Experimental Investigation on Thermal Buckling Behavior of Truss-Core Sandwich Panels

This paper presents an experimental study on the thermal buckling behavior of sandwich panels with truss cores. The ultimate goal is to find the critical buckling temperature and examine postbuckling behavior of this newly developed sandwich panel experimentally. A specifically designed fixture, which can introduce in-plane loads to the sandwich panel through thermal expansion mismatch between the specimen and the load frame, is applied in the experiment. High-temperature strain gauges are attached at the center of the sandwich panel face sheets to measure the local in-plane response, and the critical buckling temperature of panels deformed in symmetric mode is determined by using the Southwell method. To obtain the full-field postbuckling mode as well as critical buckling temperature of the sandwich panel deformed in asymmetric mode in high-temperature environments, a noncontact measurement system based on the three-dimensional digital image correlation technique is also developed. The accuracy of the present noncontact measurement technique is validated by the coordinate measurement machine technique, a conventional contact measurement method. It is found that the critical buckling temperature obtained from experiments is lower than that predicted by theoretical and numerical models, due to defects and imperfections of the truss core and sandwich panel during fabrication. Full-field measurement also indicates that local yielding together with overall buckling is the typical deformation mode in the tested specimen.