The efficacy analysis of repairing methods on carbon fibre-reinforced sandwich structures

The application of carbon fibre-reinforced polymer (CFRP) material has been widely used in the aerospace and civil engineering fields, which necessitates studying repairing methods on damaged composite structures for economic purposes. This paper numerically and experimentally investigates the efficacy of scarf repair and patch repair methods of carbon fibre-reinforced sandwich structures. A parametric analysis was conducted, and the main parameters were determined by comparing the structural strength and stiffness of the repaired sandwich structures to the baseline models under tension and compression. A novel index, the Comprehensive Recovery Index (CRI), is proposed to incorporate the contributions from both strength and stiffness to evaluate the repair efficacy of the repaired specimens, with an exponential decay factor to adjust the weight coefficients of the contributions. Based on the parametric results as posterior observations, this work shows that the repaired efficacy could be accurately predicted and optimised, and a Gaussian Process Regression (GPR)-based optimisation method is presented to identify the parameters of the repaired specimens with the optimised repair efficacy value. This paper systematically analyses and summarises the impact of both repair methods on the mechanical properties of the composite material sandwich structures, and provides design guidance for the repair solutions in CFRP sandwich structures in future engineering applications.