Tailoring the interfacial properties of glass fiber-epoxy microcomposites through the development of a self-healing poly(ϵ-caprolactone) coating

The aim of this study was the development and characterization of a continuous poly(ε-caprolactone) (PCL) coating, which was applied on glass fibers by a fluid coating method, in order to tailor the interfacial properties in glass fiber-epoxy microcomposites. Scanning electron microscopy revealed that a uniform coating was formed without noticeable discontinuities or irregularities, and its thickness increased with the deposition speed. To achieve consistent results with this approach, it is essential to consider the homogeneity of the coating thickness, which is influenced by the viscosity of the solution. The PCL-coated fibers were used for the preparation of microcomposites combined with epoxy resin (EP). The samples were tested in the microdebonding configuration to determine the interfacial shear strength (IFSS) and to assess their interfacial self-healing capability. For all deposition speeds, no significant degradation of interfacial adhesion was observed indicating the applicability of PCL coating on glass fibers. However, a decrease in self-healing efficiency was observed after multiple self-healing stages. The possible cause was identified in the progressive alteration of the EP droplet's shape after repeated microdebonding tests. This phenomenon altered the stress distribution along the fiber-matrix contact area and, therefore, underestimated the values of interfacial adhesion and self-healing efficiency. Hence, the experimental results from microdebonding tests were presented along with a finite element analysis of the interfacial region, in order to provide a comprehensive understanding of the debonding and self-healing mechanisms after multiple repairing steps.