The double cantilever beam (DCB) test is a standardised method for characterising delamination properties in composites, adapted here for sandwich structures with metal cover layers and a polymer core (MPM). An inverse parameter identification approach is used based solely on force-displacement data to characterise interface properties, eliminating the need for crack length measurements. DCB tests are conducted with varying pre-crack configurations, core thicknesses, and loading rates. The results show that critical strain energy release rates GGIIII increase with increasing core thicknesses, loading rates, and cohesive pre-cracks, while interface strengths G _IC R ₃ ⁺are influenced less by these factors. Numerical simulations using a refined mesh based on a mesh study and a cohesive zone model are used to characterise the delamination behaviour. The inverse method of determining cohesive zone model parameters RR ₃ ⁺ and GGIIII by fitting numerical force-displacement curves to experimental results provides significant improvements in accuracy and efficiency compared to manual re-calibration, reducing the pre- and post-processing time while providing robust parameter estimation for delamination behaviour in MPM composites.