5th International CFK-Valley Stade Convention 7. 8. June 2011, Stadeum Stade, Germany A. Dietz, G. Klumpp, H.-J- Kramer Fraunhofer IST, Braunschweig C. Haas Astrium GmbH Friedrichshafen
Overview GMES - Sentinel Fundamentals of Plastic Metallisation Metallisation of Waveguides Quality Management Conclusions
Sentinel GMES: Computer simulation of Sentinel 1 in LEO (Low Earth Orbit; 200 2,000 km above earth surface)
ESA-Mission GMES/Sentinel GMES - Global Monitoring for Environment and Security Sea ice & iceberg monitoring Global fire Oil pollution monitoring Active seismic zone and volcano observatory Forest Monitoring for Kyoto implementation Global Biosphere Monitoring
GMES/Sentinel SAR Synthetic Aperture Radar - Waveguide C-Band SAR with centre frequency of 5.405 GHz Waveguides Antennas in the frequency range of > 1000MHz Metallic or metal coated tubes in a round, elliptic or rectangular form The Wave length determines the dimension of the waveguides Scheme of the Sentinel 1 waveguide array
GMES/Sentinel Challenges of the plastic metallisation Hydrophobic surface no wetting Electrically insulating surface no direct metallisation Different atomistic properties between plastic substrate and metallic coating bad adhesion
Comparison: Electrodeposition on metal substrates Benefits Electrical conductivity of the substrate Coating and substrate are quite similar concerning physical and chemical properties Diffusion of coating and substrate improve the adhesion Problems Passivation of very unnoble substrate metals like Titanium, Aluminium
Metal deposition on plastics Wetting theory Push button effect Non-wetted surface Metal Wetted surface Plastic Etched plastic surface
Homogeneous deposition on complex geometries Dog bone effect due to the streamlines of field Homogeneous deposition by means of auxiliary anodes
GMES/Sentinel Dimension: VP: Length: 870mm; Width: 20mm; Height: 20mm HP: Length: 870mm; Width: 40mm; Height: 18mm Challenges of the CFRP metallisation Defect free coating outside and inside Very good adhesion due to the large temperature difference in space and the different CTE of plastic and metal Constant thickness of the coating inside and outside of the WG Roughness: ra < 2µm
Scheme of CFRP metallisation Cleaning and drying Removing dust, form release agents, finger prints from the surface with water and acetone Removing water from the plastics (heat treatment) Etching Removing the outer resin layer in order to roughen the surface Pre-metallisation Electroless deposition of a thin electrically conductive layer Metallisation Electrolytic deposition of Nickel and Copper Passivation and drying Dipping process in order to prevent the oxidation of copper Blow off with air and heat treatment to remove traces of water
Metallisation defects Not allowed: Defect size about 0,4mm Not allowed: Free metallised fibres Not allowed: (Large non-metallised areas
Metallisation defects Most frequently defects: Metallised fibres (electrically conductive); unmetallised resin (electrically insulating)
Critical points Complete metallisation Exact dimensions of wholes and slots Metallised non-metallised area (adhesion problems) Perfect metallisation of inlet and outlet
Cross sections of metallised CFRP wave guides Metallisation of the fibres Metallisation of the pure resin Metallisation of the mixed area fibres - resin
Cross sections Top view with a light microscope on the surface of CFRP Left: without any pre-treatment Right: after etching Cross sections of metallised CFRP Uncovered fibres Pure resin
Quality Management Demanded Quality Actions 100% control the coating quality visually by an endoscope (defects, free fibres) the coating weight (to calculate the coating thickness) the adhesion by an tape test the size of the metallised wholes by a defined wire Periodic control the coating thickness by investigating the cross sections under light microscope the roughness value Ra < 2 µm....
Quality Management Adhesion testing: Thermal shock test by dipping the WG in liquid Nitrogen (b.p. -196 C) and boiling water (b.p. +100 C) (5X) The Scotch tape with very high adherence must not show any metal pieces
Process Equipment Process Equipment: From Etching CFRP to the completely metallised waveguide
Conclusions Conclusions The complete and defect free metallisation of CFRP waveguides for aerospace application is possible and will be performed in an industrial scale The process of the waveguide metallisation is transferable to other devices with a simple or complex 3-D-geometry The usual metals can be deposited like Copper, Nickel, (Hard)-Chromium, noble metals The metallisation is useful for following applications Electrical conductivity (lightning protection) Diffusion barrier against gases and liquids Bonding and soldering of metal parts on CFRP Tribological application like increased wear resistance or low CoF With limitations: decorative effects....
Metal deposition on CFRP Thank you for your attention!