Significantly Enhanced Mechanical, Thermal, and Electromagnetic Interference Shielding Properties of CFRP Composites via an Optimized Spatial Arrangement of Fibers Through the Spreading Process

ABSTRACT This study reveals that ultrathin carbon fiber reinforced polymer (CFRP) composites fabricated by the ultra‐thinning of large‐tow CFs exhibit significantly enhanced multifunctional properties. Commercial 7 mm wide CF bundles were spread to widths of 13, 19, 24, and 28 mm, with optimal properties observed at 24 mm (CF ₂₄ ). The CF ₂₄ composite showed enhanced mechanical properties, with transverse fiber bundle test tensile strength, interlaminar shear strength, and compressive strength increasing by 17.79%, 20.23%, and 17.10%, respectively, compared to the unspread sample. Thermal conductivity was also notably improved, with in‐plane and through‐plane thermal diffusivity rising by 243.14% and 92.59%. Electrical conductivity increased as well, with resistivity reductions of 18.39% (fiber direction) and 38.32% (thickness direction), resulting in an electromagnetic interference shielding effectiveness of 37.52 dB. These findings validate the ultra‐thinning process as a low‐cost, designable method for creating structure–function‐integrated CFRP composites, promising for demanding fields like aerospace and new energy.