Propeller Blade Spar Segmentation and Yarn Reinforcement
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Solution Overview
Problem
Propeller blades face a trade-off between aerodynamic efficiency and structural integrity, as reducing thickness for better efficiency also decreases damage tolerance, particularly against foreign object damage like bird impacts.
Innovation Solution
The propeller blade design incorporates a structural spar with a lightweight core material and a variable thickness outer structural member, featuring carbon fibre yarns that extend through the spar to enhance damage tolerance and aerodynamic efficiency, with a core region between plies and a braided outer layer for increased strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thickness of the propeller blade is reduced to improve aerodynamic efficiency, then the aerodynamic performance is improved, but the structural integrity and damage tolerance are reduced
Solution Approach 1:
The propeller blade is divided into multiple functional regions: a first region with a full-thickness spar containing a core material surrounded by composite material, and a second region with a reduced-thickness spar. This segmentation allows different parts of the blade to have different thickness characteristics - thick enough for structural integrity in the root region, and thin enough for aerodynamic efficiency in the tip region.
Solution Approach 2:
The blade employs local quality by providing different structural configurations in different regions. The first region (near the hub) has a thicker spar with core material for maximum strength, while the second region (near the tip) has a thinner spar for aerodynamic efficiency. The core material itself has locally varying properties, being present only in the first region and absent in the second region.
2Productivity
If the thickness of the propeller blade is reduced to improve aerodynamic efficiency, then the aerodynamic performance is improved, but the damage tolerance against foreign object damage is reduced
Solution Approach 1:
The core material in the spar acts as a cushioning element that absorbs and distributes the impact energy of foreign objects (such as birds) before they can penetrate through the blade. This beforehand cushioning protects the internal structure and maintains damage tolerance even in regions where the overall blade thickness is reduced.
Solution Approach 2:
The blade uses composite materials consisting of core material (such as foam or honeycomb) surrounded by composite material plies. This composite structure provides both the reduced thickness needed for aerodynamic efficiency and the damage tolerance needed for reliability, as the core material absorbs impact while the composite plies provide structural integrity.
Data Source
Figure 1~2
AI summary
A spar for a propeller blade comprises central structural member (21) extending from a root to a tip (10) of the spar (22). A first portion (22a) of the central structural member extends from the root of the spar (22) and a second portion (22b) extends from the tip (40) and adjoins the first portion (22a). The central structural member (21) includes a first plurality of plies of composite material on a pressure side (4) thereof and a second plurality of plies of composite material on a suction side (8) thereof wherein the first plurality of plies are in contact with the second plurality of plies in the second portion (22b) from a leading edge (30) to a trailing edge thereof (32). A plurality of yarns extends through the central structural member in at least the second portion.