Composite polymer reinforcement (CPA) is increasingly applied in modern building industry. The areas of application of CPA are determined by the special properties of this material, such as stability in aggressive environments, magnetic inertness, low thermal conductivity. Glass composite reinforcement (GCR) are in the greatest demand, due to the availability of chemically resistant fiberglass and wide industrial elaboration of the GCR manufacturing technology. However, the relatively low modulus of elasticity, which does not exceed 50 GPa, is an obstacle to its application in concrete structures, that operate on bending. Proposed solution for increasing of modulus of elasticity of composite polymer reinforcement is the creation of combined reinforcement based on low-modulus and high-modulus fibers impregnated with epoxy polymer binder.Achieving the goal made it possible to establish trends for increasing the modulus of elasticity of composite reinforcement based on glass and carbon fibers with the use of an epoxy polymer matrix by evaluating the optimal ratio of the components of the epoxy binder within the framework of the well-known technology of the fillerless manufacturing method. It has been established that one of the methods of increasing the modulus of elasticity of composite reinforcement is the modification of the thermosetting polymer binder with a reactive diluent - diglycidyl ether of the epichlorohydrin homooligomer. The action of the latter is based on its ability, in small quantities, to influence the structure of the matrix epoxy anhydride binder net, ensuring a relatively high yield of the sol fraction under the conditions of a shortened period of hardening time, provided for by the technology of obtaining composite reinforcement. It is shown that in the presence of hybrid reinforcement and the optimal amount of the modifier, it is possible to achieve an elastic modulus of 50 GPa, which, in our opinion, is due to the implementation of increased adhesive contact with glass and carbon fibers and ensuring the necessary monolithicity of the polymer composite. Keywords: composite polymer reinforcement, glass and carbon fiber, modulus of elasticity, adhesive strength.

The scientific work is devoted to the improvement of the calculation methodology of reinforced concrete elements, using verification of the FRP delamination prevention, during structures strengthening with a system of composite materials (SCM) from various fibers types. During strengthening of reinforced concrete elements with composite material systems, the role of adhesion between concrete and FRP is of great importance due to the fragility of the failure mechanism due to delamination (loss of adhesion). The adhesion strength is generally much higher than the tensile strength of the concrete, so delamination always starts in concrete itself with the separation of FRP layer of different thickness. According to the load-bearing capacity requirements, such a failure mechanism should not precede the failure of the strengthened element during bending or shear. To solve the problem of possible strengthening delamination of composite materials systems, it is necessary to consider different failure modes of FRP. Due to imperfection of domestic building codes, a detailed analysis of the solution to the problem of FRP delamination was carried out in accordance with the recommendations of a number of foreign regulatory documents (ACI, CNR, FIB). The main failure modes, with subsequent initiation of delamination of FRP material from concrete base, are systematized, namely: FRP delamination due to surface irregularities, separation of FRP due to shear cracks, longitudinal shear stresses in the yield zone, excessive deformations in FRP material (FRP rupture), longitudinal shear stresses near the FRP edges, failure in anchoring (fixing) zone of FRP material. Six criterions are proposed that need to be verified during design of structures strengthening systems with FRP materials. During formulation of specified criterions, the main theoretical aspects necessary for application in structural calculations of the studied connection are given. The results of research can be used in future during the design of structures joints strengthening with systems of composite materials based on carbon fibers, glass, aramid. Keywords: system of composite materials, external reinforcement, FRP strengthening, reinforced concrete, failure mode, calculation, delamination.

The scientific work is devoted to the improvement of the calculation methodology of bending reinforced concrete beam elements strengthened with a system of composite materials (SCM) from carbon fiber. During the calculation based, on the limit state method, the recommendations of foreign standards (ACI 440.2R-02) were taken into account. The determination of the cross-sectional area of the external reinforcement was carried out by an iterative method, setting some initial value with subsequent adjustment based on the results of moment strength calculations. To prevent possible debonding of SCM from the concrete base, the coefficient ΚM, with which it is possible to limit the achievement of the limit value of tensile deformation (rupture) of carbon fiber, was introduced to the general calculation. Based on the results of the calculation, the necessary geometric parameters of the strengthening material (width, thickness, number of layers) were established, with the specified normative strength and modulus of elasticity, which allows to significantly increase the strength of the studied cross-section with full use of the external reinforcement system strength. The results of this research can be used in future during the design of structures joints strengthening with systems of composite materials based on carbon fibers, glass, aramid, etc.