Due to its approximately three times higher energy density by mass compared to conventional kerosene, hydrogen is one of the most promising technologies for reducing CO2 emissions in aviation. However, the energy density by volume is significantly lower than that of kerosene. For example, three thousand liters of gaseous hydrogen correspond only to the energy content of one liter of kerosene at ambient conditions (pressure, temperature). In the automotive sector, this problem is often solved by storing the gaseous hydrogen at a high pressure of 700 bar. Although this approach has already led to a significant improvement, it is still not sufficient for aircrafts, as weight and volume are particularly critical factors here. A further increase in energy density can only be achieved by cooling the hydrogen to 20 K (-253°C), where gaseous hydrogen turns into liquid hydrogen. At 20 K, four liters of liquid hydrogen correspond approximately to the energy density of one liter of kerosene. In order to maintain these cryogenic temperatures and minimize evaporation losses (boil-off), special requirements are placed on the cryogenic storage tanks and in particular on their insulation. Some of these cryogenic storage tanks consist of load-bearing double-wall concepts in which a vacuum ensures thermal insulation, which served as baseline for this study. The authors examined CFRP sandwich structures with 3D-printed honeycomb cores in terms of their manufacturability and their thermal insulation properties at cryogenic temperatures. 3D printing of the cores was chosen due to its advantages with respect to design freedom especially for curved structures such as tank domes but also due to its possibility of local reinforcement in areas of load introduction by means of adjustable cell density and cell wall thicknesses, anti-telegraphing design elements etc. [1]. A further advantage is the possibility to use materials with low outgassing behavior e.g. PEEK [2].     «

Due to its approximately three times higher energy density by mass compared to conventional kerosene, hydrogen is one of the most promising technologies for reducing CO2 emissions in aviation. However, the energy density by volume is significantly lower than that of kerosene. For example, three thousand liters of gaseous hydrogen correspond only to the energy content of one liter of kerosene at ambient conditions (pressure, temperature). In the automotive sector, this problem is often solved...     »