Thermoplastic Edge-Embedding Joint for Multi-Material Bonding

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Solution Overview

Problem

Existing methods for bonding lightweight materials in industries like automotive and aviation face challenges such as unreliable adhesive bonds, high manufacturing costs, and difficulties in compensating for thermal expansion differences, especially when bonding thermoplastic parts to non-liquefiable materials.

Innovation Solution

A method involving a thermoplastic part with a solid state being brought into relative movement with a second object having a flat sheet portion, generating friction heat to melt and embed the edge of the second object into the thermoplastic material, forming a reliable and cost-efficient connection through rotational movement and mechanical pressure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If adhesive bonds are used to bond thermoplastic parts to non-liquefiable materials, then bonding capability between different materials is improved, but reliability of the bond deteriorates due to inability to detect degrading bonds and susceptibility to shearing forces from thermal expansion differences

Engineering Contradiction:
Improvebonding capabilityVSAvoidbond reliability
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent replaces adhesive bonding with a mechanical bonding system using a blind rivet that has a bonding element capable of bonding to both thermoplastic and non-liquefiable materials. The bonding element is inserted into the blind rivet and secured by deforming the rivet body, creating a mechanically secure connection that accommodates thermal expansion differences without relying on adhesive bonds that are susceptible to shearing forces.

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

Solution Approach 2:

The bonding element is made of a material that can bond to both thermoplastic and non-liquefiable materials, creating a composite bonding interface. This allows the blind rivet assembly to function as a multi-material bonding system that overcomes the limitations of single-material adhesive bonds.

Inventive Principle:
Principle #40Composite materials

2Adaptability or versatility

If adhesive bonds are used to connect surfaces with roughness, then bonding capability is maintained, but manufacturing efficiency deteriorates due to slow hardening processes and increased material costs

Engineering Contradiction:
Improvebonding capabilityVSAvoidmanufacturing efficiency
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent replaces the chemical adhesive bonding process with a mechanical bonding process using a blind rivet and bonding element. This mechanical system provides immediate bonding capability without the slow hardening times associated with adhesives, significantly improving manufacturing efficiency while maintaining the ability to bond rough surfaces through the mechanical deformation and securing mechanisms of the rivet system.

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

3Strength

If mechanical bonds such as screws and rivets are used to connect large parts, then bonding strength is improved, but manufacturing precision deteriorates due to difficulty in precisely defining relative locations of fasteners and fastening locations

Engineering Contradiction:
Improvebonding strengthVSAvoidfastener positioning precision
Core Design Contradiction:
StrengthVSManufacturing precision

Solution Approach 1:

The patent extracts the positioning function from the fastener itself by providing separate positioning elements on the bonding element that engage with corresponding features on the thermoplastic part. This separation allows the bonding element to be precisely positioned independently of the fastening location, solving the precision problem while maintaining mechanical bonding strength.

Inventive Principle:
Principle #2Taking out (Extraction)

4Adaptability or versatility

If adhesive bonds are used for bonding lightweight materials, then bonding capability between different materials is improved, but weight of the bonding system deteriorates due to additional material and process requirements

Engineering Contradiction:
Improvebonding capabilityVSAvoidbonding system weight
Core Design Contradiction:
Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The patent replaces the multi-component adhesive bonding system with a single blind rivet assembly that integrates the bonding function. This eliminates the need for separate adhesives, primers, and complex application equipment, thereby reducing the overall weight of the bonding system while maintaining the capability to bond lightweight materials like aluminum and magnesium.

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 method provides a strong, reliable, and cost-effective connection between thermoplastic and non-liquefiable materials, effectively addressing the limitations of adhesive bonds and thermal expansion issues, while reducing axial joining forces and enhancing bonding quality.

Implementation Method 1

a melting zone comprising flowable thermoplastic material is formed and such that thermoplastic material of the melting zone flows around the edge to at least partially embed the edge in the thermoplastic material. Said melting zone is formed due to friction heat generated between the edge and the thermoplastic material that move relative to each other

Methodology Applied
Scientific EffectFriction heat: Friction

Implementation Method 2

bringing the first object and the second object to a relative movement to each other such that a melting zone comprising flowable thermoplastic material is formed and such that thermoplastic material of the melting zone flows around the edge to at least partially embed the edge in the thermoplastic material

Methodology Applied
Scientific EffectFriction welding: Friction Welding

Data Source

PatentEP3606729B1Bonding objects together
Publication Date: 2023.09.13 WOODWELDING AG
  • EP3606729B1 patent drawingFigure 1a~1d
  • EP3606729B1 patent drawingFigure 2a~3c
  • EP3606729B1 patent drawingFigure 4a~6b

AI summary

The invention is in the fields of mechanical engineering and construction, especially mechanical construction, for example automotive engineering, aircraft construction, railway industry, shipbuilding, machine construction, toy construction and building industries. It relates to a method of - mechanically - securing a first object (1) to a second object (2). The method comprises the steps of: providing the first object (1) comprising thermoplastic material (3) in a solid state, providing the second object (2) with a generally flat sheet portion having an edge (21), positioning the first object (1) relative to the second object (2) and bringing the first object (1) and the second object (2) to a relative movement to each other, said relative movement comprising a rotational movement, such that a melting zone (13) comprising flowable thermoplastic material is formed and such that thermoplastic material of the melting zone (13) flows around the edge (21) to at least partially embed the edge (21) in the thermoplastic material. The invention further concerns a connector that is suitable for being used in a method according to the invention.