Using the model of quasi-static crack growth and test result of the double cantilever beam (DCB) sample of layered carbon/epoxy composite, the general regularities of the interlaminar crack resistance of mode 1 were studied. The main efforts are focused to specific features of delamination (crack) growing under mechanical load and the non-homogeneity of the interlaminar crack resistance of layered composite. It is showed that in nominally brittle material the crack continuously and stably grows before the external load reaches a critical state, and the interlaminar fracture toughness is a local characteristic of crack resistance and changes as random function of a crack tip position. There are obtained statistical estimates of the maximum crack resistance and the crack resistance of crack arrest. Some regularities of unstable stage of crack growth are investigated. The saw-type of variable interlaminar fracture toughness is used in simulation of quasi-static crack growth. It is showed that the predicted behavior of the DCB sample with control of extension in general corresponds to the one observed in test.