This thesis investigates the effects of using various percentages of RAP and asphalt binder contents on the dynamic modulus and fatigue resistance of asphalt concrete. Two RAP percentages (20% and 40%) and three binder percentages (plant-mixed, plant-mixed + 0.5%, and plant-mixed + 1.0%) were evaluated. A Superpave gyratory compactor and an asphalt vibratory compactor were used to prepare dynamic modulus samples and fatigue beam samples at 7% air voids. Three replicate samples for each percentage of RAP and asphalt binder content were prepared for testing purposes. An Interlaken Technology Corporation servohydraulic testing machine and a Material Testing System servohydraulic machine were used to determine the dynamic modulus and fatigue resistance of the asphalt samples. Analysis of variance (ANOVA) was used to determine if any of the factors (air voids, percent RAP, and percent asphalt binder) affected the performance criteria (dynamic modulus and fatigue life cycles). Results suggest that as the amount of RAP increases in asphalt concrete, both the dynamic modulus and fatigue life will increase. As per the literature, these results were expected for the dynamic modulus, but not for the fatigue life. It is suspected that the increase in fatigue life for the 40% RAP mixes may be due to the use of a softer binder (PG 64-22 instead of PG 70-22).  It was also found that by increasing the amount of binder in the mixture, the stiffness of asphalt concrete will decrease, but the fatigue life will improve. The fatigue life results showed a strong trend of this improvement for the 20% RAP samples, however, the results for the 40% RAP samples were inconclusive. For dynamic modulus, it was found that the percent RAP, additional binder, frequency, and temperature were all statistically significant with 95% confidence. For the fatigue life, ANOVA showed that the percent RAP and additional binder were statistically significant with 95% confidence. These results suggest that by utilizing a higher percentage of RAP and asphalt binder, it is possible to meet or improve upon the dynamic modulus and fatigue life of the lower percentage of RAP samples. / Master of Science

Current mathematical models, developed on straight asphalt binders, are inadequate to characterize the frequency dependence of response of polymer-modified asphalt binders. In an earlier study at Virginia Tech, mathematical models were developed to predict the storage and loss shear moduli of polymer-modified binders. However the model developed for the loss shear moduli is limited at high frequency (G" less than or equal to 10^7.5 Pa). This thesis presents a statistical modeling of loss shear modulus of polymer (random copolymers and thermoplastic block copolymers) modified binder. Data from dynamic mechanical analysis on modified binders, at temperatures between 5 and 75°C and frequencies ranging from 0.06 to 0188.5 rad/s, were reduced to dynamic master curves of moduli, and used to develop the model. Twenty-one polymer-binder blends prepared and tested earlier at Virginia Tech where included in the study. Realistic characterization of loss shear moduli values was obtained using the Gompertz statistical model. The model was validated by using mean square error of prediction (MSEP) in which a second set of frequency data was input in the model to obtain the moduli values, which were compared to the measured data of the second set. Although this model was successfully tested for shear loss modulus prediction of polymer-modified binders, caution should be exercised when it is applied, as such a model should be able to predict the storage modulus for a known phase angle. / Master of Science

<p> The development and properties of carbon fibre are reviewed together with the properties and applications of carbon fibre reinforced plastic. Techniques for fabricating this material and certain design problems are discussed and future developments considered.</p> <p> Some simple predictions of the elastic moduli of fibre reinforced composites are compared with experimental data and a modification for the prediction of the longitudinal shear modulus suggested. Typical values for the elastic moduli of carbon fibre reinforced plastic are presented.</p> <p> A method for predicting the behaviour of laminated composite structures, which is more realistic than conventional netting analysis, is described and a computer programme for determining the strength and stiffness of such structures included.</p> / Thesis / Master of Engineering (MEngr)

BACKGROUND: The cornea is the outer portion of the eye and protects the eye from infection or debris. When the cornea becomes compromised due to age and disease (specifically Diabetes Mellitus), it becomes impaired and can have profound impacts on an individual’s quality of life by leading to vision loss or blindness. The different layers of the cornea all contain many proteins and collagen, and have varying degrees of thickness and biomechanical properties. Stiffness in the cornea has either been measured via the use of AFM (Atomic Force Microscopy) which involves removing a slice of the cornea and adhering to the surface, as a function of IOP (Intraocular Pressure), or tensile testing. Previous research has also used the nanoindenter to measure the stiffness of different layers in the intact globe (eyeball) within the mouse head or by adhering to PEG submerged in PBS. However, no studies to our knowledge have used the intact globe exposed to air and placed on a 3D printed model to measure different corneal layers via the use of nanoindentation. METHODS: 6 C57BL/6J mice were obtained between 8-12 and 27 weeks of age, had the eyes extracted, and half remained with intact epithelium while the other half had the epithelium abraded with a 1.5 mm trephine. The eyes were placed in keratinocyte solution (KCM) for preservation while they were transported to the site with a nanoindenter. The globes were then placed on a 3D printed holder, cornea facing up, and irrigated with KCM solution in between indentation measurements. The PIUMA Optics 11 Nanoindenter was used to measure the Effective Young’s Modulus of the epithelium, basement membrane, and stroma. The Oliver & Pharr modeling was used as opposed to the Hertzian Model due to the biomechanical and adhesion properties of the eye. RESULTS: A comparison of control mice at 9 weeks shows an average Effective Young’s Modulus of 30.73 kPa, and an average Effective Young’s Modulus for 15 week old mice of 62.50 kPa for the epithelium. The average Effective Young’s Modulus of the basement membrane for 9 week control mice was ~6.2 kPa and for older 27 week mice was ~6 kPa. The Effective Young’s modulus for the stroma of 9 week old mice was ~68.3 kPa and for 27 week old mice was ~ 222.7 kPa. CONCLUSION: It was observed that stiffer substrates (in this instance, stiffer layers) require stiffer probes. The opposite is true of softer substrates, which require softer probes. It is beneficial in either instance to use a larger tip radius as there will be more contact and surface area measurement, so the probe has less recoil due to the adhesion from the corneal layers. The values observed in this study correlated with the values seen in the study conducted by Xu et al. However, the basement membrane values were different and could be due to probe specifications or layer thinness. Additional studies are needed to observe changes in Young’s Modulus based on probe characteristics with diseases such as Diabetes Mellitus (DM).

No description available.

No description available.

Nanoparticles have been found to have an increasingly wide range of applications including drug delivery systems, chemical sensors, biomolecule sensors, single electron devices, catalysis, Li-ionbatteries, andsolarcells. Avarietyofmethodshavebeenused to produce nanoparticles, but one widely used approach is the application of reverse micellenanoreactorswherebyblockco-polymersareusedtoencapsulateprecursorsalts and serve as a vessel for precursor salts to react. As the encapsulation of precursor salts can be a multi-step process, some nanoparticle formulations have proven difficult to make within the reverse micelle nanoreactor. To fully understand the difficulties in nanoparticle formation, we need to have a method to probe the internal structure of the reverse micelle. This thesis presents a novel method for probing the internal structure of the reverse micelle using a quantitative mechanical mapping (QNM) mode for atomic force microscopy (AFM). Unloaded reverse micelle nanoreactors were analyzed using the QNM AFM mode. A decrease of the Young’s modulus was noted through the centroid of the reverse micelle. Many models were applied to describe the noted decrease of Young’s modulus. The end result indicated that intrinsic differences between the mechanical properties of polystyrene and poly(2vinyl pyridine) and the co-polymer orientation lead to the measured decrease in Young’s modulus through the centroid. Results from the unloaded case were used to explain changes to the reverse micelle nanoreactor after loading with precursor salts. Across all precursor salts similar trends were noted, however there was no consistent relative Young’s modulus or molar salt loading ratio noted within the trends. Three distinct loading zones were consistent acrosstheprecursorsalts. Region I wastypifiedbyaslightdecreaseinrelativeYoung’s modulus with small resultant nanoparticles. Region II was typified by linear increases in relative Young’s modulus for increases in the molar salt loading ratio. Region III was found to have two possible outcomes, either the micelle reach a maximum effective infiltration, where the relative Young’s modulus ratio no longer increases for increased molar salt loading ratio, or the micelle would unravel for increased molar salt loading ratio. Further studies should be done to confirm the existence of the universal loading regions across further co-polymers, solvents, and precursor salts. / Thesis / Master of Applied Science (MASc)

Many offshore energy infrastructures are built on carbonate sands which are skeletal remains of marine organisms. Carbonate sands have a porous grain structure and are more compressible compared to quartzitic sand grains which are abundant in alluvial depositional environments. Consequently, there is a stark difference in material behavior of carbonate sands and it is difficult to characterize this distinct behavior with conventional methods. This study focuses on micro-scale characterization of carbonate and quartzitic sands to overcome this challenge. Experimental studies consist of nanoindentation tests performed on 17 different sands; 7 quartzitic and 10 carbonate sand samples. Mechanical properties of individual sand grains with different mineralogies are determined using nanoindentation. A force is applied by the nanoindenter on the grain surface and the load-displacement curve is developed. Modulus and hardness of individual sand grains are evaluated. Nanoindentation test results show that modulus and hardness of carbonate sands are significantly lower than quartzitic sands. For quartzitic grains, mechanical properties are relatively independent of indentation depth; whereas, for carbonate grains there is a considerable decrease in both Young's modulus and hardness values with increasing indentation depth. Results from this study can further be used for the evaluation of compressibility and strength characteristics of these two types of sands as part of a multi-scale analysis framework. / Master of Science

Resilient moduli of different surface mixes placed at the Virginia Smart Road were determined. Testing was performed on Field cores (F/F) and laboratory-compacted plant mixed (F/L), laboratory mixed and compacted per field design (L/L), and laboratory designed, mixed, and compacted (D/L) specimens. The applied load was chosen to induce a strain ranging between 150 and 500 microstrains. Two sizes of laboratory compacted specimens (100-mm in diameter and 62.5-mm-thick and 150-mm in diameter and 76.5-mm-thick) were tested to investigate the effect of specimen size on the resilient modulus. At 5°C, the measured resilient moduli for both specimen sizes were similar. However, the specimen size has an effect on the measured resilient modulus at 25 and 40°C, with larger specimens having lower resilient modulus. At 5°C, HMA behaves as an elastic material; correcting for the specimen size using Roque and Buttlar's correction factors is applicable. However, at higher temperatures, HMA behavior becomes relatively more viscous. Hence, erroneous resilient modulus values could result when elastic analysis is used. In addition, due to difference in relative thickness between the 100- and 150-mm diameter specimens, the viscous flow at high temperature may be different. In general, both specimen sizes showed the same variation in measurements. Resilient modulus results obtained from F/L specimens were consistently higher than those obtained from F/F specimens. This could be due to the difference in the volumetric properties of both mixes; where F/F specimens had greater air voids content than F/L specimens. A compaction shift factor of 1.45 to 1.50 between the F/F and F/L specimens was introduced. The load was found to have no effect on resilient modulus under the conditions investigated. However, the resilient modulus was affected by the load pulse duration. The testing was performed at a 0.1s and 0.03s load pulses. The resilient modulus increased with the decrease of the load pulse duration at temperatures of 25°C and 40°C, while it increased at 5°C. This could be due to the difference in specimen conditioning performed at the two different load pulses. Finally, a model to predict HMA resilient modulus from HMA volumetric properties was developed. The model was tested for its fitting as well as predicting capabilities. The average variability between the measured and predicted resilient moduli was comparable to the average variability within the measured resilient moduli. / Master of Science

We study the continuity of mappings of finite distortion, a set of mappings intended to model elastic deformations in non-linear elasticity. We focus on continuity criteria for the inner-distortion function and prove that certain modulus of continuity estimates are sharp, i.e. cannot be im- proved. We also give a proof of the continuity of mappings of finite distortion under simplified conditions on the integrability of the distortion function. 1