Enhancement of Thermal Conductivity and Through‐Thickness Mechanical Properties in Pitch‐Based Carbon Fiber/Epoxy Composites via Stitching Process

In this study, an I‐shaped through‐thickness stitched pitch‐based carbon fiber (PCF)/epoxy composite is developed to simultaneously achieve through‐thickness heat dissipation, in‐plane heat spreading, and Mode I delamination resistance. By employing high‐conductivity pitch‐based carbon fiber bundles as both continuous through‐thickness heat‐transfer paths and crack‐bridging reinforcements, the proposed composite improves directional thermal transport and resistance to opening relative to unstitched pitch‐based laminates. Their exposed ends are compressed into I‐shaped heads that anchor the stitches against pull‐out. The stitch spacing is set to 10, 5, and 3 mm. Thermal conductivity is measured by laser flash analysis (LFA), and the Mode I response is evaluated by double cantilever beam (DCB)‐type tests. Results demonstrate that the through‐thickness conductivity increases from 1.73 to 5.30 W/m·K and the in‐plane conductivity from 100.69 to 140.84 W/m·K, while the maximum opening load rises from 196.9 to 299.4 N at 5 mm spacing. A non‐monotonic thermal–mechanical trade‐off emerges at the narrowest stitch spacing.