We develop a method of poroelastic relaxation indentation (PRI) to characterize thin layers of gels.  The solution to the time-dependent boundary-value problem is obtained in a remarkably simple form, so that the force-relaxation curve obtained by indenting a gel readily determines all the poroelastic constants of the gel—the shear modulus, Poisson’s ratio, and the effective diffusivity.  The method is demonstrated with a layer of polydimethylsiloxane immersed in heptane.

The paper is accepted for publication by J. Appl. Phys, and can be downloaded from: http://www.seas.harvard.edu/suo/papers/254.pdf

We use instrumented indentation to characterize the mechanical and transport behavior of a pH-sensitive hydrogel in various aqueous buffer solutions. In the measurement an indenter is pressed to a fixed depth into a hydrogel disk and the load on the indenter is recorded as a function of time. By analyzing the load-relaxation curve using the theory of poroelasticity, the elastic constants of the hydrogel and the diffusivity of water in the gel can be evaluated. We investigate how the pH and ionic strength of the buffer solution, the hydrogel cross-link density, and the density of functional groups on the polymer backbone affect the properties of the hydrogel. This work demonstrates the utility of indentation techniques in the characterization of pH-sensitive hydrogels.

This paper studies the poroelastic behavior of an alginate hydrogel by a combination of theory and experiment. The gel—covalently crosslinked, submerged in water and fully swollen—is suddenly compressed between two parallel plates. The gap between the plates is held constant subsequently, and the force on the plate relaxes while water in the gel migrates. This experiment is analyzed by using the theory of linear poroelasticity. A comparison of the relaxation curve recorded in the experiment and that derived from the theory determines the elastic constants and the permeability of the gel. The material constants so determined agree well with those determined by using a recently developed indentation method.

This paper uses a method based on indentation to characterize a polydimethylsiloxane (PDMS) elastomer submerged in an organic solvent (decane, heptane, pentane, or cyclohexane).  An indenter is pressed into a disk of a swollen elastomer to a fixed depth, and the force on the indenter is recorded as a function of time.  By examining how the relaxation time scales with the radius of contact, one can differentiate the poroelastic behavior from the viscoelastic behavior.  By matching the relaxation curve measured experimentally to that derived from the theory of poroelasticity, one can identify elastic constants and permeability.  The measured elastic constants are interpreted within the Flory-Huggins theory.  The measured permeability indicate that the solvent migrate

When an indenter is pressed into a gel to a fixed depth, the solvent in the gel migrates, and the force on the indenter relaxes. Within the theory of poroelasticity, the force relaxation curves for indenters of several types are obtained in a simple form, enabling indentation to be used with ease as a method for determining the elastic constants and permeability of the gel. The method is demonstrated with a conical indenter on an alginate hydrogel.

Does anyone have experience using poroelasticity model? I dont underestand the abaqus model -the logarithmic bulk modulus and.., where are these coming from?Is anyone knows a reference book to link those?

Research activities on soil models, porous media, poroelasticity.

Just published in this month's Journal of Materials Research--a study on poroelastic nanoindentation characterization for hydrated bone samples.  Poroelastic problems are notoriously difficult to incorporate into routine materials characterization due to the paucity of problems with closed-form solutions.  However, in some cases, a master-curve does exist and parameter identification can be accomplished without requiring inverse finite element analysis and optimization for every condition.  The abstract follows, linked from here .

Poroelastic nanoindentation responses of hydrated bone, J. Mater. Res. 23 (2008) 1307.

The 2007 Maurice A. Biot Medal for Poromechanics has been awarded during the ASCE Engineering Mechanics Conference held at Virginia Tech last Tuesday.

The 2007 Biot Medal winner is Dr. James R. Rice of Harvard University.

If you are interested in further information, such as citation of Dr. Rice's work, and photos, you can check this page:

http://www.olemiss.edu/sciencenet/poronet/medal.html

The 7th North American Workshop on Applications of the Physics of Porous Media will be held in Puerto Vallarta, Mexico, November 2-6, 2007. This will be the 7th biennial meeting of researchers around the world who are interested in the phenomena associated with physics of fluid flow and deformation in porous media and its applications to a broad range of basic roblems encountered in geophysics, geomechanics, medical physics, and condensed matter physics.

Full details are available at the website:

Given the growing interest in poroelasticity within this forum, I thought I would post the link to "Poronet" -- the poromechanics internet resources network.  In particular, there is a nice long pdf chapter on the fundamentals of poroelasticity from Detournay and Cheng, 1993, which has become one of the standard references in the field. 

M.A. Biot, General theory of three-dimensional consolidation, Journal of Applied Physics 12, 155-164 (1941).

This paper founded the theory of poroelasticity. Perhaps the most vivid demonstration of poroelasticity is a sponge, an elastic solid with connected pores. When immersed in water, the sponge absorbs water. When a saturated sponge is squeezed, water will come out. More generally, the subject is known as diffusion in elastic solids, or elasticity of fluid-infiltrated porous solids, or poroelasticity. The theory has been applied to diverse phenomena, including