Vitaly Koissin

The elastic response of sandwich structures to local loading

The paper addresses the elastic response of sandwich panels to local static and dynamic loading. The bottom face is assumed to be clamped, so that the overall bending is eliminated. The governing equations are derived using the static Lame equations for the core and the thin plate Kirchoff–Love dynamic theory for the faces. The plane and axisymmetric formulations are considered. The closed-form solutions are obtained using Fourier–Laplace (Hankel–Laplace) integral transformations for the cases of forced excitation and impact by a rigid body. The solutions allow to predict the stress–strain state of the structure. The analytical solutions demonstrate a good agreement with experimental data and finite element analysis.

Effect of Physical Nonlinearity on Local Buckling in Sandwich Beams

This article deals with experimental, theoretical, and FE characterization of the local buckling in foam-core sandwich beams. In the theoretical approach, this phenomena is considered in a periodic formulation (unbounded wrinkle wave); a nonlinear stress—strain response of the face material is accounted for. In the FE approach, nonlinearity of the core material is also modeled. Full-field strain measurement is employed in the tests showing that the commonly used edgewise compression set-up can cause premature waviness of the faces, and therefore, nonlinear local deformations in the core layer.

Wrinkling in sandwich panels - an analytical approach

This article deals with theoretical modeling of the local buckling in foam–core sandwich panels. This phenomenon is considered mainly in the periodic (unbounded wrinkle wave) and linearly elastic formulation. The analytical solutions are in agreement with results of finite element analysis and can be applied with a good precision for many finite-size panels, as well as for many sandwiches having honeycomb cores.

Residual In-plane Mechanical Properties of Transversely Crushed Structural Foams

The mechanical properties of structural polymer foams are investigated after crushing in the rise direction (out-of-plane axis of a foam material block). The crushed foams are loaded in uniaxial compression, tension, or shear. All tests are performed in the plane of the foam block, i.e., perpendicular to the crushing direction. For comparison, virgin foams are also characterized. The results are discussed featuring the properties of crushed foams, which can be important for the damage tolerance analysis of a foam core sandwich structure.