CMC Brake Components With Compliant Interlayers for Stress Relief
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Solution Overview
Problem
Traditional methods for fabricating ceramic matrix composite (CMC) structures for aircraft brake systems face limitations in withstanding high temperatures and stresses, particularly due to thermal and mechanical stresses induced by bulk densification techniques, which result in density gradients and reduced strength.
Innovation Solution
The use of a CMC structure with nominally dense plies interleaved with compliant interlayers, bonded using Field Assisted Sintering Technique (FAST), Spark Plasma Sintering (SPS), or localized Joule heating, to enhance bonding and mechanical properties, and incorporating materials like silicon-carbide fiber/silicon-carbide matrix or carbon fiber/carbon matrix with interlayers such as nanofiber mats or preceramic polymer nanofibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bulk densification techniques (CVI, MI, PIP) are used to fabricate CMC structures, then the structure achieves sufficient density, but thermal stresses, mechanical stresses, and density gradients increase, reducing the structure's ability to withstand high temperatures and stresses
Solution Approach 1:
The patent divides the CMC structure into multiple nominally dense plies that are bonded together through incremental bonding processes. This segmentation allows each ply to be densified and bonded separately, reducing the overall thermal and mechanical stresses that would occur in a single bulk densification process, while achieving the required density and reliability for high-temperature brake applications
Solution Approach 2:
The patent applies preliminary densification to individual plies before bonding them together. By pre-densifying each ply to a nominal density and then bonding them incrementally, the process avoids the severe thermal gradients and stresses that would occur in a single bulk densification step, resulting in a structure with reduced internal stresses and improved reliability
2Strength
If traditional bulk densification techniques are used, then the fabrication process is relatively simple, but density gradients increase, reducing the strength of the CMC structure
Solution Approach 1:
The patent segments the densification process into multiple incremental bonding steps, where each ply is densified and bonded separately. This approach produces a more uniform density distribution throughout the final structure compared to bulk densification, eliminating density gradients that would compromise structural strength
Solution Approach 2:
The patent applies partial densification to individual plies before bonding, rather than attempting to densify the entire structure at once. This partial action approach ensures more uniform density distribution and eliminates the density gradients that would occur in bulk densification, thereby improving overall structural strength
3Strength
If plies are layered together to fabricate laminated preforms, then the structure can be designed with specific properties, but the bonds between adjacent laminates are weak, reducing the overall strength of the composite
Solution Approach 1:
The patent applies preliminary densification to individual plies before bonding them together. This preliminary action creates fresh, reactive surfaces on each ply that bond more effectively when joined, resulting in stronger inter-laminar bonds compared to bonding already-densified plies
Solution Approach 2:
The patent replaces traditional mechanical bonding methods with field-assisted sintering techniques (FAST or SPS) that use electrical fields and localized Joule heating to bond plies together. This substitution enables strong bonds between laminates while maintaining manufacturing feasibility, overcoming the weakness of traditional bonding methods
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 improves the strength and thermal resistance of brake components, enabling them to withstand high temperatures and stresses, while reducing thermal and mechanical stresses, and allowing for better bonding and interlaminar properties.
Implementation Method 1
bonded by at least one of a Field Assisted Sintering Technique (FAST), a Spark Plasma Sintering (SPS) process
Implementation Method 2
localized Joule heating process
Implementation Method 3
radiative heating process
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A brake component (112;114;116;118) is disclosed. In various embodiments, the brake component includes a ceramic matrix composite (CMC) structure (200) including a plurality of nominally dense plies (202), interleaved with a plurality of interlayers (204), wherein the plurality of nominally dense plies and the plurality of interlayers are bonded by at least one of a Field Assisted Sintering Technique (FAST), a Spark Plasma Sintering (SPS) process, or a localized heating process. In various embodiments, the brake component is a rotor disk (116) or a stator disk (118).