Wrinkling of Thin Membrane Under Thermal Loading

There has been an increasing interest in the applications of thin membrane in space application, flexible electronic display, manufacturing of glass displays and growth of film on materials at elevated temperatures. Because of the negligible bending stiffness of thin membranes, membranes are lack of resistance to compressive stress. For the applications at high temperatures, the thermal expansion coefficient mismatch between membrane and substrate materials may generate compressive stress that causes the membrane buckling. The study of thermal buckling of isotropic elastic plate in the context of the large - deflection theory was the subject of a series of papers[1-5]. However, it has been noted that none of these papers has considered the second buckling of the membrane resulting in membrane wrinkling. The presence of wrinkles may significantly change deflection and stress profile of membranes. So, it is important to develop an effective analysis method to investigate the wrinkle formation and evolution in membrane subjected the elevated temperature. This paper presents the experiment work to investigate wrinkle formation and evolution in membranes heated from room temperature up to 170 °C. The specimens consist of polymer and metal membranes with steel and silicon substrate respectively. A wide range of membrane shapes and aspect ratios are considered in this work. An experiment set up is developed to study the deflection profiles of membranes at discrete temperatures. The information gained from this experiment work is used to validate numerical modeling results. The Finite Element Analysis results using nonlinear post-buckling analysis are also included in this paper. The nonlinear post-buckling analysis provides a good understanding of the mechanism of wrinkle generation and evolution as temperature increased. It is shown that the first buckling of membrane significantly reduces bending stiffness thus to create localized buckling modes accounting for the wrinkle generation. The wrinkle pattern is stable until the temperature reaches the next critical value. After this critical temperature, the wrinkle pattern is changed until temperature reaches the next critical value. The new wrinkle pattern is keeping evolved until the final temperature is reached. The finite element analysis results are in good agreement with experimental observations.