Experimental investigation of energy-absorption characteristics of components of sandwich structures

Two series of experiments are performed to investigate the dynamic response of various essential components of a class of sandwich structures, under high-rate inertial loads. One consists of dynamic inertia tests and the other involves dynamic impact tests. A split Hopkinson bar apparatus is modified and used for these experiments.First, the energy-absorbing characteristics of the plate material in a sandwich structure are investigated using novel dynamic inertia tests, paralleled by detailed finite-element simulations. The loading conditions in this case are similar to those in high-rate pressure loading situations, and hence more closely simulate potential blast effects on structures. Plates made of DH-36 naval structural steel are used in the dynamic inertia tests. The plates subjected to inertia loading show membrane deformation behavior, but as the deflection or thickness increases, the bending deformation near the clamped joint becomes significant.Second, the dynamic behavior of the core material in a sandwich structure is studied through dynamic impact (compression) tests, using high-speed photography. In addition, both the quasi-static and dynamic response of the material is quantified using hydraulic testing machines and the Hopkinson-bar techniques. Aluminum foam as a core material is used in these experiments. Aluminum foam is a lightweight material with excellent plastic energy absorbing characteristics. The experimental results show a localized deformation in the metal foam specimens, at suitably high impact velocities. The simulation results correlate well with the test results in the overall behavior of the metal foam specimens.With these two experimental methods, the dynamic behavior of sandwich structures under high-rate inertial loading conditions can be examined minimizing the need for direct pressure-induced impulse experiments. Each series of experiments is relatively simple and can be performed separately to study the complex behavior of sandwich panels in simple and well-controlled tests. The validity of separate performance test is shown by a finite element analysis with aluminum foam core sandwich specimen subjected to blast loading.