Stable crack growth in composite laminates under various stiffness of the loading system

The work is devoted to experimental study of stable and unstable crack growth processes in composite materials. The eccentric tension tests of the compact specimens of glass-epoxy composite laminates in conditions of various stiffness of the loading system were carried out. Different measurement techniques of crack opening displacement were used in work. During the analysis of results of a tension test of compact specimens with crack, descending sections of the loading curves were considered by analogy with postcritical deformation stage, which could be found in test of smooth specimens of different materials. It is shown that behavior of composite specimens with crack under tension depends on the loading system parameters: crack grows process is stable when stiffness of the loading system is enough, crack opening displacement rate increase under reduction of stiffness of the loading system. This effect should be take into account during modeling and analyzing of fracture processes of composite materials, strength and survivability assessment of composite structures in real loading conditions.