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Composite structures combine the advantages of multiple materials, which can improve the structural crashworthiness performance. This paper aims to combine the high strength of carbon fibre-reinforced plastic (CFRP), the excellent ductility of aluminium alloy (Al), and the good compressibility of polyurethane (PU) foam. Quasi-static compression and low-velocity impact tests were conducted on thin-walled tubes made of single materials and composite sandwich structures made of multi-materials, namely Al-PU-Al, Al-PU-CFRP, CFRP-PU-Al, and CFRP-PU-CFRP. The structural failure modes and crashworthiness indicators were analysed and compared under different loadings. The results showed that the CFRP thin-walled tube exhibited a progressive damage and failure mode, and the resultant force changed smoothly. The CFRP tube possessed a larger mean crushing force and specific energy absorption than the corresponding aluminium tube. Composite structures exhibited more stable deformation mode and higher energy absorption, compared with the sum of linear superposition (SLS) of individual components, due to the interaction effects among components. Among the designed four combinations, CFRP-PU-CFRP exhibited an ideal energy absorption under both quasi-static and dynamic impact, while CFRP-PU-Al produced the second highest specific energy absorption (SEA), with an increment of 42.0% compared with Al-PU-Al. With full consideration of crashworthiness performance and economic cost, CFRP-PU-Al can be recommended as an impact energy absorber for vehicles due to its lower economic cost than CFRP-PU-CFRP. [ABSTRACT FROM AUTHOR]

Composite structures have drawn growing attention for their outstanding characteristics benefiting from the combination of multi materials. This paper aims to investigate the crushing performance of a hybrid system involving an outer thin-walled tube made of carbon fibre-reinforced plastic (CFRP), a medial polyurethane (PU) foam and an inner thin-walled tube made of aluminium alloy (Al). The elastoplastic model of Al, the continuous damage model of CFRP and the compressible foam model of PU were established with assistance of universal material tests. The finite element model of the composite structure, namely CFRP-PU-Al, was validated by the experimental study. Based upon the reliable numerical modelling, the parametric study was carried out for exploring the effects of the wall thickness, diameter and ply orientation of the outer CFRP tube, namely CFRP-O, on the crushing behaviours of the composite structure. It was found that increasing the diameter or wall thickness of CFRP-O was helpful to increase the mean crushing force and energy absorption of CFRP-PU-Al, however, the overall specific energy absorption of the composite sandwich structure was limited by the characteristics of constitutive materials. Compared with the diameter, the wall thickness had a higher impact on the energy absorption characteristics, and increasing the diameter may decrease the specific energy absorption due to the increase of the overall structural mass. In terms of the ply orientation, the composite structure with stacking sequence of [0°/45°] 3 possessed higher mean crushing force and energy absorption than the structure with stacking sequence of [0°/90°] 3 under axial compression in this study. • Composite sandwich structures made of multi-materials were designed and fabricated. • Material constitutive models were established and the finite element model was validated by experiments. • The parametric effects of CFRP thin-walled structure on the crushing performance of the composite sandwich structure were clarified. [ABSTRACT FROM AUTHOR]

Hybrid structures have the advantage of combining different types of materials at the same time. The trend of lightweight design in the transportation industry has promoted the development and application of composite materials with good crashworthiness performance. Low-density crushable foam-filled metal-composite hybrid structures have potential advantages as energy-absorbing components. This study investigated the mechanical characteristics of four different polyurethane foam-filled hybrid structures and their individual components under quasi-static axial compression. The experimental results showed foam-filled hybrid structures could change the deformation mode and improve stability during the compression process. Meanwhile, these hybrid structures could also improve energy absorption compared with their individual components. Among the different configurations, specimen C-PU-C (i.e., polyurethane foam filler between an outer CFRP tube and an inner CFRP tube) had the highest energy absorption capacity, at 5.4 kJ, and specific energy absorption, at 37.3 kJ/kg. Finally, a finite element (FE) model was established to analyze the mechanical characteristics of the hybrid structures by validating the simulation results against the experimental results. [ABSTRACT FROM AUTHOR]