Physical Patterns of Deformation and Destruction of a Two-Layer Composite Compound Polymer - Nanocrystalline Metal Film under Local Loading by the Vickers Pyramid

The purpose. Determination of the mechanical properties of two-layer composites surface coating hard brittle films - elastic polymer, as well as the development of mechanical testing methods.

Methods. Mechanical tests of a multilayer composite compounds without carbon nanotubes and reinforced with carbon nanotubes were carried out by the method of local loading. The dependence of microhardness Hv on the magnitude of the load and the depth of indentation is determined.

Results. The method of creating multilayer composite compounds is described. The values of microhardness for composite compounds are determined. The specificity of the standard method of mechanical testing for a multilayer composite compound is revealed. 

Conclusion. The addition of nanotubes to the polymer composite has a weakening effect, which is associated with the formation of nanotube conglomerates, around which pores are formed. It is possible to achieve a growth of strength with an increase in the dispersion of carbon nanotubes. At low loads not exceeding 1 N, the microhardness is determined by the influence of a thin and hard nanocrystalline film. Therefore, the usage of a standard scheme of mechanical tests for loads from 0.5 N to 1 N allows us to define the value of microhardness of thin composite film and polymer. If loads are more than 1.5 N, it is more correctly to say, that we define the value of microhardness of the composite film, polymer and the second nanocrystalline film. If the load increases 1.5-2 N, it is correct say, that we define the microhardness of the composite as a whole. A method for determining the micro-fracture viscosity coefficient of two-layer composite compounds based on determining the total length of cracks on a surface area S, with an imprint from the Vickers pyramid in the center, is proposed.

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