Laser-based fabrication and characterization of steel–polyamide 6–steel sandwich composites

Metal–Polymer–Metal (MPM) sandwich composites are gaining increasing attention for lightweight structural applications due to their customizable mechanical properties and multifunctionality. In this study, AISI 1018–polyamide 6 (PA6)–AISI 1018 sandwich composites are fabricated using a laser-based fabrication technique to achieve controlled heat input and well-adhered steel–polymer interfaces. Surface texturing of the steel sheets is introduced to further enhance interfacial bonding. Mechanical characterization of bond strength is carried out through lap-shear testing, while interfacial morphology and chemical interactions are examined using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Results reveal that laser-based fabrication provides adequate bond strength even in untextured specimens, whereas surface texturing markedly improves both interfacial strength and consistency. Interfacial morphology and chemical analyses confirm that polymer melting, wetting, and adhesion, combined with mechanical interlocking and chemical interactions, contribute to the overall bond strength at the interface. These findings demonstrate that laser-based joining combined with optimized surface texturing offers a promising approach for fabricating high-performance MPM sandwich composites for engineering applications.