Design of Curved Fiber Paths for Composite Laminates

• US 20120323538A1
• Filed: 06/20/2011
• Published: 12/20/2012
• Est. Priority Date: 06/20/2011
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Rassaian, Mostafa, Grandine, Thomas A., Grimshaw, Matthew Todd, Patterson, Matthew Steven
• Granted Patent: US 8,756,037 B2
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: G06F 2113/26 Composites
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]
• CPC Class Codes: G06F 30/15 Vehicle, aircraft or watercraft design
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]

Abstract

A computational optimization process uses the variable stiffness performance of composite laminates attributed to steered fiber to guide the design of stream functions describing the fibers to build it. This design process combines a finite element-based analysis tool, failure criteria and geometry optimization to determine steered angles associated with stream functions by an optimization program to meet target performance requirements, e.g., load condition(s), and failure criteria for quasi-static or dynamic events. The fiber angle distribution and thickness buildup are computed based on the stream function. The simulated structure is analyzed using finite element analysis. The disclosed process allows the designer to impose manufacturing constraints such as fiber steering radius.

Claims

1. A method for designing a composite laminate, comprising:

(a) selecting design variable values for a design of a first ply;

(b) computing a stream function for the first ply in accordance with the selected design variable values;

(c) computing a balancing ply stream function for a second ply that balances or nearly balances the first ply;

(d) computing a respective fiber angle distribution of each of the first and second plies based on the respective stream functions for the first and second plies;

(e) computing a thickness buildup of the first ply based on the stream function for the first ply;

(f) analyzing the simulated structure of a laminate comprising the first and second plies simulated by the results of the foregoing computing steps and additional plies;

(g) computing one or more measures of merit for the simulated structure; and

(h) iterating steps (a) through (g) until an optimum value of one or more of the measures of merit is obtained

2. The method as recited in claim 1, wherein step (a) comprises selecting design variable values that specify courses having steered fibers of radius greater than a lower limit.

3. The method as recited in claim 1, wherein step (a) comprises selecting design variable values that specify courses having thickness buildup due to course overlap less than an upper limit.

4. The method as recited in claim 1, wherein step (f) comprises performing a finite element analysis.

5. The method as recited in claim 1, wherein step (f) comprises solving for the strain field for the simulated structure under unit load and processing that strain field to calculate laminate strength based on unit-load results.

6. The method as recited in claim 1, wherein steps (b) through (g) are performed by each of a plurality of processors operating in parallel.

7. The method as recited in claim 1, wherein each of the first and second plies is designed to have a respective cutout.

8. The method as recited in claim 1, further comprising programming a controller of a computer numerical control tow placement machine with instructions that will cause the tow placement machine to lay tows of a ply along paths defined by the stream function for the first ply which resulted in the optimum value of one or more of the measures of merit being obtained.

9. The method as recited in claim 1, further comprising storing on a computer-readable medium data representing a manufacturing plan for a particular ply, said manufacturing plan comprising the stream function for the first ply which resulted in the optimum value of one or more of the measures of merit being obtained.

10. A method for producing a composite laminate, comprising:

(a) selecting design variable values for a design of a ply;

(b) computing a stream function for the ply in accordance with the selected design variable values;

(c) computing a fiber angle distribution of the ply based on the stream function for the ply;

(d) computing a thickness buildup of the ply based on the stream function for the ply;

(e) analyzing a simulated structure of a laminate comprising the ply simulated by the results of the foregoing computing steps and additional plies;

(f) computing one or more measures of merit for the simulated structure;

(g) iterating steps (a) through (f) until an optimum value of one or more of the measures of merit is obtained;

(h) determining a computer program for controlling a machine to lay courses along paths defined by the stream function which resulted in the optimum value of one or more of the measures of merit being obtained; and

(i) automatically laying courses on a composite laminate in process in accordance with said computer program.

11. The method as recited in claim 10, wherein step (a) comprises selecting design variable values that specify courses having steered fibers of radius greater than a lower limit.

12. The method as recited in claim 10, wherein step (a) comprises selecting design variable values that specify courses having thickness buildup due to course overlap less than an upper limit.

13. The method as recited in claim 10, wherein step (e) comprises performing a finite element analysis.

14. The method as recited in claim 10, wherein step (e) comprises solving for the strain field for the simulated structure under unit load and processing that strain field to calculate laminate strength based on unit-load results.

15. The method as recited in claim 10, wherein steps (b) through (f) are performed by each of a plurality of processors operating in parallel.

16. The method as recited in claim 10, wherein the ply is designed to have a cutout.

17. The method as recited in claim 10, further comprising programming a controller of a computer numerical control tow placement machine with instructions that will cause the tow placement machine to lay courses along paths defined by the stream function which resulted in the optimum value of one or more of the measures of merit being obtained.

18. The method as recited in claim 10, further comprising storing on a computer-readable medium data representing a manufacturing plan for a particular ply, said manufacturing plan comprising the stream function for the ply which resulted in the optimum value of one or more of the measures of merit being obtained.

19. A system for designing a composite laminate having at least one steered-fiber ply, comprising a processor programmed to execute the following operations:

(a) selecting design variable values for a design of a steered-fiber ply;

(b) computing a stream function for the ply in accordance with the selected design variable values;

(c) computing a fiber angle distribution of the ply based on the stream function for the ply;

(d) computing a thickness buildup of the ply based on the stream function for the ply;

(e) analyzing a simulated structure of a laminate comprising the ply simulated by the results of the foregoing computing steps and additional plies;

(f) computing one or more measures of merit for the simulated structure; and

(g) iterating steps (a) through (f) until an optimum value of one or more of the measures of merit is obtained.

20. The system as recited in claim 19, wherein each stream function comprises a multiplicity of contour lines representing respective course paths of a respective steered-fiber ply design.