Composite Vane Arc Segment with Upstanding Collar for Stress Reduction
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Solution Overview
Problem
Implementing ceramic matrix composites (CMCs) in airfoil fairings of gas turbine engines poses challenges due to their lower material stress limits compared to metallic superalloys, requiring a suitable support scheme that is both strong and manufacturable, as traditional attachment methods like hooks or rails can concentrate stresses and create thermal issues.
Innovation Solution
The use of fiber-reinforced composite airfoil fairings with a hollow section and an upstanding collar formed by cavity fiber plies that neck down to a narrower profile, incorporating a support noodle and over-layer plies for structural integrity and manufacturability, along with a method of fabrication using tapered mandrels to form the airfoil profile and collar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional attachment methods like hooks or rails are used for CMC airfoil fairings, then the attachment structure is simple, but stress concentrations occur and thermal issues arise
Solution Approach 1:
The attachment feature is segmented into multiple functional zones: an upstanding collar portion for structural support, a neck portion for stress distribution, and a fillet portion for thermal stress relief. This segmentation allows each zone to address specific performance requirements independently, preventing stress concentrations and thermal issues while maintaining structural integrity.
Solution Approach 2:
Different regions of the attachment feature have different geometries optimized for their specific functions: the collar provides structural support, the necked-down portion reduces stress concentrations, and the fillet portion manages thermal stresses. This local quality approach ensures that each area of the attachment feature is optimized for its specific role, improving overall reliability without excessive complexity.
2Temperature
If CMC materials are used in airfoils, then high temperature resistance is achieved, but material stress limits are lower compared to metallic superalloys
Solution Approach 1:
The attachment feature geometry is specifically designed with parameter changes: the collar height, neck radius, and fillet radius are optimized to distribute stresses within the lower stress limit of CMC materials. This geometric parameter optimization allows CMC airfoils to withstand operational loads despite their lower material stress limits compared to metallic superalloys.
3Shape
If the tube necks down through a neck portion, then the collar profile becomes narrower than the airfoil profile, but manufacturing complexity increases
Solution Approach 1:
The neck portion geometry is predetermined in the mold design, allowing the fiber-reinforced composite to be formed with the correct necked-down profile during the initial manufacturing process. This preliminary action in the mold design eliminates the need for secondary operations, maintaining ease of manufacture while achieving the required collar profile dimensions.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A vane arc segment (60) includes an airfoil fairing (62) that has a fairing platform (66) and a hollow airfoil section (64) that extends there from. The hollow airfoil section (64) defines an airfoil profile (64a) and surrounds an internal cavity (74). The fairing platform (66) defines a gaspath side (66a; 68a) and a non-gaspath side (66b). The airfoil fairing (62) is formed of a fiber-reinforced composite (70) comprised of fiber plies (72). The fiber plies (72) include at least one cavity fiber ply (80) that is arranged as a tube that circumscribes the internal cavity (74). The at least one cavity fiber ply (80) extends through the fairing platform (66) and defines at least a portion of an upstanding collar (78) on the non-gaspath side (66b) of the fairing platform (66). The upstanding collar (78) defines a collar profile (78a). The tube necks down through a neck portion (84) such that at least a portion of the collar profile (78a) is narrower than the airfoil profile (64a).