Mechanical properties of composites using ultrafine electrospun fibers

The objective of this research was to show the reinforcing effects of nanofibers in an epoxy matrix and in a rubber matrix using electrospun nanofibers of PBI (polybenzimidazole). The average diameter of the electrospun fibers was around 300 nanometers, which is less than one tenth the diameter and 1/100 the cross sectional area of ordinary reinforcing fibers. The ultrafine fibers provide a very high ratio of surface area to volume. The nanofibers toughened the brittle epoxy resin. The fracture toughness and the modulus of the nanofiber (15 wt%)‐reinforced epoxy composite were both higher than for an epoxy composite made with PBI fibrids (17 wt%), which are whisker‐like particles. In an elastomeric matrix, The Young's modulus and tear strength of the chopped nanofiber‐reinforced styrene‐butadiene rubber (SBR) were higher than those of the pure SBR. Micrographs of the fracture surfaces were obtained by scanning electron microscopy (SEM).