The effect of patch hybridization on repair performance of sandwich composite

Abstract This study investigates the effectiveness of a newly proposed hybrid patch repair (HPR) method for damaged sandwich composite structures through experimental testing and numerical analysis. In the HPR configuration, a carbon fiber layer is strategically embedded beneath the foam core to redirect shear forces and prevent catastrophic core failure. Three-point bending tests conducted on specimens with a 35 mm damage diameter showed that the maximum load increased from 3247 N in the pristine specimen to 4362 N with conventional patch repair (CPR) and further to 4558 N with the proposed HPR method, corresponding to strength improvements of 34.3% and 40.4%, respectively. Additionally, the HPR configuration exhibited a significantly higher deformation capacity, reaching 18.75 mm compared to 7.73 mm for CPR, demonstrating superior energy absorption and delayed failure. Similar trends were observed for the 50 mm damage diameter specimens, where HPR maintained structural performance while CPR exhibited stiffness degradation with increasing damage size. Numerical simulations performed using a SOLSH190-based finite element model with Hashin failure criteria showed less than 4% deviation from experimental results, validating the modelling approach. The findings confirm that hybrid reinforcement provides a substantial improvement in damage tolerance, strength recovery, and energy dissipation, presenting a robust repair solution for critical sandwich composite structures used in aerospace, marine, and wind energy applications.