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A piecewise-homogeneous material model is used to numerically determine the edge effect length in a composite laminate with reinforcement plies subject to unidirectional longitudinal compression. Consideration is given to mixed boundary conditions (regularity of the material structure and symmetry of the surface load) on the sides of the composite specimen and boundary conditions for stresses on the stress-free sides of the specimen. The dependence of the edge effect length on the ratio of the mechanical characteristics of the composite components is studied Keywords: composite laminate specimen, compression of reinforcement plies, edge effect length, modified variational difference method Introduction. In designing and testing composite materials (CMs), it is of interest to analyze the combined effect of such factors as the structural inhomogeneity of a CM and the loading and boundary conditions of a CM specimen on the edge effects. One of the aspects of this problem is the analysis of the zone of unsteady stress-strain state (edge effect) where a surface load that changes substantially at distances comparable with the typical length scale of the structural inhomogeneity of the CM is applied. This, in particular, represents the case where a surface load is applied only to the reinforcement of a CM specimen. In many studies on the influence of the inhomogeneity of a material on the decay of edge effects, it is pointed out that the edge effect length may be rather great at a certain ratio of the elastic and geometrical characteristics of the composite components [1,8,12,13,15,[17][18][19][20]. This strongly restricts the conventional application of Saint Venant's principle in designing structures made of CMs. The way the edge effect decays, the geometry of its zone, and the distribution of stresses and strains in the edge effect zone depend on the ratio of the sizes of the region of variation in the external load and the structural inhomogeneity of the material. For example, edge effects in unidirectional fiber-reinforcement composites of regular structure associated with the redistribution of the external load between the matrix and the fibers subject to longitudinal tension were analyzed in [4]. The problem was formulated for a periodicity cell in a hexagonal model of the microstructure. It was shown that the edge effect size is on the order of one to two typical length scales of the internal structure of a CM. Similar results were obtained in [2, 3] for a two-layer periodicity cell of a CM with uniformly loaded reinforcement. As shown in [1,12], the edge effect zone is much larger if the size of the periodicity cell is determined by the period of the surface load and exceeds the typical length scale of the internal structure of the CM. The asymptotic dependence of the edge effect length on the size of the periodicity cell along the line of application of the surface load allows us to isolate a representative element of the material [8]. A representative element inherits the structure of an inhomogeneous materia...