Grinding of CFRP
Analyses have been conducted in order to overcome the intrinsic difficulties of the grinding process and to facilitate maintenance services. These analyses have been directed towards grinders with staggered edged knives in order to proceed, within the same device, with subsequent cuttings by a staggered step rotor; this way the process is split in several phases performed within the same device. In fact, the eccentric assembling of the blades allows a pre-reduction of the size of the inserted materials.
On the basis of the previous preliminary directions the choice of the type of grinding devices fell on grinders with a rotor with sectored blades and not with a single blade.
The main advantage of this kind of devices consists in the arrangement of the “knives” on the rotor, which produces a gradual impact of the sectors on the counter-blades (not a single impact rotating blade – counter blade) therefore, the production being equal, the electricity consumption results even 50% less than grinders with continue rotating blades.
In light of the information obtained by the development phases of the SUSRAC project, it has been set going the recognition of possible suppliers of devices already operating on the market and applicable to the present project, not recurring to the realization of dedicated devices.
Mixing of the materials
According to the SUSRAC project that represents the origin of the present work, the transformation and re-use process of CFRP coming from aircraft dismantling, production scraps and/or other industrial sources, is based on the creation of a gel solution of EPS and acetone. In this solution powders and/or ground parts of CFRP are dispersed in order to produce a mixture composed, in its final configuration, by the 70% by wt of CFRP and the 30% of EPS.
This relation represents the characterization of the product; nevertheless other mixtures are possible, for instance the one with 60% of CFRP and 40% of EPS. It is evident that, reducing the CFRP percentages, the mechanical characteristics of the finished product decrease; for this reason the mixture composed by the 70% of CFRP and 30% of EPS has been chosen as the reference for the design of the plant. In this way the greatest mechanical characteristics are guaranteed for the final product.
The process consists in the solubilization of EPS in acetone to create a gel where it is possible to disperse the recycled fibers coming from the grinding process. At the end of the process, the acetone is recovered and re-used.