Curved Tie Elements for Aircraft Torsion Box Fatigue
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Solution Overview
Problem
Aircraft flow body torsion boxes face high interface loads and stiffness issues at corner regions due to numerous individual connections between stiffening elements and skins, leading to over-determinate structures and increased weight.
Innovation Solution
A flow body torsion box design featuring tie elements with a curved, resilient structure that reduces interface loads by providing resilient behavior in one direction and stiff behavior in a transverse direction, using fiber-reinforced plastic materials with specific fiber orientations to manage load transfer effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If numerous individual connections are used to attach stiffening elements and skins, then structural strength is improved, but device complexity and weight increase
Solution Approach 1:
The patent merges multiple individual attachment connections into a single integrated tie element. The tie element combines multiple attachment functions (attaching to rib, attaching to skin, load transfer) into one unified component, eliminating the need for numerous separate connections while maintaining structural strength and reducing complexity
2Strength
If the structure is stiffened to resist torsion loads, then structural strength is improved, but weight increases
Solution Approach 1:
The patent changes the stiffness parameter of the tie element by introducing a curved section with reduced wall thickness. This creates a resilient behavior that allows controlled deformation under load, reducing the overall stiffness of the torsion box while maintaining sufficient strength and reducing weight
3Force
If the tie elements are made stiff to transfer loads effectively, then shear load transfer efficiency is improved, but interface loads at corners increase
Solution Approach 1:
The patent applies local quality by creating different stiffness characteristics in different sections of the tie element. The straight sections maintain high stiffness for effective shear load transfer, while the curved section introduces local flexibility to reduce interface loads at corner regions where stiffening elements meet skins
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
The design reduces local stiffness and interface loads, improves fatigue behavior, and decreases the overall weight of the torsion box while maintaining shear load transfer efficiency, making it suitable for both new and existing structures.
Implementation Method 1
the tie elements are at least partially curved so as to be resiliently deformable along a first direction along a connection line between the first attachment end and the second attachment end
Data Source
AI summary
A flow body torsion box includes a plurality of ribs, a first spar attached to a first end of the ribs, a second spar attached to a second end of the ribs, a first skin, and a second skin. The first skin and the second skin are arranged at a distance to each other to enclose the ribs and the spars. The first skin and the second skin are attached to the ribs and the spars through tie elements to form a torsion box. The tie elements comprise a first attachment end and a second attachment end between which the tie elements are at least partially curved so as to be resiliently deformable along a first direction along a connection line between the first attachment end and the second attachment end.