Thermoset Composite Joint Heating Above Glass Transition

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Stress concentrations and residual stresses are created in the joint region of large composite components, such as wind turbine blades, due to variations in fit and the use of adhesives or clamping forces, which can weaken the joint and result in unpredictable adhesive usage.

Innovation Solution

A method involving the application of an adhesive between two cured composite components, followed by heating one or both components to a temperature above the glass transition temperature of their thermoset resin matrix to reduce stiffness and minimize stress concentrations, allowing for a precise fit and uniform adhesive usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If adhesive is used as filler to overcome fit variations, then assembly accuracy is improved, but adhesive usage becomes unpredictable and joint strength is reduced

Engineering Contradiction:

Improveassembly accuracyVSAvoidjoint strength

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies heat to raise the temperature of the cured composite component above the glass transition temperature of its thermoset resin matrix, temporarily changing its mechanical properties. This allows the component to deform and accommodate fit variations while maintaining predictable adhesive usage and joint strength through controlled parameter change rather than relying on adhesive filler alone

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If clamping force is applied to remove gaps between components, then adhesive usage becomes uniform, but residual stresses are created that weaken the joint

Engineering Contradiction:

Improveadhesive distribution uniformityVSAvoidjoint strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent uses thermal parameter changes to temporarily reduce the stiffness of the cured composite component by heating it above the glass transition temperature. This allows the component to naturally conform to the mating surface under its own weight or minimal clamping force, achieving uniform adhesive distribution without creating damaging residual stresses from high clamping forces

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent transforms the static, rigid cured composite component into a temporarily dynamic state by heating it above the glass transition temperature. This allows the component to deform and adapt to fit variations during assembly, then returns to its original rigid state after cooling, eliminating the need for continuous high clamping forces that create residual stresses

Inventive Principle:

Principle #15Dynamics

3Strength

If cured composite components are used for assembly, then structural integrity is maintained, but stiffness prevents accommodation of fit variations

Engineering Contradiction:

Improvestructural integrityVSAvoidfit accuracy

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent temporarily changes the temperature parameter of the cured composite component to above the glass transition temperature of the thermoset resin matrix. This transforms the material from a rigid, brittle state to a more compliant state that can deform to accommodate fit variations, while maintaining the structural integrity of the composite reinforcement. After assembly, cooling restores the original stiffness and strength

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

This method eliminates residual stresses and ensures consistent adhesive usage, enhancing the strength and quality of composite joints by allowing for precise alignment and deformation to accommodate fit variations, thereby improving the structural integrity of composite components.

Implementation Method 1

heating the first composite component in the joint region to a temperature above the glass transition temperature of the thermoset resin matrix of the first composite component. The step of heating the first composite component to a temperature above the glass transition temperature of the thermoset resin matrix of the first composite component reduces the stiffness of the first composite component

Methodology Applied

Scientific EffectGlass transition temperature:

Data Source

PatentUS10179359B2Joining method of composite parts having a thermoset matrix, and wind turbine blade manufactured using this said method

Publication Date: 2019.01.15 VESTAS WIND SYSTEMS AS

AI summary

A method of fabricating a composite joint from a first cured composite component (13) and a second cured composite component (14), the first and second cured composite components (13, 14) comprising fiber elements embedded in a thermoset resin matrix; the method comprising the steps of providing an adhesive (15) on at least one of the first and/or second composite components (13, 14); forming a joint region between the first and second composite component by bringing the first and second composite component into contact with each other with the adhesive (15) therebetween; applying a force to the joint region (16, 17); and heating the first composite component in the joint region to a temperature above the glass transition temperature of the thermoset resin matrix of the first composite component.