Thermo-mechanical Performance Research Articles

Thermomechanical performance and durability analysis of graded thermal barrier coatings over engine piston using finite element analysis

Thermomechanical performance and durability analysis of graded thermal barrier coatings over engine piston using finite element analysis

Optimizing hybrid fiber content for enhanced thermo-mechanical performance of high-strength concrete

Fiber-reinforced concrete (FRC) is an innovative category of construction materials known for their enhanced mechanical strength and durability. However, there is limited information regarding the synergistic effects on concrete strength in hybrid configurations. This study utilizes steel and basalt fibers (BF) in the concrete matrix to make high-strength concrete (HSC) specimens. Moreover, varying proportions ranging from 0.25% to 1% are employed by volume of concrete to assess its mechanical properties, mass degradation, and surface cracking after exposure to escalating temperatures of 300°C, 600°C, and 800°C at a rate of 5 °C/min. The findings revealed that hybrid fiber-reinforced concrete (HFRC) exhibited superior mechanical properties relative to the control specimen. This improvement is due to the basalt fibers' filler properties and the hybrid fiber's ability to bridge cracks. In addition, 0.5% HFRC demonstrates superior mechanical properties as compared to the control specimen. The inclusion of Hybrid fibers prevented crack growth through fiber bridging, resulting in delayed crack propagation and significant enhancement in the toughness and crack energy of HFRC. The toughness and crack energy was increased with the rising content of hybrid fibers (HF) in concrete. The compressive failure mode of HSC with low fiber content changes from a single, brittle crack to a more durable multiple crack-resistant mode. It was noted that too many hybrid fibers in concrete can have adverse effects, resulting in clumping. This not only causes voids but also diminishes the amount of cement present, which in turn minimizes the strength of the concrete. Ultimate and peak strain is positively associated with the content of HF in concrete. Furthermore, concrete specimens with 1% hybrid fiber exhibited the most minor mass degradation.

Performance of bioresorbable peptide incorporated polymers produced for fused deposition modelling (FDM)

The use of biomaterials in additive manufacturing (AM) of medical devices has gained significant attention over the years, especially in areas such as wound care and orthopedics. This study aims to investigate the performance of bioresorbable peptide-incorporated polymers produced for fused deposition modelling (FDM) process. Herein, we report FDM 3D Printing process of bioactive polymers comprising polycaprolactone (PCL), poly(lactic-co-glycolic acid) (PLGA) or polylactic acid (PLA) or blended with peptide–containing brush copolymers bearing similar synthetic polymer side chains. Mechanical, thermal and rheological properties of the materials were carried out and we report that the incorporation of bioactive polymers into these biodegradable polymers does not result in significant changes to glass transition temperature, melt temperature, tensile properties of the base polymers. However, it was observed that flexural and rheological properties altered significantly. This study provides an insight into the thermomechanical performance of bioresorbable peptide-incorporated polymers for FDM utilization which allows for their use potential in medical device fabrication.

Oxygenated moiety enhanced thermal stabilization, mechanical, and thermomechanical performance of polyacrylonitrile/single wall carbon nanotubes films

AbstractThermo‐oxidative stabilization of polyacrylonitrile (PAN)‐copolymer and PAN/single‐walled carbon nanotube (SWCNT) composite films were studied in the presence of oxygenated entities which may act as an internal oxygen supplier. The oxygenated moiety exhibited dual behavior, enhancing the stabilization efficiency of PAN while also improving the dispersion of SWCNT. The addition of oxygenated moiety treated SWCNT to PAN resulted in a significant reduction in activation energy from 118 kJ/mol to 99 kJ/mol, owing to a more stable oxidation reaction. Thermogravimetric analysis showed weight loss due to stabilization, and polymer chain degradation was lower in treated SWCNT composite films, resulting in an approximate 6% increase in residual weight. Mechanical testing showed a significant increase in tensile strength to 54.15 MPa and tensile modulus to 2.53 GPa with elongation at break of 13.2%, which is attributed to the enhanced interfacial shear strength resulting from the improved dispersion of oxygenated moiety‐treated nanotubes. Furthermore, thermomechanical analysis studies showed improvement in dimension stability with oxygenated moiety treated SWCNT composite films, attributed to better dispersion and increased interfacial strength between the polymer and filler.Highlights Oxygenated entities stabilize PAN and improve SWCNT dispersion. Activation energy was reduced from 118 to 99 kJ/mol with Tween‐80. Residual weight increased by 6% with treated SWCNT in TGA. Improved tensile strength (54.14 MPa), modulus (2.53 GPa) with modified SWCNT. Dimension stability is enhanced by interfacial strength with modified SWCNT.

Itaconic acid-based 3D printed nanocomposites: An in-depth study on the effect of nanoinclusions on the physicochemical properties and the printability of formulations based on polyester itaconates

The demand for novel bio-based materials in UV-curing additive manufacturing has surged due to increasing environmental concerns and a growing emphasis on sustainable practices in the manufacturing industry. However, at the moment, their thermomechanical performance is not equal to that of their fossil-based counterparts and this impedes the acceptance of these materials within the industrial community. Therefore, in this study, a series of nanocomposite polyesters based on itaconic acid was synthesized for the first time with in-situ polymerization, in an attempt to leverage the unique properties of nanofillers and improve the overall performance of the material. A variety of reinforcing agents were utilized, namely cellulose nanocrystals (CNC), montmorillonite (MMT), graphene nanoplatelets (GNP) and titanium dioxide (TiO2), to understand the effect of each filler on the physicochemical properties of the polyester. Formulations of these polyesters were then prepared and processed on a digital light processing (DLP) 3D printer to prepare test specimens. Extensive thermomechanical characterization showed that the interference of the fillers with the UV curing process was the main parameter determining the mechanical performance of the 3D printed materials.

Uranium-zirconium hydride nuclear fuel performance in the NaK-cooled MARVEL microreactor

The Microreactor Applications Research Validation and EvaLuation (MARVEL) Project is producing a high temperature NaK-cooled nuclear reactor test bed at the Idaho National Laboratory to ultimately improve integration of microreactors to end-user applications. This ambitious effort seeks to design, authorize, construct, test, and operate the reactor within five years. The computational software package chosen for high fidelity fuel performance modeling, BISON, has been upgraded to model the performance of the MARVEL reactor's selected fuel system: 304 stainless steel-clad U-ZrHx. In this manuscript, we begin by describing the MARVEL fuel element. The known properties and relationships of the fuel element constituents are recapitulated from data available in the literature. These historical relationships assume a particular U-ZrH microstructure which previously was not well-understood; therefore, the fuel's microstructure is experimentally confirmed using electron microscopy and X-ray diffraction. This information is then used to analyze the thermomechanical performance of the MARVEL fuel element during a hypothetical extreme accident scenario (a loss of flow accident during a loss of coolant pressure accident) using the nuclear fuel performance code BISON. The analysis shows that the primary phenomenon which could compromise the structural integrity of the MARVEL fuel element is the same as for TRIGA reactors: high temperature internal gas overpressurization-induced rupture of the cladding arising from excessive hoop stresses. Despite modeling the most severe MARVEL accident scenario, the highest anticipated temperature in the fuel, about 718 °C, results in hoop stresses of less than 10 MPa. Based on this analysis, a conservative steady state fuel meat temperature limit of 900 °C precludes cladding damage. The newly incorporated fuel performance simulation capabilities developed in this work may also be extended to model this fuel system under other conditions or reactors.

Centrifuge modelling of end-bearing slender energy pile performance under temperature cycles

Slender energy pile shows a buckling deformation behavior under the coupling effect of temperature cycles and external loads, significantly affecting the long-term serviceability and even leading to the buckling failure. To investigate the thermo-mechanical performance of end-bearing slender energy piles under the long-term effect of temperature cycles, a centrifuge modelling experiment was conducted in this work, in which the temperature distribution, displacement, axial force and bending moment of the energy pile during the long-term temperature cycle were measured. The results unveiled that the axial force of the end-bearing slender pile increases as temperature rises, potentially leading to a displacement neutral point in the lower part of the pile. Meanwhile, there was an embedding effect in the lower part of the slender pile, with a preliminary calculated embedment depth of 36.2 meters. Temperature fluctuations can soften the soil at the pile end over time, diminishing the embedding effect on slender piles, and causing a reverse bending point to emerge at a depth of 45.5 meters. The appearance of bending moments in the pile signaled the horizontal displacement encountered in the pile service life, warning the bearing capacity loss problem from changes in pile deflection.

Thermomechanical performances of epoxy complex with castor oil-based polyglycidyl ethers as efficient toughness and strength agents

Thermomechanical performances of epoxy complex with castor oil-based polyglycidyl ethers as efficient toughness and strength agents

In-situ hybridization of an epoxy resin using polyurethane and MXene nanoplatelets for thermally stable nanocomposites with improved strength and toughness

A novel ternary composite system has been developed by combining MXene nanoplatelets with pre-polyurethane (PU) and an epoxy (EP) resin through in-situ polymerization and solution blending. Our approach aims to enhance the strength and toughness of the EP matrix while maintaining its thermal stability. The strong compatibility between isocyanate-terminated PU and hydroxyl-terminated MXene with the resin was demonstrated through chemical grafting and hydrogen bonding processes. In this ternary composite, significant improvements were observed, including a 32 % increase in tensile strength, a 46.4 % increase in flexural strength, and a 13.4 % increase in fracture toughness, even at very low filler contents of 0.05 wt% for MXene and 1 wt% for PU. A thorough examination of the fractured surfaces revealed the underlying mechanisms responsible for the improved strength and toughness. These mechanisms involve a transition from a brittle to a ductile fracture mode, which can be attributed to the combined effects of thermoplastic toughness, strong chemical bonding between PU and EP, and crack-anchoring and bridging effects facilitated by MXene nanoplatelets. The results presented herein are relevant to a wide range of applications in aerospace, automotive, electronics and various other industries where durability and thermomechanical performance of materials are critical.

Optimizing the thermomechanical and thermal performance of epoxidized natural rubber hybrid nanocomposites using graphene and carbon nanotubes

Optimizing the thermomechanical and thermal performance of epoxidized natural rubber hybrid nanocomposites using graphene and carbon nanotubes

Scopes for Improvements in Energy Conservation and Thermomechanical Performance of Building Blocks in the Kingdom of Bahrain: A Literature Review

In regions with hot climates such as Bahrain, the utilization of air conditioning is indispensable in both public and private buildings to attain thermally comfortable indoor environments. External walls, constructed with building blocks, play a crucial role in the heat penetration into the building system. Despite extensive research on the cavity designs of building blocks, there has been a lack of comparison between individual block systems and integrated multi-block systems, considering both thermal and mechanical performance criteria simultaneously. Therefore, it is imperative to gather and review information on key parameters influencing the thermomechanical performance of building blocks, along with investigating techniques used to evaluate these parameters according to international standards. This review primarily focuses on these aspects. Additionally, it presents the historical evolution of housing types and the standard procedures followed by the Bahraini Government and block manufacturing companies in alignment with energy efficiency policies in Bahrain. Ultimately, this review aims to inspire researchers to explore other viable and innovative designs for enhancing the thermal insulation of building walls. By doing so, this work will contribute to Bahrain’s 2030 goals of fostering sustainability and mitigating environmental impact at a local level, while also aligning with the United Nations’ Sustainable Development Goals (SDGs) for 2030, specifically SDG 11, which aims to “make cities and human settlements sustainable”.

Long-term thermo-mechanical performance evolution of a 15-cell solid oxide fuel cell stack

Understanding mechanical performance evolution and failure mechanism of solid oxide fuel cell stack (SOFCs) during long-term operation period are essential to prolong operation life and advance commercialization. In this study, based on the structural mechanical model, the evolution characteristics of thermal stress, failure probability, strains, and deformation of SOFCs fueled by partially pre-reformed CH4 during 3000 h' operation are revealed. It's found the maximum thermal stresses of anodes, sealants, and frames/ICs decease respectively by 82.9%, 74.1%, and 88.4%, while those of electrolytes and cathodes firstly fluctuate then increase. The failure probabilities of sealant and anode decrease by 6∼10 orders of magnitude, while increase by 1 order of magnitude and 1.5 times for electrolyte and cathode. 300 h later, sealant may fracture by creep strain, while the component most likely to fail due to thermal stress changes from sealant to cathode. The maximum deformation of positive electrode-electrolyte-negative electrode (PEN) locates in anode of cell 15. It is suggested creep resistance of sealant be improved to avoid creep fracture, mechanical strength of cathode/sealant be increased to decrease failure probability, and the temperature unevenness be decreased to avoid larger deformation.

Thermofluid-dynamic and thermal–structural assessment of the EU-DEMO WCLL “double bundle” Breeding Blanket concept left outboard segment

As part of the activities performed by the DEMO Central Team (DCT) to study alternative configurations of the Water-Cooled Lead Lithium (WCLL) Breeding Blanket (BB), to overcome the open issues that emerged at the end of the Pre-Conceptual Design phase, a new concept, the WCLL BB “double bundle” (db), was developed. This concept adopts an array of db tubes poloidally distributed inside the breeding zone, mimicking the arrangement inside heat exchangers. These are coaxial pipes the gap between which is filled with PbBi (or alternatively with gas and fins), which avoids direct contact between PbLi and water in case of in-box LOCA events. Similarly, the First Wall channel cooling water is separated from the PbLi. The use of PbBi as an inert fluid makes the Segment Box (SB) sizing less stringent: in the case of an in-box LOCA due to a break of the water cooling circuit inside the BB SB, the pressurized volume is only the PbBi one, instead of the whole SB volume as in the reference WCLL design configuration. Consequently, the total amount of steel inside the BB can be reduced, with benefits in terms of increased tritium breeding ratio. Within this framework, University of Palermo, in support of the DCT and under the EUROfusion action, preliminarily analysed the steady-state thermal, thermo-hydraulic and normal and off-normal thermo-mechanical performances of this concept, following a theoretical-numerical approach based on finite volume and finite element methods, and adopting the ANSYS CFX and ANSYS Mechanical codes. The analyses carried out allowed a preliminary optimization of the design, improving the thermal and thermo-mechanical performances of the WCLL-db BB, in compliance with the design requirements, while reducing the total steel amount. Models, assumptions and main results are herewith reported and critically discussed.

The role of organic solvent and nano-additives loading in preparing and characterizing graphene oxide based polystyrene nanocomposites

ABSTRACT In this work, two types of organic solvents: namely, dimethylformamide (DMF) and tetrahydrofuran (THF); were investigated individually to prepare graphene oxide (GO) based polystyrene (PS) nanocomposites. Both were effective exfoliation agents for GO nano-sheets using sonication process. However, DMF showed poor solubility for PS beads compared to THF due to its high boiling point, poor volatility, and the prevailing monomer–monomer interaction rather than monomer–solvent interaction. Hot pressing was not an efficient preparatory approach for those samples prepared by DMF. Hence, solution casting, and THF were adopted to prepare PS and its GO-based nanocomposites. (0.5 and 1.0) wt. % of GO were dispersed homogeneously in PS using different dispersive techniques. Range of properties were tested for the pure polymer and its GO-based nanocomposites prepared by THF. A good dispersion of GO nano-sheets in PS was observed by different microscopic techniques. A significant improvement of mechanical and thermo-mechanical (storage modulus) performances for the polymer nanocomposites (PNCs) were achieved compared to the pure polymer. Young’s modulus for PS/GO nanocomposites was improved by 122% and 143% for GO loadings of 0.5 and 1.0 wt. %; respectively, and storage modulus for the nanocomposites recorded a considerable promotion compared to the pure polymer.

A Meso-scale study to predict high-temperature behavior of concrete structures in a hygral-thermal-chemical-mechanical framework

Fire has become one of the common hazards that a concrete structure faces in today’s world. Considering the heterogeneity of concrete and the contrasting nature of the constituents at high temperatures (cement paste dehydrates and shrinks while aggregate expands in volume), the use of a homogeneous macroscopic model to predict concrete's thermo-mechanical performance is questionable. Therefore, a more realistic description of concrete (in terms of explicit consideration of coarse aggregate and cement mortar rather than homogenized concrete medium) is needed to characterize the behavior of a concrete structure under such severe loading conditions (e.g., fire). In fact, the performance of a macro-scale (meter size or higher) concrete structure is the coupled effect of the various physico-chemical processes that occur within its constituents at meso-scale, a scale (mm-cm scale size) where coarse aggregates are randomly distributed in a mortar paste medium. Therefore, it is required to develop a model that explicitly considers the constituents' contrasting nature and the different thermo-hygral-mechanical processes at the scale of occurrence of these processes. Hence, in this contribution, a meso-scale based model is developed in a coupled hygro-thermo-chemo-mechanical (HTCM) framework to investigate the effect of high temperature on the thermo-mechanical performance numerically (e.g., in terms of spalling, deformation, residual capacity, etc.) of fire-exposed plain and reinforced concrete structural elements (e.g., slab, beam, etc.). Simulated results and validation with experimental data (taken from the literature) highlight several crucial aspects related to obtaining a more precise residual capacity of a concrete structure, which is impossible to reproduce with a homogenized macroscopic model. The study highlights that the failing of random concrete parts at different times during high-temperature exposure can not be simulated with a homogenized assumption. Further, a mesoscopic model does not require transient creep strain to be specified explicitly. The primary influencing factors behind this transient creep strain, such as the different thermo-chemical and thermo-mechanical damage of the concrete constituents (cement paste, aggregate), thermal-incompatibility of the components and associated damages, etc., are implicitly taken into account in a meso-scale model.

Thermomechanical characterisation of reprocessable, siloxane-based, glass-fibre-reinforced vitrimers

Polymer composites have been extensively used for the last 30 years in the automotive, green-energy, maritime and aerospace industries. While the demands of composites' applications are increasing, complications are arising regarding their sustainability. In this work, a siloxane-based vitrimer with fast stress-relaxation, and its Glass-Fibre-Reinforced Vitrimer (GFRV) were manufactured and mechanically characterised as a sustainable alternative to thermoset composites produced by infusion. Dynamic mechanical analysis and differential scanning calorimetry were performed to identify the ageing effect on the glass-transition temperature of the materials. Tensile and in-plane shear tests were executed to investigate the materials’ performance at elevated temperature. The results were compared to the ones of a thermoset benchmark and showed that after ageing and up to 50 °C, both the neat vitrimer and its corresponding composite exhibited a thermomechanical performance comparable to their thermoset counterparts. GFRV specimens were then successfully reprocessed by hot-pressing up to two consecutive cycles. The GFRV specimen was thermoformed into an omega-stiffener profile by the first hot-pressing cycle, while its flat profile was restored during the second cycle. Finally, the reprocessing results were evaluated by optical microscopy, demonstrating that the newly developed advanced GFRV is indeed a viable, sustainable alternative.

Unique Method for Facile Postsynthetic Modification of Nonisocyanate Polyurethanes.

Nonisocyanate polyurethanes (NIPUs) are broadly investigated as a potential replacement for conventional polyurethanes (PUs) to eliminate the use of toxic isocyanates and reduce occupational hazards. One of the most popular approaches to NIPU synthesis is the polyaddition of cyclic bis(carbonate)s and diamines to form poly(hydroxyurethane)s (PHUs). However, such PHUs are highly hydrophilic due to the presence of two hydroxyl groups per repeat unit, and the resulting moisture absorption significantly degrades their thermomechanical performance and physical stability upon exposure to humidity, thus limiting their utility. Here, we introduce a simple and scalable approach for the modification of PHUs to increase hydrophobicity and adjust their properties. The proposed reaction between aldehydes and appropriately spaced hydroxyl groups in the polymer backbone resulted in high degrees of modification (up to 84%) and up to 3-fold reductions in water uptake at 85% RH. Furthermore, the use of aromatic aldehydes in particular enabled the retention of mechanical properties over a wide range of humidity levels, resulting in performance comparable to conventional PUs. Finally, we note that this approach is not limited to reducing moisture sensitivity alone and provides ample opportunities for imparting a broad range of novel properties to PHUs through an appropriate selection of functional aldehydes.

Investigation of the structure-property relation for graphene oxide based acrylonitrile butadiene styrene nanocomposites

The improvement of the structure-property relation in nanocomposites between different polymer matrices and the embedded nano-additives has become a strategic blueprint for many academic counterparts around the globe. In this work, different loadings of graphene oxide (GO) varied from 1.0 to 3.0 wt. % were mixed with acrylonitrile butadiene styrene (ABS) using solution casting approach. The resulted nanocomposites underwent to spectral, structural, morphological, mechanical, thermal and thermomechanical tests. Different kinds of instruments associated with each test were employed to draw a professional conclusion about the potential improvement in structure-property relation. The targeted improvement was achieved as spectral, structural and morphological investigations confirmed the interaction, structural variation, and good dispersion of GO in ABS; respectively. Furthermore, as GO loadings went higher, the mechanical, thermal, and thermomechanical performances for the nanocomposites were improved compared to the neat polymer. Young’s modulus, tensile strength, thermal decomposition, and visco-elastic properties showed an enhancement compared to the neat polymer. The mechanical and thermomechanical performances for the nanocomposites recorded significant promotions.

Contribution of silane modification of halloysite nanotube to its poly (butylene terephthalate)-based nanocomposites: structural, mechanical and thermal properties

Polybutylene terephthalate (PBT) nanocomposites were melt-blended with two types of Turkish halloysite nanotubes (HN). Naturally occurring HN samples were used to produce PBT-based composites at the HN compositions of 1%, 3%, 5%, and 10%. Findings of neat and silane-coated HN-containing composite samples were compared to investigate the interfacial adhesion between polymer matrix and reinforcement material. According to test results, a 1% amount of HN was found to be the most suitable option in the case of mechanical and thermal properties of composites. Additionally, silane-modified grade displayed highly indicative improvements compared to pristine HN clay due to better interfacial adhesion of halloysite nanotubes to the PBT matrix was accomplished. Property enhancements achieved for composite samples containing low contents of HN were confirmed by morphological examinations. As a result, the PBT/ 1% HN-S composite sample was bookmarked as the most suitable option to fabricate HN-reinforced PBT-based nanocomposites in terms of mechanical, thermo-mechanical, morphological, thermal, and physical performances based on the findings in this study. Silane-modified halloysite grades exhibited better results, and they were found to be more suitable in the case of applications of PBT.Graphical abstract

Thermomechanical performance analysis of MicroPCM-enhanced energy pile concrete: A multiscale numerical study and formulation design implications

Energy pile is a form of pile foundation that combines load-bearing and heat exchange, marking a pivotal avenue for harnessing geothermal energy. Recent strides in research have highlighted the incorporation of microencapsulated phase change materials (MicroPCM) into energy piles due to their potential to amplify heat transfer efficiency. The thermomechanical behavior of phase change energy piles, however, becomes intricate owing to the dual impact of thermal and mechanical loads. Thus, a holistic multiscale analysis remains indispensable to grasp the repercussions of varied MicroPCM concentrations on the thermomechanical attributes of phase change concrete and the dominant mechanisms driving their thermo-mechanical performance. In the study, we propose an innovative multiscale numerical model to investigate the thermomechanical performance of MicroPCM-enhanced energy pile concrete, taking into account the randomly distributed MicroPCM particles and aggregate. The sensitivity analysis pinpointing the intrinsic determinants of phase change concrete was conducted to discern the pivotal contributors to its thermomechanical response. Core insights revealed that while MicroPCM addition might compromise the mechanical strength of concrete owing to its inherently weaker properties, it unquestionably bolsters the thermal characteristics of phase change concrete. The thermal conductivity of phase change concrete stands in inverse relation to its porosity and direct correspondence with its saturation level. Correlation evaluations ascertained that the thermal prowess of phase change concrete is predominantly swayed by saturation, followed by porosity, and lastly, MicroPCM content. This inquiry endeavors to elevate the heat transfer efficacy of energy piles by finetuning the formulation design of phase change concrete materials, shedding light on underlying mechanisms, and laying a robust foundation for the forthcoming adoption of MicroPCM energy piles.