Energy Absorption Efficiency Research Articles

A computational investigation into energy absorption characteristics of multicomponent facing-foam systems of helmets

The strategic utilization of facing layers is investigated as a mechanism to increase the energy absorption in foam liner systems for improving the protective performance of helmets. Energy absorption applications extensively use foams because of their ability to efficiently absorb large amounts of strain energy at low stress levels; however, many deformations are localized to a small volume of the foam available in the system thereby reducing the material system effectiveness. One of these cases occurs as the result of poor fit of helmets. This paper details a systematic computational investigation characterizing the energy absorption of multi-layer material constructions consisting of foam combined with a relatively stiff facing layer. Results obtained reveal that facings provide a mechanism to alleviate the effects of a small deformation area caused by both poor fit and thick comfort foam in helmets, though the facings must have substantial flexural rigidity of [Formula: see text] to improve the energy absorption of the pads. Energy absorption efficiency of the foam-facing system for multiple loading curvatures have been used to quantify the energy absorption improvements of the system provided by the use of higher facing rigidity, especially when the impact is near or past the edge of the pad system.

Energy Aggregation for Illuminating Upconversion Multicolor Emission Based on Ho3+ Ions.

Lanthanide-doped upconversion luminescent nanoparticles (UCNPs) have garnered extensive attention due to their notable anti-Stokes shifts and superior photostability. Notably, Ho3+-based UCNPs present a complex energy level configuration, which poses challenges in augmenting their luminescence efficiency. Herein, a rational design strategy was used to enhance the upconversion luminescence intensity of Ho3+ ions by improving the photon absorption ability and energy utilization efficiency. Efficient absorption and transfer of excitation light energy were achieved through carefully selected host materials, precisely controlled sensitizers, and the design of external energy antennas using organic dyes, enhancing upconversion luminescence. Due to the attenuation effect of hydroxyl vibration on upconversion luminescence, the nanomaterials exhibit multicolor luminescent characteristics in different solution environments. Significantly, the composites exhibit intense upconversion of red light in aqueous solution, showing great application potential in biomedicine and colorimetry.

Analysis and optimization of threaded shear energy absorbing components of collision resistance hydraulic support columns

Conventional energy-absorbing components have limitations in terms of performance and functionality, including significant variability in reaction forces, inherent instability, and inadequate energy absorption capabilities. This paper presents a threaded shear-type energy-absorbing component designed for anti-impact hydraulic support columns, specifically for ZQL advancing support roadway hydraulic supports. The component operates based on the principle of threaded shear energy absorption. Its key structural parameters—such as thread shape, outer diameter, and pitch—are optimized using single-factor and response surface experimental design methods. Shear simulations are performed to analyze the deformation and force-displacement characteristics across various structural configurations. The impact of different thread parameters on energy absorption performance is evaluated, with quasistatic shear tests and simulations validating the results. The optimized design enhances energy absorption efficiency and provides a foundation for future research on integrating these components into hydraulic support systems to improve overall performance.

Energy absorption characteristics of asymmetric tree-like fractal hierarchical circular tubes under axial impact

A circular tube structure with asymmetric tree-like fractal hierarchical properties, known as asymmetric tree-like fractal hierarchical circular tubes (ATFH), was designed by combining an asymmetric tree-like fractal hierarchical structure with a single circular tube. The crashworthiness of this structure under axial impact was investigated using an experimentally validated LS-DYNA finite element model. Results showed that the Specific Energy Absorption (SEA) of ATFH-L4 tubes improved by 17.65%, 51.21%, 39.85%, 20.37%, 10.45%, and 44.81% compared to BBT, CMT, CT, GBCT-L3, HCT-P, and MCT tubes, respectively. The study of energy absorption performance of ATFH tubes at different fractal positions revealed that ATFH-L2-B6/8, ATFH-L3-B6/8, and ATFH-L4-B5/8 exhibited superior energy absorption properties. These findings demonstrate that the asymmetric tree-like fractal hierarchical structure design can enhance structural crashworthiness. The results provide an effective guide for designing multi-cellular structures with high energy absorption efficiency.

Deformation Behavior of Inconel 625 Alloy with TPMS Structure.

Triply periodic minimal surfaces (TPMSs) are known for their smooth, fully interconnected, and naturally porous characteristics, offering a superior alternative to traditional porous structures. These structures often suffer from stress concentration and a lack of adjustability. Using laser powder bed fusion (LPBF), we have fabricated Inconel 625 sheet-based TPMS lattice structures with four distinct topologies: Primitive, IWP, Diamond, and Gyroid. The compressive responses and energy absorption capabilities of the four lattice designs were meticulously evaluated. The discrepancies between theoretical predictions and the fabricated specimens were precisely quantified using the Archimedes' principle for volume displacement. Subsequently, the LPBF-manufactured samples underwent uniaxial compression tests, which were complemented by numerical simulation for validation. The experimental results demonstrate that the IWP lattice consistently outperformed the other three configurations in terms of yield strength. Furthermore, when comparing energy absorption efficiencies, the IWP structures were confirmed to be more effective and closer to the ideal performance. An analysis of the deformation mechanisms shows that the IWP structure characteristically failed in a layer-by-layer manner, distinct from the other structures that exhibited significant shear banding. This distinct behavior was responsible for the higher yield strength (113.16 MPa), elastic modulus (735.76 MPa), and energy absorption capacity (9009.39 MJ/m3) observed in the IWP configuration. To examine the influence of porosity on structural performance, specimens with two varying porosities (70% and 80%) were selected for each of the four designs. Ultimately, the mechanical performance of Inconel 625 under compression was assessed both pre- and post-deformation to elucidate its impact on the material's integrity.

Theoretical Study of the Pre-Plasma Density Scale Length’s Influence on the Absorption Efficiency in Laser–Solid Interaction at Relativistic Laser Intensities for PW-Class Lasers

This work studied the pre-plasma that builds up in interactions of focused high-power PW-class lasers with solid targets at the target surface facing the laser beam, and its impact on the global laser absorption efficiency as well as on the spectral cut-off energy of laser-generated proton beams. Our practical heuristic estimates were derived from the example of the VEGA-3 laser at CLPU. Our modeling results for the pre-plasma expansion due to the laser pedestal of VEGA-3 were benchmarked by hydrodynamic simulations, revealing good agreement for the evolution before the arrival of the main Gaussian laser intensity peak. Our detailed numerical two-dimensional Particle-in-Cell simulations showed the impact of different pre-plasma scale lengths on the absorption efficiency of laser energy into electrons, relevant for the seeding of other types of radiation. It was shown that the absorption can increase manyfold when increasing the pre-plasma scale length. This effect can be beneficial for the spectral cut-off energy of accelerated protons, where a trade-off between absorption and electron dynamics yields an optimum pre-plasma scale length. The findings can be applied to other PW-class laser facilities.

Optimizing core yarn twist levels for enhanced mechanical properties of aramid-wrapped yarns and fabrics

This study addresses the issue of low surface energy of aramid fibers and their fabrics and aims to enhance their mechanical properties including tensile strength and impact resistance. Using the hollow spindle spinning method, aramid fiber bundles are employed as the core yarns with varying twist levels and nylon fibers are used as the wrapping yarns to create the nylon/aramid-wrapped yarns, which are then woven into the nylon/aramid fabrics. The investigation focuses on the effect of core yarn twist levels on the mechanical properties of the yarns and fabrics. Experimental results reveal that applying an appropriate core yarn twist can significantly improve the mechanical properties of the yarns and fabrics. Specifically, with the optimized the core yarn twist of 80 turns per meter (tpm) the tensile and hook strengths of the wrapped yarns reach 3.3 GPa and 1.2 N/Tex, respectively which are about 20.6% and 21.7% increase as compared to the untwisted yarns. Similarly, the plain-woven fabric consisting of the 80 tpm yarns achieves a tensile strength of 2577.9 N/cm, a pull-out force of 160.2 N, and an absorbed energy per unit volume of 436.5 KJ/m3 which are about 20.0%, 31.4% and 30.1% improvement, respectively as compared to the fabrics with the untwisted yarns. Additionally, the optimized fabric presents a 28.4% increase in the energy absorption efficiency and significant enhancement in abrasion resistance. These findings offer valuable insights for the potential applications of the nylon/aramid-wrapped yarns for developing personal protective fabrics and products.

Polarization-Insensitive, High-Efficiency Metasurface with Wide Reception Angle for Energy Harvesting Applications.

This research presents an innovative polarization-insensitive metasurface (MS) harvester designed for energy harvesting applications at 5 GHz, capable of operating efficiently over wide reception angles. The proposed MS features a novel wheel-shaped resonator array whose symmetrical structure ensures insensitivity to the polarization of incident electromagnetic (EM) waves, enabling efficient energy absorption and minimizing reflections. Unlike conventional designs, the metasurface achieves near-unity harvesting efficiency, exceeds 94% under normal incidence, and maintains superior performance across various incident angles for TE and TM polarizations. To validate the design, a 5 × 5-unit cell array of the MS structure was fabricated and experimentally tested, demonstrating excellent agreement between simulation and measurement results. This work significantly advances metasurface-based energy harvesting by combining polarization insensitivity, wide-angle efficiency, and high absorption, making it a compelling solution for powering wireless sensor networks in next-generation applications.

Effect of Chemical Foaming Process Parameters on the Performance of Epoxy Foam and Parameter Optimization Strategies

To prepare polymer foams with low‐density and high‐energy absorption efficiency, this study designs epoxy foaming experiments employing the Box–Behnken method and investigates the impact of process parameters on the microscopic geometric parameters and uniaxial compression response of foam. Finite element analysis models are created to investigate the microscale deformation mechanism. The main results are as follows: 1) The average equivalent cell diameter is significantly affected by foaming temperature and foaming agent content, while cell wall thickness is more influenced by the foaming agent content and the precuring time. 2) The compression response is most significantly affected by foaming temperature, followed by foaming agent content, with precuring time showing less significant influence. The differences in the stress–strain curves during various stages of deformation are due to the buckling of cell walls and the subsequent collapse of cells. 3) Density exhibits a highly positive correlation with strength and modulus while showing a relatively high negative correlation with energy absorption efficiency. Based on these findings, process parameters are optimized using the Hooke–Jeeves algorithm and experimentally validated, demonstrating the reliability of the optimization strategy. The experimental design and process parameter optimization strategy can be applied to other polymer foaming research.

Induced structure and its gradient design on energy absorption properties and failure behavior of aluminum/carbon fiber reinforced polypropylene super hybrid tube

AbstractThe metal/fiber super hybrid tube is a mixture of pure metal and carbon fiber structure, featuring both stable energy dissipation of the metal and good energy absorption efficiency of the composite, with greatly improved lightweight. However, the failure mode of the hybrid tube is unstable and prone to Eulerian buckling, which affects its energy absorption performance. In this work, aluminum alloy/carbon fiber reinforced polypropylene super hybrid tube (Al/CFPP super hybrid tube) have been obtained through the addition of an induced structures, which aims at reducing the maximum peak load generated during collision. The effects of induced grooves and holes structure (number of holes, diameter and row number) on the damage and energy absorption were discussed. The results showed that the initial peak load can be effectively reduced by adding an induction groove structure. When the number of induction holes is 4, the diameter is 5 mm, and the number of rows is 1, the initial peak load decreases by 14.06%, and the total energy absorption is basically unchanged. Additionally, the gradient design of the hole diameter and spacing significantly helped guide the gradual failure of the structure, with the initial peak load decreased by 21.98% and the total absorption energy increased by 20.26%.Highlights Super hybrid structures were developed to improve crashworthiness. The effect of induced grooves energy absorption was analyzed. The effect of hole size and quantity energy absorption were analyzed. A gradient design of hole size and spacing was proposed. The combined of the induction hole and trigger angle was demonstrated.

Bionic Inner-Tapered Energy Absorption Tube Featuring Progressively Enhanced Fold Deformation Mode.

Slender tubes are in high demand owing to their lightweight and outstanding energy absorption. However, conventional slender tubes are prone to catastrophic failures such as Euler's buckling under axial load. Interestingly, growing bamboos overcome this similar dilemma via a unique tapered intine in the internodes, which endows them with excellent energy absorption. Inspired by this finding, a bionic inner-tapered tube (BITT) was designed to enhance the energy absorption of slender tubes under axial load. The special energy absorption (SEA) was evaluated via a quasi-static axial compression test. Then, theoretical calculation and finite element analysis were carried out to analyze the energy absorption mechanisms. The results reveal that the tapered inner wall induces a progressively enhanced fold deformation mode for BITT, which not only prevents buckling failure and decreases initial peak crushing load but also improves the energy absorption efficiency by increasing plastic deformation. The influences of taper and length-diameter ratio on the axial energy absorption of BITT are explored. Finally, the bionic square array (BSA) and bionic hexagon array (BHA) are fabricated by taking BITT as the basic structural unit, which significantly improves the main energy absorption performance indicators under axial load.

The effect of impactor shape on low velocity impact behavior of cylindrical sandwich structures with trapeozidal core

The aim of this study is to investigate the impact performance of a cylindrical sandwich structure with Trapeozidal core under different geometries of impactors using the finite element method. The effects of impactor shape, facesheets thickness and impact point on peak contact force, absorbed energy efficiency, maximum displacement and damage deformation are investigated. Progressive damage analysis based on the Hashin damage criterion was performed using MAT 54 material model in LS DYNA finite element program for low velocity simulations. The impact behavior was investigated by creating a Cohesive Zone Model (CZM) based on bilinear traction-separation law while providing the connection between the core structure and its surfaces. At the end of the study, it was determined that the contact force values at P2 were higher than P1. Peak force variation values for cylinder, cone and sphere tipped impactors at P1 and P2 points were 43.5%, 132.3% and 62.2%, respectively. Core support has a significant effect on the contact force. The peak force value and energy absorption efficiency value obtained with the Cone impactor are higher than the others. For all three impactors, it was determined that the largest and dominant damage type was matrix damage.

Study on the mechanical properties of the thin-walled double circular tube filled with a novel NPR lattice core based on the concave rotating mechanism

Abstract This study presents a thin-walled double circular tube filled with a novel negative Poisson’s ratio(NPR) lattice core based on the concave rotating mechanism. The unit cell of the NPR lattice core is constructed by replacing each inclined side of a concave hexagon with a smaller concave hexagon with an identical geometry aspect ratio. The single cell is arrayed to obtain a two-dimensional honeycomb structure, and then curling and mirroring operations are utilized to get a circular tube structure. Compressive deformation and load-displacement response of NPR lattice core with different concave angles are analyzed by FEM. To validate with numerical results, the NPR lattice core samples are prepared using 3D printing technology and subjected to quasi-static uniaxial compression experiments. Then, the thin-walled double circular tube filled with the NPR lattice core(FDCT) is established. The load-displacement relationship and energy absorption characteristics are analyzed, and the effects of two angle parameters on the specific energy absorption of the structure are discussed. The results show that an increase in the concave angle decreases the rigidity of the NPR lattice core. When subject to compression, all models show NPR effects, with minimum and maximum Poisson's ratios of -0.29 and -0.5, respectively. For FDCT, it is found that the interaction between the core layer and the tube wall enhances the structure's energy absorption performance. Changes in the core layer angle parameters affect the energy absorption of the FDCT structure, where increasing the concave angle improves the energy absorption efficiency of the structure. In contrast, the effect of the rotational angle is not significant.

Numerical and Experimental Study on the Hydrodynamic Performance of a Sloping OWC Wave Energy Converter Device Integrated into Breakwater

This study presents numerical and experimental investigations on an oscillating water column (OWC) wave energy device integrated into a sloping breakwater. Regular waves were generated in a physical wave tank to investigate the hydrodynamic performance and extraction efficiency of the small-scale nested OWC device. Simultaneously, to complement various scenarios, numerical simulations were conducted using the open-source computational fluid dynamics platform OpenFOAM. The volume of fluid (VOF) method was employed to capture the complex evolution of the air–water interface, and an artificial source term (Forchheimer flow region) was introduced into the Navier–Stokes equations to replace the power take-off (PTO) system. By analyzing wave reflection properties, energy absorption efficiency, and wave run-up, the hydrodynamic characteristics of the inclined OWC device were explored. The comparison between the numerical and experimental results indicate a good consistence. A smaller front wall draft broadens the high-efficiency frequency bandwidth. For relatively long waves, increasing the air chamber width enhances energy conversion efficiency and reduces wave run-up. The optimal configuration was achieved with the following dimensionless parameters: front wall draft a/h=1/3, air chamber width d1/h=2/9, and slope i=2. Due to the sloped structure, when compared with a vertical OWC, long waves can more easily enter the chamber. This causes the efficient frequency bandwidth to shift towards the low frequency range, allowing more wave energy to be converted into pneumatic energy. As a result, wave run-up is reduced, enhancing the protective function of the breakwater.

Tunable mechanical performance of nanoporous energy absorption composite material

Abstract Nanofluidic energy absorption materials (NEAs) represent smart and efficient energy absorption composite materials in the ever-growing application of advanced protective structures. In this paper, an integrated experimental and molecular dynamics simulation study is conducted on the NEAs (ZSM-5/water) to investigate the tunable strategy of mechanical performance and energy absorption by considering the microstructural, mechanical, and thermal factors. The results demonstrate that the NEAs is an efficient and tunable liquid spring-like volume memory material. The typical NEAs show superior energy absorption capacity, achieving a specific energy absorption of 5.17 J/cm³ and an energy absorption ratio of 1.14 J/cm³ per cycle. Compared with insensitivity of the loading rate, the solid-fluid mass ratio is confirmed to significantly affect energy absorption performance, with an optimal ratio of approximate 1. Temperature is validated as an effective in-situ tunable parameter for NEAs in terms of both infiltration and energy absorption properties, with only slight effect on exfiltration. The critical infiltration pressure and specific energy absorption decrease by 23% and 40% as temperature increase from 25°C to 80°C. The gas-fluid interaction based energy absorption mechanism under high temperatures is proposed according to the comparison between experimental results and molecular dynamics simulations. The findings in this work will provide novel materials solutions for the intelligent energy absorption protective structures.

Energy Absorption Behavior of Elastomeric Matrix Composites Reinforced with Hollow Glass Microspheres

Hollow glass microsphere (HGM) reinforced composites are a suitable alternative to energy absorption materials in the automotive and aerospace industries, because of their high crush efficiency and energy absorption characteristics. In this study, a polyurethane elastomeric matrix was reinforced with HGMs for HGM loadings ranging from 0 to 70 vol% (volume fraction). Quasi-static uniaxial compression tests were performed, subjecting the composite to compressive strains of up to 65%, to assess stress vs. strain and energy absorption characteristics. The results reveal that samples with a higher concentration of spheres generally exhibit better crush efficiency. Specifically, the highest crush efficiency was observed in samples with a 70 vol% HGM loading. A similar relationship was reflected in the energy absorption efficiency results, with the highest energy absorption observed in the 65 vol% sample. A correlation exists between the concentration of HGMs and important metrics such as mean crush stress and energy absorption efficiency. However, it is crucial to note that the optimal choice of sphere concentration varies depending on the desired performance characteristics of the material.

Comparative Study of the Effect of Paraffin Phase Change Material Mixture and Ice Bag on Temperature Control in Bricks

The goal of the article is to improve the thermal properties and energy efficiency of the walls and facades of the buildings by introducing the phase change material in the bricks. This study focuses on the thermal insulation capabilities of a paraffin-ice bag PCM mixture, aiming to enhance the thermal inertness of the bricks. The paraffin wax exhibits a high latent heat and is chemically stable, while the ice bags, with their low temperatures, serve as effective thermal regulators. They complement each other to address challenges such as the low thermal conductivity of paraffin and the leakage of low phase change transition temperature in paraffin. We made use of two types of paraffin and ice bag PCMs in a 50:50 ratio and embedded them in standard bricks. During the experiment, we coated the brick surfaces with liquid cement to enhance the hydraulic resistance of the PCM. Next, we inserted wires known as packing plugs into the bricks and filled the holes with powders. We also subjected the bricks to heating and cooling in cycles, ensuring the temperatures remained within a specified range. During the experiment, temperature sensors were utilized to capture data concerning thermal performance. The authors reached the conclusion that PCM polymer composite bricks possess a lot of promise such walls are being able to maintain their thermal performance parameters. When PCM-enhanced bricks are utilized, temperature changes were significantly restricted, staying constant during the times of peak heating and cooling. The PCM bricks also displayed efficient absorption and gradual release of energy due to the high energy transfer rates during phase change. This study suggests that PCM polymer composite bricks are cost-effective for the energy performance of buildings.

Study on the Impact Resistance of the Honeycomb Composite Sandwich Structure by a Fragment Flight Angle

At present, the typical targets in the air are mainly high-speed impact bodies such as fragments, which pose a great threat to aviation equipment such as drones. It is urgent to study the impact resistance of different initial conditions of fragments to honeycomb sandwich structures. The fragment impact experiment analyzes the fragment flight attitude, fragment power, failure mode, and impact resistance of the structure by changing the different impact velocities on the target plate. In order to study the damage mode and anti-damage performance of several composite honeycomb sandwich structures under oblique penetration impact mode, a total of six groups of composite honeycomb structures were tested by fragment impact sandwich structure at different angles, and the damage law of composite honeycomb sandwich structure in the experiment was compared and analyzed. According to the experimental results, the accuracy of the theoretical model and numerical simulation was verified by fragment impact composite honeycomb sandwich structure. The analysis results show that the failure mode of the composite honeycomb sandwich structure under oblique impact is quite different from that of the traditional structure, which is mainly reflected in the material accumulation type of the failure part. Compared with the traditional structure, the composite honeycomb sandwich structure exhibits better energy absorption efficiency, which is increased by 130% and 600%, respectively. This paper shows the different failure modes of honeycomb sandwich structure under oblique impact and positive impact. The existence of an inclined angle changes the failure mode, increases the damage range, and increases the total energy absorption. It is necessary to further study the failure mechanism of fragment flight angle on honeycomb sandwich structure and provide a reference for the impact resistance design of the structure.

Effect of hollow beads content in aluminum oxide hollow beads reinforced epoxy composites on mechanical and energy absorption properties of the composites

AbstractAluminum oxide hollow microbeads/epoxy resin composite is a kind of epoxy resin‐based multi‐porous energy‐absorbing material. This study improved the brittleness and toughness of epoxy resin. Adding hollow aluminum oxide microbeads with different mass fractions increased the energy absorption capacity. Quasi‐static compression tests were carried out at room temperature to test the compression properties of epoxy resin/hollow microbead composites. The composites′ energy absorption properties and energy absorption efficiency were analyzed and calculated using the obtained compression curves. The fracture characteristics and microscopic morphology of the composite specimens were observed by scanning electron microscopy. It was found that aluminum oxide hollow microbeads, as reinforcement material, can effectively improve the brittleness and yield strength of epoxy resin materials and enhance the energy absorption performance and energy absorption efficiency of composite materials. With the increase in the mass fraction of hollow microbeads, the energy absorption performance of the composite material first increases and then decreases. Its performance is the most significant when the mass fraction of aluminum oxide hollow microbeads is 10 %.

INVESTIGATION OF IMPACT PERFORMANCE OF CYLINDER CORRUGATED SANDWICH STRUCTURES WITH DIFFERENT GEOMETRIC CONFIGURATIONS

The aim of this study is to numerically investigate and compare the impact performance of CFRP composite cylinder sandwich structures with five different geometric configurations. The impact performances and damage types of composite cylinder structures for different core configurations were determined. The impact analyses were performed in LS DYNA finite element program using MAT-54 material model with Progressive damage analysis based on the combination of Hashin damage criterion, Cohesive zone model and Bilinear traction-separation law. Among the five different specimens in the study, the highest peak force (PF) value of 1.88 kN was obtained at impact point P2 of the Trapeozidal sandwich structure. The lowest value was obtained at P1 impact point in Triangular sandwich structure with 0.62 kN. The highest and lowest energy absorption efficiency occurred in the Triangular structure, 78% and 38% respectively. The PF value at P2 point is higher than P1. The effect of core support on PF is very important. Since point P1 is not supported by the core, it is determined that the deformation is larger than P2.