Relialility Analysis of Laminated Composite Plate with Initial Imperfection.

Abstract

This paper describes the reliability analysis of a simply-supported laminated composite plate with an initial imperfection under a bi-axial compression load. For a plate loaded in compression, a small initial imperfection can cause large bending stress that decreases a plate failure load. The first ply failure criterion is adopted as that of the plate failure. On the reliability analysis, the laminated composite plate is modeled as a series system consisting of the composed plies, which means that failure in any one ply reduces to failure of the plate. The initial imperfection, material properties and applied loads are considered as random variables. The mode reliability is evaluated by the first order reliability method (FORM). The system reliability is approximated by Ditlevsen's upper bound. Through numerical calculations, the effect of variations of the random variables is evaluated on the reliability. The change of the reliability in terms of ply orientation angles is also investigated. The reliability-based optimum design is demonstrated to be different from the design of deterministic strength maximization. The results show the importance of considering variations of the random variables for the safety of a laminated composite plate.