Mechanical Performance Research Articles

Mechanical performance and anisotropic analysis of rubberised 3D-printed concrete incorporating PP fibre.

The research investigates the effects of substituting sand with rubber particles derived from waste tyres-up to 40% by volume-and the inclusion of polypropylene (PP) fibres. Unlike steel fibres, which can cause operational challenges and surface irregularities in the printing process, PP fibres' flexibility integrates well within the concrete matrix. This integration ensures smooth extrusion and a high-quality surface finish, enhancing the printability of the concrete. The study's findings reveal that including rubber particles and PP fibres impacts the concrete's properties, showing a general decline in compressive and flexural strengths as the rubber content increases. Nevertheless, the PP fibre-enhanced mixtures maintain sufficient structural strength, demonstrating an anisotropic compressive strength above 30MPa and a flexural strength of 4MPa. These results underscore the feasibility of using rubberised 3D-printed concrete with PP fibres in sustainable construction practices, aligning with standards (ACI 318:2018) and contributing to eco-friendly and innovative construction methodologies.

Structural implementation of recycled lump prepared from waste concrete after elevated temperatures: Mechanical and environmental performances

To find a sustainable treatment for construction and demolition waste, the utilization of recycled lump (RL) prepared from waste concrete after elevated temperatures as coarse aggregate in concrete was investigated. The mechanical and environmental properties of recycled lump concrete (RLC) and reinforced recycled lump concrete (RRLC) were discussed with three RL replacement ratios and five treatment temperatures. The results show that increasing the RL replacement ratio would reduce the slump, and axial compressive performance of RLC, resulting from the presence of old adhered mortar on RL. The treatment of elevated temperature for RLC would improve the adverse effect of increasing the RL replacement ratio, resulting from the decreasing amount of old adhered mortar and interfacial transition zone on RL. The prediction formulas for the mechanical model of RLC were proposed while the design method for the axial compressive strength for RRLC was modified against the existing standard to conduct the full-range parametric analysis. The environment assessment indicates that the sustainable utilization of RL as coarse aggregate could reduce the environmental impact and global warming from concrete production whilst the RL prepared from waste concrete after 400oC treatment is an appreciated option for the production of RLC and RRLC products from a mechanical and environmental perspective. In addition, the increase in external diameter would remarkably dwindle the environmental impact caused by the utilization of RL in structural members.

A Review of Anode Materials for Dual-Ion Batteries.

Distinct from "rocking-chair" lithium-ion batteries (LIBs), the unique anionic intercalation chemistry on the cathode side of dual-ion batteries (DIBs) endows them with intrinsic advantages of low cost, high voltage, and eco-friendly, which is attracting widespread attention, and is expected to achieve the next generation of large-scale energy storage applications. Although the electrochemical reactions on the anode side of DIBs are similar to that of LIBs, in fact, to match the rapid insertion kinetics of anions on the cathode side and consider the compatibility with electrolyte system which also serves as an active material, the anode materials play a very important role, and there is an urgent demand for rational structural design and performance optimization. A review and summarization of previous studies will facilitate the exploration and optimization of DIBs in the future. Here, we summarize the development process and working mechanism of DIBs and exhaustively categorize the latest research of DIBs anode materials and their applications in different battery systems. Moreover, the structural design, reaction mechanism and electrochemical performance of anode materials are briefly discussed. Finally, the fundamental challenges, potential strategies and perspectives are also put forward. It is hoped that this review could shed some light for researchers to explore more superior anode materials and advanced systems to further promote the development of DIBs.

Opportunities and challenges with implementing a recycling program for municipal solid waste incineration (MSWI) bottom ash as a construction aggregate: A programmatic review.

The incineration of municipal solid waste (MSW) produces byproducts known as MSW incineration (MSWI) ash. The reuse of MSWI ash as a construction material prevails in several areas of the world, namely Europe and Asia, however, reuse in the United States (US) lags due to regulatory requirements for disposal practices. Developing a recycling program for MSWI ash provides an alternative end-of-life disposal scenario for material currently landfilled and supplements the reliability on mining of natural aggregates. This study provides a programmatic review of the past decade of challenges and opportunities a local government in the US has experienced to implement a recycling program for their MSWI bottom ash (BA) as a construction aggregate in road materials such as hot mix asphalt, concrete pavement, and road base. The regulatory and practical challenges in the US are presented, including meeting mechanical and environmental performance requirements (e.g. strength and leaching-to-groundwater). The novel approach to overcoming these challenges includes blending the MSWIBA from two facilities with common aggregates, creating suitable construction materials. Interfacing with local and state agencies such as the Department of Environmental Protection and Transportation resulted in additional testing to establish the MSWIBA as a beneficial use material and obtain essential approvals for advancing reuse opportunities. This paper synthesizes available data regarding the challenges, opportunities, and implementation of this recycling program by reviewing the experiences of an MSWI facility in the US to provide fundamental guidance to those considering similar applications.

Development of high-strength geopolymer mortar based on fly ash-slag: Correlational analysis of microstructural and mechanical properties and environmental assessment

Given the insufficient mechanical performance of existing fly ash-based geopolymer mortars under ambient curing conditions, this study is dedicated to developing a high-strength geopolymer mortar that meets the requirements of modern structural engineering. Based on the rheological performance tests of the fresh geopolymer mortar, the evolution of its rheological characteristics was revealed. Through macroscopic mechanical performance tests, the influence of slag content on the compressive and flexural strength of geopolymer mortar was clarified. Employing microstructural performance testing methods such as Thermogravimetric and Mercury Intrusion Porosimetry, the micro-mechanisms behind the improvement of mechanical properties were revealed. Utilizing the grey relational analysis method, a framework was established to analyze the correlation between the microstructural and macroscopic mechanical properties of geopolymer mortar. Additionally, an assessment system for evaluating environmental and economic benefits was developed using statistical analysis methods. The results show that increasing slag content enhances the yield stress and plastic viscosity of geopolymer mortar. Optimizing slag content boosts the compressive strength of fly ash-based geopolymer mortar, reaching up to 88.13 MPa under ambient curing conditions. An optimal amount of slag also promotes gel formation during polymerization, improving the internal pore structure. Furthermore, the content of reaction products correlates more strongly with macroscopic mechanical properties than pore structure characteristics. Geopolymer mortar also presents significant environmental and economic advantages over traditional cement-based materials, with its carbon and economic intensity indices at only 5.50 % and 10.80 %, respectively, of those in cement-based materials.

Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Self-Reinforced Composites via Solvent-Induced Interfiber Welding of Nanofibers.

In this study, we explore an approach to enhance the mechanical performance of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by utilizing the self-reinforcing effect of β-phase-induced PHBV electrospun nanofiber mats. This involves electrospinning combined with low-temperature postspun vapor solvent interfiber welding. Scanning electron microscopy imaging confirmed fiber alignment, while XRD diffraction revealed the presence of both α and β crystalline phases under optimized electrospinning conditions. The resulting composite exhibited significant improvements in mechanical properties attributed to the formation of more perfectly structured α and β polymorphs and enhanced interfacial adhesion of electrospun nanofibers after vapor solvent treatment. This approach offers entirely recyclable and biodegradable materials, presenting the potential for a new family of sustainable bioplastics.

One-Step Synthesis of Graphene-Covered Silver Nanowires with Enhanced Stability for Heating and Strain Sensing.

Solution-processed silver nanowire (AgNW) networks have been considered as promising electrode candidates for next-generation electronic devices. However, they suffer from poor thermal and electrical stability and low mechanical properties, hindering their practical applications. In this work, graphene nanosheets are successfully introduced into AgNW via a facile one-step solvothermal process. Benefiting from increased conductive paths, the resultant AgNW/graphene films exhibit high electrical conductivity. More importantly, the interlocking NW morphology can be maintained under high temperature and applied voltage due to suppressed Ag migration, which is enabled by the introduction of graphene. This feature leads to enhanced thermal and electrical stability, making them suitable for use as transparent heaters. Furthermore, the composite films present excellent mechanical performance, and negligible resistance change is observed after 10 000 repeated bending cycles. To demonstrate their feasibility toward sensor applications, sandwiched strain sensors are designed, which can endure larger tensile strains and show higher sensitivity and repeatability compared with pure AgNW-based device. Furthermore, various hand gestures can be easily recognized by the resultant sensors based on unique combinations of sensing response. This work not only provides a low-cost method to realize large-scale synthesis of AgNW/graphene composites but also offers guidance to prepare high-performance electrodes for advanced electronics.

Multi-objective optimization design of a circular core paper sandwich panel

Abstract Ensuring sufficient mechanical performance while enabling lightweight design is critical for utilizing paper sandwich panels in the furniture industry. To design lightweight sandwich panels that balance mechanical properties and cost, this study developed a circular core paper sandwich panel (CCPSP) and investigated its structural efficiency using multi-objective optimization. The response surface method (RSM) based on Box–Behnken design was utilized to establish mathematical models relating the paper tube spacing, inner diameter, and height to the out-of-plane compressive strength, density, and cost. The resulting models effectively revealed the coupled effects of the parameters on the responses. Subsequently, the models were optimized using the non-dominated sorting genetic algorithm II (NSGA-II) to find the Pareto optimal trade-offs between maximizing compressive strength while minimizing its density and cost. The optimization solution resulted in an optimal set of paper tube geometries that maximized the structural efficiency of CCPSP. Overall, lower tube height conferred superior structural efficiency, while tube spacing and diameter were constrained. The results highlight the potential of CCPSP as an efficient and sustainable material for furniture manufacturing, enabled by multi-objective optimization of its structure.

Mechanical Performance of Bentonite Plugs in Abandonment Operations of Petroleum Wells

This study aims to evaluate how the operational procedure adopted for pellet placement and the exposure to subsurface conditions influence the mechanical integrity of bentonite plugs used as barrier elements in the abandonment of petroleum wells. To this end, the plugs were formed by hydrating the pellets directly in water, simulating the onshore procedure, while the offshore plugs were obtained from pellets hydrated in deionized water after immersion in diesel or olefin, which are suggested as displacement fluids. The plugs obtained were tested by compression and adhesion tests. These mechanical tests were also carried out for specimens obtained from plugs exposed to four formulations of synthetic formation waters. The results obtained demonstrated that, in the offshore procedure, the previous contact with olefin may adversely affects the mechanical stability of bentonite plugs, while plugs formed from pellets immersed in diesel presented satisfactory mechanical properties. However, the contact with formation water evidenced that the onshore plug presents superior resistance than the offshore plug previously immersed in diesel. The highly successful performance of the onshore plug was attested by the maintenance of the compressive strength, which exhibited a maximum reduction of 13%, even after exposure to the most saline formation waters.

Dual role of epoxidized soybean oil (ESO) as plasticizer and chain extender for biodegradable polybutylene succinate (PBS) formulations

This work reports the effect of 1-5 wt% epoxidized soybean oil (ESO) addition on the thermal, mechanical, and morphological properties of polybutylene succinate (PBS). ESO acts as a chain extender as well as a mild plasticizer of PBS. N-methylimidazole (NMI) is used as a catalyst to promote the reaction between PBS and ESO, and thermal, rheological, and spectroscopic analyses demonstrate increased viscoelastic properties, compatibility, crystallinity and thermal stability of the melt reacted formulations. In the presence of NMI, storage modulus (G’) values two orders of magnitude higher than that of pure PBS are achieved, confirming the completion of the chain extension reaction. A drastic refinement of the biphasic structure of the blend is observed, with the formation of a homogenous structure where ESO is well incorporated into the matrix. Finally, tensile tests reveal enhanced mechanical performance in the blends reacted in the presence of NMI. These findings pave the way for the development of a versatile family of materials which could find potential application in sustainable biodegradable packaging.

Study on the Reinforced Properties of Geopolymer Fibers with a Sustainable Development Role

Geopolymers are of great significance in reducing the consumption of mineral resources, saving energy, protecting the environment, and realizing sustainable economic and social development. This experiment investigated geopolymer mortar with fly ash and metakaolin as the primary binders, assessing the impact of different fiber types and volume fractions on the mortar’s flexural and compressive strength. The results indicated that optimal mechanical properties could be achieved with a fly ash-to-metakaolin ratio of 35:65. The mechanical performance is the best, with a compressive strength of 54 MPa, a flexural strength of 3.4 MPa, and a split tensile strength of 1.9 MPa at 28 days. Different fibers influenced the splitting tensile strength to varying degrees; with a 1.5% volume fraction of steel fibers, geopolymer mortar exhibited the best reinforcement effect, showing a 70% increase in flexural strength and a 142% increase in tensile strength. Mechanistic analysis revealed that the reinforcement from refined various fibers could refine the structure and further enhance the strength. Of steel geopolymer fibers’ The reinforcing effect of steel fibers is the best among them, and the internal structure is the most compact. The geopolymer mortar hydration products of geopolymer mortar reinforced with PP fibers, PVA fibers, steel fibers, and carbon fibers were amorphous network-structured zeolites (Na2[Al2Si3O10]·2H2O). The limitations of geopolymers can be effectively addressed through the aforementioned research, which can effectively reduce the use of cement and achieve the goal of sustainable development.

Interpenetrated Multinetwork Hybrid Aerogels by Layered Montmorillonite and One-Dimensional Hydroxyapatite Fibers for Heat and Fire Insulation.

It is of practical significance to develop aerogels with effective thermal insulation characteristics together with fireproof properties as well as high mechanical strength. Here, an interpenetrated multinetwork hybrid aerogel realizing thermal insulation, flame retardancy, and high compression modulus is demonstrated. Specifically, one-dimensional hydroxyapatite nanowires (HAP) played dual roles as the aerogel support skeleton to entangle with layered montmorillonite (MMT) each other to form a three-dimensional interpenetrated multinetwork structure and to optimize the thermal conductivity by adjusting the pore space in current HAP/MMT/PVA hybrid aerogels. Therefore, the interpenetrated multinetwork hybrid aerogels exhibit superior thermal insulation performance in room temperature (0.033 W m-1 K-1, 298 K, air conditions) and largely enhanced ultrahigh compression modulus (80 MPa). Moreover, the obtained hybrid aerogels also exhibit excellent flame retardancy and self-extinguishing smoke suppression properties (peak heat release rate and total smoke production as low as 92.44 kW m-2 and 0.1 m2, respectively), which is the outstanding interpenetrated multinetwork hybrid aerogel that has achieved synergistic improvement in heat and fire insulation and mechanical performance. Therefore, the interpenetrated multinetwork hybrid aerogels are promising candidates for efficient heat insulation, fire prevention, and mechanically robust applications.

Ceramic waste powder as a cement replacement in concrete paving blocks: mechanical properties and environmental assessment

ABSTRACT In the quest for eco-friendly alternatives to ordinary Portland cement, a material extensively used in the manufacture of concrete paving blocks, this study explores the potential of ceramic waste powder. Towards this, a parametric investigation is conducted into the effects of substituting cement with ceramic waste powder on the mechanical properties and durability performance of mass-produced pressed concrete blocks. The findings reveal that the incorporation of ceramic waste powder as a partial cement replacement can markedly enhance the strength and durability of the paving blocks. Specifically, mixtures, containing 20% and 30% ceramic waste powder, demonstrated an increase in compressive and tensile strength by 30% and 19%, respectively, compared to their control counterparts. In addition, the modified blocks exhibited a decrease in water absorption and weight loss after undergoing freezing and thawing cycles by 8% and 40%, respectively. A life cycle assessment corroborates the environmental viability of ceramic waste powder as a cement substitute, indicating reductions across all environmental impact categories, with notable improvements. This research paves the way for more sustainable solutions in pedestrian pavement construction, underscoring the potential of ceramic waste powder as a significant contributor to global sustainability efforts in the construction industry.

Solvent Engineering of Thermo-Responsive Hydrogels Facilitates Strong and Large Contractile Actuations.

Thermo-responsive hydrogels can generate the actuation force through volumetric transitions in response to temperature changes. However, their weak mechanical properties and fragile actuation performance limit robust applications. Existing approaches to enhance these properties have typically depended on additional components, leading to an unavoidable interference to the actuation performance. In this work, robust thermo-responsive hydrogels are fabricated through solvent engineering. A particular solvent, N-methylformamide, interacts affinitively with the carbonyl group of N-isopropylacrylamide monomer, solubilizes the monomer with extremely high concentration, stabilizes chain propagation during polymerization, and greatly increases chain lengths and entanglements of the resulting polymer. The synthesized hydrogels are highly elastic, strong, and tough, displaying remarkable thermo-responsive contractile actuation. The simple synthetic process can broaden its applicability in designing robust functional hydrogel applications.

Experimental study on mechanical properties and dynamic compression performance of basalt/polypropylene fiber high strength concrete

Concrete is a typical brittle material. Although it has excellent compressive performance, its shortcomings such as poor tensile strength and easy cracking cannot resist the damage of dynamic loads such as explosion and impact to a certain extent. In order to improve the impact resistance of concrete, the φ100 × 50 SHPB was used to carry out the impact tests of high-strength concrete specimens with volume contents of 0.1%, 0.3%,0.5% basalt fiber (BF) and polypropylene fiber (PPF) under three different impact pressures. The compressive strength, splitting tensile strength, flexural strength and dynamic compression performance of basalt/polypropylene fiber high strength concrete (C60) were studied. With the increase of impact pressure, increasing the volume content of fiber can significantly improve the impact resistance of high-strength concrete, which can give full play to the crack resistance and bridging effect of fiber. BF and PPF are sensitive to strain rate. Within a certain range of strain rate, the relationship between peak stress and strain rate is positively correlated. Finally, the dynamic stress-strain curves of the optimal content of two kinds of fibers are obtained through dynamic compression test.

The impact of coaxial gas technology on the morphology of powder by gas atomisation and the additive manufactured mechanical performance

ABSTRACT Metal powders are essential for additive manufacturing (AM), with their morphology significantly impacting the performance of AM components. Gas atomisation (GA) is a common method for producing metal powders due to its efficiency and cost-effectiveness. However, GAed powders often exhibit defects such as alien powders, satellite powders, and hollow powders, which can adversely affect the AM process. To address these challenges, coaxial gas technology has been introduced and analysed through numerical simulation. Our study involved comparing GA processes with and without coaxial gas technology to generate two types of powders. These powders were assessed using Synchrotron X-ray computed tomography (SXCT) and classification algorithms. The pores in AM components manufactured from these powders were examined using SXCT, and their mechanical properties were evaluated through tensile tests. The findings of our research validate the effectiveness of coaxial gas technology in reducing powder defects and enhancing the performance of AM components.

Numerical and Experimental Study on Balanced Performance and Axial Stiffness of Fiber-Reinforced Rubber Pipe

Balanced fiber-reinforced rubber (FRR) pipes not only provide displacement compensation when transporting pressurized media but also prevent additional forces and displacements from being exerted on the connected pipeline system. Investigating the balanced performance of FRR pipes and the axial stiffness of balanced pipes is crucial for optimizing pipeline design and improving the reliability of pipeline systems. This paper develops a numerical model of FRR pipes that considers the nonlinearity of the rubber material and the interaction between the rubber matrix and fiber-reinforced layers. Using this model, the balanced performance of the pipe is calculated, and its axial stiffness under combined internal pressure and axial load is analyzed. Numerical results are compared with experimental data for validation. The results indicate that the pipe’s balance is achieved through the combined effects of the elongation and rotation of the reinforcing fibers and the deformation of the rubber matrix, highlighting the significant impact of the rubber matrix on the mechanical performance of the FRR pipe. Furthermore, the pipe’s balanced performance and axial stiffness are highly sensitive to the winding angle of reinforcing fibers. The proposed numerical model fills the gap in using numerical methods to evaluate the balanced performance of FRR pipes and provides valuable insights for their design and optimization.

Polysquaramides.

Thermoplastics, while advantageous for their processability and recyclability, often compromise thermochemical stability and mechanical strength compared to thermosets. Addressing this limitation, we introduce an innovative approach employing reversibly cross-linked polymers, utilizing squaramide moieties to reconcile recyclability and robustness. Herein, we detail the synthesis of supramolecularly cross-linked polysquaramides through the condensation polymerization of diethyl squarate with primary and secondary diamines. This methodology embeds hydrogen-bonding squaramide motifs into the polymer chains, yielding materials with significantly enhanced storage moduli, reaching up to 1.2 GPa. Material characterization via dynamic mechanical analysis, creep-recovery, and stress relaxation experiments delineate a distinctive rubbery plateau across a broad temperature range, excellent creep resistance, and multimodal viscoelastic flow, respectively, attributable to the dynamic nature of the supramolecular cross-links. Additionally, the study showcases the modulation of glass transition temperature (Tg) by altering the monomer composition and stoichiometry, demonstrating the tunability of polymer viscoelastic properties through precise control over hydrogen bonding interactions. Overall, the incorporation of squaramide motifs not only provides the structural integrity and mechanical performance of these thermoplastics but also leads to engineering materials with tailored viscoelastic characteristics.

Effect of adhesion promoters on rheokinetics and roll peel strength of electrical steel stacks

Epoxy varnishes for stacked electrical steel are of high relevance for renewable energy and electric mobility technologies. Water-borne epoxy varnish systems are still under development, especially with regards to the improvement of the adherence to the steel substrate. The main objective of this study was to assess the potential of low molar mass, silane-based adhesion promoters (AP) with amine or glycidyl functional groups as to their effect on the crosslinking kinetics of coatings and the mechanical performance of electrical steel laminates.Model formulations with different types and contents of silane AP or in combination with a pre-crosslinker were based on a Bisphenol A diglycidyl ether, a dicyandiamide (DICY) crosslinking agent and an emulsifier. The amount of water was fixed to 45 m%. Model varnishes were prepared by shear emulsification at elevated temperatures. Varnishes were applied onto electrical steel sheets and partly crosslinked to the B-stage. Finally, coated steel sheets were stacked and laminated in a heated press.To examine the crosslinking kinetics under non-isothermal conditions, rheokinetic measurements were performed. While the curing onset temperature of formulations with amine-based AP dropped by ∼10 °C, the effect of the epoxysilane AP was less pronounced (drop by ∼5 °C). Pre-conditioning of the varnishes in A-stage revealed a further reduction of the curing onset temperature associated with significantly higher initial viscosity. This was a clear indication for pronounced pre-crosslinking in A-stage and hence, a limited shelf life of silane-modified varnishes. The glass transition range in the fully cured state was solely affected by the diamine-based AP. Interestingly, the investigated low molar mass silane APs had no significant positive effect on the roll peel strength of the laminates.

Effects of liquid lubricants on the surface characteristics of 3D-printed polylactic acid

In this study, 3D-printed Polylactic acid (PLA) specimens were manufactured and polished using various lubricants to assess their surface, friction, and wear characteristics. After polishing, the surface roughness decreased by approximately 80% compared with that before polishing, except when acetone was used as the lubricant. In particular, under deionized (DI) water and acetone lubrication conditions, the friction coefficient decreased by 63% and 70%, respectively, whereas the specific wear rate decreased by 88% and 83%, respectively, compared with the unpolished specimens. In the case of dry polishing, adhesion, friction, and wear increase owing to surface damage. Ethanol and IPA polishing resulted in hydrolysis and increased friction, but slightly decreased wear rates. The surface of the specimen polished with acetone dissolved and became very rough. Only the surface polished with DI water exhibited hydrophobic properties. When acetone and DI water were used as lubricants, the surface adhesion force, adhesion energy, friction coefficient, and wear rate were lowest. The finite element analysis results showed that the polished surface exhibited stable contact pressure and friction force, while the unpolished surface showed large fluctuations in contact pressure and friction force owing to the laminated pattern. These results suggest that the polishing process is crucial for improving the surface characteristics and mechanical performance of 3D-printed PLA parts.