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Wave Propagation and Dispersion in Sandwich Plates Subjected to Blast Loads

This paper investigates through-thickness propagation of compression waves induced by blast loads on the facesheet of a sandwich plate and how it is affected by the underlying material properties. A conventional sandwich design, which utilizes a closed cell foam core, is considered together with a modified design, which includes a thin polyurea interlayer between the outer (loaded side) facesheet and the foam core. The latter design is known to perform exceptionally well under impulse loads due to the significant stiffening of polyurea under high strain rates. This property reduces the amplitude and velocity of compression waves traveling into the foam core and prevents its sudden, excessive crushing. The problem was modeled with the explicit LS-Dyna finite element code. The results compare the short term behavior of the conventional and modified sandwich designs using a one-dimensional model for through-thickness wave propagation, and illustrate the long term effects on a multi-span sandwich plate subjected to a blast load. It is shown that the polyurea interlayer retards blast-induced compression waves propagating into the foam core in the initial blast period, and this reduces the core compression and leads to an improved long term behavior.