Williams Landel Ferry Research Articles

Numerical and Experimental Investigations of Polymer Viscoelastic Materials Obtained by 3D Printing.

The aim of this research is to determine the relaxation and creep modulus of 3D printed materials, and the numerical research is based on the finite volume method. The basic material for determining these characteristics is ABS (acrylonitrile butadiene styrene) plastic as one of the most widely used polymeric materials in 3D printing. The experimental method for determining the relaxation functions involved the use of a creep test, in which a constant increase of the stress of the material was performed over time to a certain predetermined value. In addition to this test, DMA (dynamic mechanical analysis) analysis was used. Determination of unknown parameters of relaxation functions in analytical form was performed on the basis of the expression for the storage modulus in the frequency domain. The influence of temperature on the values of the relaxation modulus is considered through the determination of the shift factor. Shift factor is determined on the basis of a series of tests of the relaxation function at different constant temperatures. The shift factor is presented in the form of the WLF (Williams-Landel-Ferry) equation. After obtaining such experimentally determined viscoelastic characteristics with analytical expressions for relaxation modulus and shift factors, numerical analysis can be performed. For this numerical analysis, a mathematical model with an incremental approach was used, as developed in earlier works although with a certain modification. In the experimental analysis, the analytical expression for relaxation modulus in the form of the Prony series is used, and since it is the sum of exponential functions, this enables the derivation of a recursive algorithm for stress calculation. Numerical analysis was performed on several test cases and the results were compared with the results of the experiment and available analytical solutions. A good agreement was obtained between the results of the numerical simulation and the results of the experiment and analytical solutions.

Evaluation for Low Temperature Performance of SBS Modified Asphalt by Dynamic Shear Rheometer Method

Finding an alternative or supplementary test method to evaluating the low temperature performance of asphalt is an area of considerable interest. This paper tries to explore the possibility of using the dynamic shear rheometer (DSR) method for assessing the low temperature properties of styrenebutadienestyrene (SBS) modified asphalt. In the study, 60/80 and 80/100 pen grade asphalt binders, named binder A-70, binder B-70 and binder C-90, are used to produce the SBS modified asphalt samples. After that, the low temperature performance of the asphalt binders is characterized by using bending beam rheometer (BBR) test. The results indicate that the low temperature performance of the different binders is related to the source of the binder. The low temperature performance of asphalt could be improved with the addition of the SBS. The DSR test is used to develop the complex modulus master curves for binders. Based on the principle of time–temperature conversion, the glass transition temperature of asphalt is calculated by the Williams–Landel–Ferry (WLF) equation. The glass transition temperatures (Tg) of base asphalt and the SBS modified asphalt are determined by the viscoelastic parameters of the master curve and the WLF equation coefficients based on the time–temperature superposition principle. By establishing the relationship between the critical temperature and the Tg of the asphalt binder, the effectiveness of the method established in this paper is verified. The advantage of this method is the ability to use the DSR test for the rapid evaluation of the low temperature performance of asphalt, which is able to reduce testing materials and save testing time as well. The glass transition temperature of the SBS modified asphalt is closely associated with aging degree, asphalt source and the SBS content.

The Relationship between Free Volume and Cooperative Rearrangement: From the Temperature-Dependent Neutron Total Scattering Experiment of Polystyrene.

Although many theories have been proposed to describe the nature of glass formation, its microscopic picture is still missing. Here, by a combination of neutron scattering and molecular dynamics simulation, we present the temperature-dependent atomic structure variation of polystyrene at the glass formation, free volume and cooperative rearrangement. When it is close to glass formation, the polymer is confined in tubes, whose diameter is the main chain–main chain distance, in a “static cage” from its neighbors. This definition can not only account for the kinetic pathway dependence of Williams-Landel-Ferry (WLF) free volume, but also be testified in a set of six polymers. However, the free volume which allows a monomer to move cannot be found in any frame of its real-space image. Monomers, thus, have to move cooperatively to be out of the cage. During glass formation, dynamic heterogeneity develops, and string-like cooperative rearrangement region (CRR) grows over a long range of time and length scales. All of these CRRs tend to walk through loose “static cages”. Our observation unifies the concepts of free volume and cooperative rearrangement. The former is a statistical average leading to a polydisperse “static cage” formation; while a loose “static cage” provides the way that CRRs move.

Dynamic modulus master curve construction of asphalt mixtures: Error analysis in different models and field scenarios

Asphalt mixture stiffness is a key property in any pavement long-life performance analysis; it is used to predict a material’s strain response for any given applied stress. To accurately describe experimental data, different mathematical models have been reported in literature, which allow for extrapolation to ranges not evaluated in laboratory tests. However, a precision analysis comparing each of them is necessary. This study evaluated 50 data points from five temperatures, ten loading frequencies, and 48 different asphalt mixtures to construct dynamic modulus master curves. Sigmoidal, Christensen-Anderson-Marasteanu (CAM), and Havriliak-Negami (HN) models were calibrated with three different target error functions, in addition to 2 Springs, 2 Parabolic creep elements, and 1 Dashpot (2S2P1D) to analyze their relative and absolute errors. In the first part, the mechanical analogs (2S2P1D and HN) achieved the best results. In the second part, the error added by the Williams-Landel-Ferry (WLF) and polynomial function, which describe the time–temperature shift factors used to construct the dynamic modulus master curves, was calculated; this suggested that the polynomial function better fits the master curves’ shift factors. In the third part, three Enhanced Integrated Climate Models (EICM) with different pavement depths and temperatures throughout the year together with the influence of vehicle speed and a depth equation were used to meet a reduced frequency interval that represents practical field conditions. Therefore, by filtering the errors found in part one using the field-representative reduced frequency interval, the fitting models (based on regression adjustments) can reach lower error levels closer to those of the mechanical analog models although still greater than those of the 2S2P1D model. In summary, it is possible to obtain a reliable pavement stiffness prediction using a less robust model as long as the dynamic modulus tested database is wide enough to express the desired reduced frequency range. Nevertheless, the use of a mechanical approach model such as 2S2P1D better describes the dynamic modulus experimental results, which leads to a more reliable prediction in addition to enabling characterization of the rheological behavior of asphalt materials.

Characterization of viscoelastic bending stiffness of uncured carbon-epoxy prepreg slit tape

In support of computational modeling of tow placement at elevated temperature, the creep response of IM7/8552 uncured prepreg slit tape material during 3-point bend loading at different temperatures is measured using an RSA III dynamic mechanical analyzer. Short term creep experiments were conducted for a duration of 1000 s at ten different temperatures ranging from −5°C (below Tg of 0 °C) to 40 °C, with the latter being the nominal processing temperature for the tow. Results show that the tow material obeys the time-temperature superposition principle (TTSP) in the temperature range selected for the creep experiments. Using the TTSP, creep compliance master curve spanning more than eight logarithmic decades is obtained for the nominal processing temperature of 40 °C. The time–temperature shift factor is observed to follow closely the William-Landel-Ferry (WLF) model, with the WLF parameters obtained by least square fitting of the experimentally determined shift factors utilizing closed form shifting algorithm (CFS). The WLF model for the material is used to extend the master curve to a range of temperatures above glass transition temperature (Tg) of the material. The creep compliance data is further employed to obtain the retardation spectra of the material using an algorithm based on the work of a co-author and applied recently to a different material system by the authors. Details for extraction of the retardation spectra from the creep compliance results are provided. Results from these studies demonstrate that the creep compliance reconstructed from the retardation spectra accurately represent the experimental results while providing baseline data to quantify the importance of viscoelastic behavior in wrinkle formation during advanced manufacturing of aerospace components.

Temperature‐dependent viscosity of bio‐oil derived from white pine and Norway spruce needles

AbstractViscosity plays a significant role in the utilization of bio‐oil as a liquid transportation fuel. This study investigated the influence of temperature on the viscosity of bio‐oils derived from white pine and from Norway spruce needles. The bio‐oils were produced by pyrolyzing the biomass samples in a fixed‐bed batch reactor at a temperature of 500 °C for 30 min. The viscosity of the bio‐oils was determined at a temperature range of 20–80 °C. The bio‐oil yield was estimated to be 36.32% and 28.84% for white pine and Norway spruce needles, respectively. The viscosity of bio‐oils derived from white pine and Norway spruce needles decreased from 177.67 to 54 cP and from 161.17 to 37.67 cP, respectively, as the temperature increased from 20 to 80 °C. Among the three models (Arrhenius, modified Williams–Landel–Ferry, and the power law) used to describe the temperature‐viscosity relationship of the bio‐oils, the Arrhenius model presented the best fit for the experimental data with activation energy of 16.80 and 20.79 kJ/mol–1 for bio‐oils derived from white pine and Norway spruce needles, respectively. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Hydroxyethylresorcinol- and hydroxyethylhydroquinone-containing poly(ethylene terephthalate) copolymers

Melt polycondensation incorporating meta-substituted hydroxyethylresorcinol (HER) or para-substituted hydroxyethylhydroquinone (HEH) regioisomers enabled the synthesis of poly(ethylene terephthalate) (PET)-based (co)polyesters with targeted comonomer mol %. Incorporation of either HER or HEH lowered the glass transition temperature (Tg) relative to PET, but the 5% weight loss temperature (Td,5%) remained unchanged. Similarly, the semi-crystalline morphology varied as a function of comonomer selection and mol % comonomer. Dynamic mechanical analysis confirmed decreasing β-relaxation intensities upon HER and HEH incorporation, while HER impacted β-relaxation intensity more substantially at similar mol %. HER incorporation also shifted the β-relaxation temperature (Tβ) to lower temperatures considerably more than HEH. Time-temperature-superposition (TTS) and Williams-Landel-Ferry (WLF) analysis of melt rheology probed various physical polymer properties including melt flow activation energy (Ea), fractional free volume at Tg (fg), and molecular weight of entanglement (Me). HER-based (co)polyesters exhibited lower Ea compared to HEH. Likewise, HER incorporation lowered fg while HEH incorporation increased fg. HER-based (co)polyesters possessed a higher Me compared to HEH-based (co)polyesters, although both copolymers resulted in higher Me compared to PET. Tensile testing revealed HER/HEH-based (co)polyesters ultimate mechanical performance compared to amorphous PET. Both HER and HEH incorporation increased Young's moduli and yield strengths, although comonomer incorporation above 25–30 mol % yielded minimal change. Establishing structure-property relationships provided insight into the role of regioisomeric variation at various comonomer levels on thermal, rheological, and mechanical performance for PET-based copolymers.

A novel rapid cure epoxy resin with internal mold release

AbstractMold preparation, material layup, and cure times for thermoset‐based composites often limit their use in high‐volume applications. As such, new rapid cure epoxy resins are being developed to achieve a complete cycle time within 3 min. In this research, calorimetry and rheometry are used to examine and model two novel rapid cure epoxy resin systems with internal mold release. The rapid cure epoxy resins followed an autocatalytic cure kinetic and William–Landel–Ferry diffusion model. The rapid cure epoxy resin was shown to achieve 94% cure in 2 min at 150°C. However, adding an additional 2.5 wt% internal mold release hindered the first step of the reaction, which delayed the second reaction step since the final degrees of cure were similar. Furthermore, the resin viscosity followed a modified William–Landel–Ferry equation and at 120°C could maintain a viscosity below 5 Pa s for 4.1 min. These models provided valuable insight into the range of processing conditions these novel resins could experience during impregnation and molding processes.

Rheology of Conjugated Polymers with Bulky and Flexible Side Chains

We report on the linear viscoelasticity of dialkylfluorene- and dialkoxybenzene-based viscoelastic conjugated polymers at a wide temperature range. Three dynamic transition temperatures are probed on the rheological spectrum, which are ascribed to the backbone (Tg,bb), the inner side chain (Tsc,inner), and the outer side chain (Tsc,outer), respectively. For our polymers that contain long branched side chains, their Tg,bb values deviate from the prediction based on atomic mobility. Tsc,outer is independent of chemical structures, while Tsc,inner is in between Tg,bb and Tsc,outer. A universal William–Landel–Ferry fitting could describe the dynamic temperature dependence of backbones for different polymers at an iso-free-volume state, while the dynamics of side chains exhibit two steps of Arrhenius behavior, corresponding to motions of inner and outer side chains, respectively. The activation energy of inner side chains monotonically decreases with the increasing side chain fraction, while that of outer side chains is independent of chemical structures.

Mechanical Testing and Modeling of the Time-Temperature Superposition Response in Hybrid Fiber Reinforced Composites.

The purpose of this study was to manufacture hybrid composites from fabrics with superior ballistic performance, and to analyze their viscoelastic and mechanical response. Therefore, composites in hybrid lay-up modes were manufactured from Vectran, Kevlar and aluminum fiber-woven fabrics through a vacuum assisted resin transfer molding. The specimens were consequently analyzed using static three-point bending, as well as by dynamic mechanical analysis (DMA). Apart from DMA, time–temperature superposition (TTS) analysis was performed by all available models. It was possible to study the intrinsic viscoelastic behavior of hybrid ballistic laminates, with TTS analysis gained from creep testing. A polynomic mathematical function was proposed to provide a high accuracy for TTS curves, when shifting out of the linearity regimes is required. The usual Williams–Landel–Ferry and Arrhenius models proved not useful in order to describe and model the shift factors of the acquired curves. In terms of static results, the highly nonlinear stress–strain curve of both composites was obvious, whereas the differential mechanism of failure in relation to stress absorption, at each stage of deformation, was studied. SEM fractography revealed that hybrid specimens with Kevlar plies are prone to tensile side failure, whereas the hybrid specimens with Vectran plies exhibited high performance on the tensile side of the specimens in three-point bending, leading to compressive failure owing to the high stress retained at higher strains after the maximum bending strength was reached.

Mutual diffusion of proteins in cold concentration gradients measured by holographic interferometry

Protein mutual diffusion in cold concentration gradients is important for development of processes involving biopharmaceutical formulations. The diffusivities of α-chymotrypsinogen (aCgn), ovalbumin (Ova) and IgG1 were measured from −10 °C to 25 °C, by holographic interferometry at protein concentrations ranging from 5 g/L to 31.5 g/L in multicomponent systems containing sucrose (up to 10% mass). A dialysis step enabled to measure mutual diffusion of the proteins under equi-chemical potential conditions of the other components. The protein could therefore be considered a single component in a continuous fluid, as defined by Stokes-Einstein (SE) assumption. Overall, the SE model provided a reasonable description for mutual diffusion of all the proteins studied, with higher accuracy for aCgn and IgG1 in the full range of temperatures and concentrations. Ova with 10% sucrose, was less accurately described by this model, diffusing 20% faster than predicted. It was also observed a non-linear temperature dependence for the diffusion of Ova in a 10% sucrose medium: this was only apparent at a temperature near −10 °C. The Williams Landel Ferry (WLF) model was used to provide a measure of the non-Arrhenius regime taken the glass transition temperature (Tg) of the mixture Ova+ sucrose as reference (WLF constants obtained are C1,g ~ 18 and C2,g ~ 1). Overall, the present work offers a new approach to obtain experimental diffusion coefficients of relevant protein formulations under sub-zero conditions. The accuracy of classical transport models was explored in this manuscript which can help to gather insight into transport properties of globulins and Mabs under concentration polarization gradients occurring during freezing: deviations to the linear diffusion-temperature relation above Tg – i.e., “continuous medium” diffusion predicted by SE model - can be quantified by the WLF model. Diffusion coefficients may be further related with protein conformational changes and this was proposed for Ova.

Rouse Mode Analysis of Relaxation in Polymer Blends

AbstractThe relaxation spectra of the components in polymer blends determine the dynamic mechanical properties of the corresponding composite materials, which, in thermo‐rheological studies, show a delicate dependence on their chemical and physical properties as well as its bulk composition. A molecular dynamics simulation based Rouse mode analysis is performed to detect the relaxation spectra of the component chains on all length scales ranging from one monomer to the whole chain size, indicating that the bulk composition dominates the relaxation dynamics of the components in miscible polymer blends. The relaxation of component chains accelerates on all length scales as increasing the free volume available to monomers to move, with the dependence of mobility shift on composition being quantified by a Williams–Landel–Ferry like function governing the time‐composition superposition. Role of the chain connectivity induced self‐concentration effect on chain relaxation in polymer blends is discussed and proved to be limited, which leads to a visible but subtle length‐scale dependent rheological complexity as the composition is varied.

Experimental Study on Dynamic Properties of a Recycled Composite Sleeper and Its Theoretical Model

As a symmetrical structure in track system, the dynamic properties of recycled composite sleepers are important factors affecting the vibration characteristics of track structure. To study the viscoelastic dynamic properties of the composite sleeper, dynamic mechanical analysis (DMA) tests of a composite sleeper at −5 to 30 °C and 1–60 Hz were first carried out, and then the time-temperature superposition (TTS) and the Williams–Landel–Ferry (WLF) formula were used to predict the dynamic properties of a composite sleeper at a wider frequency range. Finally, the generalized Maxwell model was adopted to characterize the dynamic properties of the composite sleeper, which provides parameters and theoretical models for dynamic analysis. The research results show that the composite sleeper has obvious viscoelasticity. Its modulus is large at low temperature or high frequency. On the contrary, the modulus is small at high temperature or low frequency. Under the test conditions, its complex modulus ranges from 1500 to 2700 MPa. The loss factor is in the range of 0.08–0.13. Using the generalized Maxwell model (n = 4), which can better reflect the dynamic properties of the composite sleeper.

Understanding complex dynamics of interfacial reconstruction in polyampholyte hydrogels undergoing mechano-chemo-electrotaxis coupling

Polyampholyte (PA) hydrogels have attracted significant attention for their superior mechanical strength and toughness compared with other conventional hydrogels. In this study, we present a novel thermodynamic approach to understanding the mechano-chemo-electrotaxis coupling and interfacial dynamics in PA hydrogels. Flory–Huggins theory, carried out through an interfacial free-energy model, is the foundation for the quantitative study of the mechanically constitutive relationship of the PA gels. The proposed free-energy model is further extended to describe the mechano-chemo-electrotaxis switching and interfacial dynamics by co-relating the Williams–Landel–Ferry equation and scaling laws. It was concluded that the interfacial bonding strength is the key factor influencing the mechanical strength and reconstruction reversibility of the PA macromolecular gel system. The resulting analytical outcomes showed good agreement with the reported experimental data. We opine that the proposed model will guide the future application of PA hydrogels.

Crystallization and strength analysis of amorphous maltose and maltose/whey protein isolate mixtures.

Maltose is an essential derivative of starch. To understand the processability and stability of maltose-containing foods, material characterization of the phase and state transition from its amorphous state is required. Although the crystallization of amorphous maltose is well understood, few studies have reported the relationship between the crystallization and the glass transition temperature (Tg )-related molecular mobility. In this study, water sorption, crystallization, Tg -related α-relaxation, and the corresponding time factor for amorphous maltose and maltose / whey protein isolate (WPI) mixtures are measured at various water activity (aw ) levels and 25 °C. The water-additive principle for maltose / WPI mixtures was observed at aw ≤ 0.440 at the molecular level, whereas the crystallization of amorphous maltose occurred at high aw values (≥0.534). The crystal formation and crystallization kinetics of amorphous maltose were affected by water and WPI at aw ≥ 0.534 and 25 °C, as determined by X-ray diffraction. The relationship between Tg and the water content was fitted by the Gordon-Taylor model, and its constant showed a compositional dependence for the maltose / WPI mixtures. The α-relaxation temperature of the amorphous samples decreased due to water plasticization, but increased with an increase in the WPI quantity. The Strength (S) value for amorphous maltose, which was a quantitative estimate of the compositional effects on molecular mobility, was based on the William-Landel-Ferry (WLF) equation. The S concept exhibits considerable potential for application in controlling the crystallization of amorphous maltose and improving the processability and stability of maltose-containing foods. © 2020 Society of Chemical Industry.

Rheology of carbohydrate blends close to the glass transition: Temperature and water content dependence of the viscosity in relation to fragility and strength

Several modifications of the Williams-Landel-Ferry (WLF) equation that incorporate the water-content dependence of the viscosity are introduced and applied to the fitting the zero-shear viscosity of a systematic series of maltopolymer-maltose blends for water contents w between 4% and 70% (M. Dupas-Langlet et al., Carbohydrate Polymers 213 (2019) 147–158). These models include a previously published model that addresses the water-content dependence of the viscosity via a Gordon-Taylor-type modification of the C2 coefficient of the WLF equation. New models that are based on two simple assumptions are introduced: 1. The viscosity at the glass transition temperature Tg decreases exponentially with the water content and 2. The WLF coefficient C2 depends linearly on the water content. The modified WLF models allow to extract the so-called isoviscosity lines, that connect points of varying temperature and water content that are characterized by the same viscosity. Based on data obtained between T = −15 °C and 70 °C using shear rheology (w = 30–70% w/w) and dynamic mechanical thermal analysis (w = 4–9% w/w), we conclude that the models provide a good fit of the experimental data, and that additional data, specifically very close to the glass transition line, is needed, to assess the hypotheses underlying the various modified WLF models. It is established that the viscosity at Tg is dependent on the composition and decreases with the content of maltose and water. The modified WLF models are used to determine Angell’s fragility parameter m and Roos’ strength parameter S. m and S are observed to increase, respectively decrease with increasing water and maltose content, signifying an increasing temperature dependence of the viscosity close to Tg with decreasing diluent content. The application of the isoviscosity concept to unit operations in the food and pharmaceutical industry is discussed. Specifically, we show how to analyze atomization, agglomeration, sintering and compaction using the isoviscosity concept.

Lifetime Prediction Methods for Degradable Polymeric Materials-A Short Review.

The determination of the secure working life of polymeric materials is essential for their successful application in the packaging, medicine, engineering and consumer goods industries. An understanding of the chemical and physical changes in the structure of different polymers when exposed to long-term external factors (e.g., heat, ozone, oxygen, UV radiation, light radiation, chemical substances, water vapour) has provided a model for examining their ultimate lifetime by not only stabilization of the polymer, but also accelerating the degradation reactions. This paper presents an overview of the latest accounts on the impact of the most common environmental factors on the degradation processes of polymeric materials, and some examples of shelf life of rubber products are given. Additionally, the methods of lifetime prediction of degradable polymers using accelerated ageing tests and methods for extrapolation of data from induced thermal degradation are described: the Arrhenius model, time–temperature superposition (TTSP), the Williams–Landel–Ferry (WLF) model and 5 isoconversional approaches: Friedman’s, Ozawa–Flynn–Wall (OFW), the OFW method corrected by N. Sbirrazzuoli et al., the Kissinger–Akahira–Sunose (KAS) algorithm, and the advanced isoconversional method by S. Vyazovkin. Examples of applications in recent years are given.

Morphology and viscoelastic properties of UV cured-polyurethane acrylate/silicon carbide nanocomposites

The viscoelastic properties of semi-conductive UV cured urethane acrylate/silicon carbide nanocomposites (UV-PUA/SiC) containing 0.1, 0.3, 0.6, 1, 3, and 5% (wt) of SiC are studied. Scanning electron microscopy (SEM) was employed to examine the state of the spatial distribution of SiC particles in the matrix. In conjunction with the electron microscopy technique, dynamic mechanical thermal analysis (DMTA) was employed as an indirect tool for the microstructure characterization and evaluation of the network heterogeneity and cross-link density of the nanocomposites. The influence of SiC nanoparticles on the storage modulus, loss modulus, cross-link density, glass transition temperature, and activation energy for glass transition of the UV-PUA matrix are investigated. The effect of SiC content on the network structures and degree of curing of the nanocomposites was evaluated by William-Landel-Ferry (WLF) constants. The breadth of the glass transition in the tanδ curve and shape parameter (β) in the Kolrausch-Williams-Watts (KWW) equation were used to investigate the network heterogeneity of the samples. All these referred parameters increased with SiC nanoparticles loading up to 0.6% (wt). In contrast, upon introducing SiC at higher concentrations, the viscoelastic properties of the nanocomposites reduced significantly. SEM analysis was used to evaluate the DMTA results regarding the dispersion state of the nanoparticles in the matrix.

Effect of temperature and filler volume fraction on the creep and recovery behaviour of MWCNT–COOH–reinforced polypropylene films

Nonlinear viscoelastic behaviour of –COOH functionalized multi-walled carbon nanotubes reinforced polypropylene nanocomposites is examined up to 2% MWCNT concentration. Isochronal creep and strain recovery experiments are conducted in dynamic mechanical analyser with oscillatory inputs. Creep stress level of 5 MPa is selected and successive creep and recovery experiments are performed at $$-\,20\,^\circ $$ C, $$25\,^\circ $$ C and $$50\,^\circ $$ C to analyse the effect of temperature and MWCNT concentration on strain developed during creep loading and strain recovery stages. A well-known Schapery nonlinear viscoelastic solid model with Zapas–Crissman viscoplastic term is fitted to the experimental observations. Stress-dependent nonlinear model parameters are obtained under temperature and MWCNT loading. Viscoelastic and viscoplastic strains are predicted at the end of recovery period. High temperatures and low concentrations of MWCNT are observed to cause higher viscoplastic strain. Strengthening MWCNT up to 1% improves the thermomechanical behaviour and viscoelastic recovery and decreases the viscoplastic strain in nanocomposites. Temperature-dependent compliance behaviour of nanocomposites is investigated with Williams–Landel–Ferry model and Arrhenius model using time–temperature superposition principle.

Temperature-frequency-dependent properties analysis of a bio-composite based on a new liquid thermoplastic resin reinforced with jute fibers

One of the main current challenges in the development of materials is related to meet the structural industry demanding requirements and that are sustainable at the same time. This paper presents the composite mechanical characterization based on an innovative thermoplastic matrix reinforced by jute fibers. The composite was fabricated via VARTM (Vacuum Assisted Resin Transfer Molding) using jute fiber fabric in the 0/90° orientation. Several specimens were tested for uniaxial tension loading and their mechanical behavior was discussed. Also, the dynamic properties were evaluated with frequency variation and a master curve was constructed based on the WLF (Williams–Landel–Ferry) principle. Finally, fractographic evaluations of the fracture surfaces performed in a scanning electron microscope (SEM) confirm the quantitative characterization obtained from the mechanical analysis. The results obtained prove that the Jute/Elium® 150 composites can become a low-cost alternative methodology in the manufacture of more sustainable composites for the industry.