Acoustic abatement panel fabrication

1. A method of making an aircraft acoustic structural panel ( 10 ) comprising:

pressing preformed foam ( 3 ) against a core honeycomb ( 1 ) having honeycomb cells ( 14 ), and reducing thickness of said preformed foam ( 3 ) to adhesively bond and fully compress respective portions of said preformed foam ( 3 ) into said honeycomb cells ( 14 ) to preform a core honeycomb laminate ( 12 );

stacking said preformed core honeycomb laminate ( 12 ) between directly adjoining opposite top and bottom structural outer laminates ( 16 , 18 ) having corresponding structural outer skins ( 20 , 22 ); and

compressing together under heat and pressure said stacked core honeycomb laminate ( 12 ) and structural outer laminates ( 16 , 18 ) into a unitary aircraft acoustic structural panel ( 10 ) having said core honeycomb laminate ( 12 ) integrally bonded between said outer skins ( 20 , 22 ).

2. A method of making an aircraft acoustic structural panel ( 10 ) comprising:

supplying preformed uniform foam in a foam layer ( 3 );

stacking said foam layer ( 3 ) atop an adhesive layer ( 2 ) and in turn atop a core honeycomb ( 1 );

compressing together said stacked foam layer ( 3 ), adhesive layer ( 2 ), and core honeycomb ( 1 ) under pressure and heat to reduce the thickness and thermally bond respective portions of said foam layer ( 3 ) fully compressed inside said honeycomb cells ( 14 ) to preform a core honeycomb laminate ( 12 );

stacking said preformed core honeycomb laminate ( 12 ) between opposite top and bottom structural outer laminates ( 16 , 18 ); and

compressing together under heat and pressure said stacked core honeycomb laminate ( 12 ) and structural outer laminates ( 16 , 18 ) into a unitary structural aircraft acoustic structural panel ( 10 ) having said core honeycomb laminate ( 12 ) integrally bonded between outer skins ( 20 , 22 ).

3. The method according to claim 2 wherein said structural outer laminates ( 16 , 18 ) comprise an imperforate acoustic septum ( 4 ) directly adjoining said preformed core honeycomb laminate ( 12 ) disposed inboard of said outer skins ( 20 , 22 ).

4. The method according to claim 2 , wherein said stacking and compressing of said preformed core honeycomb laminate ( 12 ) between said opposite top and bottom structural outer laminates ( 16 , 18 ) further comprises:

stacking atop opposite sides of said preformed core honeycomb laminate ( 12 ) in turn a prepreg epoxy-fiber septum ( 4 ), an outer honeycomb ( 5 ), and a plurality of prepreg epoxy directional structural fiber layers ( 6 , 7 , 8 ) to form a collective stack ( 12 , 16 , 18 ); and

compressing together under heat and pressure said collective stack to cure and form said unitary aircraft acoustic structural panel ( 10 ) having said preformed core honeycomb laminate ( 12 ) bonded in the middle between said structural outer laminates ( 16 , 18 ) each structural outer laminate ( 16 , 18 ) including a corresponding one of said outer honeycombs ( 5 ) bonded between said outer skins ( 20 , 22 ).

5. The method according to claim 4 wherein said directional structural fiber layers ( 6 , 7 , 8 ) comprise a first unidirectional fiber layer ( 6 ) directly adjoining said outer honeycomb ( 5 ) followed in turn by a second unidirectional fiber layer ( 7 ) disposed transversely to said first unidirectional layer ( 6 ) and terminating in a woven fiber layer ( 8 ) exposed outboard.

6. The method according to claim 4 wherein said directional structural fiber layers ( 6 , 7 , 8 ) are imperforate to collectively define imperforate outer skins ( 20 , 22 ).

7. The method according to claim 2 wherein said honeycomb cells ( 14 ) have sharp edges and said foam layer ( 3 ) and adhesive layer ( 2 ) are cut by said sharp edges as said foam layer ( 3 ) is compressed atop said core honeycomb ( 1 ) to fill each cell ( 14 ) with a respective portion of said foam layer ( 3 ).

8. The method according to claim 7 wherein said foam layer ( 3 ) has an initial thickness (F) about twice the height (H 1 ) of said honeycomb cells ( 14 ) and is fully compressed into said cells ( 14 ), and retained therein by said adhesive.

9. The method according to claim 7 wherein said honeycomb ( 1 ) is metal with thin sidewalls ( 24 ) being sufficiently sharp to cut said foam layer ( 3 ) during said compression.

10. The method according to claim 9 wherein said foam layer ( 3 ) is sufficiently soft for being cut by said honeycomb cells ( 14 ) during said compression without damaging said honeycomb cells ( 14 ).

11. The method according to claim 7 wherein:

said foam layer ( 3 ) has an initial thickness (F/2) about the height (H 1 ) of said honeycomb cells ( 14 );

two of said foam layers ( 3 ) are disposed on opposite sides of said core honeycomb ( 1 ) with said adhesive layer ( 2 ) directly adjoining said core honeycomb ( 1 ) under only one of said foam layers ( 3 ); and

both of said foam layers ( 3 ) are compressed into said honeycomb cells ( 14 ) from opposite sides of said core honeycomb ( 1 ) to fill corresponding halves of said cells ( 14 ).

12. The method according to claim 2 wherein said structural outer laminates ( 16 , 18 ) comprise:

an imperforate acoustic septum ( 4 ) directly adjoining said preformed core honeycomb laminate ( 12 ) disposed inboard of said outer skins ( 20 , 22 );

an outer honeycomb ( 5 ) directly adjoining said acoustic septum ( 4 ); and

a plurality of directional structural fiber layers ( 6 , 7 , 8 ) defining said outer skins ( 20 , 22 ).

13. The method according to claim 12 wherein:

said preformed core honeycomb laminate ( 12 ) includes said foam ( 3 ) filling each of said honeycomb cells ( 14 ) substantially completely with foam plugs, with at least some of said cells having voids ( 32 ) devoid of foam below said plugs; and

said outer honeycomb ( 5 ) includes empty cells ( 14 ).

14. The method according to claim 13 wherein said outer skins ( 20 , 22 ) are imperforate.

15. A method of making an aircraft acoustic structural panel ( 10 ) comprising:

supplying preformed uniform foam in a foam layer ( 3 );

stacking said foam layer ( 3 ) atop an adhesive layer ( 2 ) and in turn atop a core honeycomb ( 1 ) having honeycomb cells ( 14 ); and

compressing together said stacked foam layer ( 3 ), adhesive layer ( 2 ), and core honeycomb ( 1 ) under pressure and heat to thermally bond said foam layer ( 3 ) inside said honeycomb cells ( 14 ) to preform a core honeycomb laminate ( 12 );

stacking said preformed core honeycomb laminate ( 12 ) between opposite top and bottom structural outer laminates ( 16 , 18 ); and

compressing together under heat and pressure said stacked core honeycomb laminate ( 12 ) and outer structural laminates ( 16 , 18 ) into a unitary aircraft acoustic structural panel ( 10 ) having said core honeycomb laminate ( 12 ) integrally bonded between outer skins ( 20 , 22 ); and

wherein each of said structural outer laminates ( 16 , 18 ) comprises:

an imperforate acoustic septum ( 4 ) directly adjoining a corresponding opposite side of said preformed core honeycomb laminate ( 12 );

an outer honeycomb ( 5 ) directly adjoining said imperforate acoustic septum ( 4 ); and a plurality of directional structural fiber layers ( 6 , 7 , 8 ) defining said outer skins ( 20 , 22 ).

16. The method according to claim 4 wherein said honeycomb cells ( 14 ) of said core honeycomb laminate ( 12 ) have sharp edges, and said foam layer ( 3 ) and adhesive layer ( 2 ) are cut by said sharp edges as said foam layer ( 3 ) is compressed atop said core honeycomb ( 1 ) to fill each honeycomb cell ( 14 ) with a respective portion of said foam layer ( 3 ).

17. The method according to claim 16 wherein:

said core honeycomb ( 1 ) comprises metal;

said outer honeycombs ( 5 ) comprise non-metal; and

said core honeycomb ( 1 ) is taller than said outer honeycombs ( 5 ), with correspondingly wider cells ( 14 ).