Adhesive Bonding With Resistive Heating for Precise Curing Control

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Solution Overview

Problem

Existing methods for rapidly curing adhesives using thermally activatable adhesives face challenges in achieving precise temperature control and energy efficiency, particularly when dealing with temperature-sensitive surfaces and requiring high heating and cooling rates, often resulting in reduced adhesive strength and potential thermal damage.

Innovation Solution

A method utilizing a flat, thin heating element, such as a metal mesh or foil, is integrated into the adhesive layer to provide localized and efficient heating, allowing for precise temperature control by measuring the resistance of the heating element, which corresponds to the adhesive temperature, thereby optimizing the curing process with minimal energy consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional heating methods (microwave, infrared, hot air) are used for rapid adhesive curing, then curing speed is improved, but energy consumption increases and device complexity increases

Engineering Contradiction:
Improvecuring speedVSAvoidenergy consumption
Core Design Contradiction:
ProductivityVSUse of energy by moving object

Solution Approach 1:

The heating element is integrated directly into the adhesive layer, merging the adhesive application and heating functions into a single unified system. This eliminates the need for separate external heating devices (microwave systems, infrared radiators, hot air blowers), thereby reducing energy consumption and device complexity while maintaining rapid curing capability.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The adhesive layer itself serves as the intermediary medium that directly contacts and transfers heat from the heating element to the joining elements. This direct thermal coupling through the adhesive intermediary enables efficient heat transfer with minimal energy loss, achieving rapid curing without the high energy requirements of conventional indirect heating methods.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Productivity

If conventional heating methods are used for rapid adhesive curing, then curing speed is improved, but temperature control precision deteriorates

Engineering Contradiction:
Improvecuring speedVSAvoidtemperature control precision
Core Design Contradiction:
ProductivityVSMeasurement precision

Solution Approach 1:

A temperature sensor is integrated into the adhesive layer to provide real-time temperature feedback. This feedback mechanism enables continuous monitoring and adjustment of the heating process, ensuring precise temperature control within the optimal curing range (100-250°C) even during rapid curing, thereby preventing both insufficient curing and thermal damage.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent replaces conventional mechanical/external heating systems with an electrically controlled heating element integrated into the adhesive. This substitution enables precise electrical control of heating power and real-time temperature monitoring, achieving superior temperature control precision compared to mechanical heating methods while maintaining rapid curing speed.

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

3Loss of time

If high heating rates are used for rapid curing, then curing time is reduced, but thermal damage risk increases

Engineering Contradiction:
Improvecuring timeVSAvoidthermal damage
Core Design Contradiction:
Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The heating element is positioned specifically within the adhesive layer at the bonding interface, providing localized heating exactly where needed. This local quality approach ensures that high heating rates are applied only to the adhesive and joining elements, while surrounding temperature-sensitive structures remain unaffected, thereby enabling rapid curing without thermal damage.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The integrated temperature sensor provides real-time feedback on the actual temperature at the bonding interface. This feedback enables dynamic adjustment of heating power to maintain the temperature within the optimal curing window, preventing overheating and thermal damage even during rapid curing processes with high heating rates.

Inventive Principle:
Principle #23Feedback

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 enables rapid and reliable adhesive curing with low energy expenditure, maintaining optimal temperature control and achieving sufficient bond strengths for structural connections while being suitable for temperature-sensitive materials.

Implementation Method 1

heating by means of a heating element (5) which is arranged in the thermally activatable adhesive (3) and has an ohmic resistance

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Implementation Method 2

temperature control by measuring the resistance of the heating element (5), which corresponds to the adhesive temperature

Methodology Applied
Scientific EffectElectrical resistance temperature dependence: Electrical Resistance

Data Source

PatentEP3433079B1Method for connecting two joining elements
Publication Date: 2021.08.25 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV
  • EP3433079B1 patent drawingFigure 1
  • EP3433079B1 patent drawingFigure 2
  • EP3433079B1 patent drawingFigure 3a~3g

AI summary

The invention relates to a method for connecting two joining elements (1, 2), said joining elements being connected by means of a thermal activatable adhesive (3) and a flat heating element (5) arranged therein, by appropriate heating of the adhesive, the method comprising the following step: heating the adhesive by applying electrical power to the heating element while measuring the temperature of the adhesive, the amount of electrical power applied to the heating element being controlled according to the measured temperature, the measurement of the temperature of the adhesive being carried out by determining the resistance of the heating element. The invention also relates to a composite produced in this way, consisting of two joining elements, and to an arrangement for carrying out a corresponding method.