# Experimental and Numerical Evaluation of Calcium-Silicate-Based Mineral Foam for Blast Mitigation
## 1 Introduction
The research indicated that sandwich panels with CFRP face sheets exhibited superior performance, probably due to the lightweight, high stiffness-to-weight and strength-to-weight ratios of CFRP face sheets. Furthermore, it was demonstrated that panels with a positive core density gradient (decreasing core density along the blast direction) had better blast resistance than those with uniform core density. In contrast, a negative core density gradient resulted in the worst blast resistance. Although numerous studies rely on the LCS model [17; 21; 24; 27; 30; 31; 35; 41], it is worth noting that the foam thickness can no longer be neglected compared to the standoff distance when dealing with close-in explosions [42]. Maintaining a constant distance between the detonation point and the protected structure results in a systematically increased blast-induced energy (referred to as energy input hereafter) transfer to the system upon adding SC. [PERSON] et al. [36; 37] experimentally and numerically studied the influence of the mineral foam thickness in sacrificial cladding while maintaining a constant standoff distance between a fixed aluminum plate (representing the protected structure) and the explosive charge. The mineral foam is sandwiched between the protected structure and a front skin made of aluminum. Blast loading is induced by detonating 20 g of C4 explosive positioned 250 mm from the protected structure's center. Two configurations of mineral foam with different thicknesses, 60 mm and 120 mm, were examined. Their findings suggest that compartmentalized configurations with appropriate spacing between foam volumes can enhance energy dissipation, thereby improving blast mitigation of the SC. Despite the increased energy input associated with the thickness of the mineral foam layer, the results demonstrate a reduction of at least 50% of the maximum deflection at the plate's center when the foam is added. However, [PERSON] et al. [42] reported results regarding the protective performance of SC that may not be expected. They investigated increased blast-induced energy on the cladding structure system through experimental tests and numerical simulations. Initial blast tests were performed on steel plates with and without SC, using TNT equivalent charge masses of 400 and 1400 g. The concept of positive and negative protection effects of sacrificial cladding was introduced. A positive protective effect means less energy is transmitted to the steel plate with cladding than to the plate without cladding. Otherwise, it is a negative protection effect. The results indicated a positive effect with the 400 g charge mass but a negative effect with the 1400 g charge mass. Subsequent numerical simulations validated by experimental data were conducted to explore blast mitigation performance. The simulations revealed that using SC significantly increases the energy transferred to the cladding structure system during close-in detonation. A negative protection effect is observed when the transferred energy exceeds the SC's energy absorption capacity. Factors such as front skin thickness, core density, and standoff distance were investigated, indicating that a close-in detonation with a reduced standoff distance and the same explosive charge mass could lead to a negative protection effect. To obtain a positive protection effect with the SC, enhancing core density and increasing front skin thickness are viable measures that simultaneously reduce energy input and improve energy absorption capacity. In a numerical study, [PERSON] et al. [19] compared two SCs with different core configurations, namely conical-array and single-volume cores, subjected to the same blast loading. The conical-array core is more effective than the single-volume core in distributing the blast load over time and keeping the peak force low. The current investigation aims to assess the protective effectiveness of a calcium-silicate-based mineral foam SC through experimental and numerical means.