Effect of temperature and nonlinearity of PMMA material in the design of observation windows for a full ocean depth manned submersible

Abstract

Renewed international interest in exploring the hadal zones (6,000-11,000 m) promoted the development of full ocean depth deep-sea manned submersibles. The manned cabin is the most critical component in deep-sea manned submersibles. An essential requirement to guarantee the safety of the manned cabin is the proper design of the observation windows. The current design approach, which is available in design rules such as ASME PVHO-1.2012, did not have sufficient experimental basis when applied for full ocean depth observation windows. In this study, a full-scale polymethylmethacrylate (PMMA) window model is designed and tested under quasistatic loading-unloading cycles in a high-pressure chamber. Strain variations in several critical points and axial displacement in the inner center are recorded and compared with simulation results, and a large discrepancy was found. The potential influencing parameters, such as temperature and material nonlinearity, are investigated. It was found that correction of these two factors can explain the discrepancy. The newly determined material properties can be used in the design of full ocean depth observation windows.