Composite Structure Integrity Assessment via Fluid Contact Angle

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Solution Overview

Problem

Composite structures in vehicles face uncertainty in structural integration due to inadequate bonding, leading to increased use of fasteners, which adds weight, increases manufacturing costs, and negatively impacts aerodynamic characteristics.

Innovation Solution

A method is developed to determine the sufficiency of structural integration by applying a fluid droplet to the composite structure, measuring the three-dimensional contact angle, and comparing it to a predetermined threshold, allowing for adhesive attachment with reduced or no fasteners, thereby ensuring sufficient structural integration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fasteners are used to couple skin layer and support layer, then structural integration reliability is improved, but weight increases

Engineering Contradiction:
Improvestructural integration reliabilityVSAvoidweight
Core Design Contradiction:
ReliabilityVSWeight of moving object

Solution Approach 1:

The patent replaces the mechanical fastening system (screws, rivets, clips) with a chemical bonding system (adhesive). The adhesive creates molecular-level bonds between the skin layer and support layer, eliminating the need for mechanical fasteners and thereby reducing weight while maintaining structural integration reliability through controlled adhesive bonding properties.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the bonding mechanism from mechanical interlocking (fasteners) to chemical bonding (adhesive). By controlling parameters such as adhesive type, bonding surface preparation, and environmental conditions, the structural integration reliability is achieved without the weight penalty of fasteners.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If fasteners are used to couple skin layer and support layer, then structural integration reliability is improved, but manufacturing cost increases

Engineering Contradiction:
Improvestructural integration reliabilityVSAvoidmanufacturing cost
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent eliminates mechanical fasteners and their associated manufacturing costs (parts, assembly time, labor) by using adhesive bonding. The process becomes simpler and more cost-effective while maintaining reliability through proper adhesive selection and bonding surface preparation.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If fasteners are used to couple skin layer and support layer, then structural integration reliability is improved, but aerodynamic performance worsens

Engineering Contradiction:
Improvestructural integration reliabilityVSAvoidaerodynamic drag
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces protruding mechanical fasteners with a smooth adhesive-bonded surface. This eliminates the disruption to airflow caused by fasteners, thereby improving aerodynamic performance while maintaining structural integration reliability through chemical bonding.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 approach reduces the number of fasteners needed, resulting in weight savings, lower manufacturing costs, and improved aerodynamic performance by enabling adhesive attachment with less than 0.50 fasteners per 0.093 square meters of skin surface area, while ensuring structural integrity.

Implementation Method 1

measuring a three-dimensional contact angle between the composite structure and a portion of the droplet

Methodology Applied
Scientific EffectSurface tension: Surface Tension

Data Source

PatentEP2896954B1Methods and apparatus to determine integrity of composite structures
Publication Date: 2021.04.14 THE BOEING CO
  • EP2896954B1 patent drawingFigure 1
  • EP2896954B1 patent drawingFigure 2
  • EP2896954B1 patent drawingFigure 3A~3B

AI summary

Apparatus and methods to determine structural integrity of composites are described herein. One described example method for determining sufficiency of structural integration of a composite structure (202, 304) for an aircraft includes applying a fluid droplet (300) to a surface of the composite structure (202, 304), determining a three-dimensional contact angle (314, 342, 344) between the surface and a portion of the droplet (300), comparing the three-dimensional contact angle (314, 342, 344) to a threshold angle, and determining whether the structural integration of the composite structure (202, 304) is sufficient based on the comparison.