Variable Gage Composite Stringer Design for Aircraft Weight Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional composite stringers in aircraft have a uniform gage structure that leads to excess weight and increased manufacturing costs due to mismatched stiffness between skin flanges and support structures, resulting in potential delamination under mechanical loads.
Innovation Solution
A composite stringer design with varying gages, where the top flange has a greater gage than the skin flange and web, allowing for reduced weight and cost while maintaining load-bearing performance, and incorporating a radius filler with constant radii of curvature to simplify tooling and reduce variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform gage structure is used in conventional composite stringers, then manufacturing is simplified, but weight increases and manufacturing costs increase due to excess material
Solution Approach 1:
The patent applies local quality by varying the gage (thickness) of the stringer in different regions. The top flange has a greater gage than the skin flange and web, allowing each region to have the appropriate thickness for its structural function. This reduces weight by removing excess material from regions where it is not needed while maintaining sufficient strength where required.
2Ease of manufacture
If a uniform gage structure is used in conventional composite stringers, then manufacturing is simplified, but manufacturing costs increase due to material waste
Solution Approach 1:
The varying gage design allows material to be optimized in each region. The top flange uses greater gage material where high strength is needed, while the skin flange and web use reduced gage where less material is required, thereby reducing overall material waste and manufacturing costs.
Solution Approach 2:
The patent changes the gage parameter across different regions of the stringer. By transitioning from a uniform gage to a variable gage structure, the design achieves better material utilization, reducing waste while maintaining structural integrity.
3Stability of the object's composition
If the skin flange has high stiffness to match support structure, then structural integrity is maintained, but delamination occurs under mechanical loads due to stiffness mismatch
Solution Approach 1:
The patent changes the gage parameter of the skin flange to reduce its stiffness, allowing it to flex with the support structure during loading. This parameter change reduces the stiffness mismatch between the skin flange and support structure, thereby preventing delamination while maintaining structural integrity.
4Strength
If greater gage is used throughout the stringer, then strength is maximized, but weight increases and fuel efficiency decreases
Solution Approach 1:
The patent applies local quality by concentrating greater gage material specifically in the top flange where high load-bearing capacity is needed, while using reduced gage in the skin flange and web. This localized approach maximizes strength where required without unnecessarily increasing weight throughout the entire stringer.
Solution Approach 2:
The gage parameter is changed from uniform to variable across different regions. The top flange maintains greater gage for maximum strength, while other regions use optimized, reduced gage, achieving the best strength-to-weight ratio.
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
In an example, a composite stringer (320) is described. The composite stringer includes a skin flange (324) having a first gage (338), a top flange (326) having a second gage (340), and a web (328) having a third gage (342) and extending between the skin flange and the top flange. The skin flange is configured to be coupled to a support structure (322). The support structure includes at least one of a skin of a vehicle or a base charge. The second gage of the top flange is greater than the first gage of the skin flange and the third gage of the web. The skin flange, the top flange, and the web include a plurality of plies of composite material.