Experimental investigation into static and dynamic axial crush of composite tubes of glass-fiber mat/PA6 laminates

In this paper, the results are present of an experimental investigation into quasi-static and dynamic crushing responses and crashworthiness characteristics of round-hat-shaped crash tubes made with glass long-fiber-mat/PA6 laminates of around 45 vol%. These characteristics were explored using a high-dynamic hydraulic test machine. The crash tubes failed by the progressive splaying mode except for some tubes in the quasi-static tests, which failed by the mid-length collapse mode. The specific energy absorption (SEA, 42.0 J/g) in the quasi-static tests increased to around 52 J/g in the dynamic tests. The increased energy absorption at the higher test speed was analyzed through the microscopic behavior of the small bending radius of the splayed laminar bundles and fragmentation of the lamina bundles. The drop-tower tests show that the dependency of the performance of the crash tubes on the test speed appears only at relatively low speed (1 m/s in the limited tests reported in this paper), but the performance becomes relatively steady at much higher impact speeds. The impactor mass and tube length had almost no effect on the crash characteristics of the mean crushing load, SEA, and peak load.