Laminated glass is comprised of multiple glass plates coupled together in a sandwich construction through the use of a polymorphous interlayer that acts as a bonding agent between the glass plates. Laminated glass offers several advantages over monolithic glass including the ability to resist post fracture collapse, improved sound insulation, lower ultraviolent light trans-mission, and improved thermal insulation. Because the stiffness of the interlayer is often many orders of magnitude less than that of the glass, plane sections prior to loading do not remain plane throughout the laminate?s thickness after load is applied. The behavior of laminated glass is controlled by the stiffness of the interlayer. This behavior rules out the use of classical theoretical formulations for thin plates. In such cases, it is necessary to use specially formulated equations or finite element analyses to evaluate the performance of laminated glass. Previous attempts have been made to develop procedures to quantify the interlayer stiffness for use in laminated glass design. However, there is no widely accepted technique that can be referenced for use. It is known that the interlayer stiffness is a function of both temperature and load duration. The primary objective of this thesis is to formalize a standard procedure to estimate the in situ interlayer shear modulus through the use of nondestructive testing. Physical experiments were carried out on simply supported laminated glass beams subject to three point loading in a temperature controlled environmental testing chamber. Strains and temperatures were recorded as a function of time. These data were used in combination with results from finite element analyses to quantify the variation of the interlayer stiffness as a function of temperature and load duration for a given laminated glass beam. This procedure was applied to three common types of interlayer materials: freshly man-factured polyvinyl butyral (PVB), over a decade old PVB, and freshly manufactured SentryGlas Plus (SGP). Results from these efforts provide specific design guidance for laminated glass that incorporates these interlayer materials. Further, the procedure was applied to various data presented in open literature by previous researchers. In addition, a standardized procedure to estimate interlayer stiffness is provided for the development of additional interlayer properties as required.

No description available.

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)

In this dissertation, a research effort aimed at development and implementation of a direct field test method to evaluate the linear and nonlinear shear modulus of soil is presented. The field method utilizes a surface footing that is dynamically loaded horizontally. The test procedure involves applying static and dynamic loads to the surface footing and measuring the soil response beneath the loaded area using embedded geophones. A wide range in dynamic loads under a constant static load permits measurements of linear and nonlinear shear wave propagation from which shear moduli and associated shearing strains are evaluated. Shear wave velocities in the linear and nonlinear strain ranges are calculated from time delays in waveforms monitored by geophone pairs. Shear moduli are then obtained using the shear wave velocities and the mass density of a soil. Shear strains are determined using particle displacements calculated from particle velocities measured at the geophones by assuming a linear variation between geophone pairs. The field test method was validated by conducting an initial field experiment at sandy site in Austin, Texas. Then, field experiments were performed on cemented alluvium, a complex, hard-to-sample material. Three separate locations at Yucca Mountain, Nevada were tested. The tests successfully measured: (1) the effect of confining pressure on shear and compression moduli in the linear strain range and (2) the effect of strain on shear moduli at various states of stress in the field. The field measurements were first compared with empirical relationships for uncemented gravel. This comparison showed that the alluvium was clearly cemented. The field measurements were then compared to other independent measurements including laboratory resonant column tests and field seismic tests using the spectral-analysis-of-surface-waves method. The results from the field tests were generally in good agreement with the other independent test results, indicating that the proposed method has the ability to directly evaluate complex material like cemented alluvium in the field. / text

The fact that many of the giant hydrocarbon reservoirs, such as the Ghawar field in Saudi Arabia and the Grosmont formation in Alberta, are formed from carbonates make these rocks important research topics. Compressional and shear wave velocities (at 1 MHz) and the quasi-static strains of thirty seven carbonate rock samples were measured as functions of saturating fluid and confining pressure. Furthermore, P- and S-wave velocities of the saturated samples were measured at constant differential pressure of 15 MPa. The quasi-static strains of the samples under jacketed and unjacketed conditions were also simultaneously acquired. The lithology, mineralogy, porosity and pore type and size distribution of each sample were obtained using a combination of thinsection and scanning electron microscopy, helium porosimetry and mercury intrusion porosimetry. Due to the lack of closing microcracks and compliant pores in low porosity samples, the travel times show slight changes with the confining pressure. Whereas the high porosity samples show remarkable reduction of travel time with the increase of confining pressure in both P- and S-wave. The samples show no changes in travel time with increasing confining pressure under constant differential pressure, and this behavior is taken to be representative of full saturation of the sample and hence used as a measure of quality control. The comparisons of Biot, Gassmann, squirt-Biot and squirt-Gassmann model predictions with the measured water saturated velocities show that the squirt mechanism is not active on all the studied samples. Biot mechanism is likely to be the principle dispersion mechanism in these samples. For S-wave velocities, Gassmanns model consistently over-predict the saturated at low pressure and closely fit the measured velocities at high pressure, whereas, Biot model over-predicts the saturated velocities in most of the studied samples. The strains over the horizontal axis are higher than the vertical axis suggesting that the majority of the compliant pores and crack-like pores are oriented almost in direction parallel to the length of the sample. The static bulk modulus is always lower than dynamic one for all measured samples. The measured grain bulk modulus is reasonably close to the bulk modulus of the constituent mineral. / Geophysics

Inverse spectral techniques are developed in this dissertation for recovering the shear modulus and residual stress of soft tissues. Shear modulus is one of several quantities for measuring the stiffness of a material, and hence estimating it accurately is an important factor in tissue characterization. Residual stress is a stress that can exist in a body in the absence of externally applied loads, and beneficial for biological growth and remodeling. It is a challenge to recover the two quantities in soft tissues both theoretically and experimentally. The current inverse spectral techniques recover the two unknowns invasively, and are theoretically based on a novel use of the intravascular ultrasound technology (IVUS) by obtaining several natural frequencies of the vessel wall material. As the IVUS is interrogating inside the artery, it produces small amplitude, high frequency time harmonic vibrations superimposed on the quasistatic deformation of the blood pressure pre-stressed and residually stressed artery. The arterial wall is idealized as a nonlinear isotropic cylindrical hyperelastic body for computational convenience. A boundary value problem is formulated for the response of the arterial wall within a specific class of quasistatic deformations reflexive of the response due to imposed blood pressures. Subsequently, a boundary value problem is developed from intravascular ultrasound interrogation generating small amplitude, high frequency time harmonic vibrations superimposed on the quasistatic finite deformations via an asymptotic construction of the solutions. This leads to a system of second order ordinary Sturm-Liouville problems (SLP) with the natural eigenfrequencies from IVUS implementation as eigenvalues of the SLP. They are then employed to reconstruct the shear modulus and residual stress in a nonlinear approach by inverse spectral techniques. The shear modulus is recovered by a multidimensional secant method (MSM). The MSM avoids computing the Jacobian matrix of the equations and is shown to be convenient for manipulation. Residual stress is recovered via an optimization approach (OA) instead of the traditional equation-solving method. The OA increases the robustness of the algorithms by overdetermination of the problem, and comprehensive tests are performed to guarantee the accuracy of the solution. Numerical examples are displayed to show the viability of these techniques.

No description available.

Within the vestibular system are otolith organs, both the utricle and saccule. The primary function of these organs is to transduce linear head accelerations and static head tilts into afferent signals that are sent to the central nervous system for the utilization of image fixation, muscle posture control, and the coordination of musculoskeletal movement in dynamic body motion. The utricle of the red ear slider turtle was studied in this dissertation. The turtle's utricle is composed of several layers. The base layer contains a set of neural receptor cells, called hair cells, and supporting cells. The three layers above the base layer compose the utricle's otoconial membrane (OM) and are: 1.) a saccharide gelatinous layer, 2.) a column filament layer, and 3.) a calcite and aragonite otoconial crystal layer. The primary goal of this research was to study the dynamic response of the turtle's OM to a variety of natural inertial stimuli in order to characterize its inherent mechanical properties of natural frequency ("n), damping ("), and shear modulus (G). The medial-lateral (ML) and anterior-posterior (AP) anatomical axes parameters were measured for the utricle. The ML axis median with 95% confidence intervals was found to be "n = 374 (353, 396) Hz, " = 0.50 (0.47, 0.53), and G = 9.42 (8.36, 10.49) Pa. The AP axis median with 95% confidence intervals was found to be "n = 409 (390, 430) Hz, " = 0.53 (0.48, 0.57), and G = 11.31 (10.21, 12.41). Nonlinearites were not found to occur in the OM for the tested inertial stimuli and no significant difference was found between the mechanical properties for the ML and AP axes. Additionally, this research presents the initial steps to form a novel bio-inspired accelerometer based on the morphology of the utricle. The primary transducer element for this possible otolith organ inspired accelerometer design is a droplet interface bilayer (DIB). A DIB is a lipid bilayer that is formed when the interface of two aqueous droplets, that contain free-floating lipids, are joined. The aqueous droplets are suspended in a nonpolar environment (oil) and the oil/water interface forms a lipid monolayer. This research developed and used an experimental test setup to characterize the mechanoelectrical characteristics of a micron-sized DIB. This information, along with examples in the text, could be used to further design the aforementioned accelerometer. / Ph. D.

Esta dissertação apresenta o método de análise espectral de ondas superficiais (SASW) para a obtenção das variações do módulo cisalhante (Gmáx) com a profundidade, no domínio das deformações muito pequenas (abaixo de 0,001%). O SASW é um método sísmico in situ, não destrutivo, baseado na geração e detecção de ondas Rayleigh e na natureza dispersiva desta onda. Pela aplicação de um impacto na superfície do solo e detecção da onda em vários pontos, através de dois receptores, é construída uma curva de dispersão (velocidade de fase versus comprimento de onda). Esta curva de dispersão é, então, invertida. A inversão é um processo analítico para a reconstrução do perfil de velocidade de onda de cisalhamento (VS), partindo-se da curva de dispersão experimental de campo. O módulo de cisalhamento máximo de cada camada é facilmente obtido a partir do perfil de VS. No conteúdo teórico da dissertação discutem-se propriedades dinâmicas dos solos e descrevem-se as equações que dominam a propagação das ondas elásticas, tanto em meios homogêneos como em meios estratificados. A metodologia desenvolvida para a obtenção das curvas de dispersão, através da realização de ensaios SASW, apresenta os resultados obtidos em ensaios realizados na Cidade Universitária em São Paulo, sendo esses resultados comparados com estimativas feitas a partir de correlações baseadas em ensaios SPT existentes. Essas comparações permitem concluir que a metodologia SASW é uma boa alternativa para a determinação do perfil de rigidez (Gmáx) do solo, concordando com o nível de deformação envolvido nos ensaios. São desenvolvidos estudos de sensibilidade do método para verificar a influência na mudança dos parâmetros assumidos (peso específico, coeficiente de Poisson e espessuras das camadas) no processo de redução de dados (inversão) sobre o perfil final de VS, concluindo-se que o parâmetro que apresenta maior influência é o coeficiente de Poisson. / This dissertation presents the spectral-analysis-of-surface-waves (SASW) method as a tool for obtaining the variations in the modulus shear (Gmax) with depth in the field of very small strains (below 0,001%). The SASW method is a nondestructive in situ seismic method, based on the generation and measurement of Rayleigh wave and on its dispersive characteristic nature. Throughout the implementation of an impact on the soil surface and the detection of the wave at various points by two receptors a dispersion curve is constructed (phase velocity versus wave-length). This dispersion curve is then inverted. Inversion is an analytical process for reconstructing the shear wave velocity profile from the experimental field. The shear modulus of each layer is readily obtained from the shear wave velocity profile. The theoretical content of the dissertation presents dynamic properties of the soils and is described in the equations that dominate the propagation of elastic waves, both in homogeneous media and in stratified media. The methodology developed to obtain the dispersion curves through the implementation of SASW test is defined, and results from tests carried out at the University Campus in São Paulo are presented and compared with values obtained from correlations based on SPT tests. These comparisons indicate that the SASW method is a good alternative to determine the profile of stiffness (Gmax) of the soil, agreeing with the level of deformation involved in the tests. Studies on the methods sensitivity are developed to verify the influence on the changing of the parameters given (natural unit weight, Poisson coefficient and thickness of layers) in reduction of data (inversion) on the final profile of VS. The conclusion is that the Poisson coefficient is the parameter with greater influence.