Application of the impact microindentation method for estimation of the mechanical characteristics and defects of the structure of carbon-base composites

The problems of measurement the physical and mechanical properties of carbon materials by the dynamic microindentation method are considered. The description of the gage design for measurements is given. This gage allows creating different initial energy for straining of the material tested. It is shown that the design of the gage and the device allows testing both integral (in a large volume of straining) values of the hardness and the elastic modulus, and values of these characteristics for different structural components of the carbon-carbon composites materials: carbon rods and pitch. The obtained data confirms the possibility of using the accepted elastoplastic model of straining of the materials tested for the determination of the elastic modulus and hardness. The ratio between the dynamic and static characteristics is derived. Samples from such carbon materials as pyrolitic graphite, silicified graphite, graphite PPG, coal-filled PTFE and polyamide have been certified. Using these samples it was shown that the dynamic indentation method allows determining the elastic modulus in the range from 0.5 to 100 GPa and the hardness of indentation in the range from 20 to 550 MPa with an error not exceeding 10 %. It is established that the developed measuring device can be used to establish the presence of defects like "delamination". The influence of the depth of the defect placement on the measured parameters is shown.

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