Superior through‐plane thermal conductivity in carbon fibers/spherical graphene/epoxy laminated composites for low‐altitude aircrafts

Abstract The rapid expansion of the low‐altitude economy has driven growing demand for carbon fiber/epoxy composites in applications including unmanned aerial vehicles and electric vertical take‐off and landing aircraft. However, the characteristically low through‐plane thermal conductivity ( λ ⊥ ) of these composites poses a critical thermal conduction limitation, which adversely affects the performance and reliability of onboard electronic systems. In this work, we present an architectural design to improve the λ ⊥ of mesophase pitch‐based carbon fiber (MPCF)/epoxy composites by incorporating precisely engineered spherical thermally reduced graphene (s‐TRG) as a bridging filler. At a loading of 10 wt% s‐TRG and 60 wt% MPCF, the MPCF/s‐TRG/epoxy composite achieves a λ ⊥ of 2.73 W m –1 K –1 , representing a 173.0% improvement over the MPCF/epoxy composite (1.00 W m –1 K –1 ) and about 1.71 times the λ ⊥ of its conventional TRG‐filled analogue (1.60 W m –1 K –1 ). Monte Carlo simulations reveal that the enhancement originates from the isotropic spherical architecture of s‐TRG, which facilitates efficient multi‐point bridging within the three‐dimensional interlaminar space, thereby overcoming the limited through‐plane contact characteristic of planar graphene sheets. This work not only provides an efficient filler structural design strategy for thermal enhancement but also suggests a feasible route toward managing heat in high power density electronics for next‐generation lightweight low‐altitude aircraft. image