PROCESS-ROBUST STRUCTURAL ADHESIVES AND THEIR IMPLEMENTATION IN VEHICLE MANUFACTURING

Transcription

1 PROCESS-ROBUST STRUCTURAL ADHESIVES AND THEIR IMPLEMENTATION IN VEHICLE MANUFACTURING Fügen im Karosseriebau, Automotive Circle International, April 2012 Fiorenza Di Sciullo, Dr. Andreas Lutz FIAT Centro Ricerche, IT Research&Development, Adhesives, Dow Europe GmbH, Switzerland,

2 Content Why use structural adhesives Formulation and toughening principles New BETAMATE S-Technology: process robust adhesive technology Outlook: Outlook: - 2 Part body shop and high Tg adhesives - Composite adhesive bonding concept

3 Market Drivers and Benefits Increased static stiffness to 20% Durability & Driving Comfort Increased dynamic stiffness: 2-3Hz Acoustic Comfort BETAMATE Structural Adhesives Benefits Increased energy management capability Safety Weight reduction High strength steel usage Panel thickness reduction Multi material design Environment Cost down capabilities Weld spot reduction up to 50% Metal content reduction up to 10kg/vehicle Process speed improvement of between 50 & 100% Savings STRUCTURAL ADHESIVES GENERAL INFORMATION

4 Why using toughened structural adhesives? Reduction of stress concentrations Improved fatigue durability Carrying higher loads Reduction of steel thicknesses Adhesive Spot weld (5 mm) Stress concentration Continuous stress distribution

5 Fatique Durability Fatigue strength in dependence of the metal yield point: The use of CDA Bonding increases the fatigue strength amplitude by a factor of three! no significant metal dependence! 4 DC05 ZStE340 Trip800 fatique strength Dauerfestigkeit F A, [kn] (P A =50% %) 3,5 3 2,5 2 1,5 1 0,5 0 CL H180Y SN PS Laser Step CLK SNK PSK Kleben Laser I-Naht DP500 CDA Bonding + traditional joining methods traditional joining methods Zugfestigkeit Fügeteilwerkstoff [MPa] Yield point of the metal

6 Corrosion Durability driver side passenger side red line location of weld-bond line Specimen cut out of the body structure. Strength decrease and failure mode tested BMW 745i with 107,000 miles (172,000 km) ~ 15 mm bond line direction gage section ~ 7.5 mm spot welds slots cut into specimen Adhesive (blue)

7 Results Lap shear strength No significant loss of shear strength Failure mode slightly shifted from cohesively to surface close cohesive failure Strength 17.5 Energy Driver Side Shear Strength (MPa) Absorbed Energy (N*mm/mm^2) original rebonded Adhesive State All Pairs Tukey-Kramer original rebonded Adhesive State All Pairs Tukey-Kramer 0.05 Strength Energy Passenger Side Shear Strength (MPa) Absorbed Energy (N*mm/mm^2) original Adhesive State rebonded All Pairs Tukey-Kramer 0.05 original Adhesive State rebonded All Pairs Tukey-Kramer 0.05

8 Chemical Building Blocks Epoxy resins Bis-A/F-epoxy resins Filler Mechanical strength Adhesion perfomance Cost composition Paticle size and distribution shape Viscosity Corrosion resistance Crosslinking density Epoxy resin examples CaO CaCO3 TiO2 Aluminium-magnesium-sulfates Filler Hardener Toughener Curing accelerator

9 Toughening Principle Force Substrate Adhesive Toughener Substrate Shear banding Crack deflection Cavitation Force

10 Adhesive Bulk Stability BETAMATETM-S-Technology Only minimal increase of viscosity over time and over a wider temperature range: Below 30 C 9-12 months Between 40 and 60 C: 3-6 months

11 BETAMATE S Validation Application Performance Substantial Process Advantages due to improved rheological behaviour 1) 2) 3) Reducing dozer filling time Decreasing application pressure Lower application temperature Reducing cycle time Energy/cost saving Energy/cost saving - 13bar pressure - 30s doser filling time - 10 C temperature Verification after 6 Months Storage Time Significantly reduced pressure compared to reference material 55 C 55 C 55 C 55 C 45 C 35 C 3 bar 5 bar 3 bar 5 bar 5 bar 5bar Reference S generation Reduced material temperature Application pressure Material pressure Dozer filling time No change in dozer filling time after 6 months 55 C nozzle temp No significant change in dozer filling time after 6 months storage: Higher cycle time for customer 55 C 45 C 35 C nozzle temp Significantly higher process stability

12 Adhesive Application The bulk stability combined with lower initial viscosity favors the use of modern application methods like stitch or jet stream application.

13 2K Epoxy Adhesive Technology Two part toughened epoxy structural adhesive technology which pre-cures already at temperatures below 140 C and above 110 C to reduce thermal stress in the part. Oil absorbance even at rt curing achieved under specific pre-conditions. Lap shear strength above 15 MPa Impact peel strength above 20 N/mm Good corrosion resistance Fast curing with induction at about 130 C source: SCA Schucker, Static application of a two part structural adhesive Cool down to rt After 60s

14 High Tg and toughened Structural Adhesives Improve tolerance regarding adhesion failure through relative displacement under thermal stress E.g. during cool down phase after e-coat oven delayed curing in e-coat oven T > 135 C feasable Betamate 1020S.110 G' G'' 0.6 tan_delta 1.00E E E E E temperature in C tan delta G' and G'' in Pa E+08

15 BETAMATETM Flex 1K-Epoxy Adhesive Development Grade Warm applied in Body Shop / no special equipment needed Cures at elevated in E-Coat oradhesive Paint Ovens BETAMATE 2-PartT Structural Application targets: Multi Material Designs (Different CLTE s) Hem flange bonding to prevent part distortion due to flexural modulus Structural joints for Steel/Aluminum to CFC CFC/Steel CFC/CFC STRUCTURAL ADHESIVES PRODUCTS

16 BETAMATETM Flex Mechanical Characteristics in comparison BETAMATE 2-Part Structural Adhesive E-Modulus: Tensile Strength: Lap Shear Strength: Elongation at Break: Impact Peel Strength: STRUCTURAL ADHESIVES PRODUCTS BM-Flex BM 1496F 400 MPa 10 MPa 20 MPa 40% 48 N/mm 1400 MPa 33 MPa 31 MPa 16% 60 N/mm

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