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 on glass fibers by plasma-enhanced chemical vapor deposition (PECVD) with the concurrent thermal welding of fiber junctions. This approach generates a continuous, 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 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.