Constitutive behaviour of composite with anisotropic friction

This paper presents an approach to a constitutive model for anisotropic quasi-brittle materials, developed in the framework of rate independent softening plasticity, involving a yield criterion in which an anisotropic friction and cohesion tensors are involved. It turns out to be useful for materials characterized by ultimate behaviour which varies according to the direction, such as composite materials, anisotropic rocks, textiles, masonry. The intrinsic structure of a wide range of structural, geological and industrial materials, such as composites, masonry, wood, textiles and several types of rocks and clays, is the major cause of their anisotropic behaviour. The material response to the same stress state is strongly linked to the sampling orientation with respect to the principal stress axes. The position and the orientation of the clay particles, for example, define a sort of material geometry on which the stress geometry depends. Similar considerations can be applied to a Representative Volume Element in order to describe the macroscopical behaviour of an equivalent anisotropic orientation of the fibers in a composite, the disposition of the bed and head joints in a masonry wall medium resulting from an homogenization technique. Moreover, anisotropic friction plays an important role in the formation of wrinkles and folds in textiles. The intrinsic structure of a wide range of structural, geological and industrial materials, such as composites, masonry, wood, textiles and several types of rocks and clays, is the major cause of their anisotropic behaviour. The material response to the same stress state is strongly linked to the sampling orientation with respect to the principal stress axes. The position and the orientation of the clay particles, for example, define a sort of material geometry on which the stress geometry depends. Similar considerations can be applied to a Representative Volume Element in order to describe the macroscopical behaviour of an equivalent anisotropic orientation of the fibers in a composite, the disposition of the bed and head joints in a masonry wall medium resulting from an homogenization technique. Moreover, anisotropic friction plays an important role in the formation of wrinkles and folds in textiles. The theory proposed in this paper, provides a failure criterion for quasi brittle materials in which the existence of an anisotropic friction and cohesion tensors are postulated. A geometrical representation of the limit domain in the case of plane stress, together with the results of laboratory tests, is presented and discussed.