Directionally solidified (DS) nickel-base superalloys are used in high temperature gas turbine engines because of their high yield strength at extreme temperatures and strong low cycle fatigue (LCF) and creep resistance. Costly inspecting, servicing, and replacing of damaged components has precipitated much interest in developing models to better predict service life. Turbine blade life modeling is complicated by the presence of notches, dwells, high temperatures and temperature gradients, and highly anisotropic material behavior. This work seeks to develop approaches for predicting the life of hot sections of gas turbines blade material CM247LC DS subjected to LCF, dwells, and stress concentrations while taking into consideration orientation and notch effects. Experiments were conducted on an axial servo-hydraulic MTS® testing machine. High temperature LCF tests were performed on smooth and notched round-bar specimens in both longitudinal and transverse orientations with and without dwells. Experimental results were used to develop and validate an analytical life prediction model. An analytical model based on a multiaxial Neuber approach predicts the local stress-strain response at a notch and other geometric stress concentrations. This approach captures anisotropy through a multiaxial generalization of the Ramberg-Osgood relation using a Hill's type criterion. The elastic notch response is determined using an anisotropic elastic finite element analysis (FEA) of the notch. The limitations of the simpler analytical life-modeling method are discussed in light of FEA using an anisotropic elastic-crystal viscoplastic material model. This life-modeling method provides a quick alternative to time demanding elastic-plastic FEA allowing engineers more design iterations to improve reliability and service life.

Cette étude concerne l’élaboration et la caractérisation de membranes composites de piles àcombustible PEMFC. Ces nouveaux composites associent un ionomère commercial leNafion® à des charges acides minérales qui sont des acides phosphoantimoniques. Descharges mono et triacides, H1 et H3, ont été utilisées à des taux massiques compris entre 5 et20%. Outre, leur contribution à la conduction protonique et à l’hydratation, les 2 chargesaméliorent sensiblement, même à faible taux, la tenue thermomécanique des membranes. Cerenforcement permet de diminuer l’épaisseur des membranes et donc la chute ohmique. Lestests en pile, réalisés dans une large gamme d’hydratation des gaz et de température,démontrent l’apport incontestable des charges, les membranes composites étant sensiblementplus performantes dès lors que la température de fonctionnement atteint ou dépasse 80°C. / This study deals with the elaboration and characterization of composite membranes intendedto be used in PEMFC. These new composites combine a commercial ionomer, Nafion®, withinorganic acidic fillers that are phosphatoantimonic acids. Mono and triacid fillers, H1 and H3, have been used at 5 to 20wt% contents. Besides, their contribution to proton conductionand hydration, both fillers markedly improve, even at low content, the thermomechanicalperformances of the membranes. This reinforcement allows the thickness and, therefore, theohmic drop to be decreased. The MEA tests, performed in a wide range of gas humidificationand temperature, indisputably demonstrate the benefic effect of the fillers; Compositemembranes performing significantly better as soon as the operating temperature reaches orexceed 80°C.

Orientador: Francisco das Chagas Marques / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-05T00:47:21Z (GMT). No. of bitstreams: 1 ChampiFarfan_AnaMelva_D.pdf: 65229004 bytes, checksum: 98d3b8d6ecf9c395993d20730f0013f7 (MD5) Previous issue date: 2004 / Resumo: Nesta tese estudamos a influência da incorporação de nitrogênio nas propriedades termomecânicas e estruturais em matrizes de carbono amorfo hidrogenado (a-C:H) e não hidrogenado (a-C). Duas técnicas de deposição foram utilizadas para o crescimento dos filmes. Os filmes hidrogenados foram preparados utilizando um sistema de glow discharge e as não hidrogenadas foram preparadas por IBAD. Um estudo preliminar foi feito em função do bias e a pressão do metano CH4, com o objetivo de escolher duas condições para a incorporação de nitrogênio. Deste primeiro estudo foi observado um aumento do coeficiente de dilatação térnica dos filmes de a-C:H com o aumento das ligações sp2. A partir desta série, uma segunda série de amostras com matriz tipo diamond-like e graphite-like de a-C:H foram estudadas, nas quais observamos que independente da matriz, a incorporação de nitrogênio produz um aumento no coeficiente de dilatação térnica (CTE) de até 9x10-6 C-1 para cerca de 6% de nitrogênio, próximo do valor do CTE do grafite (8x10-6C-1). A influência do nitrogênio no carbono amorfo aumenta a geração das hibridizações sp e sp2, o qual facilita a fornação de clusters grafíticos dentro dos filmes de a-C:H:Nx. O empilhamento dos clusters e a influência destes no CTE dos filmes são amplamente discutidos, para o qual técnicas espectroscópicas como Raman, infravermelho e perda de energia dos elétrons (EELS) são estudadas nesta tese. Por outro lado, para ter uma visão mais clara da influência do N, amostras com matrizes não hidrogenadas de a-C foram preparadas pela técnica de IBAD. Com nesta técnica temos filmes de a-C:Nx com altas concentrações de nitrogênio (até ~30%). Foi observado que mesmo com altas concentrações de N, o CTE dos filmes de a-C:Nx não consegue atingir valores acima de 5xl0-6 C-1. Este fato, faz pensar que o hidrogênio cumpre um papel muito importante no ernpilhamento dos clusters grafíticos. A partir das medidas feitas pela técnica de TIB (o qual foi desenvolvido em nosso laboratório e utilizado para medir o stress, CTE e módulo biaxial dos filmes) e a Nanoindentação obtivemos separadamente o módulo de Young (E) e a razão de Poisson (v), nas três séries de amostras estudadas. Os resultados são discutidos como uma função dos tipos de hibridizações dos filmes de a-C:H, a-C:H:Nx e a-C:Nx / Abstract: In this work, we studied thenno mechanical and structural properties of hydrogenated amorphous carbon (a-C: H), hydrogenated carbon nitride (a-C:H:Nx) and carbon nitride (a-C:Nx) thin films. Two techniques were used to prepare the samples: glow discharge for depositing hydrogenated amorphous carbon (a-C:H) and carbon nitride (a-C:H:Nx) and ion beam assisting deposition (IBAD) for unhydrogenated amorphous carbon nitride (a-C:Nx) films. The curvature of the film/substrate composites was measured using the thermally induced bending (TIB) technique in order to determine the stress of the films. By varying the temperature and using films deposited in several different substrates one was able to obtain the coefficient of thermal expansion (CTE) and the biaxial modulus (E/(l-v)) of the films. Complementarily to this technique, we perfonned nanohardness measurements, which also allows to obtaining the elastic constant (E/(1-v2)) as well. Using both techniques, TIB and nanohardness, we determined, for the first time, separately the Young's modulus (E) and the Poisson's ratio (v) of a-C:H, a-C:H:Nx and a-C:Nx. These thermomechanical properties were investigated as a function of sp2-bond, or graphite's cluster, concentrations, using the following techniques: EELS, infrared spectroscopy, visible and ultraviolet Raman spectroscopy. The influence of the incorporation of nitrogen in the hydrogenated and unhydrogenated matrixes is discussed. We observed that the CTE of a-C:H depends strongly on the concentration of Sp2 sites approaching the value for graphite as the concentration tends to 100 %. The nitrogen incorporation increases the cluster formation in matrixes, inducing a substantial increase of the CTE of the fi1ms. On the other hand, in the matrix free of hydrogen it was observed that the CTE is not strongly influenced by the nitrogen concentration. These observations indicate that hydrogen plays an important role on the value of the CTE in amorphous carbon nitrogen films / Doutorado / Física da Matéria Condensada / Doutor em Ciências

Les mousses minérales sont des matériaux alvéolaires utilisables en isolation thermique répartie. L’objectif de ces travaux de recherche est de développer, à partir d’une suspension très concentrée de liants hydrauliques, des mousses légères présentant de bonnes performances mécaniques et thermiques. L’introduction de tensioactif est nécessaire à la formation des mousses minérales. Six molécules tensioactives sont sélectionnées dans cette étude. Leurs capacités à réduire la tension de surface et à stabiliser une mousse aqueuse sont évaluées. Deux groupes de tensioactifs sont distingués sur la base de différents critères : tension de surface, CMC, stabilité de la mousse. Les suspensions minérales concentrées sont des fluides à seuil. L’étude du comportement de bulles formées dans de tels fluides est réalisée à l’aide d’un fluide à seuil modèle transparent, le Carbopol®, et d’un système d’injection à pression contrôlée. Le seuil de mise en écoulement affecte les conditions de formation, de croissance, de stabilité et d’évolution de la forme des bulles en modifiant la distribution des pressions au voisinage de la bulle. L’étude permet de proposer une équation de Laplace modifiée prenant en compte l’influence de la sphéricité et du seuil de cisaillement. L’introduction du tensioactif affecte les conditions de contact entre bulles et permet de contrôler le risque de coalescence. En cas de rupture de membrane, la présence du seuil de cisaillement conduit à une géométrie particulière des bulles coalescées. Les liants minéraux choisis sont un sulfate de calcium anhydre particulièrement réactif, un ciment Portland et un ciment prompt. La formulation des suspensions découle d’un critère de fluidité. La pâte fraîche est caractérisée par un seuil de cisaillement faible. Sa masse volumique apparente dépend de la nature et du dosage en tensioactif. Les mousses minérales sont générées à partir d’une composition identique. Deux méthodes de moussage traditionnelles : malaxage simple et mousse préformée et une méthode alternative : la méthode dissociée, sont exploitées. Les meilleures performances thermomécaniques des mousses durcies sont obtenues avec la méthode dissociée, méthode spécifique au laboratoire et peu énergivore. Un groupe de tensioactifs permet d’obtenir des mousses peu denses satisfaisant simultanément aux critères de performances thermomécaniques fixés. Pour ces tensioactifs, un dosage caractéristique est identifié permettant une optimisation des performances mécaniques. Des visualisations réalisées au MEB révèlent des modifications sensibles de la structure cristalline fonction du tensioactif employé et de son dosage. Les structures les plus fines et homogènes sont les plus résistantes. Les performances des mousses et leur structure porale sont donc liées. Pour analyser quantitativement la structure porale, les distributions alvéolaires surfaciques sont construites puis comparées aux distributions alvéolaires volumiques obtenues par tomographie. Une méthode analytique de passage 2D/3D est créée en s’appuyant sur les principes de la stéréologie. Un coefficient de correction est proposé pour tenir compte de la représentativité de la surface étudiée. La maîtrise de toutes les étapes de fabrication des mousses minérales ainsi que la compréhension des phénomènes physiques intervenant tout au long de la production d’une mousse (de la suspension minérale jusqu’à la mousse durcie) permettent d’obtenir des produits satisfaisant les objectifs fixés : légèreté, isolation et caractère porteur. / Mineral foams are cellular materials usable as thermal insulation solution. The purpose of these PhD researches is to develop lightweight foams with good thermal and mechanical performances realized from highly concentrated mineral suspension. Surfactant addition is required for foaming. Six surfactants molecules are selected. Their abilities to reduce surface tension and to stabilize aqueous foam are evaluated. Two surfactants groups are detected based on different criteria: surface tension, CMC and aqueous foam stability. Concentrated mineral suspensions are yield stress fluids. The study of bubbles behavior in such fluids is performed with a transparent yield stress fluid, Carbopol® and an injection device with controlled pressure. Yield stress impacts bubbles creation, growth, stability and shape by changing local pressure distribution in the fluid nearby bubble. The study proposes a revised Laplace law depending on yield stress and bubble sphericity. Contact conditions between bubbles are influenced by surfactant addition allowing to control coalescence phenomena. In case of inter-bubbles membrane breakage, presence of yield stress leads to particular geometry of the coalesced bubbles. Mineral binders selected are a highly reactive anhydrous calcium sulfate, ordinary Portland and prompt cements. Mineral suspension formulations arise from expected fluidity criterion. Fresh paste is characterized by a low yield stress. Its bulk density depends on surfactant nature and content. Mineral foams are created with same composition. Two traditional foaming methods: mix-foaming and pre-foaming and an alternative one, the dissociated method are employed. Best thermo-mechanical performances are achieved with the dissociated method, a specific method of the laboratory. A surfactant group leads to lightweight foams which simultaneously fulfills both thermal and mechanical targeted objectives. For these surfactants a characteristic content is found leading to optimized mechanical performances. Visualizations performed with SEM reveal sensitive crystalline structure modifications depending on surfactant nature and content. Thinner and more homogeneous structures are associated with the best mechanical performances which demonstrates the existing link between the porous structure and mineral foams mechanical performances. To quantitatively evaluate porous structure, surface bubble-size distributions are built and then compared to volume bubble-size distributions obtained by tomography analysis. An analytic method linking 2D and 3D distributions is created based on stereology principles. A correction coefficient is proposed to take into account the analyzed representative surface. By controlling all production steps and associated physical phenomena during mineral foams production (from mineral suspension to solid foams), products satisfying all targeted objectives are realized: lightness, insulation and load-bearing ability.

The aviation industry aims to reduce its environmental impact through innovation and research. The usage of composite materials for multiple primary structures represents one such measure. Several alternative fuels were approved and used along with the Federal Aviation Administration (FAA). These alternative fuels are produced from wastes and biomasses. Some alternative fuels were initially only approved as drop-in fuels, meaning they must be blended with conventional fuels to operate. Fuel tanks are usually embedded into the wing structure, which is mainly made of composite materials. These composites tend to absorb fluids it encounters through their matrix phase. The absorption behavior of conventional fuels by composite materials is well documented, while alternative fuels, blended or pure, are not as widely reported. The effects of four alternative fuel blends on aerospace-grade composites were investigated and compared with the conventional fuel Jet A. No significant differences were found in weight gain. The thermomechanical properties changes were also studied, with no difference between the alternative fuel blends and the conventional fuel. Additionally, model fluids with similar chemical structures as alternative fuels were used. The uptake of these model fluids was studied cyclically and compared with Jet A and one aromatic fluid. Small differences were seen in the weight gain results, primarily due to the type of model fluids used. Also, the thermomechanical properties showed no differences between these model fluids, Jet A and the pure aromatic fluid. This means that the slight differences in weight gain did not affect the changes in properties. From the results obtained, the alternative fuels blended, and the model fluids showed no differences in effects on the thermomechanical properties versus Jet A. This implies that similar effects are expected from either type of fluids used. Finite element analysis was used to model fluid’s diffusion in composite materials using different material parameters. The parameters were fiber packing, arrangement and permeability. Each parameters impacted the equilibrium uptake and the diffusion rate differently.

In this thesis, the thermomechanical approach with internal variables has been thoroughly analyzed. This approach is based on the combination of thermodynamic principles and continuum mechanics. Therefore it reflects the physical essence of constitutive behavior of materials. Based on this approach, a one-dimensional constitutive model for the two-way shape memory effect and a one-dimensional constitutive model for piezoceramics have been developed, respectively. In modeling the two-way shape memory effect, a residual stress σ_re is introduced as a controlling parameter for the two-way shape memory effect. A further refinement of the transformation kinetics expression for two-way shape memory is derived. It is demonstrated that the material parameters required by this model can be calculated or measured using a standard materials testing apparatus. A numerical study is conducted and the effectiveness of this model is verified. In the constitutive modeling of piezoceramics, a new internal state variable is introduced to relate the macroscopic behavior of a piezoceramic with its micro-properties. A phenomenological formulation of polarization reversal is proposed, and then a fully-coupled thermo-electro-mechanical model is developed. It is shown that the theory developed can describe the electromechanical behavior of piezoceramics well. / Master of Science

Le projet de la thèse a consisté au développement et à l’évaluation des performances d’une mousse syntactique phénolique pour la réalisation d’un système sandwich multicouche (cœur/peau en matériau composite). Il permet d’assurer la protection thermique, mécanique et au feu en particulier contre l’impact d’un feu torche. Un feu torche peut survenir sur un site pétrochimique suite à l’inflammation d’une fuite de fluides inflammables sous pression pouvant être très dévastateur par son effet abrasif et le flux convectif et radiatif intense. Le travail s’est essentiellement axé sur l’étude de l’efficacité de la mousse syntactique phénolique à partir d’une analyse de la relation microstructure-propriété. Les exigences de mise en œuvre ont imposé une maîtrise de la formulation par une bonne compréhension de la réactivité de la résine, notamment par rapport aux différentes transformations physiques (gélification, vitrification) qui ont lieu pendant le processus de réticulation. Il s’agit alors d’optimiser le dosage des différents composés actifs et additifs vis-à-vis des contraintes de mise en œuvre afin de parvenir à des propriétés optimales du matériau final. L’efficacité de ce dernier dans les conditions normales d’utilisation a été déterminée par une phase d’expérimentation complète sur ses propriétés mécaniques, thermiques et thermomécaniques. Des tests au feu ont permis d’étudier son comportement au feu afin de vérifier ses propriétés protectrices sous l’impact d’une flamme issue d’un feu torche. Enfin, un essai instrumenté capable de reproduire en condition réelle une fuite de gaz de propane à haute pression a été mis au point pour évaluer la performance au feu torche d’un prototype industriel complet. En parallèle, un modèle numérique simplifié a été proposé afin de simuler l’impact d’un tel feu. / This work consisted in the development and the evaluation of a phenolic syntactic foam performance for the production of a multilayer sandwich system (core/skin in composite material). It ensures thermal, mechanical and fire protection, in particular against the impact of a jet fire. A jet fire can occur on a petrochemical site resulting from the combustion of a fuel continuously released under pressure. It can be very devastating for its abrasive effect and intense convective and radiative flux. The work focuses mainly on the study of the effectiveness of the phenolic syntactic foam through the analysis of the relationship microstructure-propriety. The manufacturing process requirements imposed to control the elaboration via a good understanding of the reactivity of the resin, especially in relation to various physical transformations (gelation, vitrification) that take place during the curing mechanisms. That involves optimizing the proportions of the various active compounds and additives depending on the working conditions in order to achieve optimal properties of the final material. The effectiveness of this final material under normal conditions of use was determined by a complete testing phase on its mechanical, thermal and thermomechanical properties. Fire tests were also conducted to investigate the material burning behavior to ensure its protective properties under a jet flame impact. Finally, a large-scale instrumented test, reproducing in real conditions a propane gas leak at high pressure, was developed to evaluate the resistance to a jet fire of a complete industrial prototype. In parallel, a simplified numerical model was also proposed to simulate the impact of such a fire.

Este trabalho comparou as propriedades termomecânicas de concretos refratários comerciais para aplicação em conjunto de porta ventos de alto-forno. Dez composições diferentes de concretos refratários à base de alta alumina, alta mulita e alta andaluzita foram caracterizados. Para identificar e quantificar a composição e a microestrutura dos refratários foram utilizadas técnicas de espectroscopia de fluorescência de raios X (FRX), difratometria de raios X (DRX) qualitativa e quantitativa, microscopia eletrônica de varredura com análise de energia dispersiva de raios X (MEV-EDS), massa especifica aparente e porosidade aparente (MEA/Pa). A caracterização termomecânica foi realizada com ensaios de flexão três pontos, propagação de trinca para cálculo da energia de fratura com entalhe chevron, módulo de elasticidade dinâmico, coeficiente de Poisson e o cálculo do coeficiente de expansão térmica utilizando a regra das misturas. Para compreender o dano causado pelo choque térmico ensaios cíclicos de choque térmico foram feitos seguidos de analises de módulo de elasticidade por técnica de excitação por impulso seguido do módulo de ruptura por flexão três-pontos. Os parâmetros de resistência ao choque térmico (R e R´) e os parâmetros de resistência ao dano por choque térmico (R´´´, R´´´´ e Rst) foram calculados. Os resultados de ciclagem térmica e os parâmetros de resistência ao choque térmico mostram que para os concretos analisados, todos os materiais tem nucleação de trincas para temperaturas iguais ou superiores a 1100°C. Os parâmetros de resistência ao dano por choque térmico corroboram com os resultados das análises de MEV. O concreto D1 apresentou a melhor combinação de resistência ao dano por choque térmico e baixa condutividade térmica, propriedades requeridas para a aplicação em conjunto de porta ventos de alto-forno. Por fim é mostrado que as análises de ciclagem térmica devem ser analisadas cuidadosamente com foco na aplicação dos concretos e no desempenho da microestrutura do material, visto que as propriedades termomecânicas são caracterizadas por indiretamente por diferentes técnicas e portanto vários parâmetros precisam ser considerados. O concreto D1 apresentou boa resistência ao dano por choque térmico e baixa condutividade térmica e portanto possui o melhor desempenho para a aplicação em conjunto de porta ventos. / This work compares the thermomechanical properties of commercial castable refractories for blast furnace blowpipe application. Ten different compositions of commercial castable refractories with compositions of high alumina, high mullite, and high andalusite were characterized. In order to identify and quantify the composition and microstructure of the castables, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning eléctron microscopy with energy dispersive spectrum (SEM-EDS), bulk density, and apparent porosity were used. The thermomechanical characterization was performed through threepoint flexural strength, work of fracture through crack propagation in notched samples, dynamic elasticity modulus, Poisson ratio, and the calculation of the thermal expansion coefficient using the mix law. Cyclic thermal shocks at 1100°C were realized in order to characterize the materials under thermal shock damage environment followed by elasticity modulus, modulus of rupture, and SEM analysis. The parameters for thermal shock resistance (R e R´) and the parameters for thermal shock damage resistance (R´´´, R´´´´ e Rst) were calculated. The thermal shock cycling tests and the thermal shock resistance correlated and showed that all castables had crack nucleation after a thermal shock of 1100°C or higher. The thermal shock damage parameters and the SEM analysis correlate. Castable D1 showed high resistance to thermal shock damage and lower thermal conductivity, which are required properties for the blast-furnace blowpipe application. Thermal shock cycling tests performed on castables should therefore be examined not only through mechanical testing, but also through microstructure analysis. Castable D1 showed high thermal shock damage resistance and lower value of thermal conductivity; therefore, it is the best castable for blast furnace blowpipe application among the samples tested.

A comprehensive study of heat transfer and pressure drop of refrigerant R410A during condensation and supercritical cooling at near-critical pressures was conducted. Investigations were carried out at five nominal pressures: 0.8, 0.9, 1.0, 1.1 and 1.2xpcrit. The refrigerant was tested in commercially available horizontal smooth tubes of 6.2 and 9.4 mm I.D. Heat transfer coefficients were measured using a thermal amplification technique that measures heat duty accurately while also providing refrigerant heat transfer coefficients with low uncertainties. For condensation tests, local heat transfer coefficients and pressure drops were measured for the mass flux range 200 G 800 kg/m2-s in small quality increments over entire vapor-liquid region. For supercritical tests, local heat transfer coefficients and pressure drops were measured for the same mass flux range as in the condensation tests for temperatures ranging from 30 110oC. Condensation heat transfer coefficients and pressure drops increased with quality and mass flux. The effect of reduced pressure on heat transfer is not very significant, while this effect is more pronounced on the pressure gradient. The flow regime transition criteria of Coleman and Garimella (2003) were used to initially designate the prevailing flow regimes for a given combination of mass flux and quality. The condensation data collected in the present study were primarily in the wavy and annular flow regimes. During supercritical cooling, the sharp variations in thermophysical properties in the vicinity of the critical temperature resulted in sharp peaks in the heat transfer coefficients and sudden jumps in the pressure drop. Based on the characteristics of the specific work of thermal expansion (contraction), the data from the supercritical tests were grouped into three regimes: liquid-like, pseudo-critical transition and gas-like regimes. Flow regime-based heat transfer and pressure drop models were developed for both condensation and supercritical cooling. For condensation, the overall heat transfer model predicts 98% of the data within 15% while the overall pressure drop model predicts 87% of the data within 15%. For supercritical cooling, the heat transfer model predicted 88% of the data within 25% while the pressure gradient model predicts 84% of the data within 25%.

Shock waves create a unique environment of high pressure, high temperature and high strain-rates. It has been observed that chemical reactions that occur in this regime are exothermic and can lead to the synthesis of new materials that are not possible under other conditions. The exothermic reaction is used in the development of binary energetic materials. These materials are of significant interest to the energetic materials community because of its capability of releasing high heat content during a chemical reaction and the relative insensitivity of these types of energetic materials. Synthesis of these energetic materials, at nano grain sizes with structural reinforcements, provides an opportunity to develop a dual functional material with both strength and energetic characteristics. Shock-induced chemical reactions pose challenges in experiment and instrumentation. This thesis is addressed to the theoretical development of constitutive models of shock-induced chemical reactions in energetic composites, formulated in the framework of non-equilibrium thermodynamics and mixture theories, in a continuum scale. Transition state-based chemical reaction models are introduced and incorporated with the conservation equations that can be used to calculate and simulate the shock-induced reaction process. The energy that should be supplied to reach the transition state has been theoretically modeled by considering both the pore collapse mechanism and the plastic flow with increasing yield stress behind the shock wave. A non-equilibrium thermodynamics framework and the associated evolution equations are introduced to account for time delays that are observed in the experiments of shock-induced or assisted chemical reactions. An appropriate representation of the particle size effects is introduced by modifying the initial energy state of the reactants. Numerical results are presented for shock-induced reactions of mixtures of Al, Fe2O3 and Ni, Al with epoxy as the binder. The theoretical model, in the continuum scale, requires parameters that should be experimentally determined. The experimental characterization has many challenges in measurement and development of nano instrumentation. An alternate approach to determine these parameters is through ab-initio calculations. Thus, this thesis has initiated ab-initio molecular dynamics studies of shock-induced chemical reactions. Specifically, the case of thermal initiation of chemical reactions in aluminum and nickel is considered.