Analysis and design of inflatable aerospace structures

This dissertation presents a new structural model for the bending behavior of inflated cylindrical fabric structures that are used as beams. The goal of this investigation was twofold: to perform a fundamental investigation into the static and dynamic bending behavior of the inflated fabric beam and to apply the results to practical problems faced in the design of aerospace inflated structures.; Fundamental work was done in development of a model for the static and dynamic bending behavior of the inflated beam. The bending analysis of the inflated beam resulted in a differential equation of bending for the unwrinkled regions of the beam that is identical to the Euler-Bernoulli solution. A more complex differential equation was found when the fabric wrinkled due to the applied moments.; Experimental work was performed to verify the bending model for the inflated beam. Excellent agreement was found between the model and experimental results in static bending tests of a number of inflated cantilever beams. Dynamic tests were performed and mode shapes, natural frequencies, and damping mechanisms for the inflated beam examined. A series of dynamic tests were also performed on the NASA KC-135 Low Gravity Simulator aircraft to determine the sensitivity of the dynamics of inflated beam structures to changes in gravitation level. Large changes in structural damping were found to occur across G level.; This basic research was used to predict the dynamics of a complex inflated structure, a mockup of an inflated solar concentrator. Structural modeling was performed using a finite element software package and the lower modes of vibration of the inflated structure were accurately predicted by the finite element model.; The inflated beam bending model also proved itself immediately useful in aerospace applications since many of the current space suit components are essentially fabric tubes. Recommendations for improving space suit flexibility that have arisen from this research include reducing the modulus and increasing the Poisson's ratio of the fabric. A series of experiments were performed to prove these concepts. The results of those tests and the space suit glove design recommendations arising from them are included in this work.