Reduction of fabricational thermal residual stress of the hybrid co-cured structure using a dielectrometry

In this work, cure control system using dielectrometry for co-cured metal/composite hybrid structures was devised to reduce the fabricational thermal residual stress of the bonding layer between metal and composite material. The cure kinetic model of carbon fiber epoxy composite materials was developed by curve fitting the differential scanning calorimetry (DSC) data. The relationship between start of cure and gelation points of epoxy resin and the dissipation factor were investigated. The degree of cure was obtained by comparing the dissipation factor from the dielectric properties to the degree of cure from the DSC. Also, the curvature experiment of co-cured steel/composite strip and the static lap shear tests of the co-cured steel/composite lap joints were measured to investigate the effect of cure cycle on the thermal residual stress of the co-cured hybrid structures. From these results, the cure control algorithm using the dielectrometry for reduction of thermal residual stress was devised and verified under various temperature profiles.