Quasi-static axial crushing and transverse bending of double hat shaped CFRP tubes

This paper aims to explore the failure modes and crashworthiness characteristics of double hat shaped tubes made of weave carbon fiber reinforced plastic (CFRP) subjected to quasi-static axial crushing and transverse bending. Experimental investigations were carried out into three different thicknesses of the composite tubes fabricated by the bladder molding process. Three distinct failure modes, classified as progressive end crushing (I), unstable local buckling (II) and mid-length collapse (III), were observed in the axial crushing tests, whereas only one similar progressive collapse mode was observed in transverse bending tests. It is shown that the thickness is a critical parameter affecting the failure mode and energy absorption capability, leading to the increase in the peak load and specific energy absorption (SEA) during the tests. The SEA of the tested double hat shaped tubes under axial crushing ranges from 60 to 90 J/g, which is marginally higher than that of regular sectional CFRP tubes but over 2 times of that of conventional metallic tubes. By comparison, the load bearing and energy absorption capabilities of the tubes under transverse bending are much lower than those of the axially compressed tubes (less than 10% and 1%, respectively).