Enhancing the Interlaminar Properties of <scp>CF</scp> / <scp>PPESK</scp> Composites Through the Interlayer Directional Distribution of the Core‐Shell Structure <scp>PZS</scp> @ <scp>CNTs</scp>

ABSTRACT The delamination damage caused by resin‐rich interlayers severely restricts the engineering application of carbon fiber reinforced thermoplastic composite (CFRTP) laminates. To overcome this challenge, this study innovatively combines the core‐shell structured polyphosphazene‐carbon nanotubes filler (PZS@CNTs), which is constructed in situ via a non‐covalent bonding strategy without damage, with a two‐step solution impregnation process. This strategy enables the directional introduction of PZS@CNTs into the resin‐rich interlayer regions of CF/PPESK composites, thereby constructing a nano‐reinforced network in the weak interlayer areas. The End‐Notched Flexure (ENF) test demonstrated that the introduction of PZS@CNTs increased the mode II interlaminar fracture toughness (G II ) from 1254 to 2181 J/m 2 , a significant increase of 74%. Scanning electron microscopy (SEM) and metallographic fracture analysis indicate that the toughening mechanism originates from the significant energy dissipation caused by crack deflection induced by PZS@CNTs. Concurrently, this method does not compromise the in‐plane mechanical properties—the flexural strength is increased by 22%.