Applicability of Composite and Nanocomposite Materials to Reusable Liquid Propellant Tanks

F. Lenzi (Sp), L. Scatteia, S. Cantoni, C.I.R.A. Italian Aerospace Research Center, Capua (Italy); M. Franceschi, A. Minigher, CimTEC Lab., Trieste (Italy) 
In the frame of the PRORA USV space program, a research work aimed at studying barrier and microcrack resistance optimised composite materials for cryogenic tank building is running.
In order to investigate the mechanism of the thickness-wise propellant leakage through CFRP laminates, the barrier performance of several carbon fiber reinforced composites based on epoxy and cyanate-ester systems was estimated at three different level ranging from the macroscopic behaviour to the intrinsic material-related phenomena (multi-scale approach): leakage phenomena, permeability behaviour and sorption and solubility behaviour.
The effects of the cure conditions and the thermal cycles on the mechanical response and the barrier properties of the polymeric composite materials has been investigated.
Finally the possibility to use montmorillonite (cationic clay) modified with a primary ammonium salt, or an anionic clay (layered double hydroxide), belonging to the family of the hydrotalcites, to realize a nanocomposite matrix is also analysed. Actually, nanocomposites can potentially provide increased stability to the system, by preventing chemical degradation in the aggressive liquid fuel environments and better barrier performance thanks to the longer diffusive path that a penetrant molecule must travel in the presence of filler and to the decrease in mobility of macromolecules driven by interaction between nanoparticles and polymeric chain.

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