Study of the properties of carbon plastic samples formed by the infusion method

Abstract

Traditional methods used for assessing the properties of polymer composite materials (PCM) in most cases present a generalized picture and only few of them provide more detailed information. We present the results of studying carbon fiber samples molded using the infusion method with a thickness of about 8 mm. The microhardness of the PCM matrix was measured on transverse sections in two mutually perpendicular planes, named side and end surfaces, load of a microhardness indenter being 10 g (0.1 N). The studies revealed that the microhardness of the carbon fiber matrix in depth from the front surface of the sample to opposite one varies according to a parabolic law with maximum values in the core and minimum values in the subsurface zones. Moreover, statistical calculations showed the significance of differences in the microhardness values measured in two mutually perpendicular planes. The obtained graphical dependences of the microhardness variation measured over the thickness of the samples in two mutually perpendicular planes are similar in shape, whereas the volume anisotropy coefficients are almost equal. Microscopic studies of transverse sections of the samples revealed the structure of the studied carbon fiber reinforced plastic, provided determination of the thickness of the matrix and layers of the carbon filler, as well as the layout and orientation of the carbon filler tapes. The results of microscopic studies of zones in which the matrix microhardness was measured directly are also presented along with the obtained images of thin sections with indenter prints of the microhardness tester which indicate that the measurements were carried out directly on the matrix in areas free of the filler. The use of microhardness as a differential characteristic made it possible to evaluate the properties of the matrix in each specific structural component. The results can be used in assessing the properties of molded PCM structures.