Method for minimizing fiber distortion during fabrication of one-piece composite barrel section

• US 20100024964A1
• Filed: 12/14/2006
• Published: 02/04/2010
• Est. Priority Date: 12/14/2006
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Ingram, William H. JR., Biornstad, Robert, Dull, Kenneth M.
• Granted Patent: US 8,691,037 B2
• Time in Patent Office: Days
• US Class Current: 156/189
• CPC Class Codes: B29C 53/587 having a non-uniform wall-structure, e.g. with inserts, perforations, locally concentrated reinforcements
• CPC Class Codes: B29C 53/66 with axially movable winding feed member , e.g. lathe type winding
• CPC Class Codes: B29C 70/32 on a rotating mould, former or core
• CPC Class Codes: B29C 70/382 Automated fiber placement [AFP]
• CPC Class Codes: B29C 70/44 using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding
• CPC Class Codes: B29K 2063/00 Use of EP, i.e. epoxy resins or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2077/10 Aromatic polyamides [polyaramides] or derivatives thereof
• CPC Class Codes: B29K 2079/08 PI, i.e. polyimides or derivatives thereof
• CPC Class Codes: B29K 2105/243 Partially cured
• CPC Class Codes: B29K 2105/246 Uncured, e.g. green
• CPC Class Codes: B29K 2707/04 Carbon
• CPC Class Codes: B29L 2031/3082 Fuselages

Abstract

A method for fabricating a one-piece composite fuselage section that minimizes out-of-plane fiber distortion. This is accomplished by fabricating a mandrel having a coefficient of thermal expansion in the hoopwise direction that is sufficiently greater than that of the laid-up composite ply assembly. As a result of this differential in the coefficients of thermal expansion in the hoopwise direction, the laid-up composite ply assembly is stretched circumferentially as the mandrel expands radially during cure, thereby eliminating or reducing out-of-plane fiber distortion. At the same time, the mandrel and part being fabricated should have substantially the same coefficient of thermal expansion in the lengthwise direction. As the outer surface of the mandrel increases in circumference, the circumferentially oriented reinforcing fibers of the inner plies are stretched, while the circumferentially oriented reinforcing fibers of the outer plies do not reduce in circumference and thus do not form waves or wrinkles.

Claims

1. A method for fabricating a one-piece composite barrel section, comprising the following steps:

(a) laying a composite ply assembly around a mandrel having a coefficient of thermal expansion in a hoopwise direction that is greater than the coefficient of thermal expansion of the composite ply assembly in the hoopwise direction; and

(b) raising the temperature and pressure within a volume surrounding the composite ply assembly, the temperature increase being sufficient to cause the circumference of the mandrel to expand and stretch one or more plies of the composite ply assembly,

said mandrel and said composite ply assembly having a not insubstantial difference in coefficients of thermal expansion in a hoopwise direction and an insubstantial difference in coefficients of thermal expansion in a lengthwise direction, the coefficient of thermal expansion of said mandrel in said hoopwise direction being greater than the coefficient of thermal expansion of said composite ply assembly in said hoopwise direction such that said composite ply assembly is stretched during step (b).

2. The method as recited in claim 1, further comprising the steps of:

lowering the temperature and pressure within the volume; and

separating the mandrel from the composite ply assembly after the latter has cooled.

3. The method as recited in claim 1, wherein during and after expansion, the circumference of one or more outermost plies of the composite ply assembly does not decrease by an amount sufficient to cause significant waviness or wrinkling in the composite ply assembly.

4. The method as recited in claim 1, wherein during expansion, the mandrel and the composite ply assembly expand in a lengthwise direction by substantially the same amount.

5. The method as recited in claim 1, wherein the mandrel has a plurality of grooves on its outer circumferential surface, and layup comprises the following steps:

(i) placing a portion of a respective hat stringer in a respective one of said plurality of grooves, each hat stringer being made of multiple plies of composite material;

(ii) placing a respective bladder in said portion of said respective hat stringer after step (i) has been performed; and

(iii) laying multiple plies of composite material around the outer circumferential surface of the mandrel and the bladders.

6. The method as recited in claim 5, wherein the grooves in the mandrel extend in generally lengthwise directions.

7. The method as recited in claim 1, wherein each ply of the composite ply assembly comprises reinforcing fibers or fabric and polymeric material.

8. The method as recited in claim 1, wherein an outer circumferential portion of the mandrel comprises reinforcing fabric and polymeric material.

9. The method as recited in claim 1, further comprising the following steps, performed after step (a) and before step (b):

surrounding the composite ply assembly with a sealed air-impermeable sheet to form an evacuable space; and

evacuating the evacuable space.

10. A method for fabricating a one-piece composite barrel section, comprising the following steps:

(a) laying a plurality of plies of a composite material around a mandrel to form a composite ply assembly, each ply comprising reinforcing fibers and polymeric material, the mandrel having a coefficient of thermal expansion in a hoopwise direction that is greater than the coefficient of thermal expansion of the composite ply assembly in the hoopwise direction and having a coefficient of thermal expansion in a lengthwise direction that is substantially the same as the coefficient of thermal expansion of the composite ply assembly in the lengthwise direction; and

(b) raising the temperature and pressure within a volume surrounding the composite ply assembly, the temperature increase being sufficient to cause the circumference of the mandrel to expand, which in turn causes the length of reinforcing fibers in one or more plies of the composite ply assembly to increase due to the difference in the coefficients of thermal expansion of said mandrel and said composite ply assembly in the hoopwise direction.

11. The method as recited in claim 10, further comprising the steps of:

lowering the temperature and pressure within the volume; and

separating the mandrel from the composite ply assembly after the latter has cooled.

12. The method as recited in claim 10, wherein during and after expansion, the length of reinforcing fibers in one or more outermost plies of the composite ply assembly does not decrease by an amount sufficient to cause significant waviness or wrinkling in the composite ply assembly.

13. The method as recited in claim 10, wherein during expansion, the mandrel and the composite ply assembly expand in a lengthwise direction by substantially the same amount.

14. The method as recited in claim 10, wherein the mandrel has a plurality of grooves on its outer circumferential surface, and layup comprises the following steps:

(i) placing a portion of a respective hat stringer in a respective one of said plurality of grooves, each hat stringer being made of multiple plies of composite material;

(ii) placing a respective bladder in said portion of said respective hat stringer after step (i) has been performed; and

(iii) laying multiple plies of composite material around the outer circumferential surface of the mandrel and the bladders.

15. The method as recited in claim 14, wherein the grooves in the mandrel extend in generally lengthwise directions.

16. The method as recited in claim 10, wherein an outer circumferential portion of the mandrel comprises reinforcing fabric and polymeric material.

17-27. -27. (canceled)