Super-austenitic stainless steels (SASS), characterized by their high Cr–Ni–Mo alloying content, have attracted increasing attention for structural applications that demand exceptional corrosion resistance, high ductility, and robust energy-absorption capacity. When these advanced alloys are incorporated into sandwich panel configurations—typically consisting of two face sheets and a lightweight core—they offer a promising solution for protective structures exposed to extreme dynamic loading environments. Such composite systems are being explored for naval vessels, offshore platforms, subsea equipment, and critical infrastructure where both mechanical resilience and environmental durability are essential.

In this case, both top and bottom steel plates are modeled as 3D parts, and the core is modeled as a shell part. The Johnson-Cook hardening and damage model is selected to demonstrate the high-rate deformation of the sandwich panel. The UNDEX and CONWEP method is used simultaneously to consider the air blast and underwater shock at the same time.

Air blast and underwater explosion (UNDEX) events impose highly transient, large-amplitude pressures that can drive complex deformation mechanisms in metallic sandwich structures. Unlike quasi-static or low-rate loading, these impulsive events activate strain-rate-dependent material behavior, fluid–structure interaction effects, and dynamic core–face sheet interactions. For sandwich panels fabricated with super-austenitic stainless steels, the deformation response is governed not only by the intrinsic high-rate plasticity of the alloy but also by the geometry and architecture of the core—commonly honeycomb, corrugated, or foam designs.

Under air blast loading, the deformation is dominated by pressure wavefront interaction with the front face sheet, core crushing or shear failure, and global plate bending. The relatively short duration of air-blast impulses often results in localized plastic deformation, face-sheet wrinkling, and, in more severe cases, core densification or debonding. The high toughness of SASS alloys contributes to delaying fracture initiation, enabling the structure to dissipate energy through extensive ductile deformation.

In contrast, underwater explosion loading produces a markedly different response due to the higher density of water, longer impulse duration, and potential for bubble-pulse loading. The pressure transmitted through the water medium can be significantly larger, promoting global panel deformation, fluid–structure interaction effects, and more pronounced through-thickness core damage. The ability of super-austenitic stainless steels to maintain strength and ductility at high strain rates plays a crucial role in mitigating catastrophic failure modes such as face-sheet tearing or core shear buckling.

Overall, the deformation behavior of SASS sandwich panels under blast and UNDEX conditions embodies a complex interplay among material strain-rate sensitivity, panel architecture, and loading characteristics. Understanding these mechanisms is essential for the design and optimization of next-generation blast-resistant and corrosion-resistant structural systems.