Mesoscopic study on mechanical properties and dynamic damage characteristics of self-healing microcapsule

In the field of smart materials, microencapsulated self-healing technology has received a lot of attention in recent years. However, the existing microcapsule preparation techniques continue to have difficulties controlling the structural parameters of microcapsules at the microscopic scale, and there are difficulties in investigating the mechanical properties of microcapsules based on a single structural parameter experimentally. In addition, the commonly used Finite Element Method (FEM) also has significant limitations in investigating dynamic damage problems in non-homogeneous, discontinuous materials. To address the aforementioned issues, the Discrete Element Method (DEM) is used to create a numerical model of a single microcapsule. The reliability and feasibility of the discrete element model are demonstrated by utilizing the microcapsule's mechanical intrinsic model and experiments. Further, the discrete element models are employed to analyze the influence of microcapsule structure/material parameters on the crack resistance and fracturability of a single microcapsule, discuss the micromechanics of the microcapsule damage process, and predict the rupture mode and rupture location of a single microcapsule. It is shown that (1) the larger the wall thickness and smaller the diameter of the microcapsule, the stronger the deformation resistance of the microcapsule, but the rupture load and nominal rupture stress increase linearly with the increase of wall thickness and decrease nonlinearly with the increase of diameter; (2) the maximum stress field during compression of small deformation microcapsules occurs in the polar region, and the initial scattered damage appears in the polar region, also the scattered damage gradually develop into one or more main cracks along the meridian and (3) large deformation microcapsule compression through three stages of elastic deformation, plastic deformation and hardening, and gradually occur three kinds of the morphology of "spherical", "drum-shaped" and "butterfly-shaped", while rupture after producing scattered cracks and fragments in the near-polar region.