Co-authors​ :

 Cecilia SCAZZOLI (SWITZERLAND), Robin TRIGUEIRA (SWITZERLAND), Adrien DEMONGEOT (SWITZERLAND), Ugo LAFONT (NETHERLANDS) 

Fibre reinforced polymers (FRPs) have been increasingly adopted in high performances structural components because of their superior mechanical and lightweight properties. In particular, epoxy resins are often chosen as a matrix, for their high glass transition temperature, Tg, stiffness and chemical resistance. For these reasons, these types of material are used in the construction of pressure vessels (PVs) functioning as reservoirs for the cryogenic propellent of space launchers. However, they have some major drawbacks: they are brittle and sensitive to damage, they cannot be re-shaped or repaired without additional material, nor recycled. Another challenge is represented by the process induced defects that can arise when building a PV [1]. Damage events that can threaten the structural integrity and the impermeability of cryogenic fuel tanks can also arise in use, due to the extreme thermo-mechanical conditions [2]. In particular the build-up of matrix microcracks and delamination eventually connecting can create preferential paths for the cryogenic propellent, in the liquid or gaseous state, to leak, leading to serious consequences for missions’ safety [1], [2]. To counter these limitations, in some cases metal is chosen as the main material to build PVs (Type I PVs), entailing a higher weight compared to FRPs, which always represents a critical point in space missions; otherwise liners, either made of steel/aluminium (Type III PVs) or plastic (Type IV PVs), usually cover the internal part of composite cryogenic tanks to prevent leakages [1]. This induces an overweight of 10-25% compared to Type V PVs [1]. For these reasons, in spite of the challenges, Type V PVs raise an increasing interest in the industry. Furthermore, over the last years, targeting a more sustainable and cost efficient space industry, the European Space Agency (ESA) has been driving the research towards reusable launchers, so to avoid leaving debris behind, highlighting the necessity of smart composite structures, like healable composite structures.
In order to tackle the mentioned challenges, CompPair Technologies Ltd. has developed an efficient solution to build healable composites specifically for space applications. The mechanical and healing performances of the developed composite material as well as the compatibility with the space environment have been characterized. In particular, the capability to resist cryogenic microcracking and to heal those potential damages has been investigated.