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Polydopamine (PDA) coated SiO2 nanoparticles (SiO2@PDA) were considered as filler for an aeronautical graded epoxy matrix. The nanoparticles (NPs) were synthesized by a modified one-step procedure, based on the nucleation and growth of SiO2 NPs followed by the growth of a thin PDA layer on the silica surface. TEM observations have revealed that Core/Shell Nanoparticles (CSNPs) are characterized by a core with a diameter of 250 nm and a 15 nm thick PDA shell. Nanocomposites with different filler concentrations (0.1, 1 and 5 wt%) were manufactured. Preliminary fracture toughness results show an increase of both KIC and GIC with addition of 1 wt% of CSNPs. Further samples will be tested by thermal and mechanical techniques, with particular attention to the thermal stability and fracture toughness properties.

A glassy hyperbranched polymer (HBPG) was synthesized and dispersed within an aeronautical graded epoxy matrix as toughening agent. This filler is a polyester characterized by a Tg higher then room temperature (∼90 °C) and obtained by means of bulk poly-condensation reaction starting from a diphenolic acid as precursor. HBPG/epoxy systems were prepared considering two concentration levels (0.1 and 5 wt%) and the effects on mechanical properties and fracture toughness were investigated. HBPG induces a limited reduction of the Tg along with an improvement of the fracture toughness performances as indicated by the increase KIC and GIC values.