Lightning Strike Coating Topography for Composite Substrates
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Solution Overview
Problem
Conventional spray-on lightning strike protection (LSP) coatings for composite aircraft and wind turbine blades are less effective due to high contact resistance, which can lead to resistive heating and damage from lightning strikes, as they distribute electrical current through contact interfaces between metal particles rather than providing a continuous conductive path.
Innovation Solution
A method of applying an electrically conductive coating in a flowable form with a three-dimensional surface topography featuring spaced apart protrusions, which creates a Corona effect to distribute lightning current, reducing contact resistance and enhancing protection by forming multiple streamers that carry only a fraction of the current load, thereby mitigating damage to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a spray-on LSP coating is applied to composite aircraft, then the coating can be applied after induction welding is complete, but the coating has high contact resistance leading to resistive heating and damage from lightning strikes
Solution Approach 1:
The LSP coating is segmented into a multi-layer structure with a metallic particle layer, a conductive polymer layer, and an optional topcoat layer. This segmentation allows each layer to perform its specific function: the metallic particles provide conductive pathways, the conductive polymer binds particles and provides additional conductivity, and the topcoat protects the underlying layers while maintaining electrical properties.
Solution Approach 2:
The invention uses composite materials by combining metallic particles (such as aluminum, copper, or silver) with conductive polymers (such as polyacetylene, polypyrrole, or polyaniline) to create a coating that exhibits enhanced electrical conductivity and lightning strike protection properties that neither material could achieve alone.
2Reliability
If co-consolidated metal mesh or expanded metal foil is used for LSP, then continuous conductive path is provided, but metal cannot be integrated into thermoplastic composites that are to be joined by induction welding
Solution Approach 1:
The invention replaces the mechanical co-consolidation process with a post-welding spray application process. Instead of integrating metal mesh or foil into the composite during consolidation, the LSP coating is applied as a sprayable composition after induction welding is complete, eliminating the need for mechanical integration while achieving similar protective functionality.
Solution Approach 2:
The invention changes the physical state and application parameters of the LSP material from solid metal mesh/foil requiring mechanical co-consolidation to a sprayable composition that can be applied as a liquid or paste and then cured to form a protective coating layer.
3Reliability
If individual wires of conductive material are woven into fibers or conductive coatings are deposited on raw carbon-fibers, then continuous conductive path is achieved, but the process becomes complex and cannot be applied to finished composite parts
Solution Approach 1:
The invention performs the LSP coating application as a preliminary action that can be done on finished composite parts before final assembly or painting. The sprayable composition is applied to the completed composite structure, allowing the base composite to be fully formed and welded before adding the protective LSP layer.
Solution Approach 2:
The invention replaces complex mechanical weaving or deposition processes with a simplified spray application method. Instead of weaving individual wires into fibers or depositing coatings on raw carbon fibers during manufacturing, the LSP coating is sprayed onto the finished composite surface, dramatically reducing process complexity.
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 solution significantly improves the electrical conductivity and protective effectiveness of LSP coatings by distributing the lightning strike current over a larger surface area, reducing the risk of damage to composite substrates and providing a more effective alternative to co-consolidated metal plies.
Implementation Method 1
A form is pressed against the electrically conductive coating applied on the composite article while the electrically conductive coating is flowable. The form comprises a plurality of spaced apart depressions. The electrically conductive coating is cured while the form is pressed against the electrically conductive coating on the composite article to create an impression of the form in the electrically conductive coating that includes a plurality of spaced apart protrusions.
Implementation Method 2
A method of applying an electrically conductive coating in a flowable form with a three-dimensional surface topography featuring spaced apart protrusions, which creates a Corona effect to distribute lightning current, reducing contact resistance and enhancing protection by forming multiple streamers that carry only a fraction of the current load
Implementation Method 3
The electrically conductive coating is cured while the form is pressed against the electrically conductive coating on the composite article to create an impression of the form in the electrically conductive coating
Data Source
AI summary
A composite article includes a lightning strike protection coating on a composite substrate. The lightning strike protection coating is formed from electrically conductive material and includes protrusions spaced along the length and width of a portion of the substrate surface. To form the lightning strike protection coating, a form is pressed against electrically conductive coating material on the composite substrate while the electrically conductive coating material is flowable. For example, the form can be a release film used in a composite vacuum bagging process. Suitable release film can have depressions along an inner surface that define an imprint of the coating protrusions. After curing, the coating can be covered with a layer of paint that conceals the protrusions but still allows lightning streamers to penetrate the paint at the protrusions.