An Initial and Progressive Failure Analysis for Cryogenic Composite Fuel Tank Design

Thermal residual stresses, internal pressure stresses, and acceleration stresses during launch were evaluated and quantified for cryogenic composite fuel tank design. Both failure initiation and progression of graphite/epoxy laminate system (IM7/977-2) [0/90/90/0/0/90]s and graphite/BMI laminate system (IM7/5250-4) [0/90/90/0/0/90]s were investigated using the non-isothermal classical laminate and plate theory (CLPT) and the maximum stress failure criterion. The thermal residual stresses in the transverse direction are the dominant stresses on each ply in the launch stage. After initial ply cracking, through-the-thickness temperature change of a laminate related to fuel leakage as well as a laminate stiffness matrix change was applied to the progressive failure analysis. The fuel leakage-based progressive analysis shows a higher number of initial ply cracking does not necessarily mean a higher chance of matrix cracking in all plies. The graphite/BMI laminate has such an advantage as transverse thermo-mechanical resistance over the graphite/epoxy laminate at an initial exposure to —253°C and 1500 kPa. In terms of complete laminate matrix cracking, however, the graphite/ epoxy laminate is more resistant to transferring stresses to other plies than the graphite/BMI laminate.