CMC Airfoil Trailing Edge Support Structure

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Solution Overview

Problem

Ceramic Matrix Composite (CMC) airfoil designs for gas turbine engines face challenges in creating a strong, thin trailing edge that can withstand thermal-mechanical loads without splitting, due to natural geometric stress concentrations at the sharp trailing edge feature.

Innovation Solution

The design incorporates a 'C' shaped forward and aft trailing edge support structure within the CMC airfoil, where the forward support forms an internal pressure vessel and the aft support allows for a split trailing edge to relieve stress, using a minimal number of CMC plies to maintain strength and prevent debonding, while the internal pressure vessel and aft support compartmentalize pressure to resist external forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a thin trailing edge is used in CMC airfoil design, then weight is reduced and temperature capability is improved, but the trailing edge becomes susceptible to splitting due to stress concentration

Engineering Contradiction:

Improvetemperature capabilityVSAvoidtrailing edge strength

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The trailing edge is divided into multiple CMC ply segments (first, second, third, and fourth plies) with different orientations and functions. The first and second plies form the pressure and suction sides, while the third and fourth plies provide additional structural support and stress distribution, preventing splitting while maintaining the thin profile

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The airfoil utilizes CMC composite material with specifically oriented fibers in multiple plies. The fiber orientation in each ply is tailored to provide strength in specific directions, creating a composite structure that resists thermal-mechanical loads while maintaining a thin trailing edge geometry

Inventive Principle:

Principle #40Composite materials

2Shape

If a sharp trailing edge feature is created, then aerodynamic performance is improved, but natural geometric stress concentration occurs where pressure and suction side walls meet

Engineering Contradiction:

Improvetrailing edge geometryVSAvoidstress concentration

Core Design Contradiction:

ShapeVSStress or pressure

Solution Approach 1:

The trailing edge structure employs different ply configurations at different locations. The third and fourth CMC plies are specifically positioned and oriented at the trailing edge region to provide local reinforcement and stress distribution, while other regions of the airfoil maintain their standard construction for optimal aerodynamic performance

Inventive Principle:

Principle #3Local quality

3Strength

If multiple CMC plies are used to strengthen the trailing edge, then bending strength is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvebending strengthVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

Multiple CMC plies are combined in a single integrated manufacturing process. The first, second, third, and fourth plies are stacked and cured together as one unit, forming the complete trailing edge structure in a single manufacturing step, which reduces assembly complexity while providing enhanced bending strength through the multi-ply construction

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP2599959B1Ceramic matrix composite airfoil structure with trailing edge support for a gas turbine engine

Publication Date: 2018.03.07 UNITED TECH CORP

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AI summary

An airfoil (68) for a gas turbine engine includes an aft trailing edge support (98) between a pressure side (82) and a suction side (84). A forward trailing edge support (96) may also be provided. The supports (96,98) are manufactured from a CMC material.