PSI - Issue 30

A.K. Kychkin et al. / Procedia Structural Integrity 30 (2020) 173–178 Kychkin A.K., Struchkov N.F., Vinokurov G.G. et al. / Structural Integrity Procedia 00 (2019) 000–000

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describes the experimental data for small diameters of basalt fiber reinforced polymers - D = 6 mm and D = 8 mm. At the same time, with a significant increase in the diameter (up to 20 mm) and the state of the composite material after exposure, the linear relationship (1) shows significantly exceeded values of the average open porosity - up to 2.7% for D = 20 mm. This is due to the fact that during long-term climatic tests of basalt fiber reinforced polymers of large diameters, degradation processes occur, depending on the bulk physical and chemical state of the materials, and not only on the state of the outer surface layer. In this case, the average porosity can be described by a more complex relationship than a simple linear expression (1) Thus, the estimation of the average porosity of basalt fiber reinforced polymers by linear dependence (1) should be used for small diameters of basalt fiber reinforced polymers. It is also assumed the initial stage of exposure of composite materials during climatic tests. 4. Conclusion The change in the structure of basalt fiber reinforced polymers was studied during climatic tests after 51 months in the North. In the initial state of delivery, the structure of basalt fiber reinforced polymers is rather homogeneous and monolithic: a dense content of reinforcing basalt fibers has been revealed; only individual pores up to ~ 10–20 microns are observed. After climatic tests, the homogeneity and solidity of basalt fiber reinforced polymers are noticeably disturbed, the number of pores in the cross-section of basalt fiber reinforced polymers increases by almost ~ 1.5 times. It was found that degradation of the basalt fiber reinforced polymer leads to a significant increase in its open porosity: for reinforcement with a diameter of 6 mm – ≈ 4 times, for reinforcement with a diameter of 8 mm – ≈ 2.5 times. Estimated calculations of the average porosity of basalt fiber reinforced polymers at their uniform degradation from the outer surface under the influence of the external environment have been carried out. It is assumed that the average porosity of the basalt fiber reinforced polymer is proportional to the number of reinforcing fiber rovings in the degraded annular layer. This leads to a linear dependence of the average porosity on the cross-sectional diameter of the basalt fiber reinforced polymer. The linear dependence of the average porosity more satisfactorily describes the experimental data for small diameters of basalt fiber reinforced polymers - D = 6 mm and D = 8 mm. With a significant increase in the diameter (up to 20 mm) and the state of the composite material after exposure, the linear dependence shows the exceeded values of the average open porosity - up to 2.7% for D = 20 mm. Thus, the estimation of the average porosity of basalt fiber reinforced polymers by linear dependence should be used for basalt fiber reinforced polymers of small diameters and for the initial stage of exposure during climatic tests. Acknowledgements

The reported study was funded by RFBR according to the research project № 18-29-05012. References

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