Experimental, analytical and numerical study of water diffusion in unidirectional composite materials – Interphase impact

This study is a first approach of water diffusion in unidirectional (UD) composite, associating experimental measurements, analytical and numerical modelling. In the initial state, an interphase of several micrometers width around each monofilament is revealed from micro-thermal analysis measurements. This interphase is characterized by a higher molecular mobility than the bulk resin, which is a determining parameter for water diffusion. Water absorption measurements on both the resin and the UD composite show a Fickian kinetic in first approximation. A finite element analysis of water diffusion in the composite clearly shows the influence of the interphase properties on water diffusion kinetic.

► An interphase of several micrometers width present around each monofilament.
► Numerical model with barrier effect (contact fibres) and closed matrix areas.
► Matrix strongly modified by the presence of fibres.
► Matrix diffusion coefficient higher to fit the experimental data.