Thermomechanical processing of Type-4 composite cylinders under static load

Abstract

Type-4 composite cylinders have recently gained recognition in global markets for storage of compressed gas as an alternative to the existing metallic cylinders. The developed cylinders are certified before commercial deployments, based on the safety requirements of the available standards for onboard compressed gas storage. However, various accidents relating to the sudden burst of these cylinders have been reported previously. The failure depends on a variety of reasons; failure due to thermal degradation has been addressed in this study. Finite element analysis is used to predict the ultimate hoop stress of composite rings; the model is experimentally validated using the NOL ring test as per the ASTM standards. An FEA model to virtually test the cylinder for hydrostatic pressure burst test, high temperature creep test and accelerated stress rupture test is also developed and experimentally validated. The composite cylinders are tested as per the testing criteria mentioned in ISO 11439 which is the safety standard for onboard compressed natural gas storage. The validated FEA models can be used to analyze the thermomechanical response of composite cylinders when subjected to a hydrostatic load under temporary thermal conditions or when operated at temperatures higher than the service temperature mentioned in the ISO standard.