“…In order to represent better the types of complex geometries found in cellular material, the authors have investigated the use of fractals [2,18], which arise in many other areas of science [19] and play a part in describing a variety of behaviours in nonlinear systems [20]. Fractals can be constructed in a number of ways, but a particularly attractive procedure is by application of a small number of affine contraction maps [2,20,21]. Although complex geometries can readily be represented using fractals, their subsequent use in practical analysis is beset with difficulties.…”