Abstract Thin-walled tubular structures are widely used in industries such as automotive, aerospace and military because of their lightweight and excellent performance under different loading conditions. This study aimed to investigate the lateral crushing performance of square aluminium tubes filled with different cores (honeycomb, polyurethane foam and mixed of these two fillers). Different failure modes of tested structures have been observed and they are progressive failure with plastic hinges formed in the middle of the tube wall, cracks at the corners of some tested tubes and fractures in the mixed foam and honeycomb core. Results show that the lateral crushing performance of aluminium tubes was significantly improved when using mixed filler (honeycomb and foam). The average load, energy dissipation and specific energy absorption of mixed core filled tubes increased up to 638%, 451% and 177% respectively when compared to those for hollow tubes.

In this study, the effects of cobalt and nickel additions on microstructure evolution and mechanical properties of Al-Zn-Mg-Cu alloys produced by chill casting process were investigated. Al-Zn-Mg-Cu aluminum alloys containing Ni and Co additives were homogenized at different heat treatment conditions, aged at 120ºC for 24 h, and retrogressed at 180ºC for 30 min then re-aged at 120ºC for 24h. Comparison of the ultimate tensile strength of the Al-Zn-Mg-Cu base alloy underwent RRA temper process with that of the base alloy underwent a similar heat treatment process after the addition of 0.5 wt. % Ni and 0.5 wt. % Co showed that the gains of tensile strengths of the orders of 100 MPa and 135 MPa were attained respectively. These improvements are attributed to phase dispersion particles of the formation of Ni and Co-rich such as Al7Cu4Ni, Al75Ni10Fe15, Al3Ni2 and Al70Co15Ni15. The dispersed particles of nickel or/and cobalt have improved the ultimate tensile strength to reach 630 MPa and 665 MPa and the hardness HV values to 250 MPa and 265 MPa respectively. Besides dispersion, Ni and Co intermetallic dispersoids retarded the grain growth, led to grain refinement and precipitation hardening and resulted in further strengthening of the Al alloy. Microstructure characterization of the alloys was carried out using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD).