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The present study deals with the finite element analysis of parametric instability characteristics of delaminated bidirectional Glass/Epoxy composite panels exposed to hygrothermal field with harmonic in-plane loading based on first order shear deformation theory. An 8-noded isoparametric finite element model was developed which takes account of the influences of area delamination and hygrothermal environment for predicting dynamic instability regions of composite flat panels. Validation of numerical results from finite element analysis was done with those available from previous researches. The influences of various parameters like static load factor, area of delamination, temperature, moisture, fiber orientations, boundary conditions and stacking sequence on the dynamic instability regions of bidirectional Glass/Epoxy flat panels were investigated. Significant effects of these parameters on the dynamic stability characteristics of composite plates were observed and discussed. [ABSTRACT FROM AUTHOR]

Abstract: The present study deals with the effects of moist environment on the natural frequencies of vibration of Glass/Epoxy woven fibre composite doubly curved panels with strip delamination using the finite element method (FEM). For modelling the delamination, multipoint constraint algorithm is incorporated in the analysis. The effects of boundary condition, delamination size and shape of panels on natural frequencies of vibration are investigated in the moisture content range. The frequencies of vibration reduce with increase of moisture in delaminated curved panels. The reductions of frequencies are more prominent for higher degree of moisture concentrations and significantly affected by boundary conditions. [Copyright &y& Elsevier]

Abstract: Free vibration response of laminated composite shells with delamination is presented using the finite element method based on first order shear deformation theory. The shell theory used is the extension of dynamic, shear deformable theory according to the Sanders'' first approximation for doubly curved shells, which can be reduced to Love''s and Donnell''s theories by means of tracers. An eight-noded C 0 continuity, isoparametric quadrilateral element with five degrees of freedom per node is used in the formulation. For modeling the delamination, multipoint constraint algorithm is incorporated in the finite element code. The natural frequencies of the delaminated cylindrical (CYL), spherical (SPH) and hyperbolic paraboloid (HYP) shells are determined by using the above mentioned shell theories, namely Sanders'', Love''s, and Donnell''s. The validity of the present approach is established by comparing the authors'' results with those available in the literature. Additional studies on free vibration response of CYL, SPH and HYP shells are conducted to assess the effects of delamination size and number of layers considering all three shell theories. It is shown that shell theories according to Sanders and Love always predict practically identical frequencies. Donnell''s theory gives reliable results only for shallow shells. Moreover, the natural frequency is found to be very sensitive to delamination size and number of layers in the shell. [Copyright &y& Elsevier]