Composite blades?

[PeterGustafsson]

Hi!


Mr. Mechanical Engineer in action:
This thread is a spinoff of several safety-related threads of late. We all know that broken blades are much more dangerous than whole blades. Maraging is an attempt to alleviate the problem of the broken blade by making the break surface less sharp, but there is still a broken surface.

However, if one could make the blade break so that when it breaks the parts stay together, then there would be no break surface at all.

My suggestion for how to make such a blade: Instead of having a blade made of solid metal, make a blade out of a metal tube, which is totally filled by a rubbery material. The tube, in this context, is obviously a metal piece with a correct weapon cross-section. Rubbers have much lower Elastic modulus values than steel, so the total cross-section dimensions of the metal must be increased somewhat. However, the laws of deflection of a cantilever beam, and second moment of inertia of a cross-section, tells us that only a very slight increase in cross-section dimensions is needed, since the 2nd moment is proportional to the quartic of the linear dimension.

If one manufactures an appropriately shaped tube, then it can be filled with a non-cured rubber polymer, which is then let to cure. This is standard procedure for producing steel-rubber-steel coaxial springs. By choosing the correct rubber polymer, one can fine-tune the properties of the finished blade. My guess is that a polyurethane with a hardness of some Shore 50 A, or so, would be about right. Materials like that will bond quite well to the metal upon curing, which will enhance safety once a blade breaks.

Once this kind of blade breaks, it will behave totally different than the blades we have today. Since rubber polymers have much lower Elastic modulus and also much higher Elongation at Yield than steel, the fatigue fracture through the metal surrounding will not penetrate into the rubber core. Once the fracture through the metal is complete the blade will break - but the rubber core will hold the two pieces together! The fencer with the broken blade will be standing with a weapon where the distal end of the blade is left dangling from the rest. If he still continues his attack, the exposed rubber core will be the first part to hit the other fencer. This will present much less of a penetration danger. Even if he would manage to penetrate - which is highly unlikely even on ordinary non-fencing clothing - the still attached distal end of the blade would have to be pushed in, so it would be very difficult to penetrate to any depth.

I now place this idea in the open realm, which makes accessible to all, and patentable to no one.

What do you think? Any drawbacks? Any improvements? Miscellaneous comments?


Have a nice time!

Peter Gustafsson

[keith]

Originally Posted by PeterGustafsson

What do you think? Any drawbacks? Any improvements? Miscellaneous comments?

technical nit pick, maraging blades don't break differently they just break less often.

As to the composite blade, many many years ago the club I was at had one of those bizare blades that were a plastic core with a metal 'wrap' hard to describe but sounds similar to your idea. It felt horrrible, but was (after much much testing) apparantly close to indisctructable.

[shlepzig]

My worry would be if the fracture occurs and the rubber is sufficient to keep the two halves together so that the break is not apparent.

Thus the director would draw his attention to the problem and allow fencing to begin with a seriously compromised blade.

Currently in epee I most often (75% about) see a break occur and the wire holds the two ends together, but in a dangling fashion.

The safety concern you are trying to address, injuries caused by a broken blade are usually due to the blade breaking early in the action (on contact) and the motion continues with the broken end penetration the target. I don't know that the rubber core would prevent this.

However what may occur with sufficient composite material development you might be able to develop a blade that was not capable of shattering, and would only take a permanent bend on the end and be disposed of immediately.

That's my thought. I don't expect to be using a plastic epee any day soon though. I certainly don't expect to hear anyone telling me how great the new plastic epees ever.

Shlep.

[KD5MDK]

Among other things, epee blades need to be conductive to avoid touches scored on them, unless we do the ful body lame thing.

[PeterGustafsson]

Hi!

Originally Posted by KD5MDK

Among other things, epee blades need to be conductive to avoid touches scored on them, unless we do the ful body lame thing.

The outer metal tube would take care of that.


Have a nice time!

Peter Gustafsson

[PeterGustafsson]

Hi!

Originally Posted by keith

technical nit pick, maraging blades don't break differently they just break less often.

As to the composite blade, many many years ago the club I was at had one of those bizare blades that were a plastic core with a metal 'wrap' hard to describe but sounds similar to your idea. It felt horrrible, but was (after much much testing) apparantly close to indisctructable.

Does indeed sound close to my suggestion. Was the metal really wrapped around the plastic core? If so, was is a lot of wounds of thin metal wrapped to the necessary metal thickness? I was thinking of a tube, where the material in the tube wall is not formed from thinner layers.

In what way did it feel horrible? Light, too whippy, too difficult/too easy to do flicks, strange balance, unusual shape of flex curve, what?

What do you mean with "much much testing"? Was that rigorous testing in a designed for the purpose test bench, or just fencing around a great deal?

Do you have any pictures, web links, or maybe that blade itself available?


Have a nice time!

Peter Gustafsson

[PeterGustafsson]

Hi!

Originally Posted by shlepzig

My worry would be if the fracture occurs and the rubber is sufficient to keep the two halves together so that the break is not apparent.

Thus the director would draw his attention to the problem and allow fencing to begin with a seriously compromised blade.

If the metal is totally broken and the rubber core holds the pieces together, then the blade will bend in a very tell-tale way. Since the rubber is much softer than metal, almost all of the bend will happen at the break - where there is only rubber - and the two pices will be nearly straight. One will therefore see a knick on the blade. If such a blade is waved around, the distal part will quiver around the break in a very obvious manner. When the two break surfaces of the metal touch each other in such a waving, I expect that one would hear a typical metal rattling sound.

Originally Posted by shlepzig

Currently in epee I most often (75% about) see a break occur and the wire holds the two ends together, but in a dangling fashion.

I have seen the "dangling by the wire" break mode also, but in my personal experience those are in the small minority. The great majority of epee breaks that I have seen are cases where the wires break during the blade break.

For sabre there obviously is no "dangling by the wire" break mode.

Originally Posted by shlepzig

The safety concern you are trying to address, injuries caused by a broken blade are usually due to the blade breaking early in the action (on contact) and the motion continues with the broken end penetration the target. I don't know that the rubber core would prevent this.

Well, if the rubber is unbroken, you have to stick in both break ends to get penetration. The rubber must also bend so that the two blade parts are 180 degrees from each other, the blade must fold over. Once it has folded over, there will be an exposed part of rubber that will mushroom on impact. Remember that I recommended a soft rubber (Shore 50 A)

Originally Posted by shlepzig

However what may occur with sufficient composite material development you might be able to develop a blade that was not capable of shattering, and would only take a permanent bend on the end and be disposed of immediately.

That would require a core material with a relatively low elongation at yield, but large elongation at break. There are several metals that fit that description (Pb, Sn, Cu, Au, to name a few). Of those, I think that Cu would be the overall best. However, there are many polymers that also fit the description. Rubbers absorb vibrational energy much more than metal does, therefore the risk of shattering should be smaller.

Originally Posted by shlepzig

That's my thought. I don't expect to be using a plastic epee any day soon though. I certainly don't expect to hear anyone telling me how great the new plastic epees ever.

Shlep.

Have a nice time!

Peter Gustafsson

[larkmaj]

Originally Posted by keith

As to the composite blade, many many years ago the club I was at had one of those bizare blades that were a plastic core with a metal 'wrap' hard to describe but sounds similar to your idea. It felt horrrible

BIG issue. Especially condsidering this:

Originally Posted by PeterGustafsson

Rubbers absorb vibrational energy much more than metal

my 2 cents

[KD5MDK]

Originally Posted by PeterGustafsson

Hi!




The outer metal tube would take care of that.


Have a nice time!

Peter Gustafsson

I was referring to shlepzig's plastic weapons.

[keith]

Originally Posted by PeterGustafsson

Does indeed sound close to my suggestion. Was the metal really wrapped around the plastic core? If so, was is a lot of wounds of thin metal wrapped to the necessary metal thickness? I was thinking of a tube, where the material in the tube wall is not formed from thinner layers.

It was quite a thick metal but with breaks in for articulation - not a continuous metal tube with internal plastic. More that the plastic supported the outer metal layer, which in turn prevented the inner plastic core from being over flexed and weakened.

Originally Posted by PeterGustafsson

In what way did it feel horrible? Light, too whippy, too difficult/too easy to do flicks, strange balance, unusual shape of flex curve, what?

well it couldn't take a curve due to its design and it flexed equally in all directions - it really was like trying to fence with one of those plastic car antennas. Also the amount of flex was limited by the metal shell, so it flexed to its limit then 'snapped' back and wobbled around for a while.

Originally Posted by PeterGustafsson

What do you mean with "much much testing"? Was that rigorous testing in a designed for the purpose test bench, or just fencing around a great deal?

... well more like drunken students faced with a worthy challenge. ah the good old days.........

I think a vice and monkey wrench final did for it. The bits may still be lying in the back of a cupboard at EUFC.

Originally Posted by PeterGustafsson

Do you have any pictures, web links, or maybe that blade itself available?

I think it may have be a leon paul design - maybe Alex or Barry could comment if they ever produced such a thing in the '80s?

[penguin_2000]

If someone wanted to make a cool new blade, I think they should consider a blade with a hole in the middle of it running the length of the blade, and no wire slot. Anytime you need to redo a wire, you'd just pull the old one out and thread a new one in--no glue.

[DHCJr]

Been done and patented, which upset the FIE to no end.

[Mergs]

And it was the patent aspect of the blade that made the FIE 'ban' it. Small minded prats.

[Purple Fencer]

Originally Posted by Mergs

And it was the patent aspect of the blade that made the FIE 'ban' it. Small minded prats.

When was that blade...50s or 60s??

And who was the FIE serving? not fencers or armorers...it was manufacturers....

[mrbiggs]

Here's a question. Would it be possible for such a blade to break without anyone noticing? Could it crack, with the rubber holding it together?

I'd think that would be pretty bad.


On the other hand, it'd be nice to have something to keep a blade together when it breaks. Last tournament I went to, a teammate of mine broke a blade. He couldn't find the tip half. It turned out that the 8 inch piece of metal had flown off, down an entire strip (the long way), and stopped just short of the bout committee table. This could easily have injured someone...I'm actually very surprised it didn't, as tournaments are often very crowded.

[PeterGustafsson]

Hi!

Originally Posted by mrbiggs

Here's a question. Would it be possible for such a blade to break without anyone noticing? Could it crack, with the rubber holding it together?

I'd think that would be pretty bad.

From post #7:

Originally Posted by PeterGustafsson

If the metal is totally broken and the rubber core holds the pieces together, then the blade will bend in a very tell-tale way. Since the rubber is much softer than metal, almost all of the bend will happen at the break - where there is only rubber - and the two pices will be nearly straight. One will therefore see a knick on the blade. If such a blade is waved around, the distal part will quiver around the break in a very obvious manner. When the two break surfaces of the metal touch each other in such a waving, I expect that one would hear a typical metal rattling sound.

I this addresses your concern.


Have a nice time!

Peter Gustafsson

[Mergs]

Originally Posted by Purple Fencer

When was that blade...50s or 60s??

And who was the FIE serving? not fencers or armorers...it was manufacturers....

Actually it was in the 80's (or could be early 90's) and I think it came out of Britan. I thinnk we talked about it at Armorers College. I know we talked about the round blade with the hole for the wire running down the center of the blade.

[Purple Fencer]

Originally Posted by Mergs

Actually it was in the 80's (or could be early 90's) and I think it came out of Britan. I thinnk we talked about it at Armorers College. I know we talked about the round blade with the hole for the wire running down the center of the blade.

I thought Dan said it was from the 50s or 60s...and was American designed and made...

Ahhh....from your notes:

"1955 tubular blade was proposed; design was patented and FIE wouldn’t allow because of the limitations on competition of manufacturers Bella De’tuscon (from Detroit)."

[mrbiggs]

Originally Posted by PeterGustafsson

Hi!





From post #7:


I this addresses your concern.


Have a nice time!

Peter Gustafsson

Ah, that's what I get for reading too quickly. Thanks.