CMC Airfoil Sharp Trailing Edge via Ceramic Insert
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Solution Overview
Problem
The manufacturing of composite airfoil components for gas turbine engines is hindered by the stiffness of ceramic composite materials, which makes it difficult to achieve a sharp trailing edge radius without damaging the material, and machining such materials is costly and time-consuming due to their hardness.
Innovation Solution
The use of a ceramic insert with angled faces at the trailing edge, combined with inner CMC fiber layers and a filler to provide stability and a sharp edge, allows for a molded or machined desired radius, and additional layers to ensure exposure of the angled faces for optimal aerodynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CMC material is wrapped around the trailing edge radius, then the airfoil component can be manufactured, but the stiffness of the material causes fiber breaking and material damage
Solution Approach 1:
The trailing edge is divided into two separate components: a ceramic insert providing the sharp trailing edge radius, and CMC plies wrapping around the insert. This segmentation allows each component to fulfill its function without compromising the other - the insert provides the rigid geometric definition while the plies provide structural integration.
Solution Approach 2:
The ceramic insert acts as an intermediary element between the CMC plies and the trailing edge geometry. It mediates the conflict between the need for a sharp radius and the stiffness of CMC material by providing a rigid form around which the plies can wrap without experiencing damaging stresses.
2Ease of manufacture
If CMC material is joined at the trailing edge, then the airfoil component can be manufactured, but the surface finish becomes rough and the trailing edge becomes thicker
Solution Approach 1:
The ceramic insert serves as a precision intermediary that defines the trailing edge geometry. By having CMC plies wrap around this pre-formed insert rather than joining them directly, the insert ensures a smooth, precise trailing edge surface while the plies provide structural continuity.
3Manufacturing precision
If CMC material is machined to the desired radius, then the trailing edge geometry can be achieved, but the manufacturing cost and time increase significantly
Solution Approach 1:
The trailing edge radius is formed preliminarily during the molding process by incorporating the ceramic insert into the mold cavity. This preliminary formation eliminates the need for subsequent expensive and time-consuming machining operations, as the desired geometry is achieved directly in the forming stage.
Solution Approach 2:
The mechanical machining process is replaced with a molding process using a ceramic insert. Instead of removing material through machining, the trailing edge geometry is formed by molding the CMC plies around the insert, which is both faster and more cost-effective for achieving precise radii.
Data Source
Figure 1
Figure 2~4
AI summary
An airfoil component includes an insert that has angled faces joined at an edge that provides an airfoil trailing edge. An outer CMC fiber layer overlaps the angled faces to provide a trailing edge portion of an airfoil.