Transcript Environmental resistance of composites

Durability of composites
in the marine environment
John Summerscales
Plymouth University
External presentations
• Ifremer/ONR International Workshop on
Durability of Marine Composites
Nantes - France, 23 August 2012.
• Wuhan University of Technology
Wuhan – China, 06 September 2013.
• ICACME 2013: First International Conference
Advanced Composites for Marine Engineering
Beijing – China, 10 September 2013
Key references
• J Summerscales and TJ Searle (1999)
Review of the durability of marine laminates
in G Pritchard (ed.)
Reinforced Plastics Durability
Woodhead Publishing, Cambridge, pp 219–266.
• J Summerscales (2014)
Durability of composites in the marine environment
in P Davies and YDS Rajapakse (eds.)
Durability of composites in a marine environment
Springer, Dordrecht (NL), pp 1-13.
Applications
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marine renewable energy
offshore oil and gas
defence vessels
submarines
lifeboats
powerboats
sterngear
yachts
canoes
surfboards
… and all the others
Durability
• defined as good for
the full intended working life of the system
• the downside is end-of-life considerations
only a limited number of museums
want to keep artefacts for ever 
o if sufficiently desirable
objects may be trading in the antiques market
o if too durable
then difficulties arise in “recycling”
o
Outline of lecture
glass transition temperature
diffusion of moisture
osmosis and blistering
cavitation erosion
galvanic corrosion
marine coatings
antifouling paints
flame, smoke and toxicity (FST)
Temperature
Glass transition temperature
Tg is a
function of:
molecular
structure
Tg = glass
transition
below Tg:
elastic/brittle
key design
parameter
in aerospace
Crystallinity or
extent-of-cure
chain ends
to backbone ratio
loading rate
above Tg:
viscoelastic/tough
“hot wet Tg”
Wright (Composites, July 1981) found "as a rough rule-of-thumb“
that there was a drop in Tg of epoxy resins of
20°C for each 1% of water pick-up (up to 7% moisture content).
moisture
content
Peak surface temperature vs
ambient air temperature
120 surface °C
black
brown
red green
orange tan
purple blue
light blue Al
yellow
white
100
80
60
40
20
redrawn from SP Systems design allowable booklet
0
10
20
30
40
50 ambient °C
The response is dependent on the chemical nature of the dye/pigment and
the heating may be reduced by choosing low solar absorbance materials.
Moisture diffusion
Moisture (Fickian diffusion)
Moisture content
equilibrium/saturation
… or Flory-Huggins or
Langmuir/Henry/clustering models ?
√(time)
Saturation moisture content (M%)*
• M% dependent on (resin) chemistry
o
M%max <0.5% (only apolar groups)

o
M%max <3.0% (non-hydrogen donors)

o
polyethers, polyesters
M%max <3.0%

o
polyolefins, PTFE, polystyrene, polydimethylsiloxane
cured epoxy
M%max <10% (H-donors in hydrogen bonding)

polyvinylalcohol, polyacrylic acid, polyacrylamide
* Xavier Colin and Jacques Verdu
at Ifremer-ONR workshop on Durability of composites, 2012.
Osmosis
… and blistering
Osmosis ...
• Osmosis can be defined (Clegg, 1996) as
“the equalisation of solution strength
by passage of a liquid (usually water)
through a semi-permeable membrane
membrane
Weak solution
Strong solution
Osmosis ...
• normally the fluid will pass
through the material without affecting it
• but, there may be soluble materials ….
Osmosis and blistering
• a little solvent and a lot of solute
-> a strong solution
• strong driving force for osmotic cell
• high pressures generated cause/expand void
containing strong solution
• swelling leads to blisters with
associated surface undulation
• Image from:
http://www.wessex-resins.com/
westsystem/wsosmosis.html
http://www.insightmarinesurveyors.co.uk/osmois%20ringed.jpg
Osmosis and blistering: causes
raw materials
•
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residual glycol
high acid value resin
too little or too much styrene
too much catalyst (carrier)
chemical/physical
factors
•
•
•
•
soluble binder/release systems
gel-coat thickness and quality
permeability of gel-coat < laminate
dark pigments
process factors
•
•
•
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inadequate mixing
incomplete wet-out or consolidation
elapsed time between layers
degree of cure
Osmosis and blistering
• For marine applications, consider
changing from orthophthalic
to isophthalic polyester resin
o and to improve “iso” resin further,
use NPG (neo pentyl glygol):
o
HO-CH2-C(CH3)2-CH2-OH
 2,2-dimethyl-1, 3-propanediol

• Durability:
o
ortho < iso < NPG
Chemical structure from: http://chemicalland21.com/specialtychem/perchem/NEOPENTYL%20GLYCOL.htm
Natural fibre composites
• fibre composed primarily of
cellulose, hemicellulose, lignin and pectin
• limited solubility in water
• successful applications include
Araldite: 6.5 metre racing yacht
o Flaxcat: light-weight catamaran/Delft
o
• … but time will tell ?
• LCA important if product life
< “traditional” equivalent
Cavitation erosion
Cavitation
= spherical bubble collapse
• The following slides use images extracted from
numerical simulation in Kawitachnik video
(http://www.youtube.com/watch?feature=player_detailpage&v=Ibd-v1YbD8c )
• vapour bubble collapse caused by cavitation
creates impinging jet of liquid onto solid surface$
• pressure pulse*
impact stress may exceed 1000 MPa
duration of pulse ~2-3 μs
o
o
$
*
W Lauterborn and H Bolle, … cavitation bubble collapse …, J Fluid Mechanics, 1975, 72(2), 391-399.
A Karimi and JL Martin, Cavitation erosion of materials, International Metals Reviews, 1986, 31(1), 1-26.
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion
• Collapsing bubble creates jet
towards a hard surface
loosens structure and removes material:
Solid surface
model from Lauterborn and Bolle - video from Kawitachnik
Cavitation erosion in NAB propeller
photographs courtesy of Peter Dyson
Cavitation erosion
• very limited public domain data
on fibre-reinforced composites 
• how much good data is locked away in
publicly-funded defence “stealth” research ?
o
o
o
National Technical Information Service
(US NTIS) search for “cavitation erosion”:
returned “0 document found”.
OpenGrey SIGLE (System for Information on Open Grey
Literature in Europe) search for “cavitation erosion
composite(s): 1(2) non-polymer items returned.
Karimi and Martin review:
2 references (of 231) for rain erosion of composites
Cavitation erosion
• composites may perform better than metals
because fibre > grain size
student projects* suggested
CFRP proportional loss in weight
only 40% of that for Al under identical conditions
o but difficult experiment
o
CFRP absorbs some water
 may have low initial - but accelerating - loss rate

* Handley ..and.. Ladds (1995)
Cavitation erosion/ADCO
Abu Dhabi Commercial Oil
• oil pipe diffuser section
• steel component replaced every month
• composite “temporary” replacement
removed from service after nine months
Galvanic corrosion
Galvanic corrosion
• corrosion involves flow of an electric current
• most constituents of fibre-composites are
insulators and hence
electrochemical corrosion is not an issue
• However, carbon (graphite) acts as a noble
metal, lying between platinum and titanium in
the galvanic series.
Galvanic corrosion
• Carbon fibres should
not come into contact
with structural metals
(especially Al or Mg)
in the presence of a conducting fluid
(eg sea-water).
• A thin glass fibre surface layer may be
sufficient to prevent the formation of such a
galvanic corrosion cell.
Marine coatings
including antifouling paints
Marine coatings
• Surface coatings may be for
provide aesthetic finish
o improve resistance to corrosion
o protect against fouling
o

especially for marine or process plant applications
• gel-coat is normally applied to the mould
before the laminate is laid-up/injected
• a major issue in the marine industry is
“print-through”
o
surface echoes topology of reinforcement
Benefit of antifouling
• Aristotle (fourth century BCE) observed that
small fish (barnacles) could slow down ships.
• US Navy [New Scientist, 1975] reported that
barnacles and other marine encrustations
on hulls increase drag, slow the vessel down
and estimate this consumes 25% of the fuel.
• US NSWC Carderock estimated
biofouling reduces vessel speed by 10%
o added drag increases fuel consumption by 40%.
o
Antifouling paints
Toxic
compositions
cuprous oxide
– increasing
concern
tri-butyl tin –
now banned
worldwide
Exfoliating/ selfpolishing
surfaces
microparticles increasing
concern
Non-toxic
low surface
energy
compositions
Adhesion to
substrate
issues
Polymer “brush”
coatings
Prevention of
attachment
Reduced
adhesion
strength
Degrade or kill
organisms
Biomimetic
approach:
shark skin
analogue
surface
microstructure,
Rz = 76 μm
soft silicone
material
(shore A = 28)
low surface
energy
(25 mN/m)
Flame,
smoke
and toxicity
Flame, Smoke and Toxicity (FST)
important
for …
submarines
underground
railways
sub-surface
mines
Flame, Smoke and Toxicity (FST)
F=
flame
low spread
of flame
S=
smoke
minimal
emission of
smoke
T=
toxicity
no Toxic
products of
combustion
phenolic resins burn
to just H2O and CO2
in the presence of a
good supply of air
Balmoral offshore lifeboat
• glass reinforced plastic
fire-retardant resins
carries 21-66 people
• certification required to
withstand 30 m high
kerosene flames and
temperatures of 1150°C
• throughout the fire test,
the temperature inside
never exceeded 27°C.
Image from the front cover of
International Reinforced Plastics Industry
May/June 1983, 2(5), 1
Summary
• temperature
o
stay below Tg
• moisture diffusion
o
this will happen
• (osmosis and) blistering
o
avoid with correct materials selection
• cavitation erosion
o
need more research
• galvanic corrosion in CFRP systems
o
avoid by isolating conductive elements
• marine coatings
• flame, smoke and toxicity
Acknowledgements
• Plymouth Sound images
•
•
•
http://upload.wikimedia.org/wikipedia/commons/9/94/Plymouth_Sound.jpg
http://www.heart.co.uk/plymouth/events/going-out/americs-cup-action-plymouth/americas-cup-action-2/
http://www.heart.co.uk/plymouth/events/going-out/americs-cup-action-plymouth/americas-cup-action-6/
Thank you for your attention
…. any questions ?