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In this study, the effect of using an epoxy healing agent containing silica nanoparticles instead of the neat epoxy healing agent on the self-healing ability of glass fibers/epoxy composites under the flexural, tensile and shear loadings was assessed. For doing this, in the first step, the silica nanoparticles (0, 1, 2 and, 3 wt.%) were dispersed into the ethyl acetate/epoxy healing agent. Then, these mixtures were encapsulated with the urea-formaldehyde polymer by an in-situ polymerization method. Finally, the glass fibers/epoxy composite containing 14 wt.% microcapsules along with 2 wt.% NiCl2(imidazole)4 catalyst were fabricated. To understand how the mechanical-healing behaviors of these composites under the various mechanical loads, these composites were destructed with a quasi-static penetration test for the creation of delamination damage. The healing process was done by the thermal activation method. The obtained results showed that the highest healing efficiency under the flexural, tensile and shear loads belonged to the composite containing 1 wt.% nanosilica into the healing agent, which were 89.8, 87.8, and 156.8%, respectively. The hackles of microcapsules, reduction in the thickness of microcapsules, formation of nanocomposite healing shell and the agglomeration of silica nanoparticles on the healed area were the influence factors on the healing ability of these composites. This work can give a view for healing the microcracks into composite structures by nanocomposite healing agents, which have the higher healing ability and better performance under mechanical loads than conventional healing agents.

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