Method of manufacturing a fan blade and a fan blade

1. A method of manufacturing a fan blade for a gas turbine engine, the method comprising:

providing a compression mould having an internal mould surface corresponding to an outer profile of a fan blade;

providing opposing first and second laminates to form a shell corresponding to the mould surface, each laminate comprising a lay-up of plies of fibre reinforcement material;

applying a core material comprising quasi-isotropic short fibre reinforced resin in the compression mould so that with the compression mould in a moulding configuration the core material is enclosed by the shell, the core material and the shell forming a pre-form for the fan blade;

applying pressure to compress the pre-form so that it conforms to the mould surface; and

applying heat to cure the pre-form,

wherein the pre-form includes a root portion and a blade portion, and the core material within the root portion is no more than 50% of the thickness of the root portion, and the core material within the blade portion is no more than 30% of the thickness of the blade portion.

2. The method according to claim 1 , wherein the method comprises:

providing the first laminate on a first mould surface of a first mould part of the compression mould which defines a respective portion of the internal mould surface, wherein the core material is applied on the first laminate;

providing the second laminate over the core material or on a second mould surface of a second mould part of the compression mould which defines a respective portion of the internal mould surface; and

assembling the first and second mould parts into the moulding configuration so that the core material is enclosed by the first and second laminates of the shell.

3. The method according to claim 1 , wherein the method comprises:

providing the first laminate on a first mould surface of a first mould part of the compression mould which defines a respective portion of the internal mould surface;

providing the second laminate on a second mould surface of a second mould part of the compression mould which defines a respective portion of the internal mould surface;

assembling the first and second mould parts into the moulding configuration so that a cavity is formed between the first and second laminates of the shell; and

wherein core material is applied into the cavity after assembly of the compression mould.

4. The method according to claim 1 , wherein providing the first laminate or the second laminate comprises laying up plies of fibre reinforcement material on the internal mould surface of the compression mould.

5. The method according to claim 1 , wherein the core material is applied to extend from a terminal root end of the preform, corresponding to a root end of the fan blade, along a longitudinal extent of the pre-form.

6. The method according to claim 5 , comprising applying pressure to the core material at or through the root end with a piston, such that the core material drives the shell against the mould surface of the compression mould, and optionally wherein the piston applies direct pressure only to the core material.

7. The method according to claim 1 , wherein the core material is applied to define a tapered profile in the root portion of the pre-form.

8. The method according to claim 1 , wherein the first and second laminates of the shell are provided so that they have a substantially constant thickness in regions adjacent the core material.

9. The method according to claim 1 , wherein the viscosity of the core material is lower than the viscosity of the first and second laminate material.

10. The method according to claim 1 , wherein an initial quantity of core material is applied in the compression mould before the compression mould is closed for forming, and wherein the initial volume corresponds to at least 90% of the volume inside the shell when the shell conforms to the mould surface.

11. The method according to claim 1 , wherein the core material flows within the shell under pressure.

12. The method according to claim 1 , wherein pressure is applied at least partly by opposing action of first and second mould parts, and wherein a pressure-maintaining device acts on the core material to maintain pressure.

13. The method according to claim 12 , wherein the pressure maintaining device drives core material into the shell, or wherein the pressure maintaining device permits core material to flow out of the shell.

14. The fan blade for a gas turbine engine comprising a core and a surrounding shell, wherein the core comprises a quasi-isotropic short fibre reinforced resin, and the shell comprises laminate comprising plies of fibre reinforcement material, and wherein the fan blade is manufactured in accordance with claim 1 , such that the core and shell are compression moulded and cured together.

15. A fan blade for a gas turbine engine comprising a core and a surrounding shell, wherein the core comprises a quasi-isotropic short fibre reinforced resin, and the shell comprises laminate comprising plies of fibre reinforcement material,

wherein the fan blade includes a root portion and a blade portion, and the core material within the root portion is no more than 50% of the thickness of the root portion, and the core material within the blade portion is no more than 30% of the thickness of the blade portion.

16. The fan blade according to claim 15 , wherein the core material extends from a terminal root end of the fan blade along a longitudinal extent of the fan blade.

17. The fan blade according to claim 15 , wherein at least one of (i) the core defines a tapered profile at the root portion of the fan blade, and (ii) the laminate shell has a substantially constant thickness through the fan blade.

18. The fan blade according to claim 15 , wherein the resin of the core and the resin of the shell is continuous between the core and the shell.

19. The fan blade according to claim 15 , wherein there is no adhesive layer between the core and the shell.

20. The fan blade according to claim 15 , wherein there are substantially no voids at an interface region between the core and the shell.