Determination of robustness for a stiffened composite structure using stochastic analysis

It is a common practice to only consider the nominal means as input variables for both classical solid mechanics and finite element (FE) analysis problems. A single solution based on the mean values is then used in design. In reality all input variables are stochastic, existing within a range of possible values. Different combinations of these stochastic input variables will lead to differing output responses and the introduction of variability will cause each structure to have a response that deviates from the original specification, sometimes with catastrophic consequences. In this paper two variables, influence and sensitivity, have been identified as parameters affecting structural robustness. Variability and uncertainty in loads, geometry and lamina stiffness are introduced via a stochastic finite element analysis (SFEA) procedure. The procedure is applied to the design of composite yacht hulls comparing the robustness of designs aimed at satisfying a range of performance and cost requirements. It is shown that influence and sensitivity are useful in identifying designs that lead to imperfection tolerant structures.