CMC Shroud Segment Interlocking Joints Brittle Bond Failure

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Solution Overview

Problem

Current methods for joining ceramic matrix composite (CMC) subcomponents in gas turbine shroud segments often result in brittle bond lines, leading to potential catastrophic failure under applied loads, as they fail to effectively utilize the toughness of CMC materials and are challenging to manufacture due to complex geometries.

Innovation Solution

The use of interlocking mechanical joints, such as mortise and tenon, dovetail, and sawtooth joints, that orient reinforcing fibers to break before failure, ensuring that the joint exhibits toughness and damage tolerance, and can be formed during the CMC manufacturing process using methods like melt infiltration, chemical vapor infiltration, or polymer infiltration and pyrolysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional bonding methods (diffusion bonding, reaction forming, melt infiltration, brazing, adhesives) are used to join CMC subcomponents, then the components can be connected, but the bond lines become brittle and prone to catastrophic failure under applied loads

Engineering Contradiction:

Improvejoint reliabilityVSAvoidbond line toughness

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The joint is segmented into multiple discrete features (protrusions and recesses) rather than relying on a continuous bond line. This segmentation allows the joint to fail progressively through individual features rather than catastrophically along the entire bond line, improving reliability while maintaining toughness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The protrusions and recesses are pre-formed during the CMC manufacturing process (before final assembly) using techniques like fiber placement or molding. This preliminary action ensures the interlocking features are integrated into the material structure, providing toughness while eliminating the need for separate bonding operations that create brittle interfaces.

Inventive Principle:

Principle #10Preliminary action

2Strength

If complex geometries are used to achieve interlocking joints, then joint strength and toughness improve, but manufacturing complexity increases significantly

Engineering Contradiction:

Improvejoint toughnessVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The interlocking joint features are merged with the structural components themselves rather than being added as separate elements. The protrusions and recesses are formed as integral parts of the CMC subcomponents during the same manufacturing process, combining the joint function with the structural function and eliminating additional manufacturing steps.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The CMC manufacturing process is made multi-functional by simultaneously creating both the structural geometry and the interlocking joint features. A single manufacturing operation (such as fiber placement or molding) produces both the load-bearing structure and the mechanical interlock, simplifying manufacturing while maintaining joint toughness.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The interlocking mechanical joints provide a damage-tolerant and tough shroud segment that withstands applied loads with graceful failure, minimizing the risk of catastrophic failure and simplifying the manufacturing process by allowing for the use of simpler subcomponents.

Implementation Method 1

interlocking mechanical joints, such as mortise and tenon, dovetail, and sawtooth joints

Methodology Applied

Scientific EffectMechanical interlocking: Mechanical Fastener

Implementation Method 2

melt infiltration (MI)

Methodology Applied

Scientific EffectMelt infiltration: Melting

Implementation Method 3

chemical vapor infiltration (CVI)

Methodology Applied

Scientific EffectChemical vapor infiltration: Chemical Vapour Deposition

Implementation Method 4

polymer infiltration and pyrolysis (PIP)

Methodology Applied

Scientific EffectPyrolysis: Pyrolysis

Data Source

PatentUS11702948B2CMC shroud segment with interlocking mechanical joints and fabrication

Publication Date: 2023.07.18 GENERAL ELECTRIC CO

AI summary

A shroud segment including a forward radial wall, an aft radial wall and at least one interlocking subcomponent. The forward radial wall, an aft radial wall and the at least one interlocking subcomponent are each formed of a ceramic matrix composite (CMC) including reinforcing fibers embedded in a matrix. The shroud segment further including an interlocking mechanical joint joining each of the forward radial wall and the aft radial wall to the at least one interlocking subcomponent. Methods are also provided for joining the forward radial wall and the aft radial wall to the at least one interlocking subcomponent using an interlocking mechanical joint.