Grâce au développement des méthodes de mesure de champs, de nouvelles stratégies d’identification de paramètres matériau de lois de comportement mécanique sont proposées, fondées sur l’utilisation d’essais mécaniques hétérogènes. Les champs de déformation hétérogènes développés au cours de ces essais permettent une meilleure caractérisation du comportement mécanique des tôles métalliques et, par conséquent, de réduire considérablement le nombre d’essais nécessaires pour identifier les paramètres matériau de modèles phénoménologiques complexes. Mais comment concevoir ces essais? Dans ce travail, une méthodologie d’optimisation pour le développement d’essais mécaniques hétérogènes est présentée. L’objectif principal est la conception, par analyse inverse et en proposant un indicateur représentatif des états de déformation, d’un essai capable de caractériser le comportement mécanique des tôles métalliques pour plusieurs états de contrainte et déformation. Pour cela, cette étude a été réalisée en considérant un matériau virtuel (acier doux sous forme de tôle mince), obtenu à partir de données expérimentales. En outre, un indicateur qui caractérise les essais mécaniques a été proposé pour être utilisé dans la méthodologie d’optimisation. D’un côté, le comportement mécanique de l’acier doux a été représenté avec un modèle phénoménologique complexe composé du critère anisotrope de plasticité Yld2004-18p, combiné à une loi d’écrouissage mixte et un critère macroscopique de rupture. Pour cette loi de comportement, un procédé d’identification des paramètres du matériau a été développé et le jeu de paramètres identifiés a été validé en comparant des résultats expérimentaux et numériques de l’emboutissage d’un godet cylindrique. D’un autre côté, un indicateur quantitatif pour évaluer l’information du champ de déformation des essais mécaniques a été formulé et sa pertinence a été évaluée à travers l’analyse numérique d’essais classiques et hétérogènes de la littérature. Concernant la méthodologie d’optimisation, deux approches différentes ont été considérées pour la conception de l’essai mécanique hétérogène. La première approche est fondée sur une procédure en une seule étape, où l’optimisation de la forme de l’éprouvette et des conditions aux limites, imposées par un outil, a été effectuée. La seconde approche est fondée sur une technique incrémentale en plusieurs étapes, en optimisant la forme de l’éprouvette et le chemin de déformation, par l’application des déplacements locaux. Les résultats obtenus sont comparés et un essai est retenu pour identifier les paramètres matériau, en utilisant le matériau virtuel comme référence, afin d’illustrer la pertinence de la démarche / With the development of full-field measurements methods, recent material parameters identification strategies call upon the use of heterogeneous tests. The inhomogeneous strain fields developed during these tests lead to a more complete mechanical characterization of the sheet metals, allowing the substantial reduction of the number of tests in the experimental database needed for material parameters identification purposes. In the present work, an innovative design optimization process for the development of heterogeneous tests is presented. The main goal is the design of a mechanical test able to characterize the material behavior of thin metallic sheets under several stress and strain paths and amplitudes. To achieve this aim, the study was carried out with a virtual material, though derived from experimental data. An indicator of the mechanical interest of the test was proposed, and was used in an optimization procedure to design both the boundary conditions and the sample shape. On the one hand, the virtual behavior of a mild steel was characterized using a complex phenomenological model composed by the Yld2004-18p anisotropic yield criterion combined with a mixed isotropic-kinematic hardening law and a macroscopic rupture criterion. An efficient material parameters identification process based on finite element model updating type was implemented and the identified parameters set was validated by performing a deep drawing test leading either to full drawing or rupture of the blank. On the other hand, an indicator which rates the strain field of the experiment by quantifying the mechanical information of the test was formulated. The relevance of the indicator was stressed out by the numerical analysis of already known classical as well as heterogeneous tests and the results obtained were validated by a material parameter sensitivity study. Two different optimization approaches were used for designing the heterogeneous test, namely (i) a one-step procedure designing both specimen shape and loading path by using a tool and (ii) a sequential incremental technique designing the specimen shape and the loading path of the specimen considering local displacements. The results obtained revealed that the optimization approach proposed was very promising for designing a single experiment able to fully characterize the several strain paths and amplitudes encountered in sheet metal forming processes.

O policloreto de vinila (PVC) é comercialmente utilizado em diversas aplicações, destacando-se os filmes flexíveis. Para a fabricação destes compostos de PVC, utilizam-se vários tipos de aditivos, tais como plastificantes, estabilizantes térmicos, lubrificantes, retardantes de chama e outros. No presente trabalho foram produzidos compostos de PVC a partir de uma formulação referencial, variando-se a concentração de pigmento, carga, modificador de impacto e plastificantes. A preparação das amostras foi feita através de uma misturadeira intensiva (Mecanoplast), calandra de 2 rolos e prensa, obtendo-se placas flexíveis de 1 mm de espessura. Os resultados das análises térmicas (DMA e TGA) mostraram que o uso e a quantidade de plastificantes foram os principais fatores que influenciaram as propriedades de mudança de fase (Tg) e estabilidade térmica do material. As análises das propriedades mecânicas (resistência à tração e alongamento) mostraram que estas propriedades foram influenciadas pelas proporções de cargas, modificador de impacto e plastificantes na composição. As medidas elétricas (rigidez dielétrica) não foram afetadas pela variação da adição de materiais nas amostras analisadas / Poly(vinyl chloride) (PVC) is commercially used in several applications, especially in flexible films. Aiming the production of products, PVC can be filled with a variety of additives, like plasticizers, thermal stabilizers, lubricants, flame-retardants and others. In this work PVC compounds were produced based on a known formulation, using different weight ratios for pigment, filler, impact modifier and plasticizers. Samples were prepared through intensive mixing using two rolls calendrer followed by a hot press to form films with 1 mm thickness. Thermal analysis results (DMA and TGA) showed that plasticizers are the most important factors that influenced the material properties such as phase behavior (Tg) and thermal stability. Mechanical properties analysis (breaking strength and elongation) were influenced by fillers, impact modifier and plasticizers proportions used in the composition. Electrical properties (dielectric breakdown strength) were not affected by different weight ratios in the analyzed samples

Ces travaux de thèse portent sur le soudage par friction-malaxage hétérogène entre le titane (Ti grade II) et l'aluminium (Al1050). La recherche est axée sur la configuration de l'assemblage par recouvrement afin de limiter les contraintes pendant le procédé. La méthode de plans d'expérience de Taguchi a permis de déterminer l'influence des paramètres pour une jonction sans défaut. La vitesse de rotation de l'outil a été identifiée comme le paramètre influençant le plus la génération de défauts. Les combinaisons de paramètres sont liées à un coefficient d'apport de chaleur. La différence de conductivité thermique entre les deux matériaux conduit à un gradient thermique dans l'épaisseur jusqu'à 80°C. Aucune optimisation de la résistance mécanique des jonctions n'a été révélée par les tests de traction et de flexion trois points.Des analyses microstructurales ont été réalisées sur la jonction soudée afin de mieux comprendre les propriétés mécaniques. Un seul composé intermétallique TiAl3 se forme dans le volume de titane et assure la continuité chimique de l'interface. D'autres analyses par EBSD (MEB) et par la méthode ASTAR™ (MET) pour les plus petites échelles ont complété les observations. Le processus génère une déformation plastique sévère de l'aluminium qui induit une réduction de la taille des grains avec un gradient suivant l'épaisseur.Toutes les observations ont fournis des moyens pour comprendre le phénomène de soudage par friction-malaxage conduisant à une évolution microstructurale pour réaliser un meilleur lien entre la microstructure finale et les propriétés macroscopiques du cordon de soudure. / These PhD works are about heterogeneous friction stir welding between titanium (Ti grade II) and aluminum (AA1050). Research is focused on lap joining configuration in order to limit the process stress. Taguchi's design of experiments determined parameters influence for a defectless welded junction. The rotational speed of the tool has been identified as the parameter which influences the most the defects generation. Parameters combinations are linked to a heat input coefficient. The thermal conductivity difference between the two material leads to a thermal gradient in the thickness up to 80°C. No junction mechanical strength optimization has been revealed by tensile and bending tests.Microstructural analyses were performed on the welded junction in order to understand the mechanical properties. One single intermetallic compound TiAl3 nucleates in the titanium volume and ensures interface chemical continuity. Further analyses with EBSD (SEM) supplemented by ASTAR™ (TEM) method for the smaller scales have completed the observations. The process generates aluminum severe plastic deformation which induces a grain size reduction with a gradient following the configuration thicknessAll observations brought clues to understand friction stir welding phenomenon leading to microstructural evolution to realize a better link between resulting microstructure and macroscopic properties.

No description available.

Bulk Metallic Glasses (BMGs), also known as amorphous metals, are of considerable scientific and commercial interest due to their random or chaotic structure. Given their potential use as engineering materials, there is a concomitant need to establish their mechanical properties. However, BMGs are not conveniently available in sufficient volumes (especially experimental and combinatorial compositions), making property determination via conventional tensile or compression testing problematic. Instrumented indentation is ideally suited for this purpose because the testing requires only small sampling volumes and can probe multiaxial deformation characteristics at various length scales. In this technique, conducted generally on a sub-micron regime, the depth of penetration of an indenter, usually a diamond, is measured as a function of the applied load and expressed graphically as load (P) - displacement (h) curves from which a host of mechanical properties can be extracted and studied. In this work, a methodology for using instrumented indentation at nano- and micro- scales to determine the mechanical response of BMGs was developed and implemented. The implementation primarily focused on deformation in the elastic regime but included preliminary results related to the onset of inelastic deformation. The methodology developed included calibration techniques, formulations to extract the machine compliances, verifications using standards and verification for uniqueness of instrument deformation under a spherical indenter. The methodology was different for the two platforms used based on the load-depth response characteristics of the instrument. In the case of the Micro Test platform, the load-depth response of the instrument was linear. In the case of the Nano Test platform, the instrument load-depth response followed a 3/2 power law, representative of Hertzian behavior. The load-depth response of the instrument was determined by subtracting the theoretical response from the corresponding raw load-depth response obtained by elastically indenting a standard steel specimen of known modulus. The true response of the sample was then obtained by subtracting the instrument's response from the corresponding uncorrected load-depth response (raw data). An analytical model to describe the load-train compliance was developed. The methodology was verified using quartz and tungsten standards. Indentation experiments were conducted on Zr41.25Ti13.75Cu12.5Ni10Be22.5 (Vitreloy 1), Cu60Hf25Ti15, Cu60Zr30Ti10 and Fe60Co7Zr10Mo5W2B16 bulk metallic glasses using spherical indenters with diameters 2.8 mm and 100 [micro]m. The spherical geometry results in a simpler stress distribution under the indenter (when compared to a sharp geometry) and furthermore by recourse to spherical indenters the onset of plastic deformation was delayed. In the case of the Zr-based BMG, the experiments showed that the elastic response did not depend on the diameter of the indenter used indicative of the absence of residual stresses in the sample. Large scale plastic deformation was observed when the sample was indented using a smaller diameter indenter. Log scale analysis (i.e., examining the results on a log load vs. log depth response to check for deviation from Hertzian behavior) showed a deviation from a 3/2 fit indicating a deviation from elastic behavior. The onset implied a yield strength value of ~ 4 GPa, higher than the value reported in the literature (~ 2 GPa). Hence, it is believed that the first signs of plastic deformation occurred at lower loads than the predicted loads from the log scale analysis procedure and is expected to occur as discrete bursts. Discrete plastic events or "pop-ins" were observed in the load-depth indentation responses under quasistatic loading conditions, which were believed to be associated with shear band activity. An attempt was made to formulate a mathematical model based on three yield criteria (Drucker-Prager, Mohr-Coulomb and von Mises). Based on the von Mises predictions and comparable experiments on a quartz standard, it was established that the pop-ins observed were real and not an instrument artifact. Multiple load cycles following partial unload experiments showed that the pop-ins affected the subsequent indentation response. The moduli and the yield strength values obtained for the Cu-based BMGs were comparable to the values reported in the literature. There was significant scatter in the indentation data from the Fe-based BMG. Porosity and lack of 100 % compaction were believed to be the reasons for scatter in the data. The financial support of NSF through grant DMR 0314212 is gratefully acknowledged.

The excellent in-plane strength and stiffness to-weight ratios, as well as the ease of manufacturing have made the carbon fiber reinforced polymer composites (CFRPs) suitable structural materials for variety of applications such as aerospace, automotive, civil, sporting goods, etc. Despite the outstanding performance of the CFRPs along their fibers direction (on-axis), they lack sufficient strength and performance in the out-of-plane and off-axis directions. Various chemical and mechanical methods were reported to enhance the CFRPs' out-of-plane performance. However, there are two major drawbacks for utilizing these approaches: first, most of these methods induce damage to the carbon fibers and, therefore, deteriorate the in-plane mechanical properties of the entire CFRP, and second, the methods with minimal deteriorating effects on the in-plane mechanical performance have their own limitations resulting in very confined mechanical performance improvements. These methods include integrating nano-sized reinforcements into the CFRPs' structure to form a hybrid or hierarchical CFRPs. In lieu to all the aforementioned approaches, a relatively novel method, referred to as graphitic structures by design (GSD), has been proposed. The GSD is capable of grafting carbon nanotubes (CNTs) onto the carbon fibers surfaces, providing high concentration of CNTs where they are most needed, i.e. the immediate fiber/matrix interface, and in-between the different laminae of a CFRP. This method shows promising improvements in the in-plane and out-of-plane performance of CFRPs. Zinc oxide (ZnO) nanorods are other nano-sized reinforcing structures which can hybridize the CFRPs via their radially growth on the surface of carbon fibers. Among all the reported methods for synthesizing ZnO nanorods, hydrothermal technique is the most straightforward and least destructive route to grow ZnO nanorods over carbon fibers. In this dissertation, the GSD-CNTs growth method and the hydrothermal growth of ZnO nanorods have been utilized to fabricate hybrid CFRPs. The effect of different ZnO nanorods growth morphologies, e.g. size distribution and alignment, on the in-plane tensile performance and vibration attenuation capabilities of the hybrid CFRPs are investigated via quasi-static tension and dynamical mechanical analysis (DMA) tests, respectively. As a result, the in-plane tensile strength of the hybrid CFRPs were improved by 18% for the composite based on randomly oriented ZnO nanorods over the carbon fibers. The loss tangent of the CFRPs, which indicates the damping capability, increased by 28% and 19% via radially and randomly grown ZnO nanorods, respectively. While there are several studies detailing the effects of dispersed nanofillers on the fracture toughness of FRPs, currently, there are no literature detailing the effect of surface GSD grown CNTs and ZnO nanowire -on carbon fiber- on the fracture toughness of these hybrid composites. This dissertation probes the effects of surface grown nano-sized reinforcements on the fracture toughness via double cantilever beam (DCB) tests on hybrid ZnO nanorod or CNT grafted CFRPs. Results show that the surface grown CNTs enhanced the Mode I interlaminar fracture toughness (GIc) of the CFRPs by 22% and 32%, via uniform and patterned growth morphologies, respectively, over the reference composite based on untreated carbon fiber fabrics. The dissertation also explains the basis of the improvements of the fracture toughness via finite element method (FEM). In particular, FEM was employed to simulate the interlaminar crack growth behavior of the hybrid CFRPs under Mode I crack opening loading conditions embodied by the DCB tests. These simulations revealed that the hybrid CFRP based on fibers with uniform surface grown MWCNTs exhibited 55% higher interlaminar strength compared to the reference CFRPs. Moreover, via patterned growth of MWCNTs, the ultimate crack opening resistance of the CFRPs improved by 20%. To mimic the experimental behavior of the various CFRPs, a new methodology has been utilized to accurately simulate the unstable crack growth nature of CFRPs. Several investigations reported the effects of adding nanomaterials-including CNTs- as a filler phase inside the matrix material, on the impact energy absorption of the hybrid FRPs. However, the impact mitigation performance of CFRPs based on ZnO nanorod grafted carbon fibers has not been reported. The dynamic out-of-plane energy dissipation capabilities of different hybrid composites were investigated utilizing high velocity (~90 m/s) impact tests. Comparing the results of the hybrid MWCNT/ZnO nanorod/CFRP with those of reference CFRP, 21% and 4% improvements were observed in impact energy absorption and tensile strain to failure of the CFRPs, respectively. In addition to elevated stiffness and strength, CFRPs should possess enough tolerance not only to monotonic loadings, but also to cyclic loadings to be qualified as alternatives to traditional structural metal alloys. Therefore, the fatigue life of CFRPs is of much interest. Despite the promising potential of incorporating nano-sized reinforcements into the CFRPs structure, not many studies reported on the fatigue behavior of hybrid CFRPs so far. In particular, there are no reported investigations to the effect of surface grown CNTs on the fatigue behavior of the hybrid CFRPs, due to fact that almost all the CNT growth techniques (except for the GSD method) deteriorated the in-plane performance of the hybrid CFRPs. The hybrid ZnO nanorod grafted CFRPs have not been investigated under fatigue loading as well. In this dissertation, different hybrid CFRPs were tested under tension-tension fatigue to reveal the effects of the different nano-reinforcements growth on the fatigue behavior of the CFRPs. A remarkable fatigue damage tolerance was observed for the CFRPs based on uniform and patterned grown CNT fibers. Almost two decades of fatigue life extension was achieved for CFRPs based on surface grown MWCNTs. / Ph. D. / Carbon fiber reinforced polymer composites (CFRPs) are light-weight materials with excellent strength and stiffness along the direction of the fibers. These great mechanical properties have made CFRPs suitable structural materials for variety of applications such as aerospace, automotive, civil, sporting goods, etc. Despite the outstanding performance of the CFRPs along their fibers direction (on-axis), they lack sufficient strength and performance in the out-of-plane and off-axis directions. Various chemical and mechanical methods were reported to enhance the CFRPs’ out-of-plane performance. However, there are two major drawbacks for utilizing these approaches: first, most of these methods induce damage to the carbon fibers and, therefore, deteriorate the in-plane mechanical properties of the entire CFRP, and second, the methods with minimal deteriorating effects on the in-plane mechanical performance have their own limitations resulting in very confined mechanical performance improvements. These methods include integrating nano-sized reinforcements into the CFRPs’ structure to form a hybrid or hierarchical CFRPs. In lieu to all the aforementioned approaches, a relatively novel method, referred to as graphitic structures by design (GSD), has been proposed. The GSD is capable of grafting carbon nanotubes (CNTs) onto the carbon fibers surfaces, providing high concentration of CNTs where they are most needed, i.e. the immediate fiber/matrix interface, and in-between the different layers of a CFRP. This method shows promising improvements in the in-plane and out-of-plane performance of CFRPs. Zinc oxide (ZnO) nanorods are other nano-sized reinforcing structures which can hybridize the CFRPs via their radially growth on the surface of carbon fibers. Among all the reported methods for synthesizing ZnO nanorods, hydrothermal technique is the most straightforward and least destructive route to grow ZnO nanorods over carbon fibers. In this dissertation, the GSD-CNTs growth method and the hydrothermal growth of ZnO nanorods have been utilized to fabricate hybrid CFRPs. The effect of different ZnO nanorods growth morphologies, e.g. size distribution and alignment, on the in-plane tensile performance and vibration damping capabilities of the hybrid CFRPs are investigated via tension and dynamical mechanical analysis (DMA) tests, respectively. As a result, the in-plane tensile strength of the hybrid CFRPs were improved by 18% for the composite based on randomly oriented ZnO nanorods over the carbon fibers. The loss tangent of the CFRPs, which indicates the damping capability, increased by 28% and 19% via radially and randomly grown ZnO nanorods, respectively. Fracture toughness is a measure for the capability of a material to withstand a load in the presence of damage (i.e. crack) in the material’s structure. While there are several studies detailing the effects of dispersed nanofillers on the fracture toughness of FRPs, currently, there are no literature detailing the effect of surface GSD grown CNTs and ZnO nanowire -on carbon fiber- on the fracture toughness of these hybrid composites. This dissertation probes the effects of surface grown nano-sized reinforcements on the fracture toughness via double cantilever beam (DCB) tests on hybrid ZnO nanorod or CNT grafted CFRPs. Results show that the surface grown CNTs enhanced the Mode I interlaminar fracture toughness (G_Ic) of the CFRPs by 22% and 32%, via uniform and patterned growth morphologies, respectively, over the reference composite based on untreated carbon fiber fabrics. The dissertation also explains the basis of the improvements of the fracture toughness via finite element method (FEM). In particular, FEM was employed to simulate the interlaminar crack growth behavior of the hybrid CFRPs under Mode I crack opening loading conditions embodied by the DCB tests. These simulations revealed that the hybrid CFRP based on fibers with uniform surface grown MWCNTs exhibited 55% higher interlaminar strength compared to the reference CFRPs. Moreover, via patterned growth of MWCNTs, the ultimate crack opening resistance of the CFRPs improved by 20%. To mimic the experimental behavior of the various CFRPs, a new methodology has been utilized to accurately simulate the unstable crack growth nature of CFRPs. Several investigations reported the effects of adding nanomaterials - including CNTs - as a filler phase inside the matrix material, on the impact energy absorption of the hybrid FRPs. However, the impact mitigation performance of CFRPs based on ZnO nanorod grafted carbon fibers has not been reported. The dynamic out-of-plane energy dissipation capabilities of different hybrid composites were investigated utilizing high velocity (~90 m/s) impact tests. Comparing the results of the hybrid MWCNT/ZnO nanorod/CFRP with those of reference CFRP, 21% and 4% improvements were observed in impact energy absorption and tensile strain to failure of the CFRPs, respectively. In addition to elevated stiffness and strength, CFRPs should possess enough tolerance not only to monotonic loadings, but also to cyclic loadings to be qualified as alternatives to traditional structural metal alloys. Therefore, the fatigue life (i.e. the number of loading cycles to failure) of CFRPs is of much interest. Despite the promising potential of incorporating nano-sized reinforcements into the CFRPs structure, not many studies reported on the fatigue behavior of hybrid CFRPs so far. In particular, there are no reported investigations to the effect of surface grown CNTs on the fatigue behavior of the hybrid CFRPs, due to fact that almost all the CNT growth techniques (except for the GSD method) deteriorated the in-plane performance of the hybrid CFRPs. The hybrid ZnO nanorod grafted CFRPs have not been investigated under fatigue loading as well. In this dissertation, different hybrid CFRPs were tested under tension-tension fatigue to reveal the effects of the different nano-reinforcements growth on the fatigue behavior of the CFRPs. A remarkable fatigue damage tolerance was observed for the CFRPs based on uniform and patterned grown CNT fibers. Almost two decades of fatigue life extension was achieved for CFRPs based on surface grown MWCNTs.

The objective of this research is to develop a water-based processing method for incorporating large filler loadings into nanocomposite systems. Specifically, cellulose nanocrystal/poly(vinyl alcohol) (CNC/PVA) nanocomposite aqueous suspensions and films were processed and characterized at CNC loadings up to 67 wt.% with respect to polymer concentration. Both aqueous suspended and freeze-dried CNCs were studied with this method. Two methods for incorporating the CNCs were investigated: solution processing and batch mixing of aqueous suspensions. The materials produced by these methods were characterized using rheology of aqueous suspensions and a method for understanding the morphology of these aqueous suspension through rheological characterization was developed. The CNC/PVA suspensions were dried and the structure of the film studied using x-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. With regard to characterization of polymer structure by these methods, PVA crystallinity was seen to increase with increasing CNC loading. Finally, dynamic mechanical analysis and micro-tensile testing were conducted on consolidated films and CNCs were seen to increase modulus, yield stress but decrease strain at failure. Biodegradation studies were also conducted and CNCs were seen to increase the biodegradation characteristics of PVA. While the general trends in experimental data were the same, differences in properties between systems made with solution processing and batch mixing were observed, attributed to differences in the CNC dispersion. Overall, results indicated that this methodology is feasible for the industrially scalable production of highly loaded nanocomposites.

Biomaterials requirements nowadays are becoming more and more specialized to meet increasingly demanding needs for biomedical applications such as matrices for tissue scaffolds. Among various useful classes of biomaterials, protein-based materials have been extensively pursued as they can offer a wide range of material properties to accommodate a broader spectrum of functional and performance requirements. The advent of genetic engineering and recombinant DNA technology has enabled the production of new protein-based biopolymers with precisely controlled amino acid sequence. As an example, silk-elastinlike protein (SELP) polymers consisting of polypeptide sequences from native silk of remarkable mechanical strength and polypeptide sequences from native elastin that is extremely durable and resilient have been produced. In this dissertation, a particular silk-elastinlike protein copolymer, SELP-47K, was cast into film form, and fully characterized for its material properties, including the mechanical property, secondary structure transition, optical transparency, surface, and other physical, chemical properties. The relationship between mechanical property and protein secondary structure was investigated as well. In addition, the material property tunability which can be induced by physical, mechanical, and chemical treatments has been explored. It is worth noting that the physically crosslinked SELP-47K films displayed mechanical properties comparable to those of native elastin obtained from bovine ligament. Secondary structure study through Raman and FTIR spectra showed that methanol treatment is capable of inducing theβ-sheet crystallization of silklike blocks, which act as physical crosslinks in the protein polymer chain network, thus stabilizing the protein structure and conferring the improved material integrity. The SELP-47K protein polymer thin films displayed excellent optical transparency. In particular, its excellent optical transmittance (over 90%) in visible light range may indicate SELPs can be a family of promising biomaterial candidate for ocular applications. Besides material property characterization, SELP-47K protein polymer has been fabricated into a variety of drug delivery devices to sustainably release a common ocular antibiotic, ciprofloxacin over a period of up to 220 h, with near-first order kinetics.

O presente trabalho visou desenvolver ligas à base de Níquel-Cromo para prótese dentária, que confiram as melhores características metalúrgicas e químicas para posterior produção e aplicação. Para isto foram adquiridas amostras de ligas comerciais de 8 fabricantes. Os materiais foram caracterizados em termos de composição química, propriedades mecânicas, caracterização microestrutural, temperatura de fusão, coeficiente de expansão térmica, corrosão e biocompatibilidade. Para isto, utilizou-se as fluorescência de raios X (XRF-WDS), ICP-OES, ensaios de tração, ensaios de dureza, ensaios de corrosão, avaliação de citotoxicidade, microscopia eletrônica de varredura (MEV), microanálise eletrônica (EDS), difratometria de Raios X (DRX), análise térmica diferencial (DTA), dilatometria e avaliação de fluidez. A maioria dos resultados composicionais não condiz com as composições fornecidas pelos fabricantes. Os resultados mostraram claramente a presença de um eutético típico formado pelas fases Niss e NiBe nas ligas contendo Be, que pode ser considerado uma \"impressão digital\" da presença deste elemento nestas ligas. É possível verificar a formação de intermetálicos na região interdendritica para as ligas isentas de Be, sendo identificado um siliceto (Nb6Ni16Si7) em uma das ligas, que possui temperatura de inicio de fusão inferior ao eutético Niss e NiBe das ligas com Be. De uma forma geral, os resultados dos ensaios de dureza mostraram valores superiores de dureza para as ligas com Be. Foi escolhida uma das ligas comerciais para a reprodução em escala laboratorial (LAB) e industrial (IND). Estas ligas produzidas apresentaram as mesmas características microestruturais, químicas e físicas da liga comercial. Nos ensaios de fluidez, a liga LAB apresentou o mesmo comportamento da liga comercial. A liga IND apresentou limite de escoamento e módulo de elasticidade de ?e0,02%= 810MPa e E= 200 GPa, respectivamente. Os ensaios de corrosão mostraram comportamento passivo tanto para a liga comercial quanto para a liga IND em saliva artificial e enxaguante bucal. O ensaio de citotoxicidade da liga IND indicou comportamento não citotóxico em controle negativo (Chapa de Ti). Os resultados obtidos com a liga IND indicam a possibilidade de fabricação desta liga Ni-Cr para próteses dentárias em escala industrial. / This study aimed to develop nickel-chromium base alloys for dental prostheses with the best characteristics for subsequent production and application. Samples were acquired from eight manufacturers of commercial alloys. The materials were characterized in terms of chemical composition, mechanical properties, microstructure, melting temperature, coefficient of thermal expansion, corrosion and biocompatibility. For this, we have used X-ray fluorescence (XRF-WDS), ICP-OES, tensile tests, hardness testing, corrosion testing, evaluation of cytotoxicity, scanning electron microscopy (SEM), electron probe microanalysis (EDS) , X-ray diffraction (XRD), differential thermal analysis (DTA), dilatometry and evaluation of fluidity. Most of the chemical compositional determined in this study were not consistent with the compositions provided by the manufacturers. The results clearly showed the presence of a typical eutectic microstructure formed by Niss and NiBe in alloys containing Be, which can be considered a \"fingerprint\" of the presence of this element in these alloys. It was possible to verify the formation of intermetallics in the interdendritic region of the Be-free alloys. In one of the alloys this intermetallic was identified as (Nb6Ni16Si7), this alloy presenting a initial melting temperature below the eutectic melting of the Niss+NiB eutectic. Overall, the results of hardness tests showed superior hardness for alloys with Be. One of the commercial alloys was chosen for reproduction in laboratory (LAB) and industrial (IND) scales. The alloys produced showed the same microstructural characteristics, chemical and physical characteristics of the commercial alloy. In the fluidity tests, the LAB alloy showed the same behavior of the commercial alloy. The IND alloy presented yield strength and modulus of elasticity ?e0, 02% = 810MPa, E = 200 MPa, respectively. The corrosion tests showed passive behavior for both commercial and IND alloy in artificial saliva and mouthwash solutions. The cytotoxicity assay indicated that the IND alloy is not cytotoxic in the negative control (Ti plate). The results obtained with the IND alloy indicate the possibility of fabrication this alloy for dental prosthesis on an industrial scale.

O presente trabalho visou desenvolver ligas à base de Níquel-Cromo para prótese dentária, que confiram as melhores características metalúrgicas e químicas para posterior produção e aplicação. Para isto foram adquiridas amostras de ligas comerciais de 8 fabricantes. Os materiais foram caracterizados em termos de composição química, propriedades mecânicas, caracterização microestrutural, temperatura de fusão, coeficiente de expansão térmica, corrosão e biocompatibilidade. Para isto, utilizou-se as fluorescência de raios X (XRF-WDS), ICP-OES, ensaios de tração, ensaios de dureza, ensaios de corrosão, avaliação de citotoxicidade, microscopia eletrônica de varredura (MEV), microanálise eletrônica (EDS), difratometria de Raios X (DRX), análise térmica diferencial (DTA), dilatometria e avaliação de fluidez. A maioria dos resultados composicionais não condiz com as composições fornecidas pelos fabricantes. Os resultados mostraram claramente a presença de um eutético típico formado pelas fases Niss e NiBe nas ligas contendo Be, que pode ser considerado uma \"impressão digital\" da presença deste elemento nestas ligas. É possível verificar a formação de intermetálicos na região interdendritica para as ligas isentas de Be, sendo identificado um siliceto (Nb6Ni16Si7) em uma das ligas, que possui temperatura de inicio de fusão inferior ao eutético Niss e NiBe das ligas com Be. De uma forma geral, os resultados dos ensaios de dureza mostraram valores superiores de dureza para as ligas com Be. Foi escolhida uma das ligas comerciais para a reprodução em escala laboratorial (LAB) e industrial (IND). Estas ligas produzidas apresentaram as mesmas características microestruturais, químicas e físicas da liga comercial. Nos ensaios de fluidez, a liga LAB apresentou o mesmo comportamento da liga comercial. A liga IND apresentou limite de escoamento e módulo de elasticidade de ?e0,02%= 810MPa e E= 200 GPa, respectivamente. Os ensaios de corrosão mostraram comportamento passivo tanto para a liga comercial quanto para a liga IND em saliva artificial e enxaguante bucal. O ensaio de citotoxicidade da liga IND indicou comportamento não citotóxico em controle negativo (Chapa de Ti). Os resultados obtidos com a liga IND indicam a possibilidade de fabricação desta liga Ni-Cr para próteses dentárias em escala industrial. / This study aimed to develop nickel-chromium base alloys for dental prostheses with the best characteristics for subsequent production and application. Samples were acquired from eight manufacturers of commercial alloys. The materials were characterized in terms of chemical composition, mechanical properties, microstructure, melting temperature, coefficient of thermal expansion, corrosion and biocompatibility. For this, we have used X-ray fluorescence (XRF-WDS), ICP-OES, tensile tests, hardness testing, corrosion testing, evaluation of cytotoxicity, scanning electron microscopy (SEM), electron probe microanalysis (EDS) , X-ray diffraction (XRD), differential thermal analysis (DTA), dilatometry and evaluation of fluidity. Most of the chemical compositional determined in this study were not consistent with the compositions provided by the manufacturers. The results clearly showed the presence of a typical eutectic microstructure formed by Niss and NiBe in alloys containing Be, which can be considered a \"fingerprint\" of the presence of this element in these alloys. It was possible to verify the formation of intermetallics in the interdendritic region of the Be-free alloys. In one of the alloys this intermetallic was identified as (Nb6Ni16Si7), this alloy presenting a initial melting temperature below the eutectic melting of the Niss+NiB eutectic. Overall, the results of hardness tests showed superior hardness for alloys with Be. One of the commercial alloys was chosen for reproduction in laboratory (LAB) and industrial (IND) scales. The alloys produced showed the same microstructural characteristics, chemical and physical characteristics of the commercial alloy. In the fluidity tests, the LAB alloy showed the same behavior of the commercial alloy. The IND alloy presented yield strength and modulus of elasticity ?e0, 02% = 810MPa, E = 200 MPa, respectively. The corrosion tests showed passive behavior for both commercial and IND alloy in artificial saliva and mouthwash solutions. The cytotoxicity assay indicated that the IND alloy is not cytotoxic in the negative control (Ti plate). The results obtained with the IND alloy indicate the possibility of fabrication this alloy for dental prosthesis on an industrial scale.