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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.

Magnesium and magnesium-based alloys are widely used in the transportation, aerospace and military industries because they are lightweight, have good specific strength, a high specific damping capacity, excellent electromagnetic shielding properties and controllable degradation. However, traditional as-cast magnesium alloys have many defects. Their mechanical and corrosion properties cause difficulties in meeting application requirements. Therefore, extrusion processes are often used to eliminate the structural defects of magnesium alloys, and to improve strength and toughness synergy as well as corrosion resistance. This paper comprehensively summarizes the characteristics of extrusion processes, elaborates on the evolution law of microstructure, discusses DRX nucleation, texture weakening and abnormal texture behavior, discusses the influence of extrusion parameters on alloy properties, and systematically analyzes the properties of extruded magnesium alloys. The strengthening mechanism is comprehensively summarized, the non-basal plane slip, texture weakening and randomization laws are comprehensively summarized, and the future research direction of high-performance extruded magnesium alloys is prospected.

Natural bones exhibit a substantial recoverable strain ( ϵ rec ) of 2%‒4% and vary in mechanical and mass transfer properties across different body regions. Integrating these attributes is essential for the functionality and therapeutic efficacy of metallic scaffolds used in bone defect treatment. This study presents innovative superelastic nickel-titanium (NiTi) scaffolds with a remarkable maximum ϵ rec of 6%‒7% and extensive tuneability in elastic modulus, cyclic stress, compressive strength, specific damping capacity, and permeability. These impressive performance integrations are attributed to carefully designed structures featuring stable austenite phases with hierarchical microstructures and gyroid-sheet macrostructures. Physical experiments and computational simulations illustrate that this unique structure combination promotes martensitic transformation during deformation and allows the tuning of mechanical and mass transfer properties without compromising superelasticity. The deformation-recoverable and performance-tuneable NiTi scaffolds are more adaptive than their conventional counterparts, offering a versatile solution for diverse bone implantation needs. In addition to scaffold applications, this study provides valuable insights for developing advanced multifunctional metamaterials applicable in other fields. Extensively tuneable mechanical and mass transfer properties are integrated into superelastic NiTi scaffolds via laser powder bed fusion. Multiscale optimisation of microstructures and macrostructures achieves exceptional superelasticity. Adjusting volume fraction and unit cell size enables effective tuning of mechanical and mass transfer properties.

We use the three-phase sphere model or the generalized self-consistent scheme (GSCS) to study the mechanical damping of a particulate composite with concurrent interface slip and diffusion under a time-harmonic deviatoric far-field load. In particular, we determine the specific damping capacity characterizing the effective damping behavior in the particulate composite. Our results indicate that both interface slip and interface diffusion contribute to the specific damping capacity and effective storage shear modulus. Two peaks of the specific damping capacity can appear. The co-existence of interface slip and diffusion will enhance the maximum value of the specific damping capacity.

The specific damping capacity variation of heat-treated NiTi was observed during a pseudoelasticity test. The detailed B2 → R-phase transformation process in cold-drawn NiTi wires undergoing middle-temperature aging was studied via X-ray diffraction, transmission electron microscope, and internal friction technique. Results show that, as aging time increased at 450 °C, the dynamic phase transition splitting from B2 → R to B2 → R1 and B2 → R2 became evident. However, such a splitting process was not observed for the sample after aging at 400 °C. The reason for R-phase generation is attributed to non-uniformly distributed stress fields. The splitting of the internal friction peak, in conjunction with high-resolution transmission electron microscope and mechanic results, suggests a substantial occurrence of short-range segregation of Ni atoms in the B2-NiTi matrix. Furthermore, the specific damping capacity (SDC) exhibits a gradual increase with prolonged annealing time. Specifically, the sample with significant dynamic phase transition splitting reaches an SDC value of 0.60.

Аннотация. В статье представлены результаты анализа механического поведения механических слоистых конструкций с прослойками ауксетических метаматериалов при динамическом и квазистатическом нагружении. Данные конструкции могут быть использованы в облегченных конструкциях для гашения динамических нагрузок в транспортной и аэрокосмической технике. Элементы конструкций со слоями механических метаматериалов имеют низкую удельную массовую плотность и высокие удельные прочностные характеристики. Эти многослойные конструкции обладают высокой удельной способностью поглощать и рассеивать энергию внешних динамических нагрузок. Результаты численного моделирования реакции многослойных структур на динамические воздействия, полученные в данной работе, свидетельствуют о высоких удельных энергопоглощающих и диссипативных свойствах, позволяющих ослабить амплитуду импульса после прохождения слоистой системы и ослабить амплитуды колебаний. Полученные результаты указывают на возможность создания эффективных механически демпфирующих конструкций.

In this paper, an analytical model for the flexural vibration damping of Carbon Fiber Reinforced Plastics (CFRP) cantilever beams was proposed, which is based on the Lamination Theory and Euler–Bernoulli Beam Theory. By using a finite element analysis and an analytical model, four sets of specific damping capacity with different pavement schemes were predicted, and flexural vibration test and damping analysis were carried out. Comparing the analytical model, finite element analysis, and test results, it could be found that the analytical model had relatively good accuracy in predicting the first-order natural frequency and specific damping capacity of the bending vibration of CFRP beams. The maximum error of the first-order natural frequency between the analysis result and the experimental result was 7.05%; the maximum specific damping capacity error was only 5.65%. Comparing the finite element analysis method and the experiment results, the maximum error of the first-order natural frequency was 7.8%, the error of the specific damping capacity was bigger, and the [±30°]5S specimen was as high as 18.7%. However, there was a significant error when the analytical model was used to predict the second-order natural frequency and the specific damping capacity of CFRP beam’s flexural vibration.

We study the damping of thickly coated fibrous composites with viscous fiber-coating and coating-matrix interfaces under longitudinal shear loads. The specific damping capacity is derived by means of the three-phase composite cylinder model. Our analysis indicates that the specific damping capacity depends on six dimensionless parameters: the fiber and coating volume fractions, two stiffness ratios, and two interface parameters arising from rate-dependent interface sliding.

This paper investigates damping optimization design of variable-stiffness composite laminated plate, which means fibre paths can be continuously curved and fibre angles are distinct for different regions. First, damping prediction model is developed based on modal dissipative energy principle and verified by comparing with modal testing results. Then, instead of fibre angles, the element stiffness and damping matrixes are translated to be design variables on the basis of novel Discrete Material Optimization (DMO) formulation, thus reducing the computation time greatly. Finally, the modal damping capacity of arbitrary order is optimized using MMA (Method of Moving Asymptotes) method. Meanwhile, mode tracking technique is employed to investigate the variation of modal shape. The convergent performance of interpolation function, first order specific damping capacity (SDC) optimization results and variation of modal shape in different penalty factor are discussed. The results show that the damping properties of the variable-stiffness plate can be increased by 50%-70% after optimization.

Use of carbon nanotubes as additives to composite parts for the purpose of increased damping has been the subject of much recent attention, owing to their large surface area per weight ratio which provides for frictional losses at the carbon nanotube–resin matrix interface. This article presents an experimental study to quantify the structural damping in composites due to the addition of carbon nanotubes to thermosetting resin systems with and without fiberglass reinforcement. Carbon nanotubes of varying quantity and morphology are ultrasonically dispersed in epoxy resin and are compression molded to form test samples that are used in forced vibration, free vibration with initial tip deflection, and tension tests to determine their damping ratio, specific damping capacity, and Young’s modulus. Results show increased stiffness and specific damping capacity with the addition of carbon nanotubes and particularly increased frictional loss with increasing surface area to weight ratio. The addition of fiberglass reinforcement to composite samples is shown to reduce the effective damping ratio over plain epoxy samples and carbon nanotube-filled epoxy samples.