Manufacturing of Hierarchical (Nano-)Composite Structures: Numerical and Experimental Perspectives

Thermoset polymer nanocomposites have considerable potential to improve the functionality and optimise the performance of composite structures. Such a nanocomposite generally consists of a modified polymer matrix (continuous phase) containing nanofillers (discontinuous phase) at the nano scale to tailor the mechanical, physical, and thermal properties of the final product. This review focuses on selected nanofillers, particularly graphene (Gr), carbon nanotubes (CNTs), nanoclays (NCs), and nanocellulose, including cellulose nanocrystals (CNCs) and cellulose nanofibres (CNFs). The impregnation mechanisms of nanocomposites in fibrous porous media across different length scales, together with their chemo-rheological characteristics, thermal response, and mechanical integrity, are discussed from numerical and experimental perspectives. The modification and functionalisation of nanomaterials, the preparation and processing of polymer-based nanomaterials, and the manufacture of hierarchical composite materials are also reviewed. The findings demonstrate that composite performance depends on the nanofiller type, content, dispersion, and compatibility with the matrix, whereas agglomeration, increased viscosity, filtration, poor impregnation, and non-uniform curing remain major challenges. The review further demonstrates that the scope of available numerical studies remains limited and identifies a need for improved models that connect nano-scale phenomena with the micro-, meso-, and macro-scale behaviour of the manufactured composite, thereby supporting more effective process optimisation.