Flyaway Stringer End Caps for Composite Wing Skin
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Solution Overview
Problem
The fabrication of composite stringers for aircraft often results in edge conditions that are out of tolerance, requiring rework, and poses challenges in laying up and curing due to complex geometries, necessitating a method to improve ramp rates and stringer run-out quality.
Innovation Solution
The use of rigid end caps affixed to stringer preforms during co-curing, which eliminate the need for shaping preforms to specific ramp rates and cutting stringers post-curing, while providing load-bearing support and enforcing desired shapes during curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If stringers are fabricated by laying up and curing preforms to terminate within the wing skin, then the stringers can be cut to desired dimensions after curing, but the edge conditions are out of tolerance and rework is required
Solution Approach 1:
Ramps are integrated into the preform during the laying up process before curing, rather than being added afterward. This preliminary action ensures the stringer has the correct geometry from the start, eliminating edge condition tolerance issues and avoiding rework while maintaining ease of manufacture through a streamlined process
Solution Approach 2:
The ramp feature is merged with the stringer preform as an integral part, rather than being a separate component. This combining of the ramp and stringer into a single preform structure simplifies manufacturing by eliminating separate fabrication and assembly steps, while ensuring precise edge conditions through unified molding
2Manufacturing precision
If preforms are shaped to specified ramp rates, then the stringer run-out quality is improved, but the laying up and curing process becomes difficult due to complex geometries
Solution Approach 1:
The ramp and stringer are merged into a single integrated preform structure that is molded as one piece. This integration eliminates the need for complex separate shaping operations, reducing device complexity while maintaining high stringer run-out quality through precise molding capabilities
Solution Approach 2:
The manufacturing approach changes from mechanical shaping of complex geometries to molded fabrication with integrated ramps. This parameter change in the manufacturing process allows achieving specified ramp rates and high run-out quality without the difficulty of laying up and curing complex geometric preforms
3Length of moving object
If stringers are cut after curing, then the desired dimensions are achieved, but post-curing trimming is required which increases time and cost
Solution Approach 1:
The stringer is molded to its final desired dimensions and shape during the curing process itself, rather than requiring post-curing cutting operations. This preliminary action achieves the correct length and geometry before the material hardens, eliminating time-consuming post-processing while maintaining precise dimensional control
Solution Approach 2:
The need for post-curing cutting operations is extracted and eliminated from the manufacturing process. By molding the stringer to its final dimensions during curing, the separate trimming step is removed entirely, reducing time loss and simplifying the overall process
Data Source
AI summary
Systems and methods are provided for fabricating composite parts. One embodiment is a method for fabricating a composite part. The method includes forming a skin panel preform comprising fiber reinforced material, disposing rigid end caps at the skin panel preform at end locations of stringer preforms that will be placed at the skin panel, locating the stringer preforms at the skin panel preform via the rigid end caps, and anchoring the stringer preforms to the skin panel preform.