Compacted Stringer Packages Using Mandrel and Radius Fillers
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Solution Overview
Problem
Conventional composite stringer manufacturing processes are hindered by large cure tools that limit production capacity and increase manufacturing time due to the need for multiple assembly processes and the challenge of forming stringers to complex fuselage contours without introducing wrinkles, which can affect material performance.
Innovation Solution
A method involving a composite charge shaped over a forming and cure mandrel with mechanical and vacuum pressure to form compacted stringer packages with a hat-shaped cross-section, using first and second radius fillers to maintain shape and reduce the need for extensive curing and consolidation steps, allowing for efficient assembly and reduced manufacturing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a large cure tool is used to form composite stringers and skins, then the stringers can be assembled on the cure tool, but the manufacturing footprint increases and the quantity of cure tools that fit within a manufacturing environment decreases
Solution Approach 1:
The manufacturing process is segmented into two independent stages: (1) forming stringer packages separately using a compact forming tool with a mandrel, radius fillers, and vacuum pressure, and (2) assembling the pre-formed stringer packages onto the cure tool with the skin. This segmentation allows the forming operation to use a small footprint tool while the curing tool maintains its full functionality for skin curing.
Solution Approach 2:
The stringer packages are formed in advance as complete, compacted units before being assembled onto the cure tool. The preliminary forming action creates self-contained packages that include the stringer structure, radius fillers, and vacuum consolidation layers, eliminating the need for on-tool forming operations.
2Ease of manufacture
If multiple assembly processes are performed to form composite stringers, then the stringers can be assembled on the cure tool, but the overall manufacturing time increases
Solution Approach 1:
Multiple manufacturing operations are merged into a single integrated forming process. The mandrel, radius fillers, composite stringer components, and vacuum consolidation layers are all formed simultaneously in one operation, rather than being assembled through multiple sequential steps. This merging dramatically reduces manufacturing time while maintaining assembly capability.
3Shape
If composite stringers are formed to complex fuselage contours, then the stringers can match the fuselage shape, but wrinkles may be introduced that affect material performance
Solution Approach 1:
The mandrel serves as an intermediary forming surface that provides the exact fuselage contour shape. The radius fillers act as intermediaries between the mandrel and the composite stringer components, ensuring smooth transitions and proper curvature. The vacuum consolidation layers serve as intermediaries that apply uniform pressure to eliminate wrinkles while the stringer package cures, protecting material performance.
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 enables the production of compacted stringer packages that can be efficiently assembled and cured, reducing manufacturing time and storage requirements while maintaining material integrity, thus improving aircraft production capacity and reducing the risk of wrinkles.
Implementation Method 1
Mechanical pressure is applied to shape the composite charge to the forming and cure mandrel and a rigid base to form a stringer layup
Implementation Method 2
Vacuum pressure is applied to the stringer layup to form a compacted stringer package having a hat-shaped cross-section
Data Source
AI summary
An illustrative embodiment of the present disclosure provides a method. A composite charge is placed over a forming and cure mandrel, a first radius filler, and a second radius filler. Mechanical pressure is applied to shape the composite charge to the forming and cure mandrel and a rigid base to form a stringer layup having a hat-shaped cross-section. Vacuum pressure is applied to the stringer layup to form a compacted stringer package.