Smart cure cycle with cooling and reheating for co-cure bonded steel/carbon epoxy composite hybrid structures for reducing thermal residual stress

In this work, a smart cure cycle with cooling and reheating for co-cure bonded steel/carbon epoxy composite hybrid structures was developed to reduce the fabricational thermal residual stress between the steel and carbon epoxy composite material. The thermo-mechanical properties of the high modulus carbon epoxy composite were measured by a Differential scanning calorimetry (DSC) and rheometer to obtain the optimal time to apply the cooling operation. The static lap shear strength of the co-cure bonded steel/composite lap joints and tensile strength of the composite specimen were measured to investigate the effect of cure cycle on the thermal residual stress. Also, the deflection of the hybrid structures was measured to measure the actual cure temperature with respect to various cure cycles. From the experiments, it was found that the smart cure cycle with cooling and reheating not only reduced the fabricational thermal residual stress but also improved the strength and dimensional accuracy of the hybrid structures.