Thesis

The use of composite materials in the space field has led to great weight improvements. To continue to achieve significant weight gain, composite cryogenic tank is the next technological application to reach by replacing the current metal alloy cryogenic propellant tanks. Lighter reinforced organic matrix composite materials (that are at least as efficient from a mechanical, thermal, chemical and ignition resistance point of view) are a realistic target to be reached that has been explored in recent years. Many research approaches tend to answer to this technological lock, but the potentialities of Carbon NanoTubes (CNTs) in terms of mechanical and physical properties, need to be explored deeper.
A first phase to assess the interest of CNTs for space applications (collaboration CNES/CEA/I2M/CMP Composite) was carried out to associate CNTs with a cyanate ester matrix in layered composite materials through three processes: (i) transfer of aligned CNTs mats by hot pressing (ii) dispersion of entangled CNTs mixed with resin, or (iii) growth of nanotubes aligned directly on the dry ply. Knowing mechanical and thermal loads, the aim is to demonstrate the efficiency of CNTs and influence of their characteristics with regard to damage tolerance of the material and consist in delaying the cracking process of the composite nearby the CNT layer and thus blocking the percolation of the cracking network which leads to the loss of tightness. For the preferred development process identified, the aim of this doctoral work is now to consolidate the material functionalisation with CNTs (shape, density, etc.) and the understanding of the mechanical behaviour (at room temperature and at low temperature) for the development of the layered material integrating CNTs.
Knowing the potential final application as cryogenic tank or for the improvement of structural materials sustainability in dual application, relevant tests will be performed to demonstrate the impact in terms of damage development and tightness in comparison with the same material without CNTs.