Investigation on quasi-static compression of circular CFRP tubes: effect of EPP foam filling

This research aims to experimentally investigate the effect of carbon fiber thickness and foam density on the crashworthiness of circular CFRP tubes under quasi-static axial loading. CFRP tubes were manufactured with different plies numbers of 6, 8 and 10. An apparatus was designed and used to obtain identical CFRP tubes related to the manufacturing process. Closed-cell expanded polypropylene (EPP) foam with two different densities as 30 kg/m(3) and 60 kg/m(3) was used as the reinforcement material to enhance the energy absorption capability. The highest absorbed energy value was obtained in the 60 kg/m(3) EPP foam-filled 10-ply CFRP tube as 10.430 J. In terms of the highest increase in absorbed energy by using EPP foam was obtained in the 60 kg/m(3) EPP foam-filled 6-ply CFRP tube at 101%. This increase remained at the level of 75% and 17% in the 8 and 10-ply CFRP tubes, respectively. As a result, the 60 kg/m(3) density EPP foam-filled 8-ply CFRP tube was the best crash box design in terms of the specific energy absorption and crush force efficiency parameters even though it did not absorb the highest energy. Lastly, aluminum tubes with a wall thickness of 2 mm were used to examine the EPP foam filling effect on the absorbed energy of the metallic tube. It is observed that the EPP foam is an efficient reinforcement material with composite tubes in contrast to aluminum ones.