Integral CMC Fastener with Non-Polymer Rigidization

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Solution Overview

Problem

Existing attachment methods for ceramic matrix composite (CMC) components in aerospace and industrial gas turbine engines face challenges such as low through-thickness and interlaminar properties, leakage issues, and difficulties in controlling tolerances, particularly with traditional fasteners.

Innovation Solution

A method of forming an integral fastener for CMC components involves creating a fiber preform with an opening, rigidizing it with a non-polymer based material, machining the opening, and infiltrating a matrix material to form a single-piece ceramic matrix composite component with a fastener that is woven from fibers, eliminating gaps and improving interlaminar properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a CMC fastener is machined from a flat CMC panel and inserted into an opening to connect the CMC component to the metal support structure, then the attachment function is achieved, but leakage around the fastener head occurs and tolerance control between the fastener and opening becomes difficult

Engineering Contradiction:

Improveattachment reliabilityVSAvoidleakage around fastener head

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The fastener and CMC component are merged into a single integral structure through simultaneous infiltration of matrix material into both the preform and fastener. This eliminates the gap between the fastener head and component surface, preventing leakage while maintaining attachment functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The opening is machined into the rigidized preform before the fastener is inserted and before final matrix infiltration. This preliminary machining ensures precise tolerance control and proper fit between the fastener and opening, eliminating leakage paths.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If a CMC fastener is used to connect the CMC component to the metal support structure, then attachment is achieved, but processing expenses increase and difficulty in controlling tolerances between the fastener and opening occurs

Engineering Contradiction:

Improveattachment functionVSAvoidprocessing expenses

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The fastener and CMC component are manufactured as a single integrated part through simultaneous matrix infiltration, eliminating separate machining and assembly operations. This reduces processing expenses while ensuring precise tolerance control between the fastener and opening.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The opening is machined into the rigidized preform before final assembly and infiltration, allowing precise tolerance control to be established early in the manufacturing process rather than requiring expensive post-assembly adjustments.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the fiber preform is rigidized with a polymer based material before inserting the fiber fastener, then the preform structure becomes rigid for machining, but additional processing steps and potential contamination are introduced

Engineering Contradiction:

Improvemachinability of preformVSAvoidnumber of processing steps

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The polymer rigidization step is extracted and replaced with a non-polymer alternative. This removes the need for subsequent polymer removal steps, reducing the total number of processing steps while maintaining the ability to machine the preform.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A non-polymer rigidizing material is used that serves its purpose during machining and is then completely removed, leaving no residue. This disposable approach simplifies the overall process by eliminating complex removal and cleanup steps associated with polymer rigidization.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 enhances the interlaminar properties of CMC components, prevents gas leakage, reduces fabrication costs and time, and allows for precise tolerance control, resulting in a robust and efficient attachment method for gas turbine engine components.

Implementation Method 1

the preform is rigidized prior to inserting the fiber fastener into the opening to provide a rigid preform structure

Methodology Applied

Scientific EffectRigidization:

Implementation Method 2

drying the preform to remove any remaining water prior to infiltrating a matrix material

Methodology Applied

Scientific EffectDrying: Desiccation

Implementation Method 3

infiltrating a matrix material into the fiber preform and fiber fastener to form a ceramic matrix composite component

Methodology Applied

Scientific EffectInfiltration: Capillary Action

Implementation Method 4

freezing the preform with water, and drying the preform to remove any remaining water

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS11878943B2Integral ceramic matrix composite fastener with non-polymer rigidization

Publication Date: 2024.01.23 RTX CORP

AI summary

A method of forming an integral fastener for a ceramic matrix composite component comprises the steps of forming a fiber preform with an opening, forming a fiber fastener, inserting the fiber fastener into the opening, and infiltrating a matrix material into the fiber preform and fiber fastener to form a ceramic matrix composite component with an integral fastener. A gas turbine engine is also disclosed.