Re: what material has the highest resistance to impacts

For a material to exhibit high impact resistance it must combine high
strength and toughness.  The charpy impact test does not give usable values
of impact strength however it provides us with relative impact strength and
also it allows us to determine the brittle-ductile transition of a
material.  The brittle-ductile transition temperature is important because
brittle materials have lower impact resistance than ductile one.  Therefore
if a material is tested at a temperature where it is brittle its impact
resistance will be lower than if it was tested at a temperature where it is
ductile.

The materials with the highest impact resistance that I have found were
polymeric, including Rislan, Pebax, Ultramid and Vestamind (all are
tradenames).  A lot of them did not even break using conventional testing. 
The names and values of impact resistance of those polymers can be found
using the search found in: http://www.matls.com/ (which is a free
online materials property database)

Steels have a lower impact resistance strength to polymer.  Also they have
a higher density and thus making their use in bullet proof armour less
attractive than polymer.  The steel that I found with the highest impact
resistance is called Gall-Tough PLUS stainless (annealed) its composition: 

C <0.15%
Mn 4-8%
Ni 6-10%
Si 2.5-4.5%
Cr 16.5-21%
Mo 0.5-2.5%
P <0.04%
N 0.05-0.35%
S <0.04%
Fe 62%

(all are in weight%)

I hope this is of help to you.

Regards,
Jeries