Adapting ply drop positions for compensating fabric changes—Application to swimming monofins

Composite structures manufactures sometimes have to change their material, either in an attempt to reduce their costs, or because of their provider’s policies. If the structure’s behavior has to stay constant, some re-design is necessary to compensate for material variations. In tapered composite structures, ply drop positions can be moved for such purpose. The present article describes an application to swimming monofins. The intuitive concepts used by swimmers to characterize monofins are translated here into two criteria: the deflection under static loading and the natural frequencies. The ply drop positions with the thicker prepeg are optimized, so that the deformed configuration and natural frequencies are as close as possible to those of the reference monofin. Numerical simulations based on the finite element method provide the deflections and natural frequencies of the various models. The optimization problem is solved with the Globalized and Bounded Nelder–Mead (GBNM) algorithm (Luersen et al. (2004) [1]). The ply drop positions identifications of two monofins with different characteristics are carried out and the results are discussed.