Abstract

Tapered laminated structures have considerable potential for creating significant weight savings in engineering applications. In the present thesis, the ply failure and global buckling failure of internally-tapered curved laminates are considered. For the buckling analysis, four different analytical approaches are employed: (1) classical shell theories using Ritz method, (2) first-order shear deformation shell theories using Ritz method, (3) linear finite element analysis based on first-order shear deformation shell theories, and (4) non-linear finite element analysis. Due to the variety of tapered curved composite plates and the complexity of the analysis, no closed-form analytical solution is available at present regarding their response to compressive loading. Therefore, the Ritz method is used for the global buckling analysis considering uniaxial compressive load. Linear buckling analysis of the plates is carried out based on eight classical shell theories and six first-order shear deformation shell theories. To apply the first-order shear deformation shell theories, an appropriate set of shear correction factors has been determined. The buckling loads obtained using Ritz method are compared with the existing experimental and analytical results, and are also compared with the buckling loads obtained using finite element method. The strength characteristics and load carrying capability of the tapered curved plates are investigated considering the first-ply failure and delamination failure. The commercial software ANSYS® is used to analyze these failures. Based on the ply failure and buckling analyses, the critical sizes and parameters of the tapered curved plates that will not fail before global buckling are determined.

Linear buckling analysis is insufficient to take into account the effect of large deflections on the buckling loads. This effect can only be considered in the non-linear buckling analysis. However, very large number of load steps is required to determine the buckling load based on the non-linear analysis in which the stability limit load is calculated from the non-linear load-deflection curve. In the present thesis, a simplified methodology is developed to predict the stability limit load that requires the consideration of only two load steps. The stability limit loads calculated using the present simplified methodology are shown to have good agreement with that calculated from the conventional non-linear load-deflection curve.

Parametric studies are carried out using the above mentioned four different types of analytical methods. In these studies, the effects of boundary conditions, stacking sequence, taper configurations, radius, and geometric parameters of the plates are investigated.