X-Ray computed tomography O.Caty1, F.Gaubert1, G.Hauss2, G.Chollon1 caty@lct.u-bordeaux1.fr 1LCTS : Laboratory of Thermostructural Composites - 3 Allée de la Boetie, 2 ICMCB - 87, Avenue du Docteur Schweitzer F33 600 PESSAC, France Abstract Carbon foams are refractory cellular materials. The material exhibits an open porosity with a tridimensional architecture offering multifunctional properties. These properties can ever be tailored threw post processing in order to use the material in many fields such as energy (fuel cell) or transport (shock absorber). For all applications, the knowledge of the mechanical properties is important. These properties depend on the 3D architecture and the damage kinetics. In this study the computed X-Ray microtomography (µCT) has been used firstly to analyze the damage kinetics during in-situ compression tests and secondly to simulate the behavior. The µCT compression tests lead to the local damages and global deformations. The analyses of these images will be presented to illustrate the potentiality of tomographic investigations for brittle cellular materials. To assess both the stress and strain fields, a model based on the real material was developed. This model consists in meshing the tridimensional images and modeling the behavior of the constitutive material. The fracture of cells is treated using an adapted law and a brittle criterion. The models are also compared with the measured macroscopic mechanical behavior or adapted to simulate numerically-generated materials. Introduction Ceramic foams are cellular materials which are used in industry in particular for their attractive mechanical properties coupled with other functionalities. Thermal insulation, acoustical absorption properties, low density with large specific surface and electrical conductivity are some examples of these properties [1-2-3]. The main industrial sectors are packaging (as shock absorbers), filtering (through the open cell) or energy (fuel cells). Although the main reason to select this material is not always its mechanical properties, they need to be known and must be understood in regards with the parameters of the 3D structure. The ceramic foams studied were manufactured at the LCTS using vitreous carbon preform provided by the CEA - Le Ripault [1-2]. This material is composed of a solid 3D arrangement of struts and edges delimitating open cells. The solid phase is glassy carbon and the resulting material combines its properties (thermal stability, high strength…) with the properties of the cellular structure (low density, high specific surface, open porosity). The material is macroscopically ductile while the vitreous carbon itself is brittle. This surprising behavior is explained by the 3D structure and its damage kinetics. Macroscopic compression tests were carried on foams having different pore sizes and relative densities by S.Delettrez [1-2]. The results of these tests are not in accordance with the theory of Gibson and Ashby [1–3]. One hypothesis to explain this difference is that the 3D structure of the material is far from the one considered by Gibson and Ashby [3]. In particular one can not define a simple unite cell, the material being rather random. This random 3D structure must be characterized to better understand the mechanical properties. Probably the better way to do is using micro-computed X-Ray tomography (µCT). Firstly the mechanical properties and damage kinetics are analyzed using a compression test coupled with tomography. These observations are necessary to understand the damaged mechanisms responsible of the macroscopic behavior. In addition it would be useful to measure further informations, such as the strain and stress fields in the material. The choice of T. Proulx (ed.), Optical Measurements, Modeling, and Metrology, Volume 5, Conference Proceedings of the Society for Experimental Mechanics Series 9999999, DOI 10.1007/978-1-4614-0228-2_6, © The Society for Experimental Mechanics, Inc. 2011 39 Characterisation of mechanical properties of cellular ceramic materials using
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