Thermal effects play significant role in the design of a structure when it is supposed to work in hot environment. For this purpose a thorough analysis of structure is necessary that could precisely consider the effect of temperature change. At first an accurate thermal analysis is required that may be further followed by stress or dynamic analysis. In this work, shell finite element developed by Rolfes et al to perform 3D thermal analysis is studied using Ansys and results are found good when comparing with the 3D solid element result. The interlaminar shear stress analysis of composite plate considering thermal and mechanical loading is studied under different set up of laminate scheme and the results have been found good when compared with the available 3D elasticity results. Then, the effect of thermal stresses on natural frequency of a structure is analyzed considering as thermally prestresssed case under different laminate schemes and boundary conditions. Finaly, A stringer stiffened panel is analyzed under thermal and mechanical load. Interlaminar stresses and natural frequency are evaluated by considering the effect of thermal loading.

Composite stiffened panels have been used in aerospace industries for past decades. Due to light weight nature composite panels are prone to buckling. In this study buckling load for Ortho-grid panel and Iso-grid panel is determined. This was accomplished by developing a composite laminate for both skin and stiffener using MSC PATRAN/NASTRAN was used for linear buckling analysis of composite panels. The buckling loads of two panels were determined based on finite element analysis results, including geometric dimension, thickness of the skin, number of laminae, ply stacking sequence, thickness and height of stiffener. Parametric studies of general grid stiffened panel was conducted using skin thickness, stiffener thickness and stiffener height as design variables. Conclusions drawn from these results are presented. All three buckling modes appeared and maximum buckling load was observed in skin buckling mode for Iso-grid panel.