Composite integrally bladed rotor

1. An integrally bladed rotor for use in a gas turbine engine comprising:

a plurality of pairs of airfoil blades;

each pair of blades having a spar which extends from a first end tip at an outer end of a first one of said airfoil blades in said pair to a diametrically opposed second end tip at an outer end of a second one of said airfoil blades in said pair;

an outer shroud integrally joined to the first and second tips in each pair of airfoil blades;

each said spar has a first arm and second arm spaced from said first arm in a central portion of said spar;

said first arm and said second arm define an opening and said opening allowing said spars to be interwoven; and

a filler ply assembly filling a central portion of said rotor.

2. An integrally bladed rotor according to claim 1 , further comprising an inner diameter hub and said spar in each said pair of blades passing through said inner diameter hub.

3. An integrally bladed rotor according to claim 1 , wherein said filler ply assembly is formed from a near isotropic, continuous weave fabric lay-up.

4. An integrally bladed rotor according to claim 1 , further comprising said spar in each said pair of blades being formed from a composite material.

5. An integrally bladed rotor according to claim 1 , wherein said spars associated with said pairs of airfoil blades are interwoven and said filler ply assembly comprises a plurality of stacked filler plies.

6. An integrally bladed rotor according to claim 5 , wherein said spars are interwoven in a spiral pattern and said plurality of stacked filler plies are arranged in a complimentary spiral pattern.