Durability of composites

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18 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Durability of composites

in the marine environment

John
Summerscales

Plymouth University


Plymouth


Advanced Composites Manufacturing Centre


only UK undergrad. composites degrees:

BEng

(honours)

Mechanical Engineering with Composites


BSc

(honours)

Marine and Composites Technology


Marine
C
entre
at
Coxside

under re
-
development for

diving and diver
training

plus
technical support
to

marine
-
based
projects
and

research
activities
.

Plymouth Sound


Third largest natural harbour in the world


Hosted America’s Cup in September 2011

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


m
arine renewable energy


o
ffshore oil and gas


d
efence 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

o
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”

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

Crystallinity or
extent
-
of
-
cure

chain ends

to backbone ratio

loading rate

moisture
content

Tg = glass
transition

below Tg:
elastic/brittle

above Tg:

viscoelastic/tough

key design
parameter

in aerospace

“hot wet Tg”

Wright
(Composites
, July
1981) found
"as a rough
rule
-
of
-
thumb“

that
there was a drop
in T
g

of epoxy resins of

20
°
C for
each 1% of water pick
-
up
(up
to 7% moisture content
).

Peak surface temperature
vs

ambient air temperature

b
lack

b
rown

r
ed

green

o
range tan

p
urple

blue

l
ight blue
Al

y
ellow

white

surface
°
C

120


100


80


60


40


20


0


10


20


30


40 50 ambient
°
C

r
edrawn from SP Systems
design allowable booklet



Moisture diffusion

Moisture (Fickian diffusion)

… or Flory
-
Huggins or
Langmuir/Henry/clustering models ?

Moisture content

√(time)

equilibrium/saturation

Saturation moisture content (M%)
*


M% dependent on (resin) chemistry

o
M%
max

<0.5%
(only
apolar

groups)


polyolefins
, PTFE, polystyrene,
polydimethylsiloxane

o
M%
max

<3.0%
(non
-
hydrogen donors)


polyethers
, polyesters

o
M%
max

<10%
(H
-
donors in hydrogen bonding)


p
olyvinylalcohol
,
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



residual glycol



high acid value resin



too little or too much styrene



too much catalyst (carrier)

raw materials



soluble binder/release systems



gel
-
coat thickness and quality



permeability of gel
-
coat < laminate



dark pigments

chemical/physical
factors



inadequate mixing



incomplete wet
-
out or consolidation



elapsed time between layers



degree of cure

process factors

Osmosis and blistering


For marine applications, consider

o
changing from
ortho
phthalic

to
iso
phthalic

polyester resin

o
and to improve “
iso
” resin further,

use
NPG

(neo
pentyl

glygol
):


HO
-
CH
2
-
C(CH
3
)
2
-
CH
2
-
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


f
ibre composed primarily of

cellulose, hemicellulose, lignin and pectin


limited solubility in water


successful applications include

o
Araldite:
6.5 metre racing yacht

o
Flaxcat
:
light
-
weight
catamaran/Delft


… but time will tell ?


LCA important if product life

< “traditional” equivalent



Cavitation erosion


Cavitation

=
spherical
b
ubble 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
*


o
impact
stress may exceed 1000 MPa

o
duration of pulse ~2
-
3
μ
s



$
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



h
ow much good data is locked away in
publicly
-
funded defence “stealth” research ?

o
National Technical Information Service

(US NTIS) search for “cavitation erosion”:

returned “
0
document
found
”.

o
OpenGrey

SIGLE (System for Information on Open Grey
Literature in Europe) search for “cavitation erosion
composite(s):

1(2) non
-
polymer items returned.

o
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

o
student projects
*

suggested

CFRP proportional loss in weight

only 40% of that for Al under identical conditions

o
but difficult experiment


CFRP absorbs some water


may have low initial
-

but accelerating
-

loss rate

* Handley ..and..
Ladds

(1995)


Cavitation
erosion/ADCO

Abu Dhabi Commercial Oil


o
il pipe diffuser section


s
teel 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

i
ncluding antifouling paints

Marine coatings


Surface coatings may be for

o
provide aesthetic finish

o
improve resistance to corrosion

o
protect against fouling


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

o
biofouling

reduces vessel speed by

10%

o
a
dded drag increases
fuel consumption by

40
%.

Antifouling paints

Toxic
compositions

cuprous oxide


increasing
concern

tri
-
butyl tin


now banned
worldwide

Exfoliating/
self
-
polishing
surfaces

microparticles

-
increasing
concern

Non
-
toxic low
surface energy
compositions

Bio
-
inspired approach
(biomimetics)

Liedert and Kesel:
shark skin as the
analogue

surface
microstructure,
Rz

= 76
μm


soft silicone
material

(shore A = 28)

low surface
energy

(25
mN
/m)

adhesion
to
substrate issues

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 H
2
O and CO
2

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


c
avitation erosion

o
need more research


g
alvanic corrosion in CFRP systems

o
avoid by isolating conductive elements


marine coatings


f
lame, 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 ?