Increase In Energy Absorption Research Articles

Toxicogenetic, biochemical, and physiological effects of azoxystrobin and carbendazim fungicides over Lactuca sativa L. and Phaseolus vulgaris L.

Fungicides are pesticides that are frequently used in agriculture because of their action against fungal diseases. However, the widespread application of pesticides around the world raises environmental and public health concerns, since these compounds are toxic and can pose risks to ecosystems and human health. The aim of this study was to evaluate the phytotoxic, cytogenotoxic, and biochemical effects of azoxystrobin and carbendazim on Lactuca sativa L. and their physiological effects on Phaseolus vulgaris L. by analyzing the cell cycle and chromosomal and nuclear alterations in L. sativa; the biochemical effects of azoxystrobin and carbendazim on Phaseolus vulgaris L. and their physiological effects on Phaseolus vulgaris L. by analyzing the cell cycle and chromosomal and nuclear alterations in L. sativa; the biochemical effects by analyzing the activity of antioxidant enzymes in L. sativa; and the physiological effects by analyzing chlorophyll content and chlorophyll a fluorescence in P. vulgaris. It was observed that both fungicides were phytotoxic and cytotoxic, reducing root growth and the mitotic index, cytogenotoxic, increasing the occurrence of chromosomal alterations, as well as inducing oxidative stress and an increase in chlorophyll fluorescence emission and altered energy absorption in the plants used as a test system. In view of this, studies such as the one presented here indicate that the use of pesticides, even in small quantities, can lead to damage to the metabolism of plant organisms.

Crashworthiness Analysis of Bio-Inspired Fractal Plant Stems Multi-Cell Circular Tubes

A novel structure resembling plant stems, termed bio-inspired fractal plant stems multi-cellular circular tubes (BFPMC), was developed by incorporating fractal plant stem characteristics into smaller circular tubes within larger ones. The crashworthiness of this structure under axial impact was investigated using a validated LS-DYNA finite element model. The energy absorption performance of BFPMC tubes, varying in the number of branches, fractal orders, and inner circular diameters, was numerically studied. The numerical findings reveal a 19.27% increase in specific energy absorption (SEA) for BFPMC with [Formula: see text][Formula: see text]mm compared to [Formula: see text][Formula: see text]mm, indicating that filling a single circular tube can enhance the structure’s impact resistance. Subsequently, structural parameters conducive to excellent energy absorption characteristics were determined for various combinations of a number of branches, fractal order, and inner circle diameter parameters. These results offer valuable insights for designing multi-cellular double tubes with high energy absorption efficiency.

Mechanical properties and regulatory strategy of twinned tetrahedral lattice structures

Given the outstanding mechanical performance of lattice metamaterials, novel structural forms and performance modulation strategies have garnered considerable attention. Herein, we develop a twined tetrahedral lattice structure (TTL) with a bending defect inside the unit cell. Mechanical properties before and after the introduction of defects in TTLs were studied using experiments and numerical simulations. The developed structure exhibits strictly stretching-dominated properties in the absence of bending defects. Whereas, the bending-dominant component of TTLs is elevated with increasing bending angle that can increase energy absorption efficiency. Moreover, the relative elastic modulus and initial peak stress can be reduced by even more than 70 % and 50 %, respectively, as the bending angle increases. Besides, a theoretical model for the relative elastic modulus of TTL at θ = 0° was established based on the displacement method on the Representative Volume Element (RVE), including both Euler-Bernoulli beam theory and Timoshenko beam theory. However, the two solutions show consistent results for strictly stretching-dominated structures. The accuracy of solutions is verified by experiments and simulations. The plateau stress theoretical model for TTLs was derived from the deformation process of the RVE based on plastic hinge theory. The theoretical solutions under different θ align well with numerical and experimental results. Overall, TTLs have superior relative elastic modulus, relative yield strength, and specific energy absorption compared to common lattice structures. The developed TTLs provide a new perspective on the property regulation of mechanical metamaterials.

Steel/plastic-steel hybrid fiber UHPC dynamic tensile performance: An experimental and numerical simulation study

Steel fibers (ST) in Ultra-high performance concrete (UHPC) play an important role in enhancing its mechanical strength and toughness. However, the brittleness of UHPC increases significantly under dynamic loading, while the contribution of ST to its tensile strength and fracture mode is relatively limited. In this study, Ultra-high performance hybrid fiber reinforced concrete (UHP-HFRC) was prepared using four hybrid ratios of ST and plastic steel fibers (high-performance polypropylene, PSF), and a series of quasi-static and dynamic splitting tests were conducted to investigate the effect of PSF on its dynamic tensile behavior. Additionally, X-ray computed tomography (X-CT) and SEM characterization techniques were applied to reveal the fiber synergy effect and enhancement mechanisms from the perspective of microcrack development. In addition, a novel hybrid fiber modeling method is proposed for finite element simulation of the dynamic tensile response of UHP-HFRC. The results indicate that fiber hybridization reduces the degree of damage of UHPC under dynamic loading, and its contribution is influenced by the strain rate. The increase in steel fiber content increases the dynamic tensile strength of UHP-HFRC, but the increase in PSF content contributes to the increase in energy absorption at fracture, and it is recommended to use 1 % of PSF mixed with ST. The simulation results show the constitutive relationships and failure modes that agree with the impact test results, verifying that the proposed three-dimensional mesoscopic model can effectively analyze the dynamic splitting performance of UHP-HFRC.

Impact Performance of 3D Orthogonal Woven Composites: A Finite Element Study on Structural Parameters

This study uses the finite element method (FEM) to investigate the effect of key structural parameters on the impact resistance of E-glass 3D orthogonal woven (3DOW) composites subjected to low-velocity impact. These structural parameters include the number of y-yarn layers, the path of the binder yarn (z-yarn), and the density of the x-yarn. Using ABAQUS, yarn-level finite element (FE) models are created based on the measured geometrical parameters and validated for energy absorption and damage behavior from experimental data gathered from the previous study. The results from finite element analysis (FEA) indicate that the x-yarn density and the binder path substantially influenced the composites’ damage behavior and impact performance. Increasing x-yarn density in 3DOW leads to a 15% increase in energy absorption compared to models with reduced x-yarn densities. Moreover, as the x-yarn density increases, crack lengths at the back face of the resin matrix decrease in the y-yarn direction but increase in the x-yarn direction. The basket weave structure absorbs less energy than plain and 2 × 1 twill structures due to the less constrained weft primary yarns. These results underscore the importance of these structural parameters in optimizing 3DOW composite for better impact performance, providing valuable insights for the design of advanced composite structures.

Enhancing the flexural performance of concrete beams with 3D-printed UHP-SHCC permanent formwork via graded fiber volume fraction

Conventional concrete structures often rely on labor-intensive and wasteful formwork systems. In contrast, 3D concrete printing (3DCP) technology offers a more efficient alternative for fabricating complex-shaped permanent formwork. This study fabricates innovative composite beams using 3D-printed ultra-high-performance strain-hardening cementitious composites (UHP-SHCC) as permanent formwork, followed by casting infill materials. The spatially tailored fiber dosage distribution in the 3D-printed UHP-SHCC permanent formwork enables the performance optimization of the composite beam. The flexural behavior of three such formed composite beams is evaluated using four-point bending tests. A reference beam with homogeneous fiber distribution in the UHP-SHCC formwork is also tested for comparison. The failure mode, overall load–displacement response, and cracking performance of four beams are comprehensively characterized and compared. The results reveal that employing graded fiber dosages in UHP-SHCC formwork enhances fiber efficiency and structural performance while reducing fiber usage and material costs. The use of 3D-printed UHP-SHCC formwork with graded fiber distribution, despite using 25% less fibers and reducing the material cost by 12.8%, leads to a 65.6% increase in strength and over 50% increase in energy absorption, or a 77.4% increase in ultimate displacement with comparable peak load to the reference beam with homogeneous fiber distribution.

Mechanical and piezoresistive performance of additively manufactured carbon fiber/PA12 hybrid honeycombs

This study investigates a novel self-sensing honeycomb composite structure composed of two distinct cellular layers with differing unit cell architectures, specifically hexagonal and re-entrant designs. Short carbon fiber (CF)/polyamide 12 (PA12) composite filaments with 0, 5 or 15 wt.% CF content were utilized to additively manufacture the honeycomb structures via Fused Filament Fabrication (FFF), and their mechanical and piezoresistive self-sensing characteristics were experimentally investigated under quasi-static in-plane and out-of-plane compression at both room temperature and elevated temperatures. The results reveal that the hybrid hexagonal/re-entrant (HR) honeycombs mechanically outperform their non-hybrid double-layer and single-layer counterparts under in-plane loading, reporting an increase in collapse strength and energy absorption by factors of 1.64 and 2.25, respectively. These improvements are attributed to the mechanical interactions occurring at the interface between the auxetic and non-auxetic layers within the hybrid structure, effectively enhancing its structural attributes. Furthermore, the double-layer honeycombs display excellent strain-sensing capabilities within the elastic regime, with gauge factors reaching values as high as 146. Mechanical tests conducted at elevated temperatures reveal that the CF/PA12 honeycombs retain a significant portion of their elastic modulus, strength and energy absorption even at 125 °C, while maintaining high gauge factors of up to 72.4. These honeycombs also exhibit pronounced thermoresistive behavior, evidenced by a decrease in electrical resistance of up to 41.3 % with increasing temperatures from 25 to 125 °C. Considering their exceptional combination of thermo-mechanical, thermoresistive and piezoresistive characteristics, these hybrid double-layered CF/PA12 honeycombs hold promise for potential applications in multifunctional lightweight structures, offering integrated temperature and strain-sensing capabilities.

Physical and mechanical properties of deflection-hardening hybrid fibre-reinforced recycled aggregate concrete

Recycled aggregate concrete (RAC) has been gaining a large interest in recent years due to the depletion of natural aggregates and environmental protection requirements. To improve the ductility of RAC for structural applications and to avoid corrosion risks involved with utilising steel fibres, this study proposes a deflection-hardening hybrid fibre-reinforced recycled aggregate concrete (FRRAC) by combining newly developed macro-basalt fibre (BF, 0.67 % by volume) and recycled macro-polypropylene fibre (PF, 0.67 % by volume). Its fresh, static and dynamic mechanical properties were investigated and compared with the mix containing macro-BF only (1.34 % by volume). A Ø 100 mm split Hopkinson pressure bar (SHPB) system was used to determine the dynamic mechanical properties in compression and tension. The hybrid FRRAC retained up to 90 % of its average first peak load at 3.5 mm crack width and showed better cracking bridging performance under dynamic splitting tension than the specimens with the same volume of macro-BF. Empirical formulae for dynamic increase factors and energy absorption capacities against varying strain rates have also been proposed for the newly developed hybrid FRRAC.

Enhanced impact toughness of 316L stainless steel welded joint by ultrasonic impact

316 L welded structures have been widely used in the industrial field, but the weld defects seriously affect the reliability. The ultrasonic impact treatment (UIT) is used to improve the quality of welded joints and the effects of the UIT on the impact toughness, fracture morphology, microhardness and microstructure of the 316 L stainless steel welded joint were studied. Moreover, the coupled finite element model of the 316 L stainless steel welding-UIT was established to study the effects of the UIT on the residual stress. The results showed that the UIT could effectively improve the impact toughness of the 316 L stainless steel welded joint, and the impact toughness could be improved with the increasing of the UIT current. According to the fracture morphology, it was found that the fibrous region increased, and the radical region decreased. In addition, the dimple of the material tends to become deeper and larger, and the increase of dimple was accompanied by the increase of energy absorption. The microhardness of the welded joint was improved, and the grain was refined, which indicated that the 316 L stainless steel welded joint generated obvious plastic deformation. The simulation results show the welded joints can introduce the significant residual compressive stress under the action of the UIT. Based on the comprehensive analysis of the UIT on impact toughness, the generated plastic deformation, the reduced grain size, and the introduced residual compressive stress of the 316 L stainless steel welded joint were the main reasons for the improvement of the impact toughness.

Experimental and simulation study of the crashworthiness behavior of thickness-graded auxetic structures of ductile and brittle materials

This article examines the compressive behavior of re-entrant auxetic structures to optimize its energy absorption. The unique properties of auxetic structures have made them popular in various industries, especially for sports equipment. This study aims to create different types of structures using an FDM 3D printer. First, an appropriate raster angle for 3D printing of tensile test samples is examined for PLA and PLA+ materials. Next, three types of structures are constructed using brittle PLA and ductile PLA+ materials, and their energy absorption is compared. These structures are homogeneous auxetic re-entrant (HAR), unilateral graded thickness (UGT), and bilateral graded thickness (BGT). Changing from brittle (PLA) to soft material (PLA+) increases energy absorption in all structures. Likewise, grading the thickness of the structure, especially on BGT, increases energy absorption. Simulation results are validated by modeling the structures in two ways for brittle and ductile materials using Abaqus software. Finally, based on the simulation results, the most appropriate step of the bilateral graded thickness is recognized as 0.8-1-1.2.

Influence of Interface Type on Dynamic Deformation Behavior of 3D-Printed Heterogeneous Titanium Alloy Materials.

Using the Split Hopkinson Pressure Bar technique, strain-limited dynamic compressive loading experiments were performed on TA1/TA15 heterostructure (HS) materials. The plastic deformation mechanisms, fracture forms, and energy absorption properties of an HS material with a metallurgical bonding interface (MB) and an HS material without a metallurgical bonding interface (NMB) are compared and analyzed. The results show that there is no significant difference between the two deformation mechanisms. The fracture forms are all "V-shaped" fractures within the TA1 part. The NMB was carried for 57 μs before failure and absorbed 441 J/cm3 of energy. The MB was carried for 72 μs before failure and absorbed 495 J/cm3 of energy. Microstructure observations show that there is a coordinated deformation effect near the MB interface compared to the NMB, with both TA1 and TA15 near the interface carrying stresses. This causes an enhancement of the MB load-bearing time and a 12% increase in energy absorption.

Pilot Study Investigating Effects of Changing Process Variables on Elastic and Energy-Absorbing Characteristics in Polyurethane/Agglomerated Cork Mix for Use in Micro-Transport Helmet.

This pilot investigation identifies the influence that changing the process variables of curing pressure, curing temperature, and mix ratio of a polyurethane/agglomerated cork matrix has on the mechanical properties of energy absorption, Young's modulus of elasticity, and spring stiffness in safety helmets intended for micro-transport riders. The results are compared to expanded polystyrene, a material commonly used in micro-transport helmets. Mechanical testing of the various samples found that, over the range tested, curing pressure had no effect on any of the mechanical properties, while increasing amounts of resin caused a stiffer structure, and increasing curing temperature led to increased energy absorption. Consistent with the elastic modulus findings, all polyurethane/agglomerated cork test samples demonstrated higher median levels of spring stiffness, ranging from 7.1% to 61.9% greater than those found for expanded polystyrene. The sample mixed at a 1.5:1 binder/cork ratio and cured at 40 °C displayed the closest spring stiffness to EPS. While the mechanical properties of the eco-friendly polyurethane/agglomerated cork matrix did not match those of expanded polystyrene, the difference in performance found in this study is promising. Further investigation into process variables could characterise this more ecologically based matrix with equivalent energy-absorbing and structural characteristics, making it equivalent to currently used expanded polystyrene and suitable for use in micro-transport helmets.

Pull-Through Behavior of Novel Additively Manufactured Sandwich Composite Inserts.

Joining structural components with mechanical fasteners is common in many engineering applications across all industries. This study investigates combining additive manufactured inserts with sandwich composites consisting of aluminum honeycomb cores with carbon fiber reinforced facesheets. The combination of these components offers an integrated, lightweight solution when mechanically fastening sandwich composite components using bolted joints. The experimental and numerical investigation explores the influence insert geometry has on the structural response of a sandwich composite under pull-through load scenarios. Various failure modes are observed during experimental analysis with facesheet debonding being the initial failure mode. In addition, finite element models investigate the stress fields in the honeycomb core and overall panel deflections, validating the mechanics observed experimentally. When comparing additively manufactured inserts to standard inserts, additively manufactured inserts have increases in stiffness, maximum force, and total energy absorption of 7.1%, 53.0%, and 62.3%, respectively. These results illustrate the potential of an integrated approach to mechanical joint technology by combining additively manufactured inserts with sandwich composite components using aluminum honeycomb cores.

Investigating the Impact of Friction Stir Processing on the Hydrogen Embrittlement in AA6082-T6 Heat-Treatable Aluminum Alloy

AbstractThis study investigates the impact of friction stir processing (FSP) on the hydrogen embrittlement (HE) in AA6082-T6 heat-treatable aluminum alloy. The effects of different number of FSP passes and different hydrogen cathodic charging (HCC) conditions on the material’s response to HE are examined through comprehensive mechanical testing, microhardness analysis, and microstructural characterization. The results revealed that FSP leads to a decrease in yield strength, ultimate tensile strength, and microhardness, accompanied by an increase in energy absorption. The introduction of hydrogen through HCC significantly reduces mechanical properties, particularly in non-FSPed specimens. Notably, specimens with 8 FSP passes exhibit an interesting behavior with a slight increase in energy absorption and microhardness values after HCC. Microstructural analysis shows that FSP refines the microstructure, resulting in enhanced resistance to hydrogen-induced blistering effects. These findings contribute to the understanding of hydrogen embrittlement in FSPed aluminum alloys, providing insights for developing surface-modified materials suited for hydrogen-rich applications. Graphical Abstract

A Synergistic Approach Combining Surface Enhancement and Buckling Modes for Improved Axial Crushing Performance of Thin-Walled Tubes

Abstract In this study, thin-walled tubes were circumferentially strengthened by plasticity ball burnishing of critical locations determined from buckling mode analysis. Axial crush test results revealed that the surface-treated (ST) tubes increased localized yield strength, attained superior crashworthiness performance, and triggered predictable deformation modes according to the buckling modes of the tubes. Numerical analysis was performed and successfully validated with the experiment at 90% prediction accuracy. The treated tube ST-4 with the 12th buckling mode outperformed a conventional tube with an increase in specific energy absorption (SEA) and crush force efficiency (CFE) by up to 70% while sustaining a low increase in initial peak force (IPF). Furthermore, the tube demonstrated a greater rate of energy dissipation compared to tubes with conventional surface-treated patterns at the same level of surface-treated area. The crashworthiness performance improved as the surface-treated area ratio increased. A theoretical model was developed for the surface-treated tube based on fundamental deformation kinematics, predicting mean crushing force and total energy absorption with acceptable accuracy. The findings strongly suggest that the proposed surface-enhanced tubes have great potential to be used as energy-absorbing structures in crashworthiness applications.

A ribbed strategy disrupts conventional metamaterial deformation mechanisms for superior energy absorption

ABSTRACT Enhancing energy absorption in mechanical metamaterials has been a focal point in structural design. Traditional methods often include introducing heterogeneity across unit cells. Herein, we propose a straightforward ribbed strategy to achieve exceptional energy absorption. We demonstrate our concept through modified body-centered cubic (BCC) and face-centered cubic (FCC) ribbed truss-lattice metamaterials (BCCR and FCCR). Using stainless-steel 316L samples, compression tests indicate a 111% and 91% increase in specific energy absorption (SEA) for BCCR and FCCR, respectively, along with an enhancement in compression strength by 61.8% and 40.7%. Deformation mechanisms are comprehensively elucidated through both finite element analysis and theoretical calculations. The mitigation of stress concentration at nodes, redistribution of load transfer pathways within struts, and introduction of multiple plastic hinges collectively contribute to increased energy absorption and higher compression strength. Using rein-based polymer samples, the ribbed truss-lattice metamaterials also exhibit exceptional damage tolerance, experiencing only a 15% loss in maximum strength after cyclic compression at 20% strain, while maintaining a 73% higher SEA compared to their non-ribbed counterpart. This strategy extends beyond the discussed structures, presenting itself as a generic approach to enhance plateau strength and SEA.

Investigation of dynamic compression properties of lightweight engineered geopolymer composites containing different ceramsites (LW-EGC)

Lightweight engineering geopolymer composites (LW-EGC) can contribute to green building materials products by taking advantage of the advantages of man-made ceramsite and geopolymers. In this paper, an active "sacrifice" method was proposed, which is based on the idea that low elastic modulus ceramsites are preferentially damaged or ruptured during the impact loading process, thus absorbing and dissipating the impact energy. LW-EGC was enhanced by PVA fiber with volume fraction of 2% and multi-walled carbon nanotubes with mass fraction of 0.15%. The dynamic compression properties of LW-EGC containing different ceramsites were studied by using Φ100 mm split Hopkinson pressure bar (SHPB) test device. The compression characteristics of the LW-EGC under an impact load were evaluated, including the strain rate, dynamic stress–strain relationship, elastic modulus, dynamic increase factor (DIF), energy absorption, and failure patterns. The results showed that the dynamic peak stress, dynamic peak strain, DIF, energy absorption and damage degree of LW-EGC all increased with the increase of strain rate, showing obvious strain-rate sensitivity. At high strain rate, the dynamic elastic modulus mainly showed softening effect. At the same strain rate, the impact resistance of LW-EGC-1 containing fly ash ceramsite was the best, and the damage degree of LW-EGC-3 containing shale ceramsite was the lowest. Empirical DIF formulas of the LW-EGC was proposed; the DIF increased approximately linearly with the strain rate in a logarithmic manner.

Dynamic responses of shear thickening fluid-filled lattice structures

Lattice structures that possess exceptional energy absorption capabilities show promise across various fields. However, their tendency to exhibit relatively low stiffness due to rotation or bending during impacts poses a challenge. Shear thickening fluid with the unique property of shear thickening effect can be an ideal filler to overcome the limitation of lattice structure. In this paper, composites that combined STF with new lattice structures were fabricated to investigate their dynamic response using experimental and numerical means and found that incorporating STF into these lattice structures not only preserved the inherent mechanical characteristics of the lattice structures but also led to substantial improvements on mechanical performance. The lattice structures displayed a noteworthy boost in stiffness, increasing significantly from 11.02 to 85.56 times. Additionally, there was an improvement in energy absorption, ranging from 2.78 to 5.51 times. These findings indicate that STF holds more promise in enhancing a structure's stiffness compared to its energy absorption capacity. Moreover, strain rate, weight fraction of STF, and cell size of the lattice structure were considered to further investigate their impact on the dynamic behaviour of STF-filled lattice structures. Our findings indicate that the increase in stiffness and energy absorption of the lattice structure following STF filling is correlated with an increase in strain rate and weight fraction but decreases when the cell size of the lattice structure is increased. The critical strain rate of STF-filled lattice structure was predicted, around 104 s−1, which indicates the onset of the shear-thickening effect in STF. Furthermore, it was observed that composites with higher weight fractions of STF were more responsive to changes in strain rate. Additionally, structures with initially lower mechanical properties experienced the most significant improvements after being filled with STF. These optimal outcomes provide valuable insights for the design of STF-filled lattice structures in practical applications.

Effects of textile type on the flexural properties of prefabricated hollow-core slabs strengthened with PVA fibers-improved TRM

In this study, the utilization of textile-reinforced mortar (TRM) in the strengthening and rehabilitation field is investigated. To regulate crack width, polyvinyl alcohol (PVA) fibers were incorporated into the TRM matrix. Nine prefabricated hollow-core slabs strengthened with TRM, along with one reference slab, were subjected to static loading using a 4-point bending apparatus. The experimental variables consisted of the type of textile (glass, basalt, and carbon) and the number of textile layers (one, two, and three layers). The experimental findings demonstrated that the inclusion of PVA fibers improved the TRM by effectively controlling crack width and increasing energy absorption capacity. Among the textile types, carbon TRM-strengthened slabs exhibited the highest flexural capacity. This capacity increased by 74%, 119%, and 132% for slabs strengthened with one, two, and three layers of textile, respectively. Glass TRM-strengthened slabs demonstrated superior deformability, with an increase rate ranging from 202% to 331%. Finally, to predict the flexural capacity and deflection of the tested slabs, a theoretical analysis was conducted and validated by comparing the theoretical predictions to the actual test results for accuracy and reliability.

Energy absorption characteristics of asymmetric tree-like fractal gradient hierarchical structures

Bionic gradient hierarchy design as a design method that can effectively improve the structural crashworthiness, but its current research only focuses on the symmetric fractal method related to the discussion. In view of this, this article carries out the innovative design and research of asymmetric tree-like fractal gradient hierarchy structure (ATFGHS). The results show that the crashworthiness of the structure can be greatly improved by using the asymmetric tree-like fractal gradient hierarchy design method. Specifically, the ATFGHS-P3 showed a 98% increase in energy absorption (EA), a 98% increase in specific energy absorption (SEA), and an 84% increase in crush force efficiency (CFE) compared to a conventional hexagonal multicellular tube. The completion of this study provides valuable insights into the design and optimization of novel lightweight thin-walled energy-absorbing structures.