断裂韧性（Fracture toughness）反映了结构阻止宏观裂纹失稳扩展能力，是结构抵抗裂纹脆性扩展的参数。它和材料本身特性、结构几何形状以及裂纹形状相关的参数。一般用于表征断裂韧性的参数有积分J、应力强度因子K的临界值。断裂韧性用于大型的结构（如：船体）的断裂事件研究。大型结构往往在很低强度的情况下发生断裂。为了解决这个问题，发明了表征脆性断裂的应力强度因子K。后又发展出了J积分。进而产生了T参数、Q参数等表征应力场非标准特性差的参数。 K=Yσ√(πa)

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 () at which a thin crack in the material begins to grow. It is denoted K_Ic and has the units of or . Plastic-elastic fracture toughness is denoted by J_Ic, with the unit of J/cm or lbf-in/in, and is a measurement of the energy required to grow a thin crack.