Behavior of Sandwich Plates Reinforced with Polyurethane/Polyurea Interlayers under Blast Loads

Abstract

In this study, the behavior of conventional and modified sandwich plate designs subjected to blast loads is examined with the finite element method. The conventional sandwich design consists of thin outer (loaded side) and inner facesheets made of fibrous laminates, separated by a layer of structural foam core. In the modified designs, a thin ductile interlayer is inserted between the outer facesheet and the foam core. Two materials are selected for the interlayers; one is rate-independent, hyperelastic (polyurethane, PUR), and the other is rate and pressure-dependent, elastic—plastic (polyurea). A comparison is made between the two enhanced designs and the conventional design during an extended time period of 5.0 ms under an exponential pressure impulse lasting for 0.05 ms, and has a peak pressure of 100 MPa. Results show that utilizing PUR or polyurea to separate the outer facesheet and the foam core leads to a much reduced core compression, facesheet vibration, and overall deflection compared to the conventional design. Similar reductions are found in the kinetic energy and the stored and dissipated strain energy. This is attributed to the ability of the interlayers to store energy and shield the inner foam by exhibiting great stiffness under pressure. Although strain rates as high as 104 s—1 are produced by the blast pressure impulse in the sandwich plates, the strains in both the PUR and the polyurea interlayers are relatively small. This leads to generally similar responses for the two interlayer types, with the initially stiffer PUR providing a slightly better protection for the foam core.