 Schmitt and Bucknall developed the mechanism of rubber toughening according to the existence of stress whitening and shear yielding when the stress is lower than fracture strength.They proposed that the rubber particles served as the center for stress concentration, hence initiated the brittle-ductile transformation and yielding of the matrix material.To specify, yielding happens in the form of crazing or shear band, which can consume a large portion of deformation energy.