Ultrasonic Attenuation Effects Associated with the Metal to Composite Adhesive Bond Problem,
DREXEL UNIV PHILADELPHIA PA
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In the work reported here, a difficult problem is examined which has the very real application to the inspection of adhesive bonds between metals and fiber reinforced composites. This problem deserves special attention not only because on its technological importance, but also because the composite medium can be expected to modify the ultrasonic signal reflected from the adhesive layer in two ways. First, the composite has abnormally high attenuation and an acoustic impedance that is near to the adhesive so that the part of the signal reflected from the adhesive to composite interface will be much smaller than is the case for an adhesive to metal interface. Second, the layered nature of the fiber reinforced material can be expected to contribute additional reflections that will mix with the signal from the adhesive layer and possibly render it useless for interrogation of the bond strength. As a result of these studies, it can be concluded that the effects of the composite are not significant at low frequencies below 7 MHz for the cases studied and that effects arising from disbonds at the interfaces of the adhesive layer or within the composite can be recognized at higher frequencies.