Swageable Dielectric Fastener Termination for Lightning Arcing Suppression
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Solution Overview
Problem
Lightweight composite materials in vehicles, such as aircraft, are prone to electromagnetic effects from lightning strikes due to their inability to conduct away extreme electrical currents, and traditional metallic fastener systems can exacerbate these effects through sparking and arcing.
Innovation Solution
A fastener assembly with a metallic core coated in a dielectric material, featuring a termination part with a frustoconical surface for swaging, which applies a compressive force to deform and interlock with the fastener, using a dielectric seal to prevent electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional metallic fastener systems are used, then structural strength and ease of manufacture are improved, but electromagnetic effects such as sparking and arcing are exacerbated
Solution Approach 1:
A dielectric material is introduced as an intermediary substance coating the metallic fastener core. This dielectric layer acts as a mediator that prevents direct electrical contact between the conductive metallic core and surrounding structures, thereby eliminating sparking and arcing while the metallic core continues to provide structural strength through mechanical fastening.
Solution Approach 2:
The fastener is constructed as a composite structure combining a metallic core for mechanical strength with a dielectric coating for electromagnetic protection. This composite design integrates the beneficial properties of both materials: the metallic core provides tensile strength and fastening capability, while the dielectric layer provides electrical insulation to prevent electromagnetic effects.
2Object-affected harmful factors
If a dielectric coating is applied to the fastener, then protection against electromagnetic effects is improved, but friction and potential coating damage during installation increase
Solution Approach 1:
The fastening mechanism is changed from a threaded system to a swage-based mechanical interlock system. Instead of rotating the fastener to engage threads (which creates high friction and shear forces that can damage the dielectric coating), a swaging tool applies radial compressive force to deform the frustoconical outer surface of the termination part, creating a mechanical interlock that secures the fastener without requiring rotation or high-friction sliding.
3Ease of operation
If a threaded connection is used to secure the termination part, then ease of assembly is improved, but friction increases the risk of dielectric coating damage
Solution Approach 1:
The threaded mechanical connection system is replaced with a swage-based deformation system. The termination part features a frustoconical outer surface that, when subjected to radial compressive force from a swaging tool, deforms to create a mechanical interlock with the structural member. This substitution eliminates the rotational friction and shear forces associated with threading, thereby protecting the dielectric coating while maintaining ease of assembly through a simple linear insertion and swaging process.
4Object-affected harmful factors
If the termination part is made entirely of dielectric material, then electromagnetic protection is maximized, but mechanical interlocking strength with the fastener decreases
Solution Approach 1:
The termination part is constructed as a composite structure with a metallic core providing mechanical strength and a dielectric coating providing electromagnetic protection. The metallic core has sufficient tensile and yield strength to withstand the swaging process and provide mechanical interlocking, while the dielectric coating maintains electrical insulation. This composite design resolves the contradiction by assigning different functional requirements to different material components.
Solution Approach 2:
Different regions of the termination part have different material properties optimized for their specific functions. The inner core region has metallic properties for mechanical strength and deformation capability, while the outer surface has dielectric properties for electromagnetic protection. The frustoconical outer surface is specifically designed to deform under swaging while the dielectric coating remains intact, creating a mechanical interlock without compromising electrical insulation.
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
Effectively suppresses electromagnetic effects by blocking electrical paths and preventing arcing between fasteners and surrounding structures, while maintaining structural integrity and reducing the risk of coating damage from friction.
Implementation Method 1
a metallic core (52) coated by a coating layer (54) of dielectric material
Implementation Method 2
a seal (68) disposed within a counterbore hole (64) formed in an internal bore (62) of the termination body
Implementation Method 3
An outer surface (70) of the termination body includes a frustoconical wall (74) extending radially outwardly from an outer wall (72)
Data Source
Figure 1
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AI summary
An electromagnetic effect suppressing termination part (50) for a fastener (40) formed of a metallic material, the fastener having a head (42), a shank (44), and a male threaded portion (46) 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 (70) includes an outer wall (72), and a frustoconical wall (74) 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 (68) 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.