Page 160 - Fiber Fracture

STRENGTH OF GLASS FIBERS 145

HISTOGRAM
2.5
-
h
.
z
0
(0
Y c+
4 E -2.5 -
n 1 +
0.20-
8 v
t
1
' ' ' In " ' ' '
0.00 -7.5

HISTOGRAM
WEIBULL PLOT
7
2.5
0.401 I8 t

t fl I t

' 111 ' ' ' ' ' -7.5
0 500 1000 4.0 5.5
STRENGTH, (Kpsi) Ln S, (Kpsi)
Fig. 8. Weibull plot for the room temperature extrinsic strength of E-glass fibers (Gupta, 1994).

S-glass Fibers

There are not many data available for S-glass fibers. Gupta (1985) has reported an
average value of 5.1 GPa at room temperature for S-glass fibers of about 9 km in
diameter and 5 cm gauge length. However, no effort was made to check the diameter
dependence of strength. Lowenstein and Dowd (1968) have also reported strength
measurements of S-glass fibers in ambient conditions. Their highest reported strength
is about 5.8 GPa for a 5 pm diameter fiber. These results also show a decrease of
strength with increase in fiber diameter indicating that these strengths are extrinsic.
Since Gupta's strength values are smaller, his strength values must be extrinsic as well.