COPV Analysis Tool

Though this calculators main intention was to estimate minimum require tank masses, it actually goes far beyond that. To obtain the minimum mass for a given laminate, the calculator performs pass/fail analysis structural analysis on the tank using 4 different failure criteria options: Maximum stress, maximum strain, tsai-hill, and tsai-wu. This analysis also includes residual stresses within the composite due to deviation between in process cure temperature and the test temperature.

In order to perform this test, many other properties need to be determined. These include mechanical properties for individual lamina in principle and global coordinate systems as well as properties for the entire laminate.

Before running the structural analysis, the code runs a probability of failure analysis to ensure that probability of success is above 99.9%. This analysis is based on a weibull model for which the weibull parameters have been empirically derived given in the linked document .

The current code assumes a common bulkhead tank with hemispherical caps for propellants and standalone tank for pressurant. I am currently developing in line fracture mechanics analyses of the tank liners to ensure that failure does not occur due to common flaws inherent to the process. This is difficult because critical stress intensity factors (Kc) are most often determined experimentally, and I do not have the resources to compile a database; a problem which I am actively looking to work around.

Future plans are to develop a parametric model for the tanks in Siemens NX using this analysis as a starting point. Then, FEMAP / Nastran will be used to optimize ply orientation. Though this is just a starting point, feel free to download and play around with it yourself!