Stress-Sensitive Fluorescent Coating for Composite BVID Detection

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Solution Overview

Problem

Detecting Barely Visible Impact Damage (BVID) in composite aircraft parts is challenging due to their opacity and inhomogeneity, as current methods like ultrasonic C-scanning are time-consuming and require skilled technicians, leading to aircraft downtime.

Innovation Solution

A stress-sensitive coating system incorporating fluorescent dyes that change optical behavior in response to stress, allowing for rapid and accurate detection of subsurface damage through changes in fluorescence profiles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If ultrasonic C-scanning is used to detect interior flaws and damage in composite parts, then detection accuracy is improved, but inspection time increases and aircraft downtime increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidinspection time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The fluorescent dye is incorporated into the coating system during the manufacturing process, establishing the detection capability in advance. This preliminary action allows rapid inspection later without requiring time-consuming setup or specialized equipment during actual inspections.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical ultrasonic C-scanning system with an optical detection system using fluorescent dyes. This substitution enables visual inspection methods to detect subsurface damage that was previously only detectable through complex ultrasonic equipment, significantly reducing inspection time while maintaining detection capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Difficulty of detecting and measuring

If ultrasonic C-scanning is used to detect interior flaws in composite parts, then detection capability is improved, but device complexity and skill requirements increase

Engineering Contradiction:

Improvedetection capabilityVSAvoidinspection complexity

Core Design Contradiction:

Difficulty of detecting and measuringVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical ultrasonic scanning equipment with a simple optical inspection system. The fluorescent dye embedded in the coating emits visible light when exposed to UV illumination, allowing inspectors to detect subsurface damage using basic optical equipment rather than sophisticated ultrasonic scanners.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes color/fluorescence changes as the detection mechanism. The fluorescent dye in the coating changes its optical properties in response to subsurface damage, emitting characteristic fluorescence that can be easily observed. This transforms an invisible structural problem into a visible optical signal that can be detected with simple equipment.

Inventive Principle:

Principle #32Color changes

3Weight of moving object

If composite parts are used to reduce weight, then weight reduction is achieved, but detection of subsurface damage becomes more difficult

Engineering Contradiction:

Improvepart weightVSAvoiddamage detection difficulty

Core Design Contradiction:

Weight of moving objectVSDifficulty of detecting and measuring

Solution Approach 1:

The patent applies a specialized coating with fluorescent dye to the surface of the composite part. This creates a localized functional layer that interacts with subsurface damage through stress transfer. The coating's optical properties change in response to local stress concentrations caused by damage, making invisible subsurface issues visible through surface observation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The fluorescent coating acts as an intermediary between the subsurface damage and the inspection system. The coating senses stress changes caused by subsurface damage through mechanical coupling and translates these changes into optical signals. This intermediary enables indirect detection of damage that would otherwise be invisible on the composite surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enables quick and consistent detection of BVID during routine aircraft service, reducing the need for extensive inspections and guiding maintenance efforts, thereby minimizing downtime and labor costs.

Implementation Method 1

at least one polymeric coating layer including a fluorescent dye, wherein an optical behavior of the fluorescent dye changes as a function of a stress of the at least one polymeric coating

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 2

an optical behavior of the fluorescent dye changes as a function of a stress of the at least one polymeric coating

Methodology Applied

Scientific EffectStress-optic effect: Photoelasticity

Data Source

PatentUS8720278B1Method of detecting inconsistencies in composite structures and stress sensitive coatings used therein

Publication Date: 2014.05.13 THE BOEING CO

AI summary

A coating system includes at least one polymeric coating layer comprising at least one fluorescent dye, wherein an optical behavior of the fluorescent dye changes as a function of a stress of the at least one polymeric coating.