A method to measure the mixed-mode fatigue behavior of environmentally degraded adhesive joints was developed. Firstly, the absorption and desorption of water in two different rubber-toughened epoxy adhesives was measured gravimetrically. The water absorption in both adhesives showed anomalous behavior that was fitted to a new “sequential dual Fickian” (SDF) model. The water desorption in both adhesives was modelled accurately using Fick’s law, and there was a significant difference in the amount of retained water after drying in the two adhesives. The effects of long-term aging were studied using open-faced specimens made with two different rubber-toughened epoxy adhesives. The contrasting results illustrated the effects of environmental degradation on the matrix and toughener. Furthermore, the differences in the degradation behavior of both adhesives, combined with gravimetric and dynamic mechanical thermal analysis (DMTA) results, were used to illustrate the role of retained water in degrading the toughening mechanisms. The measured fatigue results invalidated the environmental index (EI) hypothesis for fatigue behavior, at least for the relatively short aging times studied here. Compared with aging under constant humidity, the fatigue performance of joints was found to be superior after aging in a cyclic salt-spray environment due to the lower water concentrations in the adhesive. The effects of test environment humidity and temperature on the fatigue behavior were also studied using closed, un-aged specimens. Both individual and combined effects of temperature and humidity on fatigue behavior were studied. In elevated temperature and humidity environment, joint performance at higher crack growth rates was degraded solely due to the effect of the increased temperature, whereas fatigue performance at low crack growth rates degraded predominantly because of elevated moisture. Finally, to generalise the techniques developed to automotive aluminum sheets, a reinforced specimen was developed that avoids yielding of thin aluminum sheet adherends while loading. Fatigue testing with these reinforced specimens revealed that the fatigue behavior was sensitive to the loading phase angle and the orientation of rolling lines on the sheet. These reinforced specimens were also used to study the effects of long-term aging and the effects of test environment.

In this thesis, three types of conductive membranes were fabricated and characterized for potential energy applications such as fuel cells and solar photovoltaics. First, a single layer conductive polypyrrole (PPy) membrane was synthesized and activated. Through image analysis, surface pore geometry changes were analyzed. The single layer PPy membrane was proposed as a possible additional layer or coating in polymer electrolyte membrane fuel cells. Next, a novel adaptive trilayer PPy membrane was fabricated. The membranes were activated, and characterized through changes in surface wrinkle, roughness and contact angle. A dynamic range of surface properties were observed. Lastly, conductive fibrous membranes were fabricated with electrospinning. Two methods were utilized to spin conductive fibers including the incorporation of multi-walled carbon nanotubes (MWCNT) in polystyrene (PS) and the utilization of vapor phase polymerization (VPP) to chemically synthesize PPy on electrospun FeCl3/PS oxidant fibers. Properties including fiber morphology, thermal stability and conductivity were characterized.

A method to measure the mixed-mode fatigue behavior of environmentally degraded adhesive joints was developed. Firstly, the absorption and desorption of water in two different rubber-toughened epoxy adhesives was measured gravimetrically. The water absorption in both adhesives showed anomalous behavior that was fitted to a new “sequential dual Fickian” (SDF) model. The water desorption in both adhesives was modelled accurately using Fick’s law, and there was a significant difference in the amount of retained water after drying in the two adhesives. The effects of long-term aging were studied using open-faced specimens made with two different rubber-toughened epoxy adhesives. The contrasting results illustrated the effects of environmental degradation on the matrix and toughener. Furthermore, the differences in the degradation behavior of both adhesives, combined with gravimetric and dynamic mechanical thermal analysis (DMTA) results, were used to illustrate the role of retained water in degrading the toughening mechanisms. The measured fatigue results invalidated the environmental index (EI) hypothesis for fatigue behavior, at least for the relatively short aging times studied here. Compared with aging under constant humidity, the fatigue performance of joints was found to be superior after aging in a cyclic salt-spray environment due to the lower water concentrations in the adhesive. The effects of test environment humidity and temperature on the fatigue behavior were also studied using closed, un-aged specimens. Both individual and combined effects of temperature and humidity on fatigue behavior were studied. In elevated temperature and humidity environment, joint performance at higher crack growth rates was degraded solely due to the effect of the increased temperature, whereas fatigue performance at low crack growth rates degraded predominantly because of elevated moisture. Finally, to generalise the techniques developed to automotive aluminum sheets, a reinforced specimen was developed that avoids yielding of thin aluminum sheet adherends while loading. Fatigue testing with these reinforced specimens revealed that the fatigue behavior was sensitive to the loading phase angle and the orientation of rolling lines on the sheet. These reinforced specimens were also used to study the effects of long-term aging and the effects of test environment.

In this thesis, three types of conductive membranes were fabricated and characterized for potential energy applications such as fuel cells and solar photovoltaics. First, a single layer conductive polypyrrole (PPy) membrane was synthesized and activated. Through image analysis, surface pore geometry changes were analyzed. The single layer PPy membrane was proposed as a possible additional layer or coating in polymer electrolyte membrane fuel cells. Next, a novel adaptive trilayer PPy membrane was fabricated. The membranes were activated, and characterized through changes in surface wrinkle, roughness and contact angle. A dynamic range of surface properties were observed. Lastly, conductive fibrous membranes were fabricated with electrospinning. Two methods were utilized to spin conductive fibers including the incorporation of multi-walled carbon nanotubes (MWCNT) in polystyrene (PS) and the utilization of vapor phase polymerization (VPP) to chemically synthesize PPy on electrospun FeCl3/PS oxidant fibers. Properties including fiber morphology, thermal stability and conductivity were characterized.

The stability of evaporating liquids is examined. The geometries investigated are semi-infinite liquid sheets, bounded liquid sheets, sessile droplets, and funnels. Stability parameters are generated to characterize the stability of evaporating semi-infinite liquid sheets, and bounded liquid sheets. The derivation is made possible by introducing evaporation as the specific heat transfer mechanism at the interface, and using the statistical rate theory expression for evaporation flux so there are no fitting parameters. It is demonstrated that a single parameter can be used to predict the onset criterion instead of two parameters. A linear stability analysis is performed for spherical sessile droplets evaporating on substrates constructed of either insulating or conducting materials. A stability parameter is generated to characterize the stability of sessile droplets evaporating on insulating substrates and conducting substrates. The results indicate that spherical sessile droplets evaporating on insulating substrates are predicted to transition to Marangoni convection. Since there are currently no experimental results to compare the theory with, another analysis is performed for liquids evaporating from funnels, which can be compared with existing experimental observations. A linear stability analysis predicts stable evaporation for funnels constructed of insulating materials, in contrast to the sessile droplet case, and generates a new stability parameter for funnels constructed of conducting materials. The stability parameter is free of fitting variables since the statistical rate theory expression for the evaporation flux is used. The theoretical predictions are found to be consistent with experimental observations for water evaporating from a funnel constructed of poly(methyl methacrylate) (PMMA) and for water and heavy water evaporating from a funnel constructed of stainless steel. A parametric analysis is performed on the new stability parameter for liquids evaporating from funnels constructed of conducting materials, indicating that smaller interfacial temperature discontinuities, higher evaporation rates, and smaller radii correspond to less stable systems. It is also illustrated that calculations using statistical rate theory predict an instability, which is consistent with experimental observations, whereas using the Hertz-Knudsen theory does not predict any instability.

The focus of this research is to advance the processing techniques of fabricating scaffolds for tissue engineering and to gain a better understanding of the scaffold properties and behaviours. To achieve these objectives, the fundamental properties of two widely used biomaterials, poly(lactide-co-glycolide acid) (PLGA), poly(ε-caprolactone) (PCL), and their composites with hydroxyapatite were examined. Though increasing the mechanical properties of the bulk polymers, the addition of hydroxyapatite did not affect the thermal and viscoelastic properties, suggesting little interactions may exist between the polymer and the particles. Interestingly, though the addition of the fillers increased the mechanical properties of the bulk materials, the particles worsened the mechanical properties of gas foamed/salt leached scaffolds possibly due to the struts of the porous structure having similar thicknesses as the particles. In such a case, the filler acted as stress raisers and decreased the properties of the struts. The viscoelasticity of the scaffolds was also not affected by the fillers but was affected by the testing environment. An aqueous environment caused the PLGA, but not PCL, to transition such that the porous structure was altered. These results suggest that PLGA may not be ideal for scaffolds for load bearing applications. For electrospinning, a parametric study was performed to control the scaffold morphology, but more importantly, a novel process to fabricate 3D electrospun scaffolds was developed. The novel technique exploited the plasticizing effect of pressurized carbon dioxide on the polymer such that multiple layers of the thin meshes can be sintered together without the use of heat. The process was optimized for adhering layers of PLGA and its composite with nano-hydroxyapatite, and these scaffolds have a high open-porosity and better mechanical properties compared to the gas foamed/salt leached scaffolds. Finally, a model was derived for the viscoelasticity of the bulk materials and their scaffolds by applying fractional calculus on the classical standard linear solid model based on a system of springs and dashpots. The model fitted the data, and correlations between the static mechanical properties and the fitting parameters were found such that by performing static mechanical tests, the viscoelastic behaviours can be approximated.

Advancements in the semiconductor industry have lead to the miniaturization of components and increased power densities, resulting in thermal management issues. Due to this shift, finding multifunctional materials with excellent thermal conductivity and electrical resistivity are becoming increasingly important. For this research thesis, thermally conductive polymer composites were developed and characterized. In the first study, a LLDPE matrix was combined with hBN and SiC to determine the effects of both filler type and filler content. Novel porous composite materials were also fabricated to align thermally conductive fillers, improving k_eff while significantly reducing the overall weight. In the second study, PPS was used as a high performance matrix material and combined with different types of hBN to investigate the effects of size, shape, and aspect ratio on the composite, as well as the effect of hybrid fillers. The composites were characterized with respect to their physical, thermal, electrical, and mechanical properties.

The effect of molecular weight on polypropylene (PP) extrusion foaming was investigated and the process to make soft touch, largely expanded, high cell density non-crosslinked PP foam using environmental friendly CO2 is presented. In previous research, when the cell density was high, cell opening was dominant and large expansion could not be achieved even in HMS PP materials. The effects of processing and material parameters on the foam morphologies of PP materials with three different melt flow rate (MFR) were studied using single-screw tandem foam extrusion system. By selecting proper material and die, and by tailoring the processing conditions, large expansion (25 fold) and high cell density (>109 cells/cm3) was successfully achieved in the high MFR PP without any additives. The mechanism of locally induced crystallization was found to be significantly affecting the foaming behavior of PP and was successfully verified using SEM, DSC, HPDSC, shear viscosity and solubility measurements.

Wind farm layout optimization (WFLO) is the design of wind turbine layout, subject to various financial and engineering objectives and constraints. The first topic of this thesis focuses on solving two variations of WFLO that have different analytical aerodynamic models, and illustrate deep integration of the wake models into mixed-integer programs and constraint programs. Formulating WFLO as MIP and CP enables more quantitative analysis than previous studies could do with heuristics, and allows the practitioners to use an off-the-shelf optimization solver to tackle the WFLO problem. The second topic focuses on another version of WFLO that has two competing objectives: minimization of noise and maximization of energy. A genetic algorithm (NSGA-II) is used. Under these two objectives, solutions are presented to illustrate the flexibility of this optimization framework in terms of supplying a spectrum of design choices with different numbers of turbines and different levels of noise and energy output.

The stability of evaporating liquids is examined. The geometries investigated are semi-infinite liquid sheets, bounded liquid sheets, sessile droplets, and funnels. Stability parameters are generated to characterize the stability of evaporating semi-infinite liquid sheets, and bounded liquid sheets. The derivation is made possible by introducing evaporation as the specific heat transfer mechanism at the interface, and using the statistical rate theory expression for evaporation flux so there are no fitting parameters. It is demonstrated that a single parameter can be used to predict the onset criterion instead of two parameters. A linear stability analysis is performed for spherical sessile droplets evaporating on substrates constructed of either insulating or conducting materials. A stability parameter is generated to characterize the stability of sessile droplets evaporating on insulating substrates and conducting substrates. The results indicate that spherical sessile droplets evaporating on insulating substrates are predicted to transition to Marangoni convection. Since there are currently no experimental results to compare the theory with, another analysis is performed for liquids evaporating from funnels, which can be compared with existing experimental observations. A linear stability analysis predicts stable evaporation for funnels constructed of insulating materials, in contrast to the sessile droplet case, and generates a new stability parameter for funnels constructed of conducting materials. The stability parameter is free of fitting variables since the statistical rate theory expression for the evaporation flux is used. The theoretical predictions are found to be consistent with experimental observations for water evaporating from a funnel constructed of poly(methyl methacrylate) (PMMA) and for water and heavy water evaporating from a funnel constructed of stainless steel. A parametric analysis is performed on the new stability parameter for liquids evaporating from funnels constructed of conducting materials, indicating that smaller interfacial temperature discontinuities, higher evaporation rates, and smaller radii correspond to less stable systems. It is also illustrated that calculations using statistical rate theory predict an instability, which is consistent with experimental observations, whereas using the Hertz-Knudsen theory does not predict any instability.