Graphene-skinned welded glass fiber felt for anisotropic thermal management

Materials that can deliver in-plane heat diffusion and through-plane thermal insulation are essential for thermal management in extreme environments. However, integrating these opposing functions into a single material remains highly challenging because thermal conduction and insulation are inherently contradictory. Here, we report an anisotropic graphene-skinned welded glass fiber felt (Gr-wGFF) produced through a one-step process that couples the in situ growth of vertically aligned graphene nanosheets on glass fibers by plasma-enhanced chemical vapor deposition (PECVD) with the concurrent thermal welding of fiber junctions. This approach generates a continuous and covalently bonded thermal transport network at an ultralow graphene content (~0.86 wt.%), thereby overcoming the high percolation threshold commonly encountered in conventional composites. The resulting structure exhibits pronounced anisotropy: at an areal density of 430 g·m⁻², the Gr-wGFF achieves an in-plane thermal conductivity of 1.6 W·m⁻¹·K⁻¹ and a through-plane conductivity of 0.2 W·m⁻¹·K⁻¹, corresponding to an anisotropy ratio of 8. When embedded into a phenolic resin (PR) matrix, the composite maintains high thermal anisotropy with good mechanical strength and flame retardancy. This multifunctional integration offers a solution for advanced thermal-structural applications in extreme environments.