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.

Keywords

carbon fiber / epoxy resin / spherical thermally reduced graphene / through-plane thermal conductivity

References

[1] Miao N, Li M, Ai Q, Ge Q, Fan L, Ding X. SiO anodes with interface modulation Bi₂Cu wrapped in N-doping porous carbon for enhanced fast-charging in Lithium-ion batteries. J Energy Storage. 2026; 141:119197.

[2] Tan H, Guo Z, Yan J, Zhang D, Chen Y, Zhang H. Advancing low-carbon smart cities: Leveraging UAVs-enabled low-altitude economy principles and innovations. Renew Sustain Energy Rev. 2025; 222:115942.

[3] Wang S, Wang W, Chen Y, et al. Synergistic effect of interfacial silane film and laser texturing on joining characteristics of pretreated Al/CFRTP friction stir welded joints. Mater Des. 2025; 259:114774.

[4] Li M, Qiu P, Wen H, Ruan K, Gu J. Thermochromic hydrogels for thermal management smart windows. Sci Bull. 2026; 71(4): 900-920.

[5] Hu W, Cheng H, Wang S, et al. A coupled FEM-FFT concurrent multiscale method for the deformation simulation of CFRPs laminate. Compos Struct. 2024; 342:118246.

[6] Iyer V, Petersen J, Geier S, Wierach P. Development and Multifunctional Characterization of a Structural Sodium-Ion Battery Using a High-Tensile-Strength Poly(ethylene oxide)-Based Matrix Composite. ACS Appl Energ Mater. 2024; 7(9): 3968-3982.

[7] Lin Y, Gigliotti M, Lafarie-Frenot MC, Bai J, Marchand D, Mellier D. Experimental study to assess the effect of carbon nanotube addition on the through-thickness electrical conductivity of CFRP laminates for aircraft applications. Compos Part B Eng. 2015; 76: 31-37.

[8] Wang S, Ruan K, Guo Y, Kong J, Gu J. Thermally Conductive Naphthalene Epoxy Resin by Tailoring Flexible Chain Length and Liquid Crystal Structure. Angew Chem Int Edit. 2025; 64(21):e202501459.

[9] Zeng X, Shi X, Lin Y, et al. Improved interfacial compatibility of carbon fibers/PEEK laminated composites via incorporating biphenyl-branched poly(aryl-ether-nitrile). J Mater Sci Technol. 2026; 255: 259-269.

[10] Zhang Y, Wei J, Liu C, Hu Y, She F. Reduced graphene oxide modified Ti/CFRP structure-function integrated laminates for surface Joule heating and deicing. Compos Part A Appl Sci Manuf. 2023; 166:107377.

[11] Zhu H, Fu K, Huang T, et al. Highly conductive CFRP composite with Ag-coated T-ZnO interlayers for excellent lightning strike protection, EMI shielding and interlayer toughness. Compos Part B Eng. 2024; 279:111448.

[12] Ge X, Xu S, Zhang T, et al. Self-adaptive mechanical metasurface enabling zero-power-consumption thermal management of electronic devices. Adv Mater. 2025; 38(14):e09005.

[13] Ji Z, Huang X, Wang X, et al. Local mechanical sintered thermal liquid bridge for anti−/de-icing surface with thermal management and temperature warning. Chem Eng J. 2025; 512:162337.

[14] Zhong X, Ruan K, Gu J. Enhanced Intrinsic Thermal conductivity of aromatic polyesters through dual strategies of hydrogen bonding and π-π stacking. Sci China Chem. 2025.

[15] Cheng B, Ruan K, Li M, et al. Improved intrinsic thermal conductivity of highly crystalline polyimide films by regulating aggregation structures. Macromolecules. 2026; 59(4): 2601-2612.

[16] Xu R, Zhu Z, Zhang H, et al. Synergistic material–structure engineering for mid-infrared thermal management in textiles. Small. 2025; 21(47):e09257.

[17] Jia M, Tang L, Lin Y, et al. Interfacial engineering for improving thermal conductivities of BNNS/PNF nanocomposite paper with superior electrical insulation and mechanical properties. J Mater Sci Technol. 2026; 254: 126-134.

[18] Ma T, Ruan K, Guo Y, Shi X, Xu BB, Gu J. Thermal conduction pathways with specific angles and distributions to improve the thermal conductivity of copper wire/poly(lactic acid) composites. J Mater Sci Technol. 2026; 262: 261-269.

[19] Zhang K, Zhang J, Dang L, et al. High intrinsic thermal conductivity and low dielectric constant of liquid crystalline epoxy resins with fluorine-containing semi-IPN structures. Sci China Chem. 2025; 68(6): 2615-2627.

[20] Lin W, Yu C, Sun C, et al. Enhancing the thermal conductivity of epoxy composites via constructing oriented ZnO nanowire-decorated carbon fibers networks. Materials. 2024; 17(3): 649.

[21] Wu X, Shi S, Tang B, et al. Achieving highly thermal conductivity of polymer composites by adding hybrid silver–carbon fiber fillers. Compos Commun. 2022; 31:101129.

[22] Fontana M, Ramos R, Morin A, Dijon J. Direct growth of carbon nanotubes forests on carbon fibers to replace microporous layers in proton exchange membrane fuel cells. Carbon. 2021; 172: 762-771.

[23] Qin J, Wang C, Lu R, et al. Uniform growth of carbon nanotubes on carbon fiber cloth after surface oxidation treatment to enhance interfacial strength of composites. Compos Sci Technol. 2020; 195:108198.

[24] Fang H, Bai S, Wong CP. Microstructure engineering of graphene towards highly thermal conductive composites. Compos Part A-Appl S. 2018; 112: 216-238.

[25] Huang K, Pei S, Wei Q, et al. Highly thermally conductive and flexible thermal interface materials with aligned graphene lamella frameworks. ACS Nano. 2024; 18(34): 23468-23476.

[26] Ruan K, Li M, Pang Y, et al. Molecular brush-grafted liquid crystalline hetero-structured fillers for boosting thermal conductivity of polyimide composite films. Adv Funct Mater. 2025; 35(41):2506563.

[27] Wu Z, Xu C, Ma C, Liu Z, Cheng H, Ren W. Synergistic effect of aligned graphene nanosheets in graphene foam for high-performance thermally conductive composites. Adv Mater. 2019; 31(19):1900199.

[28] Zhao H, Yu M, Liu J, Li X, Min P, Yu Z. Efficient preconstruction of three-dimensional graphene networks for thermally conductive polymer composites. Nano Micro Lett. 2022; 14(1):129.

[29] Lu X, Liu J, Shu C, et al. Densifying conduction networks of vertically aligned carbon fiber arrays with secondary graphene networks for highly thermally conductive polymer composites. Adv Funct Mater. 2025; 35(11):2417324.

[30] Zhang S, Lu X, Liu J, et al. A biomimetic thermal conduction network enables metal-level thermal conductivity in polymer nanocomposites. ACS Nano. 2025; 19(41): 36663-36674.

[31] Wang B, Li N, Cheng S, et al. Thermal conductivity and mechanical properties enhancement of CF/PPBESK thermoplastic composites by introducing graphene. Polym Compos. 2022; 43(5): 2736-3745.

[32] Yao S, Lee S, Li H, Jin F, Park S. Enhanced thermal conductivity of carbon fibers/silanized graphene/epoxy matrix composites. Carbon Lett. 2024; 34(2): 647-655.

[33] Hansen MJ, Rountree KS, Irin F, Sweeney CB, Klaassen CD, Green MJ. Photodegradation of dispersants in colloidal suspensions of pristine graphene. J Colloid Interface Sci. 2016; 466: 425-431.

[34] Li Z, Chu J, Yang C, et al. Effect of functional groups on the agglomeration of graphene in nanocomposites. Compos Sci Technol. 2018; 163: 116-122.

[35] Zeinedini A, Shokrieh MM. Agglomeration phenomenon in graphene/polymer nanocomposites: Reasons, roles, and remedies. Appl Phys Rev. 2024; 11(4): 41301.

[36] Guo H, Zhao H, Niu H, et al. Highly thermally conductive 3D printed graphene filled polymer composites for scalable thermal management applications. ACS Nano. 2021; 15(4): 6917-6928.

[37] Li X, Shao L, Song N, Shi L, Ding P. Enhanced thermal-conductive and anti-dripping properties of polyamide composites by 3D graphene structures at low filler content. Compos Part A-Appl S. 2016; 88: 305-314.

[38] Shao L, Shi L, Li X, Song N, Ding P. Synergistic effect of BN and graphene nanosheets in 3D framework on the enhancement of thermal conductive properties of polymeric composites. Compos Sci Technol. 2016; 135: 83-91.

[39] Eksik O, Bartolucci SF, Gupta T, Fard H, Borca-Tasciuc T, Koratkar N. A novel approach to enhance the thermal conductivity of epoxy nanocomposites using graphene core–shell additives. Carbon. 2016; 101: 239-244.

[40] Badakhsh A, Han W, Jung S, An K, Kim B. Preparation of boron nitride-coated carbon fibers and synergistic improvement of thermal conductivity in their polypropylene-matrix composites. Polymers. 2019; 11(12):2009.

[41] Wang H, Guo Q, Wang S, Gao L, Shi X. Enhanced delamination resistance and through-thickness thermal conductivity of carbon fiber epoxy resin composites by in situ generation of interconnected thick oriented matrix-carbon nanotube layer. Compos Part B Eng. 2025; 297:112297.

[42] Li X, Xu T, Cao W, et al. Graphene/carbon fiber network constructed by co-carbonization strategy for functional integrated polyimide composites with enhanced electromagnetic shielding and thermal conductive properties. Chem Eng J. 2023; 464:142595.

[43] Lu N, Sun X, Wang H, et al. Synergistic effect of woven copper wires with graphene foams for high thermal conductivity of carbon fiber/epoxy composites. Adv Compos Hybrid Mater. 2024; 7(1): 29.

[44] Noh YJ, Kim SY. Synergistic improvement of thermal conductivity in polymer composites filled with pitch based carbon fiber and graphene nanoplatelets. Polym Test. 2015; 45: 132-138.

[45] Sun Y, Wang S, Li M, Gu Y, Zhang Z. Improvement of out-of-plane thermal conductivity of composite laminate by electrostatic flocking. Mater Des. 2018; 144: 263-270.

[46] Wu Z, Dong J, Teng C, et al. Polyimide-based composites reinforced by carbon nanotube-grafted carbon fiber for improved thermal conductivity and mechanical property. Compos Commun. 2023; 39:101543.

[47] Yang X, Wang N, Li X, et al. Integrated thermal conductive and electromagnetic interference shielding performance in polyimide composite: impact of carbon felt-graphene van der Waals heterostructure. Macromol Rapid Commun. 2024; 45(22):2400527.

[48] Fang C, Zhang J, Chen X, Weng GJ. Calculating the electrical conductivity of graphene nanoplatelet polymer composites by a Monte Carlo method. Nanomaterials. 2020; 10(6): 1129.

[49] Zhou J, Song B, Li M, Liu T, Chen G, Ding Z. Umklapp scattering is not necessarily resistive. Phys Rev B. 2018; 98(18):180302.

[50] Zhong X, Gu J. Core-shell Co-C@CNT engineered to enable concurrent thermal conductivity and microwave absorption for Poly(4, 4′-dihydroxybiphenyl isophthalate). Trans Mater Res. 2026; 2(2):100184.

RIGHTS & PERMISSIONS

2026 The Author(s). InfoMat published by UESTC and John Wiley & Sons Australia, Ltd.