Stitched Propeller Blade Trailing Edge for Impact Tolerance
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Solution Overview
Problem
Propeller blades face a trade-off between aerodynamic efficiency and structural integrity, as reducing thickness and radius for better aerodynamics compromises damage tolerance against foreign object damage, such as bird impacts.
Innovation Solution
A propeller blade design featuring a trailing edge insert and a shell with yarn stitches that extend through the shell but not the insert, combined with a laminate sheet and specific stitching techniques, enhances structural strength and aerodynamic efficiency while maintaining damage tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the aerodynamic thickness and radius of the propeller blade trailing edge are decreased to improve efficiency, then the aerodynamic performance is improved, but the structural integrity and damage tolerance capacity are reduced
Solution Approach 1:
The trailing edge is divided into two distinct parts: a thin aerodynamic insert (foam, composite, or metal) that provides the desired aerodynamic profile, and a separate shell structure that provides structural strength. This segmentation allows each component to be optimized for its specific function without compromise.
Solution Approach 2:
Stitches of yarn are introduced as an intermediary element that connects the shell parts together and bonds them to the trailing edge insert. The stitches transfer loads between the shell and insert, enabling the thin insert to maintain aerodynamic efficiency while the shell provides the necessary structural integrity.
2Productivity
If the thickness of the trailing edge is reduced to improve aerodynamic efficiency, then the drag is reduced, but the damage tolerance capacity against foreign object damage is compromised
Solution Approach 1:
The trailing edge structure is segmented into a thin aerodynamic insert and a separate shell, allowing the insert to be optimized for aerodynamics while the shell provides damage tolerance.
Solution Approach 2:
The propeller blade utilizes composite material construction with a shell made from composite materials that provide both strength and damage tolerance. The combination of the shell and insert creates a composite structure that maintains reliability while reducing thickness.
3Strength
If a thick trailing edge insert is used to maintain structural strength, then the damage tolerance is improved, but the aerodynamic efficiency is reduced
Solution Approach 1:
The trailing edge is segmented into a thin aerodynamic insert and a shell structure, separating the aerodynamic function from the structural function. This allows the insert to be thin for efficiency while the shell provides strength.
Solution Approach 2:
The stitches of yarn act as intermediaries that bond the thin insert to the shell, allowing the insert to be thin while still maintaining structural strength through the connection to the shell.
4Strength
If the shell thickness is increased to provide sufficient structural strength, then the inter-laminar shear strength is improved, but the overall blade weight and complexity increase
Solution Approach 1:
The stitches of yarn serve as intermediaries that bond the shell to the trailing edge insert, distributing loads and providing inter-laminar shear strength without requiring excessive shell thickness. This reduces the overall weight while maintaining strength.
Solution Approach 2:
The stitching parameters (yarn material, stitch density, stitch pattern) are optimized to provide sufficient inter-laminar shear strength with minimal shell thickness, reducing weight while maintaining structural integrity.
Data Source
AI summary
A propeller blade comprises a root, a tip distal from the root, a trailing edge extending from the root to the tip, a trailing edge, e.g. foam, insert, a shell forming an outer surface of the propeller blade and a plurality of stitches of yarn extending through two parts of the shell adjacent the trailing edge, wherein the yarns do not extend through the trailing edge insert.