|MadSci Network: Engineering|
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
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