A comparative study is performed on the monitoring of delamination healing in CFRP-ionomer sandwich composites by non-destructive techniques and destructive compression testing. Artificial delaminations of various areal dimensions and nature were introduced during production of the composites. The extent of the delamination and the healing thereof was monitored in both air and water-coupled ultrasonic C-scan experiments as well as by the frequency shift of the local defect resonance (LDR). It is shown that the LDR approach can be used to detect the early stage healing of the delaminations while ultrasonic C-scanning techniques are very effective to determine the extent of healing in the final stages of the repair process. A quasi-linear relation was observed between the delaminated area measured with ultrasonic C-scan and the compressive failure strength in destructive testing. This correlation shows the beneficial effect on the compression strength of the delaminated area reduction by on-demand healing.@en