Experimental study on interlaminar fracture toughness of carbon/epoxy composites embedded with weft-knitted electrothermal layer

To develop carbon/epoxy composites with electrothermal anti-icing/de-icing capabilities for aircraft structural components, the nickel-chromium (Cr20Ni80) wires were weft-knitted into plain, 1×1 rib, and interlock electrothermal fabrics. Serving as the electrothermal layer, these were embedded into the midplane of carbon/epoxy laminates and prepared via vacuum-assisted resin infusion. Under a power density of 0.3 W/cm² for 180 s, all composites exceeded 70℃, with a uniform surface temperature distribution. Short-beam shear and Mode I interlaminar fracture tests indicated that, compared to the pristine carbon/epoxy composites, for specimens with plain, 1×1 rib, and interlock electrothermal layers, the shear strength retention rates reached 84.60%, 79.34% and 87.70%; the initial fracture toughness (G_IC^init) retentions reached 74.36%, 91.03% and 96.15%, the propagation fracture toughness (G_IC^prop) retentions reached 97.22%, 93.52% and 88.89%, respectively. Digital image correlation and profilometry were employed to observe and analyze the strain distribution and fracture morphology of the specimens, Research demonstrates that the loop structure of the weft-knitted electrothermal fabric plays a role in regulating the interlaminar failure behavior.