Curable Adhesive Sheet for Strain Gauge Bonding

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Solution Overview

Problem

Existing adhesives for strain gauges can lead to uneven thickness application, reducing measurement accuracy due to incomplete strain transmission, and may relax strains in substrates, hindering accurate detection.

Innovation Solution

A stickable-curable adhesive sheet with a pressure-sensitive adhesive component and a curing component, ensuring uniform thickness and high initial tensile elastic modulus after curing, which effectively transmits deformation to the strain gauge.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If instantaneous adhesive for strain gauge is applied to the test piece, then the strain gauge can be bonded to the test piece, but unevenness in thickness easily occurs and measurement accuracy is reduced

Engineering Contradiction:
Improvebonding reliabilityVSAvoidadhesive thickness uniformity
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The adhesive is pre-formed into a sheet with controlled thickness before application. This preliminary action of creating a uniform thickness adhesive sheet eliminates the thickness variation problem that occurs during manual application, while maintaining bonding reliability through the pre-established adhesive layer.

Inventive Principle:
Principle #10Preliminary action

2Reliability

If instantaneous adhesive for strain gauge is used, then the strain gauge can be bonded to the test piece, but the strain gauge and test piece are not fixed until curing and relative position may deviate

Engineering Contradiction:
Improvebonding strengthVSAvoidcuring time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The adhesive sheet is pre-formed with controlled thickness and properties before application. This preliminary preparation ensures that once applied, the adhesive provides immediate positioning stability and maintains the relative position of the strain gauge and test piece during the curing process, preventing deviation.

Inventive Principle:
Principle #10Preliminary action

3Ease of operation

If substrate-less double-sided pressure-sensitive adhesive sheet is used, then the strain gauge can be bonded to the test piece, but the elastic modulus is too low and strain cannot be accurately transmitted

Engineering Contradiction:
Improvebonding easeVSAvoidstrain transmission accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The adhesive composition is modified by changing the rubber component content to 5-50 parts by mass per 100 parts by mass of acrylic component, and adjusting the acrylic component structure and crosslinking agent content. These parameter changes increase the elastic modulus from 10^7 Pa to 10^9-10^10 Pa, enabling accurate strain transmission while maintaining bonding ease through pressure-sensitive adhesiveness.

Inventive Principle:
Principle #35Parameter changes

4Measurement precision

If adhesive with high elastic modulus is used, then strain can be accurately transmitted to the strain gauge, but the adhesive may be too rigid and difficult to apply uniformly

Engineering Contradiction:
Improvestrain transmission accuracyVSAvoidadhesive application ease
Core Design Contradiction:
Measurement precisionVSEase of manufacture

Solution Approach 1:

The adhesive formulation uses 5-50 parts by mass of rubber component per 100 parts by mass of acrylic component, along with specific acrylic component structures and crosslinking agents. These parameter changes create an adhesive that achieves high elastic modulus (10^9-10^10 Pa) for accurate strain transmission, while maintaining pressure-sensitive adhesiveness for easy and uniform application.

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

The adhesive sheet ensures accurate and reliable strain detection by maintaining uniform thickness and high elastic modulus, preventing strain relaxation and improving measurement accuracy.

Implementation Method 1

the stickable-curable adhesive component has pressure-sensitive adhesiveness before curing

Methodology Applied
Scientific EffectPressure-sensitive adhesion: Adhesive

Implementation Method 2

a curing component curing the stickable-curable adhesive component

Methodology Applied
Scientific EffectCuring reaction: Chemical Bonding

Data Source

PatentEP3404076B1Kit comprising a curable adhesive sheet
Publication Date: 2025.04.30 NITTO DENKO CORP
  • EP3404076B1 patent drawingFigure 1A~1B
  • EP3404076B1 patent drawingFigure 2A~2B
  • EP3404076B1 patent drawingFigure 3A~3C

AI summary

A stickable-curable adhesive sheet bonds a deformation/conversion device to an adherend. The stickable-curable adhesive sheet contains a stickable-curable adhesive component and a curing component curing the stickable-curable adhesive component. The stickable-curable adhesive component has pressure-sensitive adhesiveness before curing and the initial tensile elastic modulus at 25°C of the stickable-curable adhesive sheet after curing is 5 × 108 Pa or more.