## 2 Materials and Experimental Work
### Finite Element Modelling  
To comprehend the deformation behaviour of organosheet RG and FML under deep-drawing conditions, finite element analysis via Abaqus/Explicit was introduced. The plastic response of steel-grade TS275 was modelled by assuming isotropic hardening, but in this case, the damage criterion to simulate the fracture behaviour was not given. The plastic properties of TS275 were extrapolated according to Swift law. Figure 6 shows the relationship between flow stress and plastic strain for TS275 at RT and 235 \({}^{\circ}\)C, as well as the other properties, namely, the density (\(\rho\)), E-modulus (\(E\)), Poisson' ratio (\(\
u\)), and yield strength (\(YS\)). The corresponding data were obtained from the experimental stress-strain curves in Figure 1b. Moreover, the influence of the strain rate on the mechanical properties of the steel sheet could be ignored. The difference between the tensile strengths from 0.04 s\({}^{-1}\) to 0.004 s\({}^{-1}\) was minor for this kind of mild steel (TS275), a result which was published in the previous study [33]. The test speed for the deep-drawing (0.5 mm/s) and tensile tests (0.64 mm/s) were at the approximate magnitude, same for the characterization of organosheet and PA6. In this study, the simulation of deep-drawn FML was performed at 200 \({}^{\circ}\)C, where the difference in mechanical properties between 200 \({}^{\circ}\)C and 235 \({}^{\circ}\)C was neglected. More results on the mechanical characterization of this organosheet and PA6 regarding the temperature were published in [34], in which the same organosheet was considered. Thus, RG was modelled as an anisotropic elastic material with nine engineering parameters, \(E_{1}\), \(E_{2}\), and \(E_{3}\) (E-moduli in their respective directions); \(v_{12}\), \(v_{23}\), and \(v_{13}\) (Poisson ratios in their respective directions); and \(G_{12}\), \(G_{23}\), and \(G_{13}\)(Shear-moduli in their respective directions), whose values at RT and 200 \({}^{\circ}\)C were obtained from [33; 34] (see Table 5). The density of RG was 1.8 g/cm\({}^{3}\). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**T (\({}^{\circ}\)C)** & **\(E_{1}\) (MPa)** & **\(E_{2}\) (MPa)** & **\(E_{3}\) (MPa)** & **\(v_{12}\)** & **\(v_{23}\)** & **\(v_{13}\)** & **\(G_{12}\)** & **\(G_{13}\)** & **\(G_{23}\)** \\ \hline RT & 25,870 & 25,850 & 6448 & 0.16 & 0.44 & 0.44 & 9186 & 1331 & 1331 \\
200 & 16,600 & 16,600 & 730 & 0.1 & 0.34 & 0.34 & 250 & 200 & 200 \\ \hline \hline \end{tabular}  
\end{table} 
Table 4: Test plan for deep drawing. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**T (\({}^{\circ}\)C)** & **\(E_{1}\) (MPa)** & **\(E_{2}\) (MPa)** & **\(E_{3}\) (MPa)** & **\(v_{12}\)** & **\(v_{23}\)** & **\(v_{13}\)** & **\(G_{12}\)** & **\(G_{13}\)** & **\(G_{23}\)** \\ \hline \hline RT & 25,870 & 25,850 & 6448 & 0.16 & 0.44 & 0.44 & 9186 & 1331 & 1331 \\
200 & 16,600 & 16,600 & 730 & 0.1 & 0.34 & 0.34 & 2 Furthermore, the interfacial contact behaviour between the layers of FML was modelled using three separate approaches. First, it was modelled using cohesive elements (COH3D8) based on nominal stresses and energies, which were defined in terms of traction separation, i.e., mixed-mode delamination (see Figure 7). The maximum normal stress damage initiation criterion (Maxs) and the Benzeggagh-Kenane (BK) damage evolution criterion were used, respectively. For the damage initiation criterion in this figure, \(t_{n},\ t_{s},\ \text{and}\ t_{t}\) represent the normal and the two shear tractions; and \(t_{n}^{0},\ t_{s}^{0},\ t_{t}^{0}\), and \(t_{t}^{0}\) represent the peak values of the nominal stress when the deformation was either purely normal to the interface or purely in the first or the second shear direction, respectively [35].