Recent Trends in Manufacturing of Thermoplastic Sandwich Structures: A Review

Lightweight thermoplastic sandwich structures have a potential in terms of high specific strength, recyclability, repairability, and reduced manufacturing costs and cycle times, thereby widening their applicability in the aviation industry. However, joining thermoplastic skins to the core is considered a critical process in determining the structural integrity of fully recyclable sandwich systems. Despite rapid technological progress, a comprehensive assessment of manufacturing routes capable of achieving reliable skin/core fusion bonding remains lacking. Therefore, this review critically examines manufacturing techniques for thermoplastic-based sandwich panels, with particular emphasis on advanced processes that achieve effective skin/core fusion bonding. Within conventional manufacturing routes, compression moulding and double-belt lamination have the potential for high-volume production and process automation. Skin/core fusion bonding via in situ core formation enhances manufacturing flexibility, particularly for achieving complex designs. Emerging approaches, including additive manufacturing, automated fibre placement, and welding-based methods, are identified as promising fusion-bonding strategies. This offers enhanced manufacturing simplicity and efficiency by minimising interlinked processing stages and eliminating the need for intricate mould patterns. Future advancements are expected to focus on highly integrated and scalable manufacturing routes capable of simultaneously achieving skin consolidation, in situ core formation, and skin/core fusion bonding within a single process. In particular, continuous welding-assisted manufacturing and additive manufacturing-based approaches are highlighted as promising pathways for improving structural integration, recyclability, and production efficiency in next-generation thermoplastic sandwich structures. Overall, this review provides a structured foundation to guide future research directions and support the development of more efficient, scalable, and structurally reliable thermoplastic sandwich manufacturing technologies.