sections along the axial direction. We show that the total field inside the tapered section of the PCF can be evaluated as a superposition of local normal modes that are coupled among each other. Several factors affecting the adiabaticity of tapered PCFs, such as taper length, taper shape, and number of air hole rings are investigated. Adiabaticity of tapered PCFs is also examined. A new type of fiber structure, referred to as Fresnel fiber, is introduced. This fiber can be designed to have attractive transmission properties. We present carefully designed Fresnel fiber structures that provide shifted or flattened dispersion characteristics, large negative dispersion, or large or small effective area, making them very attractive for applications in fiber-optic communication systems. To examine the true photonic crystal modes, for which the guidance mechanism is not based on total internal reflection, photonic crystal planar waveguides with infinite periodic cladding are studied. Attention will be focused on analytical solutions to the ideal one-dimensional planar photonic crystal waveguides that consist of infinite number of cladding layers based on an impedance approach. We show that these solutions allow one to distinguish clearly between light guidance due to total internal reflection and light guidance due to the photonic crystal effect. The analysis of one-dimensional PCFs with infinite periodic cladding is carried out in conjunction with an equivalent T-circuits method to model the rings that are close to the core of the fiber. Then, at sufficiently large distance from the core, the rest of the cladding rings are approximated by planar layers. This approach can successfully estimate the propagation constants and fields for true photonic crystal modes in both solid-core and hollow-core PCFs with a high accuracy. <i>Original file (released May 10, 2007) replaced Oct. 3, 2012 GMc per DePauw]</i> / Ph. D.

The material properties of fibre networks and fibre reinforced composites are strongly influenced by fibre-fibre interactions. Stress transfer between load bearing elements in such materials is often dictated by the nature of the fibre-fibre interface. Inter-fibre bonding is solely responsible for internal cohesion in paper, because all stresses transferred between fibres operate through fibre-fibre bonds. . The future development of cellulosic fibre materials will require an improved understanding of the fibre-fibre interface. Fluorescence resonance energy transfer (FRET) was proposed as a new tool for the study of fibre interfaces. A protocol for covalent linkage of fluorophores to natural and regenerated cellulosic fibres was developed and the absorptive and emissive properties of these dyes were characterized. The fluorescent response of these dyed fibres in paper sheets was studied using steady-state fluorescence spectroscopy. Fluorescence micrographs of fibre crossings on glass slides were analyzed using the FRETN correction algorithm. Energy transfer from coumarin dyed fibres to fluorescein dyed fibres at the interface was observed. The FRETN surfaces for spruce and viscose rayon fibre crossings were distinctly different. The FRET microscopy method was able to detect statistically significant differences in spruce fibre interface development when fibre fraction and wet pressing were varied. The coalescence of natural cellulosic fibre interfaces during drying was also observed with the technique. Polysaccharide films were employed as model systems for the natural and regenerated cellulose fibre interfaces. It was found that pressing cellulose films did not result in significantly increased FRETN either due to resistance to deformation or the inability to participate in interdiffusion. Conversely, xylan films demonstrated a drastic increase in the FRETN signal with increased wet pressing. These results support the previously observed differences between regenerated cellulose fibres and natural wood fibres. The results of the FRETN analysis of the polysaccharide film model systems suggest that lower molecular weight amorphous carbohydrates are likely to be significant contributors to fibre interface development.

This diploma thesis is focused on monitoring of mechanical response of long-fiber reinforced polymer composite. Main part of this thesis was preparation of long-fiber reinforced composite specimens, on which matrix was reinforced by commercially sized glass fibers. For comparison of properties were prepared specimens reinforced by unsized glass fibers. Apart from preparing specimens reinforced by long glass fibers were prepared specimens contains long carbon fibers. For evaluation of mechanical response of the prepared composite specimen were used flexural test and short beam shear test. Mechanical response was evaluated with universal testing machine ZWICK Z010 and data were processed in OriginPro 8 program. Thanks to evaluation of the mechanical response of the prepared specimens was assessed adhesion to fiber-matrix interface. By examining the mechanical response or adhesion can be assessed efficiency of commercial fiber surface treatment and so standardize measurement to compare other options of surface treatments.

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Call number: LD2668 .T4 1933 W525