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.

Skin-stiffener structures are extensively used in the aerospace field due to their structural efficiency in terms of stiffness/weight and strength/weight ratios. The application of such panels is primarily within fuselages and wing boxes, where the weight saving potential of composite materials compared with aluminum alloys is well known. However, design of composite panels involves the optimization of a large number of variables such as ply thickness and plate widths. Further complication arises when the expert knowledge required for laminate design is considered and when the panel is constrained by buckling under axial compression. In this study, the behavior of Grid Stiffened Composite Cylinder is examined under the axial compressive load. Compressive load causes buckling and develop stresses in the structure. For the buckling analysis two approaches are used.(1)Analytical (2)FEM. An analytical smeared stiffener theory is used to determine buckling load and then FEM results were compared to gain the confidence on the developed models. The validated FEM model and analytical smeared stiffener theory is used to conduct parametric analysis.

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.

Modal parameters of spacecraft structures are important indicators of their dynamic characteristics which can be used for vibration reduction and control. In the present research modal parameters of a rocket are identified by using continuous wavelet transformation. The advantages of the wavelet transformation for the modal parameters identification over other methods is study. Through finite element method transient dynamic response of a system is determined then continuous wavelet transformation is applied to find the modal parameters like modal frequency, mode shapes and damping ratio.

Numerical simulations of sheet metal forming process based on finite element method (FEM) is widely applied for its powerful capability in forming process prediction. Since there are parameters which could affect the result of forming process, it becomes important to approach a set of parameters to improve the formability. In the present work, first, a comprehensive literature review was made for different optimization methodologies in sheet metal forming process. Then we proposed an optimization methodology using Response Surface methodology (RSM) and Genetic Algorithm (GA) for the optimization of sheet metal forming process, and the theory of RSM and GA are illustrated. The presented method was first applied to an example from literature, the results verified the feasibility of the proposed methodology. Then the methodology was applied to variable binder force optimization of the NUMISHEET'93 2D draw bending problem. The work indicated that the proposed optimization methodology is efficient and universal, which means it can also be applied in other applications of aerospace industry.

The aim of this work is to know more about the underprediction of springback in numerical simulation of sheet metal forming. There are a lot of factors which influence the accuracy of springback with numerical simulation.One factor responsible for the inaccurate springback prediction is the assumption of constant Young's modulus in FE analysis. Young's modulus, however, is found to decrease during plastic deformation. Therefore, an accurate model is needed to be implemented in FE analysis which can predict the decrease in Young's modulus. With passage of time, Young's modulus is found to restore to its initial value. The present study focuses on this aspect of springback prediction. Bake Hardenable (BH) steel has been selected to investigate the degradation and recovery in Young's modulus. The decrease in Young's modulus and its recovery has been measured experimentally by two methods i.e. the dynamic method (Impulse Excitation Technique) and a static method (Tensile Test).

Lighter and stiffer structural construction is required for space rockets than those used in aviation. A reduction of only 1 Kg in the weight of a rocket intended for a flight to Mars and back results in saving 2 tons of propellant. At present, sandwich technology is extensively used in Aeronautics and Aerospace fields. Sandwich panels with thin composite face sheets are used due to their ability to produce structures with high stiffness to weight and strength to weight ratios. In this research, Finite Element (FE) model is generated for a particular test configuration of honeycomb sandwich structure with metallic (Aluminium) skins. In this modelling effort, the specimen is modelled in such a way to simulate and analyze in a true sense. Stability and non linear analysis is carried out using FEA software SAMCEF. With geometric and material nonlinearity, the results are then compared with the experimental ones. Force displacement curves acquired from FEA and 3point bending test seem good enough for comparison.