PSI - Issue 40

I.A. Morozov et al. / Procedia Structural Integrity 40 (2022) 314–320

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I.A. Morozov et al. / Structural Integrity Procedia 00 (2022) 000 – 000

Fig. 4. AFM images of surfaces after fatigue loading: polyurethane activated in argon plasma (a) and treated in Ar/C 2 H 2 plasma for 30 (b), 60 (c) and 120 (d) seconds. The axis of deformation is horizontal.

Fig. 5. AFM images of surfaces after fatigue loading in stretched state (deformation 50%): polyurethane activated in argon plasma (a) and treated in Ar/C 2 H 2 plasma for 30 (b), 60 (c) and 120 (d) seconds. The axis of deformation is horizontal. The insets in (b) and (d) show enlarged fragments of topography and the corresponding elastic modulus maps. The stretched material after treatment for 60 s showed no formation of cracks (Fig. 5c): only open transverse folds and longitudinal folds are visible on the surface. This effect can be explained by the optimal ratio of the elastic moduli of the hard and soft areas of the surface: when treated for 30 s or 120 s, a predominantly soft or hard coating is formed (see Fig. 3b); when treated for 90 s, the mechanical heterogeneities of the surface, by analogy with the filler in a polymer composite, providing the reinforcement of the coating. With further increase in the duration of acetylene treatment, a hard carbon coating will form on the surface, cracking even at small deformations. 4. Conclusions The elastic polyurethane, a synthetic two-phase polymer, was investigated. The surface of polyurethane is covered with a low-molecular-weight soft homogeneous nanolayer that hides the structural and mechanical heterogeneities of the polymer. In this regard, the surface was pretreated with argon plasma (etching of the upper