Page 158 - Fiber Fracture

STRENGTH OF GLASS FIBERS 143

INTRINSIC STRENGTH OF GLASS FIBERS - EXPERIMENTAL RESULTS

The strengths of pristine fibers have been much studied in the literature. The work
on E-glass has been reviewed by Gupta (1983, 1988). Not much new has been reported
since about 1990 on E-glass pristine fiber strength and most new results have come from
the large amount of work reported on silica fibers. There have been several reviews of
the work on silica fibers (Kurkjian et al., 1989, 1993).

Room Temperature Intrinsic Strength, S*(RT)

E-glass Fibers

While high strengths had been reported earlier, Thomas (1960) was the first to measure
the intrinsic strengths of E-glass fiber (and probably of any glass). This is best indicated
in Fig. 5 which shows the average strength as a function of fiber diameter. It is clear
from this figure that all previous efforts measured only extrinsic strengths. In a later
work Thomas (1971) showed that the strength was constant up to diameters as large as
50 pm. The COV corresponding to the strength values reported by Thomas (see Fig. 5)
is about 1 % which, even to this day, is extremely good.

xi 03

500

h
N
n 400
v
s
m
S
F
5 300
-
a,
.-
cn
c
a,
I-

' 100 O ° C
0 20 40 60 xi 0-5
Fibre diameter (in.)
Fig. 5. Strength-diameter relationships for glass fibers: 6, Thomas (1960): 2-5, Otto (1955); 1, Anderegg
(1939). (Figure from Thomas, 1960.)