Study of the dimensional stability of a carbon-fiber-reinforced plastic by the method of laser interferometry
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The method of laser interferometry is the most sensitive, precise, and reliable method for measuring microscopic changes in the geometric dimensions of specimens of carbon-plastic, since the measurements are scaled to a natural length — fractions of the wavelength of the laser radiation.
The drift of the geometric dimensions of "dry" and "moist" specimens of carbon-plastic under natural conditions occurs during the first several hours. The sign of the drift differs on different specimens: dry specimens are saturated by moisture and the linear dimensions increase; drying takes place in the case of the moist specimens, i.e. the linear dimensions decrease (see Fig. 3).
Preliminary thermocycling stabilizes the geometric dimensions of carbon-plastics and improves their dimensional stability. The moistening-drying cycle does not increase the dimensional stability of the composite.
The location of the reinforcing fibers in the surface layers affects the dimensional stability of a carbon-plastic only in the case of dry specimens. Less drift occurs in specimens in which the fibers are longitudinally oriented.
Specimens that are stored for a long time and then chemically dried to a constant mass have the same dimensional stability as freshly prepared thermocycled specimens (curves 2–4 and 7, 8 in Fig. 3).
KeywordsRadiation Surface Layer Laser Radiation Natural Condition Geometric Dimension
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