Experimental in-plane characterization of a cellular material composed by a cell with a normal re-entrant link and geometrical parameters effects on the structure mechanical properties
Résumé
In this work, we have characterized a cellular structure constituted by a new cell on which we carried out, initially, tensile and shear tests in order to get its in-plane mechanical properties; in the second time, we explored the effects that geometry will have on these mechanical properties by varying the geometric parameters of the cell. The specimens were designed by Computer Aided Design software and obtained by rapid prototyping (laser cutting). In the quest for results, we used the technique of marker tracking. This optical method of correlating images consists in measuring the plane components of the displacement of a plane surface leaving some marks on the specimen. This makes it possible to determine the in-plane components of the transformation gradient tensor and to reach the plane components of the deformation tensor under certain assumptions (axisymmetric or isochoric transformation, small deformations, etc). The material of the studied structure is a polymethylmethacrylate, often abbreviated to PMMA. The first results gave a negative Poisson's ratio, announcing an auxetic behavior. The following results have confirmed the auxetic character of the cell and show great influence of the geometric parameters on the mechanical properties of the new structure.