Experimental characterisation and modelling of mechanical behaviour of microcapsules

Results of experimental characterisation and modelling of mechanical behaviour of microcapsules for self-sensing polymer composites are presented. Melamine–formaldehyde microcapsules were selected for this purpose. The average diameter, size distribution, and shell thickness of microcapsules were evaluated from scanning electron microscopy images. Compressive properties of the shell material were evaluated in several ways. AFM measurements allowed estimating stiffness and strength of a single microcapsule. In parallel, modelling of the mechanical behaviour of a single microcapsule was performed. Buckling of a thin-walled spherical shell under external pressure was considered and closed-form solution in a linear statement was obtained. The results of analytical calculations were compared with FEM modelling. Two demonstrator thin-shells with the radius of centimetre scale, hollow and filled with water, were tested in compression between two rigid plates. The results of their numerical analysis obtained by FEM models developed are in good agreement with experimental results.