Objectives The aim is to propose a structural strain test method under high hydrostatic pressure environment in water. And investigate the buckling pressure of composite shells under high hydrostatic pressure environment in water and the effect of different initial defects.
Methods A high hydrostatic pressure experiment was conducted on a composite shell, and the strain of the structure was measured under 15 MPa hydrostatic pressure using the deep-water 3D-DIC (digital image correlation) method based on high pressure shield. The experiment results were compared to numerical simulations to confirm the feasibility of the 3D-DIC test system in a high hydrostatic pressure environment and verify the accuracy of the numerical method. Based on the numerical simulation method, research was conducted on the buckling behavior of the composite shell
Results The results show that the average error between the experimental results and the numerical simulation results was found to be 7.2%. In addition, the ultimate load of the composite shell was found to be almost quadratic function related to the size of the added geometric defects in different modes, and the average gradient of change in ultimate load was 1.48-2.12 MPa/mm in the first order mode and 1-4.32 MPa/mm in the third order mode.
Conclusions The 3D-DIC test technology allows for accurate strain measurements on composite shells in high hydrostatic pressure environments. Moreover, in the high hydrostatic pressure environment in water, geometric defects largely affect the ultimate load of the composite shell, where third-order modes are affected to a greater extent than first-order modes.
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