28 th March 2018 The Institute of Marine Engineering, Science and Technology (IMarEST) Auxetic structures for marine safety applications (rope, sandwich panel) Nadimul Faisal, Abbi McLeod, Findlay Booth, Lindsay Scott, Scott Duncan, Ghazi Droubi School of Engineering, Robert Gordon University, Aberdeen, UK
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Auxetic structures for marine safety applications …...• Auxetic – enhanced mechanical properties,negativePoisson’sratio. • Due to the high energy absorbing properties they
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28th March 2018 The Institute of Marine Engineering, Science and Technology (IMarEST)
Auxetic structures for marine safety applications(rope, sandwich panel)
• Failure of mooring line on board LNG carrier Zarga with 1 person injured; https://www.gov.uk/maib-reports/failure-of-mooring-line-on-board-lng-carrier-zarga-with-1-person-injured
• Collision between rigid inflatable boats Osprey and Osprey II resulting in serious injuries to 1 passenger; https://www.gov.uk/maib-reports/collision-between-rigid-inflatable-boats-osprey-and-osprey-ii-resulting-in-serious-injuries-to-1-passenger
• Contact made by passenger ferry Uriah Heep with Hythe Pier; https://www.gov.uk/maib-reports/contact-made-by-passenger-ferry-uriah-heep-with-hythe-pier
• Collision between ro-ro freight ferry Petunia Seaways and historic motor launch Peggotty; https://www.gov.uk/maib-reports/collision-between-ro-ro-freight-ferry-petunia-seaways-and-historic-motor-launch-peggotty
• Collision between pure car carrier City of Rotterdam and ro-ro freight ferry Primula Seaways; https://www.gov.uk/maib-reports/collision-between-pure-car-carrier-city-of-rotterdam-and-ro-ro-freight-ferry-primula-seaways
• Collision between general cargo vessel Daroja and oil bunker barge Erin Wood; https://www.gov.uk/maib-reports/collision-between-general-cargo-vessel-daroja-and-oil-bunker-barge-erin-wood
• Collision between the stern trawler Karen and a dived Royal Navy submarine; https://www.gov.uk/maib-reports/collision-between-the-stern-trawler-karen-and-a-dived-royal-navy-submarine
• Collision between stern trawlers Good Intent and Silver Dee resulting in Silver Dee sinking; https://www.gov.uk/maib-reports/collision-between-stern-trawlers-good-intent-and-silver-dee-resulting-in-silver-dee-sinking
• Collision between container vessel Ever Smart and oil tanker Alexandra 1; https://www.gov.uk/maib-reports/collision-between-container-vessel-ever-smart-and-oil-tanker-alexandra-1 6
Recent examples (Collision, as on 31 Aug 2017)
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Mooring system failure
• The primary objective of amooring system is to maintainvessel position, protect therisers, and prevent collision withnearby infrastructure.
• Failure types: single line failure,two line failure, or at the pointof collision or riser failure, etc.
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Safety in marine structures
• As human errors and technical failures cannot be prevented easily,measures can be taken to reduce the probability of risk of severeharm if an accident does occur.
• By attaching highly energy absorbent sandwich structures to theoutside of the ship, it is thought that this will help prevent criticaldamage to a vessel and therefore prevent any future fatalities orexpensive structural damage to marine structures.
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Incidents are categorised in the Port Operations Manual as follows: • Groundings
• Ships collision
• Ship contact
• Quay contact
• Rope parting
• Touching bottom
• Equipment failure
• Near miss
• Contact with port installation
• Miscellaneous
10Ref: Port Marine Safety Code\Fowey PMSC Sept 2017
Some practices (marine safety)
• Passive mountings between items of machinery and a flexible supportstructure such as rubber mounts and wire rope isolators.
• Passive mountings provides adequate isolation at high frequencies, thepassive solution loses its effectiveness at lower frequencies due to its ownnatural frequency.
• In the case of submarines, the advanced performance is required so far athigh frequencies in order to retain the stealth function. The use of activecontrol techniques can effectively cope with these problems.
• Hybrid mount (rubber mount and piezo-stack actuators) combined passive mounting devices with active technology represents a new alternative for naval ships.
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Auxetic structures
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• Greek terms ‘auxetikos’ and ‘auxesis’which mean “that which tends toincrease” and “increase” respectively,
Enhanced Model – Path Analysis (Path 1)Enhanced Model – Path Analysis (Path 4)Enhanced Model – Path Analysis (Path 3)
Energy Absorption
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Conclusion
• Filling and filleting the auxetic structure: reduced stress concentrations and decreased energy absorption.
• Decreased stress concentration increased the structures penetration resistance.
Summary
• Possible applications for HAYs made of light-weight materials such as PEEK orPTFE could replace conventional structures have been identified.
• A maximum NPR of -12.04 was achieved by lowering the wrap starting angle. Thefindings show that a starting wrap angle of 7° will produce the highest NPR. Thisshould be the design angle for optimised performance of the yarn.
• The use of a nitinol wrap is expected to increase the maximum NPR of a HAYcompared with conventional materials such as stainless steel or carbon fibre.Materials with low coefficients of friction such as PTFE or acetal would enhancethe auxetic behaviour if used as for the core material.
• While filling the model with material reduced the stress concentration, it led to areduction in the energy absorbance. The energy absorbed by an impact is of highimportance to the structural integrity of the vessel.