Composite Stringer Forming with Pinch Bladder Control
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Solution Overview
Problem
The existing methods for fabricating composite parts, such as aircraft fuselage stringers, require separate tools for layup and curing, leading to increased production time, material and labor costs, and potential shape changes or misalignment due to tool shifting during the forming process.
Innovation Solution
A method and apparatus for forming composite parts directly on a cure tool, eliminating the need for layup and forming tools, by using pinch bladders to control the centerline position of the composite charge during the forming process, allowing one side to slip while holding the other side in place to prevent movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate tools are used for layup and curing of composite parts, then the curing process can be performed independently, but production flow time increases and tolerance location buildup occurs
Solution Approach 1:
The patent combines the layup tool and cure tool into a single integrated tool that performs both functions. The composite charge is laid up directly on the cure tool surface, eliminating the need for separate layup and cure tools. This merging of functions reduces production flow time while maintaining curing process independence through the integrated design.
2Adaptability or versatility
If separate tools are used for layup and curing, then each process can be optimized independently, but material and labor costs increase
Solution Approach 1:
The integrated tool combines layup and curing functions into a single device, reducing the total number of tools required. This reduces material costs for tooling and labor costs for operating multiple separate tools, while the modular bladder design allows for process optimization flexibility.
3Manufacturing precision
If the composite charge is compressed between male and female tool dies during forming, then the charge is formed to final shape, but the charge may shift out of position causing tolerance violations
Solution Approach 1:
The patent incorporates alignment features directly into the cure tool surface before the composite charge is placed. These pre-formed alignment features guide the charge into the correct position and maintain it during forming, preventing shifts that would cause tolerance violations while ensuring accurate final shape.
4Ease of manufacture
If the composite charge is transported between layup and cure tools, then separate processing steps can be performed, but the part may change shape or wrinkle due to relaxation
Solution Approach 1:
The patent eliminates transportation between separate layup and cure tools by integrating both functions into a single tool. The composite charge remains on the cure tool surface throughout the entire process, preventing shape changes and wrinkling that occur during transport and dwell times at pre-installation stages.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces tolerance buildup, wrinkling, and dimensional changes, ensuring accurate part formation without the need for separate tools and minimizing the risk of misalignment.
Implementation Method 1
forming the composite charge into the mold cavity is performed by forcing a bladder into the mold cavity, and expanding the bladder as the bladder is being forced into the mold cavity
Implementation Method 2
holding one of the opposite sides of the composite charge against movement on the tool during forming of the composite charge into the mold cavity
Data Source
AI summary
A composite part, such as a stiffener is formed in place. A composite charge is placed on a tool spanning a mold cavity, with the centerline of the charge offset from the centerline of the mold cavity. Opposite sides of the charge are held against the tool as the charge is formed into the mold cavity. One side of the charge is held against movement on the tool while the other side of the charge is allowed to slip over the tool toward the mold cavity.