Influence of physical ageing and fibre proximity on the local mechanical response of the Elium® thermoplastic composite matrix

[Display omitted] •Micromechanical characterisation of matrix properties in a fibre-reinforced thermoplastic (Elium) composite by nanoindentation and atomic force microscopy.•Assessment of the dual influence of physical ageing and fibre proximity on the mechanical response of the Elium polymer matrix.•Use of inference statistics and finite element simulation to strengthen the conclusions drawn from micromechanical tests. The prediction of the micromechanical response of fibre-reinforced polymer composites with numerical models relies on the assumption that the matrix behaves like a bulk sample of the same polymer. Yet, the presence of fibres likely impacts the thermochemical history and mechanical behaviour of the matrix (e.g. formation of an interphase during processing). In this work, micromechanical analysis of a thermoplastic polymer matrix is performed on glass fibre-reinforced composite samples manufactured by vacuum infusion and in-situ polymerisation. The interphase thickness and mechanical behaviour are assessed by atomic force microscopy (AFM). The mechanical properties of the matrix beyond the interphase are measured by nanoindentation and AFM in intra- and inter-tow matrix pockets, for different levels of natural physical ageing. While the distance to the nearest fibre does not significantly impact the polymer properties at a given ageing time, fibre proximity affects the rate and extent of physical ageing experienced by the polymer.