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A composite stiffener is fabricated using preforms of laminated, unidirectional composite tape. The stiffener includes a void that is reinforced by a filler wrapped with a structural adhesive. The surfaces of the preforms surrounding the void include a layer of composite fabric which is bonded to th

A composite stiffener is fabricated using preforms of laminated, unidirectional composite tape. The stiffener includes a void that is reinforced by a filler wrapped with a structural adhesive. The surfaces of the preforms surrounding the void include a layer of composite fabric which is bonded to the filler by the adhesive, thereby increasing the toughness of stiffeners around the void and improving pull-off strength of the stiffener.

대표청구항 ▼

1. A method of fabricating a composite stiffener, comprising: forming a pair of composite channels each having a flange and a radius portion using composite fiber tape having only unidirectional reinforcing fibers, the composite fiber tape placed over a tool;placing a layer of composite fiber fabric

1. A method of fabricating a composite stiffener, comprising: forming a pair of composite channels each having a flange and a radius portion using composite fiber tape having only unidirectional reinforcing fibers, the composite fiber tape placed over a tool;placing a layer of composite fiber fabric on the radius portion of each of the channels, said composite fiber fabric comprising fibers transversely oriented with respect to one another and with respect to said unidirectional reinforcing fibers comprising said channels;forming a base using additional composite fiber tape;placing a layer of said composite fiber fabric on at least a portion of the base;placing a layer of adhesive on and around an outer surface of a filler while said outer surface is not in contact with the channels and the base, said adhesive only on said outer surface and not within said filler;assembling the channels and the base following placing said layer of adhesive;placing the filler and the layer of adhesive in a radius filler zone between the radius portions of the channels and the base; and,curing the assembly to form the composite stiffener. 2. The method of claim 1, wherein the forming of the channels and the base each includes laying up multiple plies of said composite tape. 3. The method of claim 1, wherein placing the adhesive layer around the filler is performed by wrapping the filler with a sheet of adhesive. 4. The method of claim 1, further comprising: placing a layer of said composite fiber fabric on sections of each of the channels and the base outside the radius filler zone; and,introducing a layer of adhesive between the layers of said composite fiber fabric on the sections outside the radius filler zone. 5. The method of claim 1, wherein the composite stiffener comprises a C-shaped cross-section. 6. The method of claim 1, wherein the composite stiffener comprises an I-shaped cross-section. 7. The method of claim 1, wherein the step of forming multi-play lay-ups further comprises forming a first multi-ply lay up on a first tool and forming a second multi-ply lay-up on a second tool. 8. The method of claim 7, further comprising moving the first tool and the second tool proximate to each other so as to form an I-shaped cross section. 9. The method of claim 1, wherein the multi-ply lay-ups comprise carbon fibers. 10. A method of fabricating a reinforced composite stiffener, comprising: forming a composite structure having a web and a pair of flanges extending in opposite directions from the web, including forming multi-ply lay-ups of only unidirectional fiber composite tape on a tool and placing a layer of composite fiber fabric on a radius portion between one of the flanges and one of the webs, said composite fiber fabric comprising fibers transversely oriented with respect to one another and with respect to said unidirectional reinforcing fibers comprising said channels,placing an adhesive around and on an outer surface of the filler for joining the reinforcing filler to the composite fabric layers on the composite structure and a cap, said adhesive only on said outer surface and not within said filler, said placing an adhesive following formation of said filler while said outer surface is not in contact with the web and the cap and prior to assembling said cap;placing the reinforcing filler in a radius filler zone;applying a second layer of said composite fabric on a surface of the cap; andjoining the surface of the cap to the flanges. 11. The method of claim 10, wherein: forming the composite structure includes forming the laminated tape plies into first and second channels, andapplying a layer of said composite fabric on an outer surface of the laminated composite tape plies includes placing patches of the composite fabric on selected areas of the first and second channels. 12. The method of claim 11, further comprising: placing a layer of said composite fabric on facing surfaces of the each of the first and second channels; and,joining the first and second channels together at the facing surfaces. 13. A method of fabricating a reinforced composite stiffener for aircraft applications, comprising: forming multi-ply lay-ups of unidirectional fiber composite tape on a tool;forming the lay-ups into first and second C-channels, a cap and a base;assembling the C-channels, the cap and the base into an I-section structure having a web and a pair of flanges on each end of the web;applying composite fabric on outer surfaces of the C-channels, the cap and the base in areas forming radius filler zones at the intersection of the web with the cap and with the cap and with the base, said composite fabric comprising fibers transversely oriented with respect to one another and with respect to fibers comprising said C-channels;wrapping a structural adhesive around and on an outer surface of a reinforcing filler following formation of said filler while said outer surface is not in contact with the web and the base and prior to assembling said cap and said base, said adhesive only on said outer surface and not within said filler;placing the reinforcing filler and the adhesive in the radius filler zone following assembling said cap and said base; andcuring the assembly to form the composite stiffener. 14. The method of claim 13, wherein the step of forming multi-play lay-ups further comprises forming a first multi-ply lay up on a first tool and forming a second multi-ply lay-up on a second tool. 15. The method of claim 14, further comprising moving the first tool and the second tool proximate to each other so as to form an I-shaped cross section.