Gas Turbine Blade Root Interlaminar Stress Management

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Solution Overview

Problem

Gas turbine engine blades made from Ceramic Matrix Composites face significant interlaminar tensile and shear stress issues due to low interlaminar properties, leading to potential delamination and reduced operational capability.

Innovation Solution

A blade and disk assembly design that incorporates a specific ply arrangement where high interlaminar tensile and shear stress regions are contained within compressive stress zones, with tolerances accounting for offset areas and contact surfaces, and ply sections are positioned to maintain internal stresses below critical limits, utilizing a compliant attachment layer to distribute loads effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If blades are made from Ceramic Matrix Composites, then weight is reduced and temperature resistance is improved, but interlaminar tensile and shear stress resistance deteriorates

Engineering Contradiction:

Improvetemperature resistanceVSAvoidinterlaminar tensile and shear stress resistance

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The patent changes the stress state parameter from tensile to compressive by positioning the attachment region within a compressive stress zone. This parameter change exploits the superior compressive strength of Ceramic Matrix Composites, allowing the material's inherent temperature resistance to be preserved while overcoming its weakness in interlaminar tensile and shear stress resistance.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If traditional blade attachment designs are used, then structural simplicity is maintained, but interlaminar stress concentration increases leading to delamination

Engineering Contradiction:

Improveattachment structure complexityVSAvoidblade attachment reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies local quality by creating a specific ply arrangement only in the attachment region rather than throughout the entire blade. The attachment region is positioned at a specific radial location where compressive stresses naturally occur, and the local fiber orientation is optimized to align with the principal stress directions in this specific zone, providing enhanced reliability without excessive overall complexity.

Inventive Principle:

Principle #3Local quality

3Strength

If ply sections are extended into the disk, then load distribution is improved, but manufacturing precision requirements increase due to offset tolerances

Engineering Contradiction:

Improveload distributionVSAvoidoffset tolerance

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent converts the potentially harmful effect of manufacturing tolerances and offset variations into a beneficial feature. By designing the attachment region to utilize compressive stress zones and incorporating a compliant attachment layer, the structure becomes tolerant of manufacturing variations. The compliance layer absorbs dimensional discrepancies, and the compressive stress state prevents delamination even with offset variations, effectively converting what would be harmful tolerance accumulation into a robust design feature.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentEP2423440B1Root region of a blade for a gas turbine engine

Publication Date: 2017.06.14 UNITED TECH CORP

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Figure 3A~3B

AI summary

A root region (60) of an airfoil includes an inner ply layer group (82) that extends from an innermost root region (60) at least partially into an intermediate platform region (62). The inner ply layer group (82) includes an outermost ply (82-1) and an attachment ply layer group (84) attached to the outermost ply (82-1).