Page 155 - Fiber Fracture
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140 P.K. Gupta
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Fig. 3. SEM images of an E-glass fiber fracture surface showing a platinum inclusion in the bulk. The fiber
strength was 745 MPa (Gupta, 1994).
from the platinum crystal by thermal stresses. However, this explanation is not entirely
satisfactory because the expansion coefficient of platinum is larger than that of the glass
which implies that the glass will go in compression. It is possible that the crack forms at
about the glass transition temperature when the melt solidifies into glass and therefore
structural relaxation around the glass transition has to be taken into account to properly
account for the thermal stresses. Similar studies have been reported in the case of optical
fibers (Mecholsky et al., 1979; Chandan et al., 1994).
Inclusions are sometimes observed buried in the surface of fibers, indicating a dirty
fiber drawing environment as their most likely source. Impact by dust particles at low
temperatures (below glass transition temperatures) causes only micro-indents and the
