Composite Panel Step Design for Load Transmission
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Solution Overview
Problem
Existing composite aircraft skin structures face challenges in achieving significant variations in panel thickness, particularly around engine or pylon mounts, due to limitations in ramp gradients and parallel inner and outer mould line surfaces, which restrict load transmission and stiffening efficiency.
Innovation Solution
A composite structure with a panel featuring a step in thickness, where stiffeners are attached on both sides of the step, engaging either the edges of discontinued plies or a filler, allowing for efficient load transmission and reduced strain concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shallow ramp gradient is used to avoid load eccentricities, then the structure maintains load transmission stability, but the panel thickness variation is limited and cannot achieve significant thickening in required regions
Solution Approach 1:
The panel is segmented into multiple plies with different continuation patterns. Some plies are discontinued at the step location while others continue, allowing the panel to achieve abrupt thickness changes without requiring shallow ramps. This segmentation enables localized thickening while maintaining overall structural integrity and load transmission stability.
Solution Approach 2:
The patent applies local quality by allowing different plies to have different continuity characteristics at the step location. Specifically, certain plies are discontinued while others continue, creating a localized thickness variation that adapts to specific structural requirements (such as engine or pylon mount areas) without compromising the overall panel's load transmission capability.
2Ease of manufacture
If the inner mould line surface is kept parallel to the outer mould line surface under stringer feet for easier assembly, then the assembly process is simplified, but the ability to achieve significant panel thickness variation is restricted
Solution Approach 1:
The panel plies are segmented with selective discontinuation at the step location. This allows the creation of abrupt thickness changes while maintaining parallel IML and OML surfaces under the stringer feet, thus achieving both thickness variation and ease of assembly.
Solution Approach 2:
The patent introduces thickness variation in the vertical dimension through selective ply discontinuation, while maintaining the parallel relationship between IML and OML surfaces in the horizontal plane. This dimensional approach allows thickness adaptation without compromising assembly ease.
3Ease of manufacture
If conventional fasteners are used with shallow ramps, then the manufacturing process is straightforward, but significant panel thickness variation cannot be achieved
Solution Approach 1:
By segmenting the plies and allowing selective discontinuation at the step, the patent enables abrupt thickness changes that can accommodate conventional fasteners while achieving significant panel thickening in required regions, thus maintaining manufacturing simplicity with enhanced adaptability.
Data Source
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AI summary
A composite structure comprising: a panel formed from two or more plies of composite material, the panel having a surface formed with a step where the thickness of the panel changes. Two or more stiffeners are attached to the surface of th e panel. One of the stiffeners engages at least part of the step so as to transmit load forces in the panel.