Graphene‐Copper Heterogeneous Filler With Amino Groups Significantly Improves the Mechanical and Thermal Conductivity of Carbon Fiber‐Reinforced Copoly (Phthalazinone Ether Sulfone Ketone) Composites

ABSTRACT The weak interfacial bonding problem between graphene (Gr) and the resin matrix restricts the mechanical load‐carrying capacity and heat transfer efficiency of composites. To improve compatibility and enhance interfacial interaction, surface modification treatment of Gr was conducted using p‐aminobenzoic acid and p‐aniline. Additionally, graphene‐copper hetero‐fillers containing amino groups (Gr‐NH 2 ‐Cu) were synthesized. Experimental results demonstrate that the introduction of polar groups effectively improves the interfacial interaction and bonding strength between Gr and the PPBESK resin matrix, leading to a substantial enhancement in the overall performance of the composites. The flexural, compression, tensile, and interlayer shear strengths (ILSS), along with the out‐of‐plane thermal conductivity ( λ ) of the 0.2‐NH 2 ‐optimal composites, reached 1516 MPa, 890 MPa, 1663 MPa, 65 MPa, and 1.884 W/(m·K), respectively, representing increases of 15%, 15%, 9%, 12%, and 246% compared to CF/PPBESK. Furthermore, the additional introduction of Cu nanoparticles more effectively mitigated the aggregation of Gr, significantly strengthening the interfacial bonding between Gr and the resin matrix while simultaneously reducing interfacial thermal resistance. Among these, the 0.2‐Gr‐NH 2 ‐Cu‐3‐optimal composites exhibited the most outstanding overall performance, with flexural, compression, tensile strengths and ILSS reaching 1603 MPa, 940 MPa, 1732 MPa, and 74 MPa, respectively, which are 21%, 21%, 14%, and 27% higher than those of carbon fiber‐reinforced copoly (phthalazinone ether sulfone ketone) (CF/PPBESK) composites, while the λ improved to 2.218 W/(m·K), marking a 307% increase compared to CF/PPBESK composites.