Multiscale modelling and characterisation of nanoreinforced composite laminates

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High strength thermoset epoxy resins are extensively used in high performance lightweight composite laminates for aerospace, automotive, marine and electronic packaging applications. However, these epoxies suffer from relatively poor fracture toughness and are intolerant of defects. Whilst limited improvement in toughness can be achieved using certain common additives, these additives also lead to reductions in high temperature mechanical properties. It is therefore the objective of this work to replace these common additives with nanofillers, and to determine the influence of the type, size and amount of these nanofillers on the strength and the interlaminar fracture toughness of the studied composite laminates both numerically and experimentally. Numerically, 3D multiscale model, with modified coarse-grained molecular dynamics that accounts for the interaction between the nanofillers and the molecules of the epoxy resin, will be developed. An effective Hamiltonian with course grained DOF will be used to replace the original Hamiltonian of the system, thus increasing the simulation efficiency without compromising accuracy. Furthermore, a new "nanoelement", that couples atomistic/continuum regions, will also be developed to overcome the difficulties encountered when enforcement displacement continuity across these regions using commonly adopted continuum finite elements (FE). The FE will be formulated in terms of nodal position vectors to ensure a unified description of energy in the atomistic/continuum regions. Experimentally, extensive mechanical tests, ultrasound and nanostructure analysis will be conducted to characterise the effective properties of the laminates and the distribution of the nanofillers in the epoxy. Carefully designed tests will be conducted to evaluate the effective bond strength/stiffness, interlaminar fracture toughness and strain energy release rate for varying amounts of nanofillers and different temperatures. This will enable the validation of the model and creation of new high performance composites for possible patent and use in the next generation aircrafts. This work will lead to the training of the HQP in leading edge research, dissemination of knowledge and technology transfer.