: One thing that I find very interesting is that in the tests you cite, the
: glass failed on the compression side, yet in the tests cited in
: Kayakcraft, the glass always failed on the tension side. It would seem
: that there must be substantial differences in the test methodologies
: involved. Considering that the stress on a flexed composite panel is
: primarily in the tension side, I wonder if the recent tests simply applied
: pressure over a very small area (a sharp point or edge), causing crush
: failures on the compression side? Does anyone out there have more details
: on the exact method of stress application in these two sets of tests?

I am not familiar with the tests cited in Kayakcraft. However, I doubt that the differences between their results and ours are due to test methodologies. In our tests, failure occurred in the tension side of all the specimens having the wood grain oriented along the long-axis of the specimen (parallel to the direction of principle stresses). When the wood grain was oriented perpendicular to the long-axis, failure occurred in the skin experiencing compression and in the wood core. Therefore, we had two classes of behavior, which reflected the two wood grain orientations.

Load concentration can not explain the compression side failures because in most instances localized failure occurred away from the loading point. The simple explanation is that the wood core significantly contributes to the strength of the panel. In the case of wood grain perpendicular to the principle stresses, the wood core initiates failure, which leads to buckling of the skin in compression. Core failure and buckling of the skin in compression prevented failure in the tension side of the composite. All the tests were conducted in 3-point bending.