The example shows a glass textile reinforced epoxy plate with orthotropic properties. The sizes of the test plate are adjusted in order to obtain a correct plate aspect ratio for a “Poisson” plate. The information about the correct plate aspect ratio for obtaining a Poisson plate is gathered from the beam resonance tests. A Poisson plate has a fixed sequence of modal shapes: first a torsional, next a saddle and next a breathing modal shape.
1) Measurement of the frequencies associated with torsion and breathing modal shapes
The plate is diagonally suspended on thin Nylon threads. The accelerometer is fixed in one of the corners of the plate. The plate must be excited in another corner.
In this configuration, two modal shapes are easily excited (torsion and breathing) because they show a vibration amplitude in all the corners (see moving modal shapes below).
The measurement screen of the resonalyser shows two clear resonance peaks (in this example at 131 Hz and 303 Hz)
The resonalyser software can take the mass of the accelerometer into account in the numerical model. The user must indicate the value of the Mass and the position. In the example below the Mass value is 0.0012 kg and the position is Node number 73.
2) Measurement of the frequency associated with the saddle modal shape
Vertical suspension of the plate. Fix the accelerometer in the middle of an edge of the plate and excite the plate in the middle of another edge.
In this configuration, the modal shape of the Saddle modal shape is easily excited because it shows a vibration amplitude in the middle of the edges (see moving modal shape below).
Saddle Modal Shape
The measurement screen of the resonalyser shows a clear resonance peak (in this example at 269 Hz).
Again, the mass of the accelerometer can be taken into account. In the example below the Mass value is 0.0012 kg and the position of the accelerometer is in Node number 37.