Fracture toughness of functionally graded nanocomposite in quasi-static loading

Alumina nanoparticles of two shapes (spherical and rod) were dispersed in epoxy resin by sonication technique to synthesize functionally graded polymer nanocomposites (FGPNC). Weight percentage (wt%) of nanoparticles was varied in the thickness direction to achieve the gradation in samples. In a vertical acrylic mould, nanocomposite layers containing 0, 0.25, 0.5, 0.75 and 1 wt% of nanoparticles were sequentially cast to prepare the samples of FGPNC. Transmission electron micrographs and in situ EDX mapping showed the uniform dispersion of alumina nanoparticles. Fracture toughness of FGPNC samples was evaluated for three different orientations of crack by three-point bending method. In two cases, the crack was created along the thickness direction, while the load was applied from either nanocomposite side or epoxy side. Crack was introduced in the perpendicular direction to gradation in the third case. In the case of nanocomposite side loading, FGPNC (spherical) and FGPNC (nanorods) had 38% and 25% higher fracture toughness, respectively, compared to that of neat epoxy (layered). 25% and 8% of improvement in fracture toughness were observed for FGPNC having nanorods and spherical particles, respectively, for the sample with the crack in the perpendicular direction to the direction of gradation.

Automated summary

Alumina nanoparticles of two shapes (spherical and rod) were dispersed in epoxy resin using sonication technique to synthesize functionally graded polymer nanocomposites (FGPNC). The weight percentage of nanoparticles was varied in the thickness direction to achieve gradation in samples. The results showed that FGPNC samples with nanoparticles exhibited higher fracture toughness in different crack orientations.