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abstract: Asphalt binder is a complex viscoelastic hydrocarbon, whose performance depends upon interaction between its physical and chemical properties, both of which are equally important to the successful understanding of the material. Researchers have proposed various models linking linear viscoelastic (LVE) and microstructural parameters. However, none of these parameters provide insight into the relationship in the non- linear viscoelastic NLVE domain. The main goals of this dissertation are two fold. The first goal is to utilize the technique of Laser Desorption Mass Spectroscopy (LDMS) to relate the molecular structure of asphalt binders to its viscoelastic properties. The second goal of the study is to utilize different NLVE characterization tools and analysis procedures to get a clear understanding of the NLVE behavior of the asphalt binders. The goals of the study are divided into four objectives; 1) Performing the LDMS test on asphalt binder to develop at the molecular weight distributions for different asphalts, 2) Characterizing LVE properties of Arizona asphalt binders, 3) Development of relationship between molecular structure and linear viscoelasticity, 4) Understanding NLVE behavior of asphalt binders through three different characterization methods and analysis techniques. In this research effort, a promising physico-chemical relationship is developed between number average molecular weight and width of relaxation spectrum by utilizing the data from LVE characterization and the molecular weight distribution from LDMS. The relationship states that as the molecular weight of asphalt binders increase, they require more time to relax the developed stresses. Also, NLVE characterization was carried out at intermediate and high temperatures using three different tests, time sweep fatigue test, repeated stress/strain sweep test and Multiple Stress Creep and Recovery (MSCR) test. For the intermediate temperature fatigue tests, damage characterization was conducted by applying the S-VECD model and it was found that aged binders possess greater fatigue resistance than unaged binders. Using the high temperature LAOS tests, distortion was observed in the stress-strain relationships and the data was analyzed using a Fourier transform based tool called MITlaos, which deconvolves stress strain data into harmonic constituents and aids in identification of non-linearity by detecting higher order harmonics. Using the peak intensities observed at higher harmonic orders, non-linearity was quantified through a parameter termed as “Q”, which in future applications can be used to relate to asphalt chemical parameters. Finally, the last NLVE characterization carried out was the MSCR test, where the focus was on the scrutiny of the Jnrdiff parameter. It was found that Jnrdiff is not a capable parameter to represent the stress-sensitivity of asphalt binders. The developed alternative parameter Jnrslope does a better job of not only being a representative parameter of stress sensitivity but also for temperature sensitivity. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2018

The prediction of linear viscoelasticity (LVE) of a polymer melts from the knowledge of their structure has received tremendous attention in recent years. Quite accurate quantitative predictions are obtained for linear polymers, including inverse predictions of molecular weight distributions from knowledge of rheological response. The situation for branched polymers is much more complicated for at least two reasons. First, because of the incredible variety of architectures that can be, and are actually, made in the lab or by industry. Second, because branched polymers are characterised by very broad distributions of relaxation times, which are very dependent on details of the architecture. The main objective of this work is to propose a model suitable for predicting LVE of arbitrary mixtures of (a)symmetric stars and linear molecules, where the interrelation of relaxation processes (as reptation, tube length fluctuations or constraint release process) cannot be predicted a priori. We validate it on a large set of experimental data taken from the literature, from our own experiments or from co-workers. Next, we use it to detect long chain branching (LCB) in sparsely branched polycarbonate samples. This characterization technique, based on the analysis of the relaxation moduli, is compared to solution characterization. A similar work is performed for polyethylene samples, on which we compare our method to classical methods based on the measurement of their intrinsic viscosity or on the analysis of their activation energies spectrum. The success of our model in describing the relaxation of an already broad range of polymer structures gives some hope for understanding the dynamics of more complex systems. Indeed, its structure allows us to easily extend it to H or comb polymers and then, to proceed to polymers always closer to the industrial polymers.

The objective of this study was to develop a model to predict the viscoelastic material functions of a vinyl ester (VE) polymer (Derakane 441-400, Ashland Co.,) with variations in its material properties. Short-term tensile creep/creep recovery experiments were conducted at two stress levels and at four temperatures below the glass transition temperature of the VE polymer, with 10 replicates for each test configuration. Experimental strains in both the longitudinal and transverse directions were measured using a digital image correlation technique. The measured creep strain versus time responses were subsequently used to determine the creep compliances using the generalized viscoelastic constitutive equation with a Prony series representation. The variation in the creep compliances of Derakane 441-400 was described by formulating the probability density functions (PDFs) and the corresponding cumulative distribution functions (CDFs) of the creep compliances using the two-parameter Weibull and log-normal distributions. The maximum likelihood estimation technique was used to obtain the Weibull shape and its scale parameters and the log-normal location and its scale parameters. The goodness-ofit of the distributions was determined by performing Kolmogorov-Smirnov (K-S) hypothesis tests. Based on the K-S test results, the Weibull distribution is a better representation of the creep compliances of Derakane 441-400 when compared to the log-normal distribution. Additionally, the Weibull scale and shape parameters of the creep compliance distributions were shown to be time and temperature dependent. Therefore, two-dimensional quadratic Lagrange interpolation functions were used to characterize the Weibull parameters to obtain the PDFs and subsequently the CDFs of the creep compliances for the complete design temperature range during steady state creep. At each test temperature, creep compliance curves were obtained for CDF values of 0.05, 0.50 and 0.95 and compared with the experimentally obtained lowest, mean and highest creep compliances, respectively. The predicted creep compliances of Derakane 441-400 in the design space are in good agreement with the experimental data.

Mechanistic-Empirical  (M-E)  pavement  design  procedures  are  composed  of  a  reliable  response model to estimate the state of stress in the pavement and distress models in order to predict the different types of pavement distresses due to the prevailing traffic and environmental conditions. One of the main objectives of this study was to develop a response model based on multilayer elastic  theory   (MLET)  with  improved  computational  performance  by   optimizing  the   time consuming parts of the MLET processes. A comprehensive comparison of the developed program with  two  widely  used  programs  demonstrated  excellent  agreement  and  improved  computational performance.  Moreover,  the  program  was  extended  to  incorporate  the  viscoelastic  behaviour  of bituminous materials through elastic-viscoelastic correspondence principle. A procedure based on collocation of linear viscoelastic (LVE) solutions at selected key time durations was also proposed that improved the computational performance for LVE analysis of stationary and moving loads. A comparison  of  the  LVE  responses  with  measurements  from  accelerated  pavement  testing  (APT) revealed a good agreement. Furthermore the developed response model was employed to evaluate permanent deformation models  for  bound  and  unbound  granular  materials  (UGMs)  using  full  scale  APTs.  The  M-E Pavement  Design  Guide  (MEPDG)  model  for  UGMs  and  two  relatively  new  models  were evaluated  to  model  the  permanent  deformation  in  UGMs.  Moreover,  for  bound  materials,  the simplified  form  of  the  MEPDG  model  for  bituminous  bound  layers  was  also  evaluated.  The measured  and  predicted  permanent  deformations  were  in  general  in  good  agreement,  with  only small discrepancies between the models. Finally, as heavy traffic loading is one of the main factors affecting the performance of flexible pavement, three types of characterizations for heavy traffic axle load spectrum for M-E analysis and design of pavement structures were evaluated. The study recommended an improved approach that enhanced the accuracy and computational performance. / <p>QC 20140512</p>

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Ce travail présente une méthode mixte expérimentale-numérique traitant des mesures mécaniques réalisées sur structures pour l’identification de propriétés matériau viscoélastiques linéaires. Les caractéristiques de ces matériaux sont complexes et dépendent de la fréquence et nous cherchons à les identifier par une approche directe et non paramétrique. Pour cela, deux méthodes d’identification adaptées au traitement des mesures de champs de réponses en fréquences sont présentées. Cellesci utilisent les données fréquentielles, sans analyse modale expérimentale. Les champs expérimentaux sont obtenus par vibromètrie laser et les champs numérique par la méthode des éléments finis. Nous utilisons un modèle volumique adapté à l’étude des structures minces et épaisses pour l’analyse numérique. Les applications se basent sur des plaques simples ou multicouches. Les résultats sont corrélés avec des mesures DMA et des identifications à partir de données modales identifiées. / This work deals with a mixed experimental numerical method for linear viscoelastic material parameter identification. These parameters are complex and frequency dependent. Identication is performed using a direct and non parametric approach. In this goal, two identification methods adapted to frequency response fields measurements treatment are presented. These datas are durectly exploited, without any experimental modal analysis. Experimental fields are obtained using a vibrometer and numerical ones with finite element method. A brick element dedicated to thin/thick structures analysis is employed. Appications are performed using simple plates or sandwich plates. Results are also compared to DMA measurements and identified modal parameters.

Ce mémoire a pour objectif l’étude de la réalisation de nanocomposites polyétherétherkétone (PEEK) /nanotubes de carbone (NTC) par mélange en voie fondue. Il s’est articulé autour de trois axes principaux, qui sont : l’impact du pourcentage de nanotubes de carbone sur les propriétés rhéologiques et électriques, l’influence du procédé d’extrusion bivis sur l’état de dispersion, ainsi que la réalisation du composite hybride renforcé en fibres longues de carbone. Un modèle rhéologique (loi de Carreau-Yasuda à seuil) et un modèle électrique (loi puissance), ont été utilisés pour caractériser quantitativement le seuil de percolation ainsi que le degré de dispersion. L’état de dispersion par le procédé d’extrusion dépend des conditions opératoires (vitesse de rotation N et débit d’alimentation Q). Les relations entre le procédé et l’état de dispersion ont également été étudiées à l’aide de la distribution des temps de séjour, et des énergies mécaniques spécifiques. Enfin, le comportement mécanique et électrique des composites hybrides a été exploré. L’étude des temps de dégradation, de relaxation à permis d’établir une fenêtre de mise en oeuvre du composite hybride. / The aim of this dissertation is the study of the formation of polyetherethercetone (PEEK) / carbon nanotubes (NTC) nanocomposites via melt compounding. It focused on three major part which are the fallowing: the effect of CNT content on rheological and electrical properties, the effect of twin screw extrusion parameters on CNT dispersion, and the manufacture of hybrid composite reinforced with carbon fibers as well. A Carreau-Yasuda rheological model with a yield stress and power law model are used to characterize quantitatively the rheological and electrical percolation threshold and the state of dispersion. The state of dispersion is depending on the operating conditions (screw speed N and feed rate Q). The relationships between processing conditions and the state of dispersion are also investigated, using the residence time distribution and the specific mechanical energy. Finally, the mechanical and the electrical behavior of the hybrid composite have been studied. The degradation time and relaxation time studies drew a process window for the hybrid composite.

Non-invasive and fast flow measurement techniques have had increasing importance for the last decades. Scientists are looking for such quick techniques to be able to monitor real velocities without disturbing flow itself. Ultrasound Doppler velocimetry (UDV) being one of such techniques promising with advantages of getting simultaneous velocity measurements from several points and of applicability for opaque liquids as well. UDV is a technique which is still being developed for new applications and analysis of complex flows. In this study effect of sinusoidal oscillating, turbulent (random) and viscoelastic fluid motions on UDV signals were investigated theoretically and experimentally. Obtained mathematical relations for random and viscoelastic motions were utilized to get statistics of flow and distribution of relaxation spectrum, respectively. Analytical analysis and numerical simulation of sinusoidal oscillating flow depicted that there is a critical value for the ratio of oscillation amplitude to oscillation frequency for a specified set of measurement parameters of UDV. Above this critical value UDV is not successful to determine mean flow velocity. Mathematical relations between velocity probability density function (PDF) &ndash / velocity auto correlation function (ACF) and UDV signal spectrum were obtained in the analysis v of flow with random velocity. Comparison of velocity ACFs from direct velocity measurements and from raw in-phase (I) and quadrature (Q) signals through derived relation, revealed that time resolution of UDV technique is not enough for getting a good velocity ACF and thus turbulence spectrum. Using I and Q signals rather than measured velocities to get velocity ACF, increased the time resolution in the order of number of pulses used for getting one velocity value (Nprn). Velocity PDF obtained from UDV spectrum was compared with the one obtained from measured velocities with the assumption of Gaussian PDF. Both velocity PDFs were consistent. Also some parameters of pipe turbulence from literature were compared with the presented findings from velocity ACF obtained from I and Q signals through derived relation. Results showed good compatibility. In the last part of the study, complex viscosity of a linear viscoelastic fluid mathematically related to spectrum of UDV for a pipe flow with small-amplitude oscillating pressure field. Generalized Maxwell model was employed to express complex viscosity terms. Zero frequency (mean flow) component of UDV spectrum was used to obtain an equation for relaxation viscosities of generalized Maxwell model. Results have revealed that UDV technique can also be used to probe some of viscoelastic material functions. In conclusion, UDV is relatively new but a promising technique for the measurement and analysis of complex flows in a non-invasive manner.

La prédiction du comportement à long terme des matériaux cimentaires est un enjeu majeur pour contribuer à l'étude de la durabilité des structures précontraintes. Le présent travail porte sur l'utilisation de la méthode de l'inclusion équivalente, approche d'homogénéisation multi-échelle simplifiée, pour la prédiction du fluage dans ces matériaux. Le fluage est modélisé par la viscoélasticité linéaire sans vieillissement. La méthode de l'inclusion équivalente permet de contourner certaines difficultés et limitations que présentent les approches classiques. Pour les matériaux cimentaires, fortement hétérogènes, les approches multiéchelles classiques sont ou bien numériquement lourdes et très complexes à mettre en œuvre, ou bien pas suffisamment détaillées pour prendre en compte les spécificités d'une microstructure. La méthode de l'inclusion équivalente présente un juste-milieu et permet de calculer des microstructures simplifiées de type matrice-inclusions et de fournir des estimations ou des bornes sur le comportement homogénéisé. Sous sa forme variationnelle, la méthode de l'inclusion équivalente n'a jusqu'alors été mise en œuvre que pour des inclusions de forme sphérique. Le présent travail propose d'étendre cette méthode à des inclusions de forme ellipsoïdale dont la variation de l'élancement permet de modéliser de nouveaux éléments asphériques tels que les fissures, les fibres et les cristaux de portlandite. Cette complexification de la géométrie a un impact sur le temps de calcul, qui est amplifié dans le cadre du fluage. Le second volet du travail porte alors sur l'extension de la méthode de l'inclusion équivalente à la viscoélasticité linéaire sans vieillissement par l'intermédiaire de la transformée de Laplace-Carson. Une méthodologie efficace (tant du point de vue de la précision que de celui du temps de calcul) est finalement proposée pour effectuer l'inversion numérique de cette transformée / The prediction of long-term behaviour of cementitious materials is a major concern which contributs to the study of the durability of prestressed structures. This work focuses on the use of the equivalent inclusion method, simplified multi-scale homogenization approach, for the prediction of creep in these materials. Creep is modelled by the non-ageing linear viscoelasticity. The equivalent inclusion method overcomes certain difficulties and limitations posed by conventional approaches. For cementitious materials (highly heterogeneous), conventional multi-scale approaches are, either digitally heavy and complex to implement, or not sufficiently detailed to take into account the specificities of a microstructure. The equivalent inclusion method presents a middle way and allows the calculation of simplified matrix-inclusion type microstructures and to provide estimates or bounds on the homogenized behaviour.Under its variational form, the equivalent inclusion method has, up to now, been implemented only for spherical inclusions. This work proposes to extend this method to ellipsoidal inclusions whose variation of slenderness allows the modelling of new aspheric elements such as cracks, fibers and portlandite crystals. Such enrichment of the geometry has an impact on the computation time, that is amplified in the context of creep. The second aspect of the work then applies to the extension of the equivalent inclusion method to the non-ageing linear viscoelasticity by means of the Laplace-Carson transform. An effective methodology (both from the viewpoint of precision and calculation time) is finally proposed to perform the numerical inversion of this transform