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

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. (Figure presented.).