Ceramic Matrix Composite Surface Structure for Better FOD Resistance

Solution Overview

Problem

Current ceramic matrix composites (CMCs) exhibit insufficient foreign object damage (FOD) resistance, particularly in rotating components like turbine blades, due to mismatches in physical properties between the CMC and its coatings, leading to stress formation and adhesion issues.

Innovation Solution

A method involving the application of an intumescent material onto the CMC preform, followed by heating to expand it, filling voids between fibers and reducing local fiber volume fraction, thereby improving filament distribution and decreasing the elastic modulus of the outer layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If environmental barrier coatings are applied to CMCs to provide protection against harsh environmental conditions, then environmental resistance is improved, but mismatches in thermal expansion and elastic modulus between the CMC and coating lead to stress formation and adhesion problems

Engineering Contradiction:

Improveenvironmental resistanceVSAvoidadhesion strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies local quality by creating a graded coating structure where the elastic modulus varies through the coating thickness. The coating transitions from a high-modulus layer adjacent to the CMC substrate to a lower-modulus outer layer, allowing each region to have different mechanical properties that locally match the requirements for both adhesion and stress reduction

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements parameter changes by systematically varying the elastic modulus parameter through the coating structure. By controlling the composition and thickness of different coating layers, the elastic modulus is graduated from higher values near the CMC interface to lower values at the outer surface, enabling the coating to accommodate thermal expansion mismatches while maintaining strong adhesion

Inventive Principle:

Principle #35Parameter changes

2Reliability

If CMCs use long fiber structures with interface materials to provide damage tolerance via fiber slipping, then fiber toughening is achieved, but FOD resistance remains below levels seen in superalloys

Engineering Contradiction:

Improvedamage toleranceVSAvoidFOD resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs composite materials by combining CMCs with carefully designed coating systems that have graded elastic modulus properties. This composite structure integrates the damage tolerance of long fiber CMCs with the protective and stress-mitigating properties of the graded coating, creating a multi-layered composite that achieves superior FOD resistance

Inventive Principle:

Principle #40Composite materials

3Reliability

If the coating has higher thermal expansion than the CMC matrix/fiber composite, then environmental protection is enhanced, but tensile stress forms during cooling leading to coating cracking and spallation

Engineering Contradiction:

Improveenvironmental protectionVSAvoidtensile stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent applies local quality by creating a graded coating structure where the elastic modulus varies through the coating thickness. The coating transitions from a high-modulus layer adjacent to the CMC substrate to a lower-modulus outer layer, allowing each region to have different mechanical properties that locally match the requirements for both adhesion and stress reduction

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements parameter changes by systematically varying the elastic modulus parameter through the coating structure. By controlling the composition and thickness of different coating layers, the elastic modulus is graduated from higher values near the CMC interface to lower values at the outer surface, enabling the coating to accommodate thermal expansion mismatches while maintaining strong adhesion

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

Enhances FOD resistance by reducing stress response to impact and improving the structural integrity of CMC components, minimizing damage and enhancing adhesion between the CMC and its coatings.

Implementation Method 1

heating the coated ceramic matrix composite preform to expand the intumescent material

Methodology Applied

Scientific EffectIntumescent expansion: Intumescent Materials

Data Source

PatentEP4656619A1Damage resistant ceramic matrix composites

Publication Date: 2025.12.03 RTX CORP

Figure 1A~1C
Figure 2A~2B

AI summary

A method of reducing the local fiber volume fraction and improving the fiber/filament distribution within ceramic fiber tows located within the outer layers (20) of a ceramic matrix composite (CMC) (10) comprising depositing a coating medium containing intumescent material(s), such as in the form of a slurry containing intumescent particles, onto and into the outer layer of a ceramic matrix composite preform to alter the fiber structure of the surface of a ceramic matrix composite (10). The CMC (10) loaded with intumescent material is heated to a temperature where the intumescent material expands, separating the filaments near the outside of the CMC (10) and reducing local elastic modulus. After expansion, the ceramic matrix composite (10) is subjected to densification and then, optionally, coated with an environmental barrier coating (EBC).