Sacrificial Fiber Channels for CVI Densification of B4C Preforms

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Solution Overview

Problem

Infiltrating ceramic slurry into fibrous preforms used for aerospace brake stacks and heat sinks is challenging due to limited porosity, making it difficult for slurry particles to penetrate and subsequent densification, especially through the thickness of the preform.

Innovation Solution

A method involving mixing a slurry with sacrificial fibers, injecting it into the fibrous preform, and heating to burn away the fibers, creating channels that improve chemical vapor infiltration (CVI) densification, using a syringe and needle injections for uniform distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If ceramic slurry is injected into fibrous preform, then slurry infiltration is attempted, but limited porosity prevents effective penetration and subsequent densification

Engineering Contradiction:

Improveslurry infiltration qualityVSAvoiddensification difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The preform is segmented into regions with different porosity characteristics by introducing sacrificial fibers that create localized high-porosity channels. These channels act as pathways that divide the infiltration process into manageable segments, allowing slurry to penetrate through the thickness of the preform more effectively.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Sacrificial fibers serve as an intermediary material that temporarily occupies space within the preform structure. These fibers are deliberately removed through burning to create pathways, acting as a mediator that enables subsequent slurry infiltration and densification processes that would otherwise be blocked by the preform's limited porosity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If sacrificial fibers are burned away to form channels, then CVI infiltration is improved, but additional heating steps are required

Engineering Contradiction:

ImproveCVI infiltration rateVSAvoidheating cycle time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The heating cycles for sacrificial fiber removal and CVI infiltration are merged into a single continuous process. The preform is heated to decompose and burn away sacrificial fibers, and then immediately subjected to CVI infiltration without cooling down, thereby combining two separate heating operations into one efficient cycle.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Sacrificial fibers are pre-positioned within the preform structure before the CVI process begins. This preliminary placement ensures that when the fibers are burned away during heating, the resulting channels are already optimally positioned to enhance CVI infiltration throughout the preform thickness.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If multiple needle injections are used to distribute sacrificial fibers, then uniform distribution is achieved, but injection complexity increases

Engineering Contradiction:

Improvefiber distribution uniformityVSAvoidinjection system complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The injection process is segmented into multiple discrete needle insertions at different locations and angles. Each needle injection targets a specific region of the preform, and by systematically segmenting the injection operations, uniform distribution of sacrificial fibers is achieved throughout the entire preform volume.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple needle injections are performed, potentially exceeding the minimum number needed for adequate distribution. This excessive action ensures that even regions that are difficult to reach receive sufficient sacrificial fiber deposition, guaranteeing uniform distribution throughout the preform.

Inventive Principle:

Principle #16Partial or excessive action

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 method enhances the infiltration and densification process, allowing for improved heat management and friction characteristics in brake components by forming channels that facilitate CVI, resulting in increased carbon CVI weight pickup and target composite densities.

Implementation Method 1

heating the fibrous preform to form channels in the fibrous preform by burning away the sacrificial fibers suspended in the injection pathway

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 2

densifying the fibrous preform. In various embodiments, heating the fibrous preform includes a chemical vapor infiltration (CVI) process

Methodology Applied

Scientific EffectChemical vapor infiltration: Chemical Vapour Deposition

Data Source

PatentEP4282847A1Sacrificial materials to improve chemical vapor infiltration of b4c loaded preforms

Publication Date: 2023.11.29 GOODRICH CORP

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AI summary

A method (200) of forming a composite component is provided. The method includes locating a fibrous preform, providing a slurry, mixing the slurry with sacrificial fibers, injecting the slurry into the fibrous preform, heating the fibrous preform, forming channels in the fibrous preform, and densifying the fibrous preform. The sacrificial fibers are suspended in the fibrous preform along an injection pathway such that heating the sacrificial fibers forms the channels along the injection pathway as the sacrificial fibers are burned away.