Structure failure and strength evaluation of honeycomb-based sandwich composites under variable hydro-thermal-mechanical load

The high-strength and lightweight sandwich structures have broad application prospect in aerospace, wind turbine generator, traffic and civil engineering. The sandwich structures usually service with severe environment and complicated mechanical load, structure failure and strength prediction are crucial issues. Under time-varying and optional position hydro-thermal-mechanical loading, this paper systematically analyzes strength failure, buckling and delamination of a sandwich beam with carbon fiber-reinforced polymer face sheet and aluminum honeycomb core. Effects of elastic boundary conditions, hydrothermal stress, configuration of honeycomb cell and thickness of face sheet on failure pattern and critical failure loading are evaluated. The theoretical deformation model is verified by performing a bending experiment of cantilever beam. For the honeycomb core with small re-entrant angle and shot horizontal cell wall, the sandwich cantilever beam occurs strength failure of face sheet and delamination is happened in simply supported beam. With increase of re-entrant angle and cell wall length, buckling of horizontal cell wall becomes the primary failure pattern of sandwich beam. With thickness increase of face sheet, the failure pattern switches from face sheet's strength failure to delamination. The critical load for delamination decreases to a volley value and then increases with thickness of face sheet.