Examinando por Materia "Collagen"
Mostrando 1 - 6 de 6
Resultados por página
Opciones de ordenación
Ítem Deformation behaviour of aged coronal dentin(Blackwell Munksgaard, 2018-06-01) Montoya; C.; Arola; D.; Ossa; E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaObjective: This study aimed to identify the changes in the time-dependent deformation response of coronal dentin with ageing and its relationship with changes in chemical composition. Background: The structural behaviour of dentin with ageing is affected by changes in the density and diameter of its dentinal tubules (ie porosity), as well as changes in chemical composition throughout the tooth. However, little is known about the time-dependent deformation behaviour of aged dentin and the importance of its hierarchical structure and variations in chemical composition. Materials and methods: The spherical indentation response of aged coronal dentin was analysed in the outer, middle and inner regions, and its time-dependent deformation response was modelled in terms of its microstructure and chemical composition using a model recently proposed for young dentin. Results: The viscous deformation behaviour of aged dentin followed a power-law response with a decrease in the stress exponent when compared to young dentin. These results can be explained by cross-linking of the collagen present in the tissue. Conclusion: A decrease in the deformation ability of aged dentin was found. This behaviour could be a result of a dissolution process and reprecipitation of the minerals present in intertubular dentin into the dentinal tubules. © 2018 John Wiley & Sons A/S and The Gerodontology Association. Published by John Wiley & Sons LtdÍtem Effect of chemical composition and microstructure on the mechanical behavior of fish scales from Megalops Atlanticus(ELSEVIER SCIENCE BV, 2016-03-01) Gil-Duran, S.; Arola, D.; Ossa, E.A.; Gil-Duran, S.; Arola, D.; Ossa, E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaThis paper presents an experimental study of the composition, microstructure and mechanical behavior of scales from the Megalops Atlanticus (Atlantic tarpon). The microstructure and composition were evaluated by Scanning Electron Microscopy (SEM) and RAMAN spectroscopy, respectively. The mechanical properties were evaluated in uniaxial tension as a function of position along the length of the fish (head, mid-length and tail). Results showed that the scales are composed of collagen and hydroxyapatite, and these constituents are distributed within three well-defined layers from the bottom to the top of the scale. The proportion of these layers with respect to the total scale thickness varies radially. The collagen fibers are arranged in plies with different orientations and with preferred orientation in the longitudinal direction of the fish. Results from the tensile tests showed that scales from Megalops Atlanticus exhibit variations in the elastic modulus as a function of body position. Additional testing performed with and without the highly mineralized top layers of the scale revealed that the mechanical behavior is anisotropic and that the highest strength was exhibited along the fish length. Furthermore, removing the top mineralized layers resulted in an increase in the tensile strength of the scale. © 2015 Elsevier Ltd.Ítem Effect of chemical composition and microstructure on the mechanical properties of fish scales from Megalops Atlanticus(Universidad EAFIT, 2014) Gil Durán, Santiago; Ossa Henao, Édgar AlexánderFishes use their scales as a protection against external threats like environmental hazards and predators -- This work presents an experimental study of the microstructure, composition and mechanical properties of Megalops Atlanticus (Atlantic tarpon) scales -- Mechanical properties were evaluated in uniaxial tension as a function of position along the length of the fish (head, mid-length and tail) -- Additional tensile tests were performed in three different orientations (0°,45°, and 90°) to evaluate the anisotropic behavior of the scales -- Examination of fish scale microstructure and compositions were performed by using Scanning Electron Microscopy (SEM) and RAMAN spectroscopy -- The results showed that scales from Megalops Atlantiticus are anisotropic, with variations of mechanical properties as a function of body position -- Megalops Atlantiticus scales display a characteristic hierarchical structure composed of fibrous collagen layered structures and hydroxyapatite crystals that provide multifunctional characteristics, showing to have a non-homogenous distribution within the scaleÍtem Interfibril hydrogen bonding improves the strain-rate response of natural armour(Royal Society Publishing, 2019-01-01) Arola D.; Ghods S.; Son C.; Murcia S.; Ossa E.A.; Arola D.; Ghods S.; Son C.; Murcia S.; Ossa E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaFish scales are laminated composites that consist of plies of unidirectional collagen fibrils with twisted-plywood stacking arrangement. Owing to their composition, the toughness of scales is dependent on the intermolecular bonding within and between the collagen fibrils. Adjusting the extent of this bonding with an appropriate stimulus has implications for the design of next-generation bioinspired flexible armours. In this investigation, scales were exposed to environments of water or a polar solvent (i.e. ethanol) to influence the extent of intermolecular bonding, and their mechanical behaviour was evaluated in uniaxial tension and transverse puncture. Results showed that the resistance to failure of the scales increased with loading rate in both tension and puncture and that the polar solvent treatment increased both the strength and toughness through interpeptide bonding; the largest increase occurred in the puncture resistance of scales from the tail region (a factor of nearly 7). The increase in strength and damage tolerance with stronger intermolecular bonding is uncommon for structural materials and is a unique characteristic of the low mineral content. Scales from regions of the body with higher mineral content underwent less strengthening, which is most likely the result of interference posed by the mineral crystals to intermolecular bonding. Overall, the results showed that flexible bioinspired composite materials for puncture resistance should enrol constituents and complementary processing that capitalize on interfibril bonds. © 2019 The Author(s) Published by the Royal Society. All rights reserved.Ítem The natural armors of fish: A comparison of the lamination pattern and structure of scales(ELSEVIER SCIENCE BV, 2017-09-01) Murcia S; Lavoie E; Linley T; Devaraj A; Ossa EA; Arola D; Murcia S; Lavoie E; Linley T; Devaraj A; Ossa EA; Arola D; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaFish scales exhibit a unique balance of flexibility, strength and toughness, which is essential to provide protection without encumbering locomotion. Although the mechanical behavior and structure of this natural armor are of recent interest, a comparison of these qualities from scales of different fish species has not been reported. In this investigation the armor of fish with different locomotion, size and protection needs were analyzed. Scales from the Arapaima gigas, the tarpon (Megalops atlanticus) and the carp (Cyprinus carpio) were compared in terms of the stacking sequence of individual plies and their microstructure. The scales were also compared with respect to anatomical position to distinguish site-specific functional differences. Results show that the lamination sequence of plies for the carp and tarpon exhibit a Bouligand structure with relative rotation of 75 degrees between consecutive plies. The arapaima scales exhibit a cross-ply structure, with 90 degrees rotation between adjacent plies. In addition, results indicate that the volume fraction of reinforcement, the number of plies and the variations in thickness with anatomical position are unique amongst the three fish. These characteristics should be considered in evaluations focused on the mechanical behavior.Ítem Zylerberg, 1985 Contributions of the layer topology and mineral content to the elastic modulus and strength of fish scales(ELSEVIER SCIENCE BV, 2018-02-01) Murcia, S.; Miyamoto, Y.; Varma, M.P.; Ossa, A.; Arola, D.Fish scales are an interesting natural structural material and their functionality requires both flexibility and toughness. Our previous studies identified that there are spatial variations in the elastic properties of fish scales corresponding to the anatomical regions, and that they appear to be attributed to changes in the microstructure. In the present study, a model is proposed that describes the elastic behavior of elasmoid fish scales in terms of the relative contributions of the limiting layer and both the internal and external elasmodine. The mechanical properties of scales from the Megalops atlanticus (i.e. tarpon) were characterized in tension and compared with predictions from the model. The average error between the predicted and the experimental properties was 7%. It was found that the gradient in mineral content and aspect ratio of the apatite crystals in the limiting layer played the most important roles on the elastic modulus of the scales. Furthermore, misalignment of plies in the external elasmodine from the longitudinal direction was shown to reduce the elastic modulus significantly. This is one approach for modulating the fish scale flexibility for a high mineral content that is required to increase the resistance to puncture. © 2017