Toughness is defined as what?

• A. Elastic modulus
• B. Ability to resist fracture and crack propagation
• C. Yield strength
• D. Hardness

Answer: (B)

Toughness describes a material’s ability to absorb energy and resist fracture, especially in the presence of a crack. It reflects how well a material can withstand crack initiation and, more importantly, crack propagation, combining strength and ductility. In practice, toughness is measured by the energy absorbed during fracture (such as in Charpy or Izod impact tests) or by the area under the stress–strain curve up to failure. This makes toughness different from elastic modulus (stiffness and elastic deformation), yield strength (the stress at which permanent deformation begins), and hardness (resistance to indentation). Because it directly captures resistance to fracture and crack growth, the option describing the ability to resist fracture and crack propagation best defines toughness.