In
materials science,
fracture toughness is a property which describes the ability of a material containing a crack to resist
fracture, and is one of the most important properties of any material for many design applications. The linear-elastic fracture toughness of a material is determined from the
stress intensity factor (
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=1781)
) at which a thin crack in the material begins to grow. It is denoted K
Ic and has the units of
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=2101)
or . Plastic-elastic fracture toughness is denoted by J
Ic, with the unit of J/cm
2 or lbf-in/in
2, and is a measurement of the energy required to grow a thin crack.