Evolving Methods for Design by Analysis for Glassy Polymers in Marine Applications

Abstract The use of glassy polymers such as acrylics and polycarbonate for marine hulls, windows, and transparent housings has been in more demand due to increasing use of ROVs, AUVs, and smaller non-military submarines. New "Design By Analysis" (DBA) methods will provide for innovative applications while maintaining safety, reliability, and traceability. The new approach will account for the type of application while enabling new materials and shapes through a combination of experimental and computational methods based on Verification, Validation, and Uncertainty Quantification (VVUQ). Previous standards for life-critical applications like diving systems and submarines were locked into 1970's empirical methods based on defined shapes without directly using material properties. Other uses of glassy polymers, like camera housings, have been more ad-hoc. The method under development will give equipment designers the option to use modern methods like Finite Element Analysis and Computational Fluid Dynamics to innovate within existing engineering code processes. American Society of Mechanical Engineers (ASME) Pressure Vessels for Human Occupancy (PVHO) codes and standards was developed in the 1960's and 1970's based on US Navy-funded experiments. It has a proven safety record, so much so it was recently incorporated into the ASME Boiler and Pressure Vessel Code for industrial equipment. Limited by its empirical basis, it does not use material properties directly to allow you to reduce the thickness by increasing the strength, as one example. Another limitation is the tables in the code are limited to a specific range of shapes and geometric parameters, all of which were set over 50 years ago without any provision to add new shapes or parameters. These limitations have constrained later equipment development, particularly where there are requirements for engineering code compliance. The proposed DBA method under development through ASME uses PVHO applications as the benchmark for the most extreme risk, given the issue of having humans in a confined space under pressure. Once established, this method can be used for other applications ranging from spaceflight to autonomous vehicles to architectural use with the design margins adjusted based on risk analysis, all with traceability provisions for design, materials, manufacturing, and testing. The techniques proposed for this DBA method are proven and can be used immediately by equipment designers regardless of being part of an ANSI-approved engineering standard.