The traditional coin-tap testing is one of the oldest methods of non-destructive testing and it is regularly used for testing laminated structures. Percussion testing requires the marine surveyor to tap each point of the structure to be inspected with a coin and listen to the resulting sound radiated by the structure.
Unfortunately, the coin tapping method is dependent upon the inspector’s hearing and interpretation, the results are subject to interference from workplace noise, and this technique is unable to provide quantitative data.
Composites are widely used in aerospace industry. One of the biggest players in that industry; Boeing; has developed an Electronic Digital Tap Hammer that provides a quantitative measure of the hammer/composite impulse time that can be correlated to flaws such as delaminations in the structure. The instrumented tap hammer supplements the tonal discrimination of the operator with a numeric readout that is related to local part quality. The effects of background noise and operator differences on the inspection results are eliminated. This hammer is relatively insensitive to the magnitude or forcefulness of the hammer hit, but very sensitive to the local stiffness of the structure. This method provides objectivity in the test, increases the sensitivity of the test and enables the inspector to collect quantitative results of the actual impact response.
This method and device is used by both Boeing Commercial Airplane Group as well as Boeing Defense & Space Group on the composite commercial and military aircraft.
marineSOLUTIONS has invested in this Electronic Digital Tap Hammer which can be applied to many composite requirements on boats.