Monolithic mesoporous silica (silica aerogel) is presented as 3D continuous reinforcement for conventional thermoplastic matrices. Backfilling of the porous silica network with epoxy resin yields a bicontinuous material with interlocking silica and epoxy phases. Long range connectivity in the resulting silica reinforcement will better facilitate load transfer within the nanocomposite whilst ensuring uniform silica dispersion. This reinforcing structure may increase stiffness whilst retaining the toughness of the epoxy resin. A stiffer matrix will better resist fibre micro-buckling when applied to unidirectional fibre composite materials leading to an overall improvement in compressive strength. A pre-formed monolithic reinforcement avoids the undesirable viscosity and agglomeration effects seen for dispersed nanoparticulate fillers allowing potentially higher weight loadings of silica reinforcement. Silica content is instead limited only by the ability of the porous silica aerogel network to uptake epoxy resin. Therefore, a mesoporous silica precursor of high envelope density (> 0.2 g.cm-3) with a sufficiently open pore structure for epoxy-backfilling is required.