a diagnostic tool that determines the type of defect present in a core composite sandwich structure . the diagnostic tool is portable and non - destructive . the diagnostic tool locally generates and records load versus displacement measurements for the core composite sandwich skin , in both the tension and compression directions . these values are then compared to similar measurements taken in a non - discrepant area of the structure . defect type is determined based on the differences in the load / displacement behavior between the non - discrepant and discrepant locations .