The crushing behavior of E-glass~polyester and E-glass/vinyl ester pultruded tubes has been found to be significantly different for tulip triggered specimens as compared with bevel triggered specimens. Up to 100% more energy per unit weight was absorbed by tulip triggered tubes. In addition, the crushing was more controlled and predictable with the tulip trigger. The morphology of the material in the crushing zone differed in the amount and the pattern of fracture. The fracture pattern and crushing behavior initiated by both triggers were foundnot to change during crushing. The difference in crushing appeared to arise from the different abilities of the tubes to support load because of the different geometry of individual load-carrying structures that resulted from triggering.

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Two types of non-axial crushing, off-axis crushing and angled crushing, have been identified and significant differences found between the E-glass/polyester pultruded tubes crushed in these different configurations. Energy absorption for the two types of crushing was found also to vary significantly with the angle of inclination, with the difference being largest at high angles of inclination. Reasons for energy absorption differences between the crushing configurations include the initiation of different crack patterns, different loading of individual fibers, and altered friction. For all angles, the load required for continued crushing was found to fluctuate more for off-axis crushing than for angled crushing.

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