Ashes derived from the combustion of vegetal and animal biomass still represent a mostly unexplored secondary raw material for the production of alkali-activated materials, given their peculiar chemical nature. In this work, calcium phosphate biomass ashes were successfully used as partially reactive fillers in a metakaolin-based geopolymer composite to produce, by direct foaming, sustainable and lightweight boards with thermal insulating properties. The investigated materials were obtained by activating a blend of metakaolin and biomass ash in a weight ratio of 1: 1 and foamed with the addition of H₂O₂ in measure of 5 wt. %, to maximize the volume of disposed ash and ensure adequate properties to the material at the same time. The obtained geopolymer composite was characterized by microstructural, chemical-physical, mechanical and thermal analysis: the obtained results showed that biomass ash and metakaolin well integrated in the microstructure of the final porous material, which was characterized by a density of about 310 kg/m³ and a thermal conductivity of 0.073 W/mK at a mean test temperature of 30 °C, coupled with an acceptable compressive strength of about 0.6 MPa. Dilatometric and thermogravimetric analysis, performed up to 1000 °C, highlighted the thermal stability of the composite, which could be regarded as a promising material for low-cost, self-bearing thermal insulating partitions or lightweight cores for thermostructural sandwich panels.

New inorganic nanostructured matrices for fiber-reinforced composites with enhanced high-temperature stability were developed from alkali aluminosilicate polymers doped with different ultra-high-temperature ceramic (UHTC) particles. The alkali aluminosilicate matrices were synthesized at room temperature with a high SiO₂:Al₂O₃ ratio and then further functionalized by doping with 4–5 wt % of micrometric SiC, ZrB₂, ZrC, and HfC powders and finally thermally stabilized as glass–ceramics at 750 °C. The different UHTC-doped matrices were characterized according to their dimensional and microstructural changes after thermal cycling in air flux at 1000 °C. The first results showed that carbide-based UHTC powders improved the thermal stability of the matrices, preventing the excessive swelling of the material and the formation of detrimental voids that might result in the lack of adhesion with reinforcing fibers. Contrarily, the addition of ZrB₂ resulted in an excessive matrix swelling at high temperature, thus proving no efficacy compared to the undoped matrix. Impregnation tests carried out on C-fiber fabrics showed good processability, adhesion to the fibers, and fracture pull-out, especially for carbide-based matrices.

This study concerns with the optimisation of a fibre-reinforced composite material ply book and application to an aeronautical component. The presented material solution is a recyclable FML (Fibre Metal Laminate). Recyclable and structural PMCs (Polymeric Matrix Composites) developed up-to now in ENEA had to be improved to satisfy the high-demanding fire characteristics requirements in aeronautics, particularly for the case considered in ongoing project FireMat (www.firemat.it), namely a turbine-bonnet production. FireMat project objective is the combination of weight reduction and fire resistance, maximizing the use C2C recyclable, secondary and biomass derived raw materials. Aluminium layers were introduced inside the lamination, to act as oxygen barriers and improve fire-retardancy. FML were obtained starting from a fire-retardant biobased resin, which was associated with aeronautical grade basalt-derived mineral fabric, processed in the form of a prepreg and then coupled with aluminium foils. FE modelling was based on performed mechanical characterization of the single layers and inter- layer adhesive strength of the ply stack: a composite sandwich structure (including aluminium honeycomb) was optimised.