Publications: #77

77. "A contact mechanics method for characterizing the elastic properties and permeability of gels" Hui, C.-Y.; Lin, Y.Y.; Chuang, F.-C.; Shull, K.R.; Lin, W.-C., Journal of Polymer Science, Part B: Polymer Physics, 44, 359 (2005).

When a satd. gel immersed in the same liq. is suddenly brought into contact with a smooth rigid indenter, the liq. cannot immediately flow out of the pores, and so the gel initially behaves as an incompressible material. This gives rise to a pressure gradient in the liq. phase and the liq. flows until the pressure in it goes to zero everywhere, and all the stresses are transferred to the elastic network. As a result of the flow, the force needed to maintain a const. contact area relaxes with time. In this work, the authors study the feasibility of using an indentation test to measure this time-dependent force and to det. the elastic modulus, the Poisson's ratio, and the permeability, Dp, of the network. Specifically, the authors consider a two-dimensional Hertz contact problem of a rigid circular cylinder indenting on a half space consisting of an elastic gel. The network of the gel is assumed to be linearly elastic and isotropic, and liq. flow within the gel is assumed to obey Darcy's law, which states that the flux is proportional to the pressure gradient. Exact expressions are obtained for the initial and final force required to maintain a given contact length. These expressions allow us to det. the elastic consts. of the network. The permeability of the network can be obtained from the time-dependent relaxation of the load, which is obtained by solving the exact continuum equations.

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