Micromechanical modeling and experimental verification of self-healing microcapsules-based composites

Abstract

Recent investigations have focused on the evaluation of the effective elastic properties of microcapsules-based composites theoretically by assuming the constituents’ mechanical properties. The aim of this study is to investigate the effective elastic properties of self-healing microcapsules-based composites (SHMC) theoretically and validate them experimentally. The elastic modulus of the matrix material was evaluated using dynamic mechanical analysis (DMA) of neat polymer samples. Furthermore, the self-healing microcapsules (SHM) elastic modulus was determined through single-microcapsule compression testing followed by finite element modeling. The determined constituents’ elastic properties were used in modeling of SHMC to determine their effective elastic properties analytically. An analytical model, based on Eshelby and Mori–Tanka (E&M–T) two-constituent models, was reformulated and extended to be suitable for a hierarchical approach for solving core–shell–matrix three-constituent SHMC. The results were compared with predictions of the differential-effective medium theory and the rule of mixtures. Finally, all analytical models were compared to experimental results obtained from DMA of 5, 10, and 20 vol% urea-formaldehyde/dicyclopentadiene (UF/DCPD) SHM embedded in epoxy matrix. Good agreement was achieved and the reformulated E&M–T model successfully predicted the elastic properties of SHMC. It was found that the effect of the test uncertainty, the microcapsule geometric parameters for the same batch, and the shell elastic modulus for a given load–deformation curve on the effective elastic properties of SHMC is insignificant. The effective elastic properties depend only on the microcapsules volume fraction up to a certain limit.