# A Sensitivity Analysis of the Damage Behavior of a Leading-Edge Subject to Bird Strike
## 2 Experimental Test Article and Numerical Implementation
The latter ones (fiberglass, Kevlar and CFRP) or can be precured and then bonded to honeycomb core with adhesive or can be cured with a honeycomb core, and thus, the resin can replace the adhesive layer. The common methods of bonding panels are with the help of autoclaves, vacuum bagging and presses. Autoclaves and vacuum bagging are generally used for curved parts and presses for flat panels. Generally, the pressure helps to have a perfect adhesion; however, the amount of pressure to be applied depends on the compressive strength of the core. Table 2 reports the main material properties; the other ones were set according to standard numerical procedures (\(\approx\)0). The left and right webs are made of 2 mm-thick AL20204-T3. The lower and upper L-beam used to connect the skin to the interface frame are 2 mm-thick AL2020-T3. The test rig is made of steel, and it is 1200 mm high and 650 mm wide. The height of the interface frame is 405 mm. The beams of the mainframe have a \(60\times 40\) mm\({}^{2}\) rectangular cross-section, while the ones on the interface frame are \(60\times 30\) mm\({}^{2}\) C-sections. Both of them are 5 mm thick. Isotropic elastic-plastic material model was associated with the aluminum skin layers, assuming bilinear yield behavior and isotropic hardening that uses the [PERSON] yield criterion with a plasticity algorithm with strain rate effects. Cowper-Symonds law was used as the elastic-plastic formulation to consider strain rate dependency at medium rate regime and in particular, the related parameters \(D\) and \(p\) were, respectively, set to \(1.28\ \times 10^{5}\) s\({}^{-1}\) and 4.0 [20]. The impact occurs in the center of the leading edge (at the apex), with an impact trajectory normal to the leading edge (0\({}^{\circ}\) impact angle). The impact velocity is equal to 129 m/s, and the bird mass is 3.68 kg, resulting in a total starting kinetic energy of about 30.6 kJ. The projectile, i.e., the bird, was discretized as a 268 mm long cylinder with a diameter equal to 134 mm. The duration of the analyses was set to 30 ms. No friction was considered. The choice to use the small component of the leading edge is useful above all to validate the numerical models, whereas a full-scale test must be considered for the certification. The bay offers different constraint conditions with respect to the entire leading-edge component: in fact, the behavior of the ribs, which are arranged \begin{table}
\begin{tabular}{c c c c} \hline
**Description** & **Symbol** & **Unit** & **Value** \\ \hline Young’s modulus & E & [GPa] & 72 \\ Yield stress & \(\sigma_{y}\) & [MPa] & 280 \\ Ultimate strength & \(\sigma_{u}\) & [MPa] & 385 \\ Failure strain & \(\epsilon_{\text{ult}}\) & [mm/mm] & 0.18 \\ Density & \(\rho\) & [g/cm\({}^{3}\)] & 2.7 \\ \hline \end{tabular}
\end{table} 
Table 1: Aluminum alloy mechanical properties [20]. \begin{table}
\begin{tabular}{c c c c} \hline
**Description** & **Symbol** & **Unit** & **Value** \\ \hline Elastic modulus (out-of-plane) & E\({}_{\text{C}}\) & [MPa] & 861 \\ Shear modulus—ribbon direction & G\({}_{\text{L}}\) & [MPa] & 200 \\ Shear modulus—transverse direction & G\({}_{\text{W}}\) & [MPa] & 90 \\ density & \(\rho\) & [g/cm\({}^{3}\)] & 0.046 \\ \hline \end{tabular}
\end{table} 
Table 2: Honeycomb mechanical properties [20]. laterally, is very different as they are free to flex and follow the deformation of the panel, opposed to the full-scale leading edge where they are constrained by contiguous samples.