Elastic behavior porous materials

The macroscopic behavior of a saturated porous material undergoing a dissolution of its linear elastic solid matrix is therefore described by the classical Biot s theory, where the poroelastic properties now depend on the morphological parameter . Formally, plays the role of a damage parameter accounting for the dissolution. 

Abstract In this contribution, the coupled flow of liquids and gases in capillary thermoelastic porous materials is investigated by using a continuum mechanical model based on the Theory of Porous Media. The movement of the phases is influenced by the capillarity forces, the relative permeability, the temperature and the given boundary conditions. In the examined porous body, the capillary effect is caused by the intermolecular forces of cohesion and adhesion of the constituents involved. The treatment of the capillary problem, based on thermomechanical investigations, yields the result that the capillarity force is a volume interaction force. Moreover, the friction interaction forces caused by the motion of the constituents are included in the mechanical model. The relative permeability depends on the saturation of the porous body which is considered in the mechanical model. In order to describe the thermo-elastic behaviour, the balance equation of energy for the mixture must be taken into account. The aim of this investigation is to provide with a numerical simulation of the behavior of liquid and gas phases in a thermo-elastic porous body. 

Besides the brittle elastic behavior, when a gel is subjected to a tensile load, under a compressive load the porous network can be irreversibly transformed. This plasticity effect depends strongly on the volume fraction of pores, but is also clearly affected by macropores and by the OH content. In fact, either under tension or compression, the gel material is not stable and its structure and mechanical features evolve. 

Consider the cube of porous material shown in Fig. 11, which has a relative density of p and a volume fraction of porosity of I - /). The area of each face is A = As + Ai where /4s = pA is the fraction of that area occupied by the solid phase and A = (I - p)A is the fraction occupied by liquid. We are interested in the constitutive equation for this material, which is to say, the relationship between the stresses applied and the strains that result. For the moment we assume that the liquid has been drained away, and consider the behavior of the solid phase alone. If the solid phase is elastic,... 

The difference in the elastic properties between the layers caused the zigzag R-curve behavior. The porosity in the porous layer directly affected the fracture behavior. Figure 9.1.15 shows the load-displacement curves in the SENS test for the materials with porosity in the porous layer of 30 and 16%. The high porosity clearly contributed to the higher fracture resistance due to the enhanced delamination in the porous layer (Fig. 9.1.16). 

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