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From the same paper as the previous image.
The authors write:
“The resulting force–displacement responses are shown in Fig. 6. It can be seen that the postbuckling responses of the hybrid cylinders had a smaller number of mode transitions (load drops in the load–displace- ment response) compared to the carbon/epoxy cylinder (Fig. 5). The [0/G/90] cylinder was subjected to an axial shortening of 0.7 mm. The buckling pattern for this cylinder started on the carbon strips and then triggered a significant snap-through buckling event in the neighboring E-glass zones. Seeking to increase the number of mode transitions in the postbuckling regime the [45/G/ 45] cylinder was subjected to a shortening of 0.95 mm. However, no significant increase in the number of snap-buckling events were observed (two major snap- buckling events) as local buckling occurred in the E-glass zones and the buckling waves in this design had difficulty propagating along the circumferential direction. The [30/G/ 30] cylinder was shortened 50% more compared to the [0/G/90] cylinder (1.4 mm). This design was found to have a more desirable behavior in the postbuckling regime than the other two cases by presenting a large number of distinct snap-buckling events. A summary of results is provided in Table 3. This experimental study indicates that the hybrid design concepts can allow for localized snap-buckling events to be triggered in certain regions of the shell due to the use of carbon/epoxy strips as artificial imperfections. Even though the cylinders were still sensitive to imperfections (mainly due to manufacturing flaws) it was interesting to see that buckling occurred in specific regions rather than at random locations on the shell surface.
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