Experimental and Numerical Study of Residual Strength of Composite Grid Stiffened Cylindrical Shells Under Sequential Compressive Axial Load

In this research, the behavior of the initial strength of a composite lattice cylinder structure under axial compressive force in the first loading and its residual strength in the second loading stages have been studied. For this purpose, in the experimental method, first, the composite cylindrical structure, with a hexagonal lattice pattern, is made using a silicone mold and filament winding process. In the first experimental loading test, the structure is subjected to axial compressive force and its initial strength at the beginning of collapse (first damage) is obtained. Then, in order to study the residual strength, the damaged structure is subjected to the second loading stage after complete unloading and recovers its initial length. Validation of force-displacement results obtained from ABAQUS finite element software has been done in comparison with the results of experimental loading tests. Next, the numerical analysis of the effect of various rhombic and triangular lattice patterns on the initial strength and residual strength of the structure is performed. The results show that the highest ratio of bearing force to weight on the collapse threshold of the structure in first loading stage is related to the triangular, hexagonal and rhombic, lattice patterns and hexagonal, triangular and rhombic lattice patterns, respectively in the second loading stage. After the second loading stage, hexagonal, triangular and rhombic lattice patterns retained 80.5%, 69.11% and 54.01% of their original strength, respectively. Also, hexagonal, triangular and rhombic lattice patterns have the highest specific absorbed energy up to the collapse threshold, respectively.