Development of Criterion for Long-Term Failure Due to Creep of Thin-Walled Layered Structures

A model and criterion for long-term creep failure for thin-walled laminated shells with consideration of the effect of a stress state are developed. The problems of calculating the time to failure under combined loading are considered. Solutions are based on the concept of equivalent stresses. The problem of determining local stresses in unidirectional and layered composites of random structure is stated within the framework of the second-order nonlinear theory. The solution to the stochastic boundary value problem on determining the stress concentration in a unidirectional composite with a metal matrix is obtained. The method of successive approximations is used to obtain a complete system of second-order equations. The parameters of stress concentration at the boundary of components are determined. These examples show the importance of the effect of nonlinear properties on the stress redistribution near the fibers. The possibility of predicting the long-term strength of the material is shown. The necessary information about the material for the statement of failure criteria is the long-term strength curves for the individual components of the combined stresses.