A fixing frame applied with Foam Cored CFRP Sandwich Composite (FCCSC) that replaces SAPH440 steel used in the fixing frame for hydrogen storage was designed, and its structural safety was evaluated. In the design of the fixing frame, FCCSC was implemented by PMI foam core, a Bakelite mount, and Carbon Fiber Reinforced Plastics (CFRP) using woven carbon fiber prepreg. Unlike the steel fixing frame, the FCCSC-applied fixing frame had a cross-section of hollow-rectangular, and its validity was confirmed through finite element analysis. Structural analysis of the designed FCCSCapplied fixing frame and steel fixing frame was performed. Under the extreme load condition of 9G acceleration, the steel fixing frame showed the lowest safety factor of 1.14 based on the yield strength in the opposite direction of gravity. On the other hand, the FCCSC-applied fixing frame showed a safety factor of 7.6 at the maximum principal stress and 3.15 at the shear stress. Through this result of structural analysis, it was verified that the FCCSC-applied fixing frame, which was 25.8% lighter than the steel fixing frame, was 1.8 times safer.

It is generally accepted that mechanical properties of sandwich composite are affected by curing pressure variation. For the present study, the effects of curing pressure variation on the compressive properties of balsa wood sandwich composite were investigated. For this purpose, a compressive test was conducted using balsa wood and honeycomb core sandwich composite, applying 40 psi and 60 psi curing pressure conditions. The results showed that compressive load of balsa wood sandwich composite applying 60 psi curing pressure condition is higher than applying a 40-psi curing condition. This phenomenon is due to an increase in the adhesive strength of the balsa wood sandwich composite as the curing pressure increases, thereby improving the compressive strength. Deboning and local buckling were observed on fracture surfaces of all balsa wood sandwich composite, but only global buckling was observed at honeycomb core sandwich composite.