© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum DRY CLEANING AND PRETREATMENT OF ALUMINUM SHEETS USING HIGH-RATE LASER PROCESSING Annett Klotzbach, Tom Schiefer, Robert Kühne, Jens Standfuß Fraunhofer Institut für Werkstoff- und Strahltechnik Dresden
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
DRY CLEANING AND PRETREATMENT OF ALUMINUM SHEETS USING HIGH-RATE LASER PROCESSING
Annett Klotzbach, Tom Schiefer, Robert Kühne, Jens Standfuß
Fraunhofer Institut für Werkstoff- und Strahltechnik Dresden
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
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Fraunhofer IWS Dresden Application-adapted research for industry and society
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
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Fraunhofer IWS Dresden Working group: Bonding and Composite technology
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
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AGENDA
Fiber metal laminate / GLARE processing
Requirements for pretreatment
Process overview
Pretreatment by laser
Results of mechanical testing
Conclusion © fokker.com
© CTC Staade
Dry cleaning and pretreatment of aluminum sheets using high-rate laser processing
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Fiber metal laminates (FML)
GLARE®
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Glass fiber reinforced aluminum (GLARE)
Aluminum sheets (AA2024), 0.3 mm – 0.4 mm
uni-directional S-glass fiber prepreg + epoxy resign 0.13 mm
Fiber orientation based on loading condition
Schematic image of splice
Cross section
©: theatlasgroup.biz
GLARE - Advantages
Density of GLARE approx. 10% lower than monolithic aluminum
High corrosion stability
Corrosion attack will be limited by prepreg layer
Higher damage resistance
Higher fatigue properties based on reduced crack growing
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
GLARE production steps
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-> Lay-up (manually)
Coil delivery ->
Source: Fokker
Part cutting by milling-> PSA-treatment -> Primer-coating ->
-> Autoclav -> Finished GLARE part
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Requirements for surface pretreatments
SOA
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Phosphoric acid anodizing
State of the art pretreatment:
4-step wet-chemical pretreatment
Cleaning, etching, anodizing, primering
Specific surface (~4 µm ablation), defined oxide layer
Treatment time, human safety, costs, environment protection, legal requirements
Requirement:
Pretreatment with dry (physical ) processes
Active (oxide layer) and passive (adhesion) corrosion resistance
Production factors (automation, time in m²/min, costs, safety)
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Laser pretreatment
Principle
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Pulsed laser ablation
Interaction of light energy and part surface
Material melting, vaporizing and/or ablation
Material and wavelength specific interaction
Removal of layer thicknesses up to some 100 µm
Laser processes realize:
surface cleaning (removal of oil, dust, paint, rust,…)
Surface enlargement (topography change)
Surface activation (new oxide layer)
Treatment of points, lines, areas, contours (easy to automate)
Process productivity is determined by average laser power
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Laser pretreatment from PRECISE to PRODUCTIVE
Laser setups
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2D - pulsed laser ablation
ns - laser vscan: 5 m/s typical, Plav.: up to 500 W
2D - cw laser processing
cw - laser vscan: 15 m/s typical, Plav.: up to 3 kW
cw - laser vscan: 300 m/s typical, Plav.: up to 5 kW
1D - cw laser processing (R2R)
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
R2R laser pretreatment
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Principle
Combination of „laser beam scanning“ and „laser beam switching“
Proven technology: laser treatment of electrical ferritic sheets („laser magnetic domain refinement“)
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
R2R laser pretreatment
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Experimental setup
quick 1D-beam deflection (up to 300 m/s)
continuous material movement (up to 80 m/min)
Programmable line distance and length
Modified laboratory system
Parameter
Wavelength 1070 nm
Laser power 2000 - 5000 W
Scan speed up to 300 m/s
Fokus diameter ellipse (a = 18 µm, b= 460 µm)
Step-by-step material transport
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Structuring results@AA2024uc, 0.3 mm thickness
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Results
Parameter setup
P = 5000 W
Scan speed: v = 150 - 300 m/s
Line distance: 50 µm
Results
Line width: 28 - 41 µm
Ablation depth: 8 – 15 µm
500 µm
Complete line processing with artificial oxide layer
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Structuring results@AA2024uc, 0.3 mm thickness
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Enlargement of oxide layer thickness
Results
Parameter setup
P = 5000 W
Scan speed: v = 150 - 300 m/s
Line distance: 50 µm
Results
Line width: 28 - 41 µm
Ablation depth: 8 – 15 µm
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Testing of adhesion properties
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Adhesion tests
Pk. Pretreatment Primer B Non treated --- LM Solvent Yes TSA Wine-sulfur-anodizing Yes pw1 pw-Yb:YAG (fiber laser) Yes pw2 pw-Nd:YAG (rod laser) Yes cw1 1D-cw-Remote Yes cw2 1D-cw-Remote yes
Cross section tensile test specimen
Tensile shear test specimens (DIN EN 2243-1) thickening on both sides
Peel test specimen (DIN EN 2243-2)
Material: AA2024 uc ; 0.3 mm
Adhesive: GF-Epoxy resin
Primer: Cr(VI) - Primer
Thickening: 1.6 mm
Thickening: 1.6 mm
Pre-treated
foils
Autoclav - run
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Testing of adhesion properties
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LM (adhesion) TSA (cohesion) cw1 (cohesion)
0
5
10
15
20
25
30
35
40
45
50
B LM TSA PSA* pw1 pw2 cw1 cw2
Ten
sile
sh
ear
stre
ng
th
[MPa
] *) PSA-reference AA2024 unclad
Adhesion tests
Tensile shear test specimens (DIN EN 2243-1) thickening on both sides
Peel test specimen (DIN EN 2243-2)
Material: AA2024 uc ; 0.3 mm
Adhesive: GF-Epoxy resin
Primer: Cr(VI) - Primer
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Testing of adhesion properties
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0123456789
10
B LM TSA PSA* pw1 pw2 cw1 cw2
Peel
res
ista
nce
[N
/mm
] comparison (cw1- TSA)
cw1 (cohesion)
TSA (adhesive failure between AA2024/Primer)
Adhesion tests
Tensile shear test specimens (DIN EN 2243-1) thickening on both sides
Peel test specimen (DIN EN 2243-2)
Material: AA2024 uc ; 0.3 mm
Adhesive: GF-Epoxy resin
Primer: Cr(VI) - Primer *) PSA-reference AA2024 unclad
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Comparison of processes
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Comparison
© Fraunhofer IFAM
Treatment Lap Shear [MPa]
Peel Test [N mm-1]
FFT 2nd-6th fil. / mm
SST 3000h 3)
2nd -6th del. / mm
Requirements 30 7.21) 2 1.25
Laser 375) 7.85) 1.75) 0.2
Plasma 355)/256) 2 > 56) >> 2
Anodising tape
315)/306) 4.25)/7.26) 1.4 – 4.86, 2) 0.5.. > 3.02)
PSA 315)/366) 9.55)/8.76) 0.75)/1.06) 0.5
1) IPS 10-01-008-01 issue 3 (Structural adhesive film for GLARE application FM94K.06) 2) Depending on surface treatment 3) AA2024 uc, chromate loaded coating system 5) AA2024 uc 6) AA2024 c
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Fatigue and damage tolerance properties
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Fatigue testing
Fatigue crack initiation life
Crack propagation
Residue strength as function of fatigue damage
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Fatigue and damage tolerance properties
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Fatigue testing
Fatigue crack initiation life
Crack propagation
Residue strength as function of fatigue damage
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Conclusion - Outlook
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Conclusion
Processes can fulfill the adhesion requirements (strength, FFT, SST)
Material removal is needed for good adhesion and corrosion behavior
Good fatigue properties
Processing speeds of up to 1 m²/min possible
SOA
Laser treatment R2R
© Fraunhofer IWS KLZ: 22.10.2019 P2C - Forum
Conclusion - Outlook
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Conclusion
Processes can fulfill the adhesion requirements (strength, FFT, SST)
Material removal is needed for good adhesion and corrosion behavior
Good fatigue properties
Processing speeds of up to 1 m²/min possible
The presented work was funded within the aviation research project „AUTOGLARE“ (FKZ: 20W1517D), leading by AIRBUS.
Annett Klotzbach
Mobile: +49 1722414077