Ceramic Fastener Shell-Core Structure for Fracture Toughness
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Solution Overview
Problem
Current ceramic fasteners made from alumina or zirconia suffer from low fracture toughness and impact resistance, necessitating the development of high-temperature, non-conductive fasteners with enhanced toughness and shear force endurance for commercial and aeronautical applications.
Innovation Solution
A ceramic fastener is constructed with a strong ceramic shell, such as sintered alumina or zirconia, and an interior glass-ceramic core, where the shell is formed through methods like slip casting or isostatic pressing, and the glass-ceramic core is crystallized within the shell, bonding to it in compression, thereby increasing the fastener's structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ceramic fasteners are made from alumina or zirconia, then they achieve high temperature resistance and non-conductive properties, but they exhibit low fracture toughness and impact resistance
Solution Approach 1:
The patent applies composite materials by combining a ceramic shell (alumina or zirconia) with a glass-ceramic core. The shell provides high temperature resistance and non-conductive properties, while the glass-ceramic core enhances fracture toughness and impact resistance. This composite structure resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The patent applies local quality by creating a bimetallic-like ceramic structure where different regions have different material properties. The outer shell maintains high temperature resistance, while the inner core provides toughness. This localized differentiation allows each region to optimize its function without compromising the other.
2Reliability
If ceramic fasteners are made from alumina or zirconia, then they achieve non-conductive properties, but they exhibit low impact resistance
Solution Approach 1:
The composite structure combines electrically insulating ceramic materials with a glass-ceramic core that provides impact resistance. The glass-ceramic phase absorbs impact energy through its unique microstructure, while the ceramic shell maintains electrical insulation, resolving the contradiction between reliability and impact resistance.
3Ease of manufacture
If the shell is formed through slip casting or isostatic pressing, then manufacturing complexity is reduced, but the structural integrity and bonding strength may be compromised
Solution Approach 1:
The patent utilizes phase transitions during sintering to achieve strong bonding between the shell and core. The glass-ceramic material undergoes controlled crystallization and densification, creating a metallurgical-like bond that maintains structural integrity while allowing for relatively simple manufacturing processes like slip casting or isostatic pressing.
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 resulting ceramic fastener exhibits improved toughness and impact resistance, capable of withstanding high temperatures and shear forces, addressing the limitations of existing ceramic fasteners.
Implementation Method 1
The pre-glass-ceramic mixture is then melted in a furnace. The melted glass-ceramic mixture is then poured into the interior bore of the shell.
Implementation Method 2
The shell and the glass-ceramic in the shell interior bore are then heat treated to crystallize the glass-ceramic of the core.
Data Source
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AI summary
A ceramic fastener is constructed according to a method where the ceramic fastener has an outer shell of a strong ceramic material such as alumina or zirconia, and the outer shell has an interior bore filled with a glass-ceramic material.