Buckling behavior of honeycomb FRP core with partially restrained loaded edges under out-of-plane compression

Fiber-reinforced polymer (FRP) sandwich deck panels with sinusoidal honeycomb core geometry have shown to be efficient in both new construction and rehabilitation of highway bridge decks. The sandwich panel consists of top and bottom laminated face sheets bonded to the honeycomb core, which extends vertically between face sheets. This paper is focused on the study of the buckling capacities of the core components under out-of-plane compression. The facesheet and core are attached by contact molding and are, therefore, not rigidly connected. Thus, this problem can be described as the instability of an FRP core panel with two rotationally restrained loaded edges. An elastic restraint coefficient is introduced to quantify the bonding layer effect between the facesheet and core, and a simple and relatively accurate test method is proposed to obtain the restraint coefficient experimentally. A combined analytical and experimental study of compression is presented. By solving a transcendental equation, the critical compression buckling stresses are obtained, and a simplified expression to predict buckling strength is formulated in terms of the elastic restraint coefficient. The analytical solution is verified by finite element (FE) analysis. Compression tests are carried out to evaluate the effect of the bonding layer thickness, and the experimental results correlate closely with analytical and FE predictions. A parametric study is conducted to study the core aspect ratio effect on the buckling load. The method described in this paper can be further extended to determine local buckling capacities of other structural shapes with elastic restraints along the loaded edges.