Chemistry Reference
In-Depth Information
FIGURE 8.8
The optical microphotographs block, showing ZD and stable crack evolution
in blend PAASO/PC with PC content 20 mas. % sample. Enlargement 22ยข [14].
Now the equation for the fracture stress sf
f
estimation as a function of
D
cr
and sharp notch length a can be obtained. In Ref. [4], the following defini-
tion of stress intensity factor
K
I
as a function of
D
cr
was given:
a
a
2
-
D
(
)
KD
=
C
D
,
a
=
cr
,
(8.3)
I
cr
2
cr
where
C
is coefficient, dependent on crack form details and external loads
concrete distribution.
One more estimation
K
I
(
D
cr
) method the Eq. (8.1) gives. Assuming
K
I
(
D
cr
) as polymer constant [16] and equating the Eqs. (8.1) and (8.3), let
us obtain [14]:
(
)
1/ 2
D
-
3/2
s
~
a
D
.
(8.4)
cr
f
cr
The Eq. (8.4) has three characteristic features. Firstly, it shows, that at
D
cr
< 1.5 sf
f
will be decreased at a enhancement and at
D
cr
> 1.5 will raise. If
to compare these predictions with the data of
Fig. 8.9
and Refs. [1, 2], then
one can see, that they are fulfilled completely. Secondly, at
D
cr
= 1.5 s
f
must
not depended on notch length, that is also c
onir
med experimentally [1, 2].
And thirdly, at
a
= 1 mm the condition sf
f
~
c
D
should be fulfilled. As the
