ISO 29221:2014规定了一种测定聚合物材料平面应变止裂断裂韧性Kla的方法，该方法通过使用侧槽、裂纹线楔形加载的紧凑拉伸试样来获得具有令人满意裂纹前沿的平面拉伸分离的快速裂纹止裂段。ISO 29221:2014采用静态断裂分析确定裂纹停止后短时间内的应力强度因子。该估计值表示为Ka，并且当满足某些尺寸要求时，测试结果提供了聚合物的平面应变止裂韧性的估计值，称为Kla。试样尺寸要求提供了足够大的平面内尺寸，以允许通过线弹性分析对试样进行建模。

ISO 29221:2014 specifies a method for the determination of the plane-strain crack-arrest fracture toughness, K_la, of polymeric materials by using a side-grooved, crack-line-wedge-loaded compact tension specimen to obtain a rapid crack run-arrest segment of flat-tensile separation with a satisfactory crack front. ISO 29221:2014 employs a static fracture analysis determination of the stress intensity factor at a short time after crack arrest. The estimate is denoted as K_a and when certain size requirements are met, the test result provides an estimate, termed as K_la, of the plane-strain crack-arrest toughness of the polymer. The specimen size requirements provide for in-plane dimensions large enough to allow the specimen to be modelled by linear elastic analysis.