The consistent and correct model of media taking into account scale effects (cohesion and adhesive interactions) is constructed as a special case of the Cosserat's pseudocontinuum model. The variant of the interphase layer theory is elaborated, which includes the following moments: formal mathematical statement, physical constitutive equations, numerical estimations of an interphase layer influence on the stress state and energy density distribution in a composite.
The mathematical statement of interphase layer theoryRecently, in the papers [1]- [2], the generalized continuum model with kept dislocations was developed. Generally, the model presented allows to describe local-cohesion interactions [2] and superficial effects [1]. The interphase layer theory allows to study the specific local interactions which determining features of the properties of contacting phases and material as whole: cohesion fields and the internal interactions associated to them; interfacial adhesive interactions. The marked types of interactions are characterized by essential localness, small area of interaction, concentrate about defects, borders, interfaces.This mathematical statement is completely determined by following equation for the Lagrange functional L and the following variational equation:on any plane with a normal n i on the boundary surface the vector of forces T i is determinedand moment vectorHere ∇ 2 is the Laplace operator, R i are components of the displacement vector, l 2 0 = µ/C, γ ij and θ are the components of the deviator of strain and spherical deformation tensor, ω k are the components of the rotation vector, E ijk is the Levi-Civita tensor, δ ij is the Kronecker delta, µ, λ are the Lame coefficient, C is the physical constant that determine the cohesion interactions, D ijṘiṘj = A n i n jṘiṘj + B (δ ij − n i n j )Ṙ iṘj is energy density associated with changing of defectiveness of a contact surface due to modified a surface, P V i is the vector of density of the external loads over the body volume, P F i is the vector of density of the surface loads, F is the boundary surface and L ij (...) is the operator of the classical theory of elasticity.New physical constants A and B determine the surface effects associated with the normal to the surface of the body, and the superficial effects in the tangent plane respectively. Note that the ideal adhesive interaction influences only for a local state and does not change classical boundary conditions. Using variational formulation of the problem we can formulate it's differential representation as Euler equations of the functional:where S is surface of inclusion in composite. To understand the physical sense let's define displacement of cohesion field u i and separate general displacements R i on two components satisfied classical and non-classical equation of theory of elasticity: