# US 10,479,475 B2 · Composite stringer beam joint structure of an aircraft

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- Number: US 10,479,475 B2
- Document ID: US10479475B2
- Status: Granted
- Kind: B2
- Application number: 13/962,974
- Filed: 2013-08-09
- Published: 2015-02-12
- Granted: 2019-11-19
- Earliest claimed: 2013-08-09
- Assignees: The Boeing Company
- Applicants: The Boeing Company
- Inventors: Zeaid Fouad Hasan; Jeffrey F. Stulc; Phillip Roger Pratt; James A. Backlund, Jr.; Nickolas Scott Ellerbeck; Lyle Ray Deobald
- Web page: https://patentgrep.com/patent/US10479475B2

## CPC

- B64C 1/064: {Stringers; Longerons}
- B64C 1/061: {Frames}
- B64C 1/26: Attaching the wing or tail units or stabilising surfaces
- B64C 3/182: {Stringers, longerons}
- B64C 1/10: Bulkheads
- B64C 2001/0072: {from composite materials}
- Y10T 29/49622: Vehicular structural member making
- Y10T 156/1062: Prior to assembly
- B64C: AEROPLANES; HELICOPTERS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A stringer beam joint structure of an aircraft formed from fiber-reinforced composites includes a wing and a wing box. The wing is joined to the wing box at a side of a joint structure. The wing and the wing box each includes a lower skin. A plurality of stringers is coupled to the lower skin and all made of fiber-reinforced composites. A first end of at least one of the plurality of stringers at the side of the joint structure features a web cutout with a taper formed in the base flange that spans longitudinal to the respective stringer and the taper located at the end of each respective stringer, where the taper runs from a knife edge of a base flange of the respective stringer to a full height of the base flange. The tapered surface of the base flange is contiguous with an edge of the web cutout.

## Claims

### Claim 1

A stringer beam joint structure of an aircraft formed from fiber-reinforced composites comprising:
a wing and a wing box, the wing joined to the wing box at a side of a joint structure, the wing and the wing box each including a lower skin; and
a plurality of stringers coupled to the lower skin and all made of fiber-reinforced composites,
wherein:
each stringer has a first end and a second end, where the first and second ends extend in a spanwise direction, and each stringer comprises a cap flange, a base flange, and a web between the cap flange and the base flange;
the cap flange, the base flange, and the web are elongate in each respective stringer's spanwise direction;
the first end of at least one of the plurality of stringers at the side of the joint structure features a web cutout with a taper, formed in the base flange along the respective stringer, the taper located at the first end of each respective stringer, where the taper runs from a knife edge distal end of the base flange to a proximal end that coincides with a full height of the base flange, the taper oriented at an angle between 10 and 15 degrees;
the taper of the base flange is contiguous with an edge of the web cutout;
the base flange comprises an overwrap layer on the taper of the base flange;
the overwrap layer is made of sheet metal or plies of reinforcing fibers that are pre-impregnated with resin; and
the overwrap layer is bonded to the taper of the base flange and configured to constrain an end of the base flange from peeling off a mated skin.

### Claim 2 (depends on 1)

The aircraft of claim 1, further comprising a splice chord, wherein the base flange is joined to the lower skin; and wherein the cap flange is joined to the splice chord.

### Claim 3 (depends on 1)

The aircraft of claim 1, wherein the cutout has a parabolic shape.

### Claim 4 (depends on 1)

The aircraft of claim 1, wherein the overwrap layer includes fiber-reinforced composite.

### Claim 5 (depends on 1)

The aircraft of claim 1, wherein a number of corners of the base flange are rounded.

### Claim 6 (depends on 1)

The aircraft of claim 1, wherein a subset of the plurality of stringers include back-to-back beams and a number of noodles between a number of bases of the back-to-back beams, wherein the noodles are tapered to match the taper of the respective base flange.

### Claim 7

An aircraft wing assembly comprising:
a central wing box including a lower skin and a number of stringers coupled to the lower skin of the central wing box, the stringers are all made from fiber-reinforced composites;
a first wing and a second wing, where the first and second wings each includes a lower skin and a number of stringers coupled to the lower skin of each of the wings, the stringers of the first wing and the second wing all made from fiber-reinforced composites; and
a number of splice chords for joining the first and second wings to opposite sides of the central wing box;
wherein:
each of the stringers has a first end and a second end, where the first and second ends extend in a spanwise direction, and each stringer comprises a cap flange, a base flange, and a web between the cap flange and the base flange;
the cap flange, the base flange, and the web are elongate in each respective stringer's spanwise direction;
the first end of at least one of the stringers from each of central wing box, the first wing, and the second wing comprises a web cutout with a taper, formed in the base flange along the respective stringer, the taper located at the first end of each respective stringer, where the taper runs from a knife edge distal end of the base flange to a proximal end that coincides with a full height of the base flange, the taper oriented at an angle between 10 and 15 degrees;
the taper of the base flange is contiguous with an edge of the web cutout;
the base flange comprises an overwrap layer on the taper of the base flange;
the overwrap layer is made of sheet metal or plies of reinforcing fibers that are pre-impregnated with resin; and
the overwrap layer is bonded to the taper of the base flange and configured to contrain an end of the base flange from peeling off a mated skin.

### Claim 8 (depends on 7)

The aircraft wing assembly of claim 7, wherein the cap flanges of the stringers of the first and second wings are joined to the splice chords.