Definition of the different requirements needed for the materials and how to physically and practically evaluate them by test. Followed by a preselection of materials that would theoretically agree with the objective, commercial or develop by OVERLEAF partners. Different tests were done by partners or subcontract to analysis the properties and compere the different material selection.
In addition to material optimization, in WP3 the manufacturing process of the demonstrator has been develop. With focus on the Inner and External tank on the optimization of the trajectories, which is an additional challenge as the tank design is based on a spherical geometry. Therefore, the aim is to achieve a stack that maximizes mechanical properties and reduces permeability. For this reason, it is necessary to combine different strategies to solve the problem of the accumulation of tapes on the pole.
Initial configuration of the system considered a hollow inner tank to reduce weight and complexity, other optimized parameters of the system are component thicknesses. For the inner tank, the thickness was set from the beginning as the minimum one defined by the manufacturing process, as it was expected to withstand low loads. Further simulations have proven the inner tank is not compromised with this thickness, so the minimum value of 2.5mm (after machining 0.5mm from the outer surface) is seen as the optimal choice). As for the outer tank, all analyses are provisional until the final material is selected and characterized. The thickness of each insulation layers are sized in order to comply with the dormancy objective.
