Fiber orientation and shape of structure create directional effects which must be taken into account in mechanical behaviour of composite materials. This sensitivity with respect to strain and failure is analyzed by considering the feature of loading (direction and type which depend on sign of stress).To describe damage we define iso-strain criterion by quadratic surface in the space of stress. For failure we use a quadratic surface similar to Hill criterion, the coefficients of which depends on loading cycles, for each type and direction of loading.Computations are validated on unidirectional glass/epoxy and graphite/epoxy composite materials.
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