Composite Propeller Spar Collet Retention Design
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Solution Overview
Problem
The challenge in manufacturing composite propeller blades is the inconsistency in stress and vibration at fastener points, which can lead to reduced propeller life, and existing solutions either require complex and expensive designs or drilling holes for fasteners, which is undesirable.
Innovation Solution
A composite spar design that eliminates the need for fasteners by forming a root section with a closed shape configured for retention within a hub assembly, using a collet retention system, thereby avoiding holes and reducing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fasteners are used to connect the blade to the hub assembly, then the blade can be securely retained, but stress concentrations and vibrations at fastener points reduce propeller life
Solution Approach 1:
The patent removes fasteners entirely from the blade root connection. The composite spar is designed with a shaped root section that fits directly into the hub assembly, eliminating the need for fasteners and their associated stress concentrations and vibration points, thereby extending propeller life.
Solution Approach 2:
The blade root and spar are merged into an integrated composite structure. The spar's root section is formed as a continuous composite component that directly interfaces with the hub, combining the functions of structural support and retention without separate fastening elements.
2Reliability
If the entire blade and retention mechanism are formed in a single structure, then fastener-related issues are eliminated, but manufacturing complexity and cost increase
Solution Approach 1:
The blade is segmented into distinct functional components: the spar (structural support), the root section (retention interface), and the blade proper (aerodynamic function). While integrated in construction, these segments allow for specialized design of each function, reducing overall complexity compared to a fully monolithic structure.
Solution Approach 2:
The composite spar serves multiple functions: it provides structural support along the blade length, forms the retention interface at the root, and distributes loads throughout the blade. This multi-functionality reduces the need for separate components, simplifying the overall structure while maintaining reliability.
3Ease of manufacture
If holes are drilled for fasteners, then the blade can be connected to the hub, but moisture ingress and structural integrity are compromised
Solution Approach 1:
The patent extracts the harmful element of holes from the design. By eliminating fasteners and their required mounting holes, the blade structure remains continuous and sealed, preventing moisture ingress while maintaining ease of manufacture through the simplified retention mechanism.
Data Source
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AI summary
A method and apparatus comprising a composite spar. The composite spar has a root section and a main section. The root section is closed and has a shape configured to be connected to a blade retention system. The main section has an open channel. The composite spar is configured for placement inside of a blade.