Dielectric-Coated Fastener Termination for Lightning EME Isolation
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Solution Overview
Problem
Lightweight composite materials in vehicles, such as aircraft, do not effectively conduct away extreme electrical currents and electromagnetic forces generated by lightning strikes, and metallic fastener systems used in these structures can create electromagnetic interference issues like sparking and arcing.
Innovation Solution
A metallic fastener termination part with a dielectric-coated metallic core, featuring an internal bore, counterbore hole, and frustoconical wall, which deforms to conform to the fastener and seal, providing protection against electromagnetic effects by applying a compressive force to mechanically interlock and fill a cavity, thereby blocking electrical bonding paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic fastener system is used to assemble composite or metallic structures, then structural strength and assembly reliability are improved, but electromagnetic interference issues such as sparking and arcing occur due to conductivity
Solution Approach 1:
The termination part employs a composite structure consisting of a metallic core providing mechanical strength and a dielectric coating layer providing electromagnetic isolation. This composite material approach allows the fastener to maintain structural integrity while suppressing electromagnetic interference and preventing sparking between metallic components.
Solution Approach 2:
The dielectric coating acts as an intermediary layer between the metallic fastener components, providing electrical isolation and preventing direct contact between conductive surfaces. This intermediary layer blocks electromagnetic field coupling and eliminates arcing paths while allowing mechanical force transmission through the fastener.
2Weight of moving object
If composite materials are used in vehicle structures, then weight is reduced and strength-to-weight ratio is improved, but the ability to conduct away electrical currents and electromagnetic forces from lightning strikes is lost
Solution Approach 1:
The invention extracts the lightning protection function from the composite material itself and implements it through a dedicated metallic fastener system with dielectric isolation. The metallic fastener provides a controlled conductive path for electrical currents, while the dielectric coating prevents uncontrolled arcing, thereby protecting the composite structure from lightning damage.
3Object-generated harmful factors
If a termination part with dielectric coating is used on a metallic fastener, then electromagnetic effect suppression is improved, but manufacturing complexity increases due to coating application and deformation requirements
Solution Approach 1:
The dielectric coating is applied to the metallic core before final assembly and deformation operations. This preliminary coating application ensures that the electromagnetic protection is in place before the termination part undergoes swaging or deformation processes, preventing coating damage and simplifying the manufacturing sequence.
Solution Approach 2:
The dielectric coating is applied selectively to specific surfaces of the termination part where electromagnetic isolation is most critical, such as the outer surface and areas adjacent to the metallic core. This localized coating approach reduces material usage and manufacturing complexity while maintaining effective electromagnetic suppression where needed.
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 solution effectively suppresses electromagnetic effects by ensuring the dielectric coating protects against interference between the fastener and termination part, while the deformed seal occupies the cavity to prevent EME, reducing the risk of sparking and arcing, and maintaining structural integrity with sufficient compressive load deformation.
Implementation Method 1
a layer of dielectric material... the termination part having an internal bore extending through the termination part... An outer surface includes an outer wall extending from the distal end
Implementation Method 2
the frustoconical wall is configured so that a compressive force applied to the frustoconical wall deforms the inner wall to conform to the male threaded portion of the fastener
Implementation Method 3
deforms the seal to fill the cavity... A seal is disposed in the counterbore hole
Data Source
AI summary
An electromagnetic effect suppressing termination part for a fastener formed of a metallic material, the fastener having a head, a shank, and a male threaded portion opposite the head, has a metallic core coated by a layer of dielectric material. An internal bore of the termination part includes an inner wall, a counterbore hole, and a cavity disposed therebetween. An outer surface includes an outer wall, and a frustoconical wall positioned proximally relative to the outer wall, the frustoconical wall extending radially outwardly from the outer wall and having an included angle of less than approximately 90 degrees. A seal is disposed in the counterbore hole, and the frustoconical wall is configured so that a compressive force applied to the frustoconical wall deforms the inner wall to conform to the male threaded portion of the fastener and deforms the seal to fill the cavity.