Dynamic Performance of Hygrothermal Mechanically Preloaded Variable-Stiffness Composite Fairing Structures

Abstract

Since the introduction of variable-stiffness composites, the design philosophy for high-performance lightweight composite structures has broadened greatly. Indeed, variable-stiffness composites have been shown to increase buckling performance and dynamic stability, as well as to modify the dynamic response by tailoring stiffness distributions. Thus, efficient linear analysis tools play a significant role in the early design of variable-stiffness structures, allowing designers to identify many viable solutions when considering preloaded dynamically excited aerospace components. To address this need, a Ritz-based method for eigenfrequency and dynamic instability analysis of hygrothermal and mechanically prestressed variable-stiffness laminated doubly curved payload fairing structures is presented. Flexibility in modeling and design is achieved using Sanders–Koiter-based shell kinematics that allow general orthogonal surfaces to be modeled without further assumptions on the shallowness or on the thinness of the structure. The efficiency of the proposed Ritz method is enabled by using Legendre orthogonal polynomials as displacement trial functions. By comparing the present approach with finite element solutions for variable-curvature, variable-angle tow fairing shell geometries, excellent accuracy is shown, accompanied by an order-of-magnitude reduction in variables by the present method. Original solutions are presented comparing the dynamic behavior of prestressed constant and variable-stiffness composite shell structures, showcasing the viability of the variable-stiffness concept to significantly increase the structural performance of critical doubly curved variable-curvature components such as launch vehicle payload fairings.