LAUSR

Abstract The viscoelastic properties of urea-formaldehyde (UF) microcapsules is very important for achieving self-healing process in the field of concrete. In this study, the load-displacement relationship of the microcapsule was obtained by micromanipulation technique and the variation of force with time for compression and holding process, from which the properties of elasticity and viscoelasticity were determined. Three viscoelastic models, including 3-parameter Maxwell model, 5-parameter Maxwell model and 4-parameter Burgers model based on shell theory, have been applied to study the viscoelastic properties of the microcapsules. This study has demonstrated that these models consistently predict viscoelastic properties for both ramping and stress relaxation periods. Utilization of the models can enrich the experimental nano-micro material mechanics in interpretation of nanoindentation of microcapsules.