Material anisotropy and sweep effects on the hydroelastic response of lifting surfaces

Abstract

The objective is to study the hydroelastic response of composite cantilevered plates as a combined function of the material anisotropy and geometric sweep angle. For plates with a positive incidence angle, if the fibers are aligned towards the leading edge, nose-down deformations occur, which reduces lift and delays static divergence. If the fibers are aligned towards the aft, nose-up deformations occur, and the deformations increase (decrease) with forward (backward) sweep. For the cases examined, coupled-mode flutter was observed for plates in air. In water, however, flutter was caused by the emergence of a new low-frequency mode at high flow speeds. Backward sweep accelerates flutter in air, but delays flutter in water. The effect of the sweep angle was found to be secondary in contrast to the effective fiber angle. For the plates in air, the highest critical speed corresponds to a foil with a slight forward sweep with fibers aligned along the spanwise direction. For the same plate in water, a backward swept hydrofoil with fibers aligned toward the inflow was found to be the best combination to avoid divergence and flutter.