Improved Crack Resistance Research Articles

Geometric tunability of interlaminar resistance

The inherent weakness and variability in the interlaminar properties of composites and associated delamination pose significant challenges, compromising the performance of composite structures. This study investigates a strategy to tailor the apparent interlaminar resistance by altering the geometry of the interface to control crack propagation. We have developed analytical models, which propose a formulation that links the geometry, i.e. the interface width change rate and shape factor of the crack growth plane, with the reaction force–displacement curve. The results obtained, a family of power law relations followed during interlaminar crack growth, indicate that the analytical formulation is valid for all geometries tested, including those with significant width change rates; however, it may not always be easy to use or interpret. An approximated solution, constrained to slowly varying geometries, is also proposed. The limits of using this model are presented and discussed. The final validation of the models is performed using numerical and experimental approaches, considering the delamination of carbon fiber laminates. This work offers new insights into the design of composites and the fracture process in general, featuring unique shapes and improved crack resistance. It also addresses practical issues, e.g., related to composite repairs, which can enhance the performance and longevity of composite structures. Specifically, the proposed formulations can be easily adopted to obtain optimized patch geometries.

Effect of nano-metakaolin on the early-age fracture properties of cement mortar

In this paper, the fracture performance of nano-metakaolin (NMK) cement mortar during early hydration period was investigated. Different NMK contents (0 %, 3 %, 5 %, 7 %) were considered, and three-point bending tests were conducted. The digital image correlation technology and acoustic emission technology were utilized to analyze P-CMOD curves, initial fracture toughness, unstable fracture toughness, fracture energy, cumulative AE hits, and cumulative AE energy, AE source locations of cement mortar at early hydration stages. Furthermore, SEM experiments were utilized to analyze the mechanism by which NMK affects fracture performance of cement mortar. The results indicate that the incorporation of NMK enhances the fracture properties of cement mortar, with the most suitable NMK content being 5 %. The addition of NMK increases the cracking load, peak load, and the CMOD at the peak load of the cement mortar at 3 d, 7 d, and 14 d. The cracking load and fracture energy of the cement mortar with 5 % NMK increase by 22.5 % and 35.7 % respectively, compared to ordinary cement mortar at 14 d. NMK enhances the initial fracture toughness and unstable fracture toughness of the cement mortar, improving its crack propagation resistance. The unstable fracture toughness of the cement mortar is the largest when the NMK content is 5 % at 14 d, which is 31.6 % higher than that of ordinary cement mortar. Furthermore, NMK increases the cumulative AE energy and fracture energy of the cement mortar, increasing the cumulative ring counts and cumulative AE hits, causing the crack propagation path to deviate and resulting in improved crack resistance. The cumulative ring counts and AE hits for the cement mortar with 5 % NMK are 42.9 % and 66.2 % higher, respectively, than those for ordinary cement mortar at 14 d. NMK significantly modifies the cement matrix, thereby enhancing the fracture resistance of cement mortar.

Understanding Toughening Mechanisms and Damage Behavior in Hybrid-Fiber-Modified Mixtures Using Digital Imaging

Pavement cracking is a primary cause of early damage in asphalt pavements, and fiber-reinforcement technology is an effective method for enhancing the anti-cracking performance of pavement mixtures. However, due to the multi-scale dispersed structure of pavement mixtures, it is challenging to address cracking and damage with a single fiber type or fibers of the same scale. To investigate the toughening mechanisms and damage behavior of hybrid-fiber-modified mixtures, we analyzed the fracture process and damage behavior of these mixtures using a combination of basalt fiber and calcium sulfate whisker hybrid fiber modification, along with semicircular bending tests. Additionally, digital imaging was employed to examine the fracture interface characteristics, revealing the toughening mechanisms at play. The results demonstrated that basalt fibers effectively broaden the toughness range of the modified mixture at the same temperature, reduce mixture stiffness, increase residual load at the same displacement, and improve crack resistance in the mixture matrix. While calcium sulfate whiskers enhanced the peak load of the mixture, their high stiffness modulus was found to be detrimental to the mixture’s crack toughness. The fracture interface analysis indicated that the three-dimensionally distributed fibers form a spatial network within the mixture, restricting the relative movement of cement and aggregate, delaying crack propagation, and significantly improving the overall crack resistance of the mixture.

Research on the Prediction of Optimal Frequency for Vibration Mixing and Comparison on Initial Performance of Cold-Recycled Asphalt Emulsion Mixture.

The multicomponent cold-recycled asphalt emulsion mixture (CRAEM) has the ability of antireflection cracking between the base and the bottom surface layer, but it has secondary compaction and residual void, which is not conducive to crack resistance and fatigue performance. The application of high-frequency vibration mixing technology can reduce voids and improve crack resistance, but it is limited by the complexity of testing to determine the optimal mixing frequency. The fractal dimension of gradation is deduced by fractal theory, and the prediction model for optimal frequency is proposed. Dry, wet, freeze-thaw splitting tests, and rutting tests were employed to test the early mechanical properties of high-frequency vibration mixing specimens corresponding to different vibration accelerations, and mercury inclusion tests were utilized to compare the void distribution corresponding to the optimal mixing frequency and forced mixing, and to verify the prediction model for optimal frequency. The results indicate that the high-frequency vibration mixing technology is able to benefit the initial cracking resistance (28.1% increase), moisture stability (11.2% increase), and high-temperature stability on the macro level on the optimal frequency. Meanwhile, the void distribution structure can be optimized, reducing the proportion of harmful voids and increasing the proportion of transitional pores on the micro level. However, the freeze-thaw resistance needs to be further studied. This study reduces the number and cost of experiments to determine the optimal frequency, and provides theoretical guidance and technical support for the engineering application of the CRAEM.

Assessment of fracture toughness in fibrous concrete via Brazilian test: Experimental study with low-clinker cementitious binder

As the predominant and cost-effective material in the construction industry, concrete is susceptible to tension weaknesses, leading to significant flaws such as cracking and brittle fracturing. Recent advancements in fibrous concrete have emerged as a solution to mitigate these issues. Incorporating steel fibers in concrete has emerged as a promising solution to improve crack resistance and structural integrity. This study focuses on developing eco-friendly concrete using a low-clinker cementitious binder and short steel fibers to enhance fracture toughness and mitigate the environmental impact by effectively utilizing lime sludge. Concrete specimens were prepared with three binder types: treated lime sludge (TLS) at 15 % and 30 % and calcined clay (CC) at 15 % and 30 %, replacing conventional clinker. Short steel fibers were added at 1.5 % by volume to enhance mechanical properties. Fracture toughness was evaluated using notched Brazilian disc specimens, assessing mode I, II, and mixed-mode (I/II) fracture at multiple notch orientations (β = 0°, 15°, 28.83°, 45°, 60°, 75°, and 90°). Microstructural analysis during strength development was performed using scanning electron microscopy and X-ray diffraction. The findings revealed that specimens containing 15 % TLS, 30 % CC, and 1.5 % steel fibers exhibited the highest fracture toughness. Mode II fracture toughness exceeded mode I, indicating improved resistance to crack propagation. The addition of fibers to the specimens under mode II demonstrated improved fracture toughness, ranging from 0.44 to 0.53 MPa·m^1/2 compared to the corresponding non-fibrous specimens. The fibrous specimens showed significantly higher ultimate loads at β = 90° compared to β = 0°, indicating superior crack resistance and structural integrity under perpendicular loading conditions. The Brazilian disc specimens demonstrated variability in fracture toughness across different loading orientations, highlighting their suitability for mixed-mode fracture assessment.

Exploring Damage Patterns in CFRP Reinforcements: Insights from Simulation and Experimentation.

Carbon Fiber Reinforced Polymers (CFRP) have become increasingly significant in real-world applications due to their superior strength-to-weight ratio, corrosion resistance, and high stiffness. These properties make CFRP an ideal material for reinforcing concrete structures, particularly in scenarios where weight reduction is crucial, such as in bridges and high-rise buildings. The transformative potential of CFRP lies in its ability to enhance the durability and load-bearing capacity of concrete structures while minimizing maintenance costs and extending the lifespan of the infrastructure. This research explores the impact of reinforcing structural elements with advanced composite materials on the strength and durability of concrete and reinforced concrete structures. By integrating Carbon Fiber Reinforced Polymer (CFRP) reinforcements, we subjected both rectangular and T-section concrete beams to comprehensive three-point bending tests, revealing a substantial increase in flexural strength by 45% and crack resistance due to CFRP reinforcement. The study revealed that CFRP reinforcement increased the flexural strength of concrete beams by 45% and improved crack resistance significantly. Additionally, the load-bearing capacity of the beams was enhanced by 40% compared to unreinforced specimens. These improvements were validated through finite element simulations, which showed a close alignment with the experimental data. Furthermore, an innovative simulation study was conducted using a finely tuned finite element numerical model within the Abaqus calculation code. This model accurately replicated the laboratory specimens in terms of shape, dimensions, and loading conditions. The simulation results not only validated the experimental observations but also provided deeper insights into the stress distribution and failure mechanisms of the reinforced beams. Novel aspects of this study include the identification of specific failure patterns unique to CFRP-reinforced beams and the introduction of an enhanced interaction model that more accurately reflects the composite behavior under load. In CFRP-reinforced beams, specific failure patterns were identified, including flexural cracks in the tension zone and debonding of the CFRP sheets. These patterns indicate the points of maximum stress concentration and potential weaknesses in the reinforcement strategy. The study revealed that while CFRP significantly improves the overall strength and stiffness, careful attention must be given to the bonding process and the quality of the adhesive used to ensure optimal performance. These findings contribute significantly to the understanding of material interactions and structural performance, offering new pathways for the design and optimization of composite-reinforced concrete structures. This research underscores the transformative potential of composite materials in elevating the structural integrity and longevity of concrete infrastructures.

A finite difference method on crack resistance of reinforced glass beam with non-linear adhesive

Reinforced glass beam (RG beam) is a type of structural glass member that has been developed in recent years. This RG beam consists of a glass beam to which reinforcement material, such as steel, is adhesively attached in the tensile side to improve crack resistance. The adhesive plays a critical role in the structural performance of RG beam. However, the effect of non-linear shear-slip behavior of the adhesive layer remains unclear and has been neglected in most previous studies, which can result in inaccurate estimations. To address this issue, this paper presents a finite difference model (FDM) that utilizes an explicit step-by-step method and trial-and-error iterative method for interfacial stress analysis. The model predicts the static structural response of a simply-supported RG beam that simulates the adhesive with non-linear stress-slip behavior. Furthermore, the model describes the adherend’s shear deformation in elastic. The FDM results are then compared with the finite element method (FEM), adopting discrete nonlinear connectors (springs) to simulate the adhesion, and available analytical methods. Detailed parametric studies are further conducted to investigate the influences of glass strength, load pattern, reinforcement ratio and height-to-span ratio for proposing design recommendations.

Establishing Strategies to Improve Cracking Resistance of High Recycled Binder Ratio Asphalt Mixtures

This study aims to investigate promising mitigation strategies for improving the cracking performance of high recycled binder ratio (RBR) asphalt mixtures. Moisture-resistant aggregates that do not require anti-stripping agents, reclaimed asphalt pavement (RAP), and recycled asphalt shingles (RAS) were sampled for this study from sources in two climatic zones, south and north. The south-moisture-resistant (SR) mixtures were designed with 0.16 and 0.29 RBRs with RAP, while the north-moisture-resistant (NR) mixtures included 0.21 and 0.37 RBRs with RAP and 0.44 RBR with RAP/RAS. The mitigation strategies evaluated included a softer binder, a different binder source with higher ΔTc, a recycling agent (RA), reduced recycled binder availability (RBA), polymer-modified asphalt (PMA), and hybrid approaches including softer binder + RBA and PMA+RBA. The Indirect Tensile Asphalt Cracking Test (IDEAL-CT) and Disc-Shaped Compact Tension (DCT) test were conducted to capture intermediate-temperature and low-temperature cracking performance, respectively. In addition to the cracking tolerance index (CTindex), an IDEAL-CT interaction diagram analysis was added to further understanding the effect of mixture variables on cracking performance. The findings suggest that while no single strategy works for all RBR mixtures tested, RA, RBA, softer binder, or their combinations yield adequate cracking performance depending on factors including RAP binder stiffness and quantity, RA dose, climatic zone, and RBA.

Experimental Study of a Superabsorbent Polymer Hydrogel in an Alkali Environment and Its Effects on the Mechanical and Shrinkage Properties of Cement Mortars.

As internal curing self-healing agents in concrete repair, the basic properties of superabsorbent polymers (SAPs), such as water absorption and release properties, are generally affected by several factors, including temperature and humidity solution properties and SAP particle size, which regulate the curing effect and the durability of cementitious composites. This study aimed to investigate the water retention capacities of SAPs in an alkaline environment over extended periods by incorporating liquid sodium silicate (SS) into SAP-water mixtures and examining the influence of temperature. The influence of SAP particle size on mortar's water absorption capacity and mechanical behavior was investigated. Two mixing techniques for SAPs (dry and pre-wetting) were employed to assess the influence of SAP on cement mortars' slump, mechanical properties, and cracking resistance. Four types of SAPs (SAP-a, SAP-b, SAP-c, and SAP-d), based on the molecular chains and particle size, were mixed with SS to study their water absorption over 30 days. The results showed that SAPs exhibit rapid water absorption within the first 30 min, exceeding 85% before reaching a saturation point, and the chemical and temperature variations in the water significantly affected water absorption and desorption. The filtration results revealed that SAP-d exhibited the slowest water release rate, retaining water for considerably longer than the other three types of SAPs. The mechanical properties of SAP mortar were reduced due to the addition of an SAP and the improved cracking resistance of the cement mortars.

Evaluation of Cracking Resistance of SMA-13 Hot Recycling Asphalt Mixtures Reinforced by Basalt Fiber.

In the context of green and low-carbon development, energy saving, and emission reduction, hot recycling technology (RT) has been researched, which is divided into hot central plant RT and hot in-place RT. However, due to the aged asphalt binders, the shortcomings of hot recycled asphalt mixtures have become apparent, as in comparison to new asphalt mixtures, their resistance to cracking was inferior and the cracking resistance deteriorated more rapidly. Therefore, it was very necessary to focus on the improvement of crack resistance of hot recycled asphalt mixtures. Basalt fiber has been proved to be able to effectively improve the comprehensive road performance of new asphalt mixtures. Therefore, this paper introduced basalt fiber to hot central plant recycled and hot in-place recycled asphalt mixtures, in order to improve the crack resistance of asphalt as a new type of fiber stabilizer. Firstly, six types of SMA-13 fiber asphalt mixtures were designed and prepared, i.e., hot mixtures with basalt fiber or lignin fiber, hot central plant recycled mixtures with basalt fiber or lignin fiber, and hot in-place recycled mixtures with basalt fiber or lignin fiber. Secondly, the trabecular bending test, low-temperature creep test, semi-circular bending test, and IDEAL-CT were used to comparatively study the changing patterns of low and intermediate temperature cracking resistance of hot recycled mixtures with conventional lignin fibers or basalt fibers. Finally, Pearson's correlation coefficient was used to analyze the correlation of the different cracking resistance indicators. The results show that the low and intermediate temperature cracking resistance of hot central plant recycled mixtures increased by 45.6% (dissipative energy ratio, Wd/Ws) and 74.8% (flexibility index, FI), respectively. And the corresponding cracking resistance of hot in-place recycled mixture increased by 105.4% (Wd/Ws) and 55.7% (FI). The trabecular bending test was more suitable for testing the low-temperature cracking resistance of hot recycled asphalt mixtures, while the IDEAL-CT was more suitable for testing the intermediate-temperature cracking resistance. The results can provide useful references for the utilization of basalt fiber in the hot recycling of SMA-13 asphalt mixtures.

Emphasis of Cyclic Loading on the Fracture Mechanism and Residual Fracture Toughness of High-Performance Concrete Considering the Morphological Properties of Aggregate

This research investigates the fatigue behaviour and fracture mechanics of high-performance concrete (HPC), including various compositions such as HPC with basalt aggregates (HPC-B), HPC with gravel (HPC-G), and high-strength coarse mortar (CM) under static and cyclic tensile loading within the special priority program SPP 2020. The study aims to integrate fracture mechanics into structural analysis to enhance design guidelines for slender cross-sections and safety-related high-performance structural components. The experimental investigations reveal HPC-B’s remarkable superiority, displaying its higher compressive strength, modulus of elasticity, and tensile strength compared to HPC-G and CM. A modified disk-shaped compact tension (MDCT) based on ASTM standards, aided by digital image correlation (DIC) unveils fracture behaviour, emphasizing fracture energy as a crucial parameter. HPC-B exhibits improved crack resistance and notch sensitivity reduction attributed to crushed basalt aggregates and an enhanced interfacial transition zone (ITZ). The research scrutinizes factors like material characterization, aggregate morphology, stress levels, and the displacement rate on crack formation. High-cycle fatigue tests show HPC-B’s superior performance, and the post-fatigue analysis reveals enhanced residual fracture toughness attributed to nano-level structural changes, stress redistribution and aggregate-matrix interaction. A 3D image analysis via Computed Tomography (CT) scans captures mesostructural crack propagation and provide quantitative insights. This research marks a significant shift from conventional aggregate-focused approaches and introduces a novel approach by integrating excess paste theory and mesoscale analysis, highlighting the critical role of aggregate choice in material characterization and mesoscale design in enhancing the structural efficiency of HPC. Furthermore, the study advances the understanding of HPC fatigue behaviour, emphasizing the interplay of aggregate types and morphologies and their dynamic response to cyclic loading, offering valuable insights for optimizing design guidelines and fostering innovation in structural engineering.

STUDY OF LITERATURE REVIEW ON THE USE OF PLASTIC IN CONCRETE MIXES

Plastic waste poses significant environmental challenges due to its widespread use and long-lasting nature. In the search for sustainable construction solutions, this study presents a systematic review of international research spanning two decades on the integration of recycled plastics into concrete mixtures, either as aggregates or fibers. Applying strict inclusion and exclusion criteria, 97 of the 187 articles initially identified were analyzed in depth. Key findings indicate that the introduction of plastics can influence essential concrete properties such as density, compressive strength and thermal conductivity. The effectiveness of plastic integration largely depends on factors such as the type, size and shape of the plastic used. In particular, the research reveals that the use of plastic fibers can improve crack resistance, influenced by the size and type of fiber. Depending on the application, an optimal plastic replacement percentage is usually between 10% and 20%. This review highlights the potential of recycled plastics to increase the properties of concrete, offering an environmentally friendly route to reduce plastic waste and promote sustainable construction.

Combined Effect of Banana Fibre and Nano Silica on the Strength Properties of Concrete

Abstract: This study investigates the combined effect of nano silica and banana fibres on mechanical properties of concrete of grade M-25. Nano silica has been used as a partial replacement of cement by weight. Nano silica has been kept constant at 3% as maximum strength was achieved at this percentage according to past studies. Banana fibre has been added by weight of cement in proportions of 0.5%, 1%, 2%, 3%, 4% and 5%. Length of banana fibres kept at 40mm. Compressive strength was determined by using different combinations of nano silica and banana fibre. Nano concrete provides good strength as compared to conventional concrete. The addition of banana fibres in nano concrete improved the strength properties of nano concrete as well as improvement in crack resistance of concrete. On the other hand, the addition of banana fibres resulted in reduction workability as well as permeability of concrete

Promoting bridging in adhesively bonded composites with polymer inserts: A computational perspective

Preventing catastrophic failure due to delamination in adhesively bonded carbon fiber reinforced polymer (CFRP) is crucial to enhancing the reliability of structures. Experimental evidence from another study demonstrated that introducing inserts into the adhesive bond line creates bridging, effectively arresting the delamination process. In this paper, a numerical model was proposed to mimic the experiment and then utilized for conducting parametric studies. An embedded cell approach was adopted, representing a double cantilever beam (DCB) with linear-elastic continuum shell elements, beam elements for the bridging bundles, and connector elements for the adhesive. The crack propagation was initiated with adhesive failure and subsequently followed by bridging bundle failure. The numerical simulation results closely replicated the experiment’s global response in the force–displacement curve, thereby effectively validating the existence of the bridging effect. Furthermore, our study revealed that enhancing the adhesive strength and insert ductility can further improve crack resistance.

Experimental analysis of blended nanocomposites processed using compression molded microwave process

Microwave irradiation has emerged as a versatile and efficient method for synthesizing polymer nanocomposites, offering advantages such as selectivity, speed, and effectiveness in heating materials. This study explores the blending of low-density polyethylene (LDPE) and polypropylene (PP) with carbon nanotubes (CNTs) using microwave processing. The nanocomposites were characterized for their mechanical properties through tensile and fracture toughness tests. Results indicate that LDPE/CNT blended with PP/CNT pellets exhibited improved Young’s modulus and fracture toughness, while LDPE/CNT blended with PP/CNT powder showed enhanced stiffness and fracture toughness. The critical stress intensity factor ( KIC) increased with higher proportions of PP in both cases, signifying improved crack resistance. XRD and SEM analyses confirmed enhanced crystallinity and proper bonding between polymers and CNTs. Overall, this study demonstrates the potential of microwave processing in producing nanocomposites with enhanced mechanical properties, offering a promising avenue for engineering applications.

Mechanical Properties and Water Permeability of Textile-Reinforced Reactive Powder Concrete with Lightweight Aggregate.

This paper focuses on the development of thin-walled panels with specific properties for applications such as water-tight structures. The authors propose the use of textile-reinforced concrete (TRC) as a composite material and highlight its advantages, which include high tensile strength, improved crack resistance, and design flexibility. The study presents a novel approach which combines TRC with reactive powder concrete (RPC) as a matrix and a lightweight aggregate. RPC, known for its brittle behaviour, is reinforced with glass fibres and a textile fabric to increase its flexural strength. The research includes a comprehensive analysis of the physical and mechanical properties of both the unreinforced RPC matrix and the TRC composite. In particular, the lightweight aggregate RPC matrix has a porosity of 41%, and its mechanical properties, such as flexural and compressive strength, are discussed. The TRC composites, produced in thicknesses ranging from 1 mm to 4 mm, are subjected to flexural tests to evaluate their behaviour under load. The thicker elements show typical damage phases, while the thinner elements show greater flexibility and elasticity. SEM observations confirm good adhesion between the glass fibres and the RPC matrix. Water permeability tests show that the TRC composite, despite its highly porous structure, achieves a water permeability two orders of magnitude higher than that of a reference material, highlighting the roles of both the porous aggregate and the matrix hydration. The paper concludes with a proof of concept-a canoe called the PKanoe, which is constructed from the developed TRC composite. The design of the canoe is supported by numerical analysis to ensure its optimal shape and structural integrity under load. The research contributes to the exploration of innovative materials for sustainable civil engineering applications and addresses both structural and environmental considerations.

Dynamic Behaviors of Fiber-Reinforced Cellular Concrete Fabricated with Millimeter-Sized Superabsorbent Polymer

A novel cellular concrete with millimeter-level pores fabricated with superabsorbent polymers and fiber is introduced. Porous structure with reinforcement of fiber are adopted to improve crack resistance and shock-absorbing ability. To investigate the dynamic mechanical performance of fiber-reinforced cellular concrete, quasistatic compression and split Hopkinson pressure bar tests with strain rate from 15 to 90 s−1 were conducted. Three different fiber volume fractions (0.2%, 0.6%, and 1%), and two types of fibers (polypropylene fiber and basalt fiber (BF)) were adopted. Along with two levels of porosities (20% and 60%), total of 12 mix designs of cellular concrete to three-level axial impacting. The research results show that the novel cellular concrete is sensitive to high strain rates, demonstrating increasing dynamic compressive strength, dynamic elastic modulus, dynamic increase factor (DIF), and peak toughness with the increase in strain rate. In addition to the inertia effect, the locally enhanced porous structure and fiber structure can change the stress field and crack path, along with the energy consumption of deformation and cracks in the pores. The amount of fiber, physicochemical property, distribution, and shape amplify or dampen through its thickening effect, interface reaction, and stress transmission. Recommended fiber types and dosages were proposed to improve strength, stiffness, and toughness. BF showed an enhanced performance in terms of strength, modulus, and sharp strain-rate effect. Rules of DIFs were also studied. Awareness of the dynamic properties provides a foundation for proper design of structural members and increases the use of cellular concrete.

Crack behavior of expanded polystyrene foam-ceramsite composite thermal insulation mortar

To compensate for the deficiencies of thermal insulation, fire and crack resistances of traditional thermal insulation mortars, this paper prepares expanded polystyrene foam (EPSF)-ceramsites composite thermal insulation mortar (ECTIM) with ceramsite and EPSF particles as insulation aggregates. The effects of fiber content (i.e., P = 0.3%, 0.6%, 0.9%), fiber length (i.e., l = 3 mm, 6 mm, 9 mm) and fiber types (i.e., polypropylene fiber (PF), steel fiber (SF), alkali resistant glass fiber (ARGF)) on crack resistance of the ECTIM were analyzed. The test results demonstrated that the incorporation of fibers could significantly improve crack resistance and delay the cracking of mortar. With the increase of fiber content P, the water loss rate and cracking index decreased to 43.70% and 79.17% of the specimen without fiber. As the fiber length l increased from 0 mm to 9 mm, the water loss rate and cracking index decreased by 41.50% and 77.08%, respectively. Comparatively, the PF could obviously improve the crack resistance of the ECTIM. Based on the experimental research, the microscopic stress mechanism of mortar cracking, as well as the early and late anti-cracking mechanism of the ECTIM were revealed. In addition, considering the effects of fiber content and fiber length, a comprehensive influence coefficient ϖ was introduced, and a formula for conveniently calculating the maximum crack width Wmax of the ECTIM was proposed. The predicted results agreed well with the test data. The thermal insulation mortar prepared in this study could considerably overcome the deficiencies of traditional organic and inorganic thermal insulation mortars, and had excellent thermal insulation, fire and crack resistances. The resource utilization of iron tailings and the introduction of ceramsite reduced the materials cost. The prepared thermal insulation mortar could be used for wall substrate, geothermal heat insulation layer, external wall, internal wall and roof insulation.

Effects on different full-coverage designs and materials of crack propagation in first mandibular molar: an extended finite element method study.

Objectives: This study aims to investigate the biomechanical properties of fracture resistance in cracked teeth using five different full-coverage restorations made of three different materials. Materials and Methods: A 3D model of a mandibular first molar was created to design five different full-coverage repair models: crown, crown with composite resin filling inside, occlusal veneer, occlusal veneer with composite resin filling inside and onlay. These repair models were fabricated using three different materials, namely, zirconia, lithium disilicate (LDS), and a hybrid polymer-infiltrated ceramic network material (PIC). In total, 15 repair models were tested using the extended finite element method (XFEM), with an occlusal load of 5000N applied slowly to the occlusal surface of the restoration. The analysis of stress distribution in the restoration and dentin crack line was conducted to measure and record the crack initial load on the restoration and dentin. Results: The results showed that restorations on the occlusal surface significantly improved crack resistance, with zirconia exhibiting superior fracture resistance among the materials tested. Restorations of crown with composite resin filling inside demonstrated the highest resistance to fracture, while occlusal veneers showed the lowest. MPS concentration was observed at the interface between the restoration and dentin and at the root bifurcation, with the highest values at the top of crack development. Dentin covered by oxidized restorations had the highest displacement, while PIC restorations exhibited the lowest. Pulp analysis revealed selective MPS concentration and strain patterns in models with zirconia restorations and onlay, with pronounced pulp displacement in zirconia restorations and onlay. Enamel analysis indicated larger MPS values and displacements in zirconia restoration models and onlay, with higher strain in onlay. Restoration played a crucial role in protecting the tooth, with crack propagation initial loads in dentin surpassing restorations in experimental groups. Conclusion: This study confirms that full-coverage restorations significantly increased the fracture resistance of cracked teeth, with zirconia restorations significantly protecting the underlying cracked tooth. Elimination of fracture lines in the restoration design can improve fracture resistance in cracked teeth. The findings have implications for dental prosthetic design and clinical practice.

In-situ investigation of damage mechanisms in duplex AlCoCrFeNi2.1 high entropy alloy

The AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) is a promising casting system with high strength, and numerous studies investigating the effects of various thermomechanical processing routes. However, the ductility of this alloy – especially in its cast state – limits its practical applicability. In this paper, damage evolution and microstrain partitioning behaviour is presented along with bulk mechanical performance of the as-cast and hot rolled AlCoCrFeNi2.1 EHEA to provide experimental reasoning behind observed changes in ductility and strength. Tensile testing coupled with in-situ micro-digital image correlation (μ-DIC) and x-ray computed tomography (XCT) were used to determine the damage and fracture mechanisms. Microstrain analysis documents the effect of phase co-deformation and microstructure morphology on crack formation, and the role of damage evolution is supplemented with XCT. These results suggest methods to improve crack resistance in this alloy system and corroborate macroscopic mechanical property changes.