Synergistic strengthening and toughening of epoxy resins enabled by ultra-low content pristine single-walled carbon nanotubes

Abstract

The inherent brittleness of traditional epoxy resins limits their application in high-performance fields. In this study, single-walled carbon nanotubes (SWCNTs) were incorporated into bisphenol-A epoxy resin to investigate their effects on mechanical properties. SWCNTs/EP nanocomposites with varying mass fractions (0.0018 wt% to 0.0026 wt%) were fabricated using a combination of homogenization and ultrasonic dispersion. Mechanical testing revealed that the tensile, flexural, and impact properties exhibited a consistent trend of initially increasing and subsequently decreasing with higher SWCNT content. The optimal mechanical performance was achieved at an SWCNT mass fraction of 0.0022 wt%. At this concentration, the tensile strength, flexural strength, and impact strength reached 85.1 MPa, 136.8 MPa, and 40.3 kJ/m2. These values represent improvements of 23.0%, 14.5%, and 38.9% over the unmodified neat resin. Microstructural analysis using scanning electron microscopy (SEM) indicated a transition from brittle to ductile fracture characteristics. The toughening mechanism is primarily attributed to the synergistic effects of crack deflection and nanotube pull-out.