Conductive Foil Repair for Aircraft Composite Lightning Protection
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Solution Overview
Problem
Current methods for repairing composite aircraft skin panels damaged by lightning strikes are time-consuming and require the aircraft to be taken out of service, as they involve hot bond repairs that need fuel drainage and curing time, which is not suitable for in-service repairs.
Innovation Solution
A temporary repair method using a combination of a dielectric layer and a conductive layer applied with pressure-sensitive adhesive, where the conductive layer extends beyond the perimeter of the dielectric layer to prevent arcing and is scored for improved contact, allowing for in-service repairs without grounding the aircraft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot bond repair with film adhesive and solid conductive foil is used, then the lightning protection system is effectively restored, but the aircraft must be taken out of service for fuel drainage and curing (4-8 hours)
Solution Approach 1:
The patent employs a temporary repair system using pressure-sensitive adhesive and conductive foil that can be quickly applied and removed, serving as a short-term solution (up to 2 years) that restores lightning protection without requiring the aircraft to be grounded for extended periods. This disposable approach allows the aircraft to return to service immediately while a permanent repair is scheduled.
Solution Approach 2:
The conductive foil is pre-formed with the lightning protection pattern and the pressure-sensitive adhesive is pre-applied, allowing for rapid installation without requiring on-site curing processes. The adhesive is pre-configured to provide immediate bonding strength, eliminating the need for fuel drainage and extended curing times required by hot bond repairs.
2Reliability
If hot bond repair process is used, then permanent and effective repair is achieved, but the process is complex and requires fuel drainage and curing facilities
Solution Approach 1:
The temporary repair system uses simple, readily available materials (conductive foil and pressure-sensitive adhesive) that can be applied without specialized equipment. The system is designed to be removed and replaced, avoiding the need for complex curing facilities, fuel drainage systems, and autoclave equipment required by permanent hot bond repairs.
Solution Approach 2:
The pressure-sensitive adhesive acts as an intermediary that provides immediate bonding between the conductive foil and the composite skin without requiring thermal curing. This intermediary solution bridges the gap between damaged and functional states, allowing repair in field conditions without specialized infrastructure.
3Ease of manufacture
If conductive foil is applied directly to the composite surface, then the repair process is simplified, but arcing may occur at the boundaries
Solution Approach 1:
The conductive foil is applied as a thin film that conforms to the composite skin surface, creating a continuous conductive layer that prevents arcing. The foil's flexibility allows it to wrap around contours and ensure complete coverage without gaps, while the pressure-sensitive adhesive provides uniform bonding across the entire surface.
Solution Approach 2:
The conductive foil is extended beyond the perimeter of the damaged area in all directions, creating a dimensional buffer zone that prevents arcing at boundaries. This extension into the surrounding healthy composite material provides a safety margin that eliminates the harmful effects of edge arcing while maintaining the simplicity of the application process.
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 method provides a quick and robust temporary repair that can last up to 2 years, enabling the aircraft to remain in service until a permanent repair can be scheduled, reducing downtime and costs.
Implementation Method 1
A repair apparatus for an electrically conductive layer of a composite structure includes a dielectric layer, having a perimeter, secured to the structure; and a conductive layer, secured over the dielectric layer and to the structure around an entirety of the perimeter of the dielectric layer
Implementation Method 2
This design diverts an electrical current such as from a lightning strike away from the fasteners and along the surface of the wing structure away from underlying substructures
Implementation Method 3
A lightning strike to an aircraft causes a high electric current... to flow through the aircraft frame. In a carbon fiber composite structure... the resin between the plies acts as highly capacitive dielectric layers
Data Source
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AI summary
A repair apparatus for an electrically conductive layer of a composite structure (100) includes a dielectric layer (104), having a perimeter, secured to the structure, and a conductive layer (110), secured over the dielectric layer and to the structure around an entirety of the perimeter of the dielectric layer, the conductive layer being treated along a perimeter region thereof to improve a conductive path between the conductive layer and the structure.