Dynamic Mechanical Analysis Method Research Articles

Characterization of viscoelastic properties of yarn materials: Dynamic mechanical analysis in the transversal direction

Abstract Warp knitting creates very challenging dynamics due to its high production speeds. On the one hand, this makes it method of choice for many products in various fields. On the other hand, not all materials are suitable for such high productivity. With the current generation of machines being limited to only achieve their maximum speed of around 4,400 min−1 with highly elastic yarns, it is desired to gain a deeper insight into yarn behavior in such highly dynamic environments. Among other influences, resonance effects gain high significance as they may result in high loads on the used materials; therefore, yarn breakages interrupt the production and decrease the quality of the product. To extend the material choice, especially high-performance fibers, for high productivity, a deep understanding of the intrinsic properties of the yarn is required. In particular, the viscoelastic properties are of importance. This study proposes a method to determine these characteristics using the dynamic mechanical analysis method. For the purpose of finding the damping in the transversal direction to the yarn axis, the variant of free oscillation is chosen. For the trials, a high-speed camera is suspended above a testing rig. On this rig, a yarn sample is clamped and then displaced from its rest position. The resulting oscillation is recorded and later extracted from the video. From the decrement of the maxima of the amplitude and corresponding time intervals, the damping factor is determined. It decreases with higher initial deflection. Summarised the developed trial setup proved suitable for the determination of the viscoelastic properties in transversal direction.

Determination of the ignorable boundary condition and standard sample for a novel in-situ dynamic mechanical analysis method on soft matter

An in-situ Dynamic Mechanical Analysis (DMA) method for soft matter developed by our group [Wu. et.al. 2022] encounters the problem of irregular samples, which significantly vary in shape and size in practice, therefore a standard sample “large enough” to ignore the boundary and size effects is necessary to determine the baseline of test and build the correspondence between this new method to classical mechanical tests. In this work, we use finite element analysis to approach the optimal size of a brick sample where the stress on the boundaries in three spatial directions are ignorable, and certified the results by testing a series of silicone gel samples on the in-situ DMA device. The stress-strain of tensile and compression are characterized. The material properties of gel are chosen to be close to the biological soft tissue. The size of 40mm(L)×40mm(W)×20mm(H) is determined to be the optimal result.

Structure, and Mechanical and Thermal Properties of Vinyl-Polydimethylsiloxane/Zinc Dimethacrylate/Isobutylene-Isoprene Rubber Composites

The vinyl-polydimethylsiloxane (v-PDMS) composite reinforced by micron size ZDMA particles previously showed high modulus, thermal stability, solvent-proofness, and good processing ability. However, its poor damping properties limited usages. Thus, incorporation of new polymers into the composite was imperative to improve its loss factors. With a similar solubility parameter and good damping properties, isobutylene-isoprene rubber (IIR) was melt-blended in, then heat-pressed and cross-linked. The v-PDMS/ZDMA/IIR composites gotten were characterized by scanning electric microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), mechanical tests, dynamic mechanical analysis (DMA) and thermal gravimetric analysis (TGA) methods. The IR spectra of the composites illustrated that the incorporation of IIR was successful. The SEM observation showed good dispersion of the IIR, and the increasing deformation on the surface with growing dosage of IIR. The incorporation of IIR rubber decreased the composite’s modulus sharply and also the tensile strength, but improved the elongation and damping properties of the v-PDMS/ZDMA composites at low temperature. The TGA test results in N2 gas showed the composites had good thermal stability below 350 °C, then deteriorated at higher temperature owing to the decomposition of the IIR at 400 °C. The decomposition activation energy at 400 °C was determined by the Kissinger method.

Measurements and estimation of frequency-dependent multi-scale viscoelastic damping properties of materials

The state-of-art viscoelastic property measurement and estimation methods at different frequencies/length scales inherently couple structural effects or sometimes lose accuracy for relevant parameters at smaller length scales in the material. We report a unified approach to measuring and estimating the frequency-dependent viscoelastic damping properties across different frequency scales independently of the specimen size effect and boundary conditions. The Dynamic Mechanical Analysis (DMA) method with three-point bending configuration is extended to higher-fidelity modeling in terms of time–frequency scales and material micro-mechanical scales together. The methodology demonstrates ways to identify the possible sources of undesired dynamics in the measurement process and eliminate those effects. It includes exciter tip contact dynamics in three-point bending configuration, anharmonic energy transfer to different frequencies (fractal bifurcation), and unmodelled artifacts or noise. Critically reviewing the standard DMA procedure with normal mode synthesis, this paper proposes a time–frequency Fourier spectral method that resolves a broader frequency range that extends to even acoustic/ultrasonic wave regimes of viscoelastic damping. An algorithm proposed in this paper with the advanced viscoelastic model with multi-parameters (standard linear solid model) estimates the fundamental material parameters at small length scales, which is more insightful to obtain a frequency-dependent correlation of material response to general dynamic loading. Stiffness and damping properties are estimated from measured data and validated for self-consistencies via different controls regarding static preload, specimen resonance, filtered noise, and model fidelity across the frequency range, and certain consistency and convergence properties of a series solution. The unified approach with a single test will be helpful in the design and evaluation of a wide variety of materials and their applications in vibration and acoustic problems. The proposed technique further demonstrates a novel way to extend low-frequency measurement to high-frequency response modeling.

Irradiation effects and photostability of aerosil-filled polyurethane as a matrix for laser solid-state elements

Photooxidation processes during irradiation of the aerosil-filled polyurethane films, based on oligooxypropylene glycol, toluene diisocyanate and trimethylolpropane, for a use as the active media of solid-state lasers were investigated by means of the IR-spectroscopy and dynamic mechanical analysis (DMA) methods, depending on the inorganic dopant concentration (5 and 7 wt%). The IR-spectroscopic experiments showed that the introduction of aerosil slowed down these processes. Data from dynamic mechanical studies indicated that irradiation of aerosil-filled polyurethane matrices caused an increase in its structural heterogeneity and a drop of the elastic modulus. During irradiation of the polyurethane material with 7 wt% of aerosil, a partial destruction of the nanofiller spatial network was possible due to dispersion of the irradiation energy by the nanoparticles. The obtained results demonstrated a positive effect of the aerosil nanofiller on the polyurethane material stability under irradiation with an ultra-high pressure mercury lamp.

Isothermal curing analysis and properties of ultra heat‐resistant polyimide composites by DMA method

AbstractThe isothermal curing process of T700 carbon fiber/P450 polyimide prepreg is characterized by dynamic mechanical analysis method and the gelation points are analyzed by torsional braid analysis theory. The growth mechanisms of the mechanical property at different constant temperatures are investigated by the relative mechanical growth rate of storage modulus and the curing kinetics models are established. The theories of Flory and Hsich are used to calculate the activation energy during the curing reaction of prepreg. The results indicates that the gelation times which are detected by the method of torsional braid analysis at 300, 310, 330, and 350°C were 293.7, 213.8, 104.1, and 45.4 min, respectively. The activation energies of curing reaction are calculated by Flory theory and Hsich theory, they are 112.35 and 119.96 kJ/mol, respectively. The feasibly of curing system 300°C × 4 h + 330°C × 2 h + 350°C × 2 h + 370°C × 2 h is verified by the mechanical properties and the heat resistance of polyimide composite.

Composite Films Based on Methyl Cellulose Mixtures with Poly(urethane-imide) Obtained from Their Solutions in Dimethylacetamide

Composite films of methyl cellulose and poly(urethane-imide) are obtained. At the poly(urethane-imide) content in the films above 50% phase separation of the polymers is observed. Using the methods of dynamic mechanical analysis and X-ray diffraction the structural organization of the films is studied, the temperatures of relaxation transitions are determined, and the mechanical characteristics of the composite films are investigated.

Contributing Factors of Uneven Climatic Aging for Polymeric Composite Materials: Methods and Modelling

Regarding a wide variety of PCMs, the materials' strength properties which decrease no more than 20% after 30 years of operation are of special interest. One of the important regularities of the climatic aging of PCMs is the formation of gradients of mechanical parameters across the thickness of the plates. The occurrence of gradients must be taken into account when modeling the strength of PCMs for long periods of operation. At present, there is no scientific basis for the reliable prediction of the physical-mechanical characteristics of PCMs for a long period of operation in the world of science. Nevertheless, "climatic qualification" has been a universally recognized practice of substantiating the safe operation of PCMs for various branches of mechanical engineering. In this review, the influence of solar radiation, temperature, and moisture according to gradients of mechanical parameters across the thickness of the PCMs are analyzed according to the data of dynamic mechanical analysis, linear dilatometry, profilometry, acoustic emission, and other methods. In addition, the mechanisms of uneven climatic PCM aging are revealed. Finally, the problems of theoretical modeling of uneven climatic aging of composites are identified.

Dynamic Characteristics of a Novel Right-Angle Viscoelastic Damper (RVD) Using Polyurethane Damping Materials

Excessive plastic deformation may occur at the beam-column joints under seismic action and lead to connection failure, increasing the possibility of collapse of the entire frame structure. In order to improve the seismic performance of assembled steel structure joints, a right-angle viscoelastic joint damper with polyurethane as the core energy dissipation material is proposed in this paper. First, the temperature scanning tests of polyurethane materials were carried out based on the dynamic mechanical analysis method. Second, the dynamic mechanical test and numerical simulation analysis of the designed right-angle viscoelastic damper were performed to reveal the dynamic energy dissipation characteristics of the right-angle damper. Finally, the dynamic time-history damping analysis was performed on the steel frame structure equipped with RVDs. The results show that the TA value of polyurethane material reached its peak at 2.0 Hz, which is the ideal frequency for the material’s damping ability. The right-angle damper made of polyurethane material has a softening nonlinear characteristic, and the peak value of the loss factor was obtained at 2.0 Hz, which is consistent with the results of the dynamic performance of the polyurethane material. The numerical simulation results demonstrate that stress on the steel plates and viscoelastic layers is reasonable. When the excitation level did not exceed 9 mm displacement amplitude, the energy input to the damper was dissipated by polyurethane, and the steel plates never showed plastic deformation. The time-history analysis of the steel structure shows that the dampers designed in this paper have a good control effect on the interstory displacement, acceleration, and interstory shear force of the structure. The research results lay the necessary foundation for the engineering application of polyurethane materials in the field of beam-column joints vibration damping.

Study of temperature fields in samples of polymer materials using dynamic mechanical analysis

The goal of the study is to reveal the dependence of the glass transition temperature on conditions of its determination. We present the results of studying temperature fields in the samples of polymer materials by the method of dynamic mechanical analysis. Changes in the glass transition temperature of the poly­mer casting VSE-34 and the temperature profile in the polymer matrix ED-20/DAFS were analyzed. Stan­dard melting samples were used to correct the test results using the correction function. It is shown that the most significant temperature deviations are observed when measured in argon and helium media with heating rates of 1, 2, 5, and 5 K/min. The temperature distribution over the polymer casting sample is highly non-uniform. The difference between the temperature in the middle and at a distance of 1/4 from the edge of the sample equals 16°C (medium — argon, heating rate — 5 K/min). Moreover, at a heating rate of 1 K/min, abnormally low values of the glass transition index were marked. The results obtained can be used to improve the measurement procedure, reduce test duration and refine the results of tests in various gaseous media.

Послойный динамический модуль сдвига в поперечном сечении древесностружечной плиты

The research results are aimed at the formation of ideas concerning the features of molecular motion of the components of the outer and inner layers of the particle board material in the temperature range from room temperature to 275–300 °C, as well as at revealing the fact of binder undercuring in the inner layers. The paper provides data on the temperature dependences of the dynamic shear modulus of the outer and inner layers of the particle board material, obtained by dynamic mechanical analysis using a torsion pendulum. We found significant differences in the nature of the dependencies for samples taken at different distances from the surface layers. The material of the outer layers is characterized by the typical pattern of a continuous irregularly consistent decrease in the dynamic shear modulus with increasing temperature, which is common to most polymeric and composite materials. A short-term intermittent increase in the dynamic shear modulus relative to neighboring areas was detected in the inner layers at 140±5 °C, which is not typical for materials in a stable state. There is also a tendency for the dynamic shear modulus of the particle board material to decrease at room temperature with distance from the outer layers, due to the heterogeneous fractional composition and differences in the nature of chemical cross-linking during hot pressing. It has been assumed that the detected anomalous increase in the dynamic shear modulus in the inner layers of the material at 140±5 °С is a symptom of the binder post-treatment process directly in conditions of its heating when measuring the dynamic shear modulus by dynamic mechanical analysis. Thus, it is concluded that the particle board sample shows maximum curing of the thermosetting binder in the layers, which are 4.5–5.0 mm distant from both surfaces. Partial undercuring of the binder occurs in the inner layers, which are more than 5.5 mm away from the surfaces. Thus, it is shown that the method of dynamic mechanical analysis can be used as a tool to control the presence in the inner layers of the particle board material of the components of thermosetting binder, undercured in the hot pressing process, which will help to obtain a material with more stable characteristics.

Long-Term Performance Evolution of RIOHTrack Pavement Surface Layer Based on DMA Method.

Asphalt mixture is a typical viscoelastic material, and its road performance will change with the action of environment and load during actual service. This study conducted experimental research on the surface course asphalt mixture of three categories and six typical structures of RIOHTrack based on the Dynamic Mechanical Analysis method. Moreover, this study explored the performance evolution law of asphalt mixture under the coupling action of load and environment in the process of loading from 0 million to 54 million standard axle times. Results demonstrated that the phase transition characteristic temperature of the surface course materials of the three types of typical structures showed a trend of first increasing and then decreasing with the accumulation of load and environmental effects, indicating the presence of two stages of the dual coupling effect of environmental aging and load rolling on the asphalt mixture during service. In addition, the results suggested that the phase transition characteristic temperature, modulus, and phase angle of the surface layer materials have obvious material differences and structure dependencies.

Local deformation on damping performance of integral-forming aluminum foam sandwich

Damping performances of porous metals are generally measured by dynamic mechanical analysis (DMA) method which has strictly dimensional requirements on specimens especially on their thickness. In this work, based on sinusoidal excitation and Fourier transform, a new set of test equipment suitable for evaluating damping performances of large-scale porous metals was constructed. On this basis, the influence of local compression deformation on the damping performances of the newly developed integrated-forming aluminum foam sandwich (IFAFS) was investigated by means of single-point excitation method. Damping performances of different regions were obtained through partition measurement and the reasons were discussed which are beneficial to evaluate damping performances of IFAFS after local deformation.

An experimental investigation on the thermal and mechanical characterization of boron/flax/PLA sustainable composite

The current study deals with the effect of boron compounds, zinc borate (ZB), borax: boric acid combines (BxBc), and ulexite which are used to improve fire resistance, on the thermal, microstructural, and mechanical properties of the flax/PLA biocomposites. For this purpose, the mechanical properties of the biocomposites were determined by tensile, impact, and three-point bending tests. Thermogravimetric analysis and the UL-94 burn test were conducted to determine the thermal properties of composites, such as thermal stability and flammability. Thermo-mechanical properties and viscoelastic characteristics of biocomposites were determined by the dynamic mechanical thermal analysis method. Test results showed that ulexite addition could significantly reduce the burning rate by 80%. However, although mechanical properties were adversely affected by the incorporation of boron compounds resulting in a drop of up to 20%, it is believed that boron compound-filled flax/PLA composites have mechanical and thermal properties that can be considered as an alternative material, especially for the automotive industry.

Damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders with different thicknesses and preparation directions

PurposeThis study aims to experimentally assess the effect of thickness and preparation direction on the damping properties of Sn58Bi and Sn3.0Ag0.5Cu solders.Design/methodology/approachSn58Bi and Sn3.0Ag0.5Cu solder strips with different thicknesses were prepared from the bulk in longitudinal and horizontal directions, and the ratio of loss modulus and storage modulus of the samples was measured by the dynamic mechanical analysis method as the index of damping properties.FindingsSn58Bi and Sn3.0Ag0.5Cu solders exhibited viscoelastic relaxation, and their damping properties decreased with decreasing thickness. The damping properties of both solders had no obvious difference in longitudinal and horizontal directions. Sn58Bi has a more obvious high-temperature damping background than Sn3.0Ag0.5Cu solder. In addition, compared with Sn58Bi solder, Sn3.0Ag0.5Cu solder had an obvious internal friction peak, which moved toward high temperature with increasing frequency. The activation energies of Sn58Bi solder with a thickness of 0.5 mm at the longitudinal and horizontal directions were 0.84 and 0.67 eV, respectively, which were 0.39 and 0.53 eV, respectively, for the Sn3.0Ag0.5Cu solder.Originality/valueThe damping properties of Sn58Bi and Sn3.0Ag0.5Cu solder decreased with decreasing thickness, while their damping properties changed insignificantly when they were prepared from different directions. The internal friction peak of Sn3.0Ag0.5Cu solder moved to higher temperatures with increasing frequency.

In-situ reaction compatibilization modification of poly(butylene succinate-co-terephthalate)/polylactide acid blend films by multifunctional epoxy compound

Poly(butylene succinate-co-terephthalate) (PBST) copolyester, is a new type of biodegradable synthetic polymer material that has emerged in recent years, but it cannot meet the market requirements, because of its low strength. The high-strength and high-modulus polylactic acid (PLA) was blended with PBST to increase its strength, and the chain extender ADR-4370 was used to modify PBST/PLA films by reaction and compatibilization. Compared with the 80/20 wt% PBST/PLA films, the tensile strength after modification with 0.3 wt% ADR was increased by 21.8 % and 44.3 % in the machine direction (MD) and in the transverse direction (TD), respectively. The Water Vapor Permeability (WVP) was decreased from 10.0 × 10−14 to 3.09 × 10−14 g·cm/cm2·s·Pa. The compatibilization mechanism was studied by gel permeation chromatography, infrared spectroscopy, dynamic mechanical analysis, rheological analysis, and other characterization methods. The formation of the copolymer PLA-g-PBST is the most important factor to improve the compatibility of the system and the mechanical properties of the films.

Evaluation of the High- and Low-Temperature Performance of Asphalt Mortar Based on the DMA Method

Asphalt mortar is a typical temperature-sensitive material that plays a crucial role in the performance of asphalt mixture. This study evaluates the high- and low-temperature performance of asphalt mortar based on the dynamic mechanical analysis (DMA) method. Temperature-sweep tests of asphalt mortars were conducted using the DMA method under fixed strain level, frequency, and heating rate conditions. The dynamic mechanical response curves, characteristic temperature, and other indices were obtained and used to investigate the high- and low-temperature performance of asphalt mortar. The results showed that the phase transition temperatures T1, T0, and Tg can be used to evaluate the low-temperature performance of asphalt mortar. Additionally, they had a good linear relationship, and the evaluation results were consistent. Meanwhile, T2, E60, and tan(δ)max indicators can effectively evaluate the high-temperature performance of asphalt mortar. Asphalt plays a key role in the performance of asphalt mortar. Mortars with neat asphalt A70 and modified asphalt AR had the worst and best high- and low-temperature performances, respectively. Furthermore, the finer gradation improved the low-temperature performance of asphalt mortar, while the coarser gradation improved the high-temperature properties of modified asphalt mortars but had the opposite effect on neat asphalt A70.

The Effect of Agglomeration on the Electrical and Mechanical Properties of Polymer Matrix Nanocomposites Reinforced with Carbon Nanotubes.

In this work, we investigated the effect of carbon nanotubes addition and agglomeration formation on the mechanical and electrical properties of CNT–polymer-based nanocomposites. Six specimens with carbon nanotubes (CNTs) fractions of 0%, 0.5%, 1%, 2%, 4% and 5% were manufactured and characterized by dynamic mechanical analysis (DMA) and four-probe method. The stress–strain curves and electrical conductivity properties were obtained. Scanning electron microscopy (SEM) was used to characterize both agglomeration and porosity formation. By employing micromechanics, through representative volume element (RVE), finite element analysis (FEA) and resistor network model (RNM), the Young’s modulus and electrical conductivity values were calculated. The samples’ elastic moduli showed an increment, reaching the maximum value at a CNTs fraction of 2%, thereafter an adverse effect was caused in the high CNT percentage samples. The final electrical conductivity seemed greatly altered with the addition of CNTs, reaching the percolation threshold at 2%. The unavoidable formation of CNT agglomerates appeared to influence the final physical properties. The CNT agglomerates adversely affect the mechanical performance of high-CNT-percentage samples. Conversely, an exponential increment in the electrical conductivity was presented as the agglomerates formed networks allowing the transport of electrons through the tunnelling effect. These phenomena were experimentally and numerically confirmed, showing a good correlation.

Structure–property relationships and constitutive viscoelastic behaviors of polyether‐block‐amide elastomers in melt and solid states

AbstractIn this study, effects of copolymer composition on the structural, thermal, and viscoelastic properties of segmented multi‐block polyamide elastomers (PEBAX® 3533, 5533, and 6333) and polyamide‐12 (PA12) were quantified by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, and dynamic mechanical analysis (DMA) methods and rheological measurements. Soft segment, poly(tetramethylene oxide) (PTMO), contents of copolymers were proved by FTIR analysis. It was found that the increase in PTMO content dramatically reduced the crystallization and melting temperatures and degree of crystallinity values of copolymers. Different rheological test protocols performed in melt state revealed that zero shear rate viscosity values of polyamide elastomers increased with the increasing amount of hard segment. On the other hand, increase in hard segment content yielded lower flow activation energy value. In this study, we mainly focused on understanding quantitative relationships between block copolymer structure and their rheological behaviors and found that the soft segment content of ~40 (mole %) is the critical point for changing the rheological behaviors of block copolymer PAEs, dramatically. DMA measurements implied that the solid‐state viscoelastic behaviors of samples were governed by the hard content of copolymers. Higher hard content decreased long‐term creep strain and creep rate.

The Effect of Starch and Magnetite on the Physicochemical Properties of Polyurethane Composites for Hyperthermia Treatment

In this study, modified polyurethanes (PUs) with starch and magnetite were synthesized in the form of scaffolds for potential applications in orthopedics. Polyurethanes were synthesized using a one-step method. PU synthesis was carried out using poly(ε-caprolactone) 2000 as soft segments and 4,4 ′ -methylenediphenyl diisocyanate (MDI). Various molar ratios of starch and 1,5-pentanediol (PDO) as crosslinker/chain extender were applied, and the effects of incorporating different amounts of magnetite, as well as the role of PDO to starch ratio, were studied. The use of the additive in the form of magnetic particles was to feature the polyurethane materials for use in hyperthermia. The prepared polyurethanes were investigated using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), and dynamic mechanical analysis (DMA) methods. Scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) analysis and preliminary bioactivity assessment were also performed. The addition of magnetic particles did not cause significant changes in the properties of the obtained materials compared to starch. The tested materials have the potential to be used to fill or replace bone defects in orthopedics, where they can undergo hyperthermia treatment.