Difference between hardness and toughness:
Toughness describes how much total energy has to be used before a material breaks. If the material takes a lot of energy (it may change shape) before breaking, then it is a tough material. If only a little energy is needed to break the material it is weak or brittle
Hardness describes how much energy it takes to deform (stretch, compress, bend, etc.) a material. If the material takes a lot of energy to change only a little, it is said to be hard. Conversely, if only a little amount of energy is needed to make a lot of shape change, then the material is soft. Metals would be considered hard, chewing gum would be soft. source:
http://www.newton.dep.anl.gov/askasci/mats05/mats05189.htm
Toughness describes how much total energy has to be used before a material breaks. If the material takes a lot of energy (it may change shape) before breaking, then it is a tough material. If only a little energy is needed to break the material it is weak or brittle
Hardness describes how much energy it takes to deform (stretch, compress, bend, etc.) a material. If the material takes a lot of energy to change only a little, it is said to be hard. Conversely, if only a little amount of energy is needed to make a lot of shape change, then the material is soft. Metals would be considered hard, chewing gum would be soft. source:
http://www.newton.dep.anl.gov/askasci/mats05/mats05189.htm
