Paper Title
New Qualitative Method To Investigate The Vibration Of Composite Rectangular Plates Under The Effect Of Dimension And Rigidities Ratio Of Both Perpendicular Sides

In this work we propose a qualitative method that allows rapid expertise of the vibration behavior of composite rectangular plates taking into account the dimensions ratio (a/b), and the effect of the rigidity ratio (Dx/Dy) along the two axes of the plate (x,y). The comparative analysis of two or more composite rectangular plates which differ in their boundary conditions (ex: SSCC / SCSC) is intended to systematically verify the frequency curves and ensure their relative proper positions with regards to their modal progression.From previous work, the qualitative method applied to the isotropic rectangular plates with the support conditions (SSCC/ SCSC) and based only on the effect of the dimensions ratio (a/b) showed a good concordance with the results obtained from the FE method. In our previous works, we proposed a study based on a dimension ratio (a/b>1) and on varying the rigidity ratios (Dx/Dy) = (2, 1, (2:3), (1:2), (1:3), (1:4)).In this work we propose to globalize and validate the qualitative method by studying the case where we have a dimension ratio (a/b<1) and by taking into account the effect of the rigidity ratio (Dx/Dy) = (2, 1, (2:3), (1:2), (1:3), (1:4)). The comparative and qualitative analysis of frequency responses allowed the justification of the position and the threshold of the respective modal frequencies of the two plates (SSCC/ SCSC) in accordance with the results obtained from the numerical and analytical methods in use. The first six frequency modes are obtained from the results achieved by developing a MATLAB program that checks these results against those obtained by the FEM using the code of calculation ANSYS. Keywords—Free Vibration, Thin Plates, composite, Rigidity Ratio, Equivalent Method, Rayleigh's Method, Finite Element Method.