Investigating the Permeability of CFRPs for Liquid Hydrogen Storage
Topic(s) : Special Sessions
Co-authors :
Jean VEREECKE (FRANCE), Christophe BOIS (FRANCE), Jean-Christophe WAHL (FRANCE), Florian LAVELLE , Bruno DESMARSAbstract :
In a context of space launchers lightening, the development of liquid propellant tanks in composite materials without liners is a technological challenge. This study focuses on evaluating the permeability of composite materials to assess their suitability for such applications. A specialized leak rate measurement setup for tubular specimens has been devised to reproduce real loading conditions of the tank (bi-axial proportional stress) and avoid edge effects. The pressurization of tubes using helium generates a gradient that can damage the composite and allow leak rate measurements. Leak rates are measured using a mass spectrometer, and tests are conducted over a temperature range from room temperature to 130K using a dedicated cryogenic chamber (see Figure).
Leak rates are measured on healthy and damaged specimens. They provide very useful data that translate the effect of damage and temperature on the permeability of the structure. Progressive damage of the composite does not significantly affect its permeability until the creation of the first leak points. The transition from pure molecular diffusion to Darcy's flow is observed only after the initiation of leaks (Kumazawa et al., 2004). This transition prompts the need for a redefined permeability coefficient. Tests are performed on multiple specimens, they show that the global leak rate of the structure is almost proportional to the number of leak points. Further investigation into the influence of pressure gradient on the permeability coefficient reveals a direct correlation with the opening of cracks, directly linked to transverse stress in each ply. This observation holds true even when considering thermal residual stresses alone. Indeed, leak measurements have been performed by isolating one leak point and progressively lowering the temperature up to 130K.
Finally, a model prediction tool is proposed considering the crack network as an ideal nozzle. The laminate theory provides the stress state of every plies that lead the cross section, and the loss of charge coefficient is proposed using the work from (Latanision et al., 2006). The model well reproduces the coupling effects of the crack opening and the pressure gradient on the flow rate.
This comprehensive study contributes valuable insights into the permeability behavior of composite materials under cryogenic conditions. The understanding of transport mechanisms in composite materials subjected to thermomechanical loads is crucial for the specification and the design of linerless propellant tanks.
Leak rates are measured on healthy and damaged specimens. They provide very useful data that translate the effect of damage and temperature on the permeability of the structure. Progressive damage of the composite does not significantly affect its permeability until the creation of the first leak points. The transition from pure molecular diffusion to Darcy's flow is observed only after the initiation of leaks (Kumazawa et al., 2004). This transition prompts the need for a redefined permeability coefficient. Tests are performed on multiple specimens, they show that the global leak rate of the structure is almost proportional to the number of leak points. Further investigation into the influence of pressure gradient on the permeability coefficient reveals a direct correlation with the opening of cracks, directly linked to transverse stress in each ply. This observation holds true even when considering thermal residual stresses alone. Indeed, leak measurements have been performed by isolating one leak point and progressively lowering the temperature up to 130K.
Finally, a model prediction tool is proposed considering the crack network as an ideal nozzle. The laminate theory provides the stress state of every plies that lead the cross section, and the loss of charge coefficient is proposed using the work from (Latanision et al., 2006). The model well reproduces the coupling effects of the crack opening and the pressure gradient on the flow rate.
This comprehensive study contributes valuable insights into the permeability behavior of composite materials under cryogenic conditions. The understanding of transport mechanisms in composite materials subjected to thermomechanical loads is crucial for the specification and the design of linerless propellant tanks.