IMPACT TOUGHNESS - Fractal Mechanics of Polymers - page 212

FIGURE 10.15 The dependence of critical strain energy release rate G Ic on parameter ( d f -
4) in logarithmic coordinates for HDPE samples. The designations are the same, that i n Fig.
10.14 [ 47]
Hence, the adduced above data have shown the physical grounds for of-
ten cited in literature correlations of impact toughness A p and fracture sur-
face fractal dimension d fr , at any rate for polymers. And on the contrary, such
grounds exist for correlations of plasticity characteristics ( G Ic or g) and d fr .
The Eq. (10.27) gives the possibility of the value G Ic prediction, since d fr ,
as it follows from the Eq. (4.50), is a function of structure characteristic -
Poisson's ratio n. In its turn, G Ic and critical defect characteristics knowledge
gives the possibility of A p prediction [47].
As it is known [54], a polymers number exists, which do not break down
in impact tests at samples without notch usage. As the conducted experi-
ments have shown [55], impact energy increase in four times (from 1 up
to 4 J) does not change the situation. The two main groups, to which the
polymers of such type belong, can be distinguished. The semicrystalline