Vincent Pensée

The purpose of this work is to extend the equations of linear poroelasticity to the case of materials with nanopores. We consider a model of microstructure which corresponds to an assemblage of hollow spheres saturated by a fluid. The solid phase is linearly elastic and isotropic; pores are assumed to be of nanometric size. To account for the pore surface stresses, the Young-Laplace model is used. The nanopore size effects on the effective bulk modulus, Biot’ modulus and coefficient are shown. When pores are sufficiently large, the classical relations of linear poroelasticity are retrieved.

In this work, we derive a general piezoelectric interface model by using a coordinate-free asymptotic approach. Next, this interface model is applied to the homogenization of fibrous piezoelectric composites. The overall piezoelectric properties are calculated and compared to the ones obtained by using the three-phase model.

A general three-dimensional micromechanical approach to modeling anisotropic damage of brittle materials such as concrete, rocks, or certain ceramics is presented. Damage is analyzed as a direct consequence of microcracks growth. Following a rigorous scale change methodology, the macroscopic free energy of the microcracked medium is built considering either open and closed microcracks. Moreover, the microcracks opening/closure criterion as well as the moduli recovery conditions (unilateral effects) are addressed in stress-based and strain-based formulations. An alternative derivation of the homogenized properties, based on the well-known Eshelby method, is also presented and extended here to closed cracks. From the micromechanical analysis, an energy-based yield condition is formulated and illustrated in various stress subspaces. Assuming that the normality rule applies, we then present the damage evolution law and the rate form of the constitutive model. The main capabilities and advantages of the microm...

On démontre que l'influence de fissures fermées non frottantes sur les caractéristiques élastiques macroscopiques d'un milieu fissuré peut être évaluée par une technique d'estimation basée sur la théorie d'Eshelby. L'idée consiste à remplacer la fissure par un matériau fictif de module de cisaillement nul et de module de compression identique à celui du solide. La fermeture progressive des fissures est responsable de la non linéarité du comportement macroscopique. Ce phénomène permet de déterminer la distribution de la densité de fissures en fonction du rapport d'aspect initial.