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Recently, the CNC/GEL (cellulose nanocrystals/gelatin) composite hydrogel has been used as a biomaterial for 3D printing of tissue engineering scaffolds. Rheological properties of hydrogel have been regarded as one of the most important factors affecting printing quality, especially the viscosity recover time. However, there is still a lack of comprehensive research on the rheology property of the CNC/GEL hydrogel in the process of 3D printing. In this study, the CNC was isolated from Humulus japonicus, and a CNC/GEL hydrogel system was prepared. The rheological properties of CNC/GEL hydrogel were evaluated using a rotary rheometer. The viscosity recovery time of the CNC/GEL hydrogel was measured using a special method. The optimal ratio of hydrogel was obtained by rheology experiment and mechanical test. The flow field distribution of the hydrogel in the flow passage of 3D printer was analyzed using fluent simulation. The rheological parameters of a hydrogel can be adjusted by changing the printing conditions. Thus, the effect of printing conditions on the formation of CNC/GEL filaments was also investigated. Finally, the biocompatibility of the printed CNC/GEL scaffold after crosslinking treatment was verified using CCK-8 and Hoechst 33342/PI double-staining assays. The present study shows a new approach for the analysis of rheological properties of CNC/GEL and also provides some suggestions for 3D printing of CNC/GEL scaffolds.

We report direct measurements of spatially resolved stress at the boundary of a shearthickening cornstarch suspension revealing persistent regions of high local stress propagating in the flow direction at the speed of the top boundary. The persistence of these propagating fronts enables precise measurements of their structure, including the profile of boundary stress measured by boundary stress microscopy (BSM) and the nonaffine velocity of particles at the bottom boundary of the suspension measured by particle image velocimetry (PIV). In addition, we directly measure the relative flow between the particle phase and the suspending fluid (fluid migration) and find the migration is highly localized to the fronts and changes direction across the front, indicating that the fronts are composed of a localized region of high dilatant pressure and low particle concentration. The magnitude of the flow indicates that the pore pressure difference driving the fluid migration is comparable to the critical shear stress for the onset of shear thickening. The propagating fronts fully account for the increase in viscosity with applied stress reported by the rheometer and are consistent with the existence of a stable jammed region in contact with one boundary of the system that generates a propagating network of percolated frictional contacts spanning the gap between the rheometer plates and producing strong localized dilatant pressure.

The complex modulus is one of the intrinsic properties of bituminous materials, and, hence, is of importance for their rheological characterization. It was shown by various authors that the complex modulus of asphalt mixtures can be calculated from dynamic modulus measurements using the Resonant Acoustic Spectroscopy (RAS). This paper extends the RAS technique to bitumen. For the purpose of validation, rheological data for the same bitumen are also derived from standard Dynamic Shear Rheometer (DSR) tests, and the master curves resulting from both methods are compared. The laboratory programme comprised a temperature range from −30 °C to 20 °C, and four different bitumens in unaged and aged condition, resulting in 36 different test variants. RAS successfully characterizes the complex modulus of bitumen and reflects temperature and ageing effects, with good agreement to DSR results at low temperatures. At higher temperatures, viscosity and damping introduce deviations, indicating that RAS is effective for modulus evaluation but not sufficient for complete master curve development.

High-frequency rheology is a form of mechanical spectroscopy which provides access to fast dynamics in soft materials and hence can give valuable information about the local scale microstructure. It is particularly useful for systems where time-temperature superposition cannot be used, when there is a need to extend the frequency range beyond what is possible with conventional rotational devices. This review gives an overview of different approaches to high-frequency bulk rheometry, i.e. mechanical rheometers that can operate at acoustic (20 Hz–20 kHz) or ultrasound (> 20 kHz) frequencies. As with all rheometers, precise control and know-how of the kinematic conditions are of prime importance. The inherent effects of shear wave propagation that occur in oscillatory measurements will hence be addressed first, identifying the gap and surface loading limits. Different high-frequency techniques are then classified based on their mode of operation. They are reviewed critically, contrasting ease of operation with the dynamic frequency range obtained. A comparative overview of the different types of techniques in terms of their operating window aims to provide a practical guide for selecting the right approach for a given problem. The review ends with a more forward looking discussion of selected material classes for which the use of high-frequency rheometry has proven particularly valuable or holds promise for bringing physical insights.

Precise and reliable prediction of soft and structured materials’ behavior under flowing conditions is of great interest to academics and industrial researchers alike. The classical route to achieving this goal is to construct constitutive relations that, through simplifying assumptions, approximate the time- and rate-dependent stress response of a complex fluid to an imposed deformation.The parameters of these simplified models are then identified by suitable rheological testing. The accuracy of each model is limited by the assumptions made in its construction, and, to a lesser extent, the ability to determine numerical values of parameters from the experimental data. In this work, we leverage advances in machine learning methodologies to construct rheology-informed graph neural networks (RhiGNets) that are capable of learning the hidden rheology of a complex fluid through a limited number of experiments. A multifidelity approach is then taken to combine limited additional experimental data with the RhiGNet predictions to develop “digital rheometers” that can be used in place of a physical instrument.

The rheological behaviour of concentrated aqueous dispersions of graphene oxide (GO) was studied as a model system and then compared to those of GO in poly(methyl methacrylate) (PMMA). Dynamic and steady shear tests were conducted using a parallel plate rheometer. The aqueous system behaved as a reversibly flocculated dispersion with linear viscoelastic regions (LVR) extending up to strains of 10 %. Dynamic frequency sweeps conducted within the LVR showed a classic strong-gel spectrum for high concentrations. Under steady shear, the dispersions shear-thinned up to a Peclet number ( Pe ) <1, followed by a power law at higher Pe . The dispersions were thixotropic and recovered their structure after 60 min rest. The change in rheological properties of the PMMA upon the addition of the GO was less pronounced possibly due to the absence of hydrogen bonding; a relatively small increase in viscosity was found, which is encouraging for the melt processing of graphene composites.

Understanding the mechanics of fiber attrition during the extrusion process is highly important in predicting the strength of long fiber-reinforced thermoplastic composites. However, little work has been done to investigate the mechanics of fiber dispersion and its effects on fiber attrition. This study aims at investigating fiber dispersion in simple shear flows for long fiber-reinforced thermoplastic pellets. Depending on the fabrication process, fiber bundles display distinct levels of compaction within the pellets. Studies have shown that morphological differences can lead to differences in dispersion mechanics; therefore, using a Couette rheometer and a sliding plate rheometer, coated and pultruded pellets were subjected to simple shear deformation, and the amount of dispersion was quantified. Additionally, a new image-based analysis method is presented in this study to measure fiber dispersion for a multi-pellet-filled system. Results from the single-pellet dispersion study showed a small amount of correlation between the dimensionless morphological parameter and the dispersion measurement. Pultruded and coated pellets were both found to have similar dispersion rates in a multi-pellet system. However, pultruded pellets were found to have a higher dispersion value at all levels when compared with coated pellets in both dispersion studies.

This study explores the impact of adding waste vehicular crumb rubber to the commercially available warm mix additives Sasobit® and Zycotherm® on modified asphalt binders’ physical and rheological properties. Various concentrations of crumb rubber (0%, 10%, 15%, and 20%) were introduced to asphalt binder samples with 2% and 4% Sasobit and 1.5% and 3% Zycotherm. The investigation employed conventional tests (penetration and softening point) and advanced mechanical characterization tests, including Superpave rotational viscosity (RV), Dynamic Shear Rheometer (DSR), DSR multi-stress creep recovery (MSCR), DSR linear amplitude sweep (LAS), and Bending Beam Rheometer (BBR). Traditional tests measured the asphalt consistency, while workability was assessed through the RV test. The results showed that the Zycotherm binders experienced a more significant penetration reduction than the Sasobit binders. Additionally, an increased crumb rubber content consistently elevated the softening point and rotational viscosity, enhancing the complex shear modulus (G*) values. Rubberized binders exhibited an improved rutting performance and low-temperature PG grades. Increasing the crumb rubber content enhanced fatigue life, with Z1.5CR20 and S2CR20 demonstrating the longest fatigue lives among the Zycotherm and Sasobit binders, respectively. Overall, Z1.5CR20 is recommended for colder climates, while S2CR20 is suitable for hot-climate applications based on extensive analysis.

Texture-modified diets are the first-line compensatory strategy for older patients with swallowing and mastication disorders. However, the absence of a common protocol to assess textural properties inhibits their standardization and quality control and, thus, patient safety. This study aimed to (a) assess the rheological and textural properties of ten thick purees (Texture C, British Dietetic Association), (b) understand the effect of oral processing, and (c) measure the properties of the ready-to-swallow bolus after oral processing in healthy adults. Shear viscosity at 50 s−1 and 300 s−1 and textural properties (maximum force, cohesiveness, and adhesiveness) of boluses of ten thick purees were analyzed with a rheometer and a texture analyzer before and after oral processing (ready-to-swallow) in five healthy volunteers. Viscosity varied by 81.78% at 50 s−1 (900–4800 mPa·s) among purees before oral processing. Maximum force varied by 60% (0.47–1.2 N); cohesiveness, 18% (0.66–0.82), and adhesiveness, 32% (0.74–1.1 N·s). The high variability of viscosity was also present in ready-to-swallow boluses, 70.32% among purees. Oral processing significantly reduced viscosity in most purees (French omelet, zucchini omelet, turkey stew, red lentils, noodles, and hake fish) and also significantly reduced maximum force (7–36%) and adhesiveness (17–51%) but hardly affected cohesiveness (<5%). All thick purees met the qualitative textural descriptors for Level C texture. However, all ten purees showed significant differences in all parameters measured instrumentally and were affected differently by oral processing. This study demonstrates the need to use instrumental quality control using standardized protocols and SI units to narrow the variability and provide the optimal values for patients with dysphagia who require texture-modified diets.

This research evaluates the rheological and mechanical properties of polymer- and nanomaterials-modified bitumen by incorporating nanosilica (NSA), nanoclay (NCY), and Acrylonitrile Styrene Acrylate (ASA) at 5% by weight of the bitumen. The samples were prepared at 165 °C for one hour to obtain homogeneous blends. All samples were subjected to short- and long-term aging to simulate the effects of different operating conditions. The research conducted a series of tests, including consistency, frequency sweep, and multiple creep stress and recovery (MSCR) using the dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The results showed that all modified bitumen outperformed the neat bitumen. The frequency sweep showed a higher complex modulus (G*) and lower phase angle (δ), indicating enhanced viscoelastic properties and, thus, higher resistance to permanent deformation. The BBR test revealed that the bitumen modified with NCY5% has a creep stiffness of 47.13 MPa, a 51.5% improvement compared to the neat bitumen, while the NSA5% has the highest m-value, a 28.5% enhancement compared with the neat bitumen. The MSCR showed that the modified blends have better recovery properties and, therefore, better resistance to permanent deformation under repeated loadings. The aging index demonstrated that the modified bitumen is less vulnerable to aging and maintains their good flexibility and resistance to permanent deformations. Finally, these results showed that adding 5% polymer and nanomaterials improved the bitumen’s’ performance before and after aging by reducing permanent deformation and enhancing crack resistance at low temperatures, thus extending the pavement service life and making them an effective alternative for improving pavement performance in various climatic conditions and under high traffic loads.