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A comment on Titanic tourist sub goes missing sparking search. Parent comment

Re:Titanic tourist sub goes missing sparking search by mcpackieh on Monday June 19, 2023 @04:17PM (#36395976)
My first thought was that expanding foam from the hardware store is very cheap, but obviously that sort of foam would be crushed by the water pressure.

> Syntactic foams are composite materials synthesized by filling a metal, polymer,[1] cementitious or ceramic matrix with hollow spheres called microballoons[2] or cenospheres or non-hollow spheres (e.g. perlite) as aggregates.[3] In this context, "syntactic" means "put together." [...] The compressive properties of syntactic foams, in most cases, strongly depend on the properties of microballoons.

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Re:Titanic tourist sub goes missing sparking search by selimthegrim on Monday June 19, 2023 @05:18PM (#36396606)
I wonder how similar its properties are to air-entrained concrete.
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Re:Titanic tourist sub goes missing sparking search by jacquesm on Monday June 19, 2023 @05:50PM (#36396911)
Not very because air-entrained concrete has very little resistance to crumbling and doesn't handle tensile stress well (which you could fix by adding fibers or some other element that handles tension better, hence reinforced concrete). It has plenty of applications under normal atmospheric conditions but for submersibles you will want something with entirely different properties.
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