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Figure 13 apparently shows a buckling mode, but one cannot see just what this mode is. It appears to be associated with local conditions adjacent to the end supports, and it has a very short axial wavelength. Perhaps it is local core/skin kinking or core shear crimpling? The other three figures are clear.
FROM:
Hassan Mahfuz (1), Syful Islam (1), Leif A. Carlsson (2), George A. Kardomateas (3) and Shaik Jeelani (1)
(1) Center for Advanced Materials, Tuskegee Univesity, Alabama, USA
(2) Florida Atlantic University, Boca Raton, USA
(3) Georgia Institute of Technology, Atlanta, USA
“Buckling response of sandwich composites: Effect of core density and implanted interface cracks”, Paper ID 1452, (Publisher and date not given in the “pdf” file; the most recent reference is dated 1998.)
ABSTRACT: Buckling response of foam core sandwich composites with various core densities and implanted delaminations have been investigated. Klegcell foams with densities ranging from 75-300 kg/m^3 were used in the analysis. Various lengths of delaminations were introduced between the face sheets by implanting non-porous Teflon during the construction of the sandwich. The idea was to determine the influence of a/L (Crack length over the length of specimen) on the critical strain. The study further investigated the effect of interface crack in controlling/accelerating the core shear and local buckling of the face sheet. Buckling tests were carried out with simple support end conditions on a newly designed test fixture. Both in- and out-of-plane displacements were recorded and were utilized in determining the critical buckling loads. Both FEM and analytical calculations were carried out to determine the initial and post-buckling responses. They were later compared with the experimental data. Failure modes with various core densitites have also been identified, and their relationship with interface crack propagation has been determined. Details of the experimental, finite element and analytical work are presented in this paper.
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