This work describes a successful approach toward the development of a carbon fiber-reinforced composite based on an optimized nanofilled resin for industrial applications. The epoxy matrix is prepared by mixing a tetrafunctional epoxy precursor with a reactive diluent which allows reduction of the viscosity of the epoxy precursor and facilitation of the dispersion of 0.5% wt multiwall carbon nanotubes. The proper choice of the viscosity value and the infusion technique allow improvement of the electrical properties of the panels. The obtained in-plane electrical conductivity is about 20 kS m-1, whereas a value of 3.9 S m-1 is achieved for the out of plane value. Such results confirm that the fibers govern the conduction mechanisms in the direction parallel to the fibers, whereas the percolating path created by the effective distribution of carbon nanotubes achieved by resin formulation and adopted processing approach lead to a significant enhancement of the overall electrical performance of the composites
Within the national HYPROB-HYBRID project, funded by the Italian Minister of Education, University and Research (MIUR), the Italian Aerospace Research Centre (CIRA) is carrying out research activities aimed to realize an on-ground demonstrator of Hybrid Rocket Engine (HRE), with the main goal to validate design methodologies and to acquire expertise on enabling technologies and manufacturing processes. This technological demonstrator, with a thrust class of 30 kN, is based on nitrous oxide (N2O) and microcrystalline paraffin wax and will have most attractive capabilities of hybrid systems compared to solid or liquid engines, e.g., throttability and re-ignition. This paper deals with a preliminary methodological assessment and optimization of paraffin grain manufacturing processes. As known, paraffin wax is intrinsically a brittle, thermoplastic material, very sensitive to the presence of surface or internal rips, flaws, voids, micro-cracks and other microstructural high radius defects. Nevertheless, during combustion, it undergoes elevated thermal (temperature of about 3300 K) and mechanical stresses (pressure chamber of 40 bar) which can initiate and propagate deleterious unstable cracks, leading to the catastrophic failure of the grain and consequent danger of combustion instability, up to explosion of the whole rocket. This undesired behaviour strongly compromises one of the most important advantages of HRE in comparison with Liquid Rocket Engines (LRE) and Solid Rocket Engines (SRE), i.e., its inherent safety due to the separate storage and phases of fuel and oxidizer. Therefore it is crucial to select an efficient and reliable manufacturing procedure able to fabricate paraffin wax solid grain free from defects of critical size.
This work describes a successful attempt toward the development of CFRCs based on nanofilled epoxy resins. The epoxy matrix was prepared by mixing a tetrafunctional epoxy precursor with a reactive diluent which allows to reduce the viscosity of the initial epoxy precursor and facilitate the nanofiller dispersion step. As nanofiller, multiwall carbon nanotubes (MWCNTs) were embedded in the epoxy matrix with the aim of improving the electrical properties of the resin used to manufacture CFRCs. Panels were manufactured by Resin Film Infusion (RFI) using a non-usual technique to infuse a nano-filled resin into a carbon fiber dry preform
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