Machinable CMC Insert With Sacrificial Layer

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Solution Overview

Problem

Ceramic matrix composite (CMC) components in gas turbine engines face challenges with machining, as it exposes fibers and leads to cracks and reduced tolerance, necessitating the development of a solution to protect the fibers during machining.

Innovation Solution

A sacrificial layer with unarranged ceramic fibers is used, infiltrated with silicon metal to join with the structural component, which includes silicon carbide fibers, allowing for machining without exposing the structural component's fibers, thus preventing cracks and maintaining tolerance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If CMC components are machined to achieve precise dimensions, then manufacturing precision is improved, but fiber exposure occurs leading to cracks and reduced reliability

Engineering Contradiction:

Improvedimensional precisionVSAvoidfiber integrity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

A sacrificial layer is applied to the CMC component surface before machining operations. This preliminary protective layer prevents fiber exposure and damage during subsequent machining, allowing precise dimensional work to be performed on the protective layer rather than the fragile CMC fibers themselves.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sacrificial layer acts as an intermediary material between the machining tool and the CMC component. It absorbs the mechanical stress and cutting forces, protecting the underlying fibers while still allowing the machining process to achieve the desired dimensional precision on the component surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a sacrificial layer is applied to protect fibers during machining, then fiber integrity is maintained, but device complexity increases

Engineering Contradiction:

Improvefiber integrityVSAvoidcomponent structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The sacrificial layer is designed with homogeneous material properties and uniform thickness across the component surface. This simplifies the application process and ensures consistent protection during machining, reducing the complexity that would arise from variable or non-uniform protective layers.

Inventive Principle:

Principle #33Homogeneity

Solution Approach 2:

The sacrificial layer undergoes parameter changes through controlled removal or transformation during the machining process. By designing the layer to change state or be selectively removed, the temporary complexity of having an additional layer is resolved, leaving the simplified original CMC component structure intact.

Inventive Principle:

Principle #35Parameter changes

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

This approach enables machining of CMC components without fiber exposure, maintaining their mechanical integrity and tolerance, and forming a continuous ceramic matrix for enhanced durability.

Implementation Method 1

infiltrating the structural component and the sacrificial layer with silicon metal to join the structural layer and the sacrificial layer

Methodology Applied

Scientific EffectInfiltration:

Data Source

PatentUS10401028B2Machinable CMC insert

Publication Date: 2019.09.03 ROLLS ROYCE NORTH AMERICAN TECHNOLOGIES INC

AI summary

An assembly comprising a structural component and a sacrificial layer, and method for producing the same. The structural component may comprise silicon carbide fibers within a silicon carbide matrix. The sacrificial layer may be joined to the structural component and may comprising unarranged ceramic fibers, wherein the sacrificial layer may comprise a volume fiber fraction lower than a volume fiber fraction of the structural component.