Improving the interlaminar fracture toughness of carbon fiber/epoxy composites using clustered microcapsules

The composite laminates are susceptible to delamination between reinforcing plies during their long-term service. In this paper, we propose a modified carbon fiber/epoxy composite laminate with embedded clustered dual-component microcapsules in order to increase the interlaminar fracture toughness of the lamina. The details of microcapsules were illustrated using scanning electron microscope (SEM). The modified CF/EP composite laminates were fabricated using hot-compaction technique. Mode I interlaminar fracture tests were conducted using double cantilever beam specimens, then the values of opening fracture toughness G_IC were calculated to evaluate the toughening effect of modified laminates. The toughening mechanism was revealed and discussed through micrographs of the fracture surfaces obtained by ultra-depth microscope and SEM. The results show that clustered microcapsules after polymerization are equal to special Z-pinning, significantly enhancing the ability of crack arrest, and largely and roundly improved the G_IC values of resultant composite laminates. Meanwhile, the clustered microcapsules and matrix resin formed a second-phase material layer, which also absorbed the fracture energy and suppressed the expansion of cracks.