Different manifestations of toughness in polymers

The toughness of a polymer can manifest itself in a complementary manner, in several different forms. In uniaxial tension of a smooth bar, the toughness is the plastic work required in order to fracture, per unit volume, which is given by the area under the stress-strain curve as shown in Fig. 13.1, where deformation under various strain rates e is terminated when the flow stress reaches a fracture strength fff that is flaw-sensitive but otherwise relatively insensitive to the deformation rate. 

In a notched bar, deformed in tension or in bending, under slow or impact rates, the toughness is the plastic work required in order to fracture unit width of the bar, as a special form of a fracture-mechanics experiment. 

1 In a blend having a well-defined flaw-governed fracture strength or the reduced plastic resistance at a low strain rate t results in higher tensile toughness than with a high strain rate 2- 

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