Toughness is best described as:

• A. The maximum stress a material can withstand before fracture.
• B. The ability of a material to resist fracture without cracking.
• C. A measure of the energy a material can absorb before fracture.
• D. The elastic modulus divided by density.

Answer: (C)

Toughness is best described as the energy a material can absorb before fracture. It reflects how much work the material can do to deform and dissipate energy before failing, so it combines strength and ductility. On a stress–strain curve, toughness is the area under the curve up to the point of fracture, i.e., energy per volume (J/m^3). That means a material that can withstand a high load and deform a lot will have high toughness, while a brittle material that breaks with little deformation will have low toughness. Tests like Charpy or Izod quantify this energy absorption.

This differs from the maximum stress a material can withstand before fracture, which is a measure of strength (the peak stress) and does not account for how much the material can deform. It also differs from fracture toughness, which concerns resistance to crack initiation and propagation in the presence of flaws, not the overall energy absorbed to failure. And it isn’t given by the elastic modulus divided by density, which relates to stiffness per weight rather than energy absorption.