Multi-layer Flex Circuit Joining for Composite Lightning Protection

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Solution Overview

Problem

Composite materials used in aerospace applications, such as carbon fiber reinforced plastics, have poor electrical conductivity, making them inadequate for distributing and dissipating lightning strikes, which can lead to structural damage.

Innovation Solution

The integration of multi-functional flexible circuits with conductive layers, such as copper or aluminum, into composite structures, along with modular assembly joining clips and repair patches, ensures electrical continuity and isolation, providing effective lightning protection and enabling the incorporation of sensors and connectivity for various applications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If metallic conductors are integrated into composite surfaces to provide lightning protection, then electrical conductivity and lightning current distribution capability are improved, but the structural integrity and electrical isolation between conductive layers must be maintained

Engineering Contradiction:

Improvelightning protection capabilityVSAvoidstructural integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent uses composite material structures combining conductive layers (aluminum or copper foil in solid or expanded mesh form) with dielectric layers (polyimides, fluoropolymers, or similar heat resistant materials) to create a multi-layer assembly that provides both electrical conductivity for lightning protection and structural integrity through the composite nature of the materials

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Dielectric layers are positioned between conductive layers to provide electrical isolation and insulation, preventing unwanted electrical interactions while allowing the conductive layers to function independently for lightning current distribution, thus mediating between the need for conductivity and structural safety

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If multi-layer flex circuits are used for lightning protection, then electrical conductivity is improved, but ease of repair deteriorates due to the complex multi-layer structure

Engineering Contradiction:

Improveelectrical conductivityVSAvoidrepairability

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The multi-layer flex circuit is segmented into discrete conductive layers separated by dielectric layers, allowing individual layers to be addressed and repaired independently. The conductive layers can be applied as separate foil sheets that can be individually replaced or repaired without disrupting the entire multi-layer structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The conductive foil layers are designed as replaceable components that can be easily removed and replaced if damaged, using inexpensive materials such as aluminum or copper foil that can be quickly reapplied to restore functionality without requiring complex repair procedures

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If conductive layers are applied over composite surfaces, then lightning current distribution is improved, but the flexibility and conformability to surface contours must be maintained

Engineering Contradiction:

Improvelightning current distributionVSAvoidflexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The conductive layers are implemented as thin foil sheets (aluminum or copper) that inherently possess flexibility and can be conformably applied to curved and complex surface contours of aircraft components, while still providing effective lightning current distribution pathways

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent transitions from rigid planar conductive surfaces to flexible three-dimensional conformable layers that can adapt to the complex curvature of aircraft surfaces, allowing the conductive path to follow surface contours in multiple dimensions while maintaining electrical continuity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 diverts lightning current, maintains structural integrity, and allows for real-time monitoring and additional functional integration, enhancing the electrical and mechanical properties of composite aircraft surfaces.

Implementation Method 1

A dielectric material electrically isolates the first conductive layer from the second conductive layer

Methodology Applied

Scientific EffectDielectric isolation: Dielectric

Implementation Method 2

capable of distributing and diverting current away from flight critical areas and underlying aircraft components

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS7829796B2Circuit joining assembly materials for multi-layer lightning protection systems on composite aircraft

Publication Date: 2010.11.09 THE BOEING CO

AI summary

An exemplary embodiment provides a multi-layer circuit joining assembly material configured to repair multi-layer flex circuits deployed on or in a composite surface as a lightning protection system. The multi-layer circuit joining assembly material includes a first conductive layer having a first end portion, a second conductive layer having a second end portion, and a dielectric material between the first conductive layer and the second conductive layer.