When an infinite plate is excited, the frequency at which the speed of the free bending wave becomes equal to the speed of acoustic wave in air is called the critical frequency. When a structure is excited acoustically, the frequency at which the speed of the forced bending wave in the structure and the speed of the free bending wave are equal is called the coincidence frequency. Critical and coincidence frequencies of panels are important in studying their behaviour under acoustic excitation. Most spacecraft structural panels are of honeycomb sandwich construction and many of them have face sheets made of composite material. The critical and coincidence frequencies of such panels are discussed here. Expressions for critical and coincidence frequencies of thick isotopic and thin as well as thick symmetric composite panels are derived. It is shown that the orthotropic behaviour and transverse shear flexibility of the panels affects the critical and coincidence frequencies. The critical frequency of a typical composite honeycomb sandwich panel obtained using the above expressions match well with experimental results.
Critical and coincidence frequencies of flat panels
Kritische und Übereinstimmungsfrequenzen von Flachplatten
Journal of Sound and Vibration ; 205 , 1 ; 19-32
1997
14 Seiten, 9 Bilder, 16 Quellen
Article (Journal)
English
Critical and coincidence frequencies of flat panels (SV970992)
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