PSI - Issue 30

Aisen Kychkin et al. / Procedia Structural Integrity 30 (2020) 59–63 Aisen Kychkin et al / Structural Integrity Procedia 00 (2020) 000–000

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1. Introduction Modern composition materials provide wide possibilities for development and perfection of constructions, as due to the unique high specific elastic- strength properties and small specific mass they successfully compete with such "traditional" constructional materials as steel and different metallic alloys.

Nomenclature CNT

carbon nano tubes

EDI

epoxy hardener isomethyl-tetrahydrophthalic anhydride

iso-MTGFA

isomethyl-tetrahydrohthalic anhydride

PC М polymeric composition materials SEM scanning electronic microscopy

However, a limiting factor in the widespread use of PCM-reinforced high-strength structures is the low fracture toughness and crack resistance of the polymer matrix. The polymer matrix must ensure the achievement of maximum strength properties of the composite and meet a set of technological and operational requirements. This problem is particularly evident when using epoxy resins as basis polymer binder. It is known that exactly the protracted durability of the polymer matrix determines longevity of PC М and provides its monolithic nature in the process of exploitation under influence of different permanent and alternating loads. The decision of this problem can be either development of new polymer matrices or modification of existing ones. Thus, it should be noted that process of creation new polymeric binders is longer and more expensive as compared to their modification that is more perspective. Epoxy resin is relatively fragile polymeric material, therefore its fracture on is initiated by localization of stress on the surface or in the sample content. These places are defects that could appear in the process of shaping of the sample, for example, pores. In the process of loading of material the stress localize in the places of defects, and at exceeding of these stress there has been formation and growth of main crack that ultimately results in its fracture. The basic task of introduction of modifying additions into the epoxy matrix is increase of fracture viscidity of binder due to creation of structure effectively resisting to the origin and development of structural damage by Putilov (2002). One of the promising methods of using the physicomechanical properties of model nanotube binders (carbon nanotubes, nanofibers, nanoparticles). With their specific gravity, plasticity, and thermal dimensional stability, carbon nanomaterials are a promising tool for creating new highly efficient composite materials, as pointed by Iartsev (2014), Sokolenko (2014), Vigdorovich (2013), Vereshagin (2001), Inam (2012), Moosa 2015, Muhammad Ismail (2015) and Mohamed (2015). 2. Materials and methods The "hot" hardening binder EDI (temperature of hardening 180°C) on the basis of epoxy-diane resin ED-20 with anhydride hardener iso-MTGFA was chosen as an object of modification. Modifying addition is CNT with primary diameter of 2 nm, length more than 5mkm, mass stake of admixtures less than 15%. It was used as a super concentrate containing 10 mass% of carbon nano tubes and 90 mass% of epoxy resin of ED- 20. Introduction of concentrate was being implemented into the resin part of the binder, with the subsequent ultrasonic dispergating during 240 minutes. The influence of modifying addition CNT on elastic-strength properties of epoxy binder was estimated through the test of samples on stress (GOST 11262-80), compression (GOST 4651-2014) and impact strength (GOST 4647 80). The degree of filling of the test samples varied the from 0,05 to 0,50 mass%. Solidified samples were tested on the universal machine of model INSTRON 3369 with the maximum loading of 50kN, the dividing value of scale of 0,01 к N and the error of strength measuring ±0,1%. Structural changes were estimated on the fractographies of the surfaces of destructions, obtained through SEM.