PSI - Issue 20

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A.K. Kychkin et al. / Procedia Structural Integrity 20 (2019) 198–205 A.K.Kychkin et al. / Structu al Integrity Procedia 00 (2019) 0 0 – 000

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Fig. 4. Temperature correlations of the relative thermal expansion along the direction of BPA reinforcement in the initial state (1), after 30 months of exposure in Gelendzhik (2), after 28 months of exposure Yakutsk (3) after 51 months of exposure in Yakutsk (4).

With the increase of the room temperature to 120±5°C in the initial and exposed BPA samples, an increase of the relative thermal expansion is observed. Such dependence is characteristic of PKM with the polymeric matrix in the glassy state by Startsev V.O. (2018) . The character of this dependence alters at 120±5°C. Accordin g to the given data obtained using the dynamic mechanical analysis by Startsev V.O. (2018) , it is here where the area of α – transition of the epoxy matrix is located. The observed increase in Tg, ∆L⁄L 0 and  is due to the prevalence of the effect of post-hardening of the BPA polymeric matrix over the effect of tension relief of the polymeric matrix at the interface with basalt fiber. 4. Conclusions The research has established that combination of rates of the compressive strength, buckling and axial tension shows an increase of strength properties of the samples after exposure to the climatic conditions of Yakutsk. The observed increase in Tg, ∆L⁄L 0 and  is due to the prevalence of the effect of post-hardening of the BPA polymeric matrix over the effect of tension relief of the polymeric matrix at the interface with basalt fiber. Thus, as t he result of the conducted research, the increase in adhesion strength of the “fiber - matrix” compounds in the process of exposure has been established, and the matrix added solidity to the material and facilitated effective usage of mechanical properties of fibers and uniform distribution of efforts between them. Acknowledgements The work has been performed within the Project of the Russian Federal Property Fund No. 18-29-05012 "Development of scientific grounds for production of new composites under impacts of abiogenic and biogenic factors in the Arctic and Subarctic areas of the Sakha Republic (Yakutia)". The authors express their gratitude to M.V. Molokov, I.S. Kurs, K.A. Hrulev, and P.S. Marakhovsky, employees of the Akimov Climatic Testing Center, All-Russia Research Institute of Aviation Materials, for assistance in our pilot studies.