Technical help needed. Wong, please read!

Evil Sadistic Bastard · Post by **Evil Sadistic Bastard** » 2002-10-04 01:18am

Yo, Wong, I was just thinking - how effective would a breastplate of diamond (approx. 5 mm thick, laminated inside multiple layers of Kevlar in smaller segments for mobility) be against small arms fire?

I know penetration is not everything (assault round impacts HURT, by the way) but how good would it be? My chemistry teacher says that diamond would be useless because of some ionic cleavage stuff.

IIRC, that only applies to ionic bonding (cleavage only occurs because the ionic lattice is mechanically disrupted and the similarly charged ions are brought together) and not the giant covalent bonding of diamond, so I am quite confused.

I felt that asking a physics graduate who majored in fracture mechanics would be a pretty good move towards clearing this up.

Thanks.

Post by **Sea Skimmer** » 2002-10-04 01:25am

I'd expect the diamond to shatter under the impact, and the fragments to cut through the Kevlar backing. Stick to steel and ceramic plates, or just buy an APC for protection, it would be cheeper.

Evil Sadistic Bastard · Post by **Evil Sadistic Bastard** » 2002-10-04 01:29am

I personally wouldn't want to put myself in a position to find out... Better to let the other poor fool do the dying...

And APCs aren't exactly my thing. THe M2 Bradley is better, though not by much.

TrailerParkJawa · Post by **TrailerParkJawa** » 2002-10-04 01:34am

I also think diamond would shatter. The hardness of a diamond does not automatically translate into ability to resist a blow from a bullet.

Besides, if you have that much diamonds, you should be using them to get women!

Post by **Sea Skimmer** » 2002-10-04 01:40am

Evil Sadistic Bastard wrote:I personally wouldn't want to put myself in a position to find out... Better to let the other poor fool do the dying...

And APCs aren't exactly my thing. THe M2 Bradley is better, though not by much.

You call that weak ass thing an IFV? The T-84 Urban assualt tank, with built in compartment for three infantrymen, now thats an IFV!

Normally you test such things on dummies and pigs before you deploy them for combat. An IFV is technically an APC , it's a subtype which has grown to be thought of as a separate type, but really isn't.

Evil Sadistic Bastard · Post by **Evil Sadistic Bastard** » 2002-10-04 01:48am

Skimmer, IIRC the Bradley had room for up to 6 up to people, who can all shoot out the side. Accuracy goes to shit, but it should keep their heads down.

And the T-84... I've never heard of that. Haven't been doing enough reading, I guess. Got any specs?

TrailerParkJawa · Post by **TrailerParkJawa** » 2002-10-04 01:49am

Depends on the version of the Bradley. The scout version only carries 2-3 troopers. I think the full infantry version carries 6.

If IIRC, the gun ports are not used.

Post by **Sea Skimmer** » 2002-10-04 02:16am

All models of the M2 can transport 7 infantrymen. All men have firing ports, and the early models had special firing port weapons which where basically short M16's, the full-length gun was to big for the task. However I believe the latest M2 variant deletes these to provide more space for ammo and better arrangements for it storage. Among other things I believe there are now racks under the floor to keep multiple anti tank rockets for the infantry, before there was no real place to put anything bigger then an M-72.

The M3 Calvary Scouting vehicle carries two dismount scouts with no firing ports.

Both models have three man crews.

SWPIGWANG · Post by **SWPIGWANG** » 2002-10-04 05:46pm

dimands are a awful material for armor. The cracks grow like crap when it forms and it has no ductility to absorb energy.

Post by **Darth Wong** » 2002-10-04 06:01pm

The energy absorption of a material is the area under its stress-strain curve. Diamond has almost no strain before failure, so even though its hardness is high, its energy absorption is pathetic.

You need both hardness (rigidity) and toughness (energy absorption) in armour. Take one away, and it's useless. A diamond vest would shatter. It doesn't matter whether it's ionic or covalent; the problem is the innate rigidity of its crystal structure. It is a true 3-d crystal, meaning that unlike a typical metallic crystalline lattice which is just stacks of layers on top of each other, a diamond orders itself in such a manner that it cannot easily be reconfigured. Hence, enough force to reconfigure the lattice simply causes it to shatter along its natural cleavage planes.

When it comes to ductility, microstructure is king.

Evil Sadistic Bastard · Post by **Evil Sadistic Bastard** » 2002-10-05 10:12pm

Thanks, Wong, and everyone else. Small wonder everyone uses metal for armor.

And Wong, could you explain the concept of "natural cleavage plates" to me? Your ideas intrigue me and I wish to know more.

Post by **Mr Bean** » 2002-10-05 10:24pm

And Wong, could you explain the concept of "natural cleavage plates" to me? Your ideas intrigue me and I wish to know more.

Hmm its been awhile but I'll take a Vauge stab and say that Natural Cleavage plates are "Built in" places where divides and creases exist that make it easier for you to break somthing

IE if you put a farature in a rock then drop the rock, its likley to break around the Fracture rather than around anywhere else as that place is naturaly weaker than the rest(Well not in THIS example but in the real world it basicly means that, naturaly weak spots)

EmperorChrostas the Cruel · Post by **EmperorChrostas the Cruel** » 2002-10-09 12:57am

I thought that "natural cleavage plates" were related to breastfeeding!

Master of Ossus · Post by **Master of Ossus** » 2002-10-09 01:00am

Actually, the best armors nowadays (that individual soldiers wear, not the ones on tanks and AFV's) are usually made of ceramics. They offer light weight and very good resistance compared with most metals.