PSI - Issue 13

Muhammad Zakir Sheikh et al. / Procedia Structural Integrity 13 (2018) 2120–2125 Muhammad Zakir Sheikh et al. / Structural Integrity Procedia 00 (2018) 000–000

2124

5

In the second phase of the paper, the reduce the wave speed travel in the glass the PU interlayers of thicknesses (0.5 mm, 1.0 mm, 2mm and 3 mm) were modeled to study the influence of interlayer thickness. The numerical simulations are completed for all these laminated plates against spherical projectile impact at the impacting velocity of 440 m/s to compare the delay in arrival time of stress wave. The simulations were also completed for a double layer of PU such that dividing the glass plate into three equal parts. The gauge points in impact direction were defined in target plates to record the arrival of stress time. The results for delay in wave arrival time and drop in stress values recorded at gauge # 13 in all the simulations compared to monolithic glass are shown in figure 4. Through simulations, the wave propagation in the laminated glass was analyzed and it was observed that at stress wave reaches the interlayer due to the low density of PU interlayer the stress wave is attenuated. At PU interlayer interface some part of the wave is reflected back towards the glass and some part is transmitted to the right half of the glass. So, it was observed that when a wave reflects back it's in a tensile mode which causes the failure of the left half of the glass. In case of double PU interlayer of thickness 3 mm the only the first portion of the glass was damaged and other two parts of the glass remain intact because a significant amount of stress wave attenuated by two bonding layers.

Figure 4 The FE model of glass laminate with interlayer PU at (left), and delay in wave arrival time and stress values at gauge # 13 at (right)

Additionally, more simulations were conducted by adding the PU interlayer in parallel and normal to impact loading direction (plus shaped glass laminate) as shown in figure 5. The idea for this is to divide to the stress wave in two parts and change the direction of the incoming wave to keep intact the major portion of the glass laminate. The simulations for this configuration is completed for same loading conditions as mentioned above and simulation result for this configuration is also shown in figure 5. The PU interlayer in impact direction attenuates the stress wave due to its low impedance traveling in the direction of impact. However, at the same time wave continues to travel in upper and lower portion of glass which in turns loses it intensity as one continuous wavefront observed in other cases.

Figure 5 The Plus-shaped interlayer FE model and stress wave propagation contour plot at different times.