.Introduction: These types of panels are commonly used to create lightweight mobile shelters as shown in Figure 1. For this analysis work, a section of the panel was idealized into a plate and brick FEA model. The foam material (Trymer 400L) was modeled using brick elements and the aluminum tubes and skin were modeled using brick elements. An example of the model is given in Figure 2.
The panel was subjected to a secondary ballistic impact penetration of a grenade fragment falling at terminal velocity. The fragment is described in MIL-DTL-46593. LS-DYNA results showed that the sandwich panel’s foam core absorbs significant amounts of ballistic energy. To model the foam properties, element erosion was enabled along with different tensile and compressive failure limits. This allowed the foam to compress without failure yet capture the brittle failure mode that is prevalent in polyisocyanurate foams.
The final results allowed the client to meet their design requirements without the need of experimental testing. Although this was unusual (i.e., no experimental testing) the robustness of the analysis results coupled with prior experience provided sufficient margin to proceed with manufacturing.
Keywords: LS-DYNA, projectile, blast, penetration, composite sandwich structure, aluminum foam composite, nonlinear analysis, transient, dynamic, element erosion, damage prediction, contact analysis, MOTS shelter roof, trade study report, secondary mortar, rocket propelled grenade fragmentation, Trymer 400l foam, 6061-T6 aluminum, Femap, LSTC, 20mm FSP round, MIL-DTL-46593, Finite Element Analysis, Femap, Foam Material Modeling,