Biaxial Test Method for Characterization of Fabric-Film Laminates Used in Scientific Balloons

Space Structures that require lightweight materials with sufficiently high strength and environmental endurance have been in increasing demand since the early 1980’s. However, the biaxial behavior of these structural materials under pressurized loading is rarely found in the literature. An experimental investigation was conducted to develop a test method and hardware to characterize the biaxial behavior of a fabric-film laminate intended for use as a structural envelope for large balloons. The material tested is a composite laminate of three layers. The three layers are: polyester-based woven fabric, 6 microns film of polyester (Mylar type A) and 6 microns film of linear low density polyethylene (LLDPE). The laminate structure provides high strength to weight ratio. In this study, a test technique has been developed to measure the biaxial response of the material to known stress ratios. The information gained from the test can be manipulated to estimate Poisson’s ratio and the development of a material structural model.