Chemistry Reference
In-Depth Information
In Fig. 13.5, the comparison of experimental and calculated according
to the Eq. (13.4) critical strain energy release rate values is adduced, which
finds again their good conformity.
FIGURE 13.5
The relation between experimental
G
Ic
and calculated according to the Eq.
(13.4)
T
I
G
critical strain energy release rate values for PASF film samples [1].
As it was shown in chapter five, the PASF film samples there found at
tension the so-called shear deformation zone (ZD) [3] (see Fig. 5.2), through
which the stable triangular crack propagates. This crack in propagation pro-
cess maintains constant ratio of its opening d
cr
to length l
cr
and in virtue of
this is a self-similar object with dimension
D
cr
, determined according to the
Eq. (5.9).
The Eqs. (8.1), (8.3) and (8.4) have been obtained above, which allow to
estimate samples fracture stress sf
f
as a function of
D
cr
and sharp notch length
a. As it follows from the Eq. (5.9), the estimation of parameters d
cr
and
l
cr
or, more precisely, their critical values d
c
and
l
st
at the moment of instable
crack propagation start, that is, sample disastrous fracture is necessary for
the value
D
cr
calculation. Within the frameworks of dislocation analogies
application for polymers inelastic deformation description for (more details
see chapter four) the polymers yield stress value is determined as follows
[14]:
Gb
(
)
1/ 2
,
(13.5)
s
=
lC
n
Y
0
∞
cl
2
p
