MATHEMATICAL MODEL FOR PREDICTING THE DURABILITY OF COMPOSITE MATERIALS IN FATIGUE TESTS

Assessments of the durability of products made from metallic materials are carried out on the basis of safe durability model and/or on the basis of the concept of safe development of crack. Extensive operating experience and accumulated volume of experimental data give sufficient confidence to designers when metal products designing with the required durability. Unlike metals, composite materials represent a heterogeneous and anisotropic medium. The inherent structure of composite materials considerably complicates the nature of development of technological defects and operational damages from the moment of crack starting until the carrying capacity of the product. As a result, all this leads to a revision of the guidelines ( see, for example, [1]), as the concepts of safe development of crack, and models a safe life. In the present work the changing of residual strength of composite material at cyclic testing is studied within the safe life model and its relation with the characteristics of static strength. At this the cyclic stress amplitude may be both constant with asymmetry coefficient R to zero and valuable.