Modal behaviors and influencing factors analysis of inflated membrane structures

Accurate modal analysis is the basis to evaluate the dynamic performance of inflated membrane structures, however, it is still a challenge to analyze and testify due to strong nonlinearity of geometry deformation, initial stress and the air-elastic effects. This paper presents modal characteristics of inflated beam and flexible airship envelope. Firstly, an approach to numerically simulate modal behaviors of a plane membrane in the air was validated by testing natural vibration behaviors of plane membranes. This was followed with modal analysis of inflated tube in experimental and numerical methods. The influencing factors for the modal performance of the inflated tube were estimated in terms of boundary condition, internal pressure, elastic modulus and air. Based on this outcome, the verified simulation method was employed to investigate the natural vibration behaviors of flexible airship including dry and wet modal analysis. Thirdly, pressure difference, geometric dimension, welding seam were considered as influencing factors to study their effects on modal characteristics of non-rigid airship hull. Lastly, modal analysis of airship with suspended curtain in self-equilibrium configuration and self-weight and buoyancy was to investigate close practical engineering structural behavior of large airship.