Effect of Aramid Fiber Processing with Nanotubes on Shear Strength at the Matrix/Fiber Interface

The strengths of the complex thread and single filaments of the copolymer aramid fiber of the Rusar-S brand produced by JSC Research and Production Enterprise “Termoteks” (Russia, Moscow region) and microplastics based on epoxy resin (KDA brand) and prepared using the aramid fiber were determined. It was found that the treatment of the fiber surface during its formation using a suspension of multilayer carbon nanotubes produced by NanoTechCenter LLC (Russia, Tambov,) leads to an increase in the strength of the thread, determined at a clamping length of 70 mm, by 4.4%. The increase in the strength of microplastics under the same conditions was 8.2%. Estimated on the basis of the analysis of the dependence of a single filament strength on the clamping length, the value of the critical fiber length after treatment with nanotubes decreased from 0.59 to 0.43 mm, and the strength increased by 28%, from 4.98 to 6.38 GPa. This leads to an increase in the tensile strength when the matrix is shifted at the interface with aramid fiber, by 67.7%, from 72.8 to 122 MPa. The results obtained indicate the possibility of a significant increase in the strength of the composite material when using aramid fiber modified with multilayer nanotubes. It is noted that the correct application of the correlations linking the tensile strength limits of a complex thread and a microplastic made therefrom is possible only at the approximation of the experimental data using the Weibull–Gnedenko distribution. The hypothesis of compliance of experimental data for aramid fibers treated with nanotubes with the Weibull–Gnedenko distribution was verified by means of nonparametric statistics methods. Electron microscopy has shown that the fiber surface becomes rougher after treatment with nanotubes, which should lead to enhanced adhesive interaction with the matrix.