Metal-Polymer Joining with Offset Extrusion Hook Interlocking

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Solution Overview

Problem

Current hybrid joining techniques fail to achieve strong and chemically stable connections between dissimilar materials like aluminium alloys and polymer-based components, particularly in high-performance industries such as aeronautics and automotive, due to their differing physical natures, leading to limitations in lightweight design and environmental compliance.

Innovation Solution

The THE-FSpW process uses a thin, non-consumable extrusion die plate with through-holes between overlapping metal and polymer components, where a rotating tool extrudes metal into the polymer under high pressure and temperature, activating adhesive, diffusion, and clinging mechanisms, producing a non-axis-symmetrical high volume hook for enhanced mechanical strength and resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional mechanical fastening or adhesive bonding is used to join metal and polymer components, then the joining process is simple and well-established, but the connection strength and chemical stability are insufficient for high-performance applications

Engineering Contradiction:
Improveconnection strengthVSAvoidjoining process complexity
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The invention changes the physical parameters of the metal component by locally heating it to elevated temperatures (but below melting point) and applying high pressure, transforming the metal's mechanical properties to enable plastic deformation and intimate contact with the polymer surface, thereby creating strong mechanical interlocking and potential chemical bonding

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The invention replaces conventional mechanical fastening (screws, rivets) or adhesive bonding systems with a direct thermomechanical joining process where heated metal is pressed into the polymer, eliminating the need for separate fasteners or adhesives while achieving superior connection strength

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

2Strength

If friction riveting or friction spot joining is used to join polymer to metal, then pre-joining operations are avoided, but the joints have low resistance to torsion and peeling loads

Engineering Contradiction:
Improveresistance to peeling and torsionVSAvoidjoint geometry complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The invention creates an asymmetric joint geometry where the metal component is locally deformed to form an irregular, non-uniform interface with the polymer, concentrating material displacement and interlocking features in specific zones that provide superior resistance to peeling and torsional loads compared to symmetric friction-welded joints

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The invention transitions from surface-level friction welding to a three-dimensional joining process where metal material is displaced and embedded into the polymer substrate, creating depth-based mechanical interlocking that enhances resistance to separation and torsional forces

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

3Strength

If multiple spot welds are used to achieve sufficient structural strength, then the joint reliability increases, but the productivity decreases due to longer processing time

Engineering Contradiction:
Improvestructural strengthVSAvoidprocessing speed
Core Design Contradiction:
StrengthVSProductivity

Solution Approach 1:

The invention merges multiple discrete spot weld operations into a single continuous processing pass, where the tool moves along a predefined path and creates a series of interconnected joints in one operation, thereby maintaining high structural strength while significantly improving productivity

Inventive Principle:
Principle #5Merging (Combining)

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 process provides joints with superior mechanical strength, resistance to peeling, and torsion loading, reducing the number of spot welds required, enhancing productivity, and enabling the use of lighter, more environmentally friendly structural components.

Implementation Method 1

Friction Spot Joining (FSpJ). This technique is used also to join polymer/composite to metal, where frictional heat is generated on one of the metallic sheet surfaces

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 2

by generating a multi-polymer matrix that results e.g. from the local melting of the polymeric materials

Methodology Applied
Scientific EffectMelting: Melting

Implementation Method 3

The extrusion die plate has one, or more, through-holes, that will serve to extrude the part of the metal component that will be pushed through the hole into the polymer component

Methodology Applied
Scientific EffectExtrusion: Extrusion

Implementation Method 4

Adhesive, diffusion and clinging joining mechanisms are thus activated between the metal component and the polymer component

Methodology Applied
Scientific EffectDiffusion: Diffusion

Implementation Method 5

Adhesive, diffusion and clinging joining mechanisms are thus activated between the metal component and the polymer component

Methodology Applied
Scientific EffectAdhesive: Adhesive

Data Source

PatentEP3645251B1Method for joining a metal component and a polymer component, and structure comprising said components
Publication Date: 2022.11.23 AALTO UNIV FOUND
  • EP3645251B1 patent drawingFigure 1
  • EP3645251B1 patent drawingFigure 2~3
  • EP3645251B1 patent drawingFigure 4~5

AI summary

The invention concerns a method for joining a metal component (1) and a polymer component (2), and a structure comprising said components. In the method, an extrusion die plate (3) with a through hole (4) is placed between the metal component (1) and the polymer component (2). A probe(5a) is rotated and plunged across the thickness of the metal component(1) and eventually through said through hole (4) of the extrusion die plate(3), thereby extruding a part of the metal component (1) through said through hole (4) of the extrusion die plate (3) into the polymer component(2). The probe (5a) has a rotation axis having an offset to the centre of the through hole (4) during the rotating and plunging action.