Experimental evaluation of axial crush behavior of woven tubular laminates with a moving support condition

The objectives of the investigation were to measure the specific energy absorption (SEA) of the plain-weave carbon fiber reinforced polymer (CFRP) tubes, study the effect of tube length on SEA and stable crushing force, analyze the effect of using a crush trigger, and compare force-displacement data using different specimen support conditions. Dynamic crush testing of CFRP tubes was performed using the crash sled in the Impact Dynamics Laboratory at NASA Glenn Research Center. The sled features a movable mass that supports the specimen during crash testing. Laminated [±45]₄ tubes were fabricated and tested using tube lengths of 102 mm or 152 mm each with a diameter of 76 mm. Sled impact velocities ranged from 6.15–6.48 m/s. In most tests, a crush trigger was applied to the front face of the tubes to initiate a crushing failure mode. The mean SEA of the tubes tested with the crash sled was 48.6 J/g. There were virtually indistinguishable changes in failure modes for the 102-mm and 152-mm tubes. Plots of acceleration and cumulative absorbed energy for both tube lengths were nearly identical, which suggests that the effect of tube length on crush behavior was negligible in the range of tested impact velocities. One of the 102-mm tubes was tested without a crush trigger to provide a direct comparison with a drop tower specimen that lacked a crush trigger. A higher peak force and lower SEA was measured for this specimen compared to the specimens that had a crush trigger. Both the peak force and stable crushing force were comparable for the drop tower and crash sled specimens lacking a crush trigger. However, the maximum crush displacement of the crash sled specimen was lower because a portion of the energy was absorbed by the motion of the support mass.