“PMI foam used in honeycomb structure in multifunctional application”

Polymethacrylimide (PMI) foam's superior long-term dimensional stability, high stiffness, and low density provide it with a superior core material for elaborate sandwich structures. Its exceptional mechanical and functional qualities such as energy absorption, creep resistance, and superior thermal and dielectric stability are attributed to its closed-cell morphology and cross-linked molecular architecture, which outperform traditional cores like polyurethane, polyvinyl chloride foams, and balsa wood, which frequently have to give up mechanical strength, sensitivity to moisture, or resistance to heat deterioration. By facilitating production into intricate geometries like honeycomb and hierarchical hybrid structures, additive manufacturing has further increased the adaptability of PMI foams and improved interfacial bonding, damage tolerance, and multifunctional integration. In addition to providing radar absorption qualities that are essential for stealth and defence applications, these designed structures exhibit notable gains in tensile and compressive strength, increased temperature resistance, and efficient electromagnetic interference shielding. Beyond their mechanical capabilities, PMI foam-based composites are becoming more sought for their versatility, fulfilling both protective and structural functions in difficult settings. New advances in PMI foam production techniques, structure–property correlations, and multipurpose uses in sandwich composites are compiled in this review. In order to fully realize the potential of PMI foams in next-generation lightweight systems, it also critically assesses processing difficulties, large-scale integration constraints, and durability issues. Finally, it highlights future directions in sustainable synthesis, hybrid material design, and advanced manufacturing routes. This review covers PMI foam’s fabrication, structure–property relationships, multifunctional applications, and comparative advantages, while addressing processing challenges and future directions in sustainable hybrid composite design.