Mechanical properties of carbon‐fiber‐reinforced epoxy composites modified by carbon micro‐ and nanofillers

Hybrid composite materials reinforced with unidirectional fibers and small‐scale micro‐ or nanoparticles provide benefits compared to traditional composites. The present paper shows the experimental investigation of carbon‐fiber‐reinforced polymers modified by the addition of 0.5–5 wt% of milled carbon fibers and 0.1–0.5 wt% of single‐wall carbon nanotubes. Both fillers were analyzed from technological point of view. The impact on mechanical and physical properties was revealed and discussed. Main attention was paid to quasi‐static tensile and flexural properties as well as fatigue behavior under tension–tension mode. The maximal improvement in static tensile strength by 8.6% (from 682 to 741 MPa) and flexural strength by 14% (from 649 to 740 MPa) was achieved by the addition of 0.3 wt% single‐wall carbon nanotubes. Short beam shear strength increased by 18%. Fatigue durability was highly improved as well. The strengthening mechanisms are attributed to the improvement of shear interfacial properties. In contrast to single‐wall carbon nanotubes, milled carbon fibers enhanced the properties by 3%–9% only at static loading, while fatigue properties are negatively affected.