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To maintain the robustness of crashworthiness performance in energy absorbing structures, high specific energy absorption (SEA) and crush force efficiency (CFE) need to be maintained across a wide range of load angles. In this paper, concave design was proposed to address this issue. Finite element analysis was utilised to identify the main load-bearing elements for axial and shear loading. Furthermore, the design concepts were classified into surface variation and cross-section variation. Pattern design, which is a representative design of surface variation, can enhance crashworthiness performance by reducing the initial crushing load and maximising the development of a travelling hinge. However, there is a drawback that designing the cross-section to maximise the development of the travelling hinge leads to an increase in the dihedral angle, resulting in a decrease in the CFE. This paper proposed the concave design, that ensures excellent robustness of crashworthiness performance and minimised the trade-off between SEA and CFE performance under combined shear-compression loading. The design induces local crushing due to geometric imperfections, which reduces the peak load while maintaining the high load-bearing capacity, thereby increasing SEA. Furthermore, the surface of the energy absorbing structure is an important load-bearing component that supports shear loads, and the concave design induces progressive crushing modes for any load angle, thereby maximising the deformation of the surface and improving SEA. The structural characteristics of the concave design were validated through quasi-static loading tests. [ABSTRACT FROM AUTHOR]

In this paper, the energy absorption performance of braided composite tubes under combined shear-compression loading is investigated. ABAQUS/Explicit is employed to analyze the energy absorption of braided composite tubes, and quasi-static compression tests are carried out. Braided composite materials absorb energy through the damage accumulation in laminate. Thus, to maximize energy absorption performance, a progressive crushing mode should be induced. While extensive research has been conducted on cases of axial loading, understanding of the energy absorption performance of braided composite tubes under combined shear-compression loading remains limited. Experimental results reveal that under both axial and combined shear-compression loading at 30 degrees, the braided composite tube exhibits a progressive crushing mode. The test results are utilized to validate the finite element model. Through finite element analysis, it is confirmed that the damage accumulation in laminate is maximized due to the induction of a progressive crushing mode. It means that the energy absorption principles of braided composites apply similarly to combined shear-compression loading, allowing for the maintenance of superior energy absorption performance of braided composites under various load angles. [ABSTRACT FROM AUTHOR]

The crease line formed in an origami-shaped crash box (OSCB) acts as a geometric imperfection and mode inducer. Such geometric imperfections make it possible to protect occupants by lowering the peak force in the event of a collision. The OSCB also shows desirable performance as a crashworthy structure by inducing a collapsing mode with excellent energy absorption. There are many studies on crash boxes with origami patterns applied, but few studies on performance optimisation. This article describes the structural optimisation of an OSCB to maximise the specific energy absorption (SEA) by setting the corner length c and module length l as design variables. Numerical and experimental investigations of the crashworthiness performance were conducted by comparing the optimised OSCB to a circular crash box (CCB), which is known to have the best SEA among straight tubes. The numerical and experimental results were in good agreement, with the optimised OSCB collapsing into the diamond mode. The results of the numerical comparison showed that the SEA and the crush force efficiency (CFE) of the optimised OSCB were increased by 5.94% and 115.58%, respectively. However, in a quasi-static axial crushing experiment, the SEA of the optimised OSCB was 10% lower than that of the CCB, and the CFE was increased by 88.5%. The optimised OSCB in this study displayed an improvement in the SEA compared to the reference OSCB, as well as a reduction in the difference from the CCB, indicating high maintenance performance of the CFE. [ABSTRACT FROM AUTHOR]