Dynamic Response of PVC Foam/Polyurea Sandwich Structures with Different Core Layers Under Air Blast Loading

This paper presents a combined experimental and numerical method to investigate the dynamic response and energy absorption mechanisms of polyvinyl chloride (PVC) foam/polyurea sandwich structures under air blast loading. A total of five distinct core configurations were designed under the condition of identical overall areal density, covering a pure PVC foam core (denoted as B-1), three hybrid cores with a PVC-to-polyurea mass ratio of 5:1, 2:1 and 1:1 (denoted as B-2, B-3 and B-4, respectively), and a pure polyurea core (denoted as B-5). All blast experiments were conducted at a scaled distance of Z = 0.2554 m/kg1/3. Representative deformation features and failure modes of the tested sandwich specimens were systematically identified and documented. Numerical simulations were performed to analyze the effects of core mass ratios and density gradients on the energy absorption characteristics and plastic deformation. The numerical-experimental errors were all below 8.5%. The structural response was divided into three stages: front face sheet acceleration deformation, core compression and core densification (for foam-cored configurations). Results revealed that the front face sheet primarily underwent local indentation, the core layer exhibited local compression, shear and tensile failure, the back face sheet suffered significant global deformation, and obvious interfacial debonding occurred at the face sheet-core interface. For the foam-containing configurations, the PVC foam core was found to be the dominant energy-absorbing component. For the five designed configurations B-1, B-2, B-3, B-4 and B-5, the measured residual back-face deflections are 20.4 mm, 18.0 mm, 18.1 mm, 23.9 mm and 26.3 mm, respectively, while the corresponding total energy absorption values are 1035.05 J, 1176.50 J, 965.08 J, 742.40 J and 631.20 J. Among the five experimentally tested specimens, B-2 exhibits the minimum back face sheet deflection and the maximum energy absorption simultaneously, confirming its best blast resistance performance within the current test range. Moreover, the numerical results show that the graded PVC foam core design further enhances the blast resistance of the sandwich structure. Compared with the simulated B-2 reference result, the positive gradient foam core configuration (GF-1) reduces back face sheet deflection by 30.37%.