Abstract: The composite sandwich structure is widely used in today′s aviation industry because of its superior mechanical properties, but the traditional woven two-dimensional composite sandwich plate has poor resistance to delamination and peeling resistance in the thickness direction. As a new type of three-dimensional woven composite material, the looping fabric(U-cor) can effectively improve the mechanical properties of the composite sandwich structure in the thickness direction by pre-woven fabric loops. However, at present, there are few studies on the mechanical properties of the looped fabric reinforced sandwich structure in China. In this paper, the mechanical properties of flat-pulled honeycomb sandwich panels are studied. Firstly, a glass fiber looped fabric reinforced sandwich panel and a traditional glass fiber sandwich panel were fabricated by the vacuum bag forming process, and the flat pull test was completed. The force displacement curve and tensile strength were obtained. The test results show that the looped fabric reinforced honeycomb sandwich panel has a higher flat modulus and flat tensile strength. The main reason is that epoxy resin formed glue columns in the looped fabric panel during curing. The glue columns are involved in the stress of the core material to increase the tensile modulus, and the loops embedded in the glue columns also improves the flat tensile strength. It can be concluded that the loop fabric can effectively improve the flat tension performance of the honeycomb sandwich panel. Finally, the corresponding improvement methods and ideas are proposed for some problems in the research.

Key words: U-cor, sandwich structure, honeycomb, flat pull