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From the same paper as the previous slide.
Relative to this figure Professor Daniel writes:
“Figure 15 shows moment versus strain results for two different tests of sandwich beams with Divinycell H100 foam cores under four-point bending. Evidence of wrinkling is shown by the sharp change in recorded strain on the compression facesheet, indicating inward and outward wrinkling in the two tests. In both cases the critical wrinkling stress was σcr = 673 MPa. Heath’s relation ([Eq] 13) [Heath 1960] was selected because of the lack of shear interaction due to the pure bending loading. The predicted critical wrinkling stress of 667 MPa is very close to the experimental value.”
References:
[Heath 1960] W. G. Heath, “Sandwich construction: correlation and extension of existing theory of flat panels subjected to lengthwise compression”, Aircr. Eng. Aerosp. Technol. 32:8 (1960), 230–235.
[Hoff and Mautner 1945] N. J. Hoff and S. E. Mautner, “The buckling of sandwich-type panels”, J. Aeronaut. Sci. 12:3 (1945), 285–297.
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