Mortar Question?

[johnny_boomboom]

I have a neighbor that works for a materials plant... they manufacture all types of fibers and composites. He informed me that he saw some scrap 2" OD, 1.9" ID Carbon Fiber tubing... There is about 50-100 feet of it... And of course I would like to know from the experts if that pipe might make good mortar tubes...

He also told me that the tubing type by the lot number is 4 to 6 times the strength of steel... so I guess it would withstand a break charge from a 1.4 shell... my concern is if it were wear out and flower pot on me, would I be looking at a PVC type shrapnal situation?

[Bill Corbett]

Johnny Boomboom, I'm not an expert on carbon fiber, however I see it being used more and more in my field. I'm a mechanical maintenance supervisor at Mps. Int. Airport. It's mainly used for drive shafts in cooling towers at my facility. I do know for a fact it's much stronger than steel, lighter, it doesn't corrode & is very expensive. A lot of airplanes use carbon fiber now days.
At this years PGI convention I noticed a man showing a piece of this carbon tubing to others in the trade show. He said it cost $30.00, it was 1" I.D. X 12" long & about 1/16" wall thickness, ouch!
If it were me I would get the scrap tubing, provided it's scrap, and not defective tubing which should be destroyed. Research the best ways to cut & drill it etc. before attempting so. This could be a safety hazard with conventional tools, bits & blades, maybe not??? As far as shrapnel goes, I really don't know. I can only ASSUME it will act like a fiberglass mortar. You may be a pioneer if you decide to work with this material. BE CAREFUL & continue to collect data & information on it before using it to launch shells.

[Dan]

Yeah, I am with Bill on this one. If you have a piece that is 2 inches and 12-15 inches long, Put a plug in one end of it, and take a consumer shell (somewhere safe and away from everything) and insert the shell upside down and fire it. Video tape the burst, and then report back to us what happened. My thought are that since carbon fiber comes in long strands, it will peal away and splinter.

If you do test it, please take all precautions and fire it from a safe distance.

Dan

[carp]

A thread from the old forums this:


"Not sounding good for carbon fiber either. See bold statement below:

Carbon fibers in composites can be long and continuous, or short and fragmented, and they can be directionally or randomly oriented. In general, short fibers cost the least, and fabrication costs are lowest; but, as with glass, properties of resulting composites are lower than those obtainable with longer or continuous fibers.

Milled fibers are the shortest carbon fibers used for reinforcement. They range in length from 30 to 3,000 microns, averaging approximately 300 microns. Mean L/D ratio is 30. Short chopped fibers (about ¼ in. long), with an L/D ratio of about 800, increase strength and modulus of a composite more than milled fibers do. Cost of a molding compound reinforced with ¼ -in. fibers is about twice that of one containing milled carbon fibers.

Long chopped fibers (to 2 in.) are often added to a thermosetting glass/polyester sheet-molding compound to increase the stiffness of compression-molded parts. Continuous carbon fibers provide the ultimate in performance and/or weight reduction. Continuous fibers are available in a number of forms including yarns or tows containing 400 to 160,000 individual filaments; unidirectional, impregnated tapes up to 60 in. wide; multiple layers of tape with individual layers, or plies, at selected fiber orientation; and fabrics of many weights and weaves.

The outstanding design properties of carbon fiber/resin matrix composites are their high strength-to-weight and stiffness-to-weight ratios. With proper selection and placement of fibers, the composites can be stronger and stiffer than equivalent thickness steel parts and weigh 40 to 70% less. Fatigue resistance of continuous-fiber composites is excellent, and chemical resistance is better than that of glass-reinforced systems, particularly in alkaline environments. Like most rigid materials, however, carbon-fiber composites are relatively brittle. The composites have no yield behavior, and resistance to impact is low.

Thermal characteristics of carbon fibers are different from those of almost all other materials. Linear expansion coefficients range from slightly negative for 30 million-psi modulus fibers to approximately -1.3 × 10 (to the 6th power) in./in.- °F for the ultrahigh-modulus fibers. This property makes possible the design of structures with zero or very low linear and planar thermal expansion -- a valuable characteristic for components in precision instruments such as telescopes and for the alignment requirements of aerospace antennas and similar critical parts. Transverse coefficients of expansion are quite different -- typically 15 × 10 (to the 6th power) in./in.- °F.

The thermal conductivity of ultrahigh-modulus pitch-based carbon fibers exceeds that of copper. When density differences are considered, the specific conductivities can be as much as eight times that of copper."

[pyrocasto]

I agree with doing a test. Pick up some of this bad stuff and drop a shell down it upsidedown. Just make sure you are far away and behind something when it goes off.

Video camera should be the only thing looking at it.

[johnny_boomboom]

I am going to try it... I have a diamond blade saw to cut it and I have titanimum bits to drill in for screws to set the plug...

I also have a Lexan... windshield from a cup car... pretty much bullet proof.. to video through and a remote firing system...
will update you ...

[lwoodpyro]

Not shredding with a few practice shells doesn't mean it won't EVER happen. If it's able to shred, then, when you least expect it....
Not worth it. Spend the money on hdpe.

[johnny_boomboom]

I wouldn't be concerned with it shedding.. i am concerned about fragmenting like PVC or ABS... HDPE shreds...

[noel]

Proper testing is to test until it fails, not to test to see if it doesn't, because it will, you have to find at what point it fails, and what happens when that happens.


For regular HDPE, one of our tests was we fired 10 shells as fast as we could, and then inverted a shell. It blew out the side, but zero fragmentation.

I am wanting to do a failure test on Fiberglass just to see what the fragmentation looks like, and how many regular shells it takes to get it to fail, along with what happens once it's heated up and then gets a invert.

If a mortar can be found not to explode under normal shells, then we go on to something with more punch, There are 1.75" salutes (not consumer), what happens when that is fired?.... testing is important.

But testing in a safe enviroment, can't just go in the back yard and start shooting, need to have correct aparatus.

[johnny_boomboom]

I have a large clear area... a Lexan barrier and remote firing....

[carp]

You could and probably should, completely bury the mortar.

[johnny_boomboom]

Not a bad idea... will do...

[DennyMo]

So what's the latest on this?

[johnny_boomboom]

Nothing yet... I got the 6 foot section of pipe but Ihaven't had a chance to do anything with it it....:( too busy with work...:( :D