Optimization of carbon fiber usage in Type 4 hydrogen storage tanks for fuel cell automobiles

Finite element (FE) analysis of a filament wound 700-bar compressed hydrogen storage Type 4 tank is presented. Construction of the FE model was derived from an initial netting analysis to determine the optimal dome shape, winding angle, and helical and hoop layer thicknesses. The FE model was then used to predict the performance of the composite tank subject to the operating requirements and design assumptions, and to provide guidance for design optimization. Variation of the winding angle and helical layer thickness in the dome section was incorporated in the FE model. The analysis was used to determine the minimum helical and hoop layer thicknesses needed to assure structural integrity of the tank. The analysis also examined the use of “doilies” to reinforce the dome and the boss sections of the tanks to reduce the number of helical layers wound around the cylindrical section of the tank. The results of the FE analyses showed that the use of doilies reduces the stresses near the dome end but the stresses at the tank shoulder are not affected. A new integrated end-cap design is proposed to reinforce the dome section. With the integrated end-cap, FE analysis showed that the high stress points shift from the dome to the cylindrical section of the tank.