The Crush Behavior of Pultruded Tubes at High Strain Rates

Abstract

The effect of fiber diameter, trigger geometry and section geometry on the crush response of pultruded glass fiber reinforced plastic tubes, made with either polyester or vinyl ester resin, was determined at crush rates from 2.1 x 10-4 m/s to — 15 m/s. The rate dependence of the specific energy for the polyester resin tubes was positive, whereas that for the vinyl resin tubes could be either positive or negative, depending upon the par ticular tube geometry. Increases in the specific energy absorption, previously observed in quasi-static loading, caused by changes in the crush trigger geometry, were found also for dynamic loading. Reductions in the fiber diameter by one half (nominal), for the same glass content, decreased the specific energy by up to ∼20%. Differences in the resin affect the quasi-static crush resistance, the vinyl ester resin tubes having a significantly higher specific energy than that of the polyester resin tubes. These differences tend to diminish for dynamic crush. Fiber delamination occurs more profusely under dynamic loading con ditions, and it is suggested that a crush mode change occurs on passing from quasi-static to dynamic loading. A tendency to crush in an unstable manner was found for some square sections under dynamic loading, possibly due to the accumulation of crush debris in the tube interior.