FP7 Research Project MetalMorphosis · Optimization of joining processes for new automotive metal-composite hybrid parts . ... –increased use of composites in the automotive industry

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FP7 Research Project MetalMorphosis Optimization of joining processes for new automotive metal-composite hybrid parts

Joining of tubular metal-composite parts using the electromagnetic pulse technology Workshop

Koen Faes

Irene Kwee

Belgian Welding Institute

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MetalMorphosis - Motivation Motivation:

– increased use of composites in the automotive industry for weight reduction, – development of a cost-effective joining method for metals and composites

Use of the electromagnetic pulse technology: Extension of the application range towards joining of metals and composites

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Electromagnetic pulse techn.: Process principles

Coil

Field shaper

Workpiece

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Process principles : Variants

Welding Crimping

interference and form fit joints

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Variant : Electromagnetic pulse welding

Copper - Steel

Copper - Stainless steel

Aluminium - Aluminium

Copper - Brass

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Variant : Electromagnetic pulse crimping

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Joining concepts for tubular products

Interference fit joints: – Concept 1 : Connection of a metal tube with a solid composite part – Concept 2 : Connection of a metal tube with a tubular composite part

Form fit joints: – Concept 3 : Connection of a metal tube with a profiled solid composite part : single groove – Concept 4 : Connection of a metal tube with a profiled solid composite part : double groove – Concept 5 : Connection of a metal tube with a solid or tubular composite part – Concept 6 : Connection of a solid or tubular metal part with a tubular composite part, using an

external ring – Concept 7 : Connection of a metal tube with a solid composite part, with a single groove & insert – Concept 8 : Connection of a metal-composite hybrid part with another metal part – Concept 9 : Connection of a metal tube with a solid composite part, with a double groove & insert

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Joining concepts for tubular products Interference fit joints: the outer tubular part is deformed plastically and the internal part

deforms elastically

Concept 1 : Connection of a metal tube with a solid composite part

Concept 2 : Connection of a metal tube with a tubular composite part Composite tube supported by an insert placed inside the tube

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Joining concepts Form fit joints: undercuts (e.g. grooves) are used in the internal part and the other tube is

deformed into these undercuts, creating a mechanical interlock

Concept 3 : Connection of a metal tube with a profiled solid composite part : single groove

Concept 4 : Connection of a metal tube with a profiled solid composite part : double grooves

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Joining concepts Concept 5 : Connection of a metal tube with a solid or tubular composite part

Metal tube foreseen with a grooved internal surface, e.g. an internal screw thread or an internal knurled surface

Composite tube internally supported by an insert

Concept 6 : Connection of a solid or tubular metal part with a tubular composite part, using an external ring Similar as concept 5, but in addition the metal bar is foreseen with a profiled outer surface

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Joining concepts Concept 7 : Connection of a metal tube with a solid composite part, with a single groove

and metal insert

Concept 9 : Connection of a metal tube with a solid composite part, with a double groove and metal insert

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Joining concepts Concept 8 : Connection of a metal-composite hybrid part with another metal part

Possibilities for the manufacturing of hybrid parts

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Materials Metal tube material :

– Aluminium: EN AW-6082 T6 (40 x 2 mm) – Steel: E235+C (38,7 x 1,42 mm)

Composite bar & tube material :

Composite – short name

Description Shape

PA6.6 - GF30 Polyamide 66 + 30% glass fibers Bar & tube

Akulon K224 - PG8 or PA6-GF50

Polyamide 6 + 50% glass fibers, heat stabilized, high flow (manufactured by injection moulding)

Bar

EP GC 22 (EN 61212)

Glass fabric tubes with epoxy DIN 7735 HGW 2375.4

Tube

EP GC 203 Epoxy-resin glass reincorced laminate Bar

GE

Epoxy resin reinforced with continuous glass fibres (manufactured by Resin Transfer Moulding - RTM)

Tube

CE Epoxy resin reinforced with continuous carbon fibres (manufactured by Resin Transfer Moulding – RTM)

Bar

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Overview joining concepts & composites

Metal tube

Composite

Concept 1

(bar)

Concept 2

(tube)

Concept 3

(bar/tube)

Concept 4

(bar/tube)

Concept 5

(bar/tube)

Concept 7

(bar)

Concept 9

(bar)

Alum

iniu

m

6082

PA6.6GF30 x x x x x x x

EP GC22 x x x x

EP GC203 x

Glass reinforced epoxy x x x

Carbon reinforced epoxy x x x

Akulon K224-PG8 x

Stee

l E2

35+C

Akulon K224-PG8

x

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Concept 1 – Interference fit Tensile force & impact resistance:

– Joint strength of PA6.6 and CE is comparable and low (1 – 4 kN)

– Medium impact resistance : allowed energy levels up to 8 kJ without composite fracture

Higher tensile force for a larger gap – But: a too large gap between tube and composite

part should be avoided because of composite fracture

Avoid aluminium tube wrinkling by selecting a sufficiently high discharge energy

– But: a too high energy level induces cracks in the composite

Joint of aluminium & carbon reinforced epoxy

Joint of aluminium & PA6.GF30

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Concept 5 – Internal screw thread in metal Joints with low to medium strength

(0 - 18kN)

Higher strength compared to concept 1 & 2

No fracture of the aluminium tube (tube slides off)

Tensile strength increases for: – A higher discharge energy – A larger gap between aluminium tube and

composite part – When the screw thread creates indentations in

the composite part

Joint of aluminium & PA6.GF30

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Concept 3 – Single groove, without insert Connection of a metal tube with a profiled composite tube : single groove

Composite tube : Akulon K224-PG

Metal tubes : – Aluminium 6082 – Steel E235 +C

Parameter variation: – Groove geometry = constant – Composite tube inner diameter – Discharge energy

Akulon K224-PG tubes

Test series

Inner diameter (mm)

Groove radius (mm)

Groove depth (mm)

Groove width (mm)

1 13 2 3,5 14

2 17 2 3,5 14

3 21 2 3,5 14

Joint of Akulon & aluminium Joint of Akulon & steel

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Concept 3 - Akulon & aluminium Composite specimen fracture behaviour

Smallest composite inner diameter (13 mm) : highest impact resistance

For all composite inner diameters : no plastic deformation at the groove

Increase of energy ⇒ increase of number of cracks in composite

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Concept 3 - Akulon & aluminium Tensile strength

Composites with inner diameter 13 and 17 mm : similar tensile forces

Composites with inner diameter 21 mm : significant lower tensile forces

All composite inner diameters:

– similar tube fracture mode & no composite fracture

– Increase of discharge energy ⇒ increase of tensile force & fracture magnitude

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Concept 3 - Akulon & aluminium Tensile test: 3 fracture modes of the aluminium tube, no composite fracture

Small longitudinal

fracture +

No circumferential fracture

Medium longitudinal fracture

+ Small circumferential

fracture

Large longitudinal fracture

+ Medium circumferential

fracture 22,7 kN at 7 kJ 27,1 kN at 8 kJ 31,1 kN at 10 kJ

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Composite specimen fracture behaviour

For all composite inner diameters: similar impact resistance

At higher discharge energy: plastic deformation at groove bottom and groove edges, due to thermal effects of steel tube

Concept 3 - Akulon & steel

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Concept 3 - Akulon & steel Tensile strength

Steel tube : no fracture, only expansion of steel tube

Composite : 3 different fracture modes, depending on composite inner diameter and discharge energy:

– No composite fracture – Composite fracture outside

groove zone – Composite fracture at

plastically deformed groove bottom

– Increase in energy ⇒ increase in tensile force

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Tensile test: 3 fracture modes

No steel tube fracture

+ No composite fracture

No steel tube fracture +

Composite fracture outside groove zone

No steel tube fracture +

Composite fracture at plastically deformed

groove bottom 23,2 kN at 14 kJ 36,7 kN at 18 kJ 33,4 kN at 18 kJ

Concept 3 - Akulon & steel

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Tensile force comparison

Joints with alu tubes – Lower tensile forces

than steel tubes – Alu tube fracture – No composite fracture

Joints with steel tubes – Higher tensile forces

than alu tubes – No steel tube fracture – Composite fracture

outside groove zone and at plastically deformed groove bottom

Concept 3 - Akulon & aluminium vs. Akulon & steel

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Concept 4 – Double groove, without insert Connection of a metal tube with a profiled solid composite part: double groove

Composite materials : – PA6.6 GF30 bars – GC22 tubes – GE tubes

Aluminium tubes

Parameter variation: – Groove edge radius: 1 & 2 mm – Discharge energy

Joint of GC22 & aluminium

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Composite fracture behaviour

Concept 4 – GE & aluminium

No cracks nor degradation of composite

Cracks in the composite core or degradation at the groove edge or at the outer surface of the composite

Observations :

Increase of discharge energy ⇒ increase of degradation

Lack of correlation between the groove geometry and fracture behaviour

Joint of GE & alu

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Tensile test: 4 fracture modes for joints of GE glass reinforced epoxy & aluminium

Concept 4 – GE & aluminium

< 43 kN

- Aluminium tube slides off, without fracture - No composite fracture - For majority of the joints

- Aluminium tube slides off, without fracture - Composite fracture

> 43 kN

- Aluminium tube fractures in the longitudinal direction - No composite fracture - For majority of the joints

- Aluminium tube fractures in the circumferential direction

- No composite fracture

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Comparison: range of tensile forces and corresponding discharge energies

Concept 4 – Double groove, without insert

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Concept 3 (single) vs. Concept 4 (double groove) Comparison: range of tensile forces and corresponding discharge energies

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Concept 7 – Single groove, with insert In general:

– Comparable joint strengths (21 – 44 kN) – Impact resistance of PA6.6 is higher (up

to 13 kJ) compared to GC203 (up to 11 kJ)

– Different fracture modes

Higher tensile strength for: – A smaller groove edge radius

(0,75 mm - 1 mm) – A larger groove & insert edge angle

(θ = 90°) At a higher energy for GC203, but at lower energy for PA6.6

A higher impact resistance for: – A large groove depth (2,5 mm) ⇒ prevents aluminium tube from

impacting on the groove bottom – A larger insert edge angle (90°) ⇒ avoids tensile forces induced by the

inwards movement of tube

Joint of PA6.6GF30 & alu Joint of EP GC203 & alu

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Concept 9 – Double groove, with insert Connection of a metal tube with a profiled solid composite part: double groove, with insert

Composite material : PA6.6GF30 bars

Aluminium 6082 tubes

Parameter variation: – Discharge energy – Groove edge radius: 1 & 2 mm

Impact resistance: – Allowable energy levels up to 14 kJ – No effect of the groove radius on the impact resistance

Tensile force: – Range 51 – 53 kN – Lack of correlation between groove edge radii and tensile force

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Comparison: range of tensile force and corresponding discharge energies

Concept 4 (double groove & without insert) & vs. Concept 9 (double groove & with insert)

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Comparison: range of tensile forces and corresponding discharge energies

Concepts 3 vs. 4 vs. 7 vs. 9 for joints of PA6.6GF30 & aluminium

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Joining concepts: – Form fit joints provide a higher tensile force than interference fit joints – Joining concepts with a double groove (concept 4) or with an insert wit a double groove (concept 9) provides the

highest tensile force and impact resistance, due to: Mechanical interlock of the tube into the grooves or inserts of the composite Larger distance for the tube to cover prior impact onto the composite Metal insert protects the composite against the impacting tube

Composites: – EP GC22 with double groove & without insert: high impact resistance (11 kJ) & highest tensile force (57-65 kN) – PA6.6GF30 with double groove & with insert: highest impact resistance (14 kJ) & high tensile force (51-53 kN)

Metal tubes: – Steel:

Higher tensile force and higher impact resistance, But: higher energy for crimping and composite fracture during tensile testing

– Aluminium: Lower tensile force and lower impact resistance, But: lower energy for crimping and aluminium fracture during tensile testing

Conclusions

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This project is performed within the 7th Framwork Progamme funded European Research and Technological Development

Contact: Belgian Welding Institute Dr. ir. Koen Faes [email protected] +32(0)9/292.14.00

mailto:[email protected]

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FP7 Research Project MetalMorphosis · Optimization of joining processes for new automotive metal-composite hybrid parts . ... –increased use of composites in the automotive industry