The Simultaneous Effect of Microcapsules and Silica Nanoparticles on the Mechanical-healing Properties of Glass Fibers-Epoxy Smart Composites

The aim of this study is to assess the simultaneous effect of incorporating capsulated healing agent and silica nanoparticles on the mechanical-healing behaviors of glass fibers/epoxy composites. To do so, the 14 wt.% capsulated epoxy healing agent by urea-formaldehyde polymeric shell and the various percentage of silica nanoparticles (1, 3 and 5 wt.%) were added into the glass fibers-epoxy composites for studying the healing behavior under the tensile and flexural conditions. After the damaging and healing processes of composites, the maximum healing efficiency in flexural strength (110.7 %) was seen in the composite containing 5 wt.% silica nanoparticles. But the highest healing efficiency in the tensile strength (64. 2%) belonged to the smart composite with 3 wt.% silica nanoparticles. The silica nanoparticles improved the recovery capability of mechanical properties by changing the damage modes into the smart composites. Filling the micro-voids and reducing the effect of agglomerated nanoparticles by healing agent were the effective mechanisms, which improved the mechanical recovery capability. The other observed phenomena by field emission scanning electron microscope were improving the adhesion between glass fibers and epoxy, creating the micro-voids by silica nanoparticles, wasting the crack propagation energy by stick-slip method and reducing the flow ability of healing agent by silica nanoparticles.