Composite Fastener Interface for Lightning Strike Dissipation

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Solution Overview

Problem

Composite laminates in aircraft do not conduct electrical current effectively due to limited contact area with fasteners, posing a risk of lightning strikes traveling to the aircraft's interior.

Innovation Solution

A fastener system with a tapered head and malleable coating is used, combined with conductive tow groups of fibers oriented in specific directions to enhance electrical conductivity, ensuring effective current dissipation through the composite laminate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional fasteners are used with composite laminates, then the fastener can be installed, but the electrical conductivity is insufficient and lightning currents can travel to the aircraft interior

Engineering Contradiction:

Improvelightning strike protectionVSAvoidelectrical current penetration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a specialized conductive zone around the fastener hole in the composite laminate. This zone contains conductive fibers (such as carbon fibers) with higher electrical conductivity than the surrounding composite material. The conductive fibers are arranged in a pattern that intersects the fastener, providing a localized high-conductivity path at the critical interface between fastener and laminate, while the rest of the laminate maintains its structural design.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by integrating conductive fibers (e.g., carbon fibers) into the composite laminate structure around the fastener. This creates a hybrid material system where the conductive fibers are embedded within or adjacent to the fiber-reinforced polymer matrix, forming a composite that simultaneously provides structural integrity and enhanced electrical conductivity for lightning strike dissipation.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the contact area between fastener and composite laminate is increased, then electrical conductivity improves, but the fastener design becomes more complex

Engineering Contradiction:

Improveelectrical contact qualityVSAvoidfastener design

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of modifying the entire fastener or laminate to increase contact area, the patent applies local quality by concentrating conductive fibers in a specific zone around the fastener hole. This localized approach enhances electrical contact quality without requiring complex modifications to the fastener geometry or installation process, maintaining simplicity while achieving improved conductivity.

Inventive Principle:

Principle #3Local quality

3Reliability

If conductive fibers are added to the composite laminate, then electrical conductivity increases, but the manufacturing process becomes more complex

Engineering Contradiction:

Improveelectrical strike dissipationVSAvoidcomposite laminate fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by pre-arranging conductive fibers in a predetermined pattern and position within the composite laminate before the final curing process. The conductive fibers are placed in a zone that will intersect the fastener, and this arrangement is maintained throughout manufacturing. This preliminary positioning ensures that when the fastener is installed, the conductive fibers are already in optimal positions to provide electrical conductivity, eliminating the need for complex post-manufacturing adjustments.

Inventive Principle:

Principle #10Preliminary action

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 increases the conductivity of electrical strikes by grouping conductive fibers near fasteners, providing a lower resistance path and ensuring current is directed to the outer surface of the laminate, thus preventing interior damage.

Implementation Method 1

The three or more conductive fibers are operational to conduct current of the electrical strike

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

a malleable coating disposed on the tapered head of the fastener, and operational to electrically connect the fastener to the three or more conductive fibers due to a fastener pre-load while the fastener is seated

Methodology Applied

Scientific EffectPhysical contact conduction: Conduction (electrical)

Data Source

PatentUS20260005505A1Electrical strike dissipation

Publication Date: 2026.01.01 THE BOEING CO

AI summary

A system for electrical strike dissipation includes a fastener, a composite laminate, and a structural element. The fastener has a tapered head and a shank. The composite laminate includes a first composite ply and a second composite ply. The first composite ply defines a tapered bore, and has multiple first tow groups. Some first tow groups have three or more conductive fibers stacked directly on each other. The three or more conductive fibers are operational to conduct current of an electrical strike. The tapered bore extends through the first composite ply and is sized to receive the tapered head. The second composite ply defines a straight bore, and has multiple second tow groups. The straight bore extends through the second composite ply and is sized to receive the shank. The structural element is aligned with the composite laminate and is secured to the composite laminate by the fastener.