Mechanical behavior and self-healing mechanism of polyurea-based double-walled microcapsule/epoxy composite films

The built-in self-healing capability, which can substantially repair the damaged polymeric materials, has become research hotspots in recent years. In this study, double-walled microcapsules were introduced in epoxy composite films to obtain a strong self-healing ability, and the embedded microcapsules were produced by the previous studies. The microstructure and micromechanical properties of the composite films were characterized by scanning electron microscope (SEM) and nanoindentation, and its mechanical behaviors and self-healing mechanism during the tensile process were tested by using the digital speckle correlation method (DSCM). The results showed that the epoxy composite films with 3.0 wt% microcapsules had the highest mechanical property improvement and the composite films with 5.0 wt% microcapsules achieved the highest self-healing efficiency of 61 %. In addition, two typical self-healing behaviors of the composite films were obtained by analyzing and interpreting the Y-direction strain field and StS value through DSCM, the mechanism of selfhealing procedure was proposed.