EVALUATION OF THE CURING KINETICS OF A POLYMER MATRIX COMPOSITE USING A SENSOR CONTAINING AN ELECTRICALLY CONDUCTIVE FILLER

Abstract

In this work, the kinetics of the curing of fabric GFRP was carried out by measuring the parameters of its electrical conductivity. A compound of epoxy resin (ED-20), plasticizer (DBF) and hardener (PEPA) with the addition of finely milled graphite (FMG) was used as a matrix. To en-sure high-quality mixing of FMG in epoxy resin, a planetary mixer was used. Plain weave glass tape 0.2 mm thick with two woven wires was impregnated with a matrix compound. This tape was placed onto a beam 4 mm thick made of typical GFRP as an external electrically conductive functional sensor (FS). During curing at room temperature, periodic measurements of the electrical conductivity of the FS and the stiffness of the beam with FS in three-point bending were carried out. The amount of FMG into the matrix compound was below the percolation threshold; there-fore, electrical measurements of FS required alternating current. The dependence of the imped-ance on the current frequency (from 10 Hz to 1 MHz) was recorded. Comparison of the change in FS electrical impedance with the change in the beam stiffness during the curing showed their close correlation. The proposed method of measuring the FS impedance can be used to assess the degree of curing of the polymer matrix in critical large-sized composite products during the manufacturing process.