Composite micromechanics: From carbon fibres to graphene

Composite materials are being used increasingly in high-performance engineering applications. The development of the subject of composite micromechanics to understand stress transfer to a high-performance fibre in a low-modulus matrix in a composite is described. It is shown how Raman spectroscopy can now be used to measure stress and strain of individual fibres and so validate the predictions even though reinforcement was considered originally only from a theoretical viewpoint. Recent developments in the field of polymer nanocomposites are then described and it is demonstrated how it is possible to adapt and modify the theories of fibre reinforcement to matrices reinforced by nanoplatelets such as graphene. It is shown that Raman spectroscopy can again be used to map stress and strain in the graphene and that continuum micromechanics is still applicable at the nanolevel. Future trends and challenges in the field are then discussed and a number of unsolved problems are highlighted.