Keywords: sandwich plate, viscoelastic core, blast load, finite element analysis, large deflection, nonlinear.

The behaviours of sandwich and laminated composites under blast loading have been widely studied [1,2,3]. In the current paper, the blast induced vibrations of sandwich plates with stepwise graded core were studied, experimentally and numerically. For this purpose, a sandwich composite plate was manufactured. It has four layers of bidirectional glass epoxy face sheets and three types of viscoelastic layers which were AirexR structural foam, aramid honeycomb and LexanR polycarbonate sheet. In the scope of experimental studies, static, modal and blast load tests were performed. All edges of the sandwich composite plate were clamped to a fixed steel frame. Sand was used to apply a concentrated load on sandwich plate. Otherwise, for blast load tests, air blast was obtained by compressing the air in a tube and then suddenly expanding the compressed air using a membrane. Pressure and strain were measured by using pressure sensors and strain gauges. Pressure sensors were placed in front of the plate surface. On the other hand, strain gauges were placed on the back side of the plate. A pressure distribution was gained from the experimental study. According to this distribution, a pressure function was formed and it was used in modelling of the blast loaded sandwich plate. In the numerical side of the study, a sandwich plate was modelled using shell elements using ANSYS. At the end of the generation of the finite element model, static, modal and transient analyses were performed. Results from the experimental study and numerical analysis were compared according to centre point strain values. Only the first natural frequency of the sandwich plate was measured because of the plate's loading conditions. Performing these analyses, it was clearly shown that a laminated sandwich plate can be modelled with its material properties and an approximated pressure function which was formed using the experimental study. After validation of the finite element analyses of the laminated sandwich plate, core materials sequencing were reordered. With same approximated pressure function, transient analyses were performed for a new configuration. Strain and displacement results of the centre point were compared for two configurations and the results were concluded.

1

E. Wang, N. Gardner, A. Shukla, "The blast resistance of sandwich composites with stepwise graded cores", International Journal of Solids and Structures, 46, 3492-3502, 2009. doi:10.1016/j.ijsolstr.2009.06.004

2

H.S. Türkmen, Z. Mecitoglu, "Dynamic response of a stiffened laminated composite plate subjected to blast load", Journal of Sound and Vibration, 221(3), 371-389, 1999. doi:10.1006/jsvi.1998.1976

3

Z. Kazanci, Z. Mecitoglu, "Nonlinear dynamic behaviour of simply supported laminated composite plates subjected to blast load", Journal of Sound and Vibration, 317, 883-897, 2008. doi:10.1016/j.jsv.2008.03.033

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