Reflective Stop-Etch Layer for Safe Laser Coating Removal

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Solution Overview

Problem

Existing high performance coatings on aircraft skins face challenges during laser coating removal processes, as current methods lack precision in preventing damage to the underlying airframe composites, particularly with absorptive materials, due to uncontrolled laser beam penetration.

Innovation Solution

Incorporation of a reflective stop-etch layer made from a low temperature reactive metallic ink that reflects the laser beam, preventing it from penetrating the primer layer and substrate, using materials like silver to ensure minimal weight and thickness while maintaining high reflectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a laser beam is used to remove the coating, then the coating removal efficiency is improved, but the risk of damaging the underlying airframe increases

Engineering Contradiction:

Improvecoating removal efficiencyVSAvoiddamage to airframe

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

A stop-etch layer is introduced as an intermediary between the coating and the airframe substrate. This layer has controlled etch selectivity that allows the laser to remove the coating efficiently while stopping before damaging the underlying airframe, thus mediating between the conflicting requirements of removal efficiency and substrate protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The stop-etch layer is applied in advance before the coating is deposited. This preliminary action creates a protective barrier that prevents laser damage to the airframe during the coating removal process, allowing aggressive laser parameters to be used without risk to the substrate.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the laser calibration is made more precise to prevent substrate damage, then the safety of the airframe is improved, but the complexity of the process increases

Engineering Contradiction:

Improveairframe safetyVSAvoidlaser calibration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The stop-etch layer serves as a built-in safety intermediary that eliminates the need for extremely precise laser calibration. The layer's controlled etch selectivity provides a physical stop that prevents substrate damage even if laser parameters vary, thereby improving reliability without increasing process complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The stop-etch layer provides beforehand cushioning by creating a buffer zone between the laser energy and the airframe substrate. This cushioning effect absorbs excess laser energy and prevents it from reaching the substrate, ensuring airframe safety without requiring complex calibration procedures.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If a reflective stop-etch layer is used to reflect the laser beam, then the protection of the substrate is improved, but the weight and thickness of the coating stack-up increase

Engineering Contradiction:

Improvesubstrate protectionVSAvoidcoating weight

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The stop-etch layer's optical properties are carefully controlled by adjusting its thickness and material composition. By optimizing these parameters, the layer achieves sufficient laser reflection and protection while minimizing the added weight and thickness of the coating stack-up.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The stop-etch layer is implemented as a thin film that provides effective laser protection. This thin film approach ensures that the protective function is achieved with minimal additional weight and thickness, maintaining the lightweight characteristics of the airframe coating system.

Inventive Principle:

Principle #30Flexible shells and thin films

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 reflective stop-etch layer effectively prevents damage to the aircraft skin during laser coating removal, ensuring precise and safe stripping of the coating stack-up without compromising the airframe, reducing the risk of substrate heating and damage.

Implementation Method 1

Incorporation of a reflective stop-etch layer made from a low temperature reactive metallic ink that reflects the laser beam

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS12036623B2Multi-functional layer for stop etch in laser coating removal

Publication Date: 2024.07.16 NORTHROP GRUMMAN SYSTEMS CORP

AI summary

An aircraft skin coating assembly for an aircraft. The coating assembly includes a primer layer deposited on the aircraft skin, an optical stop-etch layer deposited on the primer layer that is reflective at a predetermined wavelength, a coating stack-up deposited on the optical etch-stop layer that provides performance features for the aircraft, and a sealant layer deposited on the stack-up. When a laser coating removal process employing a laser beam is used to remove the coating stack-up for replacement, the stop-etch layer reflects the laser beam to prevent it from penetrating and possibly damaging the aircraft skin.