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Low-density cellular solids have demonstrated superior mechanical properties as well as multifunctional characteristics, which may provide a basis for the development of novel structured materials. In particular, cellular solids offer great design flexibility, owing to their topology, which can provide desired functionalities via targeted geometric design and proper selection of the constituent material. While stochastic configurations such as metallic foams have proven to be effective for both thermal insulation and mechanical-energy absorption, the topology of deterministic architectures is not constrained by physical processes. This allows for a variety of configurations to be tailored to simultaneously fulfill disparate tasks. An additional aspect of deterministic cellular structures is the possibility of assembling materials or structures by the spatial repetition of a unit cell. The resulting periodicity of such systems simplifies the characterization of physical properties, which can be established by analyzing the unit cell only, and will provide new opportunities in the fields of structural dynamics, where periodicity-induced impedance leads to the control of both constructive and destructive interference on propagating waves. The objective of this work is to investigate the application of the chiral cellular topology for the design of novel macrostructural, mesostructural and microstructural configurations. A truss-core airfoil, and a truss-core beam are employed as a basis to demonstrate both large-displacement capabilities within the elastic regime of the constituent material, as well as operational deflection shapes with localized dynamic deformations. Large deformation capabilities and unique operational deflection shapes are to be attributed to the unusual deformation mechanism of the chiral lattice. Mesostructural and microstructural configurations, on the other hand, are characterized by an unique mechanical behavior, complex geometry, as well as geometric design flexibility to control both static and dynamic phenomena. The propagation of elastic waves, moreover, is characterized by significant band-gap density as well as strong energy focusing dependent on frequency and wavenumber. These features suggest the chiral topology as a basis for the development of acoustic meta-materials.

Shape memory polymer (SMP) materials have the ability to remain in a deformed state and then recover their initial/cast shape. This property has significant potential in many different fields, including aerospace and bio-medical, in which a shape change is desirable and actuation may not be required. SMP materials have been made into nano-reinforced composites and also foamed to improve desired properties for specific applications. SMP foams offer two clear advantages over non-foam SMP materials in applications for the biomedical and aerospace fields. The key advantages are lower density and significant compressibility. The significance of this is that components made out of SMP foam are lighter than traditional SMP materials, more compressible and exhibit minimal transverse change during deformation and shape recovery. This increases the performance and efficiency of devices using SMP foam material. The need for a set of design criteria, models, and limits for the use of shape memory polymer foams was proposed. The effect of temperature and strain on the mechanical behavior, compression, tensile, cyclic compression, constrained recovery and free strain recovery of the material was used to determine the operational limits of the material. Next, the damage mechanism and viscoelastic effects in compressive cycling were determined through further mechanical testing and with the incorporation of three dimensional structure mapping via micro-CT scanning. The influence of microstructure was determined by testing the basic thermomechanical, viscoelastic and shape recovery behavior of foams with relative densities of 20, 30 and 40 percent. A similar suite of tests was then performed on the base epoxy material to generate the material properties necessary to fit constitutive equations to enable computational modeling. This data was then combined with three dimensional microstructures generated from micro-CT scans to develop material models for shape memory foams. These models were then validated by comparing model results to the experimental results under similar conditions.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 152-167).

Con la finalidad de lograr la estabilización de pavimentos, surgen nuevas tecnologías de agentes estabilizadores como el asfalto espumado y la emulsión asfáltica. En el Proyecto del corredor vial Dv-Humajalso-Desagüadero y Tacna-Capazo-Mazocruz, se tenía como solución técnica aplicar en el Tramo 7 Tarata-Capazo el asfalto espumado. Sin embargo, la condición termodinámica es fundamental para el asfalto espumado y esto se evidencia en el Tramo 7, donde a temperaturas de 5°C en descenso, las partículas de asfalto no se dispersan sobre el mástic, éstas caen sobre otras partículas de asfalto, provocando una aglomeración de asfalto en forma de chicles e imposibilitando la compactación de la capa del pavimento. Frente a esta problemática, se plantea estabilizar el material granular con emulsión asfáltica, donde las partículas de asfalto están dispersas en una solución acuosa a 25°C y no se requiere calentar al asfalto a elevadas temperaturas. El objetivo de la tesis es lograr la estabilización del pavimento utilizando emulsión asfáltica. Para el diseño de la mezcla asfáltica en frío, se utiliza la metodología Illinois y una emulsión catiónica de rotura lenta como ligante. Prosigue, el diseño del pavimento con la metodología AASHTO 93, para determinar los espesores de las capas del pavimento que satisfarán las cargas de tráfico para la vida útil del proyecto. Finalmente, se logra validar la estabilización del pavimento en campo con los controles de compactación y deflectometría, quedando demostrado la versatilidad de la emulsión como mezcla asfáltica en frío frente a las condiciones termodinámicas críticas del Proyecto. / In order to achieve the stabilization of pavements, emerge new technologies of stabilizing agents such as foamed bitumen and asphalt emulsion. In the Roadway Project Dv-Humajalso-Desagüadero and Tacna-Capazo-Mazocruz, the technical solution was to apply foamed bitumen in road Section 7 Tarata-Capazo. Thermodynamic condition is fundamental where foamed bitumen is evidenced in Section 7, the temperature is lower than 5 °C, so the asphalt don’t disperse on the Mastic, causing an agglomeration of asphalt in the form of chewing gum and making impossible the compaction of the pavement layer. In this problem, It’s proposed to stabilize the granular material with asphalt emulsion, so the asphalt particles are dispersed in a solution to 25°C. The technique is a mixture of cold asphalt and is feasible for the critical thermodynamic conditions of the Section 7 Tarata-Capazo. The objective is to achieve the stabilization of the pavement using asphalt emulsion. The design of the cold asphalt mix applies the Illinois Methodology to determine the optimum quantity of residual asphalt. So that, the design of the pavement is done with the methodology of AASHTO 93, which allows to determine the thicknesses of the pavement layers that will satisfy the serviceability and traffic for the useful life of the project. Finally, It´s possible to validate the stabilization of the pavement in the field with the compaction and deflectometry controls, demonstrating the versatility of the emulsion as a cold asphalt mixture against the critical thermodynamic conditions of the Project. / Tesis

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The pavement construction industry aims to reduce its Greenhouse Gas (GHG) emissions by investigating various energy efficient practices. The industry has focused on reducing energy consumption by producing Warm Mix Asphalt (WMA) surfacing materials that are workable at lower temperatures in relation to Hot Mix Asphalt (HMA), as a means to reduce carbon emissions. Half-Warm Foamed Bitumen Mixtures (HWF) is a relatively new material and is produced at temperatures below 100°C. This translates to large energy savings to overcome the latent heat of steam when exceeding 100°C. The characteristics of HWF mixes are a compromise between those of Foamed Bitumen Stabilised material (BSM-foam) and HMA characteristics. These include to a limited extent the improved tensile strength, particle coating and durability of HMA; and the shear strength of BSM-foam. The use of microwave technology as an efficient heating method to produce improved engineering properties of BSM-foam is proposed in this study. The benefits include energy saving due to its volumetric heating capability as well as rapid heating which improve productivity when using suitable materials. The aspect of recycling material brings forth further energy saving and emissions reduction when reusing materials. The portability of the in-plant recycling machines is an ideal candidate with logistical advantages to implement microwave generators to produce HWF mixes. This study is subdivided into four parts as it progressively investigates the potential to heat aggregates and produce HWF material. Firstly it investigates the heating potential of four aggregates, namely Hornfels, Quartzite, Eucrite, Granite and Reclaimed Asphalt (RA) at various moisture contents using a microwave apparatus. The second part discusses the thermodynamics of the preliminary investigation to provide insight into the third part, the Primary Investigation. The primary investigation evaluates the tensile strength and shear properties of two material blends by respectively implementing Indirect Tensile Strength (ITS) and monotonic triaxial tests on specimens. The two blends were a combination of RA and crushed hornfels. The fourth and final part evaluates the HWF properties in relation to those of the equivalent BSM-foam product by means of a pavement analysis. The highest laboratory production temperature achieved was depicted by the material properties, microwave power capability and production rates. This temperature was consistently recorded at 50°C which theoretically simulates an in-field production rate of approximately 25 tons per hour. ITS test results indicate 100% increase in tensile strengths and an increase in compaction density for the HWF mixes. Large reduction in moisture contents is also observed after curing in relation to BSM-foam. The benefits in improving a layer within a pavement structure have an effect on the pavement’s overall performance. This could assist in reducing the requirement for premium layers e.g. thickness of HMA within the structure, thereby further assisting energy conservation. The evaluation of the microwave heated HWF mixes can be considered economical if designed with a purpose to meet the thermal dynamic requirements of a material considering the microwaves volumetric potential. / AFRIKAANSE OPSOMMING: Die plaveisel konstruksie-industrie poog om hul kweekhuisgas (KHG) uitskeiding te verlaag deur verskeie energie doeltreffende metodes te ondersoek. Die industrie fokus op die vermindering van energie-verbruik deur middel van die produksie van Warm Mengsel Asfalt (WMA) oppervlak materiale wat werkbaar is in laer temperature in verhouding tot “Hete Mengsel Asfalt (HMA)” as `n metode om koolstof uitskeiding te verlaag. Half-Warm Skuim-Bitumen Mengsels (HWS) is `n relatief nuwe materiaal en word vervaardig onder 100 °C. Dit lei tot groot energie besparings en oorkom sodoende die latente hitte van stoom wanneer temperature van 100 °C oorskry word. Die karakter-eienskappe van HWS mengsels is `n kompromie tussen Skuim-Bitumen Gestabiliseerde materiaal (BSM-S) en HMA eienskappe. Dit sluit tot `n beperkte mate in die verbeterde spankrag, partikel bestryking; en die skeer krag van BSM-S. Die gebruik van mikrogolf-tegnologie as effektiewe verwarmingsmetode vir verbeterde ingenieurseienskappe van BSM-S word voorgestel in hierdie studie. Die voordele sluit in energie besparing as gevolg van die volumetriese verwarmingsvermoë sowel as snel verhitting wat produktiwiteit verbeter tydens die gebruik van gepaste materiale. Die gebruik van herwinde materiaal bring verdere energiebesparing en uitskeiding-vermindering mee. Die draagbaarheid van binne-aanleg herwinningsmasjinerie is ‘n ideale kandidate met logistieke voordele vir die installering van mikrogolf-opwekkers vir die produsering van HWS mengsels. Dié studie word onderverdeel in vier dele terwyl dit toenemend ondersoek instel na die potensiaal van hitte versameling asook die produksie van HWS stowwe. Eerstens ondersoek dit die verwarmingspotensiaal van vier versamelings naamlik horingsteen, kwartsiet, eukrite, graniet en Herwinde Asfalt (HA) teenoor verskeie vogskattings-mikrogolf aperate. Die tweede deel bespreek die termodinamika van die voorlopige ondersoek om insig te bied vir die derde deel, die primêre ondersoek. Die primêre ondersoek evalueer die rekbaarheid en skeereienskappe van twee materiaal-mengsels van ITS en monotoniese drieassige toetse onderskeidelik op verskillende monsters. Die twee mengsels was `n kombinasie van HA en gemaalde horingsteen. Die vierde en finale deel evalueer die HWS eienskappe in verhouding tot die van die ekwivalente BSM-S produk deurmiddel van `n sypad-analise. Die hoogste laboratoriumproduksie temperature wat bereik was, was uitgebeeld deur die materiaal-eienskappe, mikrogolf krag kapasiteit en produksiekoers. Hierdie temperature was deurlopend aangeteken teen 50 °C wat `n teoretiese voorstelling is van `n binneveld produksie tempo van ongeveer 25 ton per uur. ITS toets resultate wys `n 100 % verhoging in spankrag asook `n toename in kompakte vir die HWS mengsels. Groot afname in voginhoud is ook waargeneem na bewerking in verhouding tot BSM-S. Die voordeel verbonde aan die verbetering van `n lag binne `n plaveisel-struktuur, het `n impak op die plaveisel se algemene uithoubaarheid. Dit kan bydra tot `n verlaging in die vereiste binne die struktuur en verdere bydra tot energie besparing. Die evaluering van mikrogolf verhitte HWS stowwe kan as ekonomies beskou word wanneer dit doelgerig vervaardig word om te voldoen aan die termodinamika vereistes van `n materiaal, wanneer die mikrogolf volumetriese potensiaal in ag geneem word.

A reciclagem profunda com espuma de asfalto tem sido uma alternativa de sucesso para a restauração de pavimentos degradados. Em relação às soluções tradicionais de reabilitação, como os recapeamentos, tem a vantagem de proporcionar a correção de defeitos em camadas inferiores, com a manutenção ou pequena elevação do greide da pista, além de ganhos ambientais, como um menor consumo de materiais virgens da natureza e redução do volume de material descartado. Entretanto, no Brasil não há método para dimensionamento estrutural para esta tecnologia, o que dificulta seu emprego. Para o desenvolvimento de um procedimento de dimensionamento que contemple este tipo de solução, foram estudados métodos presentes na bibliografia internacional: guia da AASHTO de 1993 e Caltrans, dos EUA, TRL386 e TRL611, da Inglaterra, as duas versões do guia sul-africano TG2 e os métodos oriundos do Austroads, tanto o procedimento interino de 2011 como adaptações de órgãos da Austrália e Nova Zelândia. Observou-se divergência de opiniões quanto ao comportamento do material reciclado com espuma de asfalto. Alguns órgãos e autores consideram o comportamento do mesmo mais próximo às misturas asfálticas, sendo o mecanismo de falha o trincamento, e outros o definem como semelhante a um material granular modificado com alta coesão e ruptura devido às deformações permanentes. Correlaciona-se tal associação ao teor de espuma usualmente utilizado nas obras rodoviárias. Outros aspectos que se destacam para este tipo de base são o ganho de resistência ao longo do tempo devido à cura, mesmo com início da operação da rodovia e a importância da infraestrutura remanescente no dimensionamento. Tais fatos foram corroborados pelos estudos de caso e resultados do trecho experimental construído na Rodovia Ayrton Senna - SP 070, monitorado por meio de ensaios deflectométricos com FWD durante um ano. Como resultado do trabalho, foi proposto um procedimento para o dimensionamento estrutural de pavimentos com camadas recicladas a frio com espuma de asfalto utilizando dados deflectométricos que atende o método do Manual de Pavimentação do Departamento Nacional de Infraestrutura de Transportes (DNIT) e incorpora diferentes aspectos na análise mecanicista. Outras conclusões são a viabilidade técnica a longo prazo da solução mencionada e a importância do controle tecnológico, com ênfase para o monitoramento deflectométrico nos primeiros meses de operação do pavimento para averiguar a evolução da cura do material. / Full-depth pavement reclamation with foamed asphalt has been a successful alternative for the rehabilitation of degraded pavements. In relation to the traditional rehabilitation methods, such as overlays, it has the advantage of provide the correction of the lower layer\'s defects considering the maintenance of the road grade or slight increase of it. Besides that, there are environmental gains, with less consumption for virgin materials and reduction of discarded material volume. However, in Brazil there is no structural design method for this technology, which hinders its use. To develop a design procedure which includes this kind of solution, several international methods were studied, like AASHTO (1993) and CALTRANS, from the USA; TRL386 and TRL611, from England; TG2 guide, from South Africa; and methods derived from the Austroads were studied, both, the interim procedure 2011 and local departments adaptations from Australia and New Zealand. There are divergent opinions of the behavior of the recycled material with foamed bitumen. Some agencies and authors consider the behavior of it similar to the asphalt mixtures, and the failure mechanism cracking due to fatigue. Others define it as similar to modified granular material with high cohesion and disruption due to permanent deformation. Such association is related to the foamed asphalt content usually used in road works. Other aspects that stand for such basecourse material are the gain of strength over time due to cure, even with the beginning of the highway operation and the importance of the remaining pavement\'s layers in design process. These facts were corroborated by case studies and results of the test section built in Ayrton Senna Highway - SP 070, which was monitored through falling weight deflectometer (FWD) measurements for a year. As result of this work, it is proposed a procedure for the structural design of cold recycled pavements with foamed asphalt using deflectometer data that meets the method of paving manual of the Brazilian National Department of Transport Infrastructure (DNIT). Other findings are the technical long-term viability of that solution and the importance of technological control, with emphasis on the deflection monitoring in early pavement operation to ascertain the evolution of the curing process.

The thermal conductivities of foamed polymer based materials are much lower thermal conductivity values than unfoamed polymeric materials. Especially, thermal conductivity values of foamed polymers with closed-cell structure decreases to 0.03 W/m.K. The reinforcement of foamed polymeric materials by mixing with bitumen lowers the raw material cost. The main objective of this study is to make a new thermal insulation material with low thermal conductance. In this study, the effects of concentration of calcium carbonate as inorganic filler and the effects of cross-linking on the properties foamed and unfoamed ethylene-vinyl acetate (EVA) copolymer based bituminous blends and composites were investigated. Applications such as thermal, mechanical characteristics of foamed and unfoamed EVA based bituminous composites were investigated. Foamed EVA based bituminous composites were prepared by using Brabender Plastic Coder, PLV 151. Mixing was made at 120 &ordm / C at 60 rpm for 15 minutes. The prepared blends were molded by a technique called Hand Lay-up Self-expanding Batch Molding (HLUSEBM) which was firstly applied by our group. The molding temperature was 170 &ordm / C at which chemical blowing agent and cross-linking agent decomposes. According to test results, at moderate chemical blowing agent and EVA content, the best closed-cell structure with high porosity and low thermal conductivity values were obtained. The compressive properties of foamed polymer based bituminous composites (FPBBCs) increase with increasing CBA and EVA content. With increasing calcium carbonate and EVA concentration, the porosity of FPBBCs increases but thermal conductivity of them decreases. On the other hand, with increasing filler content but with decreasing EVA concentration elastic modulus of FPBBCs increases but elastic recovery decreases.

Low-density cellular materials, metallic bodies with gaseous voids, are a unique class of materials that are characterized by their high strength, low mass, good energy absorption characteristics, and good thermal and acoustic insulation properties. In an effort to take advantage of this entire suite of positive mechanical traits, designers are tailoring the cellular mesostructure for multiple design objectives. Unfortunately, existing cellular material manufacturing technologies limit the design space as they are limited to certain part mesostructure, material type, and macrostructure. The opportunity that exists to improve the design of existing products, and the ability to reap the benefits of cellular materials in new applications is the driving force behind this research. As such, the primary research goal of this work is to design, embody, and analyze a manufacturing process that provides a designer the ability to specify the material type, material composition, void morphology, and mesostructure topology for any conceivable part geometry. The accomplishment of this goal is achieved in three phases of research: Design Following a systematic design process and a rigorous selection exercise, a layer-based additive manufacturing process is designed that is capable of meeting the unique requirements of fabricating cellular material geometry. Specifically, metal parts of designed mesostructure are fabricated via three-dimensional printing of metal oxide ceramic powder followed by post-processing in a reducing atmosphere. Embodiment The primary research hypothesis is verified through the use of the designed manufacturing process chain to successfully realize metal parts of designed mesostructure. Modeling & Evaluation The designed manufacturing process is modeled in this final research phase so as to increase understanding of experimental results and to establish a foundation for future analytical modeling research. In addition to an analysis of the physics of primitive creation and an investigation of failure modes during the layered fabrication of thin trusses, build time and cost models are presented in order to verify claims of the process s economic benefits. The main contribution of this research is the embodiment of a novel manner for realizing metal parts of designed mesostructure.