Thermo-mechanical Performance Research Articles

Polyalkenamers as Drop-In Additives for Ring-Opening Metathesis Polymerization: A Promising Upcycling Paradigm.

We report a distinct strategy to upcycle waste polyalkenamers such as polybutadiene into new, performance-advantaged materials by using them as drop-in additives for ring-opening metathesis polymerization (ROMP). The polyalkenamers serve as competent chain-transfer agents in ROMPs of common classes of cyclic olefin monomers, facilitating good molecular weight control, allowing low Ru catalyst loadings, and enabling efficient incorporation of the polyalkenamer into the synthesized polymeric material. We successfully demonstrate ROMP using model polyalkenamers and translate these learnings to leverage commercial polybutadiene and acrylonitrile butadiene styrene (ABS) as chain transfer agents for ROMP copolymerizations. Critically, our strategy is shown to be highly efficient and operationally simple, quantitatively incorporating the polyalkenamer and inheriting aspects of its thermomechanical performance. Our results highlight a promising pathway for the upcycling of polyalkenamers and provide an alternative to existing deconstruction and functional upcycling strategies.

A comparative study of thermo-mechanical performance of brake rotor discs using finite element analysis

A comparative study of thermo-mechanical performance of brake rotor discs using finite element analysis

4D Printing of PLA/PBS Biopolymers: Impact of Polymer Grade Variations on Thermomechanical Performance

4D Printing of PLA/PBS Biopolymers: Impact of Polymer Grade Variations on Thermomechanical Performance

Bio-Templated Aerogel Fibers: Heterogeneous Spinodal Architecting and In Situ Fibrillation of Thermoplastic Polyurethane-Silica on Nanostructured Cellulose Nanofiber Scaffold for Enhanced Thermomechanical Performance.

This study addresses the inherent fragility and fractal limitations of traditional silica aerogels by developing a bio-templated aerogel fiber. Integrating cellulose nanofibers (CNFs), thermoplastic polyurethane (TPU), and silica aerogel (SA) in a dimethyl sulfoxide (DMSO) dispersion, a gel-spinning technique was employed to create aerogel fibers with superior thermomechanical performance. CNF also provided excellent rheological modification for successful spinnability, fast gelation, and fiber formation. The unique hierarchical structure of these fibers, formed through hot-stretching and surface modification, combined the superior mechanical strength and flexibility of TPU with the exceptional insulation properties of CNF and SA. The CNF network, encapsulated within the SA particles, formed a core-shell structure, axially aligned, that significantly enhances the thermal stability and mechanical performance of the fibers while maintaining a lightweight and porous architecture. Comprehensive morphological, thermal, and mechanical analyses were conducted to evaluate the properties of the developed aerogel fibers. Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy verified the successful surface modification and grafting reactions on CNF, contributing to improved hydrophobicity and thermal insulation. Adjusting the CNF content allowed for tailoring of the thermomechanical characteristics, with a notable 294% increase in tensile strength from 5.3 to 15.6 MPa and an enhanced crystallization temperature from 106 to 119.97 °C. Furthermore, cyclic tensile and compression tests validated the durability and shape recovery capabilities of the aerogel fibers, making them promising candidates for high-performance applications in extreme environments. The thermal conductivity validated by experimental data further highlights the potential of CNF-based aerogel fibers as sustainable and multifunctional materials for advanced thermal insulation, mechanical reinforcement, and flexible structural applications.

Performance-based analysis on fire behavior of shield tunnel joint with DDCI connector

In recent years, there has been significant advancement in large-diameter shield tunnel technology, with the continuous emergence of new joint types. To meet the different requirement of application, numerous studies have been done on the mechanical behavior of the various new joints. In this paper, a new DDCI connector for the shield tunnel joint was proposed. Simultaneously, a thermo-mechanical performance analysis was conducted on the new longitudinal joint combining inclined bolts and the DDCI connector. A refined finite element model of the new joint was established and various working conditions were designed to obtain a full understanding of the thermo-mechanical performance of the structure. This evaluation included the presence of initial loads and exposure to different fire curves, specifically the RABT and RWS fire curves. The validity of the numerical model and the indirect coupling analysis method were verified by physical experiments and previous research, respectively. The temperature distribution, joint opening and internal force of the connectors were analyzed in the study. According to the results, different fire curves and thermo-mechanical sequences both have a great impact on the mechanical response of the new joint under elevated temperature. Moreover, due to the involvement of the DDCI connector, the new joint shows clear advantages in strength and stiffness over the conventional joint. The results contribute to the fire-resistant design of the large-diameter shield tunnels adopting the scheme of the new joint with a DDCI connector.

Soft modular pipe robot inspired by earthworm for adaptive pipeline internal structure

Abstract The inspection, maintenance, and repair of complex pipelines have motivated the development of soft robots with highly flexible and good adaptability. In this study, inspired by the unique locomotion of earthworms, we developed a type of smart material–driven soft modular pipe robot capable of stable manipulation and performing in unstructured pipe environments, which easily assembles into more complex configurations with multiple modules for practical use. Our prototype robot consists of three soft telescopic modules connected in series with flexible bellows and a tail friction mechanism, where the modules adopt a high-energy density shape memory alloy spring as an actuator. Based on analyzing the peristaltic process of the module inside the pipe, it is ensured that the geometric constraint performance of the braided mesh pipe is reasonably matched with the thermomechanical performance of the SMA spring to realize the alternating conversion of anchoring and releasing. By optimizing the overall robotic structure, it is demonstrated that our robot achieves robust crawling in horizontal, vertical, variable-diameter, and curved pipes, wet pipes with the partial presence of water, and pipes with complex cavities through simple open-loop on/off control.

Air Foil Thrust and Journal Bearing Coatings: A Review

Abstract Surfaces of air foil thrust and journal bearings in high-speed turbomachinery are coated to improve their operational integrity, particularly when the aerodynamic load-carrying capacity is reduced during instances of startup and shutdown. Surface coatings, as protective barriers in air foil bearings, can mitigate the adverse effects of direct surface interactions on such occasions. This article provides an in-depth review of the body of important research conducted for the study of coated air foil thrust and journal bearings, highlighting the state of the art in coating technology. The review features the role of composite coatings, designed to provide favorable thermal, mechanical, and frictional characteristics. This article also highlights the trends in the selection of coatings for air foil bearings, pertinent to desired thermo-mechanical performance.

A Systematic Study on Biobased Epoxy-Alcohol Networks: Highlighting the Advantage of Step-Growth Polyaddition over Chain-Growth Cationic Photopolymerization.

Vanillyl alcohol has emerged as a widely used building block for the development of biobased monomers. More specifically, the cationic (photo-)polymerization of the respective diglycidyl ether (DGEVA) is known to produce materials of outstanding thermomechanical performance. Generally, chain transfer agents (CTAs) are of interest in cationic resins not only because they lead to more homogeneous polymer networks but also because they strikingly improve the polymerization speed. Herein, the aim is to compare the cationic chain-growth photopolymerization with the thermally initiated anionic step-growth polymerization, with and without the addition of CTAs. Indeed, CTAs lead to faster polymerization reactions as well as the formation of more homogeneous networks, especially in the case of the thermal anionic step-growth polymerization. Resulting from curing above the TG of the respective anionic step-growth polymer, materials with outstanding tensile toughness (>5MJ cm-3) are obtained that result in the manufacture of potential shape-memory polymers.

Supercritical Water Gasification of Biomass on CSP Plants: Comparison of On-Sun and Off-Sun Designs

A comparative study of On-Sun and Off-Sun designs for supercritical water gasification (SCWG) of biomass on concentrated solar power (CSP) plants was here presented. In the On-Sun design, the tubular reactor was placed on a cavity receiver of a solar power tower (SPT) plant and the heat employed to produce the gasification came directly from the sun (viz. the solar radiation was concentrated, thanks to the heliostat field, onto the tube's surface). In the Off-Sun designs, the gasification of the biomass was carried out inside a heat exchanger and it was produced thanks to the heat absorbed from the hottest fluid, which can be obtained from CSP plants or electrical heating. This work numerically investigated the thermomechanical performance of both designs. The results stood out the relation between temperature-gas yield-thermal stress. In On-Sun configurations the gas yield was 5 times higher than those obtained in the Off-Sun configuration. However, the highest values of both temperature and stress may produce the failure of the reactor. This fact could be avoided in an Off-Sun reactor, since its uniform heating conditions mitigate the maximum temperature and stresses.

Nonlinear thermo-mechanical static stability analysis of FG-TPMS shallow spherical shells

An analytical solution for the nonlinear static stability problem of functionally graded triply periodic minimal surface (FG-TPMS) shallow spherical shells is studied in the current research for the first time. Three common TPMS structures including Primitive (P), Gyroid (G), and I-graph and Wrapped Package-graph (IWP) with three models of functionally graded porosity distribution along the thickness are considered. The shallow spherical shells (shallow SSs) are subjected to combined thermo-mechanical loadings and rested on a nonlinear elastic foundation. The fundamental formulas are expressed based on the higher-order shear deformation theory (HSDT) and von Kármán's geometrical nonlinearities. Employing the Ritz energy minimization method, the explicit relationship between load and deflection is derived. Subsequently, the static stability behavior of FG-TPMS shallow SSs is investigated. Numerical illustrations are investigated to show the superior thermo-mechanical load-carrying performance of the FG-TPMS SSs compared to corresponding isotropic structures of the same weight. The significant effects of geometric parameters, nonlinear elastic foundation parameters, and the type of FG-TPMS structures on the nonlinear static stability behavior of shallow SSs are further considered.

Process–Property Correlation in Sustainable Printing Extrusion of Bio-Based Filaments

This study investigated the effect of two critical variables for environmental process sustainability, i.e., extruder temperature and printing rate, on thermomechanical performance and accuracy in overall sample sizes, when printing bio-based materials. In this context, 3D specimens produced from basic polylactide (n-PLA) and wood-filled PLA polymer (f-PLA) were realized using extrusion-based additive manufacturing technology (MEX) by varying the nozzle temperatures (200 °C, 210 °C, and 220 °C) and speed (from 70 mm/s to 130 mm/s). Dynamic mechanical analysis (DMA) was carried out on the produced specimens, providing information on changes in storage modulus at testing temperature of 30 °C (E′30) and glass transition temperature (Tg) for each printing condition. Measurements of sample sizes allowed for printing precision considerations as a function of processing temperature and speed. The results revealed similar trends in E′30 changes in printed specimens at a fixed extruder temperature as a function of printing speed for n-PLA and f-PLA. Infrared spectroscopy was performed on printed samples and unextruded material to attest potential material degradation under various operating conditions. Finally, images of sample surface allowed to verify the homogeneity of the diameter of the extruded material, and the layer–layer contact at the interface.

Polymeric Fibers with High Strength and High Toughness at Extreme Temperatures.

Developing strong and simultaneously tough polymeric materials with excellent thermal stability and mechanical performance even under extreme temperatures is truly a challenge. In a disruptive progress, continuous polymeric yarns are developed with a combination of high tensile strength of (1145 ± 44) MPa and ultrahigh toughness of (350 ± 24) J g-1 and high thermomechanical properties from -196 to 200°C. The comprehensive thermomechanical performance of this yarn surpasses that of previously developed polymeric materials and dragline spider silks. The results demonstrate that the molecular structure of polyimide (PI) with the incorporation of flexible-rigid macromolecular, hierarchically spiral-oriented fibers, and high glass transition temperature (248°C) are keys for the yarn's notable comprehensive performance in thermomechanical properties. The materials are ideal for technical components exposed to high thermomechanical loadings, such as those encountered in spacecraft or automotive engineering for safety-critical applications.

A review of high-entropy ceramics preparation methods, properties in different application fields and their regulation methods

High-entropy alloys (HEAs) provides a new way to develop new materials with adjustable performance due to their unique cocktail effect. Inspired by HEAs, a ceramic material with high-entropy effect has been developed, which was named high-entropy ceramics (HECs). With the introduction of the concept of entropy stability, research on HECs has developed rapidly. At present, research on the performance of HECs has extended to traditional performance such as thermomechanical performance, oxidation resistance, and magnetic properties, as well as emerging performance such as catalytic performance, optical properties, and radiation resistance. Based on the definition of HECs, this paper reviews the crystal structure and preparation methods of HECs and supplements the simulation calculation methods and descriptors which is suitable for HECs. In this paper, the performance of HECs at this stage is divided into traditional fields and emerging fields according to the application fields. A variety of performance regulation methods are reviewed, and the development and research directions of HECs are prospected.

Fabrication of NBI Ion Source Back Plate and its High Heat Flux Experiment

The back plate is an important component of the ion source because of its multiple roles including heat load removal during beam operation. The main components of the back plate are (1) a Type 304L stainless steel (SS304L) magnet positioning plate that holds samarium cobalt permanent magnets required for the confinement of ion source plasma, (2) an oxygen-free electronic copper cooling plate with 35 inner and 8 outer cooling channel grooves (each of which is 4 × 1.8 mm2) that is vacuum brazed with a SS304L magnet positioning plate, and (3) a SS304L magnet cover plate. In this paper, the back plate is successfully fabricated, and a high heat flux experiment is done at the High Heat Flux Test Facility Center with an electron beam power of 200 kW for 458 s. The uniform incident heat flux is 2.5 MW/m2. Demineralized water at 34°C is supplied at the rate of 1 kg/s to the cooling plate at inlet pressure of 8.2 bars to remove the high heat load. The surface temperature of the copper plate is measured by an infrared camera, and three temperature regions are observed. The measured average surface temperature of the cooling plate is ~152°C. The bulk water temperature rise ΔTw is ~39.42°C. The estimated absorbed heat flux is ~2.04 MW/m2, and the heat absorption coefficient is 81.6%. The measured leak rate after the heat flux test is 1.6 × 10−8 mbars∙L/s. These High Heat Flux Test experimental results will be useful to study the thermomechanical performance of the back plate and to understand the effect of increasing the beam pulse length.

Thermo-mechanical performance assessment of geopolymer synthesized with steel slag and glass powder at elevated temperatures

This study utilizes glass powder (GP) and steel slag (SS) as a solid precursor material along with Fly Ash (FA) as a key ingredient to produce geopolymer composite (GPC). The developed geopolymer materials were subjected to elevated temperatures up to 800 °C to simulate intense fire conditions. Thermo-mechanical testing was conducted to evaluate the performance and microstructural characteristics of the exposed geopolymers. Results demonstrated that the GPC incorporating GP exhibited exceptional resistance to high temperatures, significantly retaining compressive strength. Conversely, the SS-based geopolymer showed a 52–54% reduction in strength, indicating improved thermal resistance. Both SS and GP-based GPC demonstrated resilience to high-temperature exposure, with SS addition providing the benefit of preserving structural integrity. However, the noted reduction in compressive strength highlights potential challenges for the application of geopolymer materials in areas exposed to high temperatures or fire.

Effects of Y2Zr2O7 particles and rolling deformation process on the mechanical properties and heat load behavior of W–Y2Zr2O7 plate

This paper addresses the significant requirements in China's fusion engineering and investigates the preparation technology and performance characterization of high-performance tungsten-based materials used as PFMs. The rolled W–Y2Zr2O7 plate were prepared through sintering and subsequent rolling, and steady-state heat load assessment was conducted under fusion device working conditions. Additionally, the change in mechanical behavior of the rolled plates was investigated across different surfaces. The results also revealed that the rolling plate exhibited a DBTT between RT and 200 °C, with more superior mechanical properties along the RD direction. The flat-plate W–Y2Zr2O7/Cu components demonstrated the ability to withstand 1000 heat load cycles at 10 MW/m2 without cracking, indicating favorable thermo-mechanical performance as PFMs. These findings serve as a valuable reference for the fabrication of tungsten-based materials in fusion engineering.

Crystallization and performance evolution of PHBV nanocomposites through annealing: The role of surface modification of CNCs

To address the brittleness challenge of polyhydroxybutyrate-co-valerate (PHBV) rooting from its slow nucleation rate, cellulose nanocrystals (CNCs) were employed as bio-based nano nucleation and reinforcement agents. CNCs were further functionalized through succinylation using aliphatic dodecyl succinic anhydride (DDSA), for improved compatibility and dispersion within PHBV. Nanocomposites of PHBV incorporating pristine or DDSA-modified CNC (mCNC) were prepared through solution mixing followed by melt injection molding. The study focused on investigating how CNCs and mCNCs affect the crystallization behavior, thermal, rheological, and mechanical properties of PHBV nanocomposites over time, in the course of annealing or conditioning. Thermal results revealed that the incorporation of neat CNCs generally improving stability due to restricted polymer chain mobility and hydrogen bonding, while DDSA-modified CNCs show varied effects depending on the concentration, sometimes diminishing stability due to increased chain mobility. Polarized optical microscopy revealed the superior nucleation efficiency of mCNC, especially at low contents, leading to smaller and numerous spherulites over conditioning. Rheological analysis indicated a dilution effect of the hairy mCNCs, decreasing both dynamic modulus and complex viscosity. Mechanical properties, assessed through tensile testing and dynamic mechanical analysis after 15 days of conditioning, demonstrated the evolving effect of CNCs on aging-induced embrittlement and thermo-mechanical performance of PHBV during storage. The results revealed that incorporating 1 wt% mCNCs effectively toughened PHBV, increasing Young's modulus, and decreasing Tg without scarifying elongation at break compared to neat PHBV. The findings position mCNCs as a promising nucleation agent which retains PHBV nanocomposites toughness after aging.

Numerical investigation of SUPERFACT-1 experiment by a MOX fuel pin thermo-mechanical model

Preparations are currently underway to develop ISAA-Na code, a sodium-cooled fast reactors (SFRs) specific version of an integrated severe accident analysis code. This version aims to evaluate both protected and unprotected accidents in SFRs. Given the crucial role of fuel pin thermo-mechanical behavior in SFR safety analysis, an advanced model for MOX(Mixed OXide) fuel pin thermo-mechanical performance under operation conditions has been developed and validated. This validation involved simulating the SUPERFACT-1 fast reactor irradiation experiment using ISAA-Na. The resulting calculation data were compared with experimental measurements and the outcomes of other codes dedicated to fuel pin performance analysis (TRANSURANUS, MACROS, andGERMINAL) to assess the fuel pin thermo-mechanical model. The overall code assessment reveals that the model achieves satisfactory performance in simulating fuel pin behavior, with predicted errors falling within an acceptable range.

Thermo-mechanical performance enhancement of volumetric solar receivers using graded porous absorbers

The potential of graded porous absorbers in enhancing the thermo-mechanical performance of a volumetric solar receiver is investigated. A coupled numerical model is developed and simulations are conducted on various configurations with porosity and pore size variations in axial, radial, and bidirectional arrangements. The performance of graded configurations is first compared with a representative uniform configuration, and then the optimal configurations within each arrangement are further analyzed to determine the overall best configuration. The parametric study reveals conflicting thermo-mechanical performances in majority of the arrangements. The configurations with a porosity range of 0.9–0.95 and a pore size range of 2–4 mm exhibit the best performance across all variations. Among the best configurations, the bidirectional configuration with radially decreasing porosity and axially increasing pore size demonstrates the best performance with an increase of 8.96 % in air outlet temperature and a decrease of 22.7 % and 4 % in Failure Index and pressure drop, respectively. Bidirectional configuration maintained superior performance over the receiver length range of 1–6 cm and velocity range of 0.4–2.4 m/s. The results underscore the suitability of certain graded arrangements for achieving improved thermal performance while ensuring higher mechanical safety.

Design of 3D printable boehmite alumina/thermally exfoliated reduced graphene oxide-based polymeric nanocomposites with high dielectric constant, mechanical and thermomechanical performance

In this study, melt-blending was employed to blend 80 wt% poly(lactic acid) and 20 wt% poly(ε-caprolactone) (80 %PLA/20 %PCL) with boehmite alumina-thermally exfoliated reduced graphene oxide (BA-TERGO) as nanofillers. Herein, we present a novel synergy effect of BA/TERGO particles on improving the dielectric constant while maintaining dielectric loss at lower magnitudes. Also, improving the thermomechanical properties of tough PLA/PCL nanocomposite through the incorporation of a dual-filer system strategy. Consequently, remarkable increase in dielectric constant was achieved for BA-TERGO/blend nanocomposite. In particular, the blend exhibited dielectric constant of about 2.91, while the BA-TERGO/blend nanocomposite exhibited dielectric constant of about 4.93 at a frequency of 2.0 ×106 Hz and a temperature of 190 ºC. On the other hand, tensile modulus of the BA-TERGO/blend nanocomposite increased from 1908.5 MPa to 2505.2 MPa and the tensile strength increased from 70.48 MPa to 96.3 MPa when compared to that of the neat blend. BA-blend and BA-TERGO/blend nanocomposites provided the improved storage modulus and thermal stability. This finding renders PLA-based biodegradable materials suitable for tough 3D printable material with potential for integrated circuits applications.