Dielectric Fasteners for Lightning Protection in Composite Aircraft
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Solution Overview
Problem
Composite aircraft structures are vulnerable to electromagnetic effects from lightning strikes due to their inability to conduct away extreme electrical currents, leading to arcing and sparking issues.
Innovation Solution
The use of fasteners with dry dielectric coatings and seals at select locations, including nuts with outer dielectric seals and collars with central openings featuring dielectric coatings or seals, to divert and inhibit lightning currents, thereby preventing arcing and sparking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If composite materials are used for aircraft structures, then weight is reduced and fuel efficiency is improved, but the structure becomes vulnerable to electromagnetic effects from lightning strikes
Solution Approach 1:
The patent introduces dielectric seals and coatings as intermediary elements between the composite structure and lightning current paths. These dielectric barriers (such as sealant material with dielectric properties) interrupt the conductive path that lightning would follow across fastener interfaces, preventing arcing and electromagnetic pulse generation while allowing the composite structure to remain lightweight
Solution Approach 2:
The patent employs composite protective coatings combining conductive and dielectric materials. For example, a conductive coating may be applied to the fastener shaft to provide a controlled current path, while dielectric coatings or seals are applied at critical interfaces to prevent arcing. This multi-material approach maintains the lightweight benefit of composite structures while providing tailored electromagnetic protection
2Reliability
If dielectric sealant is used to fill gaps between fastener parts, then arcing and sparking are prevented, but the complexity of the fastening system increases
Solution Approach 1:
The patent integrates dielectric sealing functionality directly into the fastener components themselves rather than requiring separate sealing elements. For example, dielectric seals are incorporated into the fastener head or nut design, and dielectric coatings are applied to fastener surfaces during manufacturing. This merging of functions reduces the number of discrete parts and simplifies assembly while maintaining reliable protection against arcing
3Reliability
If conductive coatings are applied to fastener shafts, then lightning current is diverted along the fastener, but the manufacturing complexity increases
Solution Approach 1:
The patent specifies controlled parameter ranges for coating applications to balance protection effectiveness with manufacturing simplicity. For example, conductive coatings are applied to specific portions of the fastener shaft with controlled thickness (sufficient to provide conductivity but not so thick as to cause excessive weight or interference), and dielectric seals are dimensioned with specific thickness ranges (e.g., 0.002 to 0.010 inches) that provide adequate electrical insulation while maintaining ease of application and quality control
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
This solution effectively protects against electromagnetic effects by blocking electrical paths and reducing contact resistance, offering weight savings, ease of installation, and redundant protection in aircraft structures.
Implementation Method 1
The coating and the seal have a thickness and composition for inhibiting lightning current
Data Source
Figure 1~3B
Figure 2
Figure 4A~4B
AI summary
Fasteners are inserted into a stack of members and terminated with parts having at least one of a dry dielectric coating and an inner dry dielectric seal at select locations to protect against electromagnetic effects (EME).