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The influence of low molecular weight additives containing polar groups and modified polyolefin-based compatibilisers on polypropylene (PP)-clay nanocomposites (PPCN) has been studied, in terms of intercalation and degree of exfoliation achievable by melt state mixing processes. PPCN were prepared by melt mixing of two commercial pp homopolymers with organically modified clay (OMMT) in the presence of maleic anhydride grafted pp (PP-MA). X-ray diffraction (XRD) analysis shows that the interlayer spacing of clay increases dramatically, whilst transmission electron microscopy (TEM) results show a significant improvement of clay dispersion in the PP matrix, when nanocomposites are prepared with commercial PP containing short chain organic additives with polar groups (amide-type slip and antistatic additives). Subsequent studies based upon customised PP formulations, with short chain amide molecules (AM), confirm the intercalation of this additive into clay galleries. The maximum interiayer spacing is achieved with low concentrations of this additive (0.5 wt. %). Contact angle measurements and low shear melt flow properties (MF!) further confirm the diffusion of this additive (AM) into the clay galleries rather than migrating away from the bulk of the PPCN. The interaction between the polar group (CONH2) of this additive and polar sites of the clay surface appears to be the driving force for the intercalation. Although this additive intercalates and allows the formation of an intercalated nanocomposite structure with non homogeneous dispersion of clay, an exfoliated PPCN structure is yet to be formed with this additive alone. A new preparation method for PPCN has therefore been developed by co-intercalation of AM and PP-MA. PPCN were prepared by this method with a significant reduction of overall PP-MA concentration in the nanocomposite structure, relative to conventional PPCN prepared with compatibiliser (PP-MA) only. XRD and TEM analysis showed that nanocomposite structures are formed with significantly improved clay dispersion, compared to PPCN prepared using the conventional method. Quantification of clay exfoliation, using image analysis software, showed that higher degrees of exfoliation can be achieved in PPCN from this new cointercalation method. Normalised melt flow index (n-MFI) data showed the relationship between low shear flow properties and clay structure and is an appropriate parameter to examine clay exfoliation and its interaction with pp in PPCN. Enhanced thennal stability of PPCN, in comparison to pure PP, further demonstrates the improved clay dispersion in nanocomposite structures prepared by the co-intercalation method. A possible mechanism for the co-intercalation of AM and PP-MA into clay galleries has been proposed, based upon hydrogen bonding between these additives and the silicate layers. Rheological characterisation of PPCN, using capillary rheometry experiments at high shear rates, shows a shear thinning, pseudoplastic behaviour similar to pure PP. However, a comparatively higher concentration of AM appears to reduce the shear viscosity of PPCN. Die swelling behaviour revealed a reduction in melt elasticity in PPCN melts in comparison to unmodified PP. Reduced die swell occurs as a result, together with a delay in the onset of melt fracture. Sheet extrusion was used to produce PPCN products with increasing clay loading levels that were evaluated for a range of mechanical properties. Significant enhancement of modulus in PPCN is achieved in comparison to pure PP whilst maintaining similar strength characteristics. However, impact resistance of extruded PPCN sheets is not improved in comparison to unmodified PP. Results have been interpreted with reference to the degree of exfoliation, additive content and differences in PP crystallinity.

This paper presents the results of an effort to use geophysical measurements such as seismic wave velocities and electrical resistivities to calculate airfield design parameters. The study converts all geophysical measurements to equivalent California Bearing Ratio (CBR) values, comparing CBR values estimated from DCP penetration resistance with CBR values estimated from shear wave velocity and electrical resistivity values. Relationships linking the geophysical measurements to CBR estimates were established using laboratory data and applied to field in-situ measurements. The elastic modulus (E) is the stiffness parameter involved in predicting soil strength and stiffness. This research aims to relate electrical conductivity and modulus by using a box test. A sigmoidal model was proposed for the prediction of elastic modulus as a function of conductivity, which performed well with high-strength soil. Soil tests from two different source locations were considered at different moisture contents, with a total of eight tests analyzed. The results show that elastic modulus values estimated from both shear wave velocity and DCP measurements tend to perform better at low conductivity and higher stiffness soil types. However, the elastic modulus from the proposed model does not match well with the DCP or shear wave velocity data when applied a field site located in Rouen, France. Overall, this study demonstrates the viability of using geophysical methods to assess airfield suitability and improve the accuracy of soil assessment in airfield design.

During the last 20 years, asphalt pavements were built in New Mexico (NM) and around the country using mostly Superpave coarse graded mixes as opposed to fine graded mixes. This is because coarse mix uses larger aggregates with good interlocking and requires less asphalt binder than a fine mix, while both mixes fulfill the Superpave criteria. Recently, it was observed nationally that the Superpave coarse graded mixes have good field rutting performances but poor cracking performances. It is hypothesized that fine graded mix can help improve pavement cracking performances. The idea is, the fine mixes would have less air voids which would transmit less air and water, and thereby, fine mixes would have less aging/cracking and moisture damage, respectively. In an effort to examine fine and coarse mix performances, mixes were collected from NM 14 that was built using the coarse mix in the southbound lane and a fine mix in the northbound lane. Both fine and coarse mixes have used identical performance grade (PG) binders, reclaimed asphalt pavement (RAP) materials, and aggregate sources. Mixes were compacted in the laboratory, and samples were tested for dynamic modulus, Hamburg Wheel Tracking Device (HWTD) rutting, beam fatigue (BF), and Thermal Stress Restrained Specimen Test (TSRST). The coarse mix shows higher dynamic moduli and better rutting performances than the fine mix, which was expected. Surprisingly, the fine mix failed (more than 12.5 mm rutting for 10,000 passes) in HWTD rutting. The fatigue test data have been analyzed by employing the viscoelastic continuum damage model (VECD). The analysis results reveal that the coarse mix has better resistance to fatigue damage and higher fatigue life than the fine mix. TSRST test results demonstrate higher failure strength and lower failure temperature for coarse mix compared to fine mix. Based on these results, this study postulates that simply replacing coarse mix with a fine mix cannot be the way to address the Superpave pavements’ cracking issue, rather continue looking for other solutions, for example, a balanced mix or gradation.

Patients with type 2 diabetes (T2DM) have higher fracture risk compared to patients without T2DM despite having comparable to higher bone mineral density (BMD). Thus, T2DM might alter other aspects of resistance to fracture beyond BMD such as bone geometry, microarchitecture, and tissue material properties. In this study, we characterized the skeletal phenotype of the TallyHO mouse model of T2DM. The minimum moment of inertia was smaller (-26%) and cortical porosity was greater (+490%) in TallyHo femurs compared to controls. Whole-bone mechanical properties were examined in three-point bending tests to failure of the femurs. Post-yield displacement was lower (-35%) in the TallyHO mice relative to that in C57Bl/6 age-matched controls after adjusting for body mass. The tissue level mechanical properties were determined by nanoindentation. The cortical bone of TallyHO mice was stiffer and harder, as indicated by greater mean tissue indentation modulus (+20%) and hardness (+15%) compared to controls. Raman mineral:matrix ratio and crystallinity were greater in TallyHO mice than in C57Bl/6 mice (mineral:matrix +10%, crystallinity +1%, both p < 0.05). Tissue level hardness and crystallinity increased with worsening hyperglycemia. The smaller femoral minimum moment of inertia and higher cortical porosity, which is related to lower structural resistance of bone in bending is compensated by increased tissue modulus and hardness to maintain whole-bone stiffness and strength in TallyHO mice. Furthermore, increased tissue mineralization and crystallinity could explain lower ductility in TallyHO mice.

Calcite (the most stable form of CaCO3) is a common mineral that naturally exists in geology and biology, and can also be grown synthetically. In its pure and defect-free form, calcite is relatively soft and brittle. Amazingly though, despite its intrinsic shortcomings as a structural material, calcite often serves a structural purpose in biology. For example, the teeth, shells, and spines of many marine organisms contain, or are entirely composed of, calcite. These biogenic calcite-containing structures are much stronger and tougher than a pure control calcite crystal, and small-scale indentation testing suggests that even the single-crystals of calcite that make up these structures may be significantly harder than a pure control. The exact mechanisms of the increased hardness are not known, thus there is much interest in creating model synthetic calcite crystals to replicate and help explain such hardening effects. However, it is difficult to interpret the differences in hardness between different biogenic and synthetic calcites because the reference hardness of pure single-crystal calcite is not well known (there are large variations in previously-reported data). In this work, strides are made towards achieving a better understanding of the strengthening of biogenic and synthetic calcites in three ways: (1) Previous reports of the indentation hardness of calcite are compiled and compared, and new experiments are performed to quantify the effect of the indentation size effect and crystal anisotropy on hardness measurements of calcite. (2) A new indentation method is developed that allows for accurate measurements to be made on small, embedded particles (like biogenic and synthetic calcite crystals), by accounting for the effect of a dissimilar matrix material. And (3) it is demonstrated that the hardness of pure synthetic calcite crystals can be increased by simply varying the kinetics of their growth. Additionally, previously published collaborative work (included in the Appendix) explains an important impurity-based strengthening mechanism in calcite.

The objective was to develop and characterize a potential method to alleviate the issues regarding post impact effective modulus of composites in a tubular geometry. The hypothesis was that the use of a metallic substrate may increase post impact stiffness characteristics of the sample geometry, compared to a traditional fiber reinforced composite tube, in the torsion and tensile loading scenarios. This required the manufacture of non substrate fiber reinforced composite samples and aluminum substrate composite samples, and testing under torsion and tension loading scenarios. Main sample testing was carried out below the sample yield point, and therefore tests were nondestructive in nature. This research has concluded with statistical significance that an aluminum substrate decreases loss in torsional effective modulus following impact compared to a composite shaft only composed of carbon fiber reinforced epoxy. Samples with both aluminum sleeve factor levels produced significantly lower post impact effective modulus change compared to traditional composite counterparts. This appears to be correlated with the elimination of visible fiber and matrix rupture during the impact event. Therefore, torsional effective modulus decrease of the aluminum sleeve tubes appears to be dictated by tube geometry change. This is in contrast to traditional composite tubes, where a decrease in effective modulus was primarily dictated by the decrease in fiber cross sectional area. This research has concluded that the aluminum substrate decreases post impact tensile effective modulus change compared to traditional composite tubes, but statistical significance could not be attained due to the high degree of variance within each of the sleeve thickness factor levels. Samples with aluminum sleeves produced lower post impact effective modulus change compared to the traditional composite counterparts, but each sample sleeve thickness factor level variance was relatively high compared to the difference in mean values.

Presented in this work is the development of a novel variable modulus, porous PDMS-membrane based ALI cell culture model to assess cell growth under tissue matched stiffness conditions, tight-junction formation, and response to nanoparticle (NP) exposures. Using Sylgard 184 and 527 polydimethylsiloxane (PDMS) and corn syrup emulsions, produced 5 micron thick, highly porous membranes. Membranes spanning 1 kPa-1000 kPa have been achieved, modeling both healthy and fibrotic physiological lung tissue stiffness respectively. Scaffold microstructure and mechanics, cellular proliferation and viability under submerged and ALI conditions, were assessed. The viability was assessed using a Guava 12HT flow cytometer with Viacount reagent. Submerged exposure to 30 nm tannic acid stabilized gold or zinc oxide will be conducted for 8, 24, and 48 hours at 0, 1, 5, 10, 20, and 100 µg/ml. Inductively coupled plasma-mass spectrometry (ICP-MS) will be performed on the apical supernatants. A model system capable of capturing the unique mechanics and membrane properties found at the alveolar-endothelial interface could better predict toxicity, safe levels of exposure, and provide a rapid-means to assess new materials, pharmacologics, or potentially hazard chemicals.

The use of warm mix asphalt (WMA) technologies and recycled materials, such as reclaimed asphalt pavement (RAP) in the pavement industry has increased widely in the past few years due to their various economic and environmental benefits. Consequently, these topics have garnered the interest of many researchers, and have led to many studies that have evaluated the performance and durability of such pavements. One of the main issues concerning WMA pavements is the binder aging. Since WMA is produced at lower temperatures than conventional hot mix asphalt (HMA) mixtures, the binder is expected to experience lower aging level as compared to HMA. Hence, studying the aging properties of WMA binders is essential in the evaluation of the performance of WMA pavements. For the use of RAP in asphalt mixture, there are concerns about the blending between the RAP and virgin binders in the mixture and the properties of the blend within the interfacial blending zone surrounding the aggregates. This dissertation is divided into two major parts: the first part evaluates aging in foamed warm mix asphalt and the second part evaluates blending properties between virgin binders and RAP binders. This was done at mainly a microscale level using Atomic Force Microscopy (AFM).Part 1 was presented in chapter 3. This part specifically evaluates the effects of aging on the micro-mechanical and chemical properties of foamed WMA and HMA asphalt materials. Two asphalt binders that met the performance grade of PG 70-22 and PG 64-22 were considered. Atomic force microscopy (AFM) was used to examine the micromechanical and adhesion properties of the asphalt binders considered at different aging conditions. In addition, Fourier-transform infrared spectroscopy (FTIR) and gel permeation chromatography techniques were used to identify the changes in the chemical composition of different asphalt binders due to aging. A rolling thin-film oven (RTFO) and pressure aging vessel (PAV) methods were utilized to simulate the short-term and long-term aging in the binders. Also, short-term and long-aging methods in accordance with AASHTO R 30 specifications were done on the HMA and WMA produced mixtures. The binder from each mixture was then extracted and recovered for testing. The results from the three tests indicated that WMA binders experienced equivalent or significantly lower aging over the service life of pavement as compared to HMA binders. The AFM results showed that WMA and HMA binders had similar aging levels for both performance grades. The micro-mechanical and adhesion properties of the asphalt binders were affected by the short-term and long-term aging, as well as the chemical properties and composition of these binders based on GPC and FTIR tests. Additionally, RTFO and PAV aging methods did not consistently show similar aging levels to short-term and long-term aged HMA and WMA binders. In general, good correlations were obtained between the micro-mechanical and adhesion properties of the considered asphalt binders measured using the AFM and their chemical properties obtained from the GPC and FTIR tests.Part 2 was presented in chapter 4. Similar to the aging study, AFM was used to evaluate the micro-mechanical properties of the interfacial blending zone between RAP and virgin asphalt binders. Three virgin asphalt binders with different performance grades (PG 58-28, PG 64-28, and PG 64-22) and two sources of RAP binder were used in this study to evaluate the effects of the different RAP and virgin asphalt binder properties on the stiffness and adhesive properties of the blending zone between these binders. A new procedure was developed to simulate the interaction between the RAP and virgin asphalt binders that occurs in the drum in an asphalt plant. The AFM tests indicated that the blending occurred between RAP and virgin binder for all 6 tested RAP-virgin asphalt binder combinations. The reduced modulus for the blending zone depended generally on the virgin binder grade and the RAP source. The highest stiffness was achieved from the combination of RAP and PG 64-22 while the lowest stiffness was obtained from the combination of RAP and PG 58-28. The bonding energy results indicate that adhesive properties of the blending zone were adversely affected by the presence of RAP within the zone. However, the adhesive properties of the blending zone were significantly better than those for the RAP binders. The variation in the blending zone between both RAP binders and PG 58-28/ PG 64-28 indicated that the blending zone might not be homogenous. Further analysis of the concentration of RAP binder within blending zone revealed dependence on RAP stiffness characteristics while the adhesive properties of the blending zone were primarily controlled by the virgin binder properties.

Let $(Z,d,\mu)$ be a compact, connected, Ahlfors $Q$-regular metric space with $Q>1$. Using a hyperbolic filling of $Z$, we define the notions of the $p$-capacity between certain subsets of $Z$ and of the weak covering $p$-capacity of path families $\Gamma$ in $Z$. We show comparability results and quasisymmetric invariance. We reprove a result due to Tyson on the geometric quasiconformality of quasisymmetric maps between compact, connected, Ahlfors $Q$-regular metric spaces. Under certain conditions, we identify the Ahlfors regular conformal dimension of $Z$ with critical exponents arising from weak capacity. Following an approach by Mario Bonk and Bruce Kleiner, we prove a necessary and sufficient condition involving weak capacity for an Ahlfors regular metric space that is topologically $\mathbb{S}^2$ to be quasisymmetrically equivalent to $\mathbb{S}^2$.

Critical size bone defects are large defects that do not spontaneously heal over time and result in permanent non-union of the bone. These abnormalities can result from traumas, surgeries, and diseases. Surgical methods used to treat these defects include natural (autografts and allografts) and synthetic bone grafts. Autografts draw advantages from diminished immune response but suffer from complications during implantation as well as pain and cosmetic defects during removal. Allograft complications include rejection and infection. Infection can be minimized by sterile processing techniques, but this frequently leads to diminished mechanical properties post-processing. As a consequence of these limitations, synthetic bone grafts have drawn significant interest. Synthetic bone grafts include biodegradable polymers, metals, and ceramics. For example, poly(caprolactone) (PCL) and poly(L-lactic acid) (PLLA) are biodegradable polymers used widely for medical applications. These materials can be molded into any desired shape; however, they are unsuitable for load-bearing applications as a consequence of their poor mechanical properties post-processing. Bioceramics, such as amorphous calcium phosphate (ACP), benefit from their osteoconductive behavior but are too brittle for load-bearing applications. Combining the biodegradable polymers with bioceramics have shown increased mechanical properties in the composites. The goal of this study was to examine the resulting mechanical properties of combining an L-phenylalanine-based poly(ester urea) (PEU) with various amount of ACP. We hypothesize that adding ACP to the polymer will lead to enhanced mechanical properties compared to the pure polymer.

Volume overload (VO) induced heart failure results from an increase in blood volume (preload) to the heart. The heart responds to increases in hemodynamic load through compensative remodeling. VO has a distinct pattern of remodeling compared to pressure overload induced heart failure, which results in fibrosis. VO results in a net decrease in extracellular matrix (ECM). This loss of ECM contributes to the progression of the disease due to the loss of structural integrity. Since cardiac fibroblasts (CFs) are the main cells responsible for maintaining ECM in the heart, we characterized the in vitro phenotype of CFs isolated from a rat VO model, aortocaval fistula (ACF). Compared to sham operated animals, ACF fibroblasts displayed a phenotype that we described as “hypofibrotic”. ACF CFs secreted relatively less collagen and profibrotic molecules, such as a-smooth muscle actin (aSMA) and connective tissue growth factor (CTGF). Interestingly, ACFs produce approximately twice as much transforming growth factor-ß1 (TGF-ß), a key profibrotic stimulus, as their sham counterparts. However, there were no changes in the canonical TGF-ß pathway that could account for the hypofibrotic phenotype observed in ACF fibroblasts. Since others have shown that the cytoskeleton and the Rho/ROCK pathway play a role in fibroblast phenotype, we characterized the actin cytoskeleton in sham and ACF fibroblasts. We found that ACF CFs have significantly less F-actin than sham CFs. We were able to show that it is possible the actin cytoskeleton might account for phenotypic differences in CFs by chemically altering the amounts of F-actin and G-actin. When the cells were treated with a ROCK inhibitor, which allows F-actin to depolymerize into G-actin, CFs displayed a more hypofibrotic phenotype. Conversely, enhancement of F-actin with jasplakinolide treatment forced the CFs to have a profibrotic phenotype. Numerous studies have linked substrate modulus with effects on the cytoskeleton. Stiff substrates tend to increase cytoskeletal organization and increase F-actin resulting in stress fiber formation in vitro. We wondered if changes in tissue modulus may account for differences in observed phenotype. To know if changes in tissue modulus account for changes in CF phenotype, we first characterized the tissue stiffness changes. We used biaxial tensile testing, which yields a direct measure of tissue modulus, an intrinsic property of the material. Here we show that ACF rats have approximately half the tissue modulus compared to control rats. Since increased stiffness is positively correlated with CF changes towards a more profibrotic phenotype, we postulated that decreased substrate stiffness may lead to a more hypofibrotic phenotype. Specifically, we hypothesized that sham CFs on softer substrates would have a more hypo-fibrotic phenotype; conversely, CFs from ACF would behave more like normal cells on a higher stiffness. Although the phenotype of sham CFs was shifted to a more hypofibrotic direction on soft substrates, ACF fibroblasts had many indications of a dampened response to stiffness reminiscent of the effect known as “mechanical memory” described by others 1,2.

Nondestructive Evaluation (NDE) is an effective way for determining material properties. More specifically, ultrasonic waves along with visual measurements from a microscope can be used to systematically determine the elastic modulus of single ply composites that are subject to an altered manufacturing process. In this approach, the magnitude of specific ultrasonic wave velocities is applied through Chirstoffel's equations to determine the necessary five elastic constants that describe the elastic modulus of transversely isotropic composites. On the other hand, fiber misalignment measurements are taken through via digital microscopy to satisfy a statistical approach for the determination of the same elastic modulus. The Paper Physics Approach (PPA) and Laminate Analogy Approach (LAA) are utilized to predict the elastic modulus of unidirectional carbon fiber samples. A two parameter Weibull distribution is expected to satisfy the probability density of the fiber length and fiber orientation variation which will then be implemented into the Halpin-Tsai equations that will determine the elastic modulus. In terms of results, the mean fiber length from the visual approach is approximately 250 μm and the mean fiber misalignment is just over 3°. The elastic constants range from 7 GPa to 9 GPa depending on the approach. Destructive mechanical testing led to an average elastic modulus value of 8.49 GPa.

The mechanically-measured Young’s modulus of metals is consistently lower than the physically measured one, particularly after plastic straining. Furthermore, the nominally elastic loading and unloading behavior is not linear; it shows significant curvature and hysteresis. While many reports of this so-called “modulus effect” have appeared, the consistency of the behavior among grades of steel, or within a single grade produced by alternate methods and suppliers, is unknown. That is, there is little information on whether it is necessary for manufacturers to measure and control the mechanical modulus for every coil of steel in order to guarantee accurate simulations, consistent forming, and reliable in-service behavior. In order to address these issues, 12 steels (4 diverse grades: IF, HSLA, DP600, DP980; 3 producers per grade) were subjected to high-precision modulus measurements using mechanical testing, resonant frequency damping analysis, and ultrasonic pulse-echo techniques. All of these measurements show remarkable consistency among not only suppliers but also among grades. The primary determinant of hysteresis/curvature of the stress-strain response was found to be the nominal flow stress of the alloy. Other variations of overall mechanical modulus are minor compared with hysteresis/curvature. The following conclusions were reached: 1) there is no significant difference among suppliers of a single steel grade, 2) there is very little difference between grades of steel, except for that attributable to differing strengths, 3) mechanical unloading and reloading after pre-strain are similar, 4) cyclic loading and unloading cycles have no accumulated effect except through a minor change of flow stress, and 5) the initial loading or unloading modulus is very similar to the physical modulus, but the mechanically measured slope degrades very rapidly as loading or unloading proceeds, and plateaus at even small strain (

Dynamic modulus (E*) test has gained substantial acceptance in recent years for evaluating Hot Mix Asphalt (HMA) rutting and fatigue cracking performances. Indeed, the recently developed Mechanistic Empirical Pavement Design Guide (MEPDG) uses E* data for stress and strain calculation, and E*-based models for prediction fatigue and rutting performances of a HMA pavement. Unfortunately, neither HMA mix design method nor the MEPDG uses E* value to evaluate moisture damage characteristics of HMA pavements. In fact, moisture damage is a very complex problem, and there exists no models for inclusion in the MEPDG for predicting moisture damage performance of HMA pavements. Rather, moisture damage performance of HMA is evaluated during the mix design state using the AASHTO T 283 test. According to AASHTO T 283 method, indirect tensile strength ratio of wet to dry samples is used as an indicator of moisture damage performance of a HMA mix. The AASHTO T 283 is a simple method, but it is not very reliable. In some cases, it gives false negative and positive values about the moisture damage characteristic of an HMA sample. To this end, this study attempts to study moisture damage in Asphalt Concrete (AC) sample by determining the loss in dynamic modulus (E*) value based on continuum damage mechanics. The loss in E* is evaluated by calculating the ratio of wet E* to dry E* (DMR). In this study, E* testing is performed on five different asphalt mixtures. Three of the asphalt mixtures are plant produced Superpave mixes, and the other two are laboratory prepared HMA mix. The plant produced mixes include SP-II mix with asphalt binders Performance Grade (PG) PG 64-22, SP-III mix with PG 70-22, and SP-IV mix with PG 70-22. The laboratory mixes are SP-III mix with PG 64-22, and SP-II with binder PG 70-22. The E* test is conducted at five temperatures (-10, 4, 21, 37, 54 °C) and six frequencies (25, 10, 5, 1, 0.5, 0.1 Hz). The resulting E* data are used to generate time-temperature mastercurves. Also, the laboratory E* data is fitted to several models such as the viscosity (\u03b7) -based Witczak model, the dynamic shear modulus (G*) -based Witczak models, and the Hirsch model. However, all models are found to underpredict the laboratory E* values. Therefore, the \u03b7-based Witczak model is modified to improve E* prediction accuracy in this study and E* ratios are used for evaluating moisture damage in AC. As mentioned above, the most common test method for evaluating moisture damage susceptibility of HMA mix is the AASHTO T 283. According to the AASHTO T 283, a dry asphalt concrete sample is vacuum saturated and then subjected to one cycle of freezing and thawing. However, one cycle of freeze-thaw does not simulate moisture condition resulting from repeated pore water pressure buildup and scouring cycles that occur when vehicle tires pass over a saturated pavement. Recently, Moisture Induced Sensitivity Tester (MIST) equipment can apply repeated pore pressure cycles inside an AC sample in the laboratory. Therefore, MIST device is employed in this study to cause damage in AC samples. Moisture damage resulting from MIST conditioning is then evaluated using the Dynamic Modulus Ratio (DMR) of wet to dry samples. MIST conditioning is performed at three different pressures (40, 55, 70 psi), three temperatures (40, 50, 60 \xbaC) and three different numbers of cycles (3500, 7000 and 10,500). MIST conditioning is found to decrease the E* value of asphalt concrete indicating the presence of moisture damage. The average DMR is observed to decrease from 1.0 to 0.85, 0.46 and 0.56 for MIST conditioning at 3500, 7000 and 10500 cycles, respectively. When the MIST conditioning temperature is increased to 40, 50 and 60 \xbaC, the average DMR decreases from 1.0 to 0.90, 0.82 and 0.76, respectively. The DMR at 276, 376 and 483 kPa MIST conditioning pressures are determined to be 1.0, 0.91 and 0.72, respectively. Therefore, moisture damage increases with an increase in number of cycles, temperatures and pressures. However, it is shown that temperature affects moisture damage less significantly than the number of cycles and pressures in a MIST device. Therefore, number of traffic and magnitude of traffic loading should be considered carefully to design moisture damage free pavements.'

Punched membranes as fine pore diffuser material have become available in the last ten years because they are more efficient. Heat, moisture and UV light are three main factors causing degradation of plastics and rubber membranes. In order to better understand the impact of sunlight on membranes, a series of outdoor tests were conducted on actual membranes. Results of this experiment showed that heat decreased hardness values; existence of UV light resulted in decreased modulus values; heat only had very slight effect on thickness and weight. To prevent membranes from degradation, it is suggested that they are stored in water as deep as at least 24 cm and they are covered with UV filter, especially when the weather is hot and UV light is strong.

Multifunctional composite materials were developed to enhance the dielectric properties of an epoxy polymer by reinforcing it with ceramic barium titanate (BaTiO3) particles. Potential applications for this material include structural capacitors that can be used to replace discrete capacitors, currently used for power conditioning or electrical discharge in military systems, giving rise to a reduction in system mass, and cost. BaTiO3 particles with an average size of 100 nm (cubic) and 200 nm (tetragonal) were used as the filler and EPONTM Resin 862 (diglycidyl ether of bisphenol F) was used as the matrix. Two parametric studies were performed using Taguchi's Design of Experiments methods. The parameters varied were the volume fraction (Vf) of the particles; the particle size (crystal structure); and the use of dielectrophoretic assembly (DPA), by applying an electric field during the composite curing process. For Study 1, DPA was applied in the plane of the composite mold, and for Study 2, DPA was applied through the plane of the composite mold. The failure stress, FS; Young's Modulus, E; dielectric constant,εr, and dielectric loss, tanδ, were characterized and a signal-to-noise ratio analysis was conducted to determine the optimum combination of manufacturing parameters. For Study 1, to maximize FS, the optimum combination was 25% Vf, 100 nm (cubic) particles, and no DPA. To maximize E and &epsilonr the optimum combination was 50% Vf, 200 nm (tetragonal) particles, and no DPA. To minimize tanδ, the optimum combination was 50% Vf, 100 nm (cubic), and with DPA applied. For study 2, to maximize FS, and to minimize tanδ, the optimum combination was 25% Vf, 100 nm (cubic) particles, and no DPA. To maximize E and &epsilonr, the optimum combination of parameters was 50% Vf, 200 nm (tetragonal) particles, and no DPA. For both studies, the optimum combination of parameters was determined through statistical methods, and supported by the physics which govern the material properties. A numerical simulation calculated the magnitude of the electric field inside the composite, and the charge on the surface of the material. The simulation and experimental results were in good agreement.

Traditional field seismic measurements have been performed for more than 50 years to determine the small-strain shear and constrained moduli of geotechnical materials under existing conditions. Field measurements to characterize the nonlinear response of the constrained modulus have received essentially no attention in the engineering community. This study was undertaken to characterize the in-situ response of the linear and nonlinear constrained moduli in one testing method. In this dissertation, a field method is presented which uses large shakers to impart vertical sinusoidal excitations directly above an embedded sensor array. This methodology essentially performs parametric studies on the constrained moduli of geotechnical materials in-situ over a wide range of axial strains. In this study, embedded sensor arrays at two different locations were constructed. A staged loading sequence was used to determine the constrained compression wave velocities between sensors in the linear, i.e. small-strain, and nonlinear strain ranges. Constrained moduli were determined using the mass density of the soil and the constrained compression wave velocities. The axial strains generated between sensors were estimated using a displacement-based method. At both sensor arrays, the method successfully measured in the field: (1) the variation of the small-strain constrained compression wave velocity with increasing confining pressure and (2) the effect of axial strain on the constrained moduli of soil in various states of stress. The field measurements indicate that, at lower levels of confining pressure, the constrained modulus increases slightly with increasing axial strain, but then decreases with increasing axial strain. However, in other cases, the constrained modulus increased with increasing axial strain and showed little or no tendency to reach a "peak" value. The nonlinear stress-strain behavior of the constrained modulus is quite complex and appears to be a function of several factors, including the amount of overconsolidation and cementation in the soil and the locations of the sensors in the array. Therefore, while the results of this study indicate that the proposed field method can be successfully used to investigate the constrained modulus, more work is required in this area to fully quantify the response of the constrained modulus in the nonlinear strain range.

Silicone hydrogels are receiving considerable interest due to their important biomedical application areas such as contact lenses and wound dressings. The applications of such materials are usually in the hydrated state, as hydrogels. However, manufacturing and molding processes are mostly carried out in the organically solvated state, as organogels. This thesis investigates the effects of some of the manufacturing parameters such as curing time and thermal processing on thermal, mechanical, viscoelastic and adhesive/cohesive fracture properties of silicone semi-interpenetrating polymer network organogels. Curing time may affect the extent of reaction and the crosslink density of a gel network. In order to investigate the effect of this parameter, materials were photo-cured for different times within the range of 150s to 1800s. Gel content, uniaxial tensile, dynamic mechanical, adhesive fracture and cohesive fracture properties were obtained as a function of photo-curing time and results were correlated with each other in order to have a better understanding of the effects on the material properties. Additionally, thermal properties of the gels were studied in detail. Crystallization and melting behavior of one of the solvents in the organogel were investigated by differential scanning calorimetry and thermal optical microscopy. Correlation between the thermal properties of the solvent and the gel network structure was shown. Dynamic mechanical analysis experiments were performed to investigate the effect of solvent crystallization on the mechanical properties. Finally, the effect of thermal processing parameters such as the heating  rate and the minimum cooling temperatures on the crystallization and the thermo-mechanical properties were studied.

Abdominal injuries caused by motor vehicle crashes have a high severity, since they have an elevated potential to be life threatening. Yet to date, injuries in the abdominal region are poorly understood. The objective of this research is to perform a computational study to investigate the influence of the human liver’s anatomical geometry, nonlinearity, viscoelasticity, and anisotropy on the macroscopic response of a liver exposed to known loading conditions at high strain rates. The influence that the fibrous Glisson’s capsule has on the liver’s overall behavior is also investigated, since it is neglected by many current FEM analyses. An axisymmetric Finite Element Model (FEM) was constructed to emulate a uni-directional compression loading condition of an isolated human liver exposed to a wide range of strain rates, simulating the experimental setup used by Sparks et al. (2007). The FEM material properties were iteratively determined in order to effectively capture the experimental force-displacement data. A secondary validation was achieved from comparing the FEM pressure contours to experimental localized pressure measurements. Stress contour plots compiled by the FEMs were also inspected to qualitatively examine the difference in FEM trends. Results indicate that the viscoelastic behavior of the liver does not significantly contribute to the overall response of the liver at high strain rates, the results from using a hyperelastic material model only exhibits minor differences from using a linear elastic material model, and the trends exhibited in an anatomical FEM are also present and captured by an axisymmetric FEM.

When designing pavements, there are three fundamental external design parameters to evaluate (1) the characteristics of the subgrade upon which the pavement is placed, (2) the applied loads, and (3) the environment. The subgrade layer, upon which the pavement is constructed, will have a large impact on structural design. The study was based on extensive laboratory work to characterize cohesive subgrade materials. Permeability of the subgrade was obtained using a flexible wall permeameter, which simulates the actual field conditions. The factors affecting permeability were also discussed. Strength parameters were determined utilizing the static load triaxial apparatus. The Consolidated-Undrained Triaxial Compression Test and Unconfined Compression Test were performed. Resilient modulus testing was conducted using a repeated load triaxial system at different confining pressures employing AASHTO T294-92I. A new testing procedure, stage loading, was used to test the permanent deformation of subgrade materials at different stress levels and load repetitions; this technique allows researchers to explore the effect of stress history on the accumulation of plastic deformation besides saving time, effort, and test specimens. Hydraulic conductivity results showed a practically impermeable subgrade layer. From the measured data of the consolidation test, the pressure-void ratio relationship was plotted and used in determining the compression index, recompression index and maximum past pressure of the soil. In addition, the coefficients of consolidation were obtained. Mohr circles at failure and Mohr failure envelopes were drawn for the total and effective stress data obtained from the CU tests, from which shear strength parameters were determined. On the other hand, Mohr circles at failure were drawn for the unconfined compression test that indicated the cohesive subgrade soils to vary between very stiff and hard consistency. Furthermore, isotropic elasticity analysis was carried out. It was found that soil moduli increase as the confining pressure increases according to the elastic theory. Resilient modulus results showed a slight increase in resilient modulus value with an increase in confining pressure. The permanent deformation results showed a constant increasing rate of plastic strain at higher stress levels. The results obtained will be added to the ODOT database to help engineers in characterizing the cohesive subgrade materials.

The thermoelectric properties of bismuth telluride based thermoelectric (TE) materials are well-characterized, but comparatively little has been published on the thermomechanical properties. In this paper, dynamic mechanical analysis (DMA) and differential scanning calorimetry data for bismuth telluride based TE materials is presented. The TE materials' tan delta values, indicative of viscoelastic energy dissipation modes, approached that of glassy or crystalline polymers, were greater than ten times the tan delta of structural metals, and reflected the anisotropic nature of TE materials. DMA thermal scans showed changes in mechanical properties versus temperature with clear hysteresis effects. These results showed that the application of DMA techniques are useful for evaluation of thermophysical and thermomechanical properties of these TE materials.

The objective of this study is to characterize the mechanical and adhesive properties of polyvinylbutyral and determine the effect of plasticizer content and photoageing on these properties. This data would be used to understand how the performance of laminated safety glass is related to the choice of adhesive interlayer. Samples of PVB plasticized with 0 to 40% butyl benzyl phthalate by weight were analyzed using a single strain rate tensile test, dynamic mechanical thermal analysis and a 1350 peel test. Two regimes of behavior were identified. PVB with low plasticizer contents, up to 10%, acts as a glassy polymer at room temperature. At higher plasticizer concentrations, greater than 20%, the material becomes elastomeric, with increased ductility and decreased moduli. The adhesive strength of each of the formulations was similar if compared at their respective glass transition temperatures. At room temperature, the heavily plasticized formulations had good adhesive strength whereas the less plasticized formulations readily debonded from the glass. These results suggest that PVB plasticized with between 20 and 40% plasticizer content is highly suitable as an interlayer material. UV radiation exposure was used to simulate the effect of sunlight on PVB. Forty micron thick samples were irradiated for up to 1000 hours of exposure time and analyzed using FTIR spectroscopy. It was determined that photo degradation had occurred in the form of a breakdown of the acetal ring structure in the vinyl butyral function. Similar treatment of 0.75 mm thick samples produced no major degradation in the mechanical or adhesive properties of the material. This is an unexpected result that conflicts with the obvious degradation discovered during FTIR spectroscopic testing. This is most likely due to the increased thickness of the mechanical samples and corresponding lo\ver UV dosage per polymer chain.

The classical Riemann Mapping Theorem has many discrete analogues. One of these, the Finite Riemann Mapping Theorem of Cannon, Floyd, Parry, and others, describes finite tilings of quadrilaterals and annuli. It relates to several combinatorial moduli, similar in nature to the classical modulus. The first chapter surveys some of these discrete analogues. The next chapter considers appropriate extensions to infinite tilings of half-open quadrilaterals and annuli. In this chapter we prove some results about combinatorial moduli for such tilings. The final chapter considers triangulations of open topological disks. It has been shown that one can classify such triangulations as either parabolic or hyperbolic, depending on whether an associated combinatorial modulus is infinite or finite. We obtain a criterion for parabolicity in terms of the degrees of vertices that lie within a specified distance of a given base vertex.