The application of reliability methods in the design of stiffened FRP composite panels for marine vessels

The use of composite laminate materials has increased rapidly in recent years due to their excellent strength to weight ratio and resistance to corrosion. In the construction of marine vessels, stiffened plates are the most commonly used structural elements, forming the deck, bottom hull, side shells and bulkheads. This paper presents the use of a stochastic approach to the design of stiffened marine composite panels as part of a current research programme into developing stochastic methods for composite ship structures, accounting for variations in material properties, geometric indices and processing techniques, from the component level to the full system level. An analytical model for the solution of a stiffened isotropic plate using a grillage analogy is extended by the use of equivalent elastic properties for composite modelling. This methodology is applied in a reliability analysis of an isotropic (steel) stiffened plate before the final application for a reliability analysis for a FRP composite stiffened plate

Genetic algorithms (GAs) based optimisation of FRP composite plated grillages in ship structures

Design optimisation of ship structures is complicated by the material choice and application of Fibre Reinforced Polymer (FRP) composites. Their numerous advantages and the number of design, material and fabrication variabilities necessitate a systematic approach for determining the most suitable design solution. The development of an optimisation framework capable of application to composite ship structures is described herein. This broadly consists of structural analyses for exemplar ship structure topologies (e.g. tophat stiffened laminated plates) coupled with a Genetic Algorithm optimisation procedure. With the adoption of a GA, the framework can deal with a number of discrete design variables and search the resulting large design space for a global optimum. The validation of the methodology is presented, as well as a study of the effect of parametric variation and applications to ship structure

Implications of failure criteria choices on the rapid concept design of composite grillage structures using multiobjective optimisation

Grillage topologies are commonly used in many composite structural applications to produce low mass designs that have a high stiffness. While composite failure criteria are being compared in many different simple structures, for example plates and tubes, literature must also compare more complicated applications, including grillages, as there are distinct differences in behaviour. This paper therefore performs analysis of grillage structures with more up to date failure criteria, taken from the world wide failure exercise, than previously investigated. The grillage theory selected is that of Navier theory with elastic equivalent properties due to its low computational expense for use with a genetic algorithm to optimise a composite structure. The results take an example from leisure boatbuilding showing the grillages produced from the different limit states, comparing the cost and mass. The final results show that the method allows a rapid analysis of grillages and that the selection of the limit state has an important effect on the optimised grillage topolog