Nonlinear Structural Analysis of SMA Bonded Curved Skew Sandwich Composite Panel Under Hygro-Thermo- Mechanical Loading

Abstract

The present dissertation proposes a nonlinear mathematical model for the analysis of smart sandwich composite panel structural responses (deflection, frequency, transient and buckling/post-buckling) with and without skew angle including the effect of hygro-thermomechanical loading. In this context, the model has been developed using an equivalent higher-order single layer theory considering the effect of shear deformation and throughthickness stretching effect. Additionally, the model includes the large geometrical deformation of the shallow shell structure (due to combined loading) through Green’s strain in Lagrangian reference frame. Further, to enhance the final performances of the structure against the loading and the environmental conditions, the shape memory alloy fibre has been introduced as the smart material. The material nonlinearity of the functional alloy due to the change in temperature environment has also been incorporated via the marching technique.
The linear and nonlinear finite element solutions of the deflection, eigenvalue and dynamic responses including the buckling load parameter are computed via the in-house computer code (MATLAB). The nonlinear solutions are evaluated through the direct iterative technique in association with the isoparametric finite element steps, whereas the constant acceleration integration method (Newmark’s) for the computation of dynamic responses. In addition, the volume fractions and the pre-strain effect of the smart material due to the variation in ambient condition have been incorporated to show the corresponding improvement of the sandwich components. The numerical model consistency and their accuracy in terms of available published benchmark solutions (numerical/analytical/experimental) for the individual and the combined cases are verified.
In addition, a few experimental tests have been carried out to show the comparison of the bending (linear/nonlinear), eigenvalue and dynamic cases of the in-house fabricated (hand lay-up technique) sandwich structural component (different numbers of face sheet layers and unlike core thicknesses) under the ambient conditions to ensure the model accuracy.
Finally, the influential input parameters which are affecting the structural stiffness and the relevant design aspect including the configurational efficacy have been explored using the present equivalent single-layer higher-order nonlinear (geometry and material) sandwich model. Also, a few recommendations are provided suitably based on the obtained output for the future reference relevant to the applicability of functional material and sandwich construction.