Thermostructural Composite Fabrication with Dual Interphase Layers

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Solution Overview

Problem

Existing methods for fabricating complex-shaped thermostructural composite material parts using liquid techniques struggle to ensure a continuous interphase between fibers and the matrix, which is crucial for mechanical properties and deformation, especially when using carbon or ceramic materials.

Innovation Solution

A method involving chemical vapor infiltration to form a first thin interphase layer on refractory fibers, followed by shaping and consolidating with a precursor resin, then forming a second interphase layer over the pyrolyzed residue, ensuring a continuous and sufficient interphase for mechanical integrity and deformation capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thick interphase coating is formed on fibers before consolidation by liquid technique, then the embrittlement-relief function is improved, but the ability of the fiber structure to be deformed deteriorates

Engineering Contradiction:

Improveembrittlement-relief functionVSAvoiddeformation ability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

A thin first interphase layer is formed on the fibers before consolidation, preserving deformation ability. The complete interphase structure is then finalized after consolidation, achieving both deformation capability during shaping and embrittlement relief in the final product.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The interphase formation process is divided into two stages: first forming a thin initial layer before consolidation, then completing the interphase formation after consolidation. This segmentation allows each stage to optimize for its specific requirement (deformation vs. embrittlement relief).

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If consolidation is performed by CVI, then the preform can be consolidated, but the tooling occupies major fraction of useful volume in the oven

Engineering Contradiction:

Improveconsolidation capabilityVSAvoiduseful volume of oven

Core Design Contradiction:

Ease of manufactureVSVolume of stationary object

Solution Approach 1:

The patent uses liquid impregnation technique instead of gas-phase CVI for consolidation. The liquid consolidating composition can be applied without occupying oven space, eliminating the tooling volume constraint while achieving effective consolidation of the fiber preform.

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Productivity

If consolidation is performed by liquid technique, then productivity is improved, but it is not possible to guarantee continuous interphase formation on fibers

Engineering Contradiction:

Improveconsolidation speedVSAvoidinterphase continuity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A thin first interphase layer is formed on the fibers before consolidation by liquid technique. This preliminary interphase layer ensures continuous coverage on fibers, while the liquid consolidation proceeds rapidly. The interphase is then completed in a second step, guaranteeing continuity while maintaining high productivity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The interphase formation is segmented into two distinct steps: initial thin layer formation before consolidation to ensure continuity, and completion after consolidation. This resolves the contradiction between rapid liquid consolidation and guaranteed interphase continuity.

Inventive Principle:

Principle #1Segmentation

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 guarantees a continuous interphase between fibers and the matrix, maintaining mechanical properties and allowing for deformation, even in complex shapes, while avoiding the limitations of prior techniques that hindered interphase formation and tooling constraints.

Implementation Method 1

using chemical vapor infiltration to form a first continuous interphase layer on the fibers of a fiber structure

Methodology Applied

Scientific EffectChemical vapor infiltration: Chemical Vapour Deposition

Implementation Method 2

the resin subsequently being transformed into a solid carbon or ceramic residue by pyrolysis

Methodology Applied

Scientific EffectPyrolysis: Pyrolysis

Implementation Method 3

then using chemical vapor infiltration to form a second continuous interphase layer covering the first interphase layer and the solid pyrolysis residue grains

Methodology Applied

Scientific EffectChemical vapor infiltration: Chemical Vapour Deposition

Data Source

PatentUS8828534B2Method of fabricating a thermostructural composite material part, and a part obtained thereby

Publication Date: 2014.09.09 SAFRAN CERAMICS SA

AI summary

The method comprises:using chemical vapor infiltration to form a first continuous interphase on the fibers of a fiber structure made of refractory fibers, the interphase having a thickness of no more than 100 nanometers;impregnating the fiber structure with a consolidation composition comprising a carbon or ceramic precursor resin;forming a fiber preform that is consolidated by shaping the impregnated fiber structure and using pyrolysis to transform the resin into a discontinuous solid residue of carbon or ceramic;using chemical vapor infiltration to form a second continuous interphase layer; anddensifying the preform with a refractory matrix.This preserves the capacity of the fiber structure to deform so as to enable a fiber preform to be obtained that is of complex shape, while nevertheless guaranteeing the presence of a continuous interphase between the fibers and the matrix.