Advances in DNA micro and macroarray technologies made these high-throughput systems good candidates for the development of cheaper, faster and easier qualitative and quantitative detection methods. In this study, a simple and cost effective sandwich hybridization-based method has been developed for the rapid and sensitive detection of various unmodified recombinant elements in transgenic plants. Attention was first focused on the optimization of conditions such as time, concentration and temperature using commercial ssDNA, which in turn could be used for real sample detection. In this sandwich-type DNA chip platform, capture probes complementary to the first half of recombinant element (target adapter) were immobilized onto poly-L-lysine covered conventional microscope slides. PCR-amplified un-purified target adapter and biotin labeled detection probe, which is complementary to the second half of target adapter, were hybridized in solution-phase to complementary capture probes to create a sandwiched tripartite complex. Later, hybridization signal was visualized by the attachment of streptavidin conjugated Quantum Dot to the sandwiched complex under UV illumination. Sandwich based array system that has been developed in this study allows multiplex screening of GMO events on a single DNA chip platform. 35S promoter, NOS terminator, CRY1Ab and BAR target sequences were successfully detected on the same DNA chip platform. The platform was able to detect unlabeled PCR amplified DNA fragments of CaMV 35S promoter sequence and NOS terminator and BAR transgene sequences from transgenic potato plants and NK603 Certified GMO Reference material, respectively. The DNA-chip platform developed in this study will allow multiple detection of label-free PCR-amplified transgenic elements from real GMO samples on a single slide via a cost effective, fast, reliable and sensitive sandwich hybridization assay.

<p>The use of composite materials in vehicle structures could reduce the weight and thereby the fuel consumption of vehicles.</p><p>As the road safety of the vehicles must be ensured, it is vital that the energy absorbing capability of the composite materials are similar to or better than the commonly used steel structures. The high specific bending stiffness of sandwich structures can with advantage be used in vehicles, provided that the structural behaviour during a crash situation is well understood and possible to predict. The purpose of this thesis is to identify and if possible to describe the failure initiation and progression in in-plane compression loaded sandwich panels.</p><p>An experimental study on in-plane compression loaded sandwich panels with two different material concepts was conducted. Digital speckle photography (DSP) was used to record the displacement field of one outer face-sheet surface during compression. The sandwich panels with glass fibre preimpregnated face-sheets and a polymer foam core failed due to disintegration of the face-sheets from the core, whereas the sandwich panels with sheet molding compound face-sheets and a balsa core failed in progressive end-crushing. A simple semi-empirical model was developed to describe the structural response before and after initial failure.</p><p>The postfailure behaviour of in-plane compression loaded sandwich panels was studied by considering the structural behaviour of sandwich panels with edge debonds. A parametrical finite element model was used to determine the influence of different material and geometrical properties on the buckling and postbuckling failure loads. The postbuckling failure modes studied were debond crack propagation and face-sheet failure. It could be concluded that the postbuckling failure modes were mainly determined by the ratio between the fracture toughness of the face-core interface and the bending stiffness of the face-sheets.</p>

Stiffness and strength models are derived for simply supported composite sandwich panels comprised of fibre-reinforced face sheets and polymer cores subject to symmetric four point bending and uniformly distributed loading. Optimal trajectories for minimum mass design are calculated using the models and situated on failure mechanism maps. A stiffness constraint is also derived to omit beam designs of excessive compliance. Analytical models were validated through an extensive series of experiments, considering beams comprised of GFRP face sheets with ROHACELL 51-IG and extruded polystyrene (EPS) polymer cores. An alternate loading fixture was used to simulate uniform pressure loads. In general, experiments were able to validate most analytical expressions for a range of experimental conditions. Though the predictions worked well with most beam cases, analytical models were noted to become unreliable for short or slender beams.

Stiffness and strength models are derived for simply supported composite sandwich panels comprised of fibre-reinforced face sheets and polymer cores subject to symmetric four point bending and uniformly distributed loading. Optimal trajectories for minimum mass design are calculated using the models and situated on failure mechanism maps. A stiffness constraint is also derived to omit beam designs of excessive compliance. Analytical models were validated through an extensive series of experiments, considering beams comprised of GFRP face sheets with ROHACELL 51-IG and extruded polystyrene (EPS) polymer cores. An alternate loading fixture was used to simulate uniform pressure loads. In general, experiments were able to validate most analytical expressions for a range of experimental conditions. Though the predictions worked well with most beam cases, analytical models were noted to become unreliable for short or slender beams.

The structural vibration damping behaviour of plates and beams can be improved by the application of viscoelastic passive damping materials. Unconstrained layer damping treatments applied to metal plate systems were studied experimentally. Design and modelling of novel fibre reinforced constrained layer damping materials was performed, and implementation of these composite damping materials into laminated composite sandwich constructions commonly used as structural elements within large composite marine vessels was explored. These studies established effective methods for examining, designing and applying damping materials to metal and composite marine structures. Two test fixtures were designed and constructed to facilitate testing of viscoelastic material damping properties to ISO 6721-3 and ASTM E756. Values of material damping made in accordance with ASTM E756 over a range of temperatures were compared to values produced by a Dynamic Mechanical Analyser (DMA). Glass transition temperatures and peak damping values were found to agree well, although results deviated significantly at temperatures above the glass transition temperature. The relative influence of damping layer thickness, ambient temperature, edge conditions, plate dimensions and substrate material on the system damping performance of metal plates treated with an unconstrained viscoelastic layer was investigated experimentally. This investigation found that substrate material had the greatest influence on system damping performance, followed by damping layer thickness and plate size. Plate edge conditions were found to have little influence on the measured system damping performance. These results were dependent on the values of each variable used in the study. Modal damping behaviour of a novel fibre reinforced composite constrained layer damping material was investigated using finite element analysis and experimental methods. The material consisted of two carbon fibre reinforced polymer (CFRP) layers surrounding a viscoelastic core. Opposing complex sinusoidal fibre patterns in the CFRP face sheets were used to achieve stress-coupling by way of orthotropic anisotopy about the core. A finite element model was developed in MATLAB to determine the modal damping, displacement, stress, and strain behaviour of these complex patterned fibre constrained layer damping (CPF-CLD) materials. This model was validated using experimental results produced by modal damping measurements on CPF-CLD beam test specimens. Studies of multiple fibre pattern arrangements found that fibre pattern properties and the resulting localised material property distributions influenced modal damping performance. Inclusion of CPF-CLD materials in laminated composite sandwich geometries commonly used in marine hull and bulkhead constructions was studied experimentally. Composite sandwich beam test specimens were fabricated using materials and techniques frequently used in industry. It was found that the greatest increases in modal damping performance were achieved when the CPF-CLD materials were applied to bulkhead geometries, and were inserted within the sandwich structure, rather than being attached to the surface.

Honeycomb core sandwich panels are widely used in the aeronautic industry due to their excellent flexural stiffness to weight ratio. Generally, classical homogenized model is used to model honeycomb core sandwiches in order to have an efficient but not expensive numerical modeling. However, previous works have shown that, while the homogenized models could correctly represent the membrane waves' behavior of sandwiches in a large frequency range, they could not give satisfying simulation results for the flexural waves' behavior in the high frequency range (HF). In fact, the honeycomb core layer plays an important role in the propagation of the flexural waves, so that when the involved wavelengths become close to the characteristic lengths of honeycomb cells, the cellular microstructure starts interacting strongly with the waves and its effect should no longer be neglected, which is unfortunately not the case of the homogenized models. In the present work, we are interested in improving the theoretical and numerical analysis of HF elastic waves' propagation in honeycomb core sandwich panels by a numerical approach based on the Bloch wave theorem, which allows taking into account the periodic characteristics of the honeycomb core. In fact, by decomposing non-periodic wave solutions into their periodic Bloch wave basis modes, numerical models are defined on a basic cell and solved in a efficient way, and provide a better description and so a better understanding of the interaction between HF wave propagation phenomena and the periodic structures. Our numerical approach is developed and validated in the cases of one-dimensional periodic beam structures, of two-dimensional periodic hexagonal and rectangular beam structures and of honeycomb core sandwich plates. By solving the eigenvalue problem of the Bloch wave modes in one primitive cell of the periodic structure for all the wave vectors located in the corresponding first Brillouin zone in the phase space, the dispersion relation between the wave vector and the eigenvalue is calculated. The analysis of the dispersion relation provides important results such as: the frequency bandgaps and the anisotropic and dispersive characteristics of periodic structures, the comparison between the first Bloch wave modes to those of the classical equivalent homogenized models and the existence of the retro-propagating Bloch wave modes with a negative group velocity.

Thesis (M. Eng.)--Carleton University, 1999. / Includes bibliographical references (p. 164-166). Also available in electronic format on the Internet.

Thesis (M. Eng.)--Carleton University, 2000. / Includes bibliographical references (p. 152). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 119-133) Also available in print.

Thesis (M. Hous. M.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves ii-xv).