Composite Propeller Blade Root With Hollow Spar-Reinforced Structure
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Solution Overview
Problem
Existing propeller blades for turboprop engines face challenges in achieving a lightweight, compact root design that can withstand various mechanical loads, including traction, bending, and circumferential compression, while being compatible with variable pitch systems.
Innovation Solution
A method for manufacturing propeller blades using composite material with a compact, rotationally symmetric root, involving 3D weaving of a fibrous blank with an inner recess, insertion of a spar, and densification, followed by machining to form a rotationally symmetric shape, ensuring mechanical strength through oriented yarns and integration with an aerodynamic profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact, rotationally symmetric root is used, then the root size is reduced and adaptability to variable pitch systems is improved, but manufacturing difficulty increases due to the complexity of forming such shapes from composite material
Solution Approach 1:
The root is divided into two distinct zones with different fibrous reinforcement orientations: a first zone with yarns in the span direction for traction and bending resistance, and a second zone with yarns in the chord direction for circumferential compression resistance. This segmentation allows each zone to be optimized for its specific mechanical function while maintaining the overall compact, rotationally symmetric shape required for variable pitch systems.
Solution Approach 2:
Different regions of the root are assigned different material properties through varying fibrous reinforcement orientations. The first zone (span direction yarns) provides different mechanical characteristics than the second zone (chord direction yarns), allowing local optimization of strength properties to match the specific stress patterns in each region while achieving the desired compact geometry.
2Weight of moving object
If composite material is used, then weight is reduced compared to metal, but mechanical strength may be compromised despite the lightweight advantage
Solution Approach 1:
The propeller blade uses composite material consisting of a matrix (polymer, metal, or ceramic) densified with fibrous reinforcement. The fibrous reinforcement provides high strength-to-weight ratio, while the matrix binds the fibers together and transfers loads. This composite construction achieves both weight reduction compared to solid metal and sufficient mechanical strength through the synergistic combination of lightweight fibers and binding matrix.
Solution Approach 2:
The fibrous reinforcement is strategically oriented in different zones of the root: span-direction yarns in the first zone for traction and bending resistance, and chord-direction yarns in the second zone for circumferential compression resistance. This local quality variation ensures that strength is concentrated where mechanically necessary, optimizing the strength-weight ratio throughout the structure.
3Device complexity
If three-dimensional weaving is used to form the fibrous reinforcement, then structural complexity is reduced to a single-piece construction, but the ability to create axisymmetric shapes becomes more difficult
Solution Approach 1:
The three-dimensional woven structure is segmented into distinct zones with different yarn orientations: a first zone with span-direction yarns and a second zone with chord-direction yarns. This segmentation within the single-piece 3D woven construction allows the complex geometry to be created through systematic arrangement of fiber bundles rather than requiring complex tooling or multiple assembly steps.
Solution Approach 2:
The fibrous reinforcement transitions from two-dimensional planar weaving to three-dimensional spatial arrangement of yarns. By organizing yarns in multiple directions (span direction and chord direction) within the root structure, the design achieves axisymmetric shaping capability while maintaining the efficiency of single-piece 3D woven construction.
Data Source
AI summary
A propeller blade or airfoil for a turboprop engine made from composite material including a matrix-densified fibrous reinforcement, the propeller blade or airfoil including, in the direction of its span, a root and an aerodynamic profile. The fibrous reinforcement includes a fibrous preform having three-dimensional weaving with a root preform portion and an aerodynamic profile preform portion. The fibrous preform includes a separation delimiting a recess that forms a cavity extending both into the root and into the aerodynamic profile. A spar is present in the cavity, the spar including an aerodynamic profile shaping portion positioned in a first portion of the cavity and a root shaping portion positioned in a second portion of the cavity. The root has a rotationally symmetric shape.