Lightweight storage tanks for liquid propellant and on-orbit fuels are a critical technology for the entire space sector. Although carbon fibre reinforced polymer (CFRP) composites have been successfully used in aircraft structures, matrix cracking and the resulting gas leakage have been a long-standing problem and was identified as a grand challenge by top global space companies. Recent research has identified that existing fibre reinforced polymeric composite materials suffer from matrix cracking when subjected to cryogenic temperature, due to the high thermal stresses induced by the large disparity between the coefficients of thermal expansion of polymeric matrix and carbon fibres. The matrix cracks in the composite laminate can link up to form interconnected pathways for hydrogen to escape. Furthermore, the matrix crack can compromise the strength of the composites, posing a significant challenge to the use of fibre composite tanks in launch vehicles and in-orbit spacecrafts.

A UNSW research team led by Professor Chun Wang, including Dr Mohammad Saiful Islam and A/Prof Garth Pearce, has been collaborating with Lockheed Martin and Omni Tanker to develop and demonstrate a novel technique to simultaneously lower the thermal residual stress and to increase resistance to matrix cracking by incorporating nano-scale materials in the matrix, thus preventing the formation of matrix cracks at cryogenic temperatures. We have invented a new method of toughening CFRPs, which has now been patented and adopted by Lockheed Martin and Omni Tanker for large-scale commercial applications for storage and transport of liquid hydrogen[1],[2].

Matrix cracks in an un-modified composite
Absence of matrix cracks in toughened composite
Functionalised nano-particles
A prototype of composite tanks for liquid hydrogen