Synergistic effects of graphene nanoplatelets and carbon nanofibers on thermomechanical fatigue response of modified glass/epoxy composites

Abstract

This study explored the synergistic role of graphene nanoplatelets (GNPs) and carbon nanofibers (CNFs) on the thermomechanical fatigue performance of modified glass fiber-reinforced polymer (GFRP). Three composite materials were investigated including unmodified GFRP, GFRP modified with GNPs (0.75 wt% GNPs), and GFRP modified with hybrid nano-reinforcements (0.375 + 0.375 wt% GNPs and CNFs). Their fatigue strengths were assessed using two thermography-based approaches (i.e. ΔT–σ, and $\dot{q}-\sigma$), with the minimum curvature radius (MCR) and maximum perpendicular distance (MPD) procedures individually incorporated into each approach. The results extracted from thermographic approaches highlighted the negative influence of GNPs on fatigue strength, while HNPs contributed to fatigue strength improvement. The $S-N$ curves were constructed as a reference to assess the reliability of fatigue strengths derived from thermographic approaches. Unlike the MCR, incorporating MPD analysis into ΔT–σ and $\dot{q}-\sigma$ approaches demonstrated good alignment with fatigue strength values derived from $S-N$ curves. Nevertheless, the introduced MPD-based $\dot{q}-\sigma$ approach provided a more reliable strategy for assessing the fatigue strengths of these composites. Moreover, the $S-N$ curve analysis, supported by thermal responses and microscopic observations, illustrated that while GNPs enhanced the low-cycle fatigue performance, incorporating HNPs notably improved the life of modified GFRP composite across both low- and high-cycle regimes.