Composite Lightning Protection via Conductive Ply and Flashover Point
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Solution Overview
Problem
Composite surfaces, particularly in aircraft, are vulnerable to puncture from lightning due to existing protection methods being heavy, difficult to apply, and prone to surface cracking, which can lead to catastrophic failures.
Innovation Solution
A method involving a composite structure with a conductive ply on the outer surface and a non-conductive ply underneath, along with a flashover point created between the conductive ply and fasteners to divert lightning currents, minimizing the risk of puncture by maintaining a lower flashover voltage than puncture voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal foils or interwoven wires are added to the composite surface for lightning protection, then protection against lightning attachment is improved, but weight increases and application becomes difficult
Solution Approach 1:
The patent uses a composite structure with alternating conductive and non-conductive plies integrated into the composite material itself. This eliminates the need for separate metal foil or wire layers, achieving lightning protection through the composite structure's inherent design rather than adding separate protective layers.
Solution Approach 2:
The conductive plies serve multiple functions: they provide lightning protection, maintain structural integrity, and enable electrical continuity throughout the composite structure. This multi-functionality eliminates the need for dedicated separate protection layers that would add weight.
2Reliability
If metal foils or interwoven wires are added to the composite surface for lightning protection, then protection against lightning attachment is improved, but application difficulty increases due to special processes required
Solution Approach 1:
The conductive and non-conductive plies are manufactured as integral parts of the composite structure using standard composite manufacturing processes. This eliminates the need for special application processes required for metal foils or interwoven wires, making the structure easier to manufacture.
Solution Approach 2:
The lightning protection function is merged with the structural composite material itself. The conductive plies are combined with non-conductive plies to form a unified composite structure that provides both structural integrity and lightning protection through standard manufacturing processes.
3Reliability
If metal foils or interwoven wires are added to the composite surface for lightning protection, then protection against lightning attachment is improved, but surface cracking occurs due to coefficient of thermal expansion differences
Solution Approach 1:
The conductive and non-conductive plies are manufactured from the same base materials and undergo the same manufacturing processes, ensuring uniform thermal expansion characteristics throughout the structure. This homogeneity prevents the coefficient of thermal expansion differences that cause surface cracking in composite structures with metal overlays.
Solution Approach 2:
The alternating ply structure of conductive and non-conductive materials creates a homogeneous composite with matched thermal expansion properties. This integrated composite structure eliminates the interface between dissimilar materials that would cause differential thermal expansion and subsequent cracking.
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 configuration provides effective lightning protection that is cost-effective and minimizes parasitic weight, preventing catastrophic failures while allowing lightning currents to safely divert away from underlying systems.
Implementation Method 1
a first composite conductive ply is located on the outer surface of the composite structure and a second non-conductive composite ply is located directly underneath the conductive ply isolating lightning currents to the conductive ply
Implementation Method 2
inserting a flashover point, by creating a distance outwards from an outer edge of the first composite conductive ply to a fastener... as the flashover voltage between conductive ply and the fastener is lower than the puncture voltage
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2C~3
AI summary
A method and system of preventing lighting from puncturing composite surfaces is provided. The method includes reconfiguring plies of a composite surface so that a composite conductive ply (24) is located on the outer surface of the composite surface (28) and a non-conductive composite ply (30) is located directly underneath the conductive ply and inserting a flashover point (32) between an outer edge (34) of the conductive ply and a fastener (36) attaching the composite surface to a support structure.