Design CFRP composites with tailored properties for LH2 storage and transportation
Topic(s) : Material science
Co-authors :
Joana F. GUEDES (PORTUGAL), Bernardo ROCHA (PORTUGAL), Rita RIBEIRO (PORTUGAL), Rodrigo PINTO CARVALHO (PORTUGAL), Raquel M. SANTOSAbstract :
Aiming to achieve decarbonisation goals and meet the Intergovernmental Panel on Climate Change targets to prevent global warming, by reducing carbon emissions, it is imperative to replace fossil fuels by green alternatives, such as hydrogen, in the mobility sector 1,2. In the particular case of Space transportation and exploration, it is critical to reduce the weight of space vehicles, achieving a significant reduction of the launch costs and increasing the payload capabilities 3–5. Cryogenic propellant tanks (as liquid hydrogen fuel, LH2) are one of the heaviest components of spacecraft vehicles, being metals the traditional material for their production 3. The replacement of metals by carbon fibre reinforced polymers (CFRP) composites can reduce the weight of the cryogenic tank by 20 to 40% 3.
The LH2 storage tanks are subjected to extreme temperatures during refueling operation and also during atmospheric reentry of space vehicle 4. Due to these conditions, thermal stresses promoted by the mismatch of the coefficient of thermal expansion (CTE) between the fibres and the matrix, and stresses due to external loads are generated. When the sum of both exceeds a critical value for the material system and layup, microcracks are developed and delamination can occur, which makes the materials permeable and leads to cryogenic fuel and other gas leakage 3–5. Regarding these challenges, it is necessary to improve some target properties for high-performance CFRP composite materials for cryogenic applications, including toughness and reduce the CTE difference between carbon fibres (CF) and polymer matrix 6.
Thermosets are one of the most used in CFRP composite production, in particular epoxy resin, being one of the most appealing approach to improve the properties of composite materials the matrix modification with fillers 3. Toughness can be improved by increasing the flexibility of the three-dimensional network chains of epoxy resin after the cure cycle (at cryogenic temperature the volume is reduced and materials become brittle), such as rubber elastomers, thermoplastics, core-shell particles, flexible segments or nanomaterials 3. On the other hand, to improve the thermal expansion mismatch between CF and resin is necessary to bring the CTE of the resin closer to the CTE of the fibre, by resin modification with low-CTE or negative-CTE particles.
In this work, particles with different natures were selected for the improvement of toughness, and CTE. In the first stage, the definition of the optimum concentration of each, and the dispersion/dissolution procedure were investigated. Nanocomposites were produced for characterization with the best conditions to determine which particle has a higher potential for incorporation in CFRP. The results showed very promising results in target properties for LH2 composite cryogenic tanks, being the next step the incorporation in composite materials reinforced with fibres and their characterisation.
The LH2 storage tanks are subjected to extreme temperatures during refueling operation and also during atmospheric reentry of space vehicle 4. Due to these conditions, thermal stresses promoted by the mismatch of the coefficient of thermal expansion (CTE) between the fibres and the matrix, and stresses due to external loads are generated. When the sum of both exceeds a critical value for the material system and layup, microcracks are developed and delamination can occur, which makes the materials permeable and leads to cryogenic fuel and other gas leakage 3–5. Regarding these challenges, it is necessary to improve some target properties for high-performance CFRP composite materials for cryogenic applications, including toughness and reduce the CTE difference between carbon fibres (CF) and polymer matrix 6.
Thermosets are one of the most used in CFRP composite production, in particular epoxy resin, being one of the most appealing approach to improve the properties of composite materials the matrix modification with fillers 3. Toughness can be improved by increasing the flexibility of the three-dimensional network chains of epoxy resin after the cure cycle (at cryogenic temperature the volume is reduced and materials become brittle), such as rubber elastomers, thermoplastics, core-shell particles, flexible segments or nanomaterials 3. On the other hand, to improve the thermal expansion mismatch between CF and resin is necessary to bring the CTE of the resin closer to the CTE of the fibre, by resin modification with low-CTE or negative-CTE particles.
In this work, particles with different natures were selected for the improvement of toughness, and CTE. In the first stage, the definition of the optimum concentration of each, and the dispersion/dissolution procedure were investigated. Nanocomposites were produced for characterization with the best conditions to determine which particle has a higher potential for incorporation in CFRP. The results showed very promising results in target properties for LH2 composite cryogenic tanks, being the next step the incorporation in composite materials reinforced with fibres and their characterisation.