Magnetic alignment of nanotubes for toughening fiber-reinforced composites

W Qiang and XY Zhang and J Lai and YF Yu and ZH Song and X Zhang, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, 301, 110478 (2025).

DOI: 10.1016/j.ijmecsci.2025.110478

This study investigates the multiscale toughening mechanisms of fiber- reinforced polymer (FRP) laminates enhanced with magnetically aligned Fe3O4-grafted carbon nanotubes (CNTs). CNTs were successfully oriented vertically in the fabrication of carbon fiber-reinforced polymer (CFRP), glass fiber-reinforced polymer (GFRP), and hybrid fiber-reinforced polymer (HFRP) laminates to improve their interlaminar fracture toughness. Double cantilever beam (DCB) tests revealed that the aligned CNTs significantly increased Mode I fracture toughness by 40.9 % in CFRP, 34.6 % in GFRP, and 76.3 % in HFRP at an optimal content of 0.3 wt. %. Scanning electron microscopy (SEM) analyses indicated enhanced fiber-matrix interfacial bonding, greater resin plastic deformation, and more tortuous crack paths due to the presence of CNTs. Molecular dynamics (MD) simulations further demonstrated that vertically aligned CNTs provide superior resistance to crack propagation through mechanisms such as nanotube bridging, anchoring, and energy dissipation. These findings offer new insights into the design of multiscale-toughened composite structures and highlight the effectiveness of magnetic alignment strategies in improving interlaminar performance.

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