Figure 1. windshield assembled in cockpit portion of the airframe

Figure 1. windshield assembled in cockpit portion of the airframe

DRD has performed finite element analysis to simulate a bird strike on an aircraft windshield for the NORDAM Group’s Transparency Division. The NORDAM Group is recognized worldwide as an industry leader in the manufacture, repair and overhaul of aircraft bonded-honeycomb components, fan/thrust reversers, engine components, interiors and aircraft transparencies.

The NORDAM Group’s Transparency Division provides commercial and regional airlines a single-source supplier for development, manufacture, repair and overhaul of aerospace transparency components.

DRD constructed the windshield finite element model starting from geometry in UNIGRAPHICS. We used layered shell finite elements, which account for offset between the nodes and the shell midsurface.

Figure 2. mode shape of first natural frequency

Figure 2. mode shape of first natural frequency

One of the first steps in the analysis was to perform normal modes analysis of the windshield. The mode shape associated with the windshield first natural frequency is shown in Figure 2.

The bird constitutive model was a critical aspect of the bird strike simulation. The animations in Figures 3 and 4 demonstrate preliminary simple cube and ellipsoid versions of the bird constitutive model, which exhibits fluid-like behavior.

figure 3. simple cube impact with bird equation of state

figure 3. simple cube impact with bird equation of state

figure 4. ellipsoid with bird equation of state CONSTITUTIVE model 

figure 4. ellipsoid with bird equation of state CONSTITUTIVE model 

After verifying satisfactory behavior for the windshield and the bird models separately, we combined the two models to perform the bird strike simulation.

This animation shows the bird impacting the windshield. The bird disintegrates during impact.

figure 5. bird impact on windshield

figure 5. bird impact on windshield

figure 6. windshield deformation

figure 6. windshield deformation

LS-DYNA 3D layered shell element enabled DRD to examine stresses at each windshield ply. The near left graphic provides stresses in one of the windshield’s inner plys.

ANSYS/LS-DYNA software made it easy for DRD to perform the bird strike analysis with and without windshield static internal pressure. An implicit-explicit finite element solution was required to account for the static internal pressure.

The far right graphic shows stress contours due to static internal pressure before bird impact.

figure 7. stress contours in windshield

figure 7. stress contours in windshield

figure 8. stress in windshield due to static internal pressure

figure 8. stress in windshield due to static internal pressure