Vibration Imaging Sensor for Damage Assessment in Composites (VISDAC)

This proposal lays out a development program for a new laser Doppler vibrometer (LDV) instrument designed for non-destructive inspection (NDI) of composite airframe structures which are susceptible to core-crush damage, disbonds and delaminations, for example in composite rotor blades. The sensor employs non-contact laser vibrometry with acoustic excitation of the structure and uses the surface vibration signature as a means for locating and imaging hidden damage sites. Example data are presented from test panels which clearly illustrate the potential of the proposed approach which requires no advanced preparation of the inspection surface. Unlike existing laser vibrometers which employ a scanning single-beam approach, the proposed instrument employs a multiple-beam array to capture full-field (2D) vibration data instantaneously. The 2D imaging format is thus able to image short duration transient surface vibrations, a unique capability which could further enhance the NDI applications for the sensor. The rapid data capture, combined with the flexible fiber-optic design architecture provides for the first time, a viable platform for field based vibrometry for composite defect inspection.