Continuously Curved Spar for Aircraft Wing Structural Integrity
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Solution Overview
Problem
Existing structural spars in aircraft wings with discrete kinks require complex assembly, increase manufacturing costs, weight, and fuel consumption due to the need for additional fasteners and increased material strength to manage kick loads, while also posing a risk of lightning strikes.
Innovation Solution
The use of continuously curved spars with a unitary configuration and no discrete kinks, which are manufactured as composite structures and integrated into the aircraft design to form structural walls within fuel containment regions, reducing the need for additional fasteners and distributing loads more evenly across ribs and panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If discrete kinks are used in structural spars, then the spar can achieve the required structural configuration, but the manufacturing complexity and cost increase due to multiple parts and splices
Solution Approach 1:
The patent merges multiple discrete spar segments into a single continuously curved spar structure. This eliminates the need for multiple splices and joints, thereby reducing manufacturing complexity while maintaining the required swept-back configuration. The continuous curvature is achieved through careful design of the mold or tooling used to form the spar.
Solution Approach 2:
The patent employs continuous curvature in the spar design, replacing the traditional straight segments with abrupt joints with smoothly curved segments. This continuous curvature not only improves the aerodynamic appearance but also eliminates the need for discrete kinks, thereby simplifying manufacturing while achieving the desired swept-back shape.
2Ease of manufacture
If multiple fasteners and fixtures are used to join spar parts, then the discrete kinked spars can be assembled, but the aircraft weight increases
Solution Approach 1:
By combining multiple discrete spar parts into a single continuously curved spar, the patent eliminates the need for numerous fasteners and fixtures that would be required to join the parts. This weight reduction is achieved while maintaining assembly capability through the integrated monolithic structure.
3Strength
If additional strength capability is added to wing skins and ribs to resolve kick loads from kinks, then structural integrity is improved, but weight and cost increase
Solution Approach 1:
The continuous curvature of the spar eliminates abrupt angle changes, thereby eliminating the generation of kick loads. This allows the wing skins and ribs to be designed with standard thickness and material properties, avoiding the need for additional strength capability that would increase weight and cost.
4Ease of manufacture
If metal fasteners are exposed through outer composite wing skin panels, then discrete spars can be joined, but the risk of lightning strike increases
Solution Approach 1:
By merging multiple discrete spar parts into a single continuously curved spar, the patent eliminates the need for exposed metal fasteners that would be required to join the parts. This reduces the risk of lightning strikes while maintaining assembly capability through the integrated structure.
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
There is provided in an embodiment an airfoil (14). The airfoil (14) has one or more fuel containment regions (28) disposed in the airfoil (14) and one or more continuously curved spars (26) extending from a root end (23) of the airfoil (14) toward a tip end (22) of the airfoil (14). At least one continuously curved spar (26) has a unitary configuration, has one or more continuous curves along the continuously curved spar (26), and either has a portion forming a structural wall (84) of at least one of the one or more fuel containment regions (28), or, is internal to the one or more fuel containment regions (28).