Conductive Bushing Interference Fit Composite Lightning Protection
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Solution Overview
Problem
Composite wing fuel tanks are more susceptible to electromagnetic effects (EME) due to their non-homogeneous nature and lower conductivity, leading to higher induced lightning currents and increased risks of sparking, which existing high-impedance systems attempt to mitigate but at the cost of complexity, weight, and increased voltage, while low-impedance systems struggle to handle higher currents effectively.
Innovation Solution
A bushing system with a cylindrical conductive body secured in an interference fit within the composite structure, providing a high-pressure, low-resistance electrical path to inhibit arcing and channel electromagnetic effects, featuring a conductive material with a contact pressure of at least 141 kg/cm2 to manage induced lightning currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-impedance systems are used to reduce current in composite structures, then current flow is reduced, but voltage increases and system complexity increases
Solution Approach 1:
The patent changes the impedance parameter of the bushing system from high to low, transforming the electrical characteristics to better suit composite structure applications. This parameter change allows the system to handle higher currents without the voltage buildup and complexity issues associated with high-impedance systems
Solution Approach 2:
The bushing is constructed from composite materials with specific electrical properties - a non-conductive outer layer for insulation and a conductive inner layer for current management. This composite structure enables low-impedance current path while maintaining electrical isolation where needed
2Reliability
If low-impedance systems are installed in composite wing fuel tanks, then current conduction is improved, but the systems must tolerate relatively higher currents without sparking
Solution Approach 1:
The patent modifies the electrical parameters of the bushing by creating a layered structure with different conductivity levels. The conductive inner layer provides a low-impedance path that controls current distribution, preventing concentration of current that would lead to sparking, while the overall system maintains low impedance for effective current conduction
Solution Approach 2:
The bushing acts as an intermediary component between the metallic fitting and the composite structure. It mediates the electromagnetic effects by providing a controlled transition path for lightning currents, managing the current flow to prevent harmful sparking while maintaining effective conduction
3Reliability
If metallic connections are used to install high-impedance systems, then current flow is obstructed, but connections may conduct relatively large induced lightning currents causing sparking
Solution Approach 1:
The bushing uses composite materials with graded electrical properties - the outer non-conductive layer obstructs current flow to prevent sparking, while the inner conductive layer provides a controlled path for lightning currents. This composite construction resolves the contradiction by providing both current obstruction and safe current management within a single component
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 bushing system effectively prevents arcing and reduces the risk of sparking in composite structures by providing a robust, low-resistance electrical path, thereby reducing material, installation, and maintenance costs while adhering to regulatory standards for fuel tank safety.
Implementation Method 1
The contact pressure between the bushing and the composite structure is sufficient to inhibit arcing during the transfers of induced lightning current from the bushing to the composite structure
Implementation Method 2
The bushing is inserted within an opening defined in the composite structure such that the bushing is secured within the opening in an interference fit
Implementation Method 3
The contact pressure between the bushing and the composite structure is sufficient to inhibit arcing
Data Source
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AI summary
A system includes a composite structure and a bushing. The composite structure includes an opening defined therethrough. The bushing includes a cylindrical body sized to be secured within the opening in an interference fit to facilitate providing electromagnetic effects protection in the composite structure. The cylindrical body is fabricated from a conductive material.