Laminate Composite Wing Stringer with Trapezoidal Cross Section
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Solution Overview
Problem
Aircraft wing structures face challenges in reacting to various loads due to the complexity of rib-to-panel interfaces and the tall, 'I' or 'T' shaped carbon fiber stiffeners, which increase the wing's exterior profile and reduce internal clearance, making maintenance difficult and limiting the wing's thinness, especially near the tip.
Innovation Solution
The use of laminate composite stringers with a solid trapezoidal cross-section, which are curved and have a reduced height, allowing for a continuous rib-to-panel interface with fasteners and simplified rib interfaces, enabling a thinner wing with improved aerodynamic performance and reduced disbond issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional 'I' shaped or 'T' shaped carbon fiber stiffeners are used, then the wing structure can react to bending loads, but the exterior vertical profile increases and internal clearance decreases
Solution Approach 1:
The patent changes the geometric parameters of the stiffener cross-section from traditional 'I' or 'T' shapes to a curved blade shape with optimized thickness distribution. The blade thickness varies along its length, being thickest at the root and tapering toward the tip, which reduces the overall height while maintaining bending load resistance through strategic material placement in the high-stress regions.
Solution Approach 2:
The patent utilizes carbon fiber composite materials with specific fiber orientations arranged in plies within the curved blade stiffener. The composite structure is designed to provide high strength-to-weight ratio and optimized stiffness characteristics, allowing the stiffener to resist bending loads with reduced dimensions compared to traditional metal or simpler composite sections.
2Strength
If traditional 'I' shaped or 'T' shaped carbon fiber stiffeners are used, then the wing structure can react to bending loads, but maintenance difficulty increases due to reduced internal clearance
Solution Approach 1:
By reducing the height of the stiffener cross-section through the curved blade design, the patent increases the internal clearance within the wing box structure. This improved clearance provides adequate space for maintenance personnel to access, inspect, and repair the stiffeners and surrounding structures, directly addressing the accessibility issue while maintaining structural integrity.
3Ease of manufacture
If traditional carbon fiber stiffeners with individual charges are used, then the wing structure can be constructed, but rib-to-panel interface complexity increases
Solution Approach 1:
The patent merges the traditional multi-component stiffener construction (consisting of separate charges, webs, and flanges) into a monolithic curved blade shape. This integrated design eliminates the need for complex rib-to-panel interfaces with individual feet straddling multiple charges, as the continuous curved blade provides a simplified, unified attachment surface for ribs, significantly reducing interface complexity while maintaining constructibility.
4Adaptability or versatility
If traditional bladed stringers are curved, then design flexibility increases, but susceptibility to rollover loads increases
Solution Approach 1:
The patent optimizes the curvature radius and thickness distribution of the curved blade stiffener to balance geometric flexibility with rollover load resistance. The blade maintains sufficient thickness throughout its length, with strategic reinforcement in regions susceptible to rollover, while the curved geometry provides the necessary design flexibility for aerodynamic shaping and structural optimization.
Data Source
AI summary
A wing may include a wing skin, a laminate composite first stringer, a rib, and at least one fastener. A majority of the first stringer may be characterized by a stacked plurality of generally planar plies of reinforcement material structurally joined as a stack to an interior surface of the wing skin and extending generally parallel to the interior surface and a span-wise direction of the wing along a substantial portion of the interior surface. The first stringer may have a generally solid trapezoidal cross section when viewed in a plane that is generally perpendicular to the span-wise direction. The rib may be positioned adjacent the interior surface, and may extend generally perpendicular to the span-wise direction. The trapezoidal cross section may be interfaced with the rib flange. The fastener may extend through the wing skin, the trapezoidal cross section, and the rib flange.