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The variable thickness hybrid square (VTHS) tubes are used to improve the energy absorption under oblique loading and the relative advantages compared with the uniform thickness hybrid square (UTHS) tubes are studied. First, a oblique compression test and finite element model were established to analyze the deformation mode and load-displacement curve of VTHS tube. Then, the parameter studies of VTHS and UTHS tubes were carried out. The results show that increasing thickness leads the structures to be prone to global bending mode, and the energy absorption performance is reduced. Compared with UTHS, VTHS tubes can increase the specific energy absorption when the progressive crushing mode occurred at the same loading angle. Meanwhile, the progressive crushing deformation with excellent energy absorption performance can still appear when the loading angle exceeds 30°. Finally, a unified equation for the relationship between the dimensionless mean crushing force and the loading angle was proposed. [ABSTRACT FROM AUTHOR]

Square-circle hybrid section (SCHS) tubes under axial loading which combine the advantage of square tubes and circular tubes are investigated. Firstly, effective finite element models of SCHS tubes are established to study the crashworthiness characteristics. Through a series of finite element models, the influence of the geometry on the behaviour of crashworthiness is studied, including relative size of square and circular sections in SCHS tubes and the position of connecting plates. The results show that compared with corresponding traditional multi-cell tubes, SCHS tubes improve the performance in energy absorption, with a maximum increase of 40.49%, while reducing peak force and improving crushing load efficiency. Moreover, the deformation of elements constituting the SCHS tube is analysed, and deformation of arc-plate elements could be classified into three typical modes. According to the observed deformation modes, the theoretical model is proposed to predict the mean crushing force of SCHS tubes. The theoretical results show that it is in good agreement with the numerical results. [ABSTRACT FROM AUTHOR]

This article deals with initial material selection and design method of long fibre-reinforced thermoplastic (LFT) based on impact resistance requirements. In this study, effects of material properties and impact condition, including total fibre thickness, fibre aspect ratio and impactor diameter, on the minimum penetration energy of LFT plates are analysed based on experiments and validated numerical models. Mathematical expression is established between them. Applicability of the original model for LFT plate with different fibre aspect ratios subjected to different impactors is discussed. The minimum penetration energy is used as the bridge between energy absorption characteristics and material parameters, impact condition. Finally, an updated theoretical model for energy absorption analysis is proposed. We conclude that the updated semi-empirical model is a valuable tool for a first stage material selection and design. [ABSTRACT FROM AUTHOR]

• Analysis of the effect of axial constraint force on the bending energy absorption of square tubes based on three-point-bending and fully clamped bending experiments. • FE models of square tubes under variable axial constraint condition are established and verified. • Deformation and energy adsorption effect of square tubes under variable axial constraint condition. • Theoretical analysis is conducted on square tubes under three different types of variable axial constraint properties. Thin-walled tubes in the actual engineering structure (e.g., autobody) are usually connected to other structure, and the boundary constraint condition at both ends of tubes are usually very complex when bending deformation occurs under transverse loading. This paper aims at the effect and mechanism of axial constraint on the bending energy absorption effect of thin-walled tube under limited and variable axial constraint condition at both ends. A typical of thin-walled tube, square tube, is taken as an example. Firstly, we compare the experiment results of square tube under transverse loading with three-point-bending condition and fully clamped condition, revealing that the axial constraint force has a significant effect on the energy absorption effect. After that, a FE model of the square tube under variable axial constraint condition at both ends is established and validated based on experiment. Based on the validated FE model, the effect of different sizes of axial constraint stiffness on the bending energy absorption of square tube are investigated, and it is found that it has a significant effect on the deformation mode and bending energy absorption. With the increase of axial constraint stiffness, it will mainly affect the latter segment of the force–displacement curve in the bending process, which increases the bending energy absorption. Finally, theoretical models are developed to predict the force–displacement curves and bending energy absorption of the square tube under three different types of variable axial constraint properties: linear axial constraint, unequal linear axial constraint and nonlinear axial constraint. [Display omitted] [ABSTRACT FROM AUTHOR]

The yield curve for bi-material structures is proposed and applied to energy absorption analysis of fully clamped FML beam with CFRP and metal under transverse load. Firstly, fully clamped FML beam tests under transverse loading are performed to acquire the energy absorption response. Then, a unified yield criterion for bi-material structures, that contains metal and fiber reinforced plastic and CFRP has asymmetry properties under tensile and compressive load, is established and discussed. Based on the yield criterion, a theoretical analytical model for the large deformation to predict energy absorption of fully clamped FML beams with shear angle-ply under the transverse load is developed. Finally, comparison of results obtained by theoretical solution and experiments show that the theoretical analysis can predict the energy absorption capacities of FML beams. In addition, effect of significant parameters on yield curves and energy absorption capacity are discussed. [ABSTRACT FROM AUTHOR]

Curved tubes are widely used on autobody to suffer the transverse bending loads. This paper studies the energy absorption performance of curved tubes under transverse bending load. Firstly, three-point-bending and fully clamped bending experiments are conducted for three kinds of curved tubes with different radii. It is found that the curvature has a significant impact on the energy absorption effect under the fully clamped condition. However, the influence is limited and it will be easily ignored in the three-point-bending condition. Under fully clamped condition, tubes with large radii have three-plastic-hinges, and curved tubes with small radius have five-plastic-hinges. Due to the participation of axial force, the energy absorption of the curved tubes under fully clamped condition is 2.8–4.1 times that of the three-point-bending condition. Subsequently, FE models of curved tubes with different radii are established to analyze the effect of curvature on the deformation mechanism and energy absorption. It is found that whether the shortening of the plastic hinges can meet the requirements of geometric compatibility determines the deformation modes of curved tubes. The influence of loading (loading direction) and geometric (cross-section and thickness) factors are also discussed. Finally, a theoretical model of curved tubes with three-plastic-hinges mode is proposed to predict the energy absorption performance. • Three-point-bending experiments and fully clamped bending experiments are conducted on curved tubes. • FE models of curved tubes are established and verified by experimental results. • How the curvature influences the energy absorption mechanism of tubes under transverse loading is presented. • The effects of loading direction, cross-section and thickness on curved tubes are discussed. • Theoretical analysis is conducted on curved tubes with three-plastic-hinges mode under fully clamped condition. [ABSTRACT FROM AUTHOR]

This paper investigates energy absorption performance of multi-cell tubes considering the influence of axial constrain in bending process Firstly, three-point-bending tests and fully clamped bending tests were conducted. Experimental results showed that the energy absorption of tubes increased to 2.5–3 times if the end of the tube is constrained. Based on the FE model verified by experiments, the effect of rib direction and rib number is investigated under fully clamped condition. Results show that the multi-cell tubes with rib parallel to the load direction (MT-Y0Zn) have better energy absorption performance than that with rib perpendicular to the load direction (MT-YnZ0), especially in the frontal part of bending process. Meanwhile, following with the increase of rib number, specific energy absorption (SEA) of MT-Y0Zn increases gradually, while SEA of MT-YnZ0 remains almost unchanged. Considering the fact that MT-Y0Zn shows better energy absorption performance, theoretical model of MT-Y0Zn is established and highly consistent with FE model. Finally, the influence of thickness and cross-section size is discussed. SEA increases with increase of cross-section and remains unchanged with increase of thickness as predicted by theory. However, when cross-section exceeds 80 mm or thickness is smaller than 1 mm, local denting caused by shear force decreased SEA significantly. • Three-point-bending and fully clamped bending tests are conducted on multi-cell tubes. • FE models of multi-cell tubes under fully clamped condition are established and verified. • Effect of rib number and direction is studied under fully clamped condition. • Theoretical analysis is conducted on multi-cell tubes under fully clamped condition. • Theoretical and FE model are used to discuss the influence of cross-section size and thickness. [ABSTRACT FROM AUTHOR]

Compared with the excellent energy absorption performance under axial loading, thin-walled tubes are vulnerable to unstable global bending under oblique loading. To improve the energy absorption performance of tubes under oblique loads, a novel designed tube with hybrid cross section is studied in this paper by adding ribs at the bottom end of the tube. Quasi-static compression experiments of square (single-cell) tube, single-double hybrid tube, double-cell tube under three oblique loads were performed to verify the finite element model. Based on the verified finite element model, the energy absorption performance was compared between the single cell tube (SCT), double cell tube (DCT) and single-double hybrid tube (SDHT) under seven oblique loads. Results showed that the SDHT has the best energy absorption performance. The influence of the height, direction and number of the ribs on the energy absorption performance of the hybrid cross section tubes is also discussed in this paper. The hybrid cross-section tubes could get the best energy absorption performance when the direction and height of the ribs were appropriate. And the energy absorption performance could be further improved by increasing the number of the ribs to compose the multi-cell hybrid cross section tube. The results also showed that the multi-cell hybrid cross section tube is more stable than the traditional multi cell tube under oblique loads. This will promote the application of multi-cell tubes in vehicles. • The novelty hybrid cross section tubes are firstly proposed. • Single-double hybrid tube is found to have excellent energy absorption capacity under oblique loads. • The influence of the height and direction of the ribs is investigated and the appropriate height and direction is found for hybrid cross section tube. • The influence of the number of ribs is investigated to form the multi-cell hybrid cross section tubes. The result shows that the multi cell hybrid cross section tube can effectively reduce the sensitivity of the multi cell tube to oblique loads. [ABSTRACT FROM AUTHOR]

Metal/composite hybrid square tubes that combine the advantages of low-density of composite with low-cost of metal provide a potential energy absorption device for automobiles. The axial crushing performance of CFRP/aluminum hybrid square tubes wrapped with single angle-ply and antisymmetric angle-ply was studied by experimental and numerical methods. Results show that for tubes wrapped with single angle-ply [0] 4 or [45] 4 , crack propagation occurred and the CFRP separated from aluminum, which resulted in worse energy absorption capacity than pure aluminum tube. A stable symmetric deformation was observed in hybrid square tubes wrapped with antisymmetric angle-ply. The specific energy absorption (SEA) for those tubes was improved 11% and they showed better energy absorption performance compared to pure aluminum tube. Then, the effect of thickness of tubes, including hybrid square tubes with identical aluminum and hybrid square tubes with identical mass, on the energy absorption capacity was further investigated by simulation. It was found that only when the number of CFRP layer reaches a certain value, hybrid square tubes perform better than pure aluminum tube with identical mass in energy absorption. Moreover, influence of mass of the tube, and substituting aluminum alloy with CFRP on the energy absorption of hybrid square tubes with identical aluminum and different number of CFRP layers was studied. • Axial crushing performance of hybrid square tubes with single and antisymmetric angle-ply was experimentally studied. • The finite element model of hybrid square tubes was established and verified by the experimental data. • Effect of thickness of tubes with identical aluminum and that with identical mass on energy absorption was investigated. • Mass of the tube and replacing aluminum alloy by CFRP was considered in the energy absorption of hybrid square tubes. [ABSTRACT FROM AUTHOR]

Variable thickness hybrid square (VTHS) tubes which had variable thickness of CFRP to achieve the variation of axial crushing performance are proposed. To study the crushing characteristics and relative advantages of the VTHS, pure aluminum tube, uniform hybrid square tube and VTHS were manufactured firstly, and their axial crushing tests were conducted. Experimental results showed that, compared with uniform hybrid square tube, VTHS had lower initial peak crushing force. Finite element models were established and verified to explore the effect of parameters of the tubes on axial crushing performance further. Numerical results showed that the crushing force can be controlled by varying the thickness of CFRP. Compared with uniform thickness hybrid square tube, VTHS had an improvement of 24.5% in specific energy absorption and increase was greater for the VTHS with thinner metal. Effects of the mean thickness, thickness difference, and number of segments of CFRP on the energy absorption performance were studied. Finally, a theoretical model to predict the mean crushing force was proposed and its accuracy was verified by tests. Results demonstrate that theory can be used to obtain the mean crushing force of each segment of VTHS accurately. [ABSTRACT FROM AUTHOR]