Composite Stringer Web Stabilization Without Metallic Fittings
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Solution Overview
Problem
Current methods for stabilizing the webs of composite stringers against lateral bending or folding, especially in non-perpendicular orientations or biased configurations, require the use of metallic fittings which increase production time, complexity, and part count, and do not address the need for stabilization without separate fittings.
Innovation Solution
A stringer configuration transitioning from a hat section to a dual-blade section with angle and ply transition zones, where the orientation of webs changes within an angle transition zone and the ply layup transitions from a biased to an unbiased configuration, eliminating the need for separate metallic fittings by altering the orientation and layup of the stringer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If metallic fittings are used to stabilize the webs against lateral bending, then the webs are stabilized, but the production time and complexity increase
Solution Approach 1:
The invention removes the cap from the stringer structure, extracting the element that was causing the need for additional stabilization fittings. By eliminating the cap, the design accepts that the webs will be unsupported at that location, but compensates through alternative means (reduced stiffness requirement at outboard section) to avoid the complexity of metallic fittings
Solution Approach 2:
Instead of adding fittings to stabilize the webs after the fact, the invention inverts the approach by designing the stringer without a cap at the outboard section. This inversion transforms the problem from one requiring additional stabilization components to one where the structural configuration itself addresses the stability concern through reduced stiffness requirements in that region
2Stability of the object's composition
If metallic fittings are used to stabilize the webs, then the webs are stabilized, but the device complexity increases
Solution Approach 1:
The invention extracts and removes the cap from the stringer structure, eliminating the need for complex metallic fitting assemblies. This simplification accepts the consequence of unsupported webs but avoids the complexity of additional stabilization components
Solution Approach 2:
The invention merges the functions of the cap and web stabilization into a single design decision: omitting the cap at the outboard section. This consolidation eliminates the need for separate stabilization fittings, reducing overall structural complexity while addressing both the cap's original functions and the web stability concern
3Productivity
If the cap is removed to reduce stiffness and provide venting, then load carrying efficiency is optimized and fuel vapor venting is enabled, but the webs become unstable
Solution Approach 1:
The invention removes the cap from the outboard section of the stringer, extracting the structural element that provided both stiffness and web stabilization. This extraction optimizes load carrying efficiency by reducing stiffness where bending loads are lower, and enables fuel vapor venting through the opening, while accepting that the webs will be unsupported in this region
Solution Approach 2:
Instead of keeping the cap intact and adding fittings to stabilize the webs, the invention inverts the approach by removing the cap entirely at the outboard section. This inversion transforms the stability problem into a design feature where the unsupported webs are acceptable given the reduced load conditions and alternative stabilization methods
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A stringer comprises a base portion (28) and first and second webs (30,32) extending outwardly from the base portion. The orientation of at least one of the first and second webs may transition from a first angle to a second angle within an angle transition zone (74).