Mechanical properties representative volume unit

For a Hookian material, the concept of minimum strain energy states that a material fails, for example cell wall disruption occurs, when the total strain energy per unit volume attains a critical value. Such an approach has been used in the past to describe a number of experimental observations on the breakage of filamentous micro-organisms [78,79]. Unfortunately, little direct experimental data are available on the Young s modulus of elasticity, E, or shear modulus of elasticity G representing the wall properties of biomaterial. Few (natural) materials behave in an ideal Hookian manner and in the absence of any other information, it is not unreasonable to assume that the mechanical properties of the external walls of biomaterials will be anisotropic and anelastic. 

In modelling the physical and the mechanical properties of textiles, there are usually two choices, i.e. whether to consider a discrete or a continuum model. A continuum model assumes that the property of any small part of the material can be considered equal to that of the whole volume. In order to model a textile structure as a continuum, its volume is divided into small parts termed unit cells or representative volume elements (RVE). RVEs model the material structure at a miaoscopic level, i.e. at the level of individual fibre arrangements. The mechanical properties of RVEs are modelled and then used at a macroscopic level, which is the level of yarn or fabric, under the assumption that the whole volume of the material can be re-constructed from a number of RVEs. 

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