Composite aerofoil
A composite aerofoil, the aerofoil having a leading edge, a trailing edge a pressure side and a suction side and comprising an outer erosion protection layer along one or both of the pressure side or suction side, a structural core having a plurality of resin impregnated plies of unidirectional fibers, and between the outer erosion protection layer and the structural core a woven composite impregnated with a resin having a modulus of elasticity greater lower than that of the resin impregnating the plies in the structural core.
1. A composite aerofoil, the aerofoil having a leading edge, a trailing edge, a pressure side and a suction side and comprising
an outer erosion protection layer along one or both of the pressure side or and the suction side,
a structural core having a plurality of resin impregnated plies of unidirectional fibres, and
between the outer erosion protection layer and the structural core a woven composite impregnated with a resin having a modulus of elasticity greater lower than that of the resin impregnating the plies in the structural core, the woven composite being located near a tip of the aerofoil.
2. A composite aerofoil according to claim 1 , wherein the outer erosion protection layer has a hardness between Shore A50 A 50 and Shore D 60.
3. A composite aerofoil according to claim 2 , wherein the hardness is Shore A 90.
4. A composite aerofoil according to claim 2 , wherein the outer erosion protection layer is polyurethane.
5. A composite aerofoil according to claim 1 , wherein the resin impregnating the structural core is an epoxy resin.
6. A composite aerofoil according to claim 1 , wherein the resin impregnating the woven composite is a thermosetting nitrile phenolic adhesive.
7. A composite aerofoil according to claim 4 , wherein the erosion protection layer is between 0.1 and 0.5 mm thick.
8. A method of manufacturing a composite aerofoil comprising the steps of
providing a structural core having a plurality of resin impregnated plies of unidirectional fibres, the resin within the plies having a predetermined modulus of elasticity;
providing a woven composite layer impregnated with a resin having a modulus of elasticity greater lower than that of the resin impregnating the plies in the structural core, the woven composite layer located near a tip of the aerofoil; and
consolidating the structural core and the woven composite layer by placing them in contact and applying heat.
9. A method according to claim 8 , further comprising the step of joining an erosion protection layer to the woven composite layer using an adhesive layer.
10. A method according to claim 9 , wherein the adhesive is layer comprises a nitrile phenolic resin.
11. A method according to claim 8 , wherein the resin impregnating the woven composite layer is a nitrile phenolic resin.
12. A method according to claim 11 , wherein the resin impregnating the structural core is an epoxy.
13. A composite aerofoil according to claim 1 , wherein the outer erosion protection layer is polyurethane having a hardness between Shore A50 A 50 and Shore D 60 and the resin impregnating the structural core is an epoxy resin.
14. A composite aerofoil according to claim 1 , wherein the outer erosion protection layer is polyurethane having a hardness between Shore A50 A 50 and Shore D 60 and the resin impregnating the woven composite is a thermosetting nitrile phenolic adhesive.
15. A composite aerofoil according to claim 14 , wherein the resin impregnating the structural core is an epoxy resin.