Whisker-Reinforced Ceramic Threaded Fasteners for High-Temperature Attachment
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Solution Overview
Problem
Current metal fasteners used in thermal protection systems and turbine engine exhaust components fail to meet the requirements of high temperature resistance, low catalycity, high emissivity, and matching thermal expansion with ceramic matrix composites, leading to issues such as overheating and difficulty in maintenance due to their brittleness and notch sensitivity.
Innovation Solution
A high temperature threaded fastener composed of an aluminum oxide ceramic material reinforced with silicon-carbide crystal whiskers, which is designed to have a bolt with an external screw threaded surface and a nut with an internal screw threaded surface, providing high strength, fracture toughness, low catalycity, high thermal emissivity, and matching thermal expansion with ceramic matrix components, while minimizing notch sensitivity and allowing for precise machining and internal thread formation without shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal fasteners are used to attach ceramic matrix components in thermal protection systems, then mechanical attachment is achieved, but the fasteners have high catalycity, low emissivity, high thermal expansion, and cannot withstand extreme temperatures
Solution Approach 1:
The patent applies composite materials by combining ceramic matrix (aluminum oxide) with silicon carbide whiskers to create a fastener that exhibits both high temperature resistance and low catalycity. The composite structure leverages the complementary properties of its constituents: the ceramic matrix provides thermal stability while the silicon carbide whiskers enhance mechanical strength and reduce catalytic activity, resolving the contradiction between temperature resistance and catalycity.
2Object-generated harmful factors
If monolithic ceramic fasteners are used, then low catalycity and high emissivity are achieved, but the fasteners are brittle, notch sensitive, and prone to catastrophic failure
Solution Approach 1:
The patent employs composite materials by integrating silicon carbide whiskers into the aluminum oxide ceramic matrix. This composite structure significantly improves fracture resistance and reliability while maintaining low catalycity. The whiskers act as reinforcement that prevents crack propagation and reduces notch sensitivity, allowing the fastener to withstand thermal shock and mechanical loads without catastrophic failure.
3Manufacturing precision
If ceramic fasteners are machined with screw threads, then precise attachment is achieved, but machining is very difficult and threads are rounded due to firing shrinkage
Solution Approach 1:
The patent applies parameter changes by utilizing the material's properties at different stages of processing. The fastener is formed at elevated temperatures where the ceramic material is more ductile and easier to machine, allowing precise thread formation. After cooling, the material exhibits its final dimensional stability with minimal shrinkage, maintaining thread precision. This temperature-dependent parameter change resolves the contradiction between manufacturing precision and ease of manufacture.
4Strength
If metal fasteners are used in turbine engine exhaust systems, then mechanical attachment is achieved, but the fasteners overheat because ceramics have lower thermal conductivity
Solution Approach 1:
The patent applies composite materials by combining aluminum oxide ceramic matrix with silicon carbide whiskers, where silicon carbide has higher thermal conductivity than aluminum oxide. This composite structure provides both the mechanical strength needed for attachment and improved thermal conductivity to prevent overheating, resolving the contradiction between attachment strength and thermal management in turbine engine exhaust systems.
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
The ceramic fastener achieves reliable attachment and maintenance of ceramic matrix composites in high-temperature environments with improved thermal shock resistance and reduced risk of catastrophic failure, maintaining performance over a wide temperature range and effectively managing heat rejection through radiative transfer.
Implementation Method 1
both the bolt and nut are constructed of an aluminum oxide ceramic material reinforced with silicon-carbide crystal whiskers
Implementation Method 2
These materials must have high emissivity to ensure the maximum rejection of incoming convective heat through radiative heat transfer
Data Source
AI summary
A high temperature fastener including a bolt and a nut, where the bolt and the nut are constructed of an aluminum oxide ceramic material reinforced with silicon-carbide crystal whiskers or silicon nitride.