Composite Structural Element for Aircraft Torsion Box
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Solution Overview
Problem
Conventional composite structural elements for aircraft torsion boxes, such as ribs and spars, face challenges in achieving high stability and stiffness while maintaining a low overall weight, particularly due to inadequate resistance to shear forces, leading to higher fuel costs and weight issues.
Innovation Solution
A composite structural element with a specific lay-up of fiber-reinforced composite materials, featuring a pair of plies oriented at angles between -17° to -23° and +37° to +43°, combined with stiffeners extending at +90°, which enhances buckling resistance equally for direct and opposite shear forces, reducing the need for additional plies or thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional lay-ups with +/- 45° or +/- 60° fiber orientation are used, then the structural element achieves basic stability, but the weight increases undesirably high
Solution Approach 1:
The patent changes the fiber orientation angles from conventional values (+/- 45° or +/- 60°) to optimized values (+/- 20° to +/- 40°). This parameter change in the lay-up configuration provides enhanced buckling resistance against shear forces while reducing the overall weight of the structural element, directly resolving the contradiction between stability and weight.
Solution Approach 2:
The patent employs fiber-reinforced composite materials with specifically optimized fiber orientations arranged in plies. By using composite materials with tailored fiber angles (+/- 20° to +/- 40°), the structure achieves superior buckling resistance per unit weight compared to conventional materials, addressing both the stability and weight concerns simultaneously.
2Strength
If additional plies or increased thickness are added to improve shear force resistance, then the buckling resistance improves, but the weight and fuel costs increase
Solution Approach 1:
Instead of increasing the number of plies or thickness, the patent changes the fiber orientation parameters to +/- 20° to +/- 40°. This optimized angular configuration provides superior shear force resistance and buckling resistance with fewer plies, thereby reducing weight and avoiding increased fuel costs.
Solution Approach 2:
The patent applies local quality optimization by specifically tailoring the fiber orientation angles in different plies to match the local stress distribution patterns. The +/- 20° to +/- 40° orientation is specifically optimized for resisting shear forces and preventing buckling in the web section, providing efficient local reinforcement without adding overall weight.
Data Source
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AI summary
The invention relates to a composite structural element (12, 14), in particular a rib (12) or a spar (14), specifically for use in a torsion box (10) of an aircraft structure such as a vertical tailplane, wherein the structural element (12, 14) defines a coordinate system with a first axis (a) wherein the structural element (12, 14) comprises a substantially planar main section (22) defining a coordinate system with a first axis (a) extending along the longitudinal axis (L) of the structural element (12, 14) and a second axis (b) extending perpendicular to said longitudinal axis (L) within the planar main section and defining an angle of +90° with the first axis (a), , wherein the structural element (12, 14) contains a lay-up (28) of single plies (30, 34) consisting of a fiber-reinforced composite material with a substantially unidirectional fiber orientation (32), and wherein the lay-up (28) comprises at least one symmetrically arranged pair of a first and a second ply (30, 34) which are arranged in said lay-up (28) such that the direction of fiber orientation (32) extends in said coordinate system at an angle (α, β) in the range of -17° to -23° for the first ply (30) and +37° to +43° for the second ply (34).