Fuselage Panel Join Using Dual Rings for Fatigue Resistance
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Solution Overview
Problem
Aircraft fuselage assemblies face challenges in transmitting high forces between panels, leading to reduced reserve factors and increased risk of fatigue cracks, especially at circumferential joins, due to the limitations of existing reinforcing ring designs which fail to adequately handle increased loads and aerodynamic stresses.
Innovation Solution
The introduction of an outer ring, positioned on the outer face of the fuselage, partially overlapping the panels and fixed to both the inner ring and panels, which works in conjunction with the inner ring to distribute forces in a double shearing manner, reducing bending moments and enhancing the reserve factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the thickness of the ring is increased to increase the ability of the join to transmit forces, then the force transmission capacity is improved, but the reserve factor does not significantly improve and secondary bending moments increase
Solution Approach 1:
The single ring structure is segmented into two separate rings: an inner ring and an outer ring. The inner ring is positioned inside the fuselage and the outer ring is positioned outside the fuselage, with both rings working together to transmit forces. This segmentation allows each ring to be optimized independently and distributes the load more effectively, improving the reserve factor while maintaining force transmission capacity.
Solution Approach 2:
The solution transitions from a single-plane ring structure to a two-dimensional configuration with rings positioned on both the inner and outer faces of the fuselage. This dimensional change creates a multi-layered force transmission system that reduces bending moments and improves the reserve factor by distributing loads more effectively across multiple planes.
2Strength
If the thickness of the ring is increased to transmit higher loads, then the static strength is improved, but the secondary bending moment increases rapidly
Solution Approach 1:
The single ring is divided into inner and outer rings that are spaced apart, creating a distributed force transmission system. This segmentation reduces the secondary bending moment by distributing the load across multiple rings rather than concentrating it in a single thick ring, while maintaining the required static strength.
Solution Approach 2:
The inner and outer rings are positioned at specific locations (inner and outer faces of the fuselage) where they can most effectively resist bending moments. This localized placement optimizes the structure by concentrating reinforcement where it is most needed, reducing secondary bending moments while maintaining strength.
3Device complexity
If a single inner ring is used to assemble panels at a circumferential join, then the structure is simple, but the reserve factor reduces under increased loads
Solution Approach 1:
The single inner ring is segmented into an inner ring and an outer ring, creating a dual-ring system. While this increases structural complexity slightly, it significantly improves the reserve factor by distributing forces more effectively. The segmented design allows each ring to be optimized for its specific function while working together to enhance overall reliability.
4Shape
If panels are assembled end-to-end at a circumferential join, then aerodynamic continuity is maintained, but force transmission capability is reduced
Solution Approach 1:
The force transmission function is segmented between the inner ring and outer ring, allowing the panels to be assembled end-to-end for aerodynamic continuity while the dual-ring system provides the necessary force transmission capability. The segmentation of the reinforcement system compensates for the reduced force transmission inherent in end-to-end assembly.
Data Source
AI summary
An aircraft fuselage including at least two sections kept assembled at a circumferential join, each section having at least one panel. The circumferential join includes at least one inner ring, situated on one face, called the inner face, of the fuselage. The inner ring has a width li, partially overlaps each of the two panels and is fixed to the two panels by fasteners. The fuselage also includes an outer ring, situated on one face, called the outer face, of the fuselage, opposite to the inner face. The outer ring has a width le, partially overlaps the two panels, and is fixed to the two panels and to the inner ring by some or all of the fasteners fixing the inner ring to the two panels.