Dissertations / Theses on the topic 'Building materials – Acoustic properties'

Ces travaux de thèse s'inscrivent dans le cadre du projet PNEEB/Typha (Programme National d’Efficacité Energétique des Bâtiments) pour la valorisation d’un roseau invasif, le Typha Australis, comme isolant thermique pour améliorer l’efficacité énergétique des bâtiments au Sénégal. Un agromatériau à base de terre argileuse et de granulats de Typha Australis est élaboré afin d’évaluer l’influence de la morphologie et de la quantité de fibres sur le comportement du matériau. Pour cela, deux modes de production de granulats sont choisis : Une découpe longitudinale et une découpe transversale. Les propriétés physiques sont étudiées (taux de porosité, densité apparente et absolue, microstructure) et la tenue mécanique est déterminée. L'absorption acoustique est également évaluée, de même que les propriétés hygrothermiques et le comportement au feu. Les résultats montrent que la morphologie du granulat de Typha affecte le comportement en flexion, cisaillement et l’absorption acoustique. Son impact sur le comportement de compression est moins prononcé. Une portion plus importante de fibres de Typha réduit la résistance mécanique. En revanche, les performances hygrothermiques sont accrues en raison de la porosité de ces granulats. La fraction transversale de Typha permet d’améliorer la résistance thermique et d’accroitre les phénomènes de transfert de la vapeur d'eau. Cette étude a également permis de montrer que ces matériaux sont d'excellents régulateurs d'humidité. Enfin, les tests au feu révèlent qu’il s’agit de combustibles ininflammables en raison de la présence d'argile. L’influence de la morphologie des granulats n’est pas relevée
This work is a part of PNEEB/Typha project (National Program for Energy Efficiency of Buildings) for the valorisation of an invasive reed, the Typha Australis, as a thermal insulator to improve the energy efficiency of buildings in Senegal. An agromaterial based on clay soil and Typha Australis is elaborated in order to evaluate the influence of the amount and fibres morphology on the material behaviour. For this, two production mode of granulates are chosen: longitudinal and transversal cut. Physical properties are studied (porosity, apparent, and absolute density, microstructure) and mechanical strength is determined. Sound absorption is also evaluated, as well as hygrothermal properties, and fire behaviour. Results show that granulate morphology affects the mechanical shear and flexure behaviour, as well as the acoustic absorption. Its impact on the compression strength is less pronounced. A greater portion of Typha fibers reduces the mechanical strength. However, hygrothermal performances are increased due to the aggregates porosity. Typha transverse fraction improves thermal resistance and increase water vapor transfer. This study also shows that these materials are excellent moisture regulators. Finally, fire tests reveal that it can be classified as combustible but non-flammable due to the clay presence. The fibres shape does not have a great influence

Dans cette thèse, nous étudions un métamatériau inspiré de la paille de blé pour l'absorption parfaite du son. Une botte de paille estidéalisée comme un milieu poreux anisotrope, composé d’un arrangement périodique très concentré de tubes creux cylindriques. L’approche théorique de ce métamatériau repose sur l'homogénéisation asymptotique à deux échelles d'un réseau perméable de résonateursparfaitement rigides dont la physique est enrichi par des résonances internes. Les principales caractéristiques de ce milieu poreux sont lacompressibilité effective négative autour de la résonance du tube et la réduction drastique de la vitesse de propagation du son (slowsound) à très basse fréquence. Une configuration optimale est conçue, basée sur la condition de couplage critique, pour laquelle la fuited’énergie du système résonnant ouvert est parfaitement compensée par les pertes intrinsèques induites par les pertes viscothermiques.Des mesures en tube à impédance sont effectuées sur des échantillons fabriqués par impression additive pour valider les résultatsthéoriques. Nous montrons que ce métamatériau est un absorbeur sub-longueur d'onde capable d’une absorption parfaite à très bassefréquence et d'introduire une quasi-bande interdite autour de la résonance du tube. De plus, la nature anisotrope de ce matériau conduit àune absorption globalement élevée à basse fréquence et ce pour toutes les incidences. Cette étude offre la possibilité de concevoir unabsorbeur acoustique sélectif en angle et en fréquence. Pour conclure, les résultats de cette thèse montrent que la paille est un boncandidat pour une absorption acoustique parfaite
Straw-inspired metamaterials for sound absorption are investigated in this Thesis. A straw stack is idealized as a highly concentratedresonant anisotropic porous medium constituted of a periodic arrangement of densely packed cylindrical hollow tubes. The approach tothis metamaterial relies on the two-scale asymptotic homogenization of a permeable array of perfectly rigid resonators, where the physicsis further enriched by tailoring inner resonances. The main features of such sound absorbing medium are the possibility for the effectivecompressibility to become negative around the tube resonance and the drastic reduction of the effective sound speed (slow sound) at verylow frequency in the system. Moreover, an optimal configuration for sound absorption is designed, based on the critical couplingcondition, in which the energy leakage out of the open resonant system is perfectly compensated by the intrinsic losses induced by thevisco-thermal losses both in the anisotropic matrix and in the resonators. Impedance tube measurements are performed on 3-D printedsamples with controlled parameters to validate the theoretical results. This metamaterial is a sub-wavelength absorber that can achievetotal absorption at a very low frequency and possesses a quasi-band-gap around the tube resonance. Furthermore, the anisotropic nature ofthe configuration gives rise to high absorption at low-frequency range for all incidences and diffuse field excitation. It paves the way tothe design of angular and frequency selective sound absorber. To conclude, the results of this Thesis show that straw is a good candidatefor perfect sound absorption

This document reports on a research project aimed at developing a concrete acoustic barrier made from Recycled Aggregate (RA) Concrete. The research project was undertaken in response to the needs expressed by the Victorian concrete recycling industry. The industry, the scientific community conducting research into relevant disciplines, and the community at large, represented by Victorian government agencies, are of the opinion that there is a need to devise a higher value utilisation application for selected concrete recycling products. This document outlines the rationale and objectives of the research project which involves the examination of Recycled Concrete (RC) Aggregate, the design and examination of RA Concrete, and finally the development of an acoustic barrier made from RA Concrete. The literature review presented in this report examines aspects of concrete recycling and concrete technology pertaining to traditional and alternative constituent materials for concrete production. Firstly, the importance and influence of fine and coarse aggregate on basic properties of concrete is introduced. Secondly, an account on the use of alternative materials in concrete technology, especially of coarse recycled aggregates and supplementary cementitious materials (SCM) is described. Thirdly, some of the physical and mechanical properties and how the use of RC Aggregate and SCM changes these properties are discussed. Fourthly, a number of commonly used techniques and neutron scattering techniques to investigate aggregate and concrete properties are introduced and discussed. Fifthly, the porosity of aggregate and concrete including durability are specifically discussed and testing methods are reasoned. The literature review also discusses the use of no-fines concrete; its physical, mechanical and acoustic properties. Finally it presents an account of the use of concrete in transportation traffic noise attenuation devices. This document continues with an outline of a methodology that was adopted in this research project. It outlines experimental work aimed at examining the properties of RC Aggregate which amongst other properties includes porosity, particle size distribution, water absorption, shape and density. It continues examining RA Concrete properties and includes, among other properties, compressive strength, porosity and durability as well as sound absorption of acoustic barrier. The methodology introduces standard and purposely modified test procedures used in the examination of aggregates, concrete and acoustic barrier. An account of various research techniques is presented, spanning from simple visual observations to more sophisticated neutron scattering techniques. The summary of test procedures follows a description of test specimen composition and their sizes, and a suite of tested specimens. It also introduces statistical methods used to analyse test results. After a detailed description of the aggregate, concrete and RA Concrete acoustic barrier, the document outlines a summary of data generated through the experimental program of this research project. The data on fine aggregate, on selected 14/10mm coarse RC Aggregate, on concrete made from natural and recycled aggregate and on acoustic barrier are presented and discussed. Test results of various physical, mechanical and acoustic properties of aggregate, concrete and barrier are reported, analysed and discussed. The data from observations, visual assessment and scientific experimentation of specific properties are then crossed analysed in a search for relationships between properties of fine and coarse aggregates and properties of concrete made from such aggregates. A cross analysis of data on ?less-fines? RA Concrete and on the acoustic performance of barrier is examined, and the relationship between the volume of interconnected voids in a porous part of ?less-fines? concrete, and the sound absorption of acoustic barrier is discussed and reported. The document then presents a synthesis of the literature review results, project aims adopted within the experimental program and test results in the three main areas of this research project. These areas include recycled concrete aggregate, recycled aggregate concrete and acoustic barrier made from RA Concrete. Finally, conclusions reached through the course of this investigation are summarised and recommendations are proposed in relation to the RA Concrete acoustic barrier. The main conclusion is that selected RC Aggregate can be used in the production of concrete of a compressive strength of 25MPa, if the moisture content and water absorption in the aggregate are closely monitored, and the foreign material content is kept below 1.5%. The author concludes that acoustic barrier made from selected RC Aggregate has unique sound absorption characteristics that can easily be tunable by a selection of appropriate aggregate and by specific concrete mix designs. Recommendations for further research are also proposed.

Thesis (PhD) - Swinburne University of Technology, 2006.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering, Swinburne University of Technology - 2006. Typescript. Includes bibliographical references.

The primary aim of this research was to investigate the fundamental acoustic properties of several cementitious materials, the influence of mix design parameters/constituents, and finally the effect of the physical and mechanical properties of cementitious material concrete/mortar on the acoustic properties of the material. The main objectives were: To understand the mechanism of sound production in musical instruments and the effects of the material(s) employed on the sound generated; To build upon previous research regarding selection of the tested physical/mechanical properties and acoustic properties of cementitious materials; To draw conclusions regarding the effect of different constituents, mix designs and material properties upon the acoustic properties of the material; To build a model of the relationship between the acoustic properties of a cementitious material and its mix design via its physical/mechanical properties. In order to meet the aim, this research was conducted by employing the semi-experimental (half analytical) method: two experimental programmes were performed (I and II); a mathematical optimization technique (least square method) was then implemented in order to construct an optimized mathematical model to match with the experimental data. In Experimental Programme I, six constituents/factors were investigated regarding the effect on the physical/mechanical and acoustic properties: cementitious material additives (fly ash, silica fume, and GGBS), superplasticizer, and basic mix design parameters (w/c ratio, and sand grading). 11 properties (eight physical/mechanical properties: compressive strength, density, hardness, flexural strength, flexural modulus, elastic modulus, dynamic modulus and slump test; and three acoustic properties: resonant frequency, speed of sound and quality factor (internal damping)) were tested for each constituents/factors related mortar type. For each type of mortar, there were three cubes, three prisms and three cylinders produced. In Experimental Programme I, 20 mix designs were investigated, 180 specimens produced, and 660 test results recorded. After analysing the results of Experimental Programme I, fly ash (FA), w/b ratio and b/s ratio were selected as the cementitious material/factors which had the greatest influence on the acoustic properties of the material; these were subsequently investigated in detail in Experimental Programme II. In Experimental Programme II, various combinations of FA replacement level, w/b ratios and b/s ratios (three factors) resulted in 1122 test results. The relationship between these three factors on the selected 11 properties was then determined. Through using regression analysis and optimization technique (least square method), the relationship between the physical/mechanical properties and acoustic properties was then determined. Through both experimental programmes, 54 mix designs were investigated in total, with 486 specimens produced and tested, and 1782 test results recorded. Finally, based upon well-known existing relationships (including, model of compressive strength and elastic modulus, and the model of elastic modulus and dynamic modulus), and new regressioned models of FA-mortar (the relationship of compressive strength and constituents, which is unique for different mixes), the optimized object function of acoustic properties (speed of sound and damping ratio) and mix design (proportions of constituents) were constructed via the physical/mechanical properties.

This project was intended to provide empirical data to determine if materials (e.g. Cocobolo, Mopane, Grenadilla, Delrin, and Purpleheart) used to make clarinet barrels have an effect on sound quality and response. The following questions were addressed in this study: For clarinet barrels, do different types of exotic hardwoods and plastics have a measurable effect on the sound qualities (timbre) of the clarinet? Do different materials used to manufacture clarinet barrels have a measurable effect on the response (immediacy of tone and vibration to the player) of the instrument? Do different materials have a measurable impact on the intensity (volume/projection) of the clarinet? Will participants have a preference for specific materials tested? Results indicated that 25% of participants chose Mopane, 25% of participants chose Grenadilla, 25% of participants chose Delrin, and 25% of participants chose Purpleheart, meaning no material was preferred by a majority of the participants. No participant chose Cocobolo. Though there were commonalities among recordings of each material, the findings were not substantial enough to determine true differences in timbre, response to articulation, or intensity.

This thesis addresses the processing, morphology, mechanical properties, and acoustic properties of new polymeric foam materials. A batch foaming process, a rotational mold foaming process and a constrained mold foaming process were designed and applied in the producing of polymeric foams. Microcellular closed cell polymethyl-methacrylate (PMMA) foams were produced using the batch foaming process. The foam morphologies and mechanical properties such as elastic modulus, tensile strength and elongation at break were investigated by varying the foaming parameters. The PMMA microcellular foam showed superior mechanical properties in tensile strength and elongation at break over conventional foams. Nanoclay was used as reinforcement filler and a nucleation agent for PMMA in the batch foaming process. The nanoclay affected the foaming behavior and enhanced the mechanical properties of the microcellular PMMA foams. The PMMA nanocomposite foam with 0.5 wt % nanoclay exhibited optimized mechanical properties. Fine celled Polypropylene (PP) and low density Polyethylene (LDPE) foams were also produced using the rotational mold foaming. The processing parameters such as the particle sizes and processing time were important parameters in this process. The obtained PP foam exhibited a greatly improved energy absorption capacity. Opened cell PMMA foams were produced using a particulate leaching/gas foaming method for acoustic absorption applications. The foam morphology i.e. porosity and cell sizes were independently controlled by altering the processing settings. Consequently, the acoustic performance of the foams was manipulated. Finite element analysis was then employed to predict the macroscopic properties of polymeric foams correlated to their microstructure. The predicted elastic responses of both opened cell and closed cell foams showed great agreement with experimental results.

Los materiales absorbentes porosos son de gran interés en el campo de la acústica debido a su amplia aplicabilidad a muchos problemas de ingeniería de control de ruido. Algunos de estos problemas son la contaminación acústica excesiva en las infraestructuras de transporte (carreteras, vías de tren,…) o la falta de sistemas efectivos de reducción de ruido en los edificios (residenciales, oficinas,…). Ambos se han convertido en un problema de gran preocupación en la sociedad moderna no solo por los efectos nocivos sobre la salud humana sino también por el impacto negativo en el medio ambiente y su conservación. De hecho, el ajetreado ritmo de vida en nuestra sociedad actual ha hecho del ruido una de las principales fuentes de estrés y convertido éste en el principal enemigo del descanso, induciendo a su vez una mayor despreocupación hacia el cuidado y preservación de dicho medio ambiente. Con el fin de concienciar a nuestra sociedad y a los agentes que la conforman hacia un mejor uso de los recursos naturales, autoridades públicas nacionales e internacionales siguen trabajando en el desarrollo de normativas que ayuden a reducir este impacto negativo en el entorno. De hecho, la creciente necesidad de dispositivos que mejoren el aislamiento acústico ha motivado que comunidad científica e industria centren parte de sus esfuerzos en el desarrollo de nuevas e innovadores soluciones que reduzcan el ruido y ayuden a mejorar el bienestar de las personas. Así, se persigue que dichas soluciones garanticen una reducción de los niveles de ruido en los distintos ámbitos sociales siendo a su vez una condición de mayor peso que estas tengan un carácter sostenible y respetuoso con el medio. Algunos ejemplos de ello son los equipos de protección auditiva contra el ruido de maquinaria en áreas industriales, la reducción del ruido del tráfico en áreas urbanas e interurbanas utilizando barreras acústicas, o el aislamiento al ruido en edificios mediante soluciones constructivas mejoradas. En este contexto, el uso de materiales absorbentes porosos se ha convertido en una de las soluciones pasivas más extendidas para el control del ruido hasta la fecha. Por lo tanto, el estudio del comportamiento acústico de estos materiales porosos no solo constituye una prioridad en la etapa de diseño de dispositivos contra el ruido, sino también en la evaluación de su rendimiento como absorbente sonoro. En resumen, los casos de estudio analizados sirven tanto como una contribución al estudio de las propiedades acústicas de materiales absorbentes porosos, como para alentar el uso de algunos de los enfoques propuestos en problemas reales de ingeniería. Aunque aún queda trabajo por hacer para establecer los modelos y metodologías presentados, y por qué no, para hacerlos extensivos para su aplicabilidad en un marco multidisciplinario, queda patente su aportación en aras del bienestar social y el desarrollo humano.

La mise en oeuvre de matériaux acoustiques est une méthode efficace et très utilisée pour réduire le bruit le long de sa propagation. Les propriétés acoustiques de nouvelles structures sandwich multifonctionnelles et de matériaux absorbants poreux sont étudiées dans la thèse. Les principales contributions de la thèse sont les suivantes: Les panneaux sandwich ont généralement d'excellentes propriétés mécaniques et un bon indice de perte en transmission sonore (STL), mais aucune capacité d'absorption acoustique. De nouvelles structures sandwich multifonctionnelles sont développées en intégrant des microperforations et des matériaux absorbants poreux aux panneaux sandwich ondulés et en nid d’abeilles conventionnels, structurellement efficaces pour obtenir de bons STL et de bonnes absorptions en basses fréquences. Le coefficient d'absorption acoustique (SAC) et la perte en transmission (STL) des panneaux sandwich ondulés sont évalués numériquement et expérimentalement en basse fréquence pour différentes configurations de perforations. Les modèles éléments finis (EF) sont construits en tenant compte des interactions vibro-acoustiques sur les structures et des dissipations d'énergie, visqueuse et thermique, à l'intérieur des perforations. La validité des calculs FE est vérifiée par des mesures expérimentales avec les échantillons testés obtenus par fabrication additive. Par rapport aux panneaux sandwich ondulés classiques sans perforation, les panneaux sandwich perforés (PCSPs) avec des perforations dans leur plaque avant présentent non seulement un SAC plus élevé aux basses fréquences, mais aussi un meilleur STL, qui en est la conséquence directe. L'élargissement des courbes des indices d’absorption et de transmission doit être attribué à la résonance acoustique induite par les micro-perforations. Il est également constaté que les PCSPs avec des perforations dans les plaques avant et les parois internes onduleés ont les fréquences de résonance les plus basses de tous les PCSPs. En outre, les performances acoustiques des panneaux sandwich en nid d'abeilles avec une plaque avant microperforée sont également examinées. Un modèle analytique est présenté avec l'hypothèse que les déplacements des deux plaques sont identiques aux fréquences inférieures à la fréquence de résonance des plaques. Le modèle analytique est ensuite validé par des modèles d'éléments finis et des résultats expérimentaux existants. Contrairement aux panneaux sandwich en nid d'abeilles classiques qui sont de piètres absorbeurs de bruit, les sandwichs en nid d'abeilles perforés (PHSPs) conduisent à un SAC élevé aux basses fréquences, ce qui entraîne en conséquence un incrément dans le STL basse fréquence. Les influences de la configuration du noyau sont étudiées en comparant les PHSPs avec différentes configurations de noyaux en nids d'abeilles. […]
Implementation of acoustic materials is an effective and popular noise reduction method during propagation. Acoustic properties of novel multifunctional sandwich structures and porous absorbing materials are studied in the dissertation. The main contributions of the dissertation are given as, Sandwich panels generally have excellent mechanical properties and good sound transmission loss (STL), but no sound absorption ability. Novel multifunctional sandwich structures are developed by integrating micro perforations and porous absorbing materials to the conventional structurally-efficient corrugated and honeycomb sandwich panels to achieve good SAC and STL at low frequencies. Low frequency sound absorption and sound transmission loss (STL) of corrugated sandwich panels with different perforation configurations are evaluated both numerically and experimentally. Finite element (FE) models are constructed with considerations of acousticstructure interactions and viscous and thermal energy dissipations inside the perforations. The validity of FE calculations is checked against experimental measurements with the tested samples provided by additive manufacturing. Compared with the classical corrugated sandwich panels without perforation, the perforated corrugated sandwich panels (PCSPs) with perforations in its face plate not only exhibits a higher SAC at low frequencies but also a better STL as a consequence of the enlarged SAC. The enlargement of SAC and STL should be attributed to the acoustical resonance induced by the micro perforations. It is also found that the PCSPs with perforations in both the face plates and corrugated cores have the lowest resonance frequencies of all the PCSPs. Besides, the acoustic properties of honeycomb sandwich panels with microperforated faceplate are also explored. An analytical model is presented with the assumption that displacements of the two faceplates are identical at frequencies below the faceplate resonance frequency. The analytical model is subsequently verified by finite element models and existing experimental results. Unlike classical honeycomb sandwich panels which are poor sound absorbers, perforated honeycomb sandwiches (PHSPs) lead to high SAC at low frequencies, which in turn brings about increment in the low frequency STL. Influences of core configuration are investigated by comparing PHSPs with different honeycomb core configurations. In order to enlarge the SAC bandwidth of perforated sandwich panels, porous absorbing materials are added to the cores of novel perforated sandwich panels. FE models are set up to estimate the SAC and STL of perforated sandwich panels with porous materials. Results show that perforated sandwich panels with porous material can provide SAC with broader bandwidth and lower resonance frequency than that without porous materials. Whereas the peak values in the SAC and STL curves are reduced due to the weakened acoustical resonance by the porous materials. […]

The need for improved timber grading is key to improving Scottish forestry: the majority (80%) of the sustainable softwood population in Scotland is Sitka spruce of variable quality. Current visual assessment of strength and stiffness is inaccurate, and machine stress grading in sawmills is little better due to incorrect assumptions regarding consistency within softwood species and between trees of the same stand. The author develops and evaluates non-destructive test (NOT) methods for Scottish Sitka spruce based upon impact-e9ho testing across a range of scales from plank, to log, to standing tree. Correlations between harmonic wave propagation velocity and elastic modulus of 0.62 ::; R2 ::; 0.71 were possible in Sitka spruce under a range of conditions including: genotype progeny, variable height and radial position in stem, and variable knot content. In achieving this correlation, the research also investigated acoustic parameters such as: time of flight velocity, damping ratio, and resonant peak behaviour with regard to their influence on dynamically derived moduli of elasticity. Examination of variation in wood properties (including static elastic modulus, knot content, simulated decay, density, and grain alignment) on these acoustic parameters was conducted on semi-controlled specimens of differing homogeneities. The consequences of these results should influence the development of timber NOT tools. In addition to the development of an NOT method, the author has provided the first large-scale derivation of reference values for dynamic stiffness and other acoustic properties for 35 year old logs and beams of Sitka spruce in Scotland.

Experience shows that the noise and sound quality in vehicles are often a recurring criticism. The bodies of modern vehicles consist predominantly of thin sheets of metal. It is hard to prevent the excitation of bending vibrations and the subsequent emission of disturbing noise while driving. The noise spectrum in a car that can be heard by the driver is from ”latent roar” to ”chattering” noise of the body and engine. In automotive vehicles damped materials, especially plastics or materials made from sheet metal and surface damping treatments, are used. Those have high internal energy losses and damp sound oscillatory systems found in the body or interior of cars. A further advantage of such treated components is that they are applied to existing components working over wide temperature and frequency ranges. Many companies provide such ”sound-absorbing compounds”. The requirements for these damping materials are high temperature-resistance, water repellence, fuel and oil-resistance and good adhesion to the base material [17]. The acoustic properties, especially the damping of the plate vibrations through rubber are of interest. the question arises how can the damping coeficient of coated metal sheets can be measured and secondly, by how much the road noise is reduced when built-in sheets are coated with a known damped material. With the Oberst Bar Test Method (named after Dr. H. Oberst) the properties are determined of the internal damping materials that can be used to simulate mechanical constructions to determine damping of larger surfaces. This method describes a laboratory test procedure for measuring the mechanical properties of damped materials. A block diagram of the test system consisting of a damped material bonded to a vibrating cantilever steel bar is shown in figure 2.1. This method is useful for testing materials such as metals, enamels, ceramics, rubbers, plastics, reinforced epoxy matrices and wood. In addition to damping measurement, the test allows for the determination of the Young’s modulus E of the material. E is calculated from the resonance frequency of a given mode and from the physical constants of the bar. By associating the damping factor with the Young’s modulus, a complex quantity is defined which is called the Complex Modulus of Elasticity. Measurements of dynamic mechanical properties are also useful in the research on the molecular structure of materials.

The present-day challenges in the transport industry, steered by the increasing environmental awareness, necessitate manufacturers to take measures to reduce emissions related to the movements of goods and humans. In particular, the measures aiming at a reduced mass or higher load capacity to increase fuel efficiency,  generally deteriorate the noise and vibration insulation properties of their products. In order to comply with the regulations and customer demands, modern vehicles increasingly move towards a multifunctional integrated design approach, if possible for all subcomponents involved. Such a multifunctional design approach is an iterative process, evaluating the proposed solutions in every stage, and is therefore best performed in a virtual testing environment. \\Poroelastic materials are interesting to include in a multifunctional design, offering reasonably good vibro-acoustic insulation properties at a low weight penalty. These materials can also be combined in multilayer arrangements to further enhance the overall performance. \\In order to achieve an accurate modelling of the vibro-acoustic behaviour of poroelastic materials, the input data describing the material properties should be of a high quality. Two characteristics inherent to these materials encumber a precise characterisation with traditional techniques. Poro-elastic aggregates are anelastic due to the constituent material used, and anisotropic as a consequence of the production process. Characterisation techniques allowing for an accurate determination of the material properties need to take these intrinsic characteristics into account.\\The objective in this thesis is to enable the characterisation of a constitutive material model for poroelastic materials which is as general as possible, and includes the inherent material anelasticity and anisotropy. For this purpose, a set of advanced characterisation techniques has been developed to characterise the anisotropic flow resistivity tensor and the anisotropic dynamic Hooke's tensor. \\These advanced characterisation techniques are based on an inverse estimation procedure, used consistently throughout the work, and includes both experiments and numerical predictions. The property to characterise is isolated in a specially designed set-up such that it can be modelled by physics solely involving this property. The obtained experimental and numerical data then serve as the input to an optimisation, which returns the material properties for which the difference between both is as small as possible. These methods have been successfully applied to melamine foam, which is found to be both anisotropic and anelastic, confirming the need for such advanced characterisation techniques.

QC 20131219

Lightweight floor structure is widely used in building industries and to have better sound insulation builders come up with different ways of construction. Depending on the construction the floor structure could either be coupled (floor and ceiling coupled by beams) or decoupled (no mechanical connection between floor and ceiling). Although there are many models on coupled structure but for decoupled structure the number is not too many. Keeping that in mind the present thesis talks about lightweight floors: the construction, properties, behaviour etc with a focus on developing a model for decoupled floor structure where the core contribution being the decoupling and adding the moment effect at plate beam joints. The advantage of decoupled structure is that it disconnects the sound bridge through the beams. One consequence on the other hand is that cavity resonance dominates the low frequency region. A comparative analysis is also done with the coupled model. While developing the model this talks about different mathematical tools such as Fourier transform, Floquet principle, Poisson's sum formula etc This also gives an overview of different types of modelling technique available such as analytical, Numerical, energy based approach, empirical method etc. A parametric study is also done here to find out the relative influence of different elements on sound pressure level.

Godkänd; 2010; 20100809 (sazmos); LICENTIATSEMINARIUM Ämnesområde: Teknisk akustik/Engineering Acoustics Examinator: Professor Anders Ågren, Luleå tekniska universitet Diskutant: Docent Jonas Brunskog, DTU, Department of Electrical Engineering, Denmark Tid: Tisdag den 7 september 2010 kl 14.00 Plats: F719 Taylor, Luleå tekniska universitet

This thesis is concerned with developing porous materials from tyre shred residue and polyurethane binder for acoustic absorption and thermal insulation applications. The resultant materials contains a high proportion of open, interconnected cells that are able to absorb incident sound waves through viscous friction, inertia effects and thermal energy exchanges. The materials developed are also able to insulate against heat by suppressing the convection of heat and reduced conductivity of the fluid locked in the large proportion of close-cell pores. The acoustic absorption performance of a porous media is controlled by the number of open cells and pore size distribution. Therefore, this work also investigates the use of catalysts and surfactants to modify the pore structure and studies the influence of the various components in the chemical formulations used to produce these porous materials. An optimum type and amounts of catalyst are selected to obtain a high chemical conversion and a short expanding time for the bubble growth phase. The surfactant is used to reduce the surface tension and achieve a homogenous mixing between the solid particulates tyre shred residue, the water, the catalyst and the binder. It is found that all of the components significantly affect the resultant materials structure and its morphology. The results show that the catalyst has a particularly strong effect on the pore structure and the ensuing thermal and acoustical properties. In this research, the properties of the porous materials developed are characterized using standard experimental techniques and the acoustic and thermal insulation performance underpinned using theoretical models. The important observation from this research is that a new class of recycled materials with pore stratification has been developed. It is shown that the pore stratification can have a positive effect on the acoustic absorption in a broadband frequency range. The control of reaction time in the foaming process is a key function that leads to a gradual change in the pore size distribution, porosity, flow resistivity and tortuosity which vary as a function of sample depth. It is shown that the Pade approximation is a suitable model to study the acoustic behaviour of these materials. A good agreement between the measured data and the model was attained.

This thesis describes the novel test techniques that were developed to measure the parameters associated with the plastic shrinkage, and subsequent possible plastic shrinkage cracking, of high strength concrete. The parameters measured during the first 24 hours after placing were the stress- strain relationship, negative pore pressure and free shrinkage strain development. The plastic behaviour of eight high strength concrete mixes was quantified and these mixes were then tested to assess their propensity towards plastic shrinkage cracking, using restrained ring tests. A review of the parameters associated with plastic shrinkage cracking was carried out. The general view was that as the particle size in a cement matrix gets smaller, then the negative pore pressures developed are greater and hence shrinkage increases. This meant that the presence of secondary cementing materials, of very small diameter, such as microsilica, in high strength concretes would explain their apparent susceptibility to plastic shrinkage cracking. Eight high strength concrete mixes were tested in exposed and sealed conditions. It was found that when tested in sealed conditions none of the parameters measured presented itself as the sole driving force behind plastic shrinkage or plastic shrinkage cracking. Also, when cured in sealed conditions, none of the mixes tested in the restrained ring test apparatus cracked. When tested in exposed conditions, the presence of wind had little effect on the stress-strain relationship of the mixes tested. However the presence of wind seemed to cause negative pore pressures to develop earlier than in the sealed samples and increased free shrinkage by 3 to 40 times depending on the mix. The samples that exhibited the highest free shrinkage strains, in exposed conditions, were the mixes that cracked when tested in the restrained shrinkage rings. The mixes that cracked all contained microsilica and these mixes did not crack when the same mixes were tested without microsilica. Polypropylene fibres were found to reduce the cracked area of the samples that cracked. The supplementary cementing materials used in this study were ground granulated blast furnace slag, metakaolin, microsilica and pulverised fuel ash.

The production processes of porous materials introduce an inherent geometric anisotropy in the material at micro scale, which influences the material properties at macro scale. In this thesis, the focus is turned to one of these macroscopic properties, the flow resistivity, which is a measure of the resistance felt by the sound pressure waves as they propagate through a porous space. In the current work, two different porous materials have been studied, a fibrous glass wool and a Melamine foam. The two materials are expected to show different degrees of anisotropy with respect to flow resistivity. Glass wool is assumed to be transversely isotropic, as a result of the stacking of layers of fibres. The level of anisotropy in Melamine foam is not as obvious, and might be related to production specific aspects, such as the rise-direction, and the position of the injection nozzles. The thesis begins by giving an introduction to porous materials in general, and to glass wool and Melamine foam in particular, followed by an introduction to flow resistivity, together with two methods to measure the flow resistivity. The full anisotropic flow resistivity of glass wool and Melamine foam samples is determined by means of measurements and inverse estimation. An eigenvalue and eigenvector decomposition of the flow resistivity tensor provides an insight into the connection between the directionality of the flow resistivity in each material, and its production process. A study of the homogeneity in density and flow resistivity for the two materials shows that these properties vary within the block of material. However, for each material, there seems to be no connection between the variation in the two properties, investigated at the macroscopic scale.
QC 20110311

An equivalent material approach is presented for the computation of the elastic properties of brick masonry and for the assessment of salt crystallization in masonry structures. A stacked brick-mortar system consisting of a series of parallel layers which behave elastically is introduced. This is extended such that masonry with two sets of mortar joints (bed and head joints) can be represented by an equivalent homogeneous orthotropic elastic material. It is then extended to salt deteriorated brick masonry by including salt crystals induced within the pores. In terms of the elastic properties of the brick and mortar, as well as relative thicknesses, expressions for the equivalent material's elastic properties are derived. The mechanical properties of salt deteriorated masonry are computed in terms of effective porosity and saturation ratio. Using this derivation, the stresses in the brick-and-mortar joints are calculated for a masonry wall partial deteriorated by salt and subjected to thermal stress variation.

A novel way to ensure stability of mortarless structures – topological interlocking – is examined. In this type of interlocking the overall shape and arrangement of the building blocks are chosen in such a way that the movement of each block is prevented by its neighbours. (The methodological roots of topological interlocking can be found in two ancient structures: the arch and the dry stone wall.) The topological interlocking proper is achieved by two types of blocks: simple convex forms such as the Platonic solids (tetrahedron, cube, octahedron, dodecahedron and icosahedron) that allow plate-like assemblies and specially engineered shapes of the block surfaces that also allow assembling corners. An important example of the latter – so-called Osteomorphic block – is the main object of this research with some insight being provided by numerical modelling of plates assembled from tetrahedra and cubes in the interlocking position. The main structural feature of the interlocking assemblies is the need of the peripheral constraint (for the Osteomorphic blocks this requirement can be relaxed to uni-directional constraint) to keep their integrity. We studied the least visible constraint structure – internal pre-stressed cables which run through pre-fabricated holes in Osteomorphic blocks. It is shown that the pre-stressed steel cables can provide the necessary constraint force without creating appreciable residual stresses in the cables, however the points of connection of the cables are the weakest points and need special treatment. The main mechanical feature of the interlocking structures is the absence of block bonding. As a result, the blocks have a certain freedom of translational and rotational movement (within the kinematic constraints of the assembly) and their contacts have reduced shear stresses which hampers fracture propagation from one block to another. These features pre-determine the specific ways the interlocking assemblies behave under mechanical and dynamic impacts. These were studied in this project and the following results are reported. As the blocks in the interlocking structure are not connected, the main issue is the bearing capacity. The study of the least favourable, central point loading in the direction normal to the structure shows elevated large-scale fracture toughness (resistance to fracture propagation). However when the central force imposes considerable bending the generated tensile membrane stresses assist fracturing of the loaded block. Prevention of bending considerably enhances the strength therefore the most efficient application of the interlocking structures would be in protective coatings and covers. Furthermore, proper selection of the material properties and the interface friction can increase the system overall strength and bearing capacity. The results of the computer simulations suggest that both Young’s modulus and the friction coefficient are the key parameters whose increase improves the bearing capacity of topologically interlocking assemblies.

Many applications of ultrasound test phantoms require that the acoustical properties of the phantom should closely match those of soft tissue. Numerous commercial test phantoms of this type are available for use with clinical ultrasound scanners, which use frequencies up to 20 MHz. However, scanners designed for imaging small animals in preclinical studies, typically operate at much higher frequencies. No commercially available test phantoms exist for use at frequencies above 20 MHz. The aim of this work was to develop a tissue-mimicking-material (TMM) that closely matches the acoustic properties of small animal tissues at high frequencies (HF). Such a material would, therefore, be suitable for ultrasound test phantoms for application with HF ultrasound scanners (20 MHz to 50 MHz). A three-step approach was adopted to address this lack of a suitable HF-TMM. Firstly, verify the acoustic characteristics of the existing IEC agar-based TMM. Secondly, establish the acoustic properties (speed of sound and attenuation coefficient) of small animal tissue at high frequencies. Thirdly, develop a TMM which exhibits, as closely as possible, these small animal tissue acoustic characteristics. A pulse-echo substitution method was used throughout to characterise the materials and the tissue samples. The speed of sound and attenuation coefficient of an IEC agar-based TMM were measured using two different techniques. Initially, a widely used method was tried, where samples are wrapped in film and placed in degassed, deionised water for assessment. The second technique was developed and validated for use in this work. In this method, TMM samples were uncovered (without film) and were both stored and assessed in a TMM preserving fluid. The second method provided up to four times more consistent results. The acoustical properties of the individual components of the IEC agar-based TMM were then measured in order to determine whether the overall attenuation coefficient of the agar TMM was a linear sum of the attenuation coefficients of its component parts. Within experimental uncertainties, this was found to be the case. This is a key observation from which the formulation of an agar TMM, matching the acoustic properties of small animal tissue, can be facilitated. The acoustical properties (speed of sound and attenuation coefficient) of mouse brain, liver, and kidney were measured using a preclinical ultrasound scanner.

The dissertation analyses the sound-insulating qualities of building materials and structures. The aim of the dissertation is to investigate and indentify, under natural conditions and in a noise suppression chamber, the structures which, as internal and external components of buildings, would ensure the protection of inte-rior rooms against noise and to model on this basis the sound reduction indices of structures. The work deals with several main tasks: investigations of the acoustic quali-ties of building materials and structures in a noise suppression chamber and under natural conditions; comparison of results obtained from measurements, and the evaluation of the sound reduction indices of perspective structures through model-ling. The introductory chapter introduces the problem addressed and topicality of the work, describes the object of research, formulates aim and tasks of the work, describes research methodology, scientific novelty of the work, points out practi-cal value of the work’s results and specifies defended propositions. The introduc-tion ends with a list of articles on the dissertation topic published by the author and the structure of the dissertation. The first chapter analyses literature relating with the dissertation topic. Con-clusions are formulated at the end of the chapter. The beginning of each chapter presents research methodologies. The second chapter differentiates investigations which were carried out in a noise suppression chamber and... [to full text]
Disertacijoje nagrinėjamos statybinių medžiagų ir konstrukcijų garso izoliaci-nės savybės. Disertacijos tikslas – natūrinėmis sąlygomis ir triukšmo slopinimo kameroje ištirti ir nustatyti konstrukcijas, kurios, kaip pastatų vidinės ir išorinės sudėtinės dalys, užtikrintų vidaus patalpų apsaugą nuo triukšmo, ir tuo pagrindu sumodeliuoti konstrukcijų garso izoliavimo rodiklius. Šiame darbe sprendžiami keli pagrindiniai uždaviniai: statybinių medžiagų ir konstrukcijų akustinių savybių tyrimai triukšmo slopinimo kameroje ir natūrinė-mis sąlygomis, matavimų rezultatų palyginimas, perspektyvių konstrukcijų garso izoliavimo rodiklių įvertinimas modeliavimo būdu. Disertaciją sudaro įvadas, aštuoni skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašas. Įvadiniame skyriuje pristatoma tiriamoji problema, darbo aktualumas, apibū-dinamas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, nusakomas darbo mokslinis naujumas ir darbo rezultatų praktinė reikšmė, išvardijami ginamieji teiginiai. Įvadas baigiamas disertacijos tema auto-riaus paskelbtų publikacijų ir pranešimų konferencijose pristatymu bei disertacijos struktūra. Pirmajame skyriuje analizuojama su disertacijos tema susijusi literatūra. Sky-riaus pabaigoje formuluojamos išvados. Tyrimų metodikos pateiktos kiekvieno skyriaus pradžioje. Antrajame skyriuje išdiferencijuojami triukšmo slopinimo kameroje vykdyti tyrimai ir analizuojami jų... [toliau žr. visą tekstą]

A cold extrusion process has been developed to tailor a porous structure from polymeric waste. The use of an extruder to manufacture acoustic materials from recycled waste is a novel idea and the author is not aware of any similar attempts. The extruder conveys and mixes the particulates with a reacting binder. The end result is the continuous production of bound particulates through which a controlled amount of carbon dioxide gas that is evolved during the reaction is used to give the desired acoustic properties. The cold extrusion process is a low energy consuming process that reprocesses the post manufacturing waste into new vibro-acoustic products that can be used to meet the growing public expectations for a quieter environment. The acoustical properties of the developed products are modelled using Pade approximation and Johnson-Champoux-Allard models. Applications for the developed products are widespread and include acoustic underlay, insulation and panels in buildings, noise barriers for motorways and railway tracks, acoustic insulation in commercial appliances and transport vehicles.

Soft trim absorbing parts (i.e., headliners, backwalls, side panels, etc.) are normally comprised of different layers including films, adhesives, foams and fibers. Several approaches to determine the complex wavenumber and characteristic impedance for porous sound absorbing materials are surveyed and the advantages and disadvantages of each approach are discussed. It is concluded that the recently documented three-point method produces the smoothest results. It is also shown that measurement of the flow resistance and the use of empirical equations is sufficient for many common materials. Following this, the transfer impedance of covers, adhesives, and densified layers are measured using an impedance difference approach. The transfer matrix method was then used to predict the sound absorption of a multi-layered materal which included a perforated cover, fiber layers, and an adhesive. The predicted results agree well with measurement.

Nous avons développé de nouveaux concepts de fabrication de matériaux nanostructurés en couche mince basés sur le dépôt par ablation laser alterné d'un métal (Ag) et d'un diélectrique (Al2O3). Cette technique permet d'atteindre un contrôle optimal sur les paramètres morphologiques des nanostructures qui déterminent la réponse optique des couches minces. Nous avons produit des nanosphères, des nanolentilles et des nanocolonnes, auto-organisées et orientées, encapsulées dans une matrice d'alumine amorphe. Leur réponse optique a été étudiée en fonction de leur morphologie et comparée à des simulations théoriques. En parallèle à cette étude, la réponse vibrationnelle des nanostructures a été analysée par spectrométrie Raman basse fréquence. Finalement, des nanostructures contenant des couches alternées de nanoparticules de Co et d'Ag séparées par une distance de quelques nanomètres ont aussi été fabriquées. Il a été montré que l'interaction entre le plasmon de surface et les modes sphéroïdaux de vibration des nanoparticules active le signal Raman.

Wood plastic composites (WPCs) were made using matrices of recycled high-density polyethylene (rHDPE) and polypropylene (rPP) with sawdust (Pinus radiata) as filler. Corresponding WPCs were also made using virgin plastics (HDPE and PP) for comparison with the recycled plastic based composites. WPCs were made through melt compounding and hot-press moulding with varying formulations based on the plastic type (HDPE and PP), plastic form (recycled and virgin), wood flour content and addition of coupling agent. The dimensional stability and mechanical properties of WPCs were investigated. Durability performances of these WPCs were studied separately, by exposing to accelerated freeze-thaw (FT) cycles and ultraviolet (UV) radiation. The property degradation and colour changes of the weathered composites were also examined. Dimensional stability and flexural properties of WPCs were further investigated by incorporation of nanoclays in the composite formulation. To understand the changes in WPCs stability and durability performance, microstructure and thermal properties of the composites were examined. Two mathematical models were developed in this work, one model to simulate the moisture movement through the composites in long-term water immersion and the other model to predict the temperature profile in the composites during hot-press moulding. Both rHDPE and rPP matrix based composites exhibited excellent dimensional stability and mechanical properties, which were comparable to those made from virgin plastics. Incorporation of maleated polypropylene (MAPP) coupling agent in composite formulation improved the stability and the mechanical properties. The incorporation of 3 wt. % MAPP coupling agent to WPCs showed an increase in tensile strength by 60% and 35 %, respectively, for the rHDPE based and rPP based composites with 50 wt. % wood flour. Scanning electron microscopy (SEM) images of the fractured surfaces of WPCs confirmed that the MAPP coupling improved the interfacial bonding between the plastic and the wood filler for both series of composites. Long-term water immersion tests showed that the water transport mechanism within the WPCs follows the kinetics of Fickian diffusion. Dimensional stability and flexural properties of the WPC were degraded after 12 accelerated FT cycles as well as 2000 h of UV weathering for both recycled and virgin HDPE and PP based composites. However, the MAPP coupled composites had improved stability and flexural property degradation. The surface of the weathered composites experienced a colour change, which increased with the exposure time. The MAPP coupled composites exhibited less colour change as compared to non-coupled composites. Regarding the effect of the plastic type, the PP based composites experienced higher colour change than those based on HDPE. With weathering exposure, flexural strength and stiffness of the WPCs were decreased, but elongation at break was increased regardless of plastic type and wood flour content. MAPP coupled rPP and rHDPE based UV weathered WPCs lowered the degradation of stiffness by 50% and 75%, respectively compared to non-coupled WPCs. SEM images of the fractured surfaces of FT and UV weathered WPCs confirmed a decrease in the interfacial bonding between the wood flour and matrix. Thermal properties of weathered composites changed with weathering, but the extent of the changes depended on WPCs formulation and matrix type. From the experimental studies on nanoclay-filled rHDPE composites, it is found that stability, flexural properties of WPCs could be improved with an appropriate combination of coupling agent, and nanoclay contents processed by melt blending. Incorporation of 1-5 wt. % nanoclay in the maleated polyethylene (MAPE) coupled wood plastic composite improved the dimensional stability and flexural properties. The thermal properties changed with the addition of nanoclay and MAPE in WPCs. In this work, a hot press-moulding model was proposed based on the one-dimensional transient heat conduction to predict the temperature profile of the WPCs during hot pressing cycle. The results from this work clearly show that rHDPE and rPP can be successfully used to produce stable and strong WPCs, which properties and performances are similar to or comparable to composites made of wood and virgin plastics. Therefore, WPCs based on recycled PP and HDPE matrix could have potential to use as construction materials.

Empirical models based on flow resistivity are commonly used to determine the bulk properties of porous sound absorbing materials. The bulk properties include the complex wavenumber and complex characteristic impedance which can be used directly in simulation models. Moreover, the bulk properties can also be utilized to determine the normal incidence sound absorption and specific acoustic impedance for sound absorbing materials of any thickness and for design of layered materials. The sound absorption coefficient of sound absorbing materials is measured in an impedance tube using wave decomposition and the measured data is used to determine the flow resistivity of the materials by least squares curve fitting to empirical equations. Results for several commonly used foams and fibers are tabulated to form a rudimentary materials database. The same approach is then used to determine the flow resistivity of compressed sound absorbing materials. The flow resistivities of the compressed materials are determined as a function of the compression ratio. Results are then used in conjunction with transfer matrix theory to predict the sound absorptive performance of layered compressed absorbers with good agreement to measurement.

Thesis (Ph.D)--Industrial and Systems Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Tsukruk, Vladimir; Committee Member: Bucknall, David; Committee Member: Kalaitzidou, Kyriaki; Committee Member: Shofner, Meisha; Committee Member: Tannenbaum, Rina. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.
Includes bibliographical references (leaves 91-96).
A three phase analytical protocol is developed to systematize the study of multifaceted serpentinite bronze-casting moulds from Bronze Age Anatolia (ca. 3500-1700 B.C.). These moulds represent a class of metal processing tools that reflect material properties and perhaps also social concerns in their development and use. In phase I of the protocol, standard serpentinite tiles are heated to known temperatures and the crack density and ineral changes at each temperature are determined using scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) analysis. These results then serve to calibrate the cracking and mineralogical behaviors of serpentinite replica moulds used in controlled casting experiments during phase II. Metallography on several phase II cast objects provides additional information on heat flow through the stone. In phase III, the protocol is modified appropriately for the non-destructive study of four archaeological moulds using x-ray diffraction (XRD), x-ray fluorescence (XRF), and SEM. The applicability of the protocol to other stone and ceramic materials is discussed.
by Katherine K. Biçer.
S.M.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.
Includes bibliographical references (leaves 241-249). Also available in electronic version. Access restricted to campus users.

This dissertation contains research directed at investigating the behavior and properties of a class of composite materials known as phononic crystals. Two categories of phononic crystals are explicitly investigated: (I) elastic phononic crystals and (II) nano-scale phononic crystals. For elastic phononic crystals, attention is directed at two-dimensional structures. Two specific structures are evaluated (1) a two-dimensional configuration consisting of a square array of cylindrical Polyvinylchloride inclusions in air and (2) a two-dimensional configuration consisting of a square array of steel cylindrical inclusions in epoxy. For the first configuration, a theoretical model is developed to ascertain the necessary band structure and equi-frequency contour features for the realization of phase control between propagating acoustic waves. In contrasting this phononic crystal with a reference system, it is shown that phononic crystals with equifrequency contours showing non-collinear wave and group velocity vectors are ideal systems for controlling the phase between propagating acoustic waves. For the second configuration, it is demonstrated that multiple functions can be realized of a solid/solid phononic crystal. The epoxy/steel phononic crystal is shown to behave as (1) an acoustic wave collimator, (2) a defect-less wave guide, (3) a directional source for elastic waves, (4) an acoustic beam splitter, (5) a phase-control device and (6) a k-space multiplexer. To transition between macro-scale systems (elastic phononic crystals) and nano-scale systems (nano-phononic crystals), a toy model of a one-dimensional chain of masses connected with non-linear, anharmonic springs is utilized. The implementation of this model introduces critical ideas unique to nano-scale systems, particularly the concept of phonon mode lifetime. The nano-scale phononic crystal of interest is a graphene sheet with periodically spaced holes in a triangular array. It is found through equilibrium molecular dynamics simulation techniques, that phonon-boundary collision effects and coherent phononic effects (band-folding) are two competing scattering mechanisms responsible for the reduction of acoustic and optical phonon lifetimes. Conclusions drawn about the lifetime of thermal phonons in phononic crystal patterned graphene are linked with the anharmonic, one-dimensional crystal model.

Modernization has brought about steady increase in the consumption of goods and services by human societies across the globe, which mostly driven by both population growth and the change of individual living standards. This, of course, leads to an ever-increasing waste production that ends up in landfills and very often as a source of pollution on natural ecosystems, especially in the low and middle-income countries where waste management is almost inexistent. The management of waste streams is a huge challenge for developed countries as well, where societal and environmental impacts are visible despite massive investments in waste management. One of the most problematic waste materials is plastic, which can remain in nature for over 100 years without degradation, leading to serious environmental concerns. As one of the most significant innovations of the 20th century, plastic is a widely used and cost-effective material for many applications. After their useful lifetimes, their management is problematic. Thus, robust and innovative approaches of managing such waste material are needed in order to mitigate the problem. One of the innovative approaches of tackling the menace cause by plastic waste is through its incorporation into the construction materials. This thesis seeks to address this problem by exploring the use of melted plastic wastes (High Density Poly Ethylene, HDPE and Low Density Poly Ethylene, LDPE) as binder in developing new construction materials (mortar with melted plastic as the only binder, MPB and Plastic Waste Crete, PWC) as an alternative to partially replace traditional concrete and mortar, or finding other engineering uses for this type of waste. Worldwide, about 190 m3 of concrete is poured every second, which translates to 6 billion m3 per year and making it, one of the most widely used manufactured materials. However, the production of concrete requires water and cement. Cement is expensive, and its production contributes to the emission of environmentally polluting gases. Replacing this binding element with recycled plastic derivatives would have significant economic and environmental benefits. In addition to the elimination of cement cost, this will result in water savings, which is especially important for areas without fresh water scarcity. Some researchers have used plastics in concrete and mortars as additives and/or replacement for fine and coarse aggregates. In addition, different types of plastics have been used in bitumen as an additive to reduce construction cost and improve sustainability by adding value to wastes materials. However, there is paucity of technical information about the use of the melted HDPE and LDPE plastic wastes as the only binding phase in concrete- or mortar-like materials. Moreover, many parameters such as preparation conditions, field variables, constituent elements, and final applications have impacts on the performance of construction materials Thus, the key objective of this PhD research is to develop the mortar with plastic binder (MPB) and PlasticWasteCrete (PWC) by using molten HDPE and LDPE plastic wastes as the only binder as well as to investigate the engineering properties of these new types of construction materials. The plastic contents of 45%, 50%, 60% and 65% and HDPE to LDPE ratios of 40/60, 50/50, and 60/40 were selected for the experimental tests. Clean river sand was used as the only aggregate for the MPB, while both sand and gravel were used for the PWC. Various tests were then performed on prepared MPB and PWC samples at different curing times from early to advanced ages to assess their engineering properties. These tests were conducted in accordance with the ASTM standards to evaluate the mechanical properties (compressive strength and splitting tensile strength), permeability and density of the MPB and PWC materials. Additional tests were carried out to analyze the products at the microstructural level (optical microscope, SEM, MIP and thermogravimetric analysis) to gain an insight into the microstructural properties of the developed materials and how that affect their engineering properties. The compressive strength tests revealed the optimal plastic content for the MPB and PWC with the best strength performance. The average compressive strength values for various optimal formulations after 28 days were found to be in the range of 9 to 18 MPa. The splitting tensile strength for the new materials from 1 to 28 days of curing time, were found to be between 1 and 5 MPa. The average hardened density of the MPB and PWC is about 2 g/cm3, which makes them lightweight material according to RILEM classification. In addition, various absorption tests (capillary and immersion) were performed on different MPB and PWC samples, and the obtained results showed that they are porous materials having lower rate of absorption than the traditional cementitious materials (mortar, concrete). This observation was supported by the results from both MIP and SEM analyses. Finally, thermogravimetric analysis provided interesting details on the thermal decomposition of the new materials, with significant changes or mass loss for these products being observed only at temperatures higher than 300°C. The findings from this study suggest MPB and PWC made with melted plastic waste as the only binder have a promising potentials for use in construction. The research conducted in this PhD study offers a good understanding of the engineering properties of the materials as well as the optimal formulations that yield best performance in terms of strength and durability. In summary, it provides useful technical information and tools on the MPB and PWC that will contribute in setting guidelines on the optimal applications of these products in the field of construction in order to have safe, durable and cost-effective structures. Résumé Avec la modernisation de nos sociétés, les habitudes ont considérablement changé, ainsi, on observe une forte consommation des biens et services, due à l’augmentation de la population et l’amélioration de leurs conditions de vie. Ce qui conduit à une augmentation considérable des quantités des déchets qui terminent leurs cycles au niveau des décharges ou dans les océans/fleuves devenant ainsi une source de source de pollution des écosystèmes naturels, surtout dans les pays à revenu faible et intermédiaire avec des systèmes défaillants ou moins performants de gestion des déchets. La gestion des flux de déchets est aussi un défi pour certains pays développés, où les impacts sociaux et environnementaux sont visibles en dépit des investissements massifs dans ce secteur. Parmi ces déchets, nous avons les plastiques, l’une des innovations du 20e siècle avec des qualités versatiles et coût faible, se trouve partout dans nos vies quotidiennes. Après leur utilisation, les plastiques deviennent des déchets qui peuvent rester dans la nature plus de 100 ans sans aucune dégradation, avec des conséquences néfastes sur l’Homme et l’environnement. Ainsi, une approche robuste et innovante de gestion de ces déchets est nécessaire afin d'atténuer leurs impacts. L'une des approches innovantes pour réduire l’impact causé par les déchets plastiques consiste à les incorporer dans les matériaux de construction. Ainsi, le problème est abordé dans cette thèse en développant des technologies permettant de recycler les plastiques fondus comme liant dans les nouveaux matériaux de construction (MPB et PWC), afin d’offrir une alternative pour remplacer partiellement le béton / mortier traditionnel. Le béton est l’un des matériaux les plus utilisés au monde, avec environ 190 m3 coulés chaque seconde, correspondant à 6 milliards de m3 par an. Cependant, la production de béton nécessite de l'eau et du ciment. Le ciment coûte cher et sa production contribue à l'émission de gaz polluants l'environnement. Le remplacement d'une partie du béton traditionnel par un matériau à base des déchets plastique aura des avantages économiques, sociaux et environnementaux importants. Allant dans ce sens, certains chercheurs ont utilisé les plastiques dans le béton et le mortier comme additifs et / ou substituts des matériaux granulaires tels que le sable et le gravier. Aussi, différents types de plastiques ont été utilisé dans le bitume comme additif pour réduire les coûts de construction et améliorer la durabilité, ainsi contribuer à donner de la valeur aux déchets. Cependant, jusqu'à présent, il existe peu d’informations techniques sur l'utilisation de déchets plastiques (HDPE et LDPE) fondus comme seuls liants pour développer de nouveaux types de matériaux de construction. En plus, plusieurs facteurs (les conditions de préparation, les éléments constitutifs, les applications finales, etc.) ont un impact sur les caractéristiques des matériaux de construction. Ainsi, l'objectif de cette recherche doctorale est de développer des nouveaux matériaux de construction (MPB et PWC) en utilisant les déchets plastiques fondus (HDPE et LDPE) comme seul liant, puis déterminer les propriétés caractéristiques de ces matériaux afin de trouver la formulation optimale conduisant à la meilleure résistance. En plus de l'élimination du coût du ciment, cette technologie permet aussi de faire des économies d'eau, bénéfique surtout pour les zones avec des difficultés d'accès à l’eau potable. Cela contribuera à la réduction des coûts de la construction en utilisant les produits innovants comme alternative au béton / mortier conventionnel. Un vaste programme expérimental, comprenant des tests à petite et grande échelle, a été développé afin d'atteindre les objectifs de cette étude de doctorat. La campagne expérimentale a comporté différentes étapes comprenant la sélection des matériaux, la détermination de la formulation optimale et les conditions appropriées pour la préparation des matériaux susmentionnés. Par la suite, pour une meilleure compréhension du comportement technique et des propriétés du produit final, divers tests ont été effectué sur les matériaux préparés à différents temps de durcissement. Ces tests ont été menés conformément aux normes ASTM pour évaluer les propriétés mécaniques (résistance à la compression et à la traction), la perméabilité et la densité des nouveaux matériaux. Les expériences ont été approfondies en analysant les produits au niveau microstructural (microscope optique, SEM, MIP et analyse thermique) pour avoir un aperçu des propriétés microstructurales des matériaux développés et essayer de comprendre les relations avec leur comportement mécanique. Les essais de compression ont permis de trouver la teneur en plastique optimale pour les matériaux (MPB et PWC) avec les meilleures valeurs de résistance. Les résistances moyennes à la compression à 28 jours pour diverses formulations étaient comprises entre 9 et 18 MPa. La résistance à la traction par fendage des nouveaux matériaux entre 1 et 28 jours se situait entre 1 et 5 MPa. La densité moyenne du béton et mortier écologique est proche de 2 g / cm3, ils peuvent donc être considérés comme des matériaux légers selon la classification RILEM. De plus, divers tests d'absorption (capillaire et par immersion) ont été réalisé sur différents échantillons de MPB et PWC, les résultats obtenus ont montré qu'il s'agit de matériaux poreux ayant un taux d'absorption plus faible que les matériaux traditionnels contenant du ciment. Plusieurs analyses microstructurales ont été réalisées sur différents échantillons des nouveaux produits (MPB et PWC) et les matériaux cimentaires traditionnels ont été utilisés pour renforcer notre compréhension. Enfin, l'analyse thermique a fourni des détails intéressants sur la décomposition thermique de ces nouveaux matériaux ; des changements significatifs avec une perte de masse considérable ont été observés seulement pour des températures supérieures à 300 ° C. Les résultats de ces essais permettent d'acquérir une bonne compréhension des propriétés techniques des nouveaux matériaux (MPB et PWC) ainsi que de déterminer les teneurs optimales en plastique conduisant aux meilleures performances en termes de résistance et de durabilité. Ainsi, les recherches menées dans cette étude de doctorat fournissent des informations techniques et des outils utiles sur le MPB et le PWC; et contribueront à installer des bases pour guider les applications optimales de ces nouveaux produits dans le domaine de la construction afin d'avoir des structures sûres, durables et rentables.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Michaels, Thomas; Committee Co-Chair: Michaels, Jennifer; Committee Member: Degertekin, Levent; Committee Member: Qu, Jianmin; Committee Member: Ruzzene, Massimo; Committee Member: Scott, Waymond. Part of the SMARTech Electronic Thesis and Dissertation Collection.

In this thesis we investigate concepts associated with aggregation. The basic idea of aggregation is that there exists a reduced order model such that, for an appropriate initial condition, the trajectories of the reduced-order model are linear combinations of the trajectories of the ful 1-order model. We study systems which do not aggregate exactly, but which "nearly aggregate". It is shown that for "nearly aggregable" systems there exists a reduced-order model such that, for an appropriate initial condition, the trajectories of the reduced-order model are near a linear combination of the trajectories of the full-order model. Under certain conditions it has also been shown that near-aggregation is equivalent to near-unobservability (roughly, an invariant subspace close to the null space of C). Here we establish a relationship between near-unobservability and modal measures of observability as suggested by Selective Modal Analysis. With this result we then obtain an upper bound on the norm of the transfer function residue using near-unobservability measures. The Generalized Hessenberg Representation (GHR) and Dual GHR are examined throughout this analysis. It is finally shown that for SISO systems, the residue norm may be expressed in terms of certain parameters of the Dual GHR.
M.S.

Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers. Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness losses) during wet/dry cycling. SCMs have been found to be effective in mitigating composite degradation through several processes, including a reduction in the calcium hydroxide content, stabilization of monosulfate by maintaining pore solution pH, and a decrease in ettringite reprecipitation accomplished by increased binding of aluminum in calcium aluminate phases and calcium in the calcium silicate hydrate (C-S-H) phase.

Ionic liquids (ILs) have made a great impact on materials science and are being explored for potential applications in several disciplines. In this article, we briefly highlight the current state-of-the-art techniques employing ILs as new crystallisation media, working as neutral solvent, template or charge compensating species. The use of an IL as environmental friendly solvent offers many advantages over traditional crystallisation methods. The change from molecular to ionic reaction media leads to new types of materials being accessible. Room temperature ILs have been found to be excellent solvent systems for the crystallisation of a wide range of substances and morphologies ranging from nanoscopic crystals to micro- and even to macroscopic crystals. Moreover, high temperature routes, such as crystallisation from melts or gas phase deposition, have been replaced by convenient room or low temperature syntheses, employing ILs as reaction media
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

Ionic liquids (ILs) have made a great impact on materials science and are being explored for potential applications in several disciplines. In this article, we briefly highlight the current state-of-the-art techniques employing ILs as new crystallisation media, working as neutral solvent, template or charge compensating species. The use of an IL as environmental friendly solvent offers many advantages over traditional crystallisation methods. The change from molecular to ionic reaction media leads to new types of materials being accessible. Room temperature ILs have been found to be excellent solvent systems for the crystallisation of a wide range of substances and morphologies ranging from nanoscopic crystals to micro- and even to macroscopic crystals. Moreover, high temperature routes, such as crystallisation from melts or gas phase deposition, have been replaced by convenient room or low temperature syntheses, employing ILs as reaction media.
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

The theme of the diploma thesis is the study of physical properties of various building materials in buildings in low-energy construction. The work is mainly focused on the influence of the thermal accumulation properties of building materials used in buildings in order to achieve low energy consumption for heating. The thesis compares the energy characteristics of five different constructional material variants of the house.

Cette thèse comprend deux parties : Détermination des contraintes résiduelles dans les composites stratifiés ±θ induites par le cycle thermique de fabrication et Etude de leurs influences sur le com-portement mécanique de ces stratifiés. Limitée par la théorie actuelle, la détermination expérimentale des contraintes résiduelles dans les stratifiés ±θ a été très difficile. Dans notre étude, la méthode du trou incrémental a été employée afin de relaxer les contraintes résiduelles et les déformations provoquées ont été mesurées par les jauges de déformation. Une nouvelle approche proposée dans cette thèse permet d’associer les déformations autour du trou et les contraintes résiduelles au sein du stratifié ±θ. Les coefficients de calibration ont été déterminés par la simulation numérique. Grâce à l’approche développée, nous avons constaté une relation linéaire entre les contraintes résiduelles et l’angle θ du stratifié [02/θ2]s. En adaptant un modèle thermoélastique du matériau, les résultats expérimentaux ont pu être modélisés numériquement. Ensuite, nous avons étudié l’influence de l’épaisseur du stratifié, du cycle de cuisson et du vieillissement hydrothermique sur la distribution des contraintes résiduelles. A l’aide de la technique d’émission acoustique, les influences des contraintes résiduelles sur l’endommagement et le comportement mécanique des stratifiés ont été étudiées grâce aux essais de traction. Enfin, l’importance des contraintes résiduelles sur la rupture transversale du stratifié a été mise en évidence en comparant avec les résultats théoriques
This thesis work consists of two main parts: Deter-mination of residual stresses in composites laminates ±θ, introduced by the thermal cycle during the manufacturing process of laminates and Study of their influences on the mechanical behavior of these laminates. Limited by the current theory, the exper-imental determination of residual stresses in the laminates ±θ was very difficult. In this work, the incremental hole drilling method was performed for the residual stresses relaxation and then the gener-ated strains around the hole were measured with strain gages. The new approach proposed in this thesis allows associating the strains around the hole and the residual stresses in the laminates ±θ. The calibration coefficients were determined by the numerical simulation. With this approach, we found a linear relationship between the residual stresses and the fiber orientation angle θ for the composite laminates [02/θ2]s. By adapting a thermoelastic ma-terial model, the results obtained by our new ap-proach were modelized by the numerical study. Then we studied the influence of laminate thickness, curing cycle and hydrothermal ageing on the distri-bution of residual stresses. With the help of acoustic emission technique, the influences of the residual stresses on the damage and the mechanical behavior of composite laminates were studied through tensile tests. Finally, the importance of the residual stresses on the transverse failure of composite laminates was demonstrated comparing with the theoretical results

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

Orientadores: Luísa Andréia Gachet Barbosa, Rosa Cristina Cecche Lintz
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia
Made available in DSpace on 2018-08-24T22:32:15Z (GMT). No. of bitstreams: 1 Angelin_AndressaFernanda_M.pdf: 3316470 bytes, checksum: e0844bd6dbe8b1d62eefa5eec0498b83 (MD5) Previous issue date: 2014
Resumo: A busca por materiais alternativos, de baixa massa específica, que possua redução na transferência de propagação de calor, associado à facilidade de manuseio e aplicação em concretos estruturais e estruturas de vedação, representa grande desafio na formulação e conhecimento do desempenho dos concretos leves. O concreto leve possui tecnologia pouco difundida em nível nacional e surge no cenário atual como um material inovador e alternativo ao concreto convencional. Frente ao exposto, este trabalho estudou concretos leves estruturais elaborados com duas graduações distintas de argila expandida e, com a finalidade de promover à manutenção das propriedades mecânicas, adicionou-se aditivo superplastificante e sílica ativa. Desenvolveu-se cinco traços distintos, que apresentaram reologia adequada, sem apresentar fenômenos de segregação e exsudação. Estudou-se algumas propriedades físicas, como índice e perda de consistência, absorção de água e massa específica do estado fresco e endurecido, os quais apresentaram uma média de 2000 kg/m3, classificando os concretos, de acordo com o ACI 213R-03 (2003), como leves. As principais propriedades mecânicas analisadas foram, resistência à compressão, apresentando, em média, 40 MPa, valor acima do mínimo prescrito pela ABNT NBR 6118:2007, para concretos estruturais, além da resistência à tração e módulo de elasticidade, as quais serviram como fundamentação na qualificação dos concretos leves estruturais, visando às exigências técnicas nacionais e internacionais para sua classificação e uso. Também foram realizados ensaios de condutividade térmica, por meio do método da placa quente protegida ("Hot Plate"), os quais apresentaram bons resultados, mostrando-se adequados no quesito desempenho térmico, de acordo com a revisão bibliográfica, bem como, com a norma nacional de desempenho térmico (ABNT NBR 15220:2005). Foram obtidas informações microestruturais sobre a zona de transição entre os agregados, convencionais e leves, e sua matriz de cimento. Foram realizadas comparações entre a massa específica seca e a resistência à compressão, assim como, comparações entre a massa específica seca e o módulo de elasticidade, sendo que tais resultados comprovam a possibilidade da utilização do concreto leve em elementos estruturais. Sugere-se, então, utilizar este concreto em painéis de vedação, pois associa-se a baixa massa específica, o conforto térmico e a resistência mecânica
Abstract: The search for alternative materials, low density, having reduced transfer of heat propagation, combined with ease of handling and application in structural concrete and seal structures, constituting a major challenge in the design and understanding of the performance of lightweight concrete. The lightweight concrete technology has little known at the national level and in the current scenario emerges as an innovative and alternative material to conventional concrete. Based on these, this paper studied structural lightweight concrete made with two different grades of expanded clay, and with the purpose of promoting the maintenance of the mechanical properties was added superplasticizer and silica fume. Developed five distinct traits, which showed adequate rheology, without presenting phenomena of segregation and oozing. We studied some physical properties, such as loss of consistency index, water absorption and density of fresh and hardened, which had an average 2000 kg/m3, classifying the concrete according to ACI 213R-03 (2003), as light. The main mechanical properties were analyzed, compressive strength, with an average of 40 MPa, above the minimum prescribed by ABNT NBR 6118:2007, structural concrete, beyond the tensile strength and modulus of elasticity, which served as the basis the qualification of structural lightweight concrete, aimed at national and international technical requirements for classification and use. Thermal conductivity tests were also carried out by means of the hot plate protected ("Hot Plate") method, which showed excellent results, proving to be adequate thermal performance in the category, according to the literature review, as well as with the national standard for thermal performance (ABNT NBR 15220:2005). Microstructural information on the transition zone between aggregates, conventional and light, and its cement matrix were obtained. Comparisons between dry density and compressive strength as well as comparisons between the dry density and modulus of elasticity were performed, and these results show the possibility of using lightweight concrete in structural elements. Then it is suggested to use this concrete fence panels, as is associated with low density, thermal comfort and strength
Mestrado
Tecnologia e Inovação
Mestra em Tecnologia

Increasing demand for new progressive construction materials requires development of modern environmentally friendly materials with excellent end-use properties and reasonable price. One of the main objectives of material research in building industry is using renewable resources of raw materials of industrial waste for development of new construction materials. Current trend of thermal insulation of building constructions results in development of environmentally friendly insulation materials based on renewable material resources from agriculture and stock farming, which could became alternative for current common use insulation materials in the future. The thesis describes research and development of insulation materials based on natural fibres of agricultural origin; in particular fibres of hemp, flax and jute. Hydrothermal behavior of developed materials is studied including computational simulation of behavior of researched materials after building in the construction.