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Galvanic Metallisation of CFRP devices

A. Dietz, G. Klumpp, H.-J- Kramer Fraunhofer IST, Braunschweig

C. Haas Astrium GmbH Friedrichshafen

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Fraunhofer IST – Business field „Aerospace“

Copernicus - Sentinel

Fundamentals of Plastic Metallisation

Metallisation of Waveguides

Quality Management

Conclusions

Galvanic Metallisation of CFRP devicesOverview

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Metallisation of materials

CFRP, FRP, Plastics

Light metals, such as titanium, magnesium, aluminium

Ceramics

Coating and process development

Electroplating

Vacuum technology (PVD, Plasma CVD)

Atmospheric pressure CVD

Plasma diffusion processes

Coatings for friction reduction and wear protection

Dry-film lubricant coatings (e.g. MoS2…)

Hard chromium, electroless Nickel, DLC, diamond…

Galvanic Metallisation of CFRP devicesFraunhofer IST: Business unit“Aerospace”

Installation technology

Design of plants

Plants on laboratory, pilot and production scale

Quality assurance and documentation

Surface analysis and characterisation

Test procedures and product-specific quality control

Technology transfer

Prototype development

Low-quantity production

Economic appraisals

Consulting services

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Copernicus - 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

Galvanic Metallisation of CFRP devicesESA-Mission Copernicus/Sentinel

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Copernicus:Computer simulation of Sentinel 1 in LEO(Low Earth Orbit; 693 km altitude)

Galvanic Metallisation of CFRP devicesSentinel

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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

Galvanic Metallisation of CFRP devicesCopernicus/Sentinel

Scheme of the Sentinel 1waveguide array

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Challenges of the plastic metallisation

Hydrophobic surface – no wetting

Electrically insulating surface – no directmetallisation

Different atomistic properties between plasticsubstrate and metallic coating bad adhesion

Galvanic Metallisation of CFRP devicesMetal deposition on plastics

Cathode/work piece

Power source

Ni Ni2+ + 2e-

Ni2+ + 2e-Ni

Anode

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Problems

Passivation of very unnoble substrate metals like Titanium, Aluminium …

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

Galvanic Metallisation of CFRP devicesComparison: Electrodeposition on metal substrates

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Push button effect Metal

Plastic

Galvanic Metallisation of CFRP devicesMetal deposition on plastics

Wetting theory

Etched plastic surface

Wetted surfaceNon-wetted surface

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Dog bone effectdue to the streamlines of field

Homogeneous deposition by means of auxiliary anodes

Galvanic Metallisation of CFRP devicesHomogeneous deposition on complex geometries

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Dimension: VP: Length: 870mm; Width: 20mm; Height: 20mmHP: 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 thedifferent CTE of plastic and metal

Constant thickness of the coating inside and outside of the WG

Roughness: ra < 2μm

Galvanic Metallisation of CFRP devicesCopernicus/Sentinel

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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

Galvanic Metallisation of CFRP devicesScheme of CFRP metallisation

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Not allowed: Defect size about 0,4mm

Galvanic Metallisation of CFRP devicesMetallisation defects

Not allowed: Free metallised fibres

Not allowed: (Large non-metallised areas

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Most frequent defects:

Metallised fibres (electrically conductive); non-metallised resin (electrically insulating)

Galvanic Metallisation of CFRP devicesMetallisation defects

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Galvanic Metallisation of CFRP devicesCritical points

• Complete metallisation• Exact dimensions of

wholes and slots

• Metallised –non-metallisedarea (adhesion problems)

• Perfect metallisation of inlet and outlet

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Galvanic Metallisation of CFRP devicesCross sections of metallised CFRP wave guides

Metallisation of the fibres Metallisation of the pure resin

Metallisation of the mixed area fibres - resin

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Galvanic Metallisation of CFRP devicesCross sections

Cross sections of metallisedCFRP• Uncovered fibres• Pure resin

Top view with a light microscope on the surface of CFRP• Left: without any pre-treatment• Right: after etching

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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 a 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

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..

Galvanic Metallisation of CFRP devicesQuality Management

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Galvanic Metallisation of CFRP devicesQuality 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

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Galvanic Metallisation of CFRP devicesProcess Equipment

Process Equipment: From Etching CFRP to the completely metallised waveguides

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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, precious metals

The metallisation is useful for following applications

Electrical conductivity (antennas, 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

..

The Launch of Sentinel 1a was 3 April 2014

Galvanic Metallisation of CFRP devicesConclusions

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Thank you for your attention!

Galvanic Metallisation of CFRP devicesMetal deposition on CFRP