Abstract: A non-destructive bond testing apparatus utilizes impedance variation represented by both the phase and amplitude of the signal vector response of a sonic energy generating and receiving probe, which is applied to a laminar, honeycomb or fiber composite structure under test. Typical bonding methods for which this bondtester and method are applicable include adhesive bonding, diffusion bonding, brazing, resistance and impact/friction bonding. A cathode ray tube displays the tip of the vector (as a bright dot) which represents the impedance characteristic affected by the structure under test.