Abstract: As a special form of composite material, the composite honeycomb sandwich structure has high specific bending stiffness, specific bending strength and designability, as well as physical properties such as sound absorption, sound insulation and heat insulation, and is used in the aviation field. Composite sandwich structure T-joints, as a common connection form in the aviation and marine fields, have attracted lots of attention from scholars. Tenon and mortise T-shaped structure can effectively improve the structure efficiency and reduce weight. However, the existing work mainly focuses on the theoretical analysis and experimental research of the traditional T-joint, and there is little research on the tenon-and-mortise T-joint. This article presents an experimental study on the bending failure mode and load-bearing capacity of the composite honeycomb sandwich tenon-and-mortise T-joint. Five kinds of T-joint test specimens with different tenon widths and different tenon numbers were tested, and bending moment-displacement curves were drawn. The bending test results show that the failure of the T-joint specimens includes tensile failure of the adhesive surface in the tenon shoulder area, shear failure of the adhesive surface of the upper panel in the tenon area or tensile fracture of upper panel. In the process of loading, the tenon shoulder area is firstly debonded, then the tenon area bears most of the load, and finally the upper panel and the bottom plate in the tenon area are debonded or the panel is broken. Parameter studies show that the increase of the width and number of tenons can significantly increase the bending stiffness of T-joints, and it also makes an important contribution to improve the bending bearing capacity of the T-joint.

Key words: honeycomb sandwich structure, T-joint, tenon-and-mortise adhesive joint, flexural failure mechanism, composites