Characterisation material physical properties of porous materials - Article Example

According to this theory, three different kinds of waves propagate within the porous material. One is the compression wave propagating in the fluid phase, the second is the compression wave travelling in the solid phase, and the third is the shear wave propagating in the solid phase (Pan & Jackson). The Biot model for predicting sound propagation in porous materials is based on five material properties, also called Biot parameters, of the material. These five parameters include the porosity of the material, its airflow resistivity, tortuosity, thermal characteristic length, and viscous characteristic length.

The present review discusses the current methods for measuring and predicting these five Biot parameters. 2 Material Physical Properties in Biot Theory This section details the characterization of the material physical properties, i.e. the five Biot parameters, of porous materials. A review of the properties themselves along with the methods for measuring and predicting them is presented. 2.1 Porosity (?) The porosity of a material is the “relative fraction, by volume, of the air contained within the material” (Fellah et al. 2003, p. 296). . Other non-destructive methods have been applied for the estimation of porosity.

Beranek (cited in Leclaire et al. 2003) gave a very simple method, in which the porous material is saturated with water and placed in an airtight chamber that is linked to a manometer. This method was based on Boyle’s law and was helpful in estimating the open porosity of the material having surfaces with open-pores. Another method that utilised Beranek’s principle was that by Champoux et al. (cited in Leclaire et al. 2003), which had a very elaborate system involving a micrometer and a differential pressure transducer.

Recently, many different methods have been proposed and applied by various investigators to measure the porosity of materials. For instance, the method by Connolly (cited in Yang 2011) uses a thermographic method. In this method, the correlation between porosity and thermal diffusivity is derived by analysing the heat diffused in the sample upon heating with a laser. Other methods include the use of X-ray computed tomography, microwaves etc to measure porosity. ASTM D6226-05 test standard describes another method that uses a gas pycnometer for measuring porosity (Pan & Jackson 2009).

This method uses an apparatus consisting of calibrated expansion and sample chambers. The porous sample is placed in the sample chamber and subjected to a certain predetermined increase in pressure. This method is also based on Boyle’s law and measures the open pore volume of the sample. Another method given by Salissou and Panneton (cited in Pan & Jackson 2009) was based on the experimental determination of the solid phase volume of the material. Four tests for measuring the masses with and without the sample at