Lightning Strike Appliqué for Composite Aircraft Protection

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Solution Overview

Problem

Composite aircraft structures are prone to electrical breakdown and damage from lightning strikes due to their low conductivity, and existing lightning protection methods often cause damage at electrical discontinuities and create hot spots, leading to over-design and duplication of protection schemes.

Innovation Solution

The use of flexible, electrically connected Lightning Strike Appliqué (LSA) gores and Wide Area Lightning Diverter Overlay (WALDO) with conductive layers and flexible electrical connections to create a predictable current distribution path, allowing current from lightning strikes to be safely dissipated through the appliqué to a grounded network, reducing damage to the composite structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If traditional metal body components are used, then lightning strike energy dissipation is efficient, but mass increases

Engineering Contradiction:

Improvelightning strike energy dissipationVSAvoidaircraft mass

Core Design Contradiction:

Loss of energyVSWeight of moving object

Solution Approach 1:

The patent applies composite materials (CFRP) for aircraft skin and structure to reduce mass while maintaining strength. Lightning protection is achieved through integrated conductive networks and sacrificial anodes within the composite structure, allowing efficient energy dissipation without requiring full metal construction.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Sacrificial zinc anodes serve as intermediaries between the lightning strike and the CFRP structure. These anodes preferentially corrode to protect the composite material, providing a controlled path for electrical discharge while preserving the lightweight composite structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If high currents are driven into composite structure, then lightning protection is achieved, but damage occurs at electrical discontinuities and hot spots are created

Engineering Contradiction:

Improvelightning protectionVSAvoiddamage at electrical discontinuities and hot spots

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements localized lightning protection measures at specific discontinuities and interfaces where electrical breakdown is most likely to occur. Conductive coatings and sacrificial anodes are strategically placed at fastener locations, panel edges, and fiber interfaces rather than uniformly across the entire structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Sacrificial zinc anodes provide beforehand cushioning by preferentially corroding to protect the CFRP structure from lightning damage. This sacrificial protection is pre-installed at critical locations to absorb and dissipate lightning energy before it can damage the composite material.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If current return networks are buried inside structure, then protection is provided, but current path prediction becomes difficult and over-design occurs

Engineering Contradiction:

Improvelightning protectionVSAvoidcurrent path prediction and design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent creates equipotential surfaces within the CFRP structure through embedded conductive networks and interconnected sacrificial anodes. This ensures uniform voltage distribution across the structure during lightning strikes, eliminating unpredictable current paths and hot spots by maintaining equal potential at all critical points.

Inventive Principle:

Principle #12Equipotentiality

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 provides reliable and efficient dissipation of lightning currents, minimizing damage to composite structures, reducing the risk of ignition, and offering additional electromagnetic interference shielding while maintaining lightweight and aesthetic integrity.

Implementation Method 1

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

offering additional electromagnetic interference shielding while maintaining lightweight and aesthetic integrity

Methodology Applied

Scientific EffectElectromagnetic shielding: Faraday Cage

Data Source

PatentUS8687342B2Method of surface charge distribution

Publication Date: 2014.04.01 THE BOEING CO

AI summary

A lightning strike protection system for protecting composite structures, an improved lightning strike appliqué (LSA) for such a lightning strike protection system, and a method of protecting composite structures, such as an aircraft fuselage. The LSA is electrically connected to adjacent conductive surfaces, e.g., by a fuzz button or a wire bond inserted in the bottom of the LSA. An adjacent conductive surface may be another LSA, a lightning diverter overlay, or a current return network. Charge, e.g., from a lightning strike to the LSA, flows to the conductive layer through the electrical connector.