PSI - Issue 20

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

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To substantiate reproducibility of temperature correlations with the thermal expansion and coefficient of the linear thermal expansion (Fig. 3), comparison of two samples, prior to and after exposure, was performed. Temperature correlations showed good reproducibility. With the increase of the room temperature up to 120±5 ° C in the initial and exposed samples of BPA, marked growth of the relative thermal expansion is observed. Such dependence is characteristic of PKM with the polymeric matrix in the glassy state.

Fig. 3. Temperature dependences of the relative thermal expansion and the coefficient of the linear thermal expansion of the initial sample of BPA – ОTR - ; KLTR - and after 28 months of exposure to natural environs ОТR exposure - ; KLTR -

The given comparative charts show that the maximal and minimal KLTR decrease after exposure, while the values of the relative t hermal expansion increase. The character of this correlation alters at 120±5 ° C. According to the data obtained applying the dynamic mechanical analysis, the glass transition temperature of the epoxy matrix is within 120-150 о С. Following insignificant con traction, further thermal expansion with the lower coefficient of the linear thermal expansion occurs. The obtained rates of the glass transition temperature are presented in Table 4, showing increased Tg. Temperature dependences of the relative thermal expansion ∆L⁄L 0 along the direction of reinforcement of BPA samples in the initial state and after exposure in Gelendzhik by Startsev V.O. (2018), and Yakutsk are presented in Fig. 4. To assess reproducibility of results, measurements of three samples in each of the states have been performed. Variability of dispersions ∆L⁄L 0 is given in stripes of various colors. Table 4.Rates of glass transition temperature depending on time of exposure.

Regulation norms and documents for tests

Tg, C 0 Initial state

BPA type

After exposure during 28 months

After exposure during 51months

Rods 6 mm in diameter GOST standard 20812 Rods 8 mm in diameter

117.0 120.0

119.5 128.6

147.4 141.4