Flexural Performance Of Composite Sandwich T-joints Under Bending Loads

T-joints are the essential structure of the ship, which is used to bond watertight bulkhead and hull. T-joints can distribute loads in effect, but also maintain overall hull water resistance. The T-joints can transmit loads between vertical faces when the hull is under external loads. Therefore, T-joints are one of the weakest parts among the entire structure. Ship security depends on the T-joints between the substructures. Therefore, rational design of composite sandwich T-joints makes a great difference in ship constructing. Compared with traditional metal or composite T-joints, composite sandwich T-joints have lighter weight, higher stiffness and better impact resistance. It will become the main trend in ship construction to use composite sandwich T-joints. Therefore, the influence of geometry on the mechanical properties of sandwich T-joints under anti-static bending and transient bending is studied in this paper with finite element analysis.Whether the analysis result is effective or not depends on the accuracy of material properties. The basic mechanical properties of woven glass fabric reinforced composites were first obtained with a series of experiments. A parametric finite element model of the T-joint is constructed by the ANSYS APDL language. According to the álvaro failure criterion, Ye failure criterion and the characteristics of woven glass fabric reinforced composite, the failure criteria and stiffness degradation method are presented in this paper. A T-joints progressive failure program complied in APDL language was verified by tensile test.Orthogonal experimental method was used to study the influence of foam core thickness, triangular foam cushion angle, strengthen layer thickness and strengthen layer length on the flexural properties of composite sandwich T-joint. The results show that the core thickness is the most important parameter, and then the foam cushion angle, while the strengthen layer thickness and length have less influence. The optimal performance of the sandwich T-joint under static bending would be achieved by the parameters as follows: core thickness of 50 mm, foam cushion angle of 60°, strengthen layer thickness of 7mm and the distance between the strengthen layer end and horizontal plate end of 20 mm.Finally, the transient analysis was used to study the influence of the four factors on the flexural properties of composite sandwich T-joints under transient bending. The results show that the resistance to dynamic load performance of joints fluctuates when the foam cushion angle and the core thickness increases, with the optimal performance obtained with the angle of 70°and the core thickness of 40 mm. Increasing the thickness of strengthen layer will lead to degradation of resistance to dynamic load performance, with the optimal thickness of 40 mm. When the distance between the strengthen layer end and horizontal plate end increases, the performance of joints will drop firstly and then increase, with the optimal distance of 60 mm.