Reliability-based design of symmetric laminated plate with initial imperfection

Abstract

This study is concerned with the reliability-based design of a simply supported symmetric laminated plate with an initial imperfection under bi-axial compression load. For a plate loaded in compression, a small initial imperfection can cause large bending stresses that reduces the load at which the ply failure occurs. The failure is modeled as a series system consisting of both the buckling failure and the material strength failure. For the reliability analysis, the initial imperfection, material properties and applied loads are treated as random variables. The mode reliability is evaluated by the first order reliability method. Then, the system reliability is approximated by Ditlevsen's upper bound, which is used as an objective function of the reliability maximization. The optimum laminate configuration is determined such that the reliability for the failure may be maximized in terms of the ply orientation angles of individual layers. Through numerical calculations, the reliability-based design is demonstrated to be important for the structural safety.