Eddy Current Non-Destructive Characterization of Carbon Fiber Reinforcement Composites Considering Capacitive Effect

This paper presents a modelling procedure to take into account the capacitive effect at high frequencies, in Eddy Current Non-Destructive Characterization (EC-NDC) of Unidirectional Carbon Fiber Reinforcement Composite (UD-CFRC) rods. To simulate the complete EC-NDC systems, first, the multilayer circular air coil is physically modeled by a finite element (FE) axisymmetric eddy current model coupled to equivalent RL circuit. Each layer of the coil is represented by an equivalent resistance (R) in series with the equivalent inductance (L). Secondly, R and L of the coil layers are computed for several frequencies up to 5Mhz, and then introduced into the equivalent RLC circuit with considering inter-turn and interlayer capacitances. Then the inversion problem is solved in order to identify all inner capacitances of the coil. Finally, the UD-CFRC rod is introduced into the FE eddy current axisymmetric model coupled to an equivalent RLC circuit, as a homogenized conductive material with an equivalent transverse conductivity. The coil with the presence of the homogenized UD-CFRC rod is then modeled as a transformer with a secondary connected to a capacitor in parallel with a resistance in order to evaluate the inner capacitor of the UD-CFRC. All evaluated parameters are then introduced in the last model. The comparison between the computed impedance parts and the measured ones shows a mean error less than 2% and a maximum one of 5% according to the frequency.

Research of technical and economic indicators of reinforcement of reinforced concrete beams by different technologies

The article presents the results of experimental investigations to determine the destructive force of beams reinforced with external reinforcement and control (without reinforcement). According to the results of such investigations, it can be stated that the strengthening of beam structures by external reinforcement made it possible to increase their bearing capacity by 383.3%. It has been established that both carbon fiber reinforcement using "clamps" and carbon fiber reinforcement are effective.The performed analytical researches established technical and economic indicators of various methods of reinforcement of beam constructions, namely: the addition of additional supports, the addition of additional beams, the external reinforcement of stretched zones by MAPEI technology. As a result, data were obtained indicating that the reinforcement of the crossbar by bringing additional rigid support requires 110.4 man-hours (100%), the reinforcement of the crossbar by bringing additional beams - 94.4 man-hours (85.5%), the reinforcement of the crossbar by external reinforcement - 48 man-hours (43.5%). In this case, the reinforcement of the crossbar by bringing additional rigid support is performed in 9.7 days (100%), the reinforcement of the crossbar by bringing additional beams - 6 days (62%), the reinforcement of the crossbar by external reinforcement - 4 days (41.4%). It is also established that the reinforcement of the crossbar by bringing additional rigid support costs 51.8 thousand UAH (100%), strengthening the structure by bringing additional beams - 58.1 thousand UAH (112%), strengthening the structure by external reinforcement - 35.72 thousand UAH (68.9%).The obtained research results indicate that the labor intensity, duration and cost of reinforcing the beam with external reinforcement is lower compared to other technologies. Efficiency is achieved by a structural component - increasing the bearing capacity without changing the design solution and by technological component - reducing the labor intensity, duration and cost of work.