Composite aerofoil

Abstract

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.

The invention claimed is: 
     
       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.