Machinable composite material

1. An aircraft which includes primary aircraft structures, said aircraft comprising:

a first part, comprising a fibrous structure comprising unidirectional fibers and a cured resin matrix, said fibrous structure having at least one surface and a layer that is located on said surface, said layer comprising a cured quasi-isotropic prepreg, said layer having been machined to provide a machined surface; and

a primary aircraft structure that is attached to said first part, said primary aircraft structure comprising at least one surface that fits against said machined surface on said first part.

2. An aircraft according to claim 1 wherein said first part and said primary aircraft structure second part are attached together with a fastener.

3. An aircraft according to claim 1 wherein said first part comprises a second surface and a second layer that is located on said second surface, said second layer comprising a cured quasi-isotropic prepreg, said second layer having been machined to provide a second machined surface and wherein said primary aircraft structure comprises a second surface that fits against said second machined surface on said first part.

4. An aircraft according to claim 3 wherein said first part and said primary aircraft structure are attached together with a fastener.

5. An aircraft according to claim 3 wherein said first part comprises a third surface and a third layer that is located on said third surface, said third layer comprising a cured quasi-isotropic prepreg, said third layer being machined to provide a third machined surface and wherein said primary aircraft structure comprises a third surface that fits against said third machined surface on said first part.

6. An aircraft according to claim 5 wherein said first part and said primary aircraft structure are attached together with a fastener.

7. An aircraft according to claim 3 wherein said first and second surfaces are located on said primary structure so as to define an opening in which said first part is located to thereby provide said fitting of said first machined surface against said first surface of said primary aircraft structure and to provide said fitting of said second machined surface against said second surface of said primary aircraft structure.

8. An aircraft according to claim 7 wherein a third surface is located on said primary aircraft structure so as to define an end to said opening in which said first part is located, said first part comprising a third surface and a third layer that is located on said third surface of the first part, said third layer comprising a cured quasi-isotropic prepreg, said third layer having been machined to provide a third machined surface that fits against said third surface of said primary aircraft structure.

9. An aircraft according to claim 3 wherein said first and second machined surfaces are located on said first part so as to define an opening in which said primary aircraft structure is located to thereby provide said fitting of said first machined surface against said first surface of said primary aircraft structure and to provide said fitting of said second machined surface against said second surface of said primary aircraft structure.

10. An aircraft according to claim 9 wherein said first part comprises a third surface and a third layer that is located on said third surface of the first part, said third layer comprising a cured quasi-isotropic prepreg, said third layer having been machined to provide a third machined surface that is located on said first part so as to define an end to said opening in which said primary aircraft structure is located, said primary aircraft structure comprising a third surface that fits against said third machined surface.

11. An aircraft according to claim 7 wherein said first part and said primary structure are attached together with a fastener.

12. An aircraft according to claim 9 wherein said first, part and said primary aircraft structure are attached together with a fastener.