A test and analysis protocol to rapidly characterize nonlinear viscoelastic properties of balloon materials

© 1996 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. The authors examine strategies to characterize nonlinear viscoelastic response using dynamic mechanical test and analysis methodologies. Two models are examined — a hybrid approach using both dynamic-mechanical (i.e. cyclic) and constant stress tests, and a nonlinear approach appropriate for oscillatory load conditions. Although these approaches potentially extend to several materials and geometries, this effort focuses on thin-film polymer materials used in high-altitude scientific balloons. Typically, the constitutive behavior of these materials is characterized by linear viscoelastic models. Although a linear model is sufficient for very small strains or stresses, these materials are highly stress dependent and, consequently, it is necessary for many engineering applications to properly describe this nonlinear behavior. Furthermore, constant stress measurements require extensive laboratory test time, yet the results obtained from cyclic tests and the use of frequency translation of the data provide long term material response characteristics with a short term test program. Although classical dynamic-mechanical test methods are formulated for only linear response, the authors formulate a theory for nonlinear characterization and describe the test protocol required to adequately measure nonlinear response.

A test and analysis protocol to rapidly characterize nonlinear viscoelastic properties of balloon materials Conference Paper