[American Institute of Aeronautics and Astronautics 49th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference 16th AIAA/ASME/AHS Adaptive Structures Conference 10t - Schaumburg, IL ()] 49th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference <br> 16th AIAA/ASME/AHS Adaptive Structures Conference<br> 10t - Effects of Central and Non-Central Plate Stiffener on Free Vibrations Response of Integrally-Stiffened and/or Stepped-Thickness Plates or Panels