Study of Vibration Characteristics of Skew Laminated Composite Sandwich Plates and Shells Operating In Hygro and Thermal Environments

Abstract

This dissertation presents an investigation of the influence of temperature and moisture on free vibration characteristics of laminated composite, hybrid composite, and sandwich panels. The composite sandwich panels (plates and shells) considered to be made of laminated composite material face sheets, and softcore materials as the core materials. A finite element (FE) formulation is developed for the whole model using a layerwise first-order shear deformation theory (FSDT) considering the uniform temperature and moisture concentration rise. The influence of temperature and moisture on the natural frequencies of various shell structures such as cylindrical, ellipsoid, hyperbolic, and spherical shells are investigated and compared with the frequencies of flat sandwich plates. Effects of length to width ratio, length to thickness ratio, radius to length ratio, the ratio of core thickness to the thickness of the face sheet, skew angle, boundary conditions on the vibration characteristics of the skew laminated composite sandwich panels are studied. Additionally, an attempt has been made to investigate the challenges in an experimental vibration study of the laminated composite sandwich plates with a 3D printed Polylactic acid (PLA) core. Furthermore, an artificial neural network (ANN) based predictive model is established to understand the influence of temperature and moisture on the skew sandwich plates. Further study has been extended to investigate the performance of active constrained layer damping (ACLD) of a laminated composite sandwich plate operating in a thermal environment. Additionally, an experimental investigation is performed to understand the influence of temperature on the natural frequency of laminated composite sandwich plates operating in sub-ambient temperatures. Consequently, the present investigation is believed to be enormously helpful in the field of computational mechanics and structural health monitoring of composite sandwich structures operating in challenging environments suitable for various industrial applications.