This work is focused on analysis of mechanical behaviour of aircraft engine’s sound-absorbing panels (SAPs) exposed to in-service damage. Its aim is to suggest techniques of local repair of damaged SAPs and estimation of their post-repair residual strength. Fibreglass laminate panels with tubular core and perforated elements were studied for this purpose. A mechanical behaviour of structural elements of the panels was modelled with the finite-element (FE) analysis, with through rupture considered as an in-service defect. A technique of defect repair without dismantling parts from the structure is introduced using a novel vacuumless technology. This procedure was implemented on specially produced samples and simulated with FE. Residual strength of repaired samples was compared with that of standard and ruptured ones in tension experiments and FE analysis. Conclusions about applicability limits of the presented method are provided.