Adhesion Test Specimens Using Dutch-Weave Fabric Without Edge Sealing

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Solution Overview

Problem

Current methods for testing the quality of material-to-material joints using adhesives are complex, costly, and often result in falsified results due to the fragility of test specimens and the need for edge sealing, which complicates the production and evaluation of adhesion tests, especially when dealing with dissimilar materials like fiber composites.

Innovation Solution

A method involving the use of a dutch fabric or calendered square mesh fabric as a test fabric, which does not tear during mechanical testing, eliminating the need for edge sealing and allowing for more accurate adhesion evaluation by creating a cohesive fracture within the fabric's pores, thereby reducing production costs and improving test reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If square-mesh fabric is used as test fabric, then adhesive penetration is improved, but fabric tearing occurs during testing

Engineering Contradiction:
Improveadhesive bond verificationVSAvoidfabric tear resistance
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent changes the structural parameters of the test fabric by using a truss-like three-dimensional structure instead of a flat square-mesh fabric. This spatial configuration transformation provides both adhesive penetration capability and tear resistance during mechanical testing.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The test fabric transitions from a two-dimensional flat structure to a three-dimensional truss-like structure. This dimensional change enables the fabric to maintain structural integrity during testing while still allowing adhesive penetration through its open framework.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Strength

If edge sealing is applied to prevent fabric tearing, then fabric strength is improved, but manufacturing complexity and cost increase

Engineering Contradiction:
Improvefabric edge strengthVSAvoidedge sealing process
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the edge sealing step from the manufacturing process. The truss-like fabric structure inherently provides sufficient edge strength without requiring additional sealing operations, thereby simplifying the manufacturing process.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The truss-like fabric structure is self-reinforcing at its edges due to its three-dimensional geometry. The structure automatically provides the necessary edge strength through its own configuration, eliminating the need for external edge sealing interventions.

Inventive Principle:
Principle #25Self-service

3Strength

If coarse-mesh fabric with thick threads is used, then fabric strength is improved, but defect detection capability deteriorates

Engineering Contradiction:
Improvefabric thread strengthVSAvoiddefect detection resolution
Core Design Contradiction:
StrengthVSMeasurement precision

Solution Approach 1:

The patent changes the geometric parameters of the fabric structure by creating a truss-like configuration with optimized member dimensions. This allows the use of thinner elements that provide sufficient strength while maintaining smaller mesh openings for improved defect detection resolution.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The truss-like fabric can be constructed using composite material approaches, combining materials with high strength-to-weight ratios. This enables the use of thinner, more resolution-friendly structures while maintaining adequate mechanical strength for testing.

Inventive Principle:
Principle #40Composite materials

4Measurement precision

If thin and fine fabric is used, then defect detection capability is improved, but fabric fragility increases

Engineering Contradiction:
Improvedefect detection resolutionVSAvoidfabric tear resistance
Core Design Contradiction:
Measurement precisionVSStrength

Solution Approach 1:

The patent transitions from a two-dimensional thin fabric to a three-dimensional truss-like structure. This dimensional transformation allows the use of finer elements for improved resolution while the three-dimensional geometry provides inherent structural reinforcement against tearing.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 method produces a test specimen that provides accurate and reliable adhesion testing results without edge sealing, reduces production effort and costs, and allows for better detection of defects, offering a more efficient and precise evaluation of bonding quality across various material combinations.

Implementation Method 1

The meshes created by the weave (openings within the fabric, also called pores) serve as penetration aids for the adhesive into the fabric, thus creating a strong bond between the square-mesh fabric and the bonding surface.

Methodology Applied
Scientific EffectAdhesion: Adhesive

Implementation Method 2

a calendered square mesh fabric is provided

Methodology Applied
Scientific EffectCompression: Compression

Data Source

PatentEP3887797B1Method for producing a test specimen
Publication Date: 2023.05.03 DEUTSCHES ZENTRUM FÜR LUFT UND RAUMFAHRT E V
  • EP3887797B1 patent drawingFigure 1
  • EP3887797B1 patent drawingFigure 2
  • EP3887797B1 patent drawingFigure 3

AI summary

The invention relates to a method for producing a test specimen (30) for a mechanically destructive test of a materially bonded joint, wherein the method comprises the following steps: - providing a planar fibre-composite substrate formed from a fibre-composite material having a fibre material and matrix material embedding the fibre material, - applying at least one test fabric and an adhesive to a substrate surface of the planar fibre-composite substrate, and - curing the adhesive such that a materially bonded joint arises between the test fabric and the substrate surface as a result of the cured adhesive, wherein a Dutch-weave fabric and/or a square-weave fabric are/is provided as the test fabric.