Patent ID: 8777577

Claim:
A hybrid fan blade for a gas-turbine engine which comprises: a supporting structure of a fiber-composite material, and a metallic enveloping structure having a convex suction-side sheet-metal cover and a concave pressure-side sheet-metal cover connected to the latter, wherein the enveloping structure is confined to an airfoil area and the suction-side sheet-metal cover having an elastic tension transverse to a longitudinal axis of the hybrid fan blade and extending from a leading edge of the suction-side sheet-metal cover to a trailing edge of the suction-side sheet-metal cover when stationary such that the pressure-side sheet-metal cover is subjected to elastic compressive stress transverse to the longitudinal axis of the hybrid fan blade and extending from a leading edge of the pressure-side sheet-metal cover to a trailing edge of the pressure-side sheet-metal cover when stationary and both sheet-metal covers elastically press against the supporting structure with elastic pre-stress from a leading edge of the supporting structure to a trailing edge of the supporting structure, the elastic pre-stress initially occurs when the hybrid fan blade is stationary, before operation of the hybrid fan blade; the supporting structure and enveloping structure thereby forming the hybrid fan blade for the gas-turbine engine.