Concrete Submarines

[Constant (David)]

Beneath the waves is a long way from Astro, however..... Ruminating upon the kurfuffle of the new French subs, in my mind arose a question.... "Why aren't the hulls of Subs constructed in concrete"?
The decade that style forgot, the 1970's a decade that delivered Glam Rock & Desert Boots, the 70's also gave us concrete sailing boats, quite a few of them.
Given that concrete is extremely strong in compression and that the foremost requirement of a Sub is that its resilient and strong under compression, why not build Subs with concrete outer hulls? Concrete is quieter acoustically than steel, titanium or aluminium, would it not be a better material?
I've a feeling there's more than one Naval Architect in our midst. My fingers are crossed for an answer to my question.... "Why isn't concrete used in building Submarines"?

[mura_gadi (Steve)]

Hello,

Just read a little about the concrete ships of WWI and WWII, public opinion seems to have been a big driver in WWI for the lack of success.

Little note, "huge difference in vertical and horizontal compression forces. Metal hulls can deform without breaking. A concrete submarine will crack"

I'd say that will be a large part of the answer...



Steve
Ps. I like the idea of them becoming a rock on the seabed though, they would be tough buggers to find.

[Hans Tucker (Hans)]

To sort of expand on this why aren't we seeing more composite technologies in the manufacture of Submarines like we are witnessing in the Aerospace Industry and in part other Maritime vessels.

[Tulloch (Andrew)]

FYI
https://www.australiandefence.com.au...erial-advances

[julianh72 (Julian)]

There's a LOT of reasons for choosing steel and other metallic alloys over concrete, but a good place to start is to consider the "specific compressive strength", which is compressive strength divided by density. (Other factors to be considered include weight, ductility - the ability to deform without failing, flexural / bending strength, tensile strength, corrosion resistance, impermeability, buckling, magnetic signature, surface finish, repairability, fatigue resistance, etc. Engineers select the materials they use considering all of their relative performance characteristics - and cost.)

High-performance concrete has quite good compressive strength (~ 50 MPa say) for a modest density (~ 2.4 tonnes per cubic metre, say); high-performance steels can be 10 times stronger in compression than concrete (or more) for approximately three times the density. All things considered, a tonne of steel can carry three or more times the compressive load of a tonne of concrete. Exotic metal alloys can be much stronger and much lighter than high-performance steels.

This Wikipedia article https://en.wikipedia.org/wiki/Specific_strength gives you some comparative information on the specific tensile strength of various materials. Most engineering metals have comparable compressive strength as their tensile and bending strength; concrete is much stronger in compression than it is in tension or bending (but still a lot weaker than steel and aluminium, for example), while a lot of advanced composites are much stronger in direct tension than they are in compression or transverse tension.

[Constant (David)]

Originally Posted by Tulloch

FYI
https://www.australiandefence.com.au...erial-advances

Very informative!

[Constant (David)]

[QUOTE=julianh72;1522458]There's a LOT of reasons for choosing steel and other metallic alloys over concrete, but a good place to start is to consider the "specific compressive strength", which is compressive strength divided by density. (Other factors to be considered include weight, ductility - the ability to deform without failing, flexural / bending strength, tensile strength, corrosion resistance, impermeability, buckling, magnetic signature, surface finish, repairability, fatigue resistance, etc. Engineers select the materials they use considering all of their relative performance characteristics - and cost.)

High-performance concrete has quite good compressive strength (~ 50 MPa say) for a modest density (~ 2.4 tonnes per cubic metre, say); high-performance steels can be 10 times stronger in compression than concrete (or more) for approximately three times the density. All things considered, a tonne of steel can carry three or more times the compressive load of a tonne of concrete. Exotic metal alloys can be much stronger and much lighter than high-performance steels.

This Wikipedia article https://en.wikipedia.org/wiki/Specific_strength gives you some comparative information on the specific tensile strength of various materials. Most engineering metals have comparable compressive strength as their tensile and bending strength; concrete is much stronger in compression than it is in tension or bending (but still a lot weaker than steel and aluminium, for example), while a lot of advanced composites are much stronger in direct tension than they are in compression or transverse tension.[/QUOT

. Cheers