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Durability of composites in the marine environment John Summerscales Plymouth University.

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Presentation on theme: "Durability of composites in the marine environment John Summerscales Plymouth University."— Presentation transcript:

1 Durability of composites in the marine environment John Summerscales Plymouth University

2 Plymouth Advanced Composites Manufacturing Centre only UK undergrad. composites degrees: BEng (honours) Mechanical Engineering with Composites BSc (honours) Marine and Composites Technology Marine Centre at Coxside under re-development for diving and diver training plus technical support to marine-based projects and research activities.

3 Plymouth Sound Third largest natural harbour in the world Hosted Americas Cup in September 2011

4 External presentations Ifremer/ONR International Workshop on Durability of Marine Composites Nantes - France, 23 August Wuhan University of Technology Wuhan – China, 06 September ICACME 2013: First International Conference Advanced Composites for Marine Engineering Beijing – China, 10 September 2013

5 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.

6 Applications marine renewable energy offshore oil and gas defence vessels submarines lifeboats powerboats sterngear yachts canoes surfboards … and all the others

7 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

8 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)

9 Temperature

10 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).

11 Peak surface temperature vs ambient air temperature black brown red green orange tan purple blue light blue Al yellow white surface °C ambient °C redrawn from SP Systems design allowable booklet

12 Moisture diffusion

13 Moisture (Fickian diffusion) … or Flory-Huggins or Langmuir/Henry/clustering models ? Moisture content (time) equilibrium/saturation

14 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) polyvinylalcohol, polyacrylic acid, polyacrylamide * Xavier Colin and Jacques Verdu at Ifremer-ONR workshop on Durability of composites, 2012.

15 Osmosis … and blistering

16 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 solutionStrong solution

17 Osmosis... normally the fluid will pass through the material without affecting it but, there may be soluble materials ….

18 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: westsystem/wsosmosis.html

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20 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

21 Osmosis and blistering For marine applications, consider o changing from orthophthalic to isophthalic 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:

22 Natural fibre composites fibre 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

23 Cavitation erosion

24 Cavitation = spherical bubble collapse The following slides use images extracted from numerical simulation in Kawitachnik videoKawitachnik video (http://www.youtube.com/watch?feature=player_detailpage&v=Ibd-v1YbD8c )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 μs $ W Lauterborn and H Bolle, … cavitation bubble collapse …, J Fluid Mechanics, 1975, 72(2), * A Karimi and JL Martin, Cavitation erosion of materials, International Metals Reviews, 1986, 31(1), 1-26.

25 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

26 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

27 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

28 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

29 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

30 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

31 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

32 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

33 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

34 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

35 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

36 Cavitation erosion Collapsing bubble: Solid surface model from Lauterborn and Bolle - video from Kawitachnik

37 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

38 Cavitation erosion in NAB propeller photographs courtesy of Peter Dyson

39 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 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

40 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)

41 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

42 Galvanic corrosion

43 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.

44 Galvanic corrosion notCarbon 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.

45 Marine coatings including antifouling paints

46 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

47 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 added drag increases fuel consumption by 40%.

48 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 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)

49 Flame, smoke and toxicity

50 Flame, Smoke and Toxicity (FST) important for … submarines underground railways sub-surface mines

51 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

52 Balmoral offshore lifeboat glass reinforced plastic fire-retardant resins carries 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

53 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

54 Acknowledgements Plymouth Sound images

55 Thank you for your attention …. any questions ?

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57 Je vous remercie de votre attention …. des questions ?


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