Mechanical property characterization of film-fabric laminate for stratospheric airship envelope

A stratospheric airship can offer a cost effective alternative to earth orbit satellites for telecommunication and science observation. To float in the stratosphere with very thin air density, the airship needs to be designed with envelope materials that are extremely light, flexible and of high strength. Film-fabric laminates, which consist of single plain woven fabric layer impregnated in polymer matrix and are laminated with thin films for environmental and leakage protection, have unique material characteristics compared to conventional composite structures that can be exploited in the design of the high altitude airship envelope materials. In this study, the material characterization of a film-fabric laminate developed for stratospheric airship envelop was conducted. First, uni-axial tests were performed for fabricated specimens to obtain tensile properties. The tests were done in the thermal chamber at low, room, and high temperatures to investigate the temperature dependency. Next, the effective tensile properties were predicted by geometrically nonlinear finite element analyses. The analyses were done for unit cells where the detailed fiber tow architecture was modeled discretely. The analysis results were compared to the test results and investigated focusing on the geometrical nonlinearity and the micro-structural behavior of the laminates.