Solving Thermosteel fragility problem

[matt512s]

Hi All;
I believe I have a solution for the brittle nature of thermosteel. The concrete industry has developed a method
of reinforcement called micro reinforced cement. It consists of staggered layers of welded wire mesh (think hardware cloth)
tied together to form a 3-D reinforcing mat. When infiltrated with concrete slurry, the resulting composite has strength
and ductility far in excess of ordinary reinforced concrete. Why couldn't this be tried in smaller scale with stainless steel
mesh layers infiltrated with thermosteel? Maybe this is the answer for those of us without metalworking or welding skills.
Best wishes:
Matt

[ace_fedde]

At what temperature concrete will loose it strength? And at what temperature it looses structure and returns to the state of cement?

Fedde

[matt512s]

Hi;
My proposal is not to actually use cement or concrete, but to use a similar reinforcement mat system
infiltrated with thermosteel. The mat system provides the ductility.

[vturbine]

Heh, reminds me of the old days in naval architecture. Ferrocement was a fad in boats -- back in the 70's when it was thought that it would be easier than any of the other normal construction methods. This turned out not to be so. While simple in concept, it actually took a lot of skill, a lot of time, and good design and planning to turn out a good boat. Just like the other methods.

It sounds from the specs that thermosteel might withstand temperatures up to the melting point of steel, but that may not be the whole story. What is yield strength of the composite? What are the different expansion rates of thermosteel and the reinforcing fabric at running temps? What is the weight of an adequate thickness for the design purpose? How will it be surface finished on the interior for adequate smoothness? How will it be molded?

It sounds like it is something that's worth a try if you are truly interested (and it and stainless mesh are afordable in a small enough quantity for you). It will certainly take time to do -- build a mold or armature, and plaster it without voids, while maintaining finish standards, or milling the interior out.

It may be useful for complex shapes with compound curves, which are more difficult in sheet steel. Also may be useful for fillets in sheet steel construction, interior tapers of inlets, etc. I think a hybrid construction could make sense. So I'm not trying to discourage exploration. But just remember it may be more expensive and more time consuming to make a whole pulsejet this way, by comparison with sheet steel construction.

[matt512s]

Hi;
I must confess my proposal is based on the assumption that thermosteel has similar expansion characteristics
to steel. I have not researched this as fully as perhaps I should have. My intent was to suggest an approach that
might not have been considered. I recognize that fabrication may be more expensive and complicated, but I am
without metalworking or welding skills. This is why a molding process would be appealing to me. Thanks for the
feedback.
Best wishes;
Matt

[vturbine]

Hi;
I must confess my proposal is based on the assumption that thermosteel has similar expansion characteristics
to steel. I have not researched this as fully as perhaps I should have. My intent was to suggest an approach that
might not have been considered. I recognize that fabrication may be more expensive and complicated, but I am
without metalworking or welding skills. This is why a molding process would be appealing to me. Thanks for the
feedback.
Best wishes;
Matt

Well, you could certainly try it to find out. If you do, maybe you could use steel tube or pipe (all you need is a hacksaw for that and a file), and your matrix in combination. That way interior finish is mostly the tube.

Or build Mike Everman's Ugly Stick - that one requires no metalworking skills other than drilling for a sparkplug and putting things together with a pipe wrench.

[Rossco]

Hey guys,
Someone was working with ceramic jets at one stage, Craig i think.
Its possible, and we would all here be very interested to see how you go with it, from memory it ended with a busted engine or two last time before being abandoned.

Rossco

viewtopic.php?f=3&t=4152 (pulled my finger out and looked it up)
I would suggest a much smoother starting and runner than this chosen model to say the least.

[ace_fedde]

Matt,

Hi;
My proposal is not to actually use cement or concrete, but to use a similar reinforcement mat system
infiltrated with thermosteel. The mat system provides the ductility.

O.k., didn't get you there because we don't have thermosteel at the Dutch market, maybe something simular but then with a different name.
I thought that thermosteel was the metallic part of the concept (with concrete) while it is a composition.

I've been thinking (more fantasies then real plans, as usual ) of using Rockwool with sodiumsilicate (we call that waterglass, it's used to make moulds).
But sodiumsilicate melts at 1043 celcius so it cannot be used for all parts.
Who knows what temperatures carbonfiber can stand?

Fedde

[ace_fedde]

Let's proceed here:

viewtopic.php?f=3&t=4152&st=0&sk=t&sd=a&start=60

(the one that Rossco found)

Fedde

[vturbine]

Hey guys,
Someone was working with ceramic jets at one stage, Craig i think.
Its possible, and we would all here be very interested to see how you go with it, from memory it ended with a busted engine or two last time before being abandoned.

Rossco

viewtopic.php?f=3&t=4152 (pulled my finger out and looked it up)
I would suggest a much smoother starting and runner than this chosen model to say the least.

The big problem with ceramics -- in foundry furnaces and burners in my experience are differential expansion and contraction, which causes cracks. Just like a glass jam jar. This is generally avoided by making the lining of a furnace non-monolithic -- in other words by incorporating bricks -- which are essentially separate units, or pieces of pre-fired masonry in the mix, or grog, which is also ground up pre-fired ceramic. Yes it is possible to make a very high temperature monolithic lining in ceramics, but they do not like rapid heat up or cool down, and especially, temperature differential along their length. You will notice that the Space Shuttle has tiles, it isn't one continuous piece, or coating. That wasn't done because they accidentally hired a former brickylayer to design the heat shield. They did it because they wanted to control cracking and expansion.

I would say that a pulsjet of sorts could be built the same way -- a steel sleeve, lets say, with fitted tiles or bricks, or a grog mix semi-monotithic coating inside. It will probably develop cracks, but the steel casing will hold it together to some extent, and possibly chunks won't fall out if they are physically keyed in. But it seems to me that the interior of a pulsejet is probably one of the harshest environments imaginable for ceramics, excluding the space shuttle, because of the continual explosive deflagrations, and longitudinal temperature differentials, as well as the rapid heat up.

I also wonder if a brick lined pulsejet would be the best choice for a thrust to weight ratio comparison.