Non-stationary oscillations of sandwich plates under local dynamic loading

The paper addresses the elastic response of composite sandwich panels to local\ud dynamic loading. The plane and axisymmetric formulations are considered; no\ud overall bending is assumed. The governing equations are derived using the static\ud Lamé equations for the core and the plate Kirchoff-Love dynamic theory for the\ud faces. The closed form solutions for the non-stationary excitation are obtained\ud using integral transformations technique. The solutions allow to predict the stressstrain state of the structure and are in good agreement with finite element analysis

Сравнительная клинико-гормональная характеристика состояния здоровья и качество жизни женщин с хирургической и естественной менопаузой

ГОРМОНЫДЕПРЕССИЯЖЕНЩИНЫКАЧЕСТВО ЖИЗНИМЕНОПАУЗАПОСТМЕНОПАУЗ

Failure of Sandwich Structures with Sub-Interface Damage

NR 2014080

Deformation of Foam Cores in Uniaxial Compression-Tension Cycle

This article deals with experimental and analytical analysis of the mechanical behavior of crushed foam cores. Three rigid cellular core materials are tested in a uniaxial compression-tension cycle. An analytical model is proposed describing the stress-strain curve in tension and secondary compression. A special emphasis is laid on the relaxation behavior of a crushed foam core in tension

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

Compression-after-impact strength of sandwich panels with core crushing damage

Compression-after-impact (CAI) strength of foam-cored sandwich panels with composite face sheets is investigated experimentally. The low-velocity impact by a semi-spherical (blunt) projectile is considered, producing a damage mainly in a form of core crushing accompanied by a permanent indentation (residual dent) in the face sheet. Instrumentation of the panels by strain gauges and digital speckle photography analysis are used to study the effect of damage on failure mechanisms in the panel. Residual dent growth inwards toward the mid-plane of a sandwich panel followed by a complete separation of the face sheet is identified as the failure mode. CAI strength of sandwich panels is shown to decrease with increasing impact damage size. Destructive sectioning of sandwich panels is used to characterise damage parameters and morphology for implementation in a finite element model. The finite element model that accounts for relevant details of impact damage morphology is developed and proposed for failure analysis and CAI strength predictions of damaged panels demonstrating a good correlation with experimental results.QC 20100525</p

Compression-after-impact strength of sandwich panels with core crushing damage

Compression-after-impact (CAI) strength of foam-cored sandwich panels with composite face sheets is investigated experimentally. The low-velocity impact by a semi-spherical (blunt) projectile is considered, producing a damage mainly in a form of core crushing accompanied by a permanent indentation (residual dent) in the face sheet. Instrumentation of the panels by strain gauges and digital speckle photography analysis are used to study the effect of damage on failure mechanisms in the panel. Residual dent growth inwards toward the mid-plane of a sandwich panel followed by a complete separation of the face sheet is identified as the failure mode. CAI strength of sandwich panels is shown to decrease with increasing impact damage size. Destructive sectioning of sandwich panels is used to characterise damage parameters and morphology for implementation in a finite element model. The finite element model that accounts for relevant details of impact damage morphology is developed and proposed for failure analysis and CAI strength predictions of damaged panels demonstrating a good correlation with experimental results.QC 20100525</p

Residual dent in locally loaded foam core sandwich structures – Analysis and use for NDI

This paper addresses the residual denting in the face sheet and corresponding core damage in a locally loaded flat sandwich structure with foam core. The problem is analytically considered in the context of elastic bending of the face sheet accompanied by non-linear deformation of the crushed foam core. The plane and axisymmetric formulations are studied. The obtained solutions allow for the estimation of the magnitude of the residual face dent through the size of the crushed core zone (or vice versa). Thus, the analytical background is proposed for a non-destructive inspection of locally indented/impacted sandwich structures. The solutions are verified experimentally

Compression strength of sandwich panels with sub-interface damage in the foam core

This paper addresses the effect of a local quasi-static indentation or a low-velocity impact on the residual strength of foam core sandwich panels subjected to edgewise compression. The damage is characterized by a local zone of crushed core accompanied by a residual dent in the face sheet. Experimental studies show that such damage can significantly alter the compressive strength. Theoretical analysis of the face sheet local bending is performed for two typical damage modes (with or without a face–core debonding). The solutions allow estimation of the onset of (a) an unstable dent growth (local buckling) or (b) a compressive failure in the face sheet. The theoretical results are in agreement with the test data for two considered sandwich configurations