Aircraft Rotor Blade Root Stress Distribution via Wrapped Lamina
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Solution Overview
Problem
Existing aircraft rotor blades made of composite materials are prone to rapid failure at the blade root, leading to potential complete detachment from the rotor, which poses a risk to the structural integrity and safety of hovering aircraft.
Innovation Solution
The rotor blade is designed using a forming method that incorporates a contoured block of composite material with a lamina member wrapped around it, providing structural redundancy by distributing stress through a pre-preg lamina and hoops made of graphite or glass fibers, minimizing the risk of detachment and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional composite material blades are used with sequential adhesive joining, then manufacturing cost and complexity are reduced, but reliability deteriorates due to rapid failure propagation at the blade root
Solution Approach 1:
The blade root structure is segmented into distinct functional components: a contoured block providing geometric definition, a wrapped pre-preg lamina providing circumferential reinforcement, and hoops providing additional structural support. This segmentation allows each component to address specific failure modes independently, preventing rapid failure propagation while maintaining overall structural integrity.
Solution Approach 2:
The invention employs multiple composite material systems with different fiber orientations and properties: the contoured block uses woven fabric pre-preg, the wrapped lamina uses unidirectional pre-preg, and the hoops use either unidirectional or woven pre-preg. This multi-material composite approach optimizes mechanical properties for different stress conditions, enhancing reliability without significantly increasing complexity.
2Reliability
If additional structural components are added to prevent failure, then reliability improves, but weight increases
Solution Approach 1:
The wrapped pre-preg lamina is nested around the contoured block, and the hoops are positioned within the blade root structure. This nested configuration provides multiple layers of structural reinforcement within the existing blade geometry, maximizing strength enhancement while minimizing additional material volume and weight.
Solution Approach 2:
The additional structural components (wrapped lamina and hoops) are concentrated specifically at the blade root where stress concentrations and failure risks are highest. This localized reinforcement provides maximum reliability improvement with minimal additional weight, as materials are placed only where mechanically necessary rather than uniformly throughout the entire blade.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design significantly reduces the risk of blade detachment from the rotor hub by distributing stress effectively, providing structural redundancy without significant weight increase, thus enhancing the reliability and safety of the rotor blades.
Implementation Method 1
Blade 1 is made of composite material using the forming method according to the present invention. More specifically, blade 1 is produced by polymerizing an assembly comprising a main structure 5 (Figures 2 and 3) of composite material, and a composite material covering 6 (Figure 1) defining the skin or outer surface 7 of blade 1.
Data Source
AI summary
An aircraft rotor blade (1) having a root portion (2) having a through seat (3) and designed for connection to the rotor; and a main portion (4) extending from the root portion (2). The blade (1) is produced by polymerizing an assembly having a main structure (5) of composite material, and a composite material covering (6) defining the outer surface (7) of the blade (1). At the root portion (2), the main structure (5) has a contoured block (8); and a lamina member (16) extending about at least part of the block (8), and having a first part (17) adhering to a first peripheral portion (12) of the block (8), and a second part (18) spaced apart from and facing a second peripheral portion (13) of the block (8) to form the seat (3); the lamina member (16) having a pre-preg of continuous unidirectional fibres.