I n Situ X-Ray Tomography Measurements of Deformation in Cellular Solids
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In Situ X-Ray
Tomography Measurements of Deformation in Cellular Solids
E. Maire, A. Elmoutaouakkil, A. Fazekas, and L. Salvo Abstract The use of microtomography to study the structure and especially the deformation modes of cellular solids is reviewed in this article. First, the technique is described in detail. Examples illustrating the power of the coupling of in situ deformation with three-dimensional (3D) imaging, drawn from the recent literature and the authors’ own work, are then given. The most detailed example is the study of the deformation modes of several samples made of different aluminum foams. Four kinds of closed-cell foams were investigated, corresponding to different routes available today for their manufacture. The initial macrostructure was quantified using the 3D images combined with 3D granulometry, allowing retrieval of pertinent information about the cell size and the wall and strut thicknesses. The global behavior exhibited by the foams during the in situ compression experiments was shown to vary from one brand of material to another. Some of these variations can be explained by differences in the known microstructure and the measured macrostructure of the samples. Keywords: cellular solids, metals, x-ray tomography.
Introduction Cellular materials surround us in nature (e.g., wood, sponge, bone, coral, cork). They have a unique combination of properties that allow them to be used in many special applications. The deformation of these materials is not well understood, however, and remains to be fully assessed both experimentally and theoretically. Deformation behavior is controlled by the structure of the cellular material at two scales: (1) the microstructural (i.e., the microstructure of the constitutive material, which governs the stiffness and strength of the cellular walls); and (2) the macrostructural (i.e., the complex arrangement of the cells and of their edges and faces). Here, we focus on this second scale, which we refer to as the macrostructure of the cellular solid.
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X-ray tomography has been shown to be a very powerful technique for the study of this macrostructure.1–5 The technique is nondestructive and gives information in three dimensions at scales down to 1 m. It has successfully been used for studying in situ the deformation of dense materials6 and cellular materials of metals,7 polymers,8 and even bone.9,10 In this article, we describe the use of x-ray tomography to investigate the deformation modes during mechanical loading (especially compression) of different types of cellular materials. The use of the tomography technique in the field of materials science is quite new, and therefore the amount of published work is small. Historically, the first field of application
(without in situ loading) was in medicine. The technique was subsequently applied to dense materials,11 and was soon coupled with the use of in situ loading, initially in tension.12 Most recently, the coupled technique has been applied in the field of cellular materials.7,8,13 After reviewing the
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