Composite steel–CFRP SHS tubes under axial impact

Composite steel–carbon fibre reinforced polymer (CFRP) tubes combine the benefits of the stable, ductile plastic collapse mechanism of the steel and the high strength to weight ratio of the fibre/resin composite, to form a composite tube with high energy absorption capability. This paper presents experimental results of square hollow section (SHS) composite steel–CFRP tubes subjected to axial impact. A number of different steel SHS geometries and two different matrix layouts of the CFRP are investigated. The dynamic results are compared with quasi-static results of composite steel–CFRP SHS and dynamic results of steel SHS and CFRP SHS. It is shown that the crashworthiness properties of load uniformity and specific energy absorption of the composite steel–CFRP tubes exceed those of the steel-only and CFRP-only tubes. An additional advantage of the CFRP application technique is that the CFRP may be retro-fitted to existing steel tubes, and the energy absorption capacity is shown to be markedly improved by such application. A theoretical method to calculate the dynamic mean crushing load which includes the effects of strain-rate is shown to compare well with the experimental results.