Abstract: A damage detection device is used to detect damage in bonded and laminated composite structures. A tap hammer or tap coin containing an acceleration sensor is connected to a circuit that can measure the width of an impact signal and then display the result. The result correlates to local stiffness of a structure. A method of determining the desired signal width and the method of using the damage detection device, includes tapping a known good region and then tapping a suspect region. Readings from the two areas are used to determine whether the suspect region is within an acceptable range. The circuit determines the desired signal width by measuring from the time the impact signal exceeds a threshold to the time it falls below the threshold.