Tailoring electrical anisotropy in CFRP laminates via additively manufactured conductive interlayers

For carbon fibre-reinforced polymer (CFRP) laminates used in applications requiring charge dissipation and electromagnetic interference shielding, limited through-thickness electrical conductivity remains a significant drawback. In this work, an innovative approach based on fused deposition modelling (FDM) is proposed to introduce conductive thermoplastic interlayers directly onto carbon fabrics prior to resin infusion. Copolyester-based hot-melt adhesive filaments modified with multi-walled carbon nanotubes (MWCNT) and carbon black were developed and processed by FDM. The hybrid MWCNT/carbon black formulation exhibited improved filler dispersion and enhanced thermal stability, resulting in electrical conductivity of up to 20.81 S/m in printed paths. When integrated into CFRP laminates, the printed interlayers increased the through-thickness electrical conductivity from 3.1 S/m for the reference laminate to 16.6 S/m and 27.1 S/m for the MWCNT- and hybrid-filled systems, respectively, while the in-plane conductivity increased from approximately 770 S/m to 2400 S/m. Mechanical and thermo-mechanical analyses confirmed that the printed interlayers did not adversely affect laminate integrity.