On Initiation and Growth of Debonding between Liner and FW Layer of Cryogenic Composite Material Tank for Rocket System Deu to Nonuniform Liner Thickness

In the present study, damage problems of a cryogenic CFRP tank with an aluminum alloy liner developed for the space vehicle is discussed through results from a three dimensional finite element analysis, which is subjected to not only internal pressure but also high thermal stresses due to cryogenic temperature. The interfacial stress distribution around the area of the thickness change of the liner in the cylindrical portion of the tank is studied since the broad debonding between the CFRP layer and the aluminum liner was observed along the thick liner area after the low temperature exposure and the internal pressure test. The thick portion of the liner was designed to make welding easy and to reduce the thermal effect on the Al alloy during welding. The magnitude of the interfacial stress is found to become sufficiently large to cause debonding at the different portion in thickness unless the size and dimensions of that portion is well designed. The yielding of the liner may cause even higher interfacial stress. The instability of the debonding crack is evaluated through the energy release rate obtained based on the elastic theory using the virtual crack closure technique.