Acoustic abatement panel fabrication

1. An aircraft acoustic structural panel ( 10 ) made by the method comprising:

compressing together under pressure and heat a stack including a preformed uniform foam layer ( 3 ), a layer of adhesive ( 2 ), and a core honeycomb ( 1 ) having a plurality of honeycomb cells ( 14 ) and thereby pressing said preformed uniform foam layer ( 3 ) substantially flush atop said core honeycomb ( 1 ) to form corresponding foam plugs from said preformed uniform foam layer ( 3 ) being thermally bonded inside said honeycomb cells ( 14 ) by said adhesive ( 2 ), with said preformed uniform foam layer ( 3 ) being initially thicker than said core honeycomb ( 1 ) and fully compressed into 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 ) having corresponding outer skins ( 20 , 22 ); and

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

2. An aircraft acoustic structural panel ( 10 ) made by the method comprising:

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

stacking said preformed uniform foam layer ( 3 ) atop an adhesive layer ( 2 ) and in turn atop a core honeycomb ( 1 ) having a plurality of honeycomb cells ( 14 ), with said preformed uniform foam layer ( 3 ) being thicker than said core honeycomb ( 1 ); and

compressing together said stacked preformed uniform foam layer ( 3 ), adhesive layer ( 2 ), and core honeycomb ( 1 ) under pressure and heat to press said preformed uniform foam layer ( 3 ) substantially flush atop said core honeycomb ( 1 ) to form corresponding foam plugs from said preformed uniform foam layer ( 3 ) having reduced thickness inside said honeycomb cells ( 14 ), and thermally bond said foam plugs 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 ( 10 , 18 ) having corresponding 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 structural panel ( 10 ) defining said aircraft acoustic structural panel having said core honeycomb laminate ( 12 ) integrally bonded between said outer skins ( 20 , 22 ).

3. The panel 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 ) and disposed inboard of said outer skins ( 20 , 22 ).

4. The panel according to claim 3 wherein each of said structural outer laminates ( 16 , 18 ) comprises:

said 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 ).

5. The panel according to claim 2 wherein said stacking and compressing of said preformed core honeycomb laminate ( 12 ) between said 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; and

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

6. The panel according to claim 5 wherein said prepreg epoxy 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.

7. The panel according to claim 5 wherein said prepreg epoxy structural fiber layers ( 6 , 7 , 8 ) are imperforate to collectively form the outer skins ( 20 , 22 ) as imperforate outer skins ( 20 , 22 ).

8. The panel according to claim 2 wherein said honeycomb cells ( 14 ) have sharp edges and said preformed uniform foam layer ( 3 ) and adhesive layer ( 2 ) are cut by said sharp edges as said preformed uniform foam layer ( 3 ) is compressed atop said core honeycomb ( 1 ) to fill each cell ( 14 ) said foam plugs.

9. The panel according to claim 8 wherein said preformed uniform 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.

10. The panel according to claim 8 wherein said core honeycomb ( 1 ) is metal with thin sidewalls ( 24 ) being sufficiently sharp to cut said preformed uniform foam layer ( 3 ) during said compression.

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

12. The panel according to claim 8 wherein:

said preformed uniform foam layer ( 3 ) comprises two preformed uniform foam layers ( 3 ) each having an initial thickness (F/2) about the height (H 1 ) of said honeycomb cells ( 14 );

said two preformed uniform 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

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

13. The panel 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 imperforate acoustic septum ( 4 ); and

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

14. The panel according to claim 13 wherein:

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

said outer honeycomb ( 5 ) includes empty cells.

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

16. An aircraft structural panel ( 10 ) comprising:

a preformed center honeycomb laminate ( 12 ) made by supplying preformed foam in a uniform foam layer ( 3 ), and then stacking said preformed uniform foam layer ( 3 ) atop an adhesive layer ( 2 ) and in turn atop a center honeycomb ( 1 ) having a plurality of honeycomb cells ( 14 ), with said preformed uniform foam layer ( 3 ) being thicker than said center honeycomb ( 1 );

and compressing together said stacked preformed uniform foam layer ( 3 ), said adhesive layer ( 2 ), and said center honeycomb ( 1 ) under pressure and heat to press said preformed uniform foam layer ( 3 ) substantially flush atop said center honeycomb ( 1 ) to form corresponding foam plugs from said preformed uniform foam layer having reduced thickness inside said honeycomb cells ( 14 ), and thermally bond said foam plugs inside said honeycomb cells ( 14 ) to preform said center honeycomb laminate ( 12 );

top and bottom structural outer laminates ( 16 , 18 ) integrally bonded to corresponding opposite sides of said center honeycomb laminate ( 12 ), with each structural outer laminate ( 16 , 18 ) comprising:

an imperforate acoustic septum ( 4 ) directly bonded to a corresponding side of said center honeycomb laminate ( 12 );

an outer honeycomb ( 5 ) directly bonded to a corresponding one of said imperforate acoustic septums ( 4 ); and

a plurality of directional structural fiber layers ( 6 , 7 , 8 ) integrally bonded to corresponding ones of said outer honeycombs ( 5 ) to collectively define said top and bottom structural outer laminates ( 16 , 18 ) having outer skins ( 20 , 22 ) integral therewith.

17. The panel according to claim 16 wherein:

said adhesive layer ( 2 ) bonds said foam plugs inside each of said honeycomb cells ( 14 ); and

said imperforate acoustic septums ( 4 ) and plurality of directional structural fiber layers ( 6 , 7 , 8 ) include prepreg epoxy thermally cured to integrally bond together said preformed center honeycomb laminate ( 12 ) between said outer laminates ( 16 , 18 ) in a unitary aircraft structural panel ( 10 ).

18. The panel according to claim 17 wherein:

said foam plugs substantially fill said honeycomb cells ( 14 ) of said center honeycomb laminate ( 12 ) to provide acoustic abatement;

said outer honeycombs ( 5 ) have empty honeycomb cells; and

said outer skins ( 20 , 22 ) are imperforate.

19. The panel according to claim 17 wherein:

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

said outer honeycombs ( 5 ) include empty honeycomb cells.

20. The panel according to claim 19 wherein:

said center honeycomb ( 1 ) comprises metal;

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

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