Crushing and energy absorption mechanisms of carbon fiber-epoxy tubes under axial impact

The energy absorption capability of carbon fiber-epoxy tubular specimens having closed circular and open C-shape cross-sections was investigated using experimental tests when focusing on the effect of the layup configuration. Specimens were subjected to a wide range of loading rates ranging from axial quasi-static compression to axial impact loading in order to reveal the deformation mechanism of CFRP samples. Several different combinations of mass and velocity of the striker were selected to study the possible effects on the crushing behavior of composite specimens. C-section specimens were used to investigate the effects of the cross-section shape on the crushing performance of carbon fiber material and to provide a better step-by-step visual understanding of the damage initiation and propagation in each layer due to quasi-static compression. It was observed that, in general, the different stacking sequences and loading conditions had minor effects on the SEA value of full-tube specimens while a significant difference between SEA values of C-section specimens with different layups was found. The calculated SEA value of C-section cross-plied specimens was lower than the SEA value of the full circular tubes having the same stacking sequence while an insignificant difference between the SEA values of C-section and full circular tube specimens of angle-ply layup configuration was observed. It was established experimentally that the removal of the outer layer with fibers oriented along the tube axis has no significant effect on the crushing force value under quasi-static compression. As a sequence, the SEA value increased due to the decrease of the total absorber weight.