Countersunk Fastener Void Filling to Prevent Aircraft Paint Halos

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Solution Overview

Problem

Conventional paint systems on composite aircraft often result in 'halos' or visible depressions around countersunk fasteners due to insufficient filling of voids by conventional surfacers, leading to aesthetic issues and potential paint cracking.

Innovation Solution

Forcing an aliphatic urethane surfacer into the voids around fastener heads using a sponge, roller, or brush to completely fill the space, followed by application of a compatible paint system that includes a primer and coats of paint.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional surfacers are applied to the structure, then the painting process can proceed, but visible halos and depressions appear around fastener heads due to insufficient void filling

Engineering Contradiction:
Improvesurface flatness around fastenersVSAvoidpainting process complexity
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent applies surfacer material to fill voids around fastener heads before applying the paint system. This preliminary action ensures that depressions are eliminated in advance, preventing halo formation and ensuring a smooth painted surface without requiring additional corrective steps later in the manufacturing process.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent applies surfacer material specifically to localized areas around fastener heads rather than uniformly across the entire structure. This targeted approach addresses the specific problem of voids and depressions at fastener locations while minimizing unnecessary material application and process complexity elsewhere.

Inventive Principle:
Principle #3Local quality

2Reliability

If voids around fastener heads are not completely filled, then the painting process is simpler, but halos appear and paint cracking may occur

Engineering Contradiction:
Improvepaint system integrityVSAvoidsurfacing process steps
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The surfacing step is performed as a preliminary action before painting, ensuring voids are filled and surface defects are eliminated before the paint system is applied. This prevents reliability issues such as halos and paint cracking by addressing the root cause in advance.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent specifies using aliphatic urethane surfacer material, which has appropriate viscosity and filling characteristics to completely fill voids around fastener heads. This material parameter selection ensures reliable void filling that prevents subsequent paint system failures.

Inventive Principle:
Principle #35Parameter changes

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

Eliminates halos and prevents paint cracking by ensuring voids are filled, enhancing the appearance and durability of the painted surface.

Implementation Method 1

forcing an aliphatic urethane surfacer into a void around the fastener head

Methodology Applied
Scientific EffectMechanical Force: Mechanical Force

Implementation Method 2

the aliphatic urethane surfacer is a two-component, chrome free, chemically cured, high solids, polyurethane surfacer

Methodology Applied
Scientific EffectChemical curing: Chemical Bonding

Data Source

PatentEP2666715B1Method of filling voids around countersunk fastener heads
Publication Date: 2023.10.11 THE BOEING CO
  • EP2666715B1 patent drawingFigure 1A~1B
  • EP2666715B1 patent drawingFigure 2
  • EP2666715B1 patent drawingFigure 3

AI summary

A method for a structure 120 having a countersunk fastener head 112 includes forcing an aliphatic urethane surfacer 430 into a void 124 around the fastener head. The method is applicable to an aircraft 200 comprising a composite skin 420 and a plurality of fasteners 410 having heads 412 countersunk in an exterior surface of the skin 420.