Structural analysis and design optimization of a sailboat composite hull

Federico Urban, Carlo Poloni (ESTECO)

The use of composites in marine industry is predicted to increase for many years to come. This is mainly due to the excellent strength-to-weight ratios, damping characteristics, corrosion resistance and design freedom for sleek looking parts that composites have to offer. Composite parts typically contain fibers that are made out of glass, carbon, and wood, among many others, which act as a reinforcement and increase mechanical properties.
When molding composite parts fibers will tend to orient in different directions. 

This orientation improves mechanical properties in the fiber direction while diminishing in the transverse direction.Taking as example a sailboat composite hull, the importance of the fiber orientation has been examinated to reduce structure stresses. 

In order to model all the rigging loads at sailing point a close-hauled at a wind speed of 35 knots has been set. Moreover, to represent the falling down from wave crest, also accelerations and hull hydrostatic pressure have been considered. The sailboat model has been provided with a complete constraint on the ballast.When evaluating the structure response at sailing point, it has been noticed too much critical zones in terms of Maximum Stress Failure Criterion. Moreover, every change in each lay up configuration has led to different stress-strain fields and then to a not easily recognizable location of maximum stresses.

Thanks to modeFRONTIER help, it was possible to explore quickly and efficiently the design space by parameterizing only the fiber orientation angles of the composite elements of the sailboat.

The goals of the optimization were to minimize maximum stress of frame, floor and interior components. To achieve the best trade-off, three constraints had to be satisfy, about controlling stresses of hull, floor and also about inter laminar stress. After a sampling DOE phase composed of 64 individuals, an exploration phase followed using MOGA for 20 generations. The obtained results showed two possible good solutions to pursue the trade-off between the objectives.