We designed and tested a manufacturing process that resulted in the formation of composites with maximized electrical conductivity and optimized electromagnetic interference (EMI) shielding effectiveness (SE) properties. Single-walled carbon nanotube (SWCNT) paper, which is a microscopic aggregate of van der Waals force interaction, was impregnated with semi-cured epoxy to make SWCNT prepregs. These prepregs were completely cured into SWCNT/epoxy composites. Fabricating and curing processes were executed under proper temperature cycle depending on the time. We inspected SWCNT paper and the interfacial state between the SWCNTs and epoxy in the composite with a field emission-scanning electron microscopy and calculated the SWCNT weight fraction through thermogravimetric analysis measurements. Using these observations, electrical conductivity and EMI SE were investigated according to thickness which could be controlled by the suggested manufacturing process as 1-, 5- and 10-layer composites. Finally, we determined ideal composite thickness and the associated number of prepreg layers using skin depth theory.

An enhanced process for shaping thermoset fiber-reinforced composites using Modified Double-Diaphragm Forming (mDDF) in Prepreg Compression Molding (PCM) is proposed to address limitations in conventional forming quality. To minimize surface defects, prepregs were pre-cut to reduce wrinkle formation and trimmed after preforming. Complex geometries were managed through draping analysis, which enabled identification and mitigation of wrinkle-prone regions. A challenging layup configuration (±45/0/90/0/90/0/±45) was selected, and temperature-dependent behavior of the prepreg—such as resin fluidity and wrinkle characteristics—was evaluated from room temperature to 80 °C. Material characterization included tensile, bias extension, bending, friction, and density tests. Forming simulations using AniForm Suite 3.0 incorporated fitted material parameters for predictive analysis. Experimental validation confirmed that the mDDF process significantly improved fiber alignment and eliminated wrinkle defects, especially in 16 previously identified critical zones. The final parts exhibited superior surface quality and dimensional accuracy compared to conventional PCM, highlighting the potential of mDDF for precision manufacturing of complex thermoset composite structures.