Strain Energy Absorption Research Articles

The high ductility performance of energy-absorbing buffer support materials

In order to study the realization of high ductility performance of foam fiber concrete (FFC) as energy-absorbing buffer support material, a series of samples were prepared based on the optimal mix ratio of orthogonal test. The uniaxial compression test was carried out to obtain the stress–strain curve and energy absorption curve. The strain capacity and macroscopic cracking process were revealed by digital image correlation (DIC). The mechanical performance of the admixture in the process of achieving high ductility performance was captured by scanning electron microscopy (SEM). The test results show that the average strength of FFC in the platform stage is 73.95% of the peak strength, and it can effectively absorb external energy as an energy-absorbing buffer support material. Foam, waste polystyrene particles and PVA fiber were the key factors to realize the high ductility of FFC.

Tensile strength and strain energy absorption in twist extruded Al 6061-B4Cp metal matrix composites

ABSTRACT Due to its accessibility and ease of use in various sectors, the twist extrusion method is gaining significant acceptance for improving the strength and hardness of structural components. However, only a few experiments on twist-extruded MMCs of aluminium 6061 alloy reinforced with ceramic boron carbide (B4C) particles have been reported. The development of an Al-6061 alloy reinforced with 1.5–8 weight percent B4C particles and its twist extrusion, a severe plastic deformation method, are the main subject of this work. The study aimed to investigate the influence of particles and the extrusion process on the tensile strength and specific strain energy absorption of both the matrix and the composites. It was observed that the addition of B4C particles and the extrusion process increased the hardness and tensile strength of the alloy by 29.1% and 68.3%, respectively and for the composites with 8 wt.% particles, the increases were 31.8% and 62%, respectively. However, the theoretical density, ductility and absorbed strain energy decreased by 3.97%, 35.7%, and 27.9%, respectively, for the composite with 8% B4C, compared to the extruded matrix. A microscopic study determined the ASTM grain size number, which supported the observed physical and mechanical properties of both the as-cast and twist-extruded Al 6061-B4Cp composites.

Preparation, characterisation, physical, and compression testing of sucrose based closed-cell aluminium foam

ABSTRACT Aluminium foam can be used as a porous and lightweight material having comparatively high impact energy absorption. To reduce the death rate caused by collisions of vehicles, there is a need of analysing the crash-worthiness properties of materials. In this present work, the Aluminium foam was prepared using the powder metallurgy method for the crash-worthiness analysis. The Al6061 powder as a matrix material having particle sizes ranging from 5 to 30 µm and Sucrose particles as a space-holding material were mixed. The compaction process was done up to a pressure of 450 MPa to make the green compact and was further subjected to sintering up to a temperature of 500 °C for 1 hour resulting into the Aluminium foam. The compressive strength significantly decreased by 26.56%, 51.39%, 72.49%, and 64.34% approximately while volume fractions of sucrose particles varied as 20%, 30%, 40%, and 50%. On the other hand, the measured maximum porosity was found as 51.8% approximately in the Aluminium foam corresponding to the addition of 50% sucrose particles by volume. Out of all the examined samples, the foam developed by containing 20% (vol.) sucrose has exhibited the maximum strain energy absorption, specific energy absorption (SEA), and crushing force efficiency (CFE).

Multiple impact resistance and microstructure of hybrid fiber-reinforced fly ash/slag-based geopolymers after exposure to elevated temperatures

Engineered geopolymer composites (EGC) have garnered significant attention from researchers as a new environmentally friendly building material with superior tensile properties, impact resistance, and high-temperature resistance. This study focuses on the investigation of the dynamic mechanical properties of a hybrid fiber reinforced lightweight EGC containing ceramsite (LW-EGC) after exposure to elevated temperatures and multiple impacts. The effects of temperature, steel fiber content, and ceramsite types were taken into consideration. The analysis encompassed multiple impact stress-strain curves, dynamic peak stress and strain evolution, energy absorption, damage evolution, damage morphology, and microstructure changes following exposure to elevated temperatures. The experimental results revealed a significant decrease in the number of impacts endured by LW-EGC-M as the temperature increased. After 200 °C, the LW-EGC-M experienced 15 impacts, while after 800 °C, it only endured 2 impacts. Both cumulative energy absorption and cumulative damage of LW-EGC exhibited an exponential growth pattern with an increasing number of impacts. Microstructural analysis unveiled the emergence of a new nepheline phase after exposure to elevated temperatures, while the calcite in the matrix demonstrated gradual decomposition. Moreover, elevated temperatures led to a decreased Si/Al ratio in the matrix. The complete melting of PVA fibers after exposure to elevated temperatures resulted in the production of numerous interconnected pores in the matrix, leading to a decline in the mechanical strength of LW-EGC. This phenomenon also contributed to the reduction of internal pore pressures and the release of local vapor pressure generated by elevated temperatures.

Experimental study on the cushioning energy absorption characteristics of polymer materials resistant to seawater erosion in seismic damping layers

AbstractPolymer materials exhibit vibration damping properties, yet scant research exists on their applicability to submarine tunnels. This study investigates the dynamic characteristics of Polymer Materials Resistant to Seawater Erosion (hereafter referred to as PMRSE) under varying conditions of density, confining pressure, strain rate, and erosion duration through dynamic triaxial tests. The results reveal an increase in material strength with a rise in density; enhanced strength and ductility with increasing confining pressure; and augmented strength and yield stress in correspondence with heightened strain rates. As confining pressure ascends, the equivalent damping ratio of PMRSE gradually diminishes. SEM and EDS indicate a porous structure for PMRSE, with a molded surface skin formed post‐manufacturing to thwart seawater erosion. The strain energy storage and energy absorption evaluation of PMRSE demonstrate its excellence as an energy‐absorbing material. Eventually, employing a numerical simulation model for a specific submarine tunnel reveals that the presence of a damping layer absorbs seismic energy and enhances the stress conditions of the secondary lining. PMRSE manifests as a strain‐rate sensitive material unaffected by seawater corrosion, which exhibits deformation characteristics of low yield strength and long yield stage. Accordingly, PMRSE proves suitable for vibration damping in submarine tunnels.

3D Printed Metamaterials for Energy Absorption in Motorsport Applications

In this study, various 3D printed metamaterials are investigated for application in energy absorbing structures in motorsports. Impact attenuating structures are used to decelerate vehicles and protect drivers in the event of a crash. Additive manufacturing enables complex plastic structures which can facilitate improved angular resistance and reduced weight and cost compared with traditional approaches. Metamaterials were 3D printed from PLA using commercially available equipment and include gyroid structures, a novel reinforced gyroid design and a lattice designed using finite-element analysis-based topology optimization. Compression testing was used to measure stress–strain response, compressive modulus, and energy absorption. This demonstrated gyroids and reinforced gyroids have ideal compressive behavior for high energy absorption under impact. The topology optimized metamaterial was found unsuitable for this application due to its high stiffness, revealing a weakness in traditional topology optimization approaches which are not catered to maximize energy absorption. The reinforced gyroid demonstrated the highest specific energy absorption and was used to manufacture an impact attenuator which demonstrated the potential to safely stop a hypothetical 300 kg vehicle crash. This work supports that gyroid-based structures can reduce weight, volume and cost over current materials in all motorsport categories, with improved safety from oblique crashes.

Topology optimization of smart structures to enhance the performances of vibration control and energy harvesting

Abstract With the growing interest in smart materials, the utilization of shunted piezoceramics for dynamic vibration control has gained significant attention due to their unique characteristics, such as the ability to absorb strain energy from vibrating systems and convert it into electrical energy. Designing and analyzing the behavior of structures in hybrid mitigation/harvesting conditions, considering both reliability and performance, pose challenges. This paper aims to achieve optimal design parameters for the structure by employing a multiobjective optimization approach that strikes a compromise between maximizing harvested power and minimizing structural damage. To evaluate the effectiveness of the design, topology optimization was conducted in three different cases to compare the results. By systematically exploring the design space, these cases provide insights into the influence of various parameters on the structural performance. In addition, to enhance computational efficiency, the structure was represented as a metamodel using neural networks. This approach enables rapid evaluation and prediction of the structure’s behavior, facilitating the optimization process. By integrating multiobjective optimization, topology optimization, and metamodeling techniques, this study aims to provide valuable insights into the optimal design of structures that simultaneously incorporate shunt circuitry for vibration control and energy harvesting, leading to improved performance and reliability.

Uniaxial tensile behavior of engineering cementitious composite reinforced with fiber textile grid and steel wire mesh

The Textile Reinforced Engineering Cementitious Composite (TRECC) is a cementitious composite material reinforced with short polyvinyl alcohol (PVA) or polyethylene (PE) fibers, possessing exceptional ductility. This unique attribute enhances the utilization of the textile grid’s strength and significantly improves the load-bearing and deformation capabilities of ECC members reinforced with textile grids. In this study, the effects of fiber textile grids and steel wire mesh on the tensile properties of ECC were investigated. The test results showed that the carbon textile grid significantly improved the peak strength of specimens. On the other hand, the glass textile grid significantly improved the ultimate strain of specimens. The carbon combined with glass textile grids can integrate effectively the advantages of both carbon and glass textile grids. When compared with single textile grids, the combination uses of steel wire mesh and fiber textile grids resulted in a significant improvement in ultimate strain and post-peak energy absorption values. Finally, based on the test data, this study proposed the peak strength calculation of TRECC and provided the stress–strain expressions of the initial non-linear strain hardening phase and the tensile softening phase and a related analytical model to describe the stress–strain behavior of TRECC.

Strain-hardening ultra-high performance concrete (UHPC) with hybrid steel and ultra-high molecular weight polyethylene fibers

This study addresses the advancement of strain-hardening ultra-high performance concrete (UHPC) by investigating its tensile behavior with hybrid steel and ultra-high molecular weight polyethylene fibers. Through direct tensile testing of UHPC samples with varying volumes of steel and polyethylene fibers (totaling 2.0%), significant improvements in tensile strain capacity and energy absorption capacity (tensile toughness) were observed upon replacing steel fibers with polyethylene fibers. Despite marginal variations in first cracking strength and ultimate tensile strength, these properties could be finely tuned by tailing fiber length and hybrid ratio. Quantitative analysis established correlations between the hybrid fiber factor and key mechanical properties, advancing a deeper understanding of UHPC behavior. The findings underscore the benefits of multiscale fiber hybridization in UHPC, offering scientific insights into predicting and optimizing its performance for structural applications. This study helps close the gap in UHPC development, emphasizing the potential of multiscale fiber hybridization to achieve concurrently high tensile strength and strain capacity.

Mechanical Behaviour of Photopolymer Cell-Size Graded Triply Periodic Minimal Surface Structures at Different Deformation Rates.

This study investigates how varying cell size affects the mechanical behaviour of photopolymer Triply Periodic Minimal Surfaces (TPMS) under different deformation rates. Diamond, Gyroid, and Primitive TPMS structures with spatially graded cell sizes were tested. Quasi-static experiments measured boundary forces, representing material behaviour, inertia, and deformation mechanisms. Separate studies explored the base material's behaviour and its response to strain rate, revealing a strength increase with rising strain rate. Ten compression tests identified a critical strain rate of 0.7 s-1 for "Grey Pro" material, indicating a shift in failure susceptibility. X-ray tomography, camera recording, and image correlation techniques observed cell connectivity and non-uniform deformation in TPMS structures. Regions exceeding the critical rate fractured earlier. In Primitive structures, stiffness differences caused collapse after densification of smaller cells at lower rates. The study found increasing collapse initiation stress, plateau stress, densification strain, and specific energy absorption with higher deformation rates below the critical rate for all TPMS structures. However, cell-size graded Primitive structures showed a significant reduction in plateau and specific energy absorption at a 500 mm/min rate.

Compressive mechanical properties of styrene-butadiene rubber under medium-low strain rates: Experiments and modeling

Styrene-butadiene rubber (SBR) is widely employed as a cushioning material in engineering applications to resist impact loadings due to its excellent mechanical properties and energy absorption capacity. This paper aims to investigate the compressive mechanical properties and constitutive model of SBR under medium–low strain rates both experimentally and theoretically. Firstly, quasi-static and dynamic compression tests of SBR were carried out under the strain rate up to 220 s−1 using an electronic universal testing machine and a drop-weight machine, respectively. Subsequently, the effect of loading rate on mechanical properties, strain rate sensitivity and energy absorption capacity was examined. The results indicate that SBR exhibits visco-hyperelastic characteristics with reversible compression deformation and strain rate dependency, ie., the yield stress, flow stress and dynamic increase factor (DIF) increase approximately exponentially with increasing logarithmic strain rate. In addition, the SBR exhibits excellent energy absorption capacity during compression, especially under higher strain rates and larger strain levels. Finally, a visco-hyperelastic constitutive model was proposed by replacing the nonlinear spring with a hyperelastic element in Zhu-Wang-Tang (ZWT) viscoelastic constitutive model to describe the nonlinear mechanical behaviors in SBR, and an acceptable agreement between experimental results and model predictions were observed. The findings of this research can provide a valuable guide for designing and optimizing the impact resistance of SBR structures.

Impact resistance analysis of a dual-constituent negative Poisson’s ratio lattice metamaterial with tailorable coefficient of thermal expansion

The combination of parameters such as negative Poisson’s ratio (NPR) and negative coefficient of thermal expansion (NCTE) can result in novel materials with specialized functions to meet the requirements of multifunctional and multipurpose devices. However, the additional structural design to meet NCTE requires a re-examination of its impact resistance. In this paper, the deformation modes and impact resistance of dual-constituent re-entrant hexagonal lattice metamaterial (DRHLM) with both NPR and NCTE are investigated under different impact velocities, and the nominal stress–strain curves and energy absorption characteristics of DRHLM structures with different arch heights, chord lengths, and angles of the bottom edge ribs and the diagonal ribs are discussed. The results show that the bi-material bending ribs affect the energy absorption of the structure, and in most cases the DRHLM structure has a better energy absorption capacity than the traditional concave hexagonal structure, but too much or too little curvature of the bi-material portion reduces the energy absorption characteristics of the DRHLM structure. In addition, the increase in the pinch angle of the ribs leads to the weakening of the negative Poisson’s ratio effect, which is also detrimental to the energy absorption of the structure. The work done can provide guidance for finding the dimensional parameters of DRHLM structures with optimal energy absorption performance.

Machine learning and feature representation approaches to predict stress-strain curves of additively manufactured metamaterials with varying structure and process parameters

Lattice structures, one type of mechanical metamaterials, exhibit excellent mechanical properties such as a high strength-to-weight ratio and energy absorption capacity. However, predicting the stress–strain relationship of lattice structures remains a challenge because the mechanical behaviors of additively manufactured lattices are affected by both the structure parameters of a lattice and process conditions. This study proposes a machine learning (ML)-based predictive modeling framework to predict the entire stress–strain curves, compressive modulus, and energy absorption of lattice structures with varying structure and process parameters. Feature engineering techniques are used to transform raw data into new data representations compatible with ML models, including artificial neural networks, long short-term memory (LSTM), and convolutional neural networks (CNN). Two novel feature representations, including polygons and colormaps, are developed to transform structure and process parameters from tabular format into image format for CNN. The LSTM model that predicts stress–strain curves achieves a minimum mean absolute percentage error (MAPE) of 0.147. The CNN (colormap) model achieves a minimum MAPE of 0.174 when predicting compressive modulus. The ANN and LSTM models achieve a minimum MAPE of 0.068 when predicting energy absorption. The training time to build these ML models is less than 6 min.

Development of hybrid green composites by dual natural fibers (jute/bamboo) reinforcement and investigation of their mechanical behavior

AbstractThis study aims to investigate the mechanical properties of natural fiber hybrid composites, specifically those based on jute and bamboo fibers. Jute fibers made in the form of highly scattered mesh and fine‐meshed bamboo mat were selected as reinforcing materials. The highly scattered meshed jute fabric composite showed poor mechanical properties owing to resin agglomeration, leading to the brittle fracture of the composite before elongation. In contrast, the randomly oriented fine‐meshed bamboo fabric performed better in terms of both mechanical properties and strain energy absorption under the same loading conditions. Hybridization with fine bamboo mesh fibers can be a solution to improve the mechanical properties of jute fabric composites. The tensile, flexural, and in‐plane shear properties of the composites are investigated in our study. We found that hybridizing a fine‐meshed bamboo mat with jute fabric resulted in an improved mechanical performance of the composite. Composite panels have been manufactured using vacuum assisted resin transfer molding (VARTM). Experimental and numerical methods have been used to investigate the flexural behavior. Of the stacking sequences considered, the (J/B4/J) stacking showed the highest flexural strength (141.1 Mpa) and the (B2/J2/B2) 2/2 stacking sequence showed the minimum flexural strength. The alternating stacking sequence (B/J/B/J/B/J) exhibited intermediate properties. The randomly oriented bamboo fabric near the neutral axis enhanced the properties of the hybridized composite. This was verified numerically using the ANSYS ACP software.Highlights Mechanical behavior of Hybrid composite of two natural fibers was investigated. Vacuum assisted resin transfer molding was used to manufacture composite panels. Tensile, in plane shear, 3 point flexural tests and SEM micro analysis were done. FEA was used to validate and compare the experimental and numerical results. Resin agglomeration was improved by fibers with better resin impregnation property.

Effect of conductive surface-coated polyethylene fiber on the electrical and mechanical properties of high-performance fiber-reinforced cementitious composites

This study investigated the electrical conductivity and mechanical properties of high-performance fiber-reinforced cementitious composites (HPFRCC) with conductive coated ultra-high-molecular-weight (UHMW) polyethylene (PE) fibers. The silver nanoparticles with spherical shape were coated most evenly. Despite some parts of the fiber surface being less coated with carbon nanotube (CNT) and graphite nanofiber (GNF) compared to the silver nanoparticles, they effectively increased electrical conductivity of the plain PE fiber. Both the coating degree and conductivity of the coating material affect the conductivity of PE fiber. The compressive strength of HPFRCC was not affected by conductive coating. The electrical conductivity of HPFRCC improved by 18.7%–45.1% than the control specimen, and the highest electrical conductivity was achieved when coated with silver nanoparticles. Incorporating conductive coating fibers had a negative effect on tensile strengths (18.9–23.5% decreases) but a positive effect on the ductility. The GNF-coated PE fibers led to the strain capacity and energy absorption capacity improved by 69.4 and 44.8%, respectively. Therefore, given the increase in deformation performance outweighs the decrease in tensile strength, engineered, conductive coating fibers can be used as novel reinforcement in HPFRCC to attain additional functionalities related to electrical capabilities.

Impact toughness and dynamic constitutive model of geopolymer concrete after water saturation

The dynamic compression test of geopolymer concrete (GC) before and after water saturation was carried out by the split Hopkinson pressure bar (SHPB). And the effects of water saturation and strain rate on impact toughness of GC were studied. Based on Weibull statistical damage distribution theory, the dynamic constitutive model of GC after water saturation was constructed. The results show that the dynamic peak strain and specific energy absorption of GC have strain rate strengthening effect before or after water saturation. The impact toughness of GC decreases after water saturation. The size distribution of GC fragments has fractal characteristics, and the fractal dimension of GC fragments after water saturation is smaller than that before water saturation. The dynamic constitutive model based on Weibull statistical damage distribution theory can accurately describe the impact mechanical behavior of GC after water saturation, and the model fitting curves are in good agreement with the experimental stress–strain curves.

The influence of the molecular chain length of PVA on the toughening mechanism of calcium silicate hydrates.

In recent years, polymers have been demonstrated to effectively toughen cementitious materials. However, the mechanism of interaction between the polymers and C-S-H at the nanoscale remains unclear, and the quantitative impact of the polymer chain length on toughening effectiveness is lacking in research. This study employs molecular dynamics techniques to examine the impact of the polyvinyl alcohol (PVA) chain length on the tensile performance and toughening mechanism of C-S-H. The toughening effect in both the X and Z directions exhibits an initial enhancement followed by a decline with increasing chain length. The optimal degrees of polymerization are determined to be 8 and 12 in the X and Z directions, respectively, resulting in an improvement of fracture energy by 146.7% and 29.5%, respectively. During the stretching process along the X and Z axes, the chain length of PVA molecules significantly influences the variation in the number of Ca⋯O bonds in the system, leading to different stress responses. Additionally, PVA molecules form C-O-Si bonds with the silicate layers of C-S-H, bridging the adjacent layers in a left-right or up-down manner. The toughening effect of PVA on C-S-H depends on the behavior of PVA molecules with different chain lengths, and there exists an optimal range of chain length for PVA, enabling it to enhance structural uniformity and adjust its own conformation to absorb strain energy. When the length of PVA molecular chains is too short, it can easily cause stress concentration in the system and its connection with silicates is not significant. Conversely, when the length of PVA molecular chains is too long, the large molecular structure restricts its extension in the defects of C-S-H, and as the stretching progresses, PVA molecules break and form numerous small segments, thereby losing the advantage of the chain length. This study provides a theoretical basis for the ability of polymers to toughen cementitious materials.

A high-performance design of tubular lattice structure having zero Poisson’s ratio

In this work, novel zero Poisson’s ratio (ZPR) tubular lattice structures, named as strut-reinforced semi-reentrant honeycomb (SR-SRH), were designed. Finite element simulations of quasi-static compression were conducted, and Design of Experiments (DoE) technique was used to study the effects of geometric parameters of the tubular lattices on the mechanical properties. One of the proposed designs of SR-SRH tubular lattices (SR-SRH-1) exhibited remarkably higher ZPR strain limit and energy absorption ability compared to previously studied ZPR tubular lattices. Another design (SR-SRH-2) demonstrated excellent compressive strength and elastic modulus. These 3D-printed structures were tested under quasi-static compression to corroborate the numerical simulations.

The role of flexible polymer composite materials properties in energy absorption of three-dimensional auxetic lattice structures

In this work, the ability of lattice structures with 3D periodic auxetic structure to absorb energy have been investigated. The lattice structures were printed using the FDM method from five types of filaments characterized by different strength, plasticity, and viscoelasticity ratios. The mechanical properties of the filaments were determined by tensile, hardness and impact tests. Quasi-static cyclic tests were used to investigate the viscoelastic behavior. The energy absorption ability of lattice structures was determined by compression tests. It has been established that TPU and nylon fibers are inferior to PLA filaments in terms of strength and hardness, but significantly surpass them in terms of the ability to withstand shock loads and damping properties. Significant differences in the mechanisms of strain energy absorption depending on the properties of the initial filaments have been demonstrated. PLA stuctures exhibit high energy values (0.06 – 0.12 J/cm3), but they are brittle and unable to recover their shape. TPU filaments provide the ability to restore shape, but absorb significantly less energy (0.011 J/cm3). Nylon fibers are less durable than PLA, but have a higher absorption energy (0.136 J/cm3) and are more prone to shape recovery. In further optimization of the structure and properties of 3D structures, it is advisable to use combined lattices consisting of materials with different plasticity and damping ability, which is proposed to be combined by mechanical behavior.

On the interactions of carbon nanotubes with metakaolin cementitious binders: Effects on ITZ, modulus and toughness

The addition of metakaolin (MK) in cementitious composites leads to a considerable improvement in compressive strength; yet negligible increases in flexural strength and toughness are observed. This research investigates the effect of carbon nanotubes (CNTs) on the tensile load carrying capacity and strain energy absorption capability of metakaolin based cementitious composites at the elastic and post-crack stages, and the microstructure and chemical composition of the Interfacial Transition Zone (ITZ) between the nanomodified cementitious matrix and aggregates. The addition of 0.1 wt% CNTs in 20% MK mortars significantly increases the nanocomposites’ flexural strength and Young’s modulus by 88% and 107%, respectively. An exceptional improvement in the tensile strain energy absorption capacity of the CNT reinforced MK cementitious composites is indicated by the 1.8x higher post-crack flexural toughness and 45–110% increased toughness indices I5, I10 and I20. Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM/EDS) analysis of the ITZ of nanoreinforced MK cementitious mixes showed that CNTs at amounts as low as 0.1 wt% decreased the Ca/Si ratio of the Calcium Silicate Hydrate (CSH) products in the ITZ and increased the polymerization of the silicate chain within CSH. Therefore, addition of CNTs in MK cementitious mixes strengthens the ITZ, and greatly improves the tensile strength and modulus, and post crack ductility.