Stress Measurements in Graphite Fibers by Laser Raman Spectroscopy.
Rept. for 1 Sep 86-31 Aug 87,
MASSACHUSETTS INST OF TECH CAMBRIDGE
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Heat treated benzene derived graphite fibers have been characterized by Raman spectroscopy as a function of applied uniaxial tensile stress. Linear shifts are observed in the frequency of the Raman lines as a function of the applied stress. Thus it is shown that laser Raman spectroscopy provides a powerful nondestructive technique for monitoring the local stress variations near the surface of carbon fibers. The Raman microprobe used in this experiment provides approximately two micrometers spatial resolution within the optical skin depth. This spatial resolution is much higher than conventional techniques such as x-ray analysis which typically has a spatial resolution of several millimeters. Stress measurements in semiconductors such as Silicon, Germanium and Gallium Arsenide by Raman spectroscopy have been previously reported. Since benzene-derived graphite fibers are typically between ten and 20 micrometers in diameter, Raman spectroscopy has been used to examine the stress variation within the optical skin depth approximately 600 Angstroms for light scattering at 4880 Angstroms of single carbon fibers. Keywords Stress, Strain, Characterization, Carbon fibers, Raman microprobe studies, Stressed carbon fibers.
- Refractory Fibers