RE: [OT]Stupid question about sloped armour

Chobham armor is a mixture of ceramic/laminate/depleted uranium. It used
the 
shear inertia of the DU, the inherent strength of ceramics, and the
"spall 
catching ability" of laminates to defeat kinetic and chemical (HEAT) 
penetrators. It is in layers to decrease the "fracturing along fractal 
surfaces" as it was crudely (yet most accurately) stated. The layers are

like a thatch weave (each in a different direction) so as to break up
the 
actual thickness of any particular "slab" of armour. It also serves to
allow 
the sliding of slab in differnt directions as a penetrator penetrates, 
basically shearing it (slug/jet/etc.) off; drastically reducing the 
penetrive power of the incoming object. LOTS of power is expended in
sliding 
slab in (relatively) lateral directions instead of actually penetrating
the 
armor. If you have ever seen chobham hit by a warhead, it looks like a 
carcass that has been shot with buck shot, until you realize how shallow
the 
penetrator actually made it into the armor.
Joe

----Original Message Follows----
From: "B Lin" <lin@rxkinetix.com>
Reply-To: gzg-l@csua.berkeley.edu
To: <gzg-l@csua.berkeley.edu>
Subject: RE: [OT]Stupid question about sloped armour
Date: Wed, 1 May 2002 10:24:37 -0600

That phenomenon is known as "spall" and most armoured vehicles are
equipped 
with spall liners to catch such fragments.  I believe that this a big 
problem in APC's with aluminum armor vs. steel armor in that aluminum
spalls 
worse than steel and so is a big debate in the weight savings vs. armor 
protection arena.

--Binhan

 > -----Original Message-----
 > From: Katie Lauren Lucas [mailto:katie@fysh.org]
 > Sent: Wednesday, May 01, 2002 1:51 AM
 > To: gzg-l@csua.berkeley.edu
 > Subject: Re: [OT]Stupid question about sloped armour
 >
 >
 > Quoting Edward Lipsett <translation@intercomltd.com>:
 >
 > > If the only benefit were the extra thickness provided by the sloped
 > > cross-section, then ceramic armor wouldn't have much to offer over
a
 > > lump of
 > > steel, would it?
 >
 > Ceramic armour fragments. You can embed a metal mesh in the
 > ceramic to retain
 > the fragments - because ceramic fractures along fractal
 > surfaces, retaining the
 > large fragments will effectively lock in the smaller
 > fragments. This is the
 > basis behind "Chobham" armour, I believe.
 >
 > So a lot of the shell's energy is spent in making cracks. Now
 > obviously, this
 > isn't good long-term (probably don't want to get hit again in
 > the same place),
 > but in the short-term, the energy is absorbed.
 >
 > Steel armour bends (which absorbs energy), but bends enough
 > to transmit energy
 > to the interior surface, which is flaked off at high speed
 > into the tank
 > interior...[1] this is because metal deforms and then
 > delaminates fairly easily
 > along crystal boundaries.
 >
 >
 > {Annoyingly we discover ceramic composite armour doesn't seem
 > to be covered in
 > the rules for Robot Wars. Mind you, the powerplant we've been
 > looking at using
 > isn't in there either...}
 >
 >
 > [1] Why isn't the tank interior coated with something to retard
these?
 >
 > ______________________________________________________________
 > _________________
 >	 Katie Lauren Lucas, Consultant Software Engineer,
 > Parasol Solutions
 > katie@fysh.org katie.lucas@parasolsolutions.com
 > http://www.parasolsolutions.com
 >

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