Composite Fastener Head and Nut Geometry for Lightning Sparking Control
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Solution Overview
Problem
Metallic fasteners in composite structures face issues with hot particle ejection and edge sparking during lightning conditions due to electromagnetic effects, and existing fastening systems require labor-intensive installation procedures.
Innovation Solution
A fastener system with a head and nut featuring reduced area engagement surfaces, endothermic concentric chambers, and double wedge seal rings to create a pressure-contained system, preventing hot particle ejection and edge sparking, and allowing for direct installation without additional sealing or processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional metallic fasteners with full contact surfaces are used, then electromagnetic energy can be conducted between structural joints, but hot particle ejection and edge sparking occur during lightning conditions
Solution Approach 1:
The fastener head contact surface is designed with a reduced area portion (e.g., central circular area) rather than full surface contact. This local modification creates a pressure-contained system that prevents hot particle ejection and edge sparking while maintaining electromagnetic conduction through the reduced contact area, directly resolving the contradiction between reliability and harmful factors
Solution Approach 2:
The contact surface is segmented into a reduced area portion and excluded peripheral areas. The reduced area portion is positioned to be radially inward of the peripheral edges, creating distinct functional zones that contain pressure and prevent sparking at the edges while maintaining overall electrical conduction capability
2Reliability
If premolded caps are installed over fastener heads to prevent sparking, then electromagnetic protection is improved, but installation time and labor increase
Solution Approach 1:
The electromagnetic protection function is merged directly into the fastener head design through the reduced area contact surface configuration. This eliminates the need for separate premolded caps or additional sealing components, providing protection while maintaining simple, quick installation procedures
Solution Approach 2:
The fastener head's reduced area contact surface automatically provides pressure containment and sparking prevention through its geometric configuration alone, without requiring additional components or installation steps. The design is self-sufficient for electromagnetic protection
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 system effectively prevents hot particle ejection and edge sparking during lightning conditions while simplifying the installation process by using profiled engagement surfaces and endothermic chambers to contain pressure, enhancing electromagnetic energy protection without additional sealing requirements.
Implementation Method 1
at least one endothermic chamber is positioned in the fastener head for hot particle ejection entrapment
Implementation Method 2
create a pressure contained system preventing hot particle ejection and edge sparking during lightning conditions
Implementation Method 3
contact resistance heating may break down the materials and generate hot gas (or plasma) in the hole
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
A fastener system for composite structure providing electromagnetic energy (EME) protection incorporates a fastener (12) having a head with an engagement surface (36) and a shank having a threaded end. A nut (28) is received on the threaded end of the fastener (12), with the nut (28) also having an engagement surface (56). At least one of the head engagement surface and the nut engagement surface incorporates a reduced area portion for engagement of a first mating surface or second mating surface, respectively.