A thorough knowledge and understanding of the structure–property relationship between thermal conductivity and C-fiber morphology is important to estimate the behavior of carbon fiber components, especially under thermal loading. In this paper, the thermal conductivities of different carbon fibers with varying tensile modulus were analyzed perpendicular and parallel to the fiber direction. Besides the measurement of carbon fiber reinforced polymers, we also measured the thermal conductivity of single carbon fibers directly. The measurements clearly proved that the thermal conductivity increased with the tensile modulus both in fiber and perpendicular direction. The increase is most pronounced in fiber direction. We ascribed the increase in tensile modules and thermal conductivity to increasing anisotropy resulting from the orientation of graphitic domains and microvoids.

Relationship between the tensile modulus and the thermal conductivity perpendicular and in the fiber direction of PAN-based carbon fibers
    Abstract
        Graphical abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
        2.2 Resin preparation and curing
        2.3 Prepreg production and consolidation
        2.4 Determination of fiber volume content
        2.5 Thermal conductivity measurements of composites
        2.6 Nanostructural analysis of PAN fibers
        2.7 Thermal conductivity measurements of single fibers
    3 Results and discussion
        3.1 Morphology of fibers
        3.2 Thermal conductivity of laminates
        3.3 Thermal conductivity of single fiber measurements
    4 Conclusions
    Acknowledgements 
    References

• Simon Bard(Polymer Engineering, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Bavaria, Germany)
• Thomas Tran(Bavarian Center for Battery Technology (BayBatt), Bavarian Polymer Institute, and Bayreuth Center for Colloids and Interfaces, Department of Chemistry, Physical Chemistry I, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Bavaria, Germany)
• Florian Schönl(Polymer Engineering, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Bavaria, Germany)
• Sabine Rosenfeldt(Bavarian Center for Battery Technology (BayBatt), Bavarian Polymer Institute, and Bayreuth Center for Colloids and Interfaces, Department of Chemistry, Physical Chemistry I, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Bavaria, Germany)
• Martin Demleitner(Polymer Engineering, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Bavaria, Germany)
• Holger Ruckdäschel(Polymer Engineering, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Bavaria, Germany)
• Markus Retsch(Bavarian Center for Battery Technology (BayBatt), Bavarian Polymer Institute, and Bayreuth Center for Colloids and Interfaces, Department of Chemistry, Physical Chemistry I, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Bavaria, Germany)
• Volker Altstädt(Polymer Engineering, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Bavaria, Germany) Corresponding author