Electro-mechanical piezoresistive properties of three dimensionally interconnected carbon aerogel (Aerographite)-epoxy composites

Aerographite (AG) is a carbon aerogel consisting of three-dimensionally (3D) interconnected graphitic microtubes. This study characterizes the electrical and mechanical properties of Aerographite/epoxy composites under tensile load. Aerographite can be used as a highly tailorable filler in polymer nanocomposites (PNCs) where the carbon filler and the matrix form an interpenetrating structure, contrary to particle filled systems. Aerographite networks with densities ranging from 3.0 to 13.9 mg/cm3 were produced in a chemical vapour deposition (CVD) process. An infiltration with epoxy leads to Aerographite/epoxy composites with filler contents in the range of 0.26-1.24 wt%. Their electrical conductivity is in the range of 2-13.6 S/m, thus, orders of magnitude higher compared to CNT-based PNCs at comparable filler contents. Although a large amount of direct interconnections of the graphitic tubes is given, interestingly the Aerographite/epoxy composites show a piezoresistive behaviour comparable to PNCs filled with carbon nanotubes (CNT) or graphene. Unexpected shifts between external mechanical strain and electrical signal have been observed in incremental piezoresistive experiments. Young's moduli and tensile strengths of the PNCs are not affected by embedding Aerographite networks. Fractographic observations identify graphitic wall slippage as the dominating failure mechanism. Both, piezoresistive characterization and fractography studies have been correlated and a model for the observed piezoresistive response is derived.