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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samples of polyester matrix basalt plastics absorbed up to 2% of normal and sea water at room temperature. Tensile strength, bend and impact elasticity decreased by 50 – 60%, notably, for samples with basalt fibers processed by H2SO4 and NaOH solutions prior to production of composites. Similar mechanical properties of basalt plastics reinforced with chopped roving, fabrics or uniaxially oriented continuous fibers have been compared with coal plastics and fiber-glasses of unsaturated polyesters, epoxyphenolic and phenol formaldehyde matrixes by Chikhradze N.M. (2012). According to data of 12 month climatic tests in the South Caucasus, strength reduction in agreement with the type of the polymeric matrix and the value of the applied tension has been observed. Processes of aging have been noted to develop on the surface of samples, but no experimental data to substantiate this statement have been provided. It is well known that processes of climatic aging in a number of cases make decisive impacts on changes of mechanical properties of materials and products, notably, during their operation in cold climates. The acute problem of use of BPA in construction is verification and substantiation of maintenance of properties in the process of long-term operation under various climatic conditions. However, in the literature reviewed, there are no data on alterations of BPA properties relevant for construction un-der natural environmental impacts of extremely cold climates. The objective of this work is to define changes of major physical and mechanical properties of basalt plastic reinforcement under impacts of abiogenic factors of extremely cold climates of Yakutia 2. Methods To assess changes of properties, BPA rods of a 6-8 mm diameter periodic profile were exposed on open stands under the extremely cold climate of Yakutsk. The average annual air temperature in Yakutsk makes - 10.2 °C. The city of Yakutsk is loc ated in the area of markedly continental climate with very cold winters and rather hot and short summers. The minimal registered temperature is - 64.4 °C. The annual amplitude of temperatures between the highest and lowest values exceeds 100 °C. In Yakutsk in winter, airborne water vapor crystallizes and forms fogs at temperatures below - 40 °C. The average speed of wind is 1.8 m/s, while the average annual relative air humidity is 68%. The loss of rainfall makes 237 mm a year. A dose of the total annual radiation in Yakutsk is 3680 MJ/m2. The daily thermal gradient in autumn - spring makes 25 °C ,with transition through a zero mark. For tests, BPA- unidirectional basalt plastic rods with a periodic profile of 6-8 mm diameter were produced using the equipmen t “Struna” on the basis of the basalt roving RBN 13 -2400-4S produced by the join-stock company “TBM” in Yakutsk, according to the standards 2296 -001-86166796-2013 "Nonmetallic composite reinforcement from basalt plastic". The initial binder based on epoxy resin ED-22 hardened with isomethyltetrahydrophthalic anhydride (iso-MTGFA) in the presence of accelerator 2,4,6-tris (dimethylaminomethyl) of phenol (UP-606/2) was prepared according to guidelines RTP-SP2-20994511-1999T. Tensile strength, bend and impact elasticity tests are major and the most common methods of control of mechanical properties of polymeric composites. The tests were carried out using the universal testing machine of Z600 Zwick/Roell. The test of ABK samples for axial tension and compression was carried out according to GOST standards 31938-2012 " Composite polymeric reinforcement for concrete structures" (ISO 10406-1:2008, NEQ). Bending tests were carried out according to standards TU 2296-00120994511-04. Measurement of KLTR and relative thermal expansion of samples was carried out using the TMA 202 "NETZSCH-Geratebau GmbH" thermomechanical analyzer at a heat rate of 5 K/min in the medium of helium duct at a speed of 70 ml/min. Measurements were conducted in accordance with national standard ASTM E 831 "Definition of the temperature coefficient of the linear expansion of solid materials using the thermomechanical analysis" within - 100 + 200 °C temperature range. Parallelepipeds of 20 mm height and with a section of 4х4 mm were cut out fr om the given rods. End faces of the samples were ground using the grinding machine with deviation from plane parallelism not greater than 0.1 mm. Excludable systematic errors were considered at calibration of relative dilatometers according to standards. The relative error of measurements made 3% at 0.95 confidence level over the whole range of operation temperatures. Average arithmetic results of KLTR observations, wherein amendments had been introduced to exclude systematic