Study of the dimensional stability of a carbon-fiber-reinforced plastic by the method of laser interferometry

Abstract

1. 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. 2. 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). 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. 4. 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. 5. 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).