Richardw's Narrow Boat Project- PLATE THICKNESS

pdwiley · Jul 21, 2014

Ad Hoc said: ↑

I was doing some research at the weekend on a totally unrelated subject and dug out one of my papers . And funnily enough came across this very subject. Anyway, the figures below clearly shows the superiority of blunt and sharp contact, as abrasion resistance, of metals. Where ceramics being the superior ones of course, followed closely behind by most metals, and the poor performance of composite.

View attachment 92942
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Thanks for that, it demonstrates the point nicely.

Not that it will stop someone coming along in another day/week/month claiming that GRP structures are superior in toughness to metal ones when it comes to boat hulls.....

You can do a lot of things with GRP that is difficult to do with metals. Impact and abrasion resistance simply are not 2 of the superior features.

PDW

SukiSolo · Jul 21, 2014

Ad Hoc said: ↑

For steel, the yield occurs at around 3-5% strain, then after the yield point in steel it dips then continues to increase in both stress and strain. This is what is called the plastic region. So, even though the steel has gone beyond its yield limit the material, or structure, has not failed. You can continue to overload the steel it won’t fail, it just stretches. It can stretch until around 35% of its original shape, before complete failure.
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So we can look forward to explosion formed steel canal craft by the banks of the Wey Navigation....

There are other examples, like aluminium 20' containers which allow approx 1 tonne more internal load, yet are tough enough for commercial service.

Ad Hoc · Jul 21, 2014

SukiSolo said: ↑

So we can look forward to explosion formed steel canal craft by the banks of the Wey Navigation....
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Never say never...

rxcomposite · Jul 21, 2014

pdwiley said: ↑

I'm really tired of this argument about the toughness of f/g type structures. Rub a f/g hull against a timber piling and you get a hole in the hull. Rub a steel hull against a timber piling for the same length of time and you get polished metal.

PDW
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It is not about toughness but the hardness. Steel is high density material and with high density comes high modulus. Thus if you rub steel against FRP, the steel will win much like filing the edges of an FRP laminate with a steel file.

Attached table shows steel has a higher modulus than FRP.

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Richardw's Narrow Boat Project- PLATE THICKNESS

pdwiley Senior Member

SukiSolo Senior Member

Ad Hoc Naval Architect

rxcomposite Senior Member

Attached Files:

Modulus table001.jpg

Richardw's Narrow Boat Project-Below The Waterline

Richardw's Narrow Boat Project -BILGE AND BALLAST