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A comprehensive study of the multiscale homogenized thermal conductivities and thermomechanical properties is conducted towards the filament groups of European Advanced Superconductors (EAS) strand via the recently proposed Multiphysics Locally Exact Homogenization Theory (LEHT). The filament groups have a distinctive two-level hierarchical microstructure with a repeating pattern perpendicular to the axial direction of Nb3Sn filament. The Nb3Sn filaments are processed in a very high temperature between 600 and 700°C, while its operation temperature is extremely low, −269°C. Meanwhile, Nb3Sn may experience high heat flux due to low resistivity of Nb3Sn in the normal state. The intrinsic hierarchical microstructure of Nb3Sn filament groups and Multiphysics loading conditions make LEHT an ideal candidate to conduct the homogenized thermal conductivities and thermomechanical analysis. First, a comparison with a finite element analysis is conducted to validate effectiveness of Multiphysics LEHT and good agreement is obtained for the homogenized thermal conductivities and mechanical and thermal expansion properties. Then, the Multiphysics LEHT is applied to systematically investigate the effects of volume fraction and temperature on homogenized thermal conductivities and thermomechanical properties of Nb3Sn filaments at the microscale and mesoscale. Those homogenized properties provide a full picture for researchers or engineers to understand the Nb3Sn homogenized properties and will further facilitate the material design and application.

The bending failure mechanism and energy absorption characteristics of hybrid metal/composite structures are the keys to the side collision safety of automobiles. The purpose of this paper is to investigate the bending behavior and failure mechanism of hybrid Steel/GFRP hat‐shaped beams under three‐point bending. Firstly, both quasi‐static and dynamic three‐point bending tests were conducted on Steel, GFRP and hybrid Steel/GFRP hat‐shaped beams. Then, the effect of layups and loading speeds on the bending failure behaviors of GFRP hat‐shaped beams were investigated, and the five stages of the bending process of GFRP hat‐shaped beams were exposed. Finally, the failure mechanism of hybrid Steel/GFRP hat‐shaped beams under both quasi‐static and dynamic three‐point bending were investigated. It is found that the failure mechanism is related to the interaction effect between the Steel and GFRP parts in the hybrid Steel/GFRP hat‐shaped beam. In the bending failure process, the crack propagation in GFRP parts is delayed by the plastic deformation of the connected Steel parts, which improves the energy absorption and load carrying capacities of the hybrid Steel/GFRP hat‐shaped beam, and this improvement in the whole bending process is quantitatively exposed in this work. Besides, it is found that with the same impact energy, the load carrying capacity of the hybrid Steel/GFRP hat‐shaped beam can be increased by the loading roll diameter increasing. Highlights: A bending process with five stages of GFRP hat‐shaped beams is exposed.The loading speed increases impact loads due to the strain rate strengthening.The interaction between Steel and GFRP improves the load carrying capacity.The load carrying improvement is due to crack propagation delay in GFRP parts.The greater loading roll diameter increases the load carrying capacity. [ABSTRACT FROM AUTHOR]

The hybrid metal/GFRP laminate is a kind of typical hybrid structure consisting of thin metal sheets and glass fiber reinforced plastic laminates, which combines the benefits of low cost, high strength, excellent impact resistance, and good corrosion resistance. In this work, a semi‐experimental method based on a nondestructive test and the analytic solution of the thin plate's deflection for the flexural and sinking stiffnesses identification of hybrid metal/GFRP laminates was proposed and validated by corresponding numerical simulations. Then, in total 17 different specimens (including metal, GFRP and hybrid metal/GFRP) were prepared and tested by the proposed semi‐experimental method to investigate their flexural and sinking stiffness performances in multiple perspectives (including stiffness per unit mass/volume/price/surface density). The analytic solutions show that the flexural and sinking stiffnesses are proportional to macro equivalent moduli of laminate specimens and proportional to the third power of thicknesses of specimens. The test results show that the stiffnesses per unit mass/density of the 7‐ply GFRP laminate can be comparable to those of the variable‐thickness rolled blank (VRB) made of steels, but the stiffnesses per volume/price of the 7‐ply GFRP laminate are only one fifth to one quarter of those of VRB. It is also found that though the hybrid metal/GFRP laminate with the combination sequence of aluminum plate/5‐ply GFRP/aluminum plate has the lowest GFRP layers' volume fraction, but has the best performances of stiffnesses per unit mass/density. Besides, the VRB part can significantly improve the stiffnesses per unit volume of hybrid metal/GFRP laminates. [ABSTRACT FROM AUTHOR]

Ultra‐high‐performance cementitious composite (UHPCC) incurs higher economic costs and resource wastage due to its high cement/silica fume (SF) content. The paper aims to achieve sustainability and environmental friendliness of UHPCC by substituting cement/SF with glass powder (GP). The influence of various GP particle sizes and substitution levels on the mechanical properties of UHPCC was investigated. X‐ray diffraction and scanning electron microscopy were employed to analyze the impact of GP on the hydration process of UHPCC from a microscopic perspective. In addition, the internal damage pattern of GP‐UHPCC was simulated by the RFPA3D program. The results show that the addition of GP could achieve superior fluidity than GP‐0. Compared to conventional UHPCC, GP‐20 exhibits improved strength, initial flexural toughness, and residual flexural toughness. Furthermore, finer GP particle sizes contribute to enhanced matrix strength and flexural energy absorption capacity to some extent. Additionally, the incorporation of 5%–20% GP leads to an increase in the characteristic peaks of hydrated lime and C‐S‐H gel, which are beneficial to improving the internal microstructure of the matrix. Based on the RFPA3D program, the crack area, principal stress distribution, and acoustic emission energy of specimens with 15%–25% GP substitution levels were significantly higher than those of specimens with low substitution levels (0%–10%). Generally speaking, a GP substitution level of 15%–25% is found the most effective range for improving strength, and toughness behavior in this study. [ABSTRACT FROM AUTHOR]

In this paper, a generalised incremental stress state dependent damage model (GISSMO) is used to accurately characterise the ductile failure behaviour of hot formed steel under collision, which is the excellent material selection to improve the crashworthiness and lightweight level of car body frames. The deformation patterns, structural failure patterns, and key crashworthiness indexes of B1500HS hot-rolled tube (HRT) are validated by the comparative researches between experiments and simulations. To fully exploit the lightweight potential of HRT, a variable-thickness rolled blanks hot rolled tube (VRB-HRT) is proposed to perform its crashworthiness optimisation design with considering the ductile failure by the extended hybrid cellular automaton for VRB thin-walled structures (eHCA-VRB) algorithm. It is found that the optimal case of VRB-HRT with considering the ductile failure is easier to meet the actual performance constraints, even though possesses a lower weight reduction ratio. Therefore, the ductile failure of VRB-HRT should be considered to guarantee the structural reliability by a more reasonable optimal design. [ABSTRACT FROM AUTHOR]

After fully understanding the limitations of traditional variable rolled blank (VRB) and variable cross-sectional (VCS) double-hat shaped beam structures on the energy absorption ability and collision safety optimal design, we propose a variable rolled blank and variable cross-sectional (VRB-VCS) double-hat shaped beam structure with piecewise exponential function. Firstly, the thickness distribution function and the mathematical model of constraint conditions are derived under the constraints of manufacturing rollability. The corresponding finite element (FE) model of the VRB-VCS structure is validated by the dropping hammer impact axial crush experiments, which can predict the crushing process with high fidelity. Secondly, the parametric researches of the energy absorption characteristic of VRB-VCS structure are carried out based on the FE model. The reasonable range of each parameter is obtained by analyzing the influence of the thickness distribution and other key cross-sectional parameters on the energy absorption characteristic and deformation mode of VRB-VCS structure. Finally, the Pareto frontier solutions of the linear and piecewise exponential function VRB-VCS structures are obtained by the multi-objective optimization of the corresponding structures. In comparison to VCS, VRB and linear VRB-VCS structures, the proposed VRB-VCS structure has a higher energy absorption capacity and greater crashworthiness. [ABSTRACT FROM AUTHOR]

The energy absorption (EA) capacity of the thin-walled structures with variable cross-section shape (VCS) under axial impact loading is investigated in this work, which plays an important role in the field of vehicle lightweight and crashworthiness designs. The accuracy of numerical models is validated by the experiments of corresponding VCS specimens. We investigate the influence of structural parameters (i.e. scaling of cross-section, ratio of width to height, thickness and cross-section shape) on the deformation mode and EA capacity of the VCS structures. A good agreement is observed by the comparison between simulation results and experimental ones, which proves the effectiveness of numerical models. Finally, we find that the permutation of appropriate parameters can significantly improve the collision EA capacity of the thin-walled structures. This work will have wild engineering applications in the field of crashworthiness design of car body structures. [ABSTRACT FROM AUTHOR]

In order to investigate the impact resistance of damaged reinforced concrete (RC) beams strengthened with carbon fiber reinforced plastics (CFRP), the dynamic responses of the damaged beams under different CFRP reinforcement methods are simulated using the finite element analysis software LS-DYNA and compared with the experimental results. The analysis results of failure pattern, crack propagation pattern and dynamic history of the strengthened beams show that the U-shaped CFRP strengthened beam can significantly inhibit the development of shear diagonal cracks and greatly reduce the crack propagation range. At the first impact, compared with the un-strengthened beam, the peak impact force of the straight, U-wrapping and composite CFRP strengthened beams increased by 15. 4%, 16. 6% and 13. 1%, respectively, and the mid-span peak displacement decreased by 4. 8%, 8. 3% and 10. 1%, respectively. At the second impact, the U-wrapping and composite CFRP strengthened beams remained good impact resistance. The study can provide a reference for the optimal design of damaged RC beams strengthened with CFRP. [ABSTRACT FROM AUTHOR]