High Energy Absorption Capacity Research Articles

Mechanical properties of hybrid metamaterial with auxetic chiral cellular structure and silicon filler

Hybrid metamaterial with auxetic cellular structure and silicon filler was manufactured and mechanically tested for the first time with aim to study its enhanced mechanical properties. The uniform and graded base specimens with auxetic chiral cellular structure were fabricated from copper alloy using the Selective Electron Beam Melting (SEBM) method. The fabricated specimens were then fully infiltrated with silicone filler under vacuum conditions to avoid any voids (air gaps) and to achieve a high degree of homogeneity in the composite structure. The mechanical behaviour of hybrid specimens under quasi-static and dynamic compressive loading conditions was investigated experimentally. The results show that hybrid specimens with auxetic cellular structure and silicon filler exhibit much better mechanical response with increased stiffness and smooth response in comparison to specimens with conventional (non-hybrid) auxetic cellular structure. They also have a higher plateau stress but lower densification strain and possess much higher energy absorption capacity in comparison to the base specimens with chiral auxetic structure. This is attributed to the interaction between the filler and the structure, which results in the improvement of the macroscopic mechanical properties.

Crashworthiness design of self-similar graded honeycomb-filled composite circular structures

Lightweight cellular materials can effectively improve the crashworthiness of thin-walled structure. To further investigate the potential of honeycomb-filled composite structures, an innovative self-similar graded honeycomb-filled thin-walled structure is proposed in this paper. First, the numerical model of the self-similar graded honeycomb-filled circular tube (SGHCT) is established in ABAQUS and then is validated via the existing experiment. To systematically study the bending behavior of this novel structure, eight kinds of SGHCT with different graded patterns are designed and compared with uniform honeycomb-filled circular tube (UHCT). Through parametric study, we find that the novel structure exhibits better energy absorption characteristics than the corresponding UHCT. In addition, various parameters like thickness, mass ratio and yield stress of column wall have a considerable effect on the crashworthiness performance of this innovative structure. Furthermore, the bending behaviors of effective SGHCT are also investigated to increase the weight efficiency. Finally, the SGHT and UHCT are optimized by adopting the non-dominated sorting genetic algorithm II (NSGA-II) and Kriging modeling technique. The optimization results show that the SGHCTs show superior Pareto solutions to the uniform honeycomb-filled tubes, also better crashworthiness than foam-filled tubes under high PCF conditions in the previous researches. Especially, the specific energy absorption of ascending single-direction self-similar tube increases from 1.17 kJ/kg to 1.74 kJ/kg by 48.9%. The findings of this study offer a new route of designing novel crashworthiness structure with high energy absorption capacity.

Effect of steel coupling beam on the seismic reliability and R-factor of box-type buildings

In reinforced concrete structures comprising box-type (tunnel form) structural systems, although the link beams (LBs) experience heavy damage before the shear walls, dimensional and cross-sectional limitations make it challenging to design LBs as seismic fuses. In this study, replaceable steel coupling beams were considered as an alternative to concrete LBs and the seismic performance, seismic reliability and multi-level response modification factor of this new system was examined. The results showed that the steel LBs had considerable effects on the lateral stiffness and load-bearing capacity of the box-type structural system. Under design and maximum credible earthquakes, the steel LBs had less influence on the performance level of the structural walls, which are the main elements of the lateral-load-bearing system. Consequently, they will slightly reduce the seismic reliability of the system while achieving predetermined performance levels. The use of steel LBs is suggested due to their replaceability and high energy-absorbing capacity.

In-plane crashworthiness of re-entrant hierarchical honeycombs with negative Poisson’s ratio

Both auxetic structures and hierarchical honeycombs are marked with lightweight and excellent mechanical properties. Here, we combine the characteristics of auxetic structures and hierarchical honeycombs, and propose two re-entrant hierarchical honeycombs constructed by replacing the cell walls of re-entrant honeycombs with regular hexagon substructure (RHH) and equilateral triangle substructure (RHT). The honeycombs are subjected to in-plane impact in order to investigate the crashworthiness by using the commercial software LS-DYNA. The plateau stress of RHH and RHT in x and y directions are derived by a two-scale method. The results from numerical simulation indicate that the specific energy absorption of RHT and RHH is improved by up to 292% and 105%. RHT and RHH improve the mean crushing force value by 298%, 108% respectively compared with the classic re-entrant honeycomb (RH) under quasi-static loading at stress plateau region. The RHT and RHH still have the characteristic of negative Poisson’s ratio. Additionally, the parametric studies are further carried out to investigate the effects of impact velocities and relative densities on crashworthiness. All the findings of this study indicate that the proposed two hierarchical honeycombs exhibit an improved crushing performance, and RHT provides the highest energy absorption capacity among all specimens.

High-Performance Impact-Resistant Concrete Mixture for Transportation Infrastructure Applications

Engineered cementitious composites (ECC) is a class of high-performance fiber-reinforced cementitious composites featuring metal-like strain-hardening behavior under tension and high ductility. The highly ductile behavior of ECC often results in high impact resistance and energy absorption capacity, which make ECC suitable for applications in structures that are prone to impact damages, like exterior bridge girders, bridge piers, and crash barriers. In a recent study, a new ECC mixture has been developed using domestically available polyvinyl alcohol (PVA) fibers and regular river sand in replacement of imported PVA fibers and fine silica sand that are normally used in other ECC mixtures. The newly developed mixture, with improved local accessibility of raw materials, enables structural-scale applications of ECC in transportation infrastructures. To evaluate the suitability of the mixture for impact-resistant structures, in this paper, the tensile and flexural behavior of the newly developed material were characterized under pseudo-static loading and high strain-rate loadings up to 10−1 s−1. Direct drop-weight impact test was also conducted to assess the impact resistance and energy absorption capacity of the material. It was ensured that the ECC mixture maintains high tensile strain capacity above 1.8% under all tested strain rates. Regarding the damage characteristics, energy absorption capacity and load-bearing capacity during repeated impact loadings, ECC was found to have 75% higher energy dissipation capacity compared with regular reinforced concrete specimens and superior damage tolerance. The research results demonstrated that the newly developed ECC has a great potential to improve the impact resistance of transportation infrastructures.

Effect of Fiber Mat Density and Crushing Mechanism on the Energy Absorption Capacity of GFRP Crashworthy Tubes

The aim of this study is to examine the effect of fiber mat’s density and deformation mechanism of tubes with and without die compression. In this study a new mode of deformation mechanism of density graded GFRP circular tube is examined when they are subjected to axial compression on to a die and without die to examine its energy absorbing capacity. Theoretical calculations were made to predict the crushing stress of different specimens. It is observed that increasing density of fiber increases energy absorption value but decreases the specific energy absorption and the die could trigger progressive crushing additionally decreasing peak load. Here the compressed tube wall is compelled to be deformed towards the end of compression die with a little range of bending curvature which was forced by the radius of the die at high crushing stress and the major part of the deformation takes place at a nearly constant load, which leads to high energy absorption capacity. Comparison between theoretical prediction values by derived equations and the experimental results shows good correlation.

Experimental and numerical investigation of an innovative buckling-restrained fuse under cyclic loading

Structural fuses are sacrificial elements embedded in the structural members to localize potential failures within themselves. These replaceable segments are used to dissipate the energy of severe loads while preserving the integrity of the structure's major components. This paper presents an innovative Composite Buckling Restrained Fuse (CBRF) as a segment of a bracing element. CBRF with relatively small dimensions is a hysteretic damper with different performance in tension and compression. According to the typical difference of the bracing element capacities in tension and compression, the CBRF possess higher tensile strength than its compressive capacity. Utilizing tensile-only elements in this fuse with a new configuration improves the efficiency of the energy dissipation and eliminates the limitation of the tensile strength that exists in bracing members which contain ordinary ones. Key design parameters such as cross-sectional area and length of the fuse core are discussed theoretically. Six CBRF specimens with various dimensions and tensile-only elements were designed, tested and numerically modeled under cyclic loading to provide better insight into the fuse core and the encasing performance. The results indicated that the proposed structural fuse has a ductile behavior with maximum average core strain of 5.6% and sufficient tensile strength along with high energy absorption capacity.

Dynamic compressive behaviour and microstructural evolution of extrusion-shear Mg–6Zn–1Cu–1Y–0.6Zr alloy

ABSTRACTIn this work, the alloy Mg–6Zn–1Cu–1Y–0.6Zr was prepared using an extrusion-shear method, which combines traditional extrusion with the equal channel angular pressing. Dynamic compressive behaviour and microstructural evolution were studied along the extrusion direction with strain rates in the range of 695–1995 s−1 using a Split-Hopkinson pressure bar. The dynamic compression properties have a distinct positive strain rate strengthening effect. A texture transition from ⟨10–10⟩ into ⟨0001⟩ is found in the Mg–6Zn–1Cu–1Y–0.6Zr alloy. Analysis of the microstructural evolution shows that {10–12} extension twinning and (0002) basal-type slip are major deformation mechanisms. The absorption energy density dramatically increases as the strain rate increases, results indicate that dynamic recrystallisation and high yield strength are mainly responsible for the high energy absorption capacity.

Circular steel tubes filled with rubberised concrete under combined loading

The research on rubberised concrete (RuC) could promote the recycling of end-of-life tyres and reduce natural resource extraction. To mitigate the greatly reduced compressive strength and fully utilise the desirable characteristics such as improved ductility and energy absorption of RuC, confinement through a steel outer tube could be adopted. This paper investigated the effect of using circular steel tube as confinement of the RuC under axial, flexural and combined loading conditions. A total of 4 circular hollow tube sections with d/t (depth/thickness) ranging from 18 to 36 was used in this study. Three rubber replacement ratios (0%, 15%, 30%) by mass of the total aggregates were examined, along with 4 load eccentricities (0, 0.25d, 0.5d and bending) used to construct the interaction diagrams. As a result of the steel confinement, the difference in load capacity between RuC and normal concrete significantly reduced compared to the plain concretes. Additionally, RuC filled steel tube (RuCFST) members were more ductile than their normal concrete counterparts. The circular cross-section showed superior load carrying capacities compared to the square sections, due to a relatively uniform stress distribution in the cross-section. The interaction diagrams of RuCFST members could be reasonably predicted in terms of accuracy and safety of design. The tested moment capacity of RuCFST also greatly exceed the predicted values. This study has demonstrated the possibility of using RuCFST in applications where high energy absorption and ductility capacities were sought, for example, the structural members in seismic regions and flexible roadside barriers.

Structure-property relationship in high strength and lightweight AlSi10Mg microlattices fabricated by selective laser melting

Aluminum alloy microlattices have been increasingly used in automotive, aerospace, packaging, defense, machinery, and construction industries due to their superior physical and mechanical properties such as high specific strength and energy absorption capacity. However, design and fabrication of microlattice structures remains a challenge because the structure-property relationship in aluminum microlattices has not been established. To address this issue, AlSi10Mg microlattices with different unit cell structures, number of unit cells, and strut diameters were designed and then fabricated by selective laser melting (SLM). The specific energy, compressive strength, and failure modes of the AlSi10Mg microlattices were examined. Experimental results have shown that the AlSi10Mg microlattices fabricated by SLM exhibited a maximum specific compressive strength of 83.113 MPa·g−1 cm3, which is higher than most metallic and non-metallic microlattices reported in the literature. During compression tests, four different failure modes, including contact region crushing, consecutive diagonal cracks at 45° to the loading direction, elastic/plastic buckling and plastic deformation, and single diagonal crack at 45° to the loading direction, were observed. In addition, the microlattices with different unit cells exhibited different strength-density relationships due to these different failure modes.

Investigating the analytical and experimental performance of a pure torsional yielding damper

A new yielding damper with pure torsional mechanism is introduced and investigated in this paper. Story shear force is transferred to the proposed device using special details to produce pure torsion without shear force and bending moment in the damper pipes. Hence, energy dissipation capacity of damper material could be efficiently used. Some relationships for structural characteristics of the proposed damper including initial stiffness, yielding and ultimate strength and load-displacement relation, are derived analytically. This is done by assuming a bi-linear curve for steel material considering its strain hardening. Ten specimens of this pure torsional damper were tested under cyclic loading. The hysteresis curves indicate a stable and well-shaped cyclic behavior. Results also show high energy absorption capacity and ductility for this damper. Widespread yielding and uniform stress distribution across the entire thickness of the pipe wall of the damper results in high equivalent viscous damping ratio from 38% to 48%. The structural characteristics of the tested specimens were compared with analytical relationships. In addition, a parametric study was conducted based on the analytical equations.

Ti3Sn-NiTi Syntactic Foams with Extremely High Specific Strength and Damping Capacity Fabricated by Pressure Melt Infiltration.

NiTi shape-memory alloy foams have attracted much attention due to their unique superelasticity, excellent mechanical properties, and damping capacities, but their high-temperature damping capacity and compressive strength remain to be a challenge. Herein, we demonstrate the preparation of Ti3Sn-NiTi syntactic foams using Ti58Ni34Sn8 alloy and alumina microspheres by novel pressure melt infiltration and air-cooling strategies. The syntactic foams with 45% porosity contain spherical and well-distributed pores of average size 500-600 μm. A fine lamellar Ti3Sn/NiTi eutectic with an interspacing distance of 600-900 nm and a Ti2Ni interfacial layer of 10 μm thickness were formed between the alumina microspheres and the matrix. The syntactic foams achieved a high specific compressive strength (110.2-110.8 MPa cm3/g) at a wide temperature range because of the large interfacial area and good lattice strain matching in the lamellar Ti3Sn/NiTi. They also exhibited 2% recoverable strain and high specific energy absorption capacity (31.5 kJ/kg). Moreover, the foams showed ultrahigh damping capacity (0.066) at a temperature range of -150 to 200 °C. Most interestingly, the Ti3Sn-NiTi syntactic foams showed the highest comprehensive coefficient, (σ/ρ)·tan δ, of 5.07 to date. Because of these impressive features, Ti3Sn-NiTi syntactic foams become a promising material for energy absorption and damping applications.

Crushing behaviors of hierarchical sandwich-walled columns

Hierarchical structures have better mechanical properties as a widely observed organization form in nature. In this paper, a series of sandwich-walled columns (SWCs) with different sandwich cells are proposed based on hierarchical route for obtaining more weight-effective protective structures. The finite element model is firstly validated via experiment testing. Then, the crushing behaviors of SWCs, regular multi-cell columns (MCs) and single-cell column (SC) under axial load are analyzed. The results show that the hierarchical sandwich design has more remarkable potential to improve mechanical behavior than regular multi-cell design, and the effect of hierarchical level N is significant for the mechanical properties. Next, the theoretical models of mean crushing force (Fm), specific energy absorption (SEA) are derived to deeply analyze the collapsing mechanism of the SWCs, and the low errors of the theoretical predictions indicate their high accuracy. Furthermore, the technique for ordering preferences by similarity to ideal solution (TOPSIS) evaluates the crashworthiness performances of all thin-walled structures, the square sandwich cell with N = 6 (S-6) is selected because of its ideal cross-section, and the wall thickness range for optimal crashworthiness in feasible design space is identified. This study offers a novel idea of designing lightweight structure with high energy absorption capacity for the crashworthy requirement.

Comparative analysis of blast response of cable truss and cable net façades

This paper presents the development and application of comprehensive numerical modelling techniques to simulate the blast response of cable supported façades (CSFs) and compares the responses of cable truss and cable net façades which are two popular types. The results of the comparative analysis are used to evaluate the influence of the façade type on the key response parameters and hence their effective performance under blast loads. Modelling approaches, material models and constraint types used are presented along with the validation of the procedure. Results from numerical models created in LS DYNA are compared with existing numerical and experimental results from literature to validate the modelling techniques. Behaviour of cable net and cable truss façades under a credible blast event are then compared by analysing the effects of cable and panel configurations. The findings of the comparative analysis, show that cable truss façades (in general) have reduced deflections and higher energy absorption capacities, but with larger cable forces. This information can be used in the design of either façade type to obtain the desired blast response. The numerical modelling techniques developed in this paper deliver important information on the blast response and failure assessment of cable supported façades and the comparative analysis will provide guidance in future research and investigation to enable safer designs.

Rock support in strainburst-prone ground

Strainburst is the most frequently encountered type of rockburst in underground mines. Strainburst occurs when the stress near the excavation boundary reaches the peak strength of the rock mass causing it to fail suddenly and violently. To mitigate strainburst damage risk, effective rock support is needed. In strainburst-prone grounds, it is critical to have rock support components to fulfill the role of rock reinforcement first to prevent rock failure. On the other hand, well-retained and reinforced rock masses may be excessively deformed and fail violently. In such a case, yielding elements are needed in the rock support system to absorb the excess strain energy released due to rock failure. The conventional method to support strainburst-prone grounds is to install rock reinforcement system using rebar and mesh first and then install yielding support system using dynamic rockbolts at a later stage. This two-stage rock support installation process is not effective because it can adversely impact mine production schedule. This paper presents a new, patented dynamic rockbolt, which is called superbolt and is developed for rock support in burst-prone grounds. Laboratory testing confirmed that the superbolt has superb capacity to achieve the goal of reinforcing and holding rock masses. The superbolt is characterized by high dynamic energy absorption capacity, consistent performance, and the ability to withstand repeated dynamic loading. The new rockbolt can be used in a one-pass rock support system to facilitate rapid drift development in underground mines and increase mine safety and productivity.

Development of two new rockbolts for safe and rapid tunneling in burst-prone ground

Strainbursts are the most frequently encountered rockburst in underground mines. Conventional approach to support strainburst-prone ground is to install rock reinforcement system using rebar and wire mesh first and then install yielding support system using dynamic rockbolts at a later stage. This two-stage rock support installation process is not safe and effective because it can adversely impact worker’s safety and mine production schedule.Two new patented dynamic rockbolts for reinforcing and holding rock masses, which are called Superbolts, were developed for safe and rapid tunneling in burst-prone grounds. Laboratory testing was conducted to confirm the design. The new rockbolts are characterized by high reinforcement load capacity, high shear resistance capacity, high dynamic energy absorption capacity, and the ability to withstand repeated dynamic loadings. The new rockbolts can be used in cost-effective support systems in burst-prone grounds. Most importantly, they are quick to install and can be used in a one-pass rock support system to facilitate safe and rapid tunnel development in underground mines and increase mine safety and productivity.

Cycloparaphenylene crystals: Packed carbon nanorings for energy absorption and thermal insulation

Cycloparaphenylene (CPP) crystals comprising of molecular carbon nanorings are a unique class of carbon-based nanomaterials possessing inimitable properties. Based on molecular dynamics simulations and density functional theory calculations, the mechanical and thermal properties of CPP crystals are investigated in the present study. Our results show that CPP crystals possess an ultrahigh energy absorption capacity, an ultralow thermal conductivity and an ultralight weight simultaneously, which can be attributed to their intrinsically porous lattice structures and also the nanoscale dimension of their component nanoring cells. Such unique coexistence of high energy absorption and thermal insulation capacities in CPP crystals makes them more appealing in some extreme environment applications when compared to most existing engineering materials. Moreover, the energy absorption capacity and thermal conductivity of CPP crystals are also found to strongly depend on the cell size and packing mode of their component CPP molecules. The high tunability of the energy absorption capacity and thermal conductivity observed in CPP crystals raises the potential to design them for specific application requirements.

Experimental Investigation into the Energy Absorption of Composite-metal Tubes Subjected to Lateral Load

This paper studies the flattening process of empty and polyurethane foam-filled composite-metal tubes, experimentally. To prepare these specimens, metal tubes were wrapped with a fiber-reinforced composite using hand layup method. For the metal tubes, two kinds of materials, aluminum and brass, were used, and the composite tubes were made of woven E-glass fiber and vinyl ester resin. A composite tube and a metal tube were tested to compare their flattening process with the results of composite-metal tubes. The specimens were laterally compressed between two rigid plates in quasi-static condition. According to the results, specific absorbed energy (SAE: absorbed energy to the specimen mass) by a studied composite tube is about 1.5 times bigger than the SAE by the metal tubes. However, the deformation mode of the metal tube is more regular than the composite tube. So, in composite-metal tubes, the metal part causes regularity in deformation, and the composite part causes higher energy absorption capacity and lower density at the same time. Finally, the effects of some parameters such as the tubes length, foam-filler, foam adhesion, and density on the energy absorption characteristics of composite-metal tubes are studied. The results indicate that wrapping the metal tubes by composite materials causes more regularity in deformation, higher energy absorption capacity, and lower density, simultaneously.

Numerical study of low-speed impact response of sandwich panel with tube filled honeycomb core

Sandwich panel with Honeycomb Filled with Circular Tubes (HFCT) as core is numerically investigated by using ABAQUS/Explicit in this study. To calibrate the numerical model, the panels equipped with conventional hexagon honeycomb cores are modeled. Good agreement between numerical and experimental results is achieved. The sandwich panels with HFCT are compared with the sandwich panels with Honeycomb and Multi-tube cores of identical mass subjected to vertical and oblique impacts. The maximum displacement of face-sheets, plastic energy absorption, boundary reaction forces and impact load time history are calculated to assess the impact resistant capacity. The panel with HFCT core has smaller rear face-sheet displacement and higher energy absorption capacity as compared to the panels with the Multi-tube and Honeycomb core. Under oblique impact, both HFCT and Multi-tube panels have superior impact resistant capacity than the Honeycomb panel. In addition, the impact resistances of four types of multi-arc tube filled Honeycomb (HFMT) are also analysed. Their performances under vertical and oblique impacts are compared with those of HFCT.

Impact Response of Novel Fibre-Reinforced Grouted Aggregate Rubberized Concrete

The consumption of waste tyre rubber in concrete is considered to be a critical factor addressing environmental issues and sustainability. Rubberized concrete is a novel building material that poses high energy absorption capacity compared to normal concrete and finds many applications in civilian infrastructures. The concept of impact strength of fibre-reinforced grouted aggregate rubberized concrete (FRGARC) has been pioneered in this study. In the fabrication of FRGARC, combination of steel fibres and treated rubber aggregates was placed in the formwork, and then, a flowable grout was injected to fill the voids. The rubber used in this experiment was pre-treated by immersing in water with 10% NaOH solution for a time period of 0.5 h. The variables examined in this investigation are crumbed rubber aggregate replacement ratios of 5%, 10%, 15%, 20%, 25% and 30% with three different water/binder ratios (0.45, 0.50 and 0.55). Hooked-end steel fibres were used at a constant dosage of 0.5% volume of concrete. The density reduction factor, compressive strength (CS), number of impact that induced initial crack and failure, initial crack and failure energy increasing factor of FRGARC were studied. Linear and power regression equations were developed to assess the density reduction factor and initial crack and failure energy increasing factor. FRGARC exhibits reduction in CS with increasing rubber content, and it significantly contributes to the enhancement of initial crack and failure impact energy absorption capacity.