Fracture and energetic strength scaling of epoxy-resins toughened with multi-walled carbon nanotubes

The paper studies the toughening effect of multi-walled carbon nanotubes (MWCNTs) as nanofiller on epoxy resins. We use the size-effect testing methodology to prepare geometrically similar epoxy specimens with varying MWCNT weight fractions. We tested 72 single-edge notched samples and 72 unnotched samples in tensile loading. The addition of MWCNTs resulted in a non-negligible fracture process zone (FPZ). A size-dependent strength is observed and is modeled using type-II energetic scaling law. The mode-I fracture toughness and the FPZ size increased with the MWCNT content, peaked at optimum weight fraction, and then decreased at higher weight fraction. Fractography showed the growth of nanoclusters with an increase in the MWCNT content. We speculate this reduction in the fracture toughness at higher weight fractions is due to failure occurring in the nanoclusters instead of the nanofiller-reinforced matrix.

Automated summary

The paper investigates the impact of multi-walled carbon nanotubes (MWCNTs) as nanofiller on the toughening effect of epoxy resins. The results show that the addition of MWCNTs leads to a significant fracture process zone (FPZ), and the fracture toughness and the FPZ size increase with the MWCNT content, reaching a peak at the optimum weight fraction and then decreasing at higher weight fractions. Fractography reveals the growth of nanoclusters with an increase in the MWCNT content.