## 5 Description of the Numerical Model  
In this section, a detailed description of the underlying numerical model is provided. Figure 13 illustrates the support configuration and some of the constant geometry parameters. This setting is valid for all the topologies and configurations investigated here. The set of constant parameters also includes a constant cover thickness of 1.0 mm, a constant core height of 20.0 mm, and a constant relative core density of almost 3.3 percent. The outer dimensions of the sandwich specimens are 400 \(\times\) 400 mm and do not vary. In all computational studies, both the total mass and the ratio of the core to the two faces (\(\approx\)1:3) are kept constant. The core mass is thus approx. 25% of the total weight. In consequence, these specifications imply, for a monolithic reference panel of the same weight, a panel thickness of 2.66 mm. All components have the material properties of the aluminum alloy EN AW-7108 T6. The aluminum alloy EN AW-7108 T6 serves as an exemplary representative for descriptions of ductile material behavior. The main alloying element, zinc, helps it to achieve high strengths and allows it to be used in aircraft and automotive construction, aerospace applications, and high-quality sports equipment. The alloy has high corrosion resistance, favorable machining properties, and very good weldability. It is, therefore, a suitable material for the real production of the different core variants for sandwich panels. The elastic material parameters and the density of the aluminum alloy are shown in Table 5.  
The commercial finite element code ABAQUS/Explicit employs an extensive material model that includes rate-dependent elasto-plastic material behavior and various types of failure mechanisms. The calculations for damage evolution and progressive softening after damage initiation are based on the concept of effective stresses. The behavior of the damaged material is represented by the behavior of the undamaged material in conjunction with a total scalar damage parameter D. This parameter takes into account the individual stresses specified for the three ductile failure mechanisms:  
* Failure due to the growth, coalescence, and regeneration of micro-voids. * Shear/slip failure due to local shear bands. * Necking instabilities (local necking). By means of the damage parameter, both reductions in the yield stress and losses of stiffness can be modeled. All necessary material data, including, in particular, those for characterizing the hardening and strain rate behavior as well as the failure phenomena, are taken from the experimentally verified ABAQUS reference example \"Progressive failure analysis of thin-wall aluminum extrusion under quasi-static and dynamic loads\". A blast loading above the support structure serves as the load source. Measured from each upper edge, the point of ignition is located at a distance of 100 mm centrally above the alternating test structures (i.e., the different core topologies). The TNT equivalent of the explosive charge is 40 g. The support is free from any kind of constraints in the sense that the sandwich structure lies loosely and directly on the supporting structure and is free in its translational and rotational movements throughout the simulation. A restriction of movement exists only due to the contact conditions. The ABAQUS/Explicit general  
Figure 13: Configuration of the numerical model, including the support structure and the load source (air blast). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Young’s Modulus** & **Poisson’s Ratio** & **Density** \\ \hline
70.000 N/mm\({}^{2}\) & 0.33 & 2.700 kg/m\({}^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The elastic material parameters and the density of the aluminum alloy EN AW-7108 T6. contact conditions prevail throughout the model (hard contact in the normal direction and \"aluminum-steel\" or \"aluminum-friction\" contact in the tangential direction). However, all components of the sandwich structure can come into mutual contact.