Parametric identification of coefficients for fatigue stiffness degradation model of a composite material

Abstract

The problem of finding the fatigue characteristics of a composite material based on test results is considered. As a mathematical model of stiffness degradation, a non-linear ordinary differential equation with five unknown parameters is used, reflecting characteristic changes in the properties of the material. It is required to find such parameter values that the solution of the differential equation describes the available test re- sults with sufficient accuracy. The solution procedure is reduced to the problem of optimizing the objective function, the value of which characterizes the achieved accuracy. The optimization methods used were a method that simulates the behavior of a flock of moths and a method of sequential reduction of the search set. A step-by-step algorithm for finding the unknown parameters of the model is proposed, and numerical results are presented for processing three versions of experimental data containing information about the change in the elastic modulus of the composite material during the application of load cycles.