Absorption Behavior Research Articles

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.

Effect of biochar content and particle size on mechanical and water absorption properties of landscaping waste/polylactic acid composites

The high-value utilization of landscaping waste to produce wood-plastic composites provides a promising approach to waste management, yet remains a challenge. In this study, wood-plastic composites were prepared using landscaping waste and polylactic acid (PLA) through an extrusion-molding process, with biochar (BC) as the reinforcing material. First, the effects of biochar content (0.5 %, 1 %, 2 %, 3 %, 4 %) and particle size (100mesh, 300mesh, 800mesh, 1200 mesh) on the physico-mechanical and dynamic thermo mechanical properties of the composites were analyzed. A multivariate nonlinear model was employed to fit the flexural properties of the composites. Additionally, the water absorption properties were investigated under immersion conditions at three different temperatures (20°C, 35°C, 50°C). The results demonstrated that biochar significantly improved the interfacial compatibility between landscaping waste and PLA, enhancing the mechanical properties of this composite. When the biochar content was 1 % and particle size was 100 mesh, flexural strength reached 25.16 MPa, respectively, representing increases of 19.20 % over composites without biochar, while the change in impact strength was small. In addition, the water absorption process of composites with 1 % BC were well fitted by Fick's law. SEM morphology observation indicated that interfacial bonding was reduced after water absorption, which was consistent with the test results. Combined with Arrhenius equation and Fick's law, the water absorption model of the composites at each water immersion temperature was obtained, which can predict the water absorption behavior at 60°C.

Acoustic modeling of three-dimensional-printed fibrous sound absorbersa).

In this study, an analytical model was developed to predict the sound absorption performance of fibrous absorbers fabricated using an extrusion-based three-dimensional (3D) printing method. The proposed model employs geometric design parameters, including the average fiber diameter and the horizontal and vertical fiber separations, to calculate the porosity, static airflow resistivity, tortuosity, and viscous and thermal characteristic lengths. These transport parameters are then used within the Johnson-Champoux-Allard semiempirical formulation to predict the normal incidence sound absorption coefficient. The analytical model was validated by comparing the calculated properties with those obtained using the finite element-based hybrid numerical modeling method and those estimated through direct and indirect experimental measurements. Finally, by using the validated analytical model, the effect of each geometrical design parameter on the sound absorption performance of the 3D-printed fibrous absorbers was investigated, revealing that the absorption behavior is primarily controlled by the static airflow resistivity and showing that high absorption peaks and a broadband absorption profile can be achieved by adjusting the three geometrical parameters. This study highlights the potential of 3D printing to fabricate fibrous sound absorbers with tailored acoustic properties, offering a promising solution for advanced noise control materials.

Energy absorption and deformation of cellular structures with dovetail joints

In this paper, the dovetail joint is creatively applied to cellular structural plates. Based on the concave cellular structural dovetail joint plates, several new cellular structural dovetail joints with stable quality are designed by chamfering the joints and bending the rods. Tensile experiments of several dovetail jointed cellular structure plates are carried out to investigate the effects of the connection methods on energy absorption and deformation behavior. Finite element models are established and the finite element simulation results are compared with the experimental results for verification. By comparing the different dovetail connection methods, the results show that under axial tensile conditions, the dovetail-jointed cellular structures generally fail at the rod connections. The chamfering of the rod connection and the bending of the rod at the connection can significantly improve the model load-carrying capacity, and when the chamfering or the degree of rod bending is large, the energy-absorbing characteristics of the model can be significantly improved due to the increased stress and deformation of the model's horizontal rods.

Influence of density of a polyurethane microcellular elastomer foam on its compressive energy absorption and time-dependent behavior

Influence of density of a polyurethane microcellular elastomer foam on its compressive energy absorption and time-dependent behavior

Mitigating aging infrastructure risks: An optimized epoxy resin system for water supply pipeline rehabilitation

Urban water supply networks are crucial for ensuring the delivery of safe drinking water to urban populations; however, the aging infrastructure in these systems has led to a rising incidence of leaks and frequent pipeline failures, posing serious risks. Traditional repair approaches encounter limitations in terms of efficiency, durability, and environmental safety, particularly when employed in potable water pipelines. To address these challenges, we developed a novel multi-component amine-cured epoxy resin system specifically optimized for in-situ curing under ambient conditions. This study comprehensively examines the mechanical properties, water absorption behavior, and curing kinetics of this resin system, formulated to reduce volatile organic compound emissions while enhancing durability under prolonged water exposure. Experimental findings demonstrate that the E2 formulation exhibited superior tensile strength, flexural properties, and fracture toughness relative to other formulations, with a two-stage water absorption model accurately predicting resin behavior in moisture-laden environments. Moreover, finite element modeling and laboratory testing confirmed the influence of bubble defects on mechanical performance, and a negative pressure defoaming technique effectively reduced defect volume, resulting in a 17.6% improvement in tensile strength. Collectively, this research advances the practical application of rapid-curing resins, offering a resilient, safe, and sustainable solution for the rehabilitation of aging water pipeline networks.

ACOUSTIC-MODELING OF RANDOM FIBROUS MATERIALS

We present a microstructure-based model for determining the sound absorption behavior and transport parameters of random fibrous materials and exploring the physical mechanisms underlying acoustic energy dissipation. In order to increase the generalizability of the model, a three-dimensional random fiber structure is employed for simulation. The propagation of sound waves is associated with four transport parameters, including viscous permeability, tortuosity, as well as viscous and thermal characteristic lengths. These parameters are determined by the porosity and diameter of the fibrous material. By using the method of multi-scale asymptotic simulation, the theoretical model for transport parameters includes unknown coefficients that are adjusted based on the simulated results. The sound absorption coefficients are then obtained by integrating the transport parameters into the widely-used Johnson-Champoux-Allard (JCA) model for porous materials. The theoretical predictions match well with existing experimental measurements on sintered fiber metals and fibrous copper wires. Our model systematically examines the impact of fiber diameter, porosity, and material thickness on sound absorption performance. Optimal results are achieved by carefully selecting fiber diameter and porosity to enhance the acoustic dissipation of sound waves, while thicker fibrous materials increase sound absorption in the low frequency range. The model provides a theoretical framework for designing and fabricating fibrous materials to reduce noise.

Investigating the Acoustic Behavior of Polyurethane Foam Reinforced with Clay Nanoparticles

Introduction: Disturbing noise can cause physical and mental illnesses among workers; for this reason, it is necessary to restrain it, especially in workplaces. Using sound-absorbing materials with suitable acoustic properties has been a growing trend in mitigating noise. This study aimed to improve the acoustic properties of polyurethane foam (PUF) as a sound absorber. Material and Methods: In the present study, PUF was synthesized with different percentages of clay nanoparticles (0 -1.2 wt.%), and then the Sound Absorption Coefficient (SAC) of the synthesized PUF was measured by the acoustic impedance tube in the frequency range of 63 to 6400 Hz according to the ISIRI 9803 standard. The morphology of the foam was also investigated by Scanning Electron Microscope (SEM) Results: The results showed that the addition of clay nanoparticles to PUF improved the sound absorption behavior of the samples, and the best sound absorption behavior was for PUF with 1.2% weight of nanoparticles at low frequencies (500-2600 Hz). This increase in the absorption coefficient can be due to the increase in the number and smaller size of the pores with the increase in the amount of nanoparticles in PUF. Conclusion: This study illustrates that the incorporation of clay nanoparticles into PUF at varying percentages results in an enhanced absorption coefficient. The presence of clay nanoparticles leads to a reduction in cell size and an increase in the number of pores, consequently enhancing surface friction. The absorption coefficient was observed to increase with the growing concentration of clay nanoparticles in PUF.

Crashworthiness and stiffness improvement of a variable cross-section hollow BCC lattice reinforced with metal strips

The ultra-lightweight structures with high mechanical properties and energy absorption behaviors are focused on the innovation structural design. The design strategy of implementing novel unit cells within architecture materials such as lattice materials enables the attainment of unparalleled combinations of mechanical properties and functionalities while minimizing weight. The most common method to design light-weight lattice materials is optimizing the geometric configurations of the unit cells. However, changing the geometric boundary of lattice structures can also be a good solution to improve the mechanical characteristics and energy absorption behaviors of the lattice materials. In this work, a novel variable cross-section hollow (VCH) lattice was established to improve the energy absorption capacity. By adding metal strips on the edge of the VCH lattices, a new reinforced variable cross-section hollow (RVCH) lattice with metal strips was developed to further enhance the stiffness and energy absorption capacity. The stainless VCH and RVCH lattices were additively manufactured by Selective Laser Melting (SLM) using an EP-M450H metal 3D printer. The quasi-static compressive characteristics and energy absorption behaviors of RVCH lattices were studied experimentally. Finite element modeling was implemented to study the energy absorption mechanism of RVCH lattices. A parametric analysis based on the finite element models was conducted to study the influence of different metal strips on the energy absorption capacity of RVCH lattices. The results show that the RVCH lattices with metal strips attaching to the vertical edges can signally enhance energy absorption of lattice structures with good load uniformity. Furthermore, the natural frequencies analysis indicate that the higher bending stiffness and the tensile stiffness can be achieved for RVCH lattices. This novel lattice is more stable as a load-bearing structure and more efficient as an energy absorber, which can provide guidance in designing innovative lattice structures with excellent mechanical properties and energy absorption capacity.

Seismic Behavior Improvement of Rigid Steel Frame Braced with Cable and Optimal Rotational Friction Damper

The research focused on enhancing the seismic performance of steel moment frames using cable braces and a central friction damper. By optimizing the design and pretensioning force of the cable braces, this study aimed to improve the energy absorption and overall behavior of the frames under cyclic earthquake loads. A quasi-cyclic loading test was developed through FE simulations using ABAQUS software, version 2023. To verify the modeling, an experimental test was compared with the numerical modeling, and the numerical results confirmed the accuracy of the experimental data. Results made by modeling in ABAQUS software (version 2023) include the impact of pretensioning force on stiffness and energy absorption, the relationship between pretensioning force and force required to move the target, the increase in absorbed energy with pretension force up to 25%, and the superior seismic performance of frames with rotational friction dampers. This study also highlighted the benefits of using cable braces with a friction damper regarding the symmetry of hysteresis diagrams, cyclic performance, and energy absorption capacity. The amount of pretensioning of the cables affects the energy dissipation capacity. As the pretensioning of the cables increases, the energy dissipation capacity initially increases. However, further increases in pretensioning lead to decreased energy dissipation capacity beyond a certain point. When the percentage of cable brace pretension increases from 2% to 25%, the energy dissipation capacity is enhanced by 2%, and when in the 25–30% range, it stabilizes at around 35%. Energy dissipation capacity decreases for pretensions of more than 30%.

Structural regulation and sodium storage mechanism of high-performance non-graphitic carbon derived from semi coke

Non-graphitic carbon (NGC) is considered as one of the most promising anodes for sodium-ion batteries (SIBs) because of its low cost and abundant reserves. Nevertheless, there is significant debate regarding the contribution mechanism of sloping and plateau capacity. Herein, a series of NGC with adjustable defect concentration, carbon phases and pore structure are synthesized with semi-coke as precursor to explore the sodium storage mechanism and an “adsorption-insertion-filling” model is proposed based on the in-depth analysis of microstructure and electrochemical behaviors. The very attraction about this work is that the entire discharge curve is divided into three regions for analysis, and the corresponding cause for each region is traced. To be specific, the defects and disordered structure contribute to the surface-controlled absorption behavior in the sloping region >0.1 V, the pseudo-graphitic structure shows diffusion-controlled insertion behavior in the plateau region between 0.1 and 0.05 V, and the closed pores formed by curved graphite-like structure provide plateau capacity (<0.05 V) through the filling of quasi-metallic sodium. This study provides theoretical education for the optimization of NGC anode structure and a novel approach for the excessive value-added utilization of semi coke.

Distinct nonlinear absorption behaviors in Cu1.8S nanocrystals influenced by geometry features

Spherical and lamellar [Formula: see text] nanocrystals with radial dimension of about 40[Formula: see text]nm were synthesized by the thermal injection method. Combining the crystal and morphological analysis with the photo physical property, the lamellar [Formula: see text] nanocrystals displayed the typical features of 2D metal sulfides which can be ultrasonically exfoliated into single or few layers of [Formula: see text] nanosheets due to the fact that the atomic layers were bonded by interlayer van der Waals forces. While in the spherical [Formula: see text] nanocrystals, no exfoliation or morphological change occurred after sonication. The nonlinear optical properties of spherical and lamellar [Formula: see text] nanocrystals after sonication were investigated by the [Formula: see text]-scanning technique using a 532-nm nanosecond laser pulse. The lamellar [Formula: see text] nanocrystals showed saturation absorption, reaching a normalized transmittance of 1.58 at [Formula: see text] with a [Formula: see text] value of [Formula: see text] and [Formula: see text] value of [Formula: see text]. While the spherical [Formula: see text] nanocrystals exhibited optical limiting effects, reaching the normalized transmittance of 0.38, with a [Formula: see text] value of 8[Formula: see text]cm/GW. Distinct nonlinear absorption behaviors in [Formula: see text] nanocrystals with the similar lateral size were observed in the spherical and lamellar [Formula: see text] nanocrystals, showing significant geometry feature-dependent nonlinear absorption behaviors.

Bilosomes and Niosomes for Enhanced Intestinal Absorption and In Vivo Efficacy of Cytarabine in Treatment of Acute Myeloid Leukemia

Cytarabine (CTR) is a hydrophilic anticancer drug used to treat leukemia. It suffers from poor permeability and intestinal metabolism, diminishing its oral bioavailability. Background/Objectives: The objective was to develop and evaluate niosomes and bilosomes for enhanced intestinal absorption; hence, oral bioavailability. Results: CTR-loaded niosomes and bilosomes with vesicle sizes of 152 and 204.3 nm were successfully prepared with acceptable properties. The presence of bile salts increased the zeta potential of bilosomes. The recorded entrapment efficiency of cytarabine was acceptable for such a hydrophilic drug. CTR-bilosomes showed a pH-dependent drug release pattern with preferred release in pH 6.8. Intestinal absorption behavior indicated a site-dependent CTR absorption pattern with unfavorable absorption in the distal intestine. Niosomal and bilosomal formulations enhanced intestinal absorption parameters with evidence for a predominant paracellular absorption mechanism that bypasses intestinal barriers. The investigation of the anti-leukemic effect of niosomal and bilosomal formulations indicated that both formulations ameliorated the blood parameters, reflecting significant improvement in leukemia treatment compared with the drug solution. Pathological examination of blood films revealed decreased blast cells in peripheral blood in groups treated with tested formulations. Methods: Tested formulations were prepared according to the pro-concentrate method and characterized for particle size, zeta potential, entrapment efficiency, and in vitro release. CTR-loaded niosomes and bilosomes were evaluated for enhanced intestinal absorption utilizing the single-pass in situ intestinal perfusion method in rabbits, and the anti-leukemic effect was assessed using the benzene-induced leukemia model in rats. Conclusions: This study introduced surfactant vesicles for enhanced oral bioavailability of CTR.

Impact of structural characteristics on energy-absorption of 3D-printed thermoplastic polyurethane line-oriented structures

Purpose Additive manufacturing offers the ability to produce complex, flexible structures from materials like thermoplastic polyurethane (TPU) for energy-absorption applications. However, selecting optimal structural parameters to achieve desired mechanical responses remains a challenge. This study aims to investigate the influence of key structural characteristics on the energy absorption and dissipation behavior and the deformation process of 3D-printed flexible TPU line-oriented structures. Design/methodology/approach Samples with varying line orientations and infill densities were fabricated using material extrusion and subjected to quasi-static compression tests. The design of experiments methodology explored the significance of design variables and their interaction effects on energy absorption and dissipation. Findings The results revealed a statistically significant interaction between infill density and orientation, highlighting their combined influence; however, the effect was less pronounced compared to infill density alone. For low-density structures, changing the orientation from 0°/90° to 45°/−45° and increasing infill density enhanced energy absorption and dissipation, while high-density structures exhibited unique energy absorption behavior influenced by deformation patterns and heterogeneity levels. This study facilitates the prediction of mechanical responses and selection of suitable TPU line-oriented printed parts for energy absorbing applications. Originality/value To the best of the authors’ knowledge, the present work have investigated for the first time the energy-related responses of flexible line-oriented TPU structures highlighting the distinction between the low and high density structures.

Enhanced Energy Absorption and Unusual Mechanical Behaviors of Continuously Graded Diamond-Shellular Nanostructures

Enhanced Energy Absorption and Unusual Mechanical Behaviors of Continuously Graded Diamond-Shellular Nanostructures

Investigation on the Moisture Absorption Behaviors of Palm Leaves (Corypha umbraculifera) and Their Variation Mechanism.

Palm leaves serve as a traditional recording medium and are widespread in south and southeast Asia, and they have a long history. However, they are sensitive to environmental fluctuations, especially moisture, which may severely affect their conservation status. In this research, the moisture absorption behaviors of palm leaves in different states, including raw, treated, naturally aged, and artificially aged ones, were investigated by intelligent gravimetric analysis (IGA) and water retention value (WRV) to analyze their moisture absorption characteristics. Mathematical model was employed to fit and analyze their water adsorption curves, aiming to explore the content and distribution of the adsorbed water in monolayered and multilayered. Then, the chemical and physical properties of different palm leaves were studied by chemical composition analysis, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM), and low-field nuclear magnetic resonance (low-field NMR), and the relationship between moisture absorption characteristics and their chemical composition and physical structures was analyzed. The results demonstrated that both treatment and aging processes could have a noticeable impact on the moisture absorption of palm leaves, as evidenced by reduced equilibrium moisture content (EMC) at high relative humidity (RH), decreased multilayer water adsorption content, and slightly increased monolayer water adsorption content. Besides, palm leaves exhibit a lower rate of moisture adsorption, at ∼30-50% RH, which facilitates their long-term conservation. The results of chemical and physical analyses revealed that the reduced content of hydrophilic groups was the primary reason for a decrease in palm leaves moisture absorption. Additionally, the fiber structure changes of palm leaves caused by treatment or aging may have different influences on their moisture adsorption, especially the content of monolayer adsorbed water.

Experimental study on absorption and desorption behavior of a novel metal hydride reactor for stationary hydrogen storage applications

Metal hydrides have captured significant attention for hydrogen storage because of their high energy density and safety. However, the performance of these systems is largely influenced by the design of the storage reactor. In this perspective, a novel compact, lightweight, and effective multi tube MH reactor was designed, fabricated, and experimentally tested. The absorption and desorption behavior of the newly developed Ti0.9Zr0.1Mn1.46V0.45Fe0.09 alloy using the proposed MH reactor for hydrogen storage applications was analysed. At 30 bar supply pressure, the MH reactor absorbed 164.3 g (1.58 wt.%) of hydrogen in 894 s and delivered specific energy at an average rate of 94.7 W/kgMH. Further, the reactor released 153.6 g (1.48 wt.%) of hydrogen in 2246 s, when the desorption temperature was set at 50 °C. Moreover, the parametric study revealed that by raising the supply pressure from 10 bar to 20 bar and 30 bar, the stored capacity was improved by 11 % and 18.9 %, respectively, whereas the absorption time was drastically reduced by 43 % and 61.5 %, respectively. Furthermore, the fabricated reactor achieved gravimetric and volumetric storage densities of 0.75 % and 20.6 kg/m3 of H2. Also, the MH reactor achieved a maximum hydrogen storage efficiency of 82.3 %. Finally, the comparative results indicated that the MH reactor studied in this work demonstrated a faster hydrogen release rate compared to other medium to large capacity MH reactors reported in the literature.

Impact of molecular configuration on the photoluminescence and electrical characteristics of poly-pyrrol-thiazol-imine polymers films

The optical, photoluminescence, and electrical properties of Poly(Z)-PTI and Poly(E)-PTI, two Poly-Pyrrol-Thiazol-Imine polymers with comparable chemical structures but distinct configurations, were examined. Using the dip-casting method, polymer films were deposited on ITO substrates. UV-VIS spectroscopy revealed that both polymers diverged between 500 and 800 nm, showing the impact of molecular arrangement, but showed similar absorption behavior for wavelengths shorter than 500 nm. For Poly(Z)-PTI, the direct optical energy gaps were 2.06 eV, while for Poly(E)-PTI, they were 1.78 eV. Poly(Z)-PTI displayed an emission peak at 610 nm (red) according to laser photoluminescence spectra, while Poly(E)-PTI peaked at 563 nm (green-yellow). The capacitance behavior was revealed by electrochemical impedance spectroscopy. Nyquist plots suggested an equivalent circuit model of Rs (CRct)(QR)(CR) for both polymers, and the relaxation times were 15.9 ns for Poly(Z)-PTI and 89.5 ns for Poly(E)-PTI. The Mott-Schottky analysis verified the n-type conductivity, revealing 2.18 × 1016 cm− 3 carrier densities for Poly(Z)-PTI and 1.78 × 1016 cm− 3 for Poly(E)-PTI. At lower frequencies, both polymers exhibited limited conductivity and large dielectric constants. Insights into the possible uses of Poly-Pyrrol-Thiazol-Imine polymers in electrical and optoelectronic devices are provided by this study, which emphasizes the influence of molecular configuration on these polymers’ characteristics.

Third-order nonlinear optical properties based on triphenylamine derivative-based covalent organic frameworks

Nonlinear optics (NLO) is an extremely critical research area. In recent years, covalent organic frameworks (COFs) have attracted much attention as a potential NLO material. In this study, a series of COF materials with different D-A effects were successfully synthesized based on the excellent electron-donating properties of the triphenylamine group and were prepared into D-A COFs\\KBr sheet materials that can be used for third-order NLO by the KBr−pressing method. The results of the open-aperture Z-scan technique showed that all COFs\\KBr sheets exhibited saturable absorption (SA) behavior at 3 μJ, with nonlinear absorption coefficients (β) of −1.64, −1.23, and −2.02 × 10−9 mW−1 for PT-PA, PT-BD, and PT-TZ, respectively. Theoretical calculations show that the electron transport distance of PT-PA is shorter than that of PT-BD, while the introduction of S atoms makes the D-A effect of PT-TZ stronger than that of PT-BD, and thus the SA properties of PT-PA and PT-TZ are better than those of PT-BD. These works indicate that the COFs\\KBr sheets have a potential application as high-performance NLO materials and also provide an option for COFs powder application in the field of third-order NLO.

Moisture-induced mechanical property changes in natural hybrid composites with mwcnt fillers

ABSTRACT This study investigates the moisture absorption behaviour and its effects on the mechanical properties of polyester composites reinforced with jute and hemp fibres. The differences in moisture absorption between distilled water and saltwater are examined. Tensile and flexural tests are conducted on pure jute fibre-reinforced polyester composite, pure hemp fibre-reinforced polyester composite, and jute (J-P) and hemp (H-P) fibre-reinforced polyester composite. Changes in mechanical properties due to varying moisture conditions are analysed. Furthermore, the impact of a synthetic nano filler, multiwall carbon nanotubes (MWCNTs), on these composites is assessed. The study reveals that MWCNTs enhance mechanical properties, particularly in moist conditions. Fracture behaviour analysis aids in understanding the interaction between natural fibres, the matrix, and nano-reinforcement. At maximum natural fibre weight fractions (40%), moisture absorption reaches 8.17% for the J-P composite in distilled water and 9.61% in saltwater, while the H-P composite shows maximum absorptions of 6.61% and 8.27%, respectively. The hybrid composite records 4.18% and 7.17% under similar conditions. Compared to the plain jute fibre-reinforced composite, the addition of multiwall carbon tubes into the polymer matrix significantly reduces the moisture absorption capacity of the jute composite to 34.89% and 31.30% for distilled water and saltwater, respectively.