Delaminations in composite beams under cyclic bending are considered taking into account buckling of delaminations and damage accumulation in the interlayer. Local interlaminar tensile and shear stresses near the tips of delaminations are estimated in the framework of the theory of multilayered structures. Two damage measures are introduced in which accumulation is governed with the ranges of tensile and shear stresses in the interlayer. It is assumed that the generalized force characterizing the resistance to the tip propagation depends on both damage measures. The driving generalized force is calculated from the energy balance consideration taking into account buckling of the delamination. It is shown that, in the generic case, the fatigue life of delaminations in beams subjected to bending consists of the initiation stage with the fixed tips, the stage of rapid growth, and the final stage of the slowly retarding growth. When the damage accumulation threshold is comparatively high, the latter stage terminates in complete arrest of the delamination.
展开▼
