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Thèse (M.Sc.)--Université Laval, 2008. / Bibliogr.: f. 93-99. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. Description based on print version record. Includes bibliographies: leaves 56-57, 72.

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A novel accelerometer based on light modulation has been designed and a prototype device manufactured. The device utilises the change in refractive index brought about by stress induced by the applied vibration. A detailed mathematical analysis of several feasible sensing designs has been performed to aid the design process. A mathematical model has been developed to assess the performance characteristics of the light modulated accelerometer the results of which were also used as a design tool. The prototype accelerometer was tested, from 1 g to 50 g between frequencies of 25 Hz to 2000 Hz, on a vibration system under three modulation schemes. The acceleration response of the device was seen to be linear over the testing range whilst the frequency response dropped off initially and levelled off at approximately 1 kHz. An experimental accelerometer was also assembled on the vibration table so that various materials could easily be tested without having to undergo precise machining. The acceleration and frequency responses showed similar behaviour to those obtained with the prototype accelerometer. However, the actual response levels varied with each material. To aid in the development of the accelerometer the stress-optic and thermo-optic coefficients have been determined for a range of polymeric materials. The stress optic coefficient was determined for polycarbonate, polymethyl methacrylate, polvinyl chloride and araldite epoxy resin using a circular polariscope and two interferometer configurations up to the yield stress of the materials tested. Each material showed a constant coefficient over the testing range. The results obtained using each technique were in good agreement with each other and the limited literature data available. The thermal variation of refractive index was also determined for the same materials. The Abbe refractometer was used for the determination between 5 and 140°C using five wavelength sources and two interferometer configurations using a HeNe laser from -50°C to approximately 30° above the glass transition temperatures. The change in index was found to be linear over the temperature range tested. However, at the glass transition temperature a change in gradient was observed with each material. Two simple mathematical relationships were used to predict the thermo-optic coefficient. These gave values reasonably close to those obtained in experiment.

Modulus reduction and damage accumulation during fatigue cycling of an injection moulded composite been studied. The material is a long, discontinuous glass fibre reinforced nylon composite having a skin/core structure. A continual decrease in modulus with cycling is observed for composite and single skin layer specimens. During fatigue cycling of composite specimens damage accumulates in both the skin and core layers and both layers contribute to the measured modulus reduction. Damage accumulation in the core, in the form of transverse cracks, is studied in detail. These cracks initiate predominantly at the free edges and grow across the specimen width with cycling. A milling/dye penetrant technique is developed to quantify the cracking and average crack spacings are related to measured modulus reductions at a range of peak stresses. The experimental data is compared with predictions made using a shear-lag model developed for continuous fibre cross-ply laminates relating modulus reduction to average crack spacing. A theoretical model, based on the Cox model, is derived to predict modulus reduction/cycling curves for skin layer specimens. Cracking patterns in the core are predicted using a strain energy release rate approach which is compared with experimental data. Empirical relationships, derived for the modulus reduction of the skin and core layers are combined to predict modulus reduction/cycling curves at a range of specimen widths and stress levels.

The strength of carbon fibres in unidirectional hybrid composites of glass and carbon fibres have been investigated. It has been shown that the strength distributions of bundles of carbon fibres impregnated with resin, both unsupported and in a hybrid, may be described by the Weibull model confirming earlier reports. The primary objective of this work has been to investigate the strength and the state of dispersion of the carbon component. Hybrid composites consisting of accurately aligned arrays of bundles in two and three dimensions have been fabricated and tested. It has been shown that the strength decreases when the bundle spacing is less than a critical distance but at very low spacings the strength begins to increase again. This observation is explained with reference to the fracture behaviour and the implications for practical composites are discussed. The hybrid composites exhibit a greater strength over impregnated bundles. An hypothesis is proposed to explain this phenomena which combines thermal effects with the constraining influence of the glass and the differences in the severity of flaws in hybrid bundles. The last two arguments result in a larger critical group of failed fibres being required in the hybrid before catastrophic failure occurs. The type of hybrid specimen tested in this work enables the fracture process in the composite to be followed closely. The investigation has in principle supported the model for composite strength proposed by Batdorf, the "critical i-plet" model. However, experimental evidence indicated that a slightly different fracture process to that proposed by Batdorf was operating. The significance of this fracture process with respect to the strength and the size effect in composites is discussed.

Experiments aimed at elucidating the identity of antigenic metabolites of practolol, using in vitro generated practolol metabolites and sera from practolol patients, were unsuccessful as none of the sera tested contained measurable concentrations of antimetabolite antibodies. Collaborative experiments with workers who had originally established the technique also failed to detect such antibodies. It was concluded, after follow up studies, that the active sera must have been used up or damaged during the original investigations. Rabbits and guinea-pigs, injected with the protein bound practolol metabolites did not respond by synthesising antimetabolite antibodies. The probable reason for the lack of response was the low concentration of hapten binding (1 metabolite molecule/6 protein molecules). A ratio of at least 10:1 is normally used in such experiments and ratios of greater than 100:1 are not uncommon. Neither in vitro generated metabolites of practolol nor chemical analogues, had any effect on human skin fibroblast growth or collagen synthesis in vitro. In contrast, practolol, propranolol and paracetamol all inhibited these fibroblasts functions in a dose related fashion. Cells from uninvolved skin of a psoriasis patient were more sensitive to the inhibitory actions of the two 3-receptor blocking drugs than fibroblasts obtained from a control volunteer but were less sensitive to paracetamol indicating a variation in the response to 3-receptor blocking drugs and that such changes in sensitivity need not be paralleled by chemically related compounds such as paracetamol. Practolol was not taken up by the fibroblasts to any great extent indieating that its site of action was the plasma membrane. Uptake of leucine was inhibited to the same extent as collagen synthesis suggesting that practolol may interfere with protein synthesis by limiting substrate availability. In vitro morphological studies are consistent with the idea that the three drugs act by different mechanisms although further studies are necessary to confirm this. The following conclusions can be drawn from the experimental findings. - The side effects of practolol are more likely to have been due to the parent molecule than to a metabolite. - The action of practolol is likely to have been an inhibitory, rather than a stimulatory, one. - Susceptible patients have an increased sensitfvity to practolol which could be reflected in the response of fibroblasts from such patients in vitro.

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