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 Page 0
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 Page 1
Electromagnetic pulse techn.: Process principles Coil Field shaper Workpiece Page 2
Process principles : Variants Welding Crimping interference and form fit joints Page 3
Variant : Electromagnetic pulse welding Copper - Brass Copper - Steel Copper - Stainless steel Aluminium - Aluminium Page 4
Variant : Electromagnetic pulse crimping Page 5
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 Page 6
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 Page 7
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 Page 8
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 Page 9
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 Page 10
Joining concepts Concept 8 : Connection of a metal-composite hybrid part with another metal part Possibilities for the manufacturing of hybrid parts Page 11
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 EP GC 22 (EN 61212) Polyamide 6 + 50% glass fibers, heat stabilized, high flow (manufactured by injection moulding) Glass fabric tubes with epoxy DIN 7735 HGW 2375.4 Bar Tube EP GC 203 Epoxy-resin glass reincorced laminate Bar GE CE Epoxy resin reinforced with continuous glass fibres (manufactured by Resin Transfer Moulding - RTM) Epoxy resin reinforced with continuous carbon fibres (manufactured by Resin Transfer Moulding RTM) Tube Bar Page 12
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) Aluminium 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 Steel E235+C Akulon K224-PG8 x Page 13
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 Joint of aluminium & PA6.GF30 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 Page 14
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) Joint of aluminium & PA6.GF30 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 Page 15
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 Test series Akulon K224-PG tubes Inner diamete r (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 Page 16
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 Page 17
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 Page 18
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 Page 19
Concept 3 - Akulon & steel 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 Page 20
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 Page 21
Concept 3 - Akulon & steel 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 Page 22
Concept 3 - Akulon & aluminium vs. Akulon & steel 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 Page 23
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 Joint of GC22 & aluminium Aluminium tubes Parameter variation: Groove edge radius: 1 & 2 mm Discharge energy Page 24
Concept 4 GE & aluminium Composite fracture behaviour Joint of GE & alu 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 Page 25
Concept 4 GE & aluminium Tensile test: 4 fracture modes for joints of GE glass reinforced epoxy & 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 Page 26
Concept 4 Double groove, without insert Comparison: range of tensile forces and corresponding discharge energies Page 27
Concept 3 (single) vs. Concept 4 (double groove) Comparison: range of tensile forces and corresponding discharge energies Page 28
Concept 7 Single groove, with insert Joint of PA6.6GF30 & alu Joint of EP GC203 & alu 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 Page 29
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 Page 30
Concept 4 (double groove & without insert) & vs. Concept 9 (double groove & with insert) Comparison: range of tensile force and corresponding discharge energies Page 31
Concepts 3 vs. 4 vs. 7 vs. 9 for joints of PA6.6GF30 & aluminium Comparison: range of tensile forces and corresponding discharge energies Page 32
Conclusions 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 Page 33
This project is performed within the 7th Framwork Progamme funded European Research and Technological Development Contact: Belgian Welding Institute Dr. ir. Koen Faes Koen.Faes@bil-ibs.be +32(0)9/292.14.00 Page 34