Energy absorption and failure pattern of hybrid composite tubes under quasi-static axial compression

Novel fiber-metal hybrid tubes with overlapped fiber reinforced plastics (FRP) and aluminum layers were proposed in this paper. By combining progressive failure behavior of composites and large plastic deformation of metal materials, the structure was hybridized at mesoscopic scale. To this end, circular fiber/aluminum hybrid tubes with various inner diameters (40, 60, and 80 mm) combined with parent materials (Al-1060, carbon fiber, and glass fiber) were fabricated using vacuum bag molding process. Quasi-static uniaxial compressive tests were conducted to comprehensively explore the effects of geometric factors and failure patterns on energy absorption capability. The experimental results revealed that the pristine FRP and CF/Al (carbon fiber and aluminum) hybrid tubes collapsed in a progressive failure mode and generated abundant intra- and inter-laminar cracks during crushing. The GF/Al (glass fiber and aluminum) hybrid tubes with large diameters collapsed in an unstable and inefficient mode due to local buckling and delamination. Compared with bare aluminum tubes (Al 6061-T6), the specific energy absorption (SEA) and crushing force efficiency (CFE) of CF/Al hybrid structures were improved significantly by respectively 54.3% and 40.4% for tubes with 40 mm inner diameter. Furthermore, the CFE of CF/Al hybrid structures improved by more than 40% when compared to their bare CFRP counterparts, though the SEA reduced by more than 5.5%. In sum, the proposed hybrid design efficiently reduced the peak crushing force with desirable SEA, which has great potential for low-cost and lightweight energy absorber applications.