## 1 Introduction  
Sandwich structures are widely used in blast dissipation applications due to their excellent physical and mechanical properties [1; 2; 3; 4; 5]. They are adopted as sacrificial cladding structures, which are designed to attach at the facade of structures in order to absorb energy through the progressive plastic deformation of the front-facing plate and the inner core layer and thus the transfer of the peak force to the non-sacrificial structure can be minimized [6; 7; 8]. Sandwich panels are three-layer composite structures consist of two outer plates made of metals or composite materials and a crushable core layer in between. The plate faces blast wave distributes blast pressure more evenly across the core layer that deforms progressively and absorbs most of the energy, so the core has a significant influence on the blast behavior of sandwich structures. The core layer could have several topologies,such as corrugated [5; 9], honeycomb [5; 10], trusses [11; 12], hybrid cores [13], and functionally graded cores (FGC) [14]. Under those topologies, several configurations could be used to shape the core of the sandwich panels to provide adequate stiffness and strength to support structural loads. For instance, the corrugated topology can have trapezoidal-folded, diamond-folded, Y-frame-folded, and triangular-folded core configurations [7], a zig-zag trapezoidal corrugated core [15], and woven corrugated cores [16]. A lot of research work was dedicated examining the impact of assorted core topologies on the blast performance of sandwich structures. [PERSON] et al. [17] examined the response of metallic triangular honeycomb sandwich panels and equivalent solid plates under localized blast loads. They noticed that the sandwich panels were superior to a solid plate when subjected to blast load. Moreover, they proposed a sandwich panel with a double-corrugated soft core, which surpasses that with a triangular honeycomb core. As an attempt to investigate the effect of the core topology; [PERSON] et al. [18] examined the behavior of metallic sandwich panels with diverse core topologies; square honeycomb, triangular honeycomb, multi-layer pyramidal truss, triangular corrugation, and diamond corrugation core topologies with a core relative density of approximately 5%. They found that truss and corrugated cores had a significantly lower strength with a long plateau, like metal foams, while honeycomb cores revealed a high initial strength with a softening post peak response. Moreover, they found that crushable cores reduce the transmitted impulse by 25% compared with high rigid cores. [PERSON] et al. [19] investigated three core topologies (square honeycomb, I-core, and corrugated) for a sandwich structure subjected to a blast load. They concluded that the best overall performance was attained by the soft cores (corrugated). [PERSON] et al. [7] numerically investigated the performance of six different core topologies for metallic sandwich panels under blast loading. They concluded that folded shapes attenuate more energy than honeycomb shapes. [PERSON] et al. [20] conducted a comprehensive numerical analysis on the response of metallic sandwich structures with different core configurations under the impact of blast load. They also introduced woven shapes as a novel core topology for the metallic sandwich structures. The study revealed that woven shapes achieved superior energy dissipation capability compared to the folded and honeycomb shapes; however, this novel pattern required more core relative density compared to corrugated cores. Various research topics were focused on far-field blast; however, close-in explosions often cause a serious damage for various structural components when the explosive charge detonates at a very short distance from the structure. The American Society of Civil Engineers (ASCE) classifies explosions detonates with a scaled distance (Z) of less than 1.2 m/kg\({}^{1/3}\) as a close-in explosion [21].