Structural optimization for CFRP cryogenic tank based on energy release rate

In the present study, we conducted structural optimization for CFRP cryogenic propellant tank. Under the cryogenic temperature, large thermal stress between metallic material and CFRP might cause the debonding failure. Optimizations were performed by considering crack propagation. Energy release rate of debonding crack calculated by virtual crack closure method was used as objective function. Two analytical conditions were considered: when merely the temperature of tank was decreased and when the pressure was applied to the tank in the decreased temperature. Two types of optimizations were conducted for each condition. One is liner wall thickness optimization. Another optimization is curved wall shape optimization. On the basis of these results, we proposed a new design of the CFRP cryogenic tank. The new design that has notch and optimized dorm shape can reduce energy release rate near the cap and prevent crack propagation.