Investigation of Geometric Imperfection in Inflatable Aerospace Structures

Abstract

Communication and solar array inflated structures must be deployed to a very precise geometric configuration in order to meet quality requirements of their application. The focus of this paper is on geometric imperfections associated with inflated structures. To further understand some of the elements, that derive imperfection in a parabolic inflated communication and solar array structures, a computational model is proposed. This computational approach is dictated by the geometric complexity, deformation sensitivity as function of load and boundary conditions, and nonlinear characteristics of inflated structure assemblies. The deformation of a single component depends on the flexibility/stiffness of other components due to their interaction. In order to simulate such deformations of the multicomponent inflated structure, in the present study, the computational model consists of main parabolic shape envelope (reflector and canopy), torus, and catenary’s support and uses geometric nonlinear finite element. Further, tuning of communications and solar arrays is a primary concern in the operation of these systems. To investigate the effects of pressure tuning on geometric imperfection of a parabolic inflated antenna, in this investigation, analyses using uniformly axisymmetric and asymmetric applied load are performed. The analyses assume an initial parabolic shape envelope with a perfect circular edge for the reflector and canopy. Error estimates, which quantify geometric imperfections, are computed. The results show that as the axisymmetric load increases, the surface deviation from the parabolic shape of the envelope also increases. An asymmetric load on the surface of the torus leads to variable tensile forces in the catenary along the circular edge of the envelope, which in turn cause a visible local asymmetrical deformation in the vicinity of the circular edge of the envelope. In general, an asymmetric load causes greater geometric imperfections and should be avoided