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An experimental device fixed with a laser displacement sensor was assembled to investigate the rebound behaviors and damping mechanism of rubber balls prepared with ethylene-propylene-diene monomer (EPDM)/chlorinated butyl rubber (CIIR) blends. The result showed that a prediction model was proposed to characterize the damping capacity by using the rebound height of the rubber balls. The lower rebound height corresponded to better damping capacity. A modified equation relating to the rebound height has been obtained from the theoretical derivation on the basis of the dynamic mechanical analysis, showing that the rebound height was affected by the deformation frequency, the external excitation, and the nature of rubber blends. Furthermore, the energy dissipation rate (EDR), defined by the ratio of the height loss to the rebound time, was proposed to further characterize the damping capacity. The EDR value was shown to be highest for the pure CIIR and lowest for the pure EPDM, exhibiting a decreasing trend with the increase in EPDM content in the rubber blends. It can be expected that the damping capacity of the EPDM/CIIR blends decreases with the decrease in external excitation, the conclusion of which plays a key role in the formulation design of viscoelastic damping rubber materials.

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In the field of aerospace and advanced equipment manufacturing, accurate response analysis has been paid more attention, requiring a more comprehensive study of the variation of mechanical parameters with the service environment. The damping variation characteristics of 304 aluminum alloy, Sa564 high-strength alloy, GW63K magnesium alloy, and Q235 steel were investigated in this paper, which plays a significant role in the dynamic responses of structures. Variable damping ratios were revealed by the damping tests based on a dynamic mechanical analysis (DMA). The numerical method of temperature/frequency-dependent damping parameters in stochastic dynamics was focused on. With a large variation in the damping ratio, a numerical constitutive relation for temperature-dependent damping was proposed, and an efficient stochastic dynamics method was derived to analyze the responses of structures based on the pseudo excitation method (PEM) and variable damping theory. The computational accuracy and validity of the proposed method are confirmed during the vibration tests and numerical analysis. Based on the comparison results of the two damping models and the experiments on GW63K alloy, we proved that the proposed method is more accurate to the real response of the actual engineering structure. The differences in dynamic responses between the constant damping and experiments are significant, and more attention should be paid to the numerical method of stochastic dynamic response of variable damping materials in the aviation and aerospace fields and high-temperature environments.

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As the lightest structural metal material, magnesium alloys possess good casting properties, high electrical and thermal conductivity, high electromagnetic shielding, and excellent damping properties. With the increasing demand for lightweight, high-strength, and high-damping structural materials in aviation, automobiles, rail transit, and other industries with serious vibration and noise, damping magnesium alloy materials are becoming one of the important development directions of magnesium alloys. A comprehensive review of the progress in this field is conducive to the development of damping magnesium alloys. This review not only looks back on the traditional damping magnesium alloys represented by Mg-Zr alloys, Mg-Cu-Mn alloys, etc. but also introduces the new damping magnesium materials, such as magnesium matrix composites and porous magnesium. But up to now, there have still been some problems in the research of damping magnesium materials. The effect of spiral dislocation on damping is still unknown and needs to be studied; the contradiction between damping performance and mechanical properties still lacks a good balance method. In the future, the introduction of more diversified damping regulating methods, such as adding other elements and reinforcements, optimizing the manufacturing method of damping magnesium alloy, etc., to solve these issues, will be the development trend of damping magnesium materials.

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Magnesium alloys with high damping, high specific strength and low density have attracted great attention in recent years. However, the application of magnesium alloys is limited by the balance between their mechanical and damping properties. The strength and plasticity of magnesium alloys with high damping performance often cannot meet the industrial requirements. Understanding the damping mechanism of magnesium alloys is significant for developing new materials with high damping and mechanical properties. In this paper, the damping mechanisms and internal factors of the damping properties of magnesium alloys are comprehensively reviewed. Some damping mechanisms have been studied by many scholars, and it has been found that they can be used to explain damping performance. Among existing damping mechanisms, the G-L dislocation theory, twin damping mechanism and interface damping mechanism are considered common. In addition, some specific long-period stacking ordered (LPSO) phases' crystal structures are conducive to dislocation movement, which is good for improving damping performance. Usually, the damping properties of magnesium alloys are affected by some internal factors directly, such as dislocation density, solute atoms, grain texture and boundaries, etc. These internal factors affect damping performance by influencing the dissipation of energy within the crystal. Scholars are working to find novel damping mechanisms and suitable solute atoms that can improve damping performance. It is important to understand the main damping mechanisms and the internal factors for guiding the development of novel high-damping magnesium alloys.

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PURPOSE: The aim of this study was to evaluate the reliability of implant stability measuring devices depending on the location of the implant and the position of the patient. MATERIALS AND METHODS: Six implants were installed in different dentate sextants of six artificial bone models. Implant stability was measured in three conditions of the bone model (without mounting on a phantom head, mounted on a phantom head in supine position, and mounted on a phantom head in upright position). A resonance frequency analysis device (Osstell) and two damping capacity analysis devices (Periotest and Anycheck) were used to measure implant stability. The values measured outside the phantom head were treated as controls, and the values inside the phantom head were compared using an independent t-test. RESULTS: Osstell showed different results in two of the six divisions in both the supine and upright positions compared to outside of the mouth (P < .05). Periotest showed different results in all six parts in the supine position and in five parts in the upright position compared to outside of the mouth (P < .05). While Anycheck showed different results in five areas in the supine position compared to outside of the mouth, it showed different results in only one area in the upright position (P < .05). CONCLUSION: In the difficult implant position for the operator to access, the implant stability measuring devices show less reliability. The accessibility of implant is greatly affected in the order of Osstell, Anycheck, and Periotest.

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Fe-Ga alloys (GalFeNOLs) are the focus of attention due to their enhanced magneto-elastic properties, namely, magnetostriction in low saturation magnetic fields. In the last several years, special attention has been paid to the anelastic properties of these alloys. In this review, we collected and analyzed the frequency-, amplitude-, and temperature-dependent anelasticity in Fe-Ga and Fe-Ga-based alloys in the Hertz range of forced and free-decay vibrations. Special attention is paid to anelasticity caused by phase transitions: for this purpose, in situ neutron diffraction tests with the same heating or cooling rates were carried out in parallel with temperature dependencies measurements to control ctructure and phase transitions. The main part of this review is devoted to anelastic effects in binary Fe-Ga alloys, but we also consider ternary alloys of the systems Fe-Ga-Al and Fe-Ga-RE (RE-Rare Earth elements) to discuss similarities and differences between anelastic properties in Fe-Ga and Fe-Al alloys and effect of RE elements. We report and discuss several thermally activated effects, including Zener- and Snoek-type relaxation, several transient anelastic phenomena caused by phase transitions (D03 ↔ A2, D03 → L12, L12 ↔ D019, D019 ↔ B2, Fe13Ga9 → L12+Fe6Ga5 phases), and their influence on the above-mentioned thermally activated effects. We also report amplitude-dependent damping caused by dislocations and magnetic domain walls and try to understand the paradox between the Smith-Birchak model predicting higher damping capacity for materials with higher saturation magnetostriction and existing experimental results. The main attention in this review is paid to alloys with 17-20 and 25-30%Ga as the alloys with the best functional (magnetostriction) properties. Nevertheless, we provide information on a broader range of alloys from 6 to 45%Ga. Due to the limited space, we do not discuss other mechanical and physical properties in depth but focus on anelasticity. A short introduction to the theory of anelasticity precedes the main part of this review of anelastic effects in Fe-Ga and related alloys and unsolved issues are collected in summary.

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For a wide industrial application of magnesium alloys, a method for imparting high damping properties while maintaining mechanical properties is required. Controlling the crystallographic texture seems to be useful, because dislocations are known to have a significant influence on the damping characteristics of magnesium alloys. In addition, textures are affected by the microstructure and texture variation when the deformation or annealing is applied. However, there were less reports about their effect on damping capacity. Therefore, the effect of twinning and annealing, which can affect the recrystallization, were investigated in this study. An AZ31 alloy was hot rolled at 673 K with a reduction ratio of 10% and 50%, and then annealed at 673 K and 723 K for 0.5, 1, 2, and 3 h, respectively. SEM-EBSD was used to examine the microstructure and texture. In addition, each specimen's hardness and internal friction were contemporarily measured. As a result, hot rolling produced tensile twins and their fraction increased with internal friction when the reduction ratio increased. Due to annealing, a discontinuous type of static recrystallization occurred within the twinning grains, and was highly activated along with the increasing annealing temperature and the fraction of twinning. In the samples annealed at 723 K, the internal friction continuously increased over the annealing time, whereas in the samples annealed at 673 K, the decrease in dislocation density was delayed while the internal friction showed a relatively low value.

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Designing new materials for vibration and noise reduction that are lightweight is of great significance for industrial development. Magnesium (Mg) alloy is considered one of the best damping metal structural materials because of its low density, high specific strength, good energy storage characteristics and rich resources. Solution atoms have an important effect on the damping capacities of Mg alloys, but the relevant laws have not been completely clarified. In this work, two kinds of alloying elements (Ga and Er) with various atomic sizes were selected to study the metallographic structure and damping capacities of binary Mg-X (X = Ga and Er) alloys in the as-cast and solid solution states, respectively. Solution treatment can improve the damping capacities of binary Mg-X (X = Ga and Er) alloys, and the damping mechanisms of the two solid solution alloys are consistent with the G-L damping mechanism. The influence of alloy elements with different atomic sizes on damping capacities is also different. This influence is due to the various radii of solute atoms and Mg atoms which can result in different degrees of lattice distortion. This work provides a research basis for development and design of high-performance damping Mg alloy materials.

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Composite materials based on magnesium-lithium (MgLi) and magnesium-yttrium (MgY) matrices reinforced with unidirectional carbon fibers were prepared using the gas pressure infiltration method. Two types of carbon fibers were used, high-strength PAN-based T300 fibers and high-modulus pitch-based Granoc fibers. The PAN-based carbon fibers have an internal turbostratic structure composed of crystallites. The pitch-based carbon fibers have a longitudinally aligned graphite crystal structure. The internal carbon fiber structure is crucial in the context of the interfacial reaction with the alloying element. There are various mechanisms of bonding to carbon fibers in the case of magnesium-lithium and magnesium-yttrium alloys. This paper presents the use of the DMA method for the characterization of the role of alloying elements in the quality of interfacial bonding and the influence on the complex modulus at increasingly elevated temperatures (50-250 °C). The complex modulus values of the composites with T300 fibers were in the range of 118-136 GPa. The complex modulus values of the composites with Granoc fibers were in the range of 198-236 GPa. The damping capacity of magnesium-based unidirectionally aligned carbon fiber composites is related to the quality of the interfacial bonding.

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This paper discusses the effect of different heat treatment procedures on the microstructural characteristics, damping capacities, and mechanical properties of CuAlNi shape memory alloys (SMA). The investigation was performed on samples in the as-cast state and heat treated states (solution annealing at 885 °C/60'/H2O and after tempering at 300 °C/60'/H2O). The microstructure of the samples was examined by light microscopy (LM) and scanning electron microscopy (SEM) equipped with a device for energy dispersive spectrometry (EDS) analysis. Light and scanning electron microscopy showed martensitic microstructure in all investigated samples. However, the changes in microstructure due to heat treatment by the presence of two types of martensite phases (ß1' and γ1') influenced alloy damping and mechanical properties by enhancing alloy damping characteristics. Heat treatment procedure reduced the alloys' mechanical properties and increased hardness of the alloy. Fractographic analysis of the alloy showed a transgranular type of fracture in samples after casting. After solution annealing, two types of fracture mechanisms can be noticed, transgranular and intergranular, while in tempered samples, mostly an intergranular type of fracture exists.

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The capability of damping mechanical energy in polycrystalline metals depends on the activities of defects such as dislocation and grain boundary (GB). However, operating defects has the opposite effect on strength and damping capacity. In the quest for high damping metals, maintaining the level of strength is desirable in practice. In this work, gradient nanograined structure is considered as a candidate for high-damping metals. The atomistic simulations show that the gradient nanograined models exhibit enhanced damping capacities compared with the homogeneous counterparts. The property can be attributed to the long-range order of GB orientations in gradient grains, where shear stresses facilitate GB sliding. Combined with the extraordinary mechanical properties, the gradient structure achieves a strength-ductility-damping synergy. The results provide promising solutions to the conflicts between mechanical properties and damping capacity in polycrystalline metals.

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OBJECTIVES: To evaluate and quantify the damping capacities of common CAD/CAM restorative materials (CRMs) and to assess their energy dissipation abilities by comparing loss tangent and Leeb hardness data. METHODS: Leeb hardness (HLD), together with its deduced energy dissipation data (HLDdis), and loss tangent values recorded via dynamic mechanical analysis (DMA) were determined for 4 ceramic, 13 composite, and 2 polymer-based CRMs as well as 1 metal. For Leeb hardness, ten indentations per material were performed on two separate specimens (12.0 × 12.0 × 3.5 mm3) after water storage (24 h; 37.0 ± 1.0 °C). For DMA, ten specimens (16.00 × 4.00 × 1.00 mm3 ± 0.05 mm) per material were investigated in distilled water (37.0 ± 0.5 °C) with a dynamic force of 1 N at 1.5 Hz. Each data set was analyzed using two-way analysis of variance (ANOVA) with material type and material nested in material type as factors. Post-ANOVA contrasts were performed using a Bonferroni adjustment for multiple comparisons (α = 0.05). Correlations between different parameters were tested (Pearson, α = 0.05). RESULTS: HLDdis data revealed the significantly highest damping capacity for metal and the lowest values for ceramics with composites and polymers in between. However, for loss tangent, the metal together with lithium disilicate glass-ceramics exhibited the lowest damping effects and polymer materials the highest results with composites likewise in between. A strong dependency of the loss tangent results on the filler content of the investigated CRMs was indicated (r = - 0.822, p < 0.001), while a positive and only moderate correlation between loss tangent and HLDdis was observed (r = 0.565, p < 0.001), which conversely revealed a very strong correlation (r = 0.911, p < 0.001) if the metal was excluded from the calculation. CONCLUSIONS: Although HLDdis and loss tangent values both allowed a distinct differentiation of the damping capabilities of various CRMs and the respective material types, HLDdis data appeared to more accurately describe the damping capacity of CRMs as the energy dissipation mechanism of permanent plastic material deformation, that is commonly observed for metals and some composite-based CRMs, is equally captured. This finding could be particularly interesting for the future development of new CRMs with improved mechanical properties as HLDdis data determination in principle is a very efficient and simple technique to entirely specify unknown damping capacities of materials.

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The relationship between the tensile properties and damping capacity of fatigue-damaged Fe-22%Mn-12%Cr-4%Co-3%Ni-2%Si alloy under various magnitudes of fatigue stress was investigated. Analytical results show that α'- and ε-martensite were formed due to fatigue stress. The formed α'- and ε-martensite followed a specific orientation and surface relief and intersected with each other. TEM observation and pattern analysis reveal that both α'- and ε-martensites formed on the austenite. As a result of X-ray diffraction, with an increase in fatigue stress, the volume fractions of α'- and ε-martensite were increased, and the increasing rate of the volume fraction of α'-martensite was higher than that of the ε-martensite. As the fatigue stress increased, the tensile strength and damping capacity increased, but the elongation decreased. Besides, as the strength increased and the elongation decreased, the damping capacity decreased. This result is inconsistent with the general tendency for metals but similar to that of alloys undergoing deformation-induced martensite transformation.

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Additive manufacturing (AM) is a disruptive technology that enables one to manufacture complex structures reducing both time and manufacturing cost. Among the materials commonly used for AM, thermoplastic elastomers (TPE) are of high interest due to their energy absorption capacity, energy efficiency, cushion factor or damping capacity. Previous investigations have exclusively focused on the optimization of the printing parameters of commercial TPE filaments and the structures to analyse the mechanical properties of the 3D printed parts. In the present paper, the chemical, thermal and mechanical properties for a wide range of commercial thermoplastic polyurethanes (TPU) filaments were investigated. For this purpose, TGA, DSC, 1H-NMR and filament tensile strength experiments were carried out in order to determine the materials characteristics. In addition, compression tests have been carried out to tailor the mechanical properties depending on the 3D printing parameters such as: infill density (10, 20, 50, 80 and 100%) and infill pattern (gyroid, honeycomb and grid). The compression tests were also employed to calculate the specific energy absorption (SEA) and specific damping capacity (SDC) of the materials in order to establish the role of the chemical composition and the geometrical characteristics (infill density and type of infill pattern) on the final properties of the printed part. As a result, optimal SEA and SDC performances were obtained for a honeycomb pattern at a 50% of infill density.

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High strain rate rolling (HRSS) of a ZK60 magnesium alloy at 300 °C with a strain rate from 5 s-1 to 25 s-1 was used to research the effect of the rate on the mechanical properties and damping capacity of the ZK60 alloy. The results show that as the strain rate increases, the tensile strength decreases from 355 MPa at 25 s-1 to 310 MPa at 5 s-1. Two damping peaks (P1 and P2) are detected in the high strain rate rolled ZK60 alloys at different strain rates. The P1 peak appears at low temperatures and is caused by grain boundaries sliding. The P2 peak appears at high temperatures and is caused by recrystallization. As the strain rate increases from 5 to 20 s-1, the dynamic recrystallization (DRX) volume percent rises and the dislocation density decreases, both of which cause the P1 peak to become more and more obvious, and activation energy rises. At the same time, the dislocation density decreases and leads to a decrease in the storage energy, which reduces the recrystallization driving force and shifts the P2 peak to high temperatures. When the strain rate reaches 20 and 25 s-1, DRX occurs fully in the sheet, so the activation energy of the P1 peak and the temperature where the P2 peak appears are basically equal.

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

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The development of dental restorative materials that mimic tooth-like properties provided by graded structures, aesthetics and properties such as strength, damping capacity and the ability for a continuous remodeling according to the biomechanical solicitation is a great challenge. In this work, damping capacity and dynamic Young's modulus of Y-TZP/porcelain composites for all-ceramic dental restorations were studied. These mechanical properties were assessed by dynamic mechanical analyses (DMA) at frequencies of 1, 5 and 10 Hz, over a temperature ranging from 0 to 60 °C, simulating extreme conditions when a cold or hot drink is experienced. The results showed that porcelain and porcelain-matrix composites exhibited higher damping capacity while Y-TZP and Y-TZP-matrix composites presented higher dynamic Young's modulus. Furthermore, while damping capacity is strongly influenced by the temperature, no significant difference in dynamic Young's modulus was found. For both damping and modulus properties, no significant influence of frequency was found for the tested materials. Based on the obtained results and also on the known advantages of the graded Y-TZP/porcelain structures over traditional bi-layer solutions (e.g., improved bending strength, enhanced mechanical and thermal stress distribution), a novel design of all-ceramic restoration with damping capacity has been proposed at the end of this study. A positive impact on the long-term performance of these all-ceramic restorations may be expected.

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N50.5Ti49.5 foams with porosity 25.5% were prepared by transient liquid sintering process. Laminated pore architecture was created in the foam via pre-mixing Ni and Ti powders layer-by-layer. The foam consists of alternate less porous alloy layers with discontinuous closed pores and highly porous layers with continuous open pores. The sintered Ni50.5Ti49.5 foams exhibited three-step martensite transformation (MT), i.e. B2→ (R + B19'), B2→B19' and R→B19', due to the presence of heterogeneously distributed micron-sized Ni4Ti3 precipitates. By contrast, the aged Ni50.5Ti49.5 foam showed two-step B2→R→B19' MT with homogeneous nano-sized Ni4Ti3 phase. Anisotropic compressive strength and modulus were found in the sintered foam. The sintered foam had a high damping capacity (tanδ = 0.047) in the martensite and low damping capacity (tanδ = 0.002) in the austenite. However, the aged foam exhibited improved damping capacity (tanδ = 0.01) in the austenite. The enhanced damping capacity of austenite was attributed to the localized plastic deformation in nodes/struts and stress-induced B2-R MT. Furthermore, a damping peak at a temperature of 130 °C related to the (R + B19')→B2 transition during heating was confirmed. The laminated pore architecture foams with anisotropic mechanical properties may be promising candidate materials for bio- and mechanical applications.

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Conversely to natural teeth, where periodontal ligament (PDL) and pulp works as a damper reducing the effect of the stress on surrounding structures, when natural teeth is lost and replaced or restored the biting forces are directly transmitted to the bone or affect the integrity of the adjacent bottom layers. In this study, damping capacity and dynamic Young's modulus of CoCrMo-porcelain composites for dental restorations were evaluated. Dynamic Young's modulus and damping capacity of materials were assessed by dynamic mechanical analyzes (DMA) at 1 and 10 Hz frequencies, over a temperature ranging (18-60 °C). Results show that by reinforcing dental porcelain with metallic particles, producing ceramic matrix composites (CMCs) with 20 vol% and 40 vol% of metallic particles, the damping capacity and dynamic Young's modulus are improved. A decrease on both properties of the metal matrix composites (MMCs) with increasing ceramic particles content (from 20 vol% to 40 vol% of ceramic phase) was observed for all the studied frequencies and temperatures. While damping capacity is strongly dependent on frequency, no significant difference in dynamic Young's modulus was found. Results show that besides the yet reported advantages of the bio-inspired functionally graded restorations over traditional bilaminate ones, traduced by improved veneer to substrate adhesion and by the enhanced thermal and mechanical stress distribution, these restorations can also display improved behavior as regard to a damping capacity, which may have a positive impact in the long-term performance of implant - supported prosthesis.

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Designing gradient structures, mimicking biological materials, such as pummelo peels and tendon, is a promising strategy for developing advanced materials with superior energy damping capacities. Here a facile and effective approach for fabricating polymers with composition gradients at millimeter length scale is presented. The gradient thiol-ene polymers (TEPs) are created by the use of density difference of ternary thiol-ene-ene precursors and the subsequent photo-crosslinking via thiol-ene reaction. The compositional gradients are analyzed via differential scanning calorimeter (DSC), compressive modulus testing, atomic force microscopy (AFM) indentation, and swelling measurements. In contrast to homogeneous TEPs networks, the resultant gradient polymer shows a broader effective damping temperature range combining with good mechanical properties. The present result provides an effective route toward high damping materials by the fabrication of gradient structures.

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