Plated Titanium Fasteners for EME Protection in Composite Assemblies
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Solution Overview
Problem
Mechanical fasteners, particularly those made of titanium, face issues with wear resistance and galvanic compatibility with aluminum alloys, and they can contribute to electromagnetic effects (EME) in aircraft structures, such as sparking and heat generation due to poor conductivity and fiber connectivity in composite materials.
Innovation Solution
A mechanical fastener system with plated components, including a base material like titanium, a conductive bonding layer, and a lubricious conductive metal plating, which enhances conductivity and galvanic compatibility, reducing the likelihood of EME by improving the conduction path and friction coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If titanium is used for mechanical fasteners, then light weight and corrosion resistance are improved, but wear resistance deteriorates and galvanic compatibility with aluminum alloys worsens
Solution Approach 1:
The fastener uses a composite material structure with a titanium base material providing strength and light weight, while a chromium nitride coating layer provides wear resistance. This combination allows the fastener to maintain the high strength-weight ratio of titanium while gaining the wear resistance of ceramic-like coating materials.
Solution Approach 2:
The chromium nitride coating acts as an intermediary layer between the titanium fastener and the aluminum alloy substrate, preventing direct galvanic contact. This intermediate layer eliminates galvanic incompatibility while allowing the titanium fastener to maintain its structural advantages.
2Strength
If titanium is used for mechanical fasteners, then light weight and corrosion resistance are improved, but galvanic compatibility with aluminum alloys deteriorates
Solution Approach 1:
The chromium nitride coating serves as a galvanic isolator between the titanium fastener and aluminum alloy substrate. This intermediate non-conductive or low-conductive layer prevents the formation of galvanic cells, eliminating corrosion issues while allowing the titanium fastener to maintain its high strength-weight ratio.
Solution Approach 2:
The fastener combines titanium base material with a chromium nitride coating to create a composite structure that provides both mechanical strength and galvanic isolation properties, making it compatible with aluminum alloy substrates.
3Ease of manufacture
If conventional fasteners are used in composite structures, then structural assembly is achieved, but electromagnetic effects worsen due to poor conductivity and current density concentration
Solution Approach 1:
The chromium nitride coating changes the electrical conductivity parameters of the fastener surface, creating a controlled conductive path that manages lightning strike current distribution. This parameter modification reduces current density concentration at the fastener-composite interface while maintaining structural assembly capabilities.
Solution Approach 2:
The chromium nitride coating acts as an intermediary layer that mediates the interaction between the metallic fastener and the composite structure, providing a controlled electrical interface that manages electromagnetic effects while enabling structural assembly.
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 plated fastener system provides effective EME protection by reducing current density and the risk of sparking, improving conductivity, and ensuring galvanic compatibility with various substrates, thus enhancing the safety and reliability of structural assemblies.
Implementation Method 1
The bonding layer may include one or more conductive metals... improving a conduction path between the fastener and the composite structure may reduce the likelihood of sparking or other problematic EME
Implementation Method 2
The metal plating may include one or more lubricious and conductive metals... reducing the likelihood of EME by improving the conduction path and friction coefficient
Data Source
AI summary
A mechanical fastener system for EME protection, including at least one plated component, wherein the at least one plated component includes a base material, a bonding layer disposed over the base material, and a metal plating disposed over the bonding layer.