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In-situ consolidation of thermoplastic composites using Automated Fibre Placement (AFP) technology is an emerging manufacturing technique, offering tailored composite properties through customised processing parameters. Multiple competing parameters during AFP manufacturing influence the quality and mechanical performance of the laminates. These lay-up parameters are interrelated, and often require comprehensive experimental characterisation which is costly and time-intensive. This study aims to optimise the fracture toughness of in-situ consolidated thermoplastic composite (AS4/APC-2) and investigate the mechanisms that contribute to it. Taguchi's method is employed to efficiently analyse the effect of various process parameters at multiple levels. Based on the obtained results, a considerable effect of process parameters on Mode I and II fracture toughness is observed. The statistical analysis reveals that the Hot Gas Torch (HGT) temperature required for AFP processing significantly affects the Mode I fracture toughness, contributing to 33.8%. Whereas, the consolidation force, another key processing parameter in AFP notably affects Mode II fracture toughness, with the contribution of 81.8%. The analysis of variance (ANOVA) reveals interdependent processing parameter relations for both fracture modes. A validation test showed good agreement between the predicted fracture toughness and the experimental test. [ABSTRACT FROM AUTHOR]

Porosity is a critical microstructural factor in ceramic materials, influencing their mechanical and thermal properties. However, the detailed mechanisms through which porosity, grain size, and grain boundary fracture energy affect the thermal shock resistance of porous ceramics are still not fully understood. This study introduces a dual‐scale model that integrates these microstructural parameters to predict fracture toughness and thermal shock resistance. Using the single‐edge V‐notch fracture toughness testing principle, we calculate the thermal stress intensity factor and establish its relationship with temperature differentials. The critical temperature differential, which marks the onset of thermal shock damage, is determined when the thermal stress intensity factor reaches the fracture toughness threshold. The model reveals a significant interplay between porosity, grain size, and grain boundary fracture energy, with fine‐grained ceramics (grain size < 10 µm) showing a sharp decrease in fracture toughness as porosity increases, while coarser‐grained ceramics are less affected by porosity. These findings provide a deeper understanding of the microstructural optimization needed to enhance the thermal shock resistance of high‐performance porous ceramics. [ABSTRACT FROM AUTHOR]

The anisotropic fracture characteristics of oil shale are crucial in determining reservoir modification parameters and pyrolysis efficiency during in situ oil shale pyrolysis. Therefore, understanding the mechanisms through which temperature and bedding planes influence the fracture behavior of oil shale is vital for advancing the industrialization of in situ pyrolysis technology. In this study, scanning electron microscopy (SEM), CT scanning, and a real-time high-temperature rock fracture toughness testing system were utilized to investigate the spatiotemporal evolution of pores and fractures in oil shale across a temperature range of 20–600 °C, as well as the corresponding evolution of fracture behavior. The results revealed the following: (1) At ambient temperature, oil shale primarily contains inorganic pores and fractures, with sizes ranging from 50 to 140 nm. In the low-temperature range (20–200 °C), heating primarily causes the inward closure of inorganic pores and the expansion of inorganic fractures along bedding planes. In the medium-temperature range (200–400 °C), organic pores and fractures begin to form at around 300 °C, and after 400 °C, the number of organic fractures increases significantly, predominantly along bedding planes. In the high-temperature range (400–600 °C), the number, size, and connectivity of matrix pores and fractures increase markedly with rising temperature, and clay minerals exhibit adhesion, forming vesicle-like structures. (2) At room temperature, fracture toughness is highest in the Arrester direction (KIC-Arr), followed by the Divider direction (KIC-Div), and lowest in the Short-Transverse direction (KIC-Shor). As the temperature increases from 20 °C to 600 °C, both KIC-Arr and KIC-Div initially decrease before increasing, reaching their minimum values at 400 °C and 500 °C, respectively, while KIC-Shor decreases continuously as the temperature increases. (3) The energy required for prefabricated cracks to propagate to failure in all three directions reaches a minimum at 100 °C. Beyond 100 °C, the absorbed energy for crack propagation along the Divider and Short-Transverse directions continues to increase, whereas for cracks propagating in the Arrester direction, the absorbed energy exhibits a 'W-shaped' pattern, with troughs at 100 °C and 400 °C. These findings provide essential data for reservoir modification during in situ oil shale pyrolysis. [ABSTRACT FROM AUTHOR]

Fracture tests are a necessary means to obtain the fracture properties of concrete, which are crucial material parameters for the fracture analysis of concrete structures. This study aims to fill the gap of insufficient test results on the fracture toughness of widely used ordinary C40~C60 concrete. A three-point bending fracture test was conducted on 28 plain concrete and 6 reinforced concrete single-edge notched beam specimens with various depths of prefabricated notches. The results are reported, including the failure pattern, crack initiation load, peak load, and complete load versus crack mouth opening displacement curves. The cracking load showed significant variation due to differences in notch prefabrication and aggregate distribution, while the peak load decreased nonlinearly with an increase in the notch-to-height ratio. The reinforced concrete beams showed a significantly higher peak load than the plain concrete beams, attributed to the restraint of steel reinforcement, but the measured cracking load was comparable. A compliance versus notch-to-height ratio curve was derived for future applications, such as estimating crack length in crack growth rate tests. Finally, fracture toughness was determined based on the double-K fracture model and the boundary effect model. The average fracture toughness value for C50 concrete from this study was 2.0 M P a · m , slightly smaller than that of lower-strength concrete, indicating the strength and ductility dependency of concrete fracture toughness. The fracture toughness calculated from the two models is consistent, and both methods employ a closed-form solution and are practical to use. The derived fracture toughness was insensitive to the discrete parameters in the boundary effect model. The insights gained from this study significantly contribute to our understanding of the fracture toughness properties of ordinary structural concrete, highlighting its potential to shape future studies and applications in the field. [ABSTRACT FROM AUTHOR]

Acoustic emission (AE) evaluation is global NDT technique in which acoustic emissions takes place by loading the component at a specified threshold level. In this study, a crack propagation is studied by AE parameters.Specimens are tensile deformed and AE parameters are recorded. Three types of specimens, Type A, Type B and Type C, are designated as Heat affected zone, Parent metal and Weldment, respectively. The recorded data are analysed in three zones, Zone-1, Zone-2 and Zone-3, in terms of passive, active and critically active of a crack, respectively. Zone-1 is equivalent to the data arrangement up to 60% of Failure Load (FL), Zone-2 equates to 75% − 90% of F.L. and Zone-3 corresponds to fast-fracture region and equates to 90%-F.L. AE parameters – Amplitude, Ring down counts, Duration, Rise Time, Energy, RA Value, DA Value, Hit Rate, Count Rate and Energy Rate are tabulated for various failure loads. These parameters have vital importance in critical assessment of dynamic nature of cracks in Maraging steel. The scatter plots as qualitative indicators, and the rate graphs are used for understanding crack propagation. An abort criterion is developed by using combination of parameters that will serve as an early warning tool. [ABSTRACT FROM AUTHOR]

To repair a pipeline system, an automatic welding process is used to carry out the sleeve welding. In this study, the repair performance of the sleeve was studied, and the research results will help improve the repair quality of pipeline systems in the future. The results show that the tensile strength of the fillet weld was lower than the minimum nominal tensile strength of X65 steel. There were small cracks at the root of the fillet weld. The fracture surfaces of the side bend test of the butt weld and the notching hammer break test of the fillet weld indicated defects to different degrees. The tensile tests of butt welds indicated breaks in the base metal, and the average tensile strength was 587 MPa. The ductile-brittle transition temperature of the butt weld and the fusion line ware both lower than −60°C , and the average crack tip opening displacement (CTOD) values of −10°C fracture toughness tests of the butt weld and heat affected zone were 0.181 and 0.510 mm, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Geology & Recovery Efficiency is the property of Petroleum Geology & Recovery Efficiency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights An interlaminar ultrafine spraying method was proposed for monolayer graphene oxide (GO) modified CFRP nanocomposite laminates. The well‐dispersed monolayer GO nano‐solutions were prepared by multi‐level dispersion and then sprayed on carbon fiber/epoxy prepreg by the ultrafine atomizing technique. A series of GO/CFRP laminate specimens with different GO loadings were fabricated for our fracture toughness tests and SEM characterization. The test results indicated that the Mode I fracture toughness (GIC$$ {G}_{\mathrm{IC}} $$) was enhanced by 140% with quite a low fraction of monolayer GO nanosheets. The distinct toughening effect at such a low level of nano‐contents was attributed to the sufficient quantity of monolayer GO nanosheets and also a uniform distribution, which was found to be more important than the volume/weight fraction as the principal structural parameter. Thus, the proposed interlaminar toughening approach owns the virtues of good effectiveness and especially low cost owing to the largely reduced weight percentage of nanographene, showing a promising potential of industrial scale‐up. Proposed an interlaminar ultrafine spraying method for monolayer GO nanosheets. Found that the quantity of GO nanosheets is vital in polymer toughening. Realized significant toughening with extremely low loadings of monolayer GO. Provided a way with high toughening effect and low cost for industrial scale‐up. [ABSTRACT FROM AUTHOR]

Featured Application: The strength and rigidity of the durable resin make it ideal for a wide range of applications, including prototyping and product development, automotive and aerospace components, medical devices, consumer goods, custom tooling, and educational models. Its strength and precision are precious in producing functional prototypes, nonstructural automotive parts, custom medical devices, and durable electronic enclosures. This versatile material speeds up design processes and improves the durability and functionality of end products in various industries. This study presents the results of fracture toughness tests conducted on specimens obtained by additive manufacturing techniques, specifically using low-force stereolithography. The samples were manufactured from a transparent 3D printing material for biocompatible applications, the so-called BioMed Durable Resin, which is a Formlabs-patented polymer material that simulates the strength and rigidity of polyethylene. The selected toughness tests in this context were performed following the ASTM D5045-99 guidelines. All tests were conducted under controlled laboratory conditions at 23 °C and 50% relative humidity, ensuring adherence to the standard and the replicability of the experimental results. To investigate the influence of printing plane orientation, specimens were produced at three printing orientation angles (0, 45, and 90 degrees). These angles were selected to provide a comprehensive evaluation of the anisotropy effects in the material. They cover both extreme orientations (0° and 90°) and include an intermediate value (45°), allowing us to assess variations in mechanical behavior across a representative range of printing orientations, consistent with prior research in the field. The experimental tests yielded data on the crack resistance and energy release rate for each angle of orientation. There are various implications of the findings, beyond materials engineering, for applications in biomedicine. Indeed, this same approach opens the door to new research methods for manufacturing certified biocompatible materials from such durable resins. Finally, complementary issues such as related medical applications have been slightly addressed for future work, since biomedicine innovation clusters can contribute to accelerating growth in this crucial field for productive sector activity and the local business environment. [ABSTRACT FROM AUTHOR]

Recently, a new promising type of marine shale gas reservoir, carbonate-rich shale, has been discovered. But the mechanical properties of this type of shale were still unrevealed and the corresponding reservoir stimulation designwas lack of guidance. Using the deep downhole cores of an exploratory carbonate-rich shale gas well, the physical and mechanical parameters and failure mechanism of the whole reservoir section were acquired and evaluated systematically, by performing XRD, tri-axial compression, Brazilian splitting, and fracture toughness tests. A new model was established to evaluate the reservoir brittleness based on fracture morphology and stress-strain curve. Recommended strategy for reservoir stimulation was discussed. Results showed that (1) Carbonate-rich shale possessed high compressive strength and high Young's modulus, which were improved by 10.74% and 3.37% compared to that of siliceous shale. It featured high tensile strength and fracture toughness, with insignificant anisotropy. (2) With the content of carbonate minerals increasing, the shear failure morphology transformed from sparse and wide brittle fractures to diffusely distributed and subtle plastic cracks. (3) The brittleness index order was: siliceous shale, clay-rich shale, carbonate-rich shale, and limestone. (4) The special properties of carbonate-rich shale were rooted in the inherent feature of carbonate minerals (high strength, high elastic modulus, and cleavage structure), resulting in greater challenge in reservoirs stimulation. The above findings would promote the understanding of carbonate-rich shale reservoirs and provide reference for the optimum design of reservoir stimulation. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing technologies provide new opportunities for manufacturing complex components. However, the limited data on fracture behavior are delaying adoption in safe‐critical applications. This paper aims to evaluate the effect of orientation and the intra‐build design parameters on EBM Ti6Al4V fracture toughness using a design of experiments. Three builds comprised of over 150 compact tension samples were printed representative of the EBM build chamber, followed by microstructural characterization, X‐ray microcomputed tomography, and fracture toughness testing per ASTM E399. The average fracture toughness was 65 MPa√m, with anisotropy as the largest source of variation due to crack growth behavior with respect to the build direction. Microstructure coarsening was observed with increase in height, resulting in an increase in fracture toughness, irrespective of sample geometry or orientation. Build orientation and sample location influenced the microstructure and fracture toughness and should be considered when adopting EBM components in load‐bearing applications. Highlights: The effect of intra‐build parameters on EBM Ti6Al4V fracture toughness is investigated.The fracture toughness reported 10% variation, comparable to cast and wrought alloys.Response surface methodology helped identify factors effecting fracture toughness.Anisotropy was the biggest source of variation, affected by build orientation. [ABSTRACT FROM AUTHOR]

This research work aims to compare the strength and fracture mechanics properties of plain concretes, obtained from different coarse aggregates. During the study, mechanical parameters including compressive strength (fcm) and splitting tensile strength (fctm), as well as fracture parameters involving critical stress intensity factor (K I c S) and critical crack tip opening displacement (CTODc) were evaluated. The effect of the aggregates used on the brittleness of the concretes was also analyzed. For better understanding of the crack initiation and propagation in concretes with different coarse aggregates, a macroscopic failure surfaces examination of the tested beams is also presented. Crushed aggregates covered were basalt (BA), granite (GT), and limestone (LM), and natural peeble gravel aggregate (GL) were used in the concrete mixtures. Fracture toughness tests were performed on an MTS 810 testing machine. Due to the high strength of the rock material, the rough surface of the aggregate grains, and good bonding in the ITZ area between the aggregate and the paste, the concretes with crushed aggregates exhibited high fracture toughness. Both of the analyzed fracture mechanics parameters, i.e.,   K I c S and CTODc, increased significantly in the case of concretes which were manufactured with crushed aggregates. They amounted, in comparison to concrete based on gravel aggregate, to levels ranging from 20% for concrete with limestone aggregate to over 30% for concrete with a granite aggregate, and to as much as over 70% for concrete with basalt aggregate. On the other hand, the concrete with gravel aggregate showed the lowest fracture toughness because of the smooth surface of the aggregate grains and poor bonding between the aggregate and the cement paste. However, the fracture process in each series of concrete was quasi-plastic in the case of gravel concrete, semi-brittle in the case of limestone concrete, and clearly brittle in the case of the concretes based on granite and basalt aggregates. The results obtained help to explain how the coarse aggregate type affects the strength parameters and fracture toughness at bending. [ABSTRACT FROM AUTHOR]

This study presents test results and deep discussion regarding measurements of the fracture toughness of new concrete composites based on ternary blended cements (TCs). A composition of the most commonly used mineral additive (i.e., fly ash (FA)) in combination with nano-silica (NS) has been proposed as a partial replacement of the ordinary Portland cement (OPC) binder. The novelty of this article is related to the fact that ordinary concretes with FA + NS additives are most often used in construction practice, and there is a decided lack of fracture toughness test results concerning these materials. Therefore, in order to fill this gap in the literature, an extensive evaluation of the fracture mechanic parameters of TC was carried out. Four series of concretes were created, one of which was the reference concrete (REF), and the remaining three were TCs. The effect of a constant content of 5% NS and various FA contents, such as 0, 15%, and 25% wt., as a partial replacement of cement was studied. The parameters of the linear and nonlinear fracture mechanics were analyzed in this study (i.e., the critical stress intensity factor ( K I c S ), critical crack tip opening displacement (CTODc), and critical unit work of failure (JIc)). In addition, the main mechanical parameters (i.e., the compressive strength (fcm) and splitting tensile strength (fctm)) were evaluated. Based on the studies, it was found that the addition of 5% NS without FA increased the strength and fracture parameters of the concrete by approximately 20%. On the other hand, supplementing the composition of the binder with 5% NS in combination with the 15% FA additive caused an increase in all mechanical parameters by approximately another 20%. However, an increase in the FA content in the concrete mix of another 10% caused a smaller increase in all analyzed factors (i.e., by approximately 10%) compared with a composite with the addition of the NS modifier only. In addition, from an ecological point of view, by utilizing fine waste FA particles combined with extremely fine particles of NS to produce ordinary concretes, the demand for OPC can be reduced, thereby lowering CO2 emissions. Hence, the findings of this research hold practical importance for the future application of such materials in the development of green concretes. [ABSTRACT FROM AUTHOR]

Obesity and type 2 diabetes (T2D) are risk factors for fragility fractures. It is unknown whether this elevated risk is due to a diet favoring obesity or the diabetes that often occurs with obesity. Therefore, we hypothesized that the fracture resistance of bone is lower in mice fed with a high fat diet (45% kcal; HFD) than in mice that fed on a similar, control diet (10% kcal; LFD), regardless of whether the mice developed overt T2D. Sixteen-week-old, male NON/ShiLtJ mice (resistant to T2D) and age-matched, male NONcNZO10/LtJ (prone to T2D) received a control LFD or HFD for 21 weeks. HFD increased the bodyweight to a greater extent in the ShiLtJ mice compared to the NZO10 mice, while blood glucose levels were significantly higher in NZO10 than in ShiLtJ mice. As such, the glycated hemoglobin A1c (HbA1c) levels exceeded 10% in NZO10 mice, but it remained below 6% in ShiLtJ mice. Diet did not affect HbA1c. HFD lowered trabecular number and bone volume fraction of the distal femur metaphysis (micro-computed tomography or μCT) in both strains. For the femur mid-diaphysis, HFD significantly reduced the yield moment (mechanical testing by three-point bending) in both strains but did not affect cross-sectional bone area, cortical thickness, nor cortical tissue mineral density (μCT). Furthermore, the effect of diet on yield moment was independent of the structural resistance of the femur mid-diaphysis suggesting a negative effect of HFD on characteristics of the bone matrix. However, neither Raman spectroscopy nor assays of advanced glycation end-products identified how HFD affected the matrix. HFD also lowered the resistance of cortical bone to crack growth in only the diabetic NZO10 mice (fracture toughness testing of other femur), while HFD reduced the ultimate force of the L6 vertebra in both strains (compression testing). In conclusion, the HFD-related decrease in bone strength can occur in mice resistant and prone to diabetes indicating that a diet high in fat deleteriously affects bone without necessarily causing hyperglycemia. [ABSTRACT FROM AUTHOR]

In this study, a new method for welding an API 5L X65 steel pipe that is internally clad with Alloy 625 cladding using Alloy 22 and AWS ER100S-G steel was developed. The first and second weld passes were made using Alloy 22 to provide excellent corrosion resistance for the Alloy 625 cladding region. The remaining weld passes were made using 100S-G steel to provide high mechanical strength. The welded joints were evaluated for their microstructure and mechanical properties. No significant solidification defects were found in the welded joints, as confirmed by bending and transverse tensile tests. The yield strength of the welded joint showed that welding was capable of delivering the necessary strength compatible with API 5L X65, X70, and X80 steels for subsequent installation using the reel lay process. The microstructure of the welded joint was complex, with the first two weld passes having a soft Ni-fcc matrix composed mainly of Alloy 22, while the first three 100S-G steel weld passes had a hard martensite matrix. The main region of the welded joint had a soft acicular ferritic matrix. Impact toughness testing showed that the energy absorbed by the notch positioned at the first steel weld pass was better than that for the notch positioned at the steel weld pass without a dilution effect for Alloy 22 (approximately 46 J and 14 J, respectively). The toughness of the weld pass increased due to the high Ni incorporation by dilution with Alloy 22, even at − 15 °C, while the steel weld passes that were not affected by dilution with Alloy 22 exhibited very low energy absorption, which is characteristic of steel materials assessed under conditions below the ductile-to-brittle transition temperature (DBTT). The fracture toughness tests confirmed this result, as the major steel weld passes exhibited brittle features that caused abrupt failure during the test at − 15 °C. [ABSTRACT FROM AUTHOR]

The composite blade is integral to megawatt-class wind turbines and frequently incurs interlaminar damages such as adhesive failures, cracks, and fractures, which may originate from manufacturing flaws or sustained external fatigue loads. Notably, adhesive joint failure in the spar–web and trailing edge (TE) represents a predominant damage mode. This study systematically explores the failure mechanism in these regions, using mode I fracture toughness tests for an in-depth, quantitative analysis of the adhesive joint's fatigue crack growth characteristics. Additionally, we conducted extensive material and technical evaluations on specimen units, aiming to validate the reliability of techniques employed for wind blade damage modeling. A damage model, inspired by the NREL 5 MW wind generator's composite blade structure, meticulously considers the interactions between the TE and spar–web. Utilizing the virtual crack closure technique (VCCT), this model effectively simulates crack growth dynamics in wind blade adhesive joints, while the extended finite element method (XFEM) aids in analyzing crack propagation trajectories under repetitive fatigue loading. By applying this integrated methodology, we successfully determined the lifespan of the spar–web adhesive joint under constant load amplitudes, providing crucial insights into the resilience and longevity of critical wind turbine components. [ABSTRACT FROM AUTHOR]

Aluminium alloys are used for the fabrication of the fuel clad of research-grade nuclear reactors as well as for several types of core components of high-flux research reactors. In order to carry out design and safety analysis of these components, their mechanical and fracture properties are required by the designer. In this work, experiments have been conducted on tensile specimens machined from an aluminium alloy block to evaluate the material stress-strain curve. Experiments have also been conducted on disc-shaped compact tension specimens in order to determine the fracture toughness of aluminium alloy. Numerical simulations of both tensile and fracture specimens have been carried out using the crystal plasticity model. Initially, the slip system level parameters of the crystal plasticity material model have been calibrated using experimental stress-strain data for single as well as polycrystalline aluminium. For the prediction of crack initiation toughness, Rice and Tracey's damage model has been used. The critical damage parameter has been evaluated for a fractured specimen with a crack length-to-width (a/W) ratio of 0.6. The attainment of the critical damage parameter in the analysis corresponds to the instance of experimentally observed ductile crack initiation in the specimen. Later, this model was applied to other fracture specimens with different a/W ratios with values ranging from 0.39 to 0.59. It was observed that the critical damage parameter corresponding to crack initiation in the material has a very small variation, even if the specimens have different crack lengths. It is well-known in the literature that Rice and Tracey's critical damage parameter is a material constant. Hence, we have applied the same model to predict crack initiation for single crystal fracture specimens with two different orientations of the crack plane. It was observed that the <111> orientation is more susceptible to crack initiation and propagation compared with the <100> orientation, as the damage parameter is high in the ligament of the specimen ahead of the crack tip for the same level of applied loading. As the [111] crack plane is more closely packed compared with the [100] plane, the distance between atomic planes is greater for the former, and hence, it is more susceptible to ductile damage. The results of the experiments and the material damage parameter are helpful for the integrity analysis of the fuel clad of research reactors as well as components of high-flux research reactors. [ABSTRACT FROM AUTHOR]

In this paper, we describe the mechanical characteristics of Al2O3 and TiCN thin films formed by chemical vapor deposition (CVD) and a TiAlN thin film formed by physical vapor deposition (PVD), which are used as hard coating films. A focused ion beam (FIB) was used to fabricate a microcantilever beam for strength tests and fracture toughness tests under bending. A nanoindentation system was used to apply normal force to cantilever beams. All the films showed a linear force–deflection relationship, indicating brittle fracture during elastic deformation. The Young’s modulus ranged from 340 to 379 GPa, with no significant difference among the films, whereas the fracture strength of the Al2O3 films was 5.5 GPa, which was almost twice those of the other two films. For the fracture toughness test, a precrack with various depths was made using FIB at 2 μm from the fixed end of the cantilever beam. The Al2O3 film toughness values ranged from 4.1 to 5.5 MPa√m, which were almost twice that of the TiCN film at each precrack depth. Both CVD films showed a similar trend, i.e., an increase in fracture toughness with decreasing precrack depth, However, the fracture toughness of the TiAlN film showed no precrack depth dependence. The difference in fracture toughness between the CVD and PVD films is discussed on the basis of fracture surface observation results and information on the crystal grain size and orientation. [ABSTRACT FROM AUTHOR]

The mechanical testing of additively manufactured parts has largely relied on the existing standards developed for traditional manufacturing. While this approach leverages the investment made in current standards development, it inaccurately assumes that the mechanical response of additive manufacturing (AM) parts is identical to that of parts manufactured through traditional processes. When considering thermoplastic, material extrusion AM, the differences in response can be attributed to an AM part's inherent inhomogeneity caused by porosity, interlayer zones, and surface texture. Additionally, the interlayer bonding of parts printed with large-scale AM is difficult to adequately assess, as much testing is performed such that stress is distributed across many layer interfaces; therefore, the lack of AM-specific standards to assess interlayer bonding is a significant research gap. To quantify interlayer bonding via fracture toughness, double cantilever beam (DCB) testing has been used for some AM materials, and DCB has been generally used for a variety of materials including metal, wood, and laminates. Mode I DCB testing was performed on thermoplastic matrix composites printed with Big Area Additive Manufacturing (BAAM). Of particular interest was the notch shape and deflection speed during testing. The results examine the differences when using two notch types and three deflection speeds. The testing method introduced by the following paper differentiates itself from the ones described in the standards used by modernizing the methodology. This was conducted with the introduction of Digital Image Correlation (DIC) to gather displacement and load data simultaneously without human intervention. [ABSTRACT FROM AUTHOR]

Featured Application: Our research is the second step toward both establishing a standard aging protocol as well as selecting methods useful for evaluating the degradation of dental materials. The durability and performance of dental composites are essential for ensuring long-lasting dental restorations. However, there is a lack of a standardized procedure for evaluating the lifespan of dental materials. Our proposal assumed that dental materials should be tested under aggressive aging conditions to accelerate materials' degradation in vitro and such an approach should simulate prolonged material usage in the oral cavity. A comprehensive examination of the impacts of three aging methodologies on various mechanical properties, including the flexural strength (FS), diametral tensile strength (DTS), hardness (HV), fracture toughness (FT), flexural fatigue limit (FFL), and microstructure of selected dental materials (Resin F, Flow-Art and Arkon), was conducted. The findings revealed that preformed aging results in an average reduction of 30% in the mechanical strength properties of the dental composites when compared to the control. Notably, a strong correlation was identified between FS and FFL post-aging whereas no such relationship was observed between these parameters and FT. This paper highlights the significance of aging tests for new dental composites and recommends a focus on flexural strength and fracture toughness to optimize costs and time efficiency. Furthermore, the establishment of a standardized test for fracture toughness in dental composites is recommended. It is proposed that a minimum flexural strength of more than 32–48 MPa after aging should be maintained. A more extensive analysis of commercially available materials is suggested to refine the proper evaluation methods for composite materials. [ABSTRACT FROM AUTHOR]

Purpose: Composite materials have revolutionized the aerospace industry by offering superior structural qualities over traditional elements. This study aims to focus on the development and testing of bamboo natural fiber-based composites enhanced with SiO2 nanoparticles. Design/methodology/approach: The investigation involved fabricating specimens with varying nanoparticle compositions (0, 10 and 20%) and conducting tensile, flexural, impact and fracture toughness tests. Results indicated significant improvements in mechanical properties with the addition of nanoparticles, particularly at a 10% composition level. Findings: This study underscores the potential of natural fiber composites, highlighting their environmental friendliness, cost-effectiveness and improved structural properties when reinforced with nanoparticles. The findings suggest an optimal ratio for nanoparticle integration, emphasizing the critical role of precise mixing proportions in achieving superior composite performance. Originality/value: The tensile strength, flexural strength, impact resistance and fracture toughness exhibited notable enhancements compared with the 0 and 20% nanoparticle compositions. The 10% composition showed the most promising outcomes, showcasing increased strength across all parameters. [ABSTRACT FROM AUTHOR]

Copyright of Diamond & Abrasives Engineering is the property of Zhengzhou Research Institute for Abrasives & Grinding and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This experimental research aims to produce and study the properties of MoSi 2 reinforced with CNT composites using the SPS sintering method. First and before any laboratory operations, using the Minitab 14 software, experimental samples were designed under L16 arrays. Four levels were set for defining parameters, such as the amount of reinforcing phase (CNT), sintering temperature (°C), and holding time (T). XRD, FESEM, density, micro-hardness, bending strength, and fracture toughness tests were used in the study for in-depth investigations. According to the signal-to-noise analysis, the parameter with the greatest influence is the reinforcement rate. Based on the obtained results, the composite with 5 wt% of carbon nanotubes, a sintering temperature of 1300 °C, and a holding time of 10 min was found to have the highest results. [ABSTRACT FROM AUTHOR]

Fracture toughness, which is the resistance of a material to crack propagation, is a critical material property for ensuring the mechanical reliability of damage‐tolerant design. Recently, damage‐tolerant design is introduced to flexible electronics by adopting micro‐cracked ultra‐thin nanocrystalline (NC) gold films as stretchable electrodes in a plane stress state. However, experimental investigation of the plane stress fracture toughness of those films remains challenging due to the intrinsic fragility from their sub‐100 nm thicknesses. Here, a quantitative method for systematically evaluating the plane stress fracture toughness of freestanding ultra‐thin NC gold film on water surface platform is presented. After effectively fabricating single‐edge‐notched‐tension samples with femtosecond laser, mode I stress intensity factors are measured in the plane stress state on water surface. Moreover, investigation regarding the effect of notch length, notch sharpness, and notch tip plasticity validates this method based on linear elastic fracture mechanics theory. As a demonstration, the thickness‐dependent plane stress fracture toughness of ultra‐thin NC gold films is qualitatively unveiled. It is revealed that the thickness confinement effect on grain boundary sliding induces a transition in fracture behavior. This method is expected to further clarify the fracture‐related properties of various ultra‐thin films for next‐generation electronics. [ABSTRACT FROM AUTHOR]

The aim of the current study was to determine the fracture toughness of different zones in carburized Pyrowear 53 steel using the small punch test (SPT) method. Firstly, Pyrowear 53 steel was quenched and tempered using different processing parameters to obtain core materials with varied microstructures and fracture toughness. The results obtained for the core material in standard fracture toughness tests were then compared with the SPT results, which allowed the determination of a formula correlating the fracture energy integral, JSPT, from the SPT with JQ integrals obtained from standardized compact tension specimens. In the next stage, Pyrowear 53 steel was carburized at 925 °C and divided into the following zones: (1) a carburized layer (up to 0.5 mm from the surface), (2) a transition layer (from 0.5 to 1.5 mm), and (3) a core zone (more than 1.5 mm). Each zone was characterized in terms of its microstructure and tensile properties using miniaturized test specimens. Finally, the fracture toughness values of the core zone (JSPT = 78–102 kJ/m2), the transition layer (JSPT = 71–80 kJ/m2), and the carburized layer (JSPT = 8.1–9.1 kJ/m2) were determined based on the obtained SPT results. It was shown that the use of such a relatively simple SPT method with the proposed energy-based approach seems to be a promising way of determining the fracture toughness of thin layers or local changes in the fracture behavior of surface-treated materials. [ABSTRACT FROM AUTHOR]

A large number of construction practice projects have found that there are many joints and microcracks in rock, concrete, and other structures, which cause the complexity of rock mechanical properties and are the main cause of geological or engineering disasters such as earthquakes, landslides, and rock bursts. To establish a rock fracture toughness evaluation method and understand the distribution range of fracture toughness of Longmaxi Formation shale, this study prepared three-point bending semi-circular disk shale samples of Longmaxi Formation with different crack inclination angles. The dimensionless fracture parameters of the samples, including the dimensionless stress intensity factors of type I, type II, and T-stress, were calibrated using the finite element method. Then, the peak load of the samples was tested using quasi-static loading, and the load–displacement curve characteristics of Longmaxi Formation shale and the variation in fracture toughness with crack inclination angle were analyzed. The study concluded that the specimens exhibited significant brittle failure characteristics and that the stress intensity factor is not the sole parameter controlling crack propagation in rock materials. With an increase in crack inclination angle, the prefabricated crack propagation gradually transitions from being dominated by type I fracture to type II fracture, and the T-stress changes from negative to positive, gradually increasing its influence on the fracture. An excessively large relative crack length increases the error in fracture toughness test results. Therefore, this paper suggests that the relative crack length a/R should be between 0.2 and 0.6. The fracture load distribution range of shale samples with different crack angles is 3.27 kN to 10.92 kN. As the crack inclination angle increases, the maximum load that the semi-circular disk shale samples can bear gradually increases. The pure type I fracture toughness of Longmaxi Formation shale is 1.13–1.38 MPa·m1/2, the pure type II fracture toughness is 0.55–0.62 MPa·m1/2, and the T-stress variation range of shale samples with different inclination angles is −0.49–9.48 MPa. [ABSTRACT FROM AUTHOR]

(1) Modeling and characterization of ductile fracture in metals is still a challenging task in the field of computational mechanics. Experimental testing offers specific responses in the form of crack-mouth (CMOD) and crack-tip (CTOD) opening displacement related to applied force or crack growth. The main aim of this paper is to develop a phase-field-based Finite Element Method (FEM) implementation for modeling of ductile fracture in stainless steel. (2) A Phase-Field Damage Model (PFDM) was coupled with von Mises plasticity and a work-densities-based criterion was employed, with a threshold to propose a new relationship between critical fracture energy and critical total strain value. In addition, the threshold value of potential internal energy—which controls damage evolution—is defined from the critical fracture energy. (3) The material properties of AISI 316L steel are determined by a uniaxial tensile test and the Compact Tension (CT) specimen crack growth test. The PFDM model is validated against the experimental results obtained in the fracture toughness characterization test, with the simulation results being within 8% of the experimental measurements. (4) The novel implementation offers the possibility for better control of the ductile behavior of metallic materials and damage initiation, evolution, and propagation. [ABSTRACT FROM AUTHOR]

In this work, graphene powder-reinforced Ti-Al metal-intermetallic laminated composite (GPEP-Ti/Al MIL composite) was designed and fabricated using the hot rolling and the vacuum hot-pressing sintering with the materials of graphene powder, titanium foil (TA1), and aluminum foil (1060 Al). The microstructure characterization of the composite was performed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffractometer (XRD), and the transmission electron microscopy (TEM). The results showed that single-phase Al3Ti was formed at the interface between Ti layer and Al layer. And the graphene powder and pure Al can be bonded well during the preparation process. In addition, the mechanical properties of the tensile, compressive, three-point bending, and fracture toughness tests indicated that the GPEP-Ti/Al MIL composite exhibits enhanced strength and superior plasticity. Ductile fracture predominates in Ti layer and Al layer, while the interface between them shows obvious brittle fracture. [ABSTRACT FROM AUTHOR]

This study demonstrates that bond strength can be enhanced by injecting excess electrons or holes into a material by electron beam irradiation. To determine the effect of excess electrons/holes on the interatomic bond strength, fracture toughness tests were performed on single-crystal Si micropillars under various electron-beam irradiation conditions. The fracture toughness under electron beam irradiation was 4%–11% higher than that under non-irradiated conditions. In particular, an increase in strength was large in tests performed under hole-injection conditions. Furthermore, in first-principles calculations of the tensile strength of excess electrons/hole-doped Si, the ideal tensile strength monotonically decreased with an injection in excess electrons and increased monotonically with the injection of holes. This is qualitatively consistent with the experimental result that the fracture toughness increases under hole-injection conditions. [ABSTRACT FROM AUTHOR]

To investigate the effects of nano-SiO2 (NS) and polyvinyl alcohol (PVA) fibers on the durability and mechanical properties of cementitious composites subjected to saline freeze–thaw cycling, a series of PVA fiber-reinforced cementitious composite (PFRCC) specimens were prepared using various fiber contents, and a series of NS and PVA fiber-reinforced cementitious composite (NPFRCC) specimens were prepared using various combinations of NS and fiber contents. Durability and fracture toughness tests were subsequently conducted on the specimens after different numbers of saline freeze–thaw cycles. The results indicate that the degradation of material properties can be divided into slow and accelerated damage stages before/after 50 freeze–thaw cycles. The durability and fracture toughness of the specimen series tended to increase, then decrease with increasing NS and PVA contents, suggesting optimum levels. When the PVA fiber content was 0.5%, PFRCC specimens had the best durability after saline freeze–thaw cycles; when the NS and PVA fiber contents were 1.0% and 0.5%, respectively, NPFRCC specimens had the best durability and fracture properties, and the initiation toughness, destabilization toughness, and fracture energy after 100 saline freeze–thaw cycles were 120.69%, 160.02%, and 451.31%, respectively. The results of this study may guide future exploration of the durability and mechanical properties of concrete subjected to freeze–thaw action. [ABSTRACT FROM AUTHOR]

Fiber-reinforced cement composites, particularly those incorporating natural fibers like cellulose, have gained attention for their potential towards more sustainable construction. However, natural fibers present inherent deficiencies in mechanical properties and can benefit from hybridization with carbon fibers. This study focuses on the incorporation of cellulose and carbon fibers, in varying contents, into fibrocement composites, employing a Response Surface Methodology (RSM) to optimize the material characteristics. The methodology involves testing, encompassing flexural tensile, compression, and fracture toughness tests. The results indicate an increasing trend in flexural strength for higher carbon fiber content, peaking near 5%. A plateau in flexural strength is observed between 1.2% and 3.6% carbon fiber content, suggesting a range where mechanical properties stabilize. Compressive strength shows a plateau between 1.2 and 3.6% and reaches its highest value (≈33 MPa) at a carbon fiber content greater than 4.8%, and fracture toughness above 320 MPa·m1/2 is achieved with carbon fiber content above 3.6%. This study offers insights into optimizing the synergistic effects of cellulose and carbon fibers in fibrocement composites. [ABSTRACT FROM AUTHOR]

This paper examines the impact of a multilayered gradient coating, applied via plasma-activated chemical vapor deposition (PACVD), on the structural and mechanical attributes of nanostructured WC-Co cemented carbides. WC-Co samples containing 5 and 15 wt.% Co were synthesized through a hot isostatic pressing (HIP) process using nanoparticle powders and coated with two distinct multilayer coatings: titanium nitride (TiN) and titanium carbonitride (TiCN). Nanosized grain formation without microstructural defects of the substrates, prior to coating, was confirmed by magnetic saturation and coercivity testing, microstructural analysis, and field emission scanning electron microscope (FESEM). Nanoindentation, fracture toughness and hardness testing were conducted for uncoated samples. After coatings deposition, characterizations including microscopy, surface roughness determination, adhesion testing, coating thickness measurement, and microhardness examination were conducted. The impact of deposited coatings on wear resistance of produced hardmetals was analyzed via scratch test and dry sliding wear test. Samples with higher Co content exhibited improved adhesion, facilitating surface cleaning and activation before coating. TiN and TiCN coatings demonstrated similar roughness on substrates of identical composition, suggesting Co content's minimal influence on layer growth. Results of the mechanical tests showed higher microhardness, higher elastic modulus, better adhesion, and overall superior tribological properties of the TiCN coating. [ABSTRACT FROM AUTHOR]

PyC/BN multiphase interfacial phases were prepared on the surface of SiC fiber preform, then the near stoichiometric ratio SiC fiber reinforced SiC ceramic matrix composites were obtained by polymer impregnation and pyrolysis (PIP) process. The mechanical behavior of SiC/SiC composites was characterized by three‐point bending tests and fracture toughness tests. The stress release and load transfer effects of the interfaces under external loads were analyzed by scanning electron microscope (SEM). Results showed that with the increasing of PyC component thickness from.10 to.30 µm in the PyC/BN multiphase interfacial phases, the bending strength and fracture toughness both increased first and then decreased. The results occurred due to the competition between load transfer and stress release of the interfaces. The relatively optimized interfacial phase structure was that the thickness of the PyC interfacial phase and BN interfacial phase were.20 and.30 µm. The bending strength and fracture toughness of the optimized SiC/SiC composites reached 660.65 MPa and 29.01 MPa•m1/2. Respectively, many matrix cracks appeared in the horizontal and vertical directions, occupying almost the entire fracture section. The growth path of the matrix crack was significantly increased with many long fibers pulled out and broken, which was conducive to the strengthening and toughening of SiC/SiC composites. [ABSTRACT FROM AUTHOR]

This study investigates the production and assessment of fracture toughness in Polypropylene (PP) composites reinforced with different weight fractions of treated and untreated coconut coir fibres. The potential of natural fibres, especially those obtained from agricultural waste like coconut coir, to create lightweight, affordable, and environmentally friendly composite materials has drawn attention. In the study, coir fibres were cleaned and chemically treated with NaOH before being incorporated into PP using injection moulding and extrusion techniques. According to ASTM guidelines, composites with 10%, 20%, and 30% coir fibre concentrations underwent Single Edge Notched Bend (SENB) testing to determine their fracture toughness. The fracture toughness of composites containing 10% and 20% untreated coir fibres was found to be higher than that of pure PP, but composites containing 30% untreated and all treated coir fibres showed reduced fracture toughness. The best composite, with 20% untreated coir, showed the best mix of fibre content and material performance, emphasizing how chemical treatment hurt fibre brittleness and the composites' overall ability to support loads. The potential of untreated natural fibres to improve composite materials for industrial applications- particularly in the automotive industry- is highlighted by this study. [ABSTRACT FROM AUTHOR]

This study investigated the self-healing properties of PA6/COC blends, in particular, the impact of three compatibilizers on the rheological, microstructural, and thermomechanical properties. Dynamic rheological analysis revealed that ethylene glycidyl methacrylate (E-GMA) played a crucial role in reducing interfacial tension and promoting PA6 chain entanglement with COC domains. Mechanical tests showed that poly(ethylene)-graft-maleic anhydride (PE-g-MAH) and polyolefin elastomer-graft-maleic anhydride (POE-g-MAH) compatibilizers enhanced elongation at break, while E-GMA had a milder effect. A thermal healing process at 140 °C for 1 h was carried out on specimens broken in fracture toughness tests, performed under quasi-static and impact conditions, and healing efficiency (HE) was evaluated as the ratio of critical stress intensity factors of healed and virgin samples. All the compatibilizers increased HE, especially E-GMA, achieving 28.5% and 68% in quasi-static and impact conditions, respectively. SEM images of specimens tested in quasi-static conditions showed that all the compatibilizers induced PA6 plasticization and crack corrugation, thus hindering COC flow in the crack zone. Conversely, under impact conditions, E-GMA led to the formation of brittle fractures with planar surfaces, promoting COC flow and thus higher HE values. This study demonstrated that compatibilizers, loading mode, and fracture surface morphologies strongly influenced self-healing performance. [ABSTRACT FROM AUTHOR]

Understanding the mechanical properties of coal is crucial for efficient mining and disaster prevention in coal mines. Coal contains numerous cracks and fissures, resulting in low strength and challenges in preparing standard samples for testing coal fracture toughness. In engineering, indicators such as the hardness coefficient (f value) and Hardgrove grindability index (HGI) are straightforward to measure. Various experiments, including drop weight, grinding, uniaxial compressive strength and three-point bending experiments, were conducted using notched semi-circular bend (NSCB) specimens and particle sizes of 1–2 mm/0.425–1 mm. Theoretical and experimental results indicate that the hardness coefficient of coal and rock is proportional to the crushing work ratio and inversely proportional to the mean equivalent diameter. Moreover, the square of the fracture toughness of coal and rock is directly proportional to the crushing work ratio, inversely proportional to the newly added area, directly proportional to the mean equivalent diameter and directly proportional to the hardness coefficient. The Mode-I fracture toughness of coal and rock can be rapidly determined through the density, the equivalent diameter after crushing and the elastic modulus, with experimental verification of its accuracy. Considering that smaller particle sizes exhibit greater resistance to breakage, the distribution mode of new surface areas after particle breakage was established, influenced by the initial particle size and the energy of a single broken particle. This study can assist in quickly and accurately determining the fracture toughness of coal. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental investigation of the mechanical characteristics of 3D-printed acrylonitrile butadiene styrene (ABS) and its modifications reinforced with different types of short-fiber fillers: carbon, glass, and basalt. Elastic modulus, tensile and bending strength, as well as fracture toughness were determined in series of mechanical tests for samples produced with different manufacturing parameters, such as nozzle diameter and infill angle. It was found that the use of ABS filament reinforced with the short fibers can significantly improve the mechanical properties of 3D-printed devices when the infill angle is oriented along the vector of the applied load. In such a case, the elastic modulus and tensile strength can be increased by more than 1.7 and 1.5 times, respectively. The use of a larger nozzle diameter led to the growth of tensile strength by an average of 12.5%. When the macroscopic load is applied along the normal to the printed layers, the addition of short fibers does not give much gain in mechanical properties compared to pure ABS, which was confirmed by both standard tensile and fracture toughness tests. The surface of the fractured samples was examined using scanning electronic microscopy, which allowed us to make conclusions on the type of defects as well as on the level of adhesion between the polymeric matrix and different types of short fibers. [ABSTRACT FROM AUTHOR]

The present study examines the influence of polyamide 6.6 (PA 6.6) nanofiber and MWCNTs reinforcements on the mechanical behavior of nanocomposite plates formed by hybridization of carbon fabric (CF) and kevlar fabric (KF). First, PA 6.6 nanofibers were manufactured by electrospinning. The produced nanofibers were placed in the interlaminar of nanocomposite plates. PA 6.6 nanofiber and MWCNT‐reinforced nanocomposite plates consisting of 12 layers were produced by the vacuum bagging method. Tensile, Mode‐II fracture and bending tests were applied to the produced composite plates in accordance with the standards. After the mechanical tests, the nanocomposite plates' macro and micro damage analysis was performed. As a result of the reinforcement of PA 6.6, MWCNTs and PA 6.6‐MWCNTs, the tensile strength, interlaminar fracture toughness and bending strength of the nanocomposite plates significantly enhanced compared to unreinforced samples. In addition, interlaminar crack propagation in reinforced samples became more stable than in the unreinforced sample. Highlights: Investigated the impact of PA 6.6 nanofiber and MWCNT reinforcements on nanocomposite plates formed through CF and KF hybridization.Reinforcement with PA 6.6, MWCNTs, and PA 6.6‐MWCNTs significantly improved tensile strength, interlaminar fracture toughness, and bending strength.Mode‐II interlaminar fracture toughness tests demonstrated enhanced crack propagation stability with PA 6.6 nanofiber and MWCNT reinforcements. [ABSTRACT FROM AUTHOR]

An evaluation of the interlaminar fracture toughness of polyamide/glass fiber laminates with various layups is reported. Due to large differences in thermal expansion coefficients of fiber and binder the laminates with layups where single layers are swapped exhibit high warping. A technique for avoiding this is proposed, allowing evaluating interlaminar fracture toughness of various angle interfaces. Two different layups for evaluating the Mode I and II interlaminar fracture toughness are tested. The differences of delamination behavior of a number of different-angle fiber interfaces are shown and analyzed. The applicability of the proposed testing technique is discussed. [ABSTRACT FROM AUTHOR]

The J-integral is applied to the single cantilever beam (SCB) and double cantilever beam (DCB) test specimens subjected to both mixed-mode I and II loading and large displacements. The methods proposed and resulting closed-form theoretical equations allow for the instantaneous evaluation of J during laboratory tests, requiring only the applied load and angular rotation of the specimen loading link, loading points, and remaining ligament. These measurands can be acquired using a common load cell and markers, a digital video camera, and image analysis software. In general, the equations do require knowledge of the specimen elastic moduli and shear moduli, as well as the specimen linear dimensions. Since the test data can be analyzed and J determined throughout the test instantaneously, and since, due to geometric nonlinearities, the ratio of mode I and mode II loading will likely vary significantly throughout the test, each specimen can be used to generate multiple data points. If crack length is determined throughout the test, presumably by directly measuring the crack length optically, or if the load drops abruptly due to crack growth, then when the crack advances, critical values of J for mixed-mode loading can be determined using the methods and results presented. It is noted that moderate to large translational and rotational displacements may improve the accuracy of the results using these methods. The results are applicable to standard pure mode I or pure mode II SCB and DCB tests as well and reduce to known equations in those special cases. [ABSTRACT FROM AUTHOR]

This article discusses the use of numerical cohesive zone modeling (CZM) in analyzing self-anchoring additive manufacturing (AM) metal-CFRP joints. The study explores various anchor geometries and their effects on joint strength through numerical analysis using the CZM method. The article also mentions other research in the field of joint configurations, including investigations into mechanical properties, joining processes, fracture toughness, and adhesive characteristics. The authors emphasize the importance of lightweight structures in engineering applications and the need for innovative approaches to achieve durable joint configurations. The document discusses the use of the cohesive zone model (CZM) in analyzing the performance of adhesively bonded joints. The study validates the CZM method through simulations of single lap joints (SLJ) using different adhesives. The results show a correlation between the CZM simulations and experimental parameters, demonstrating the reliability of the methodology. The simulations also reveal that certain anchor geometries and adhesives result in higher failure loads, indicating a more robust joint design. The contact status of the joints is analyzed, and it is observed that complete separation occurs after the propagation of separation passes the second row of anchors. Overall, the CZM proves to be an effective tool for analyzing the performance of adhesively bonded joints. The document discusses the impact of different anchor geometries on joint strength. The study focuses on the assumption that joint failure occurs in cohesive or adhesive mode and aims to identify the optimal geometry for potential cohesive failure. The research evaluates the effectiveness of [Extracted from the article]

The fracture behavior of C/SiC composites after oxidation treatment for different time at 800 °C in air was studied by in-situ test technology combining DIC, AE and X-CT. From results of fracture toughness tests, it can be found that with the increase of oxidation time, the stress intensity factor and the work of fracture show different trends, and the fracture mode after oxidation changes from quasi-brittle to ductile. Combined with AE clustering analysis and X-CT images obtained through in-situ load tests, the mechanism of the coupling effect of oxidation time, toughening behavior and C-phase consumption on energy dissipation is explained. In addition, long-term oxidation causes the crack initiation point to deviate from the prefabricated notch tip and the delamination damage, which may lead to the change of failure position and unexpected damage mode in the engineering structures. • The K IC and the work of fracture of oxidized C/SiC show different trends. • AE signals reflect the PyC interface and carbon fibers oxidation consumption. • The coupling mechanism alters the energy dissipation in fracture process. • Oxidation changes the crack initiation position and damage modes. [ABSTRACT FROM AUTHOR]

The paper investigated the AW7075 aluminum alloy that is used in the automotive industry. The alloy is widely used, among others, in the production of heads and engine blocks. The possibility of obtaining various properties of the alloy (material states) by appropriate heat treatment (saturation and aging) was demonstrated. The results of strength, hardness, abrasion, and fracture toughness tests of the alloy in the T73, RRA, and HTPP aging treatments, in comparison with the T651 reference state, are presented. The need to select the appropriate parameters of heat treatment in relation to the load conditions of the structural element, especially in elements with notches, was indicated. Depending on the state of the AW7075 alloy, the results prove the wide and diverse possibilities of its use and should be used consciously in the design and production processes of modern automotive drivetrain components. [ABSTRACT FROM AUTHOR]

In this study, the interlaminar fracture toughness and impact strength of polyethersulfone reinforced with continuous carbon fibers were studied. Interlaminar fracture toughness tests were performed using the double cantilever beam method. It was shown that surface modification using the thermal oxidation method of the carbon fibers can strongly increase the interlaminar fracture toughness of the obtained composites. Thus, the maximum value reached 1.72 kJ/m2, which was 40% higher than the fracture toughness of the composites reinforced with initial carbon fibers. Moreover, fractographic analysis using a scanning electron microscope allowed us to highlight the main reasons for the dependence of fracture toughness on fiber content and surface modification conditions of the carbon fibers. It was shown that the main factor that allowed for an increase in fracture toughness was the enhanced interfacial interaction between the fibers and polymer matrix. Additionally, it was found that expectedly, there was a good correlation between interlaminar fracture toughness and interlaminar shear strength results. However, a negative influence of surface modification on the impact properties of composites was found. Such behavior occurred because of higher structural stability and lower exposure to delamination in multiple layers of the composites reinforced with the modified carbon fibers. It was found that impact energy reached ~150 kJ/m2 for the polyethersulfone-based composites reinforced with initial fibers, while the composites reinforced with modified carbon fibers showed impact energy values of only ~80 kJ/m2. Nevertheless, surface modification of carbon fibers using the thermal oxidation method can be an effective method for improving the performance properties of polyethersulfone-based composite materials. [ABSTRACT FROM AUTHOR]

This work aims to develop Co and Ni-free Ti(C,N)–Fe-based cermets which are essential for developing cermets in the direction of green and low-cost materials. TiC and Ti(C,N) -based cermets prove to evince excellent mechanical properties at high temperatures as compared to conventional WC-based cermets. A binder system based on Cr, Mo, Fe, and their alloys may offer a viable solution to replace carcinogen elements such as Ni and Co from the binder. In the present work, high chromium Ti(C,N)-30 wt% FeCrMo cermets were fabricated by using Pressureless liquid-phase sintering. Samples at different sintering temperatures were prepared to investigate the influence of the temperature on microstructural formation and their mechanical characteristics. Scanning Electron Microscopy (SEM) is employed to observe the microstructural formation. A microstructural analysis of the consolidated cermets reveals that the addition of Mo to the binder system and an increase in sintering temperature affect the carbide grain size and densification, which ultimately affect their mechanical characteristics. The hardness and fracture toughness were determined by the Vickers hardness test and Indentation fracture toughness (IFT) method respectively. The maximum Hardness, Fracture toughness, and Transverse rapture strength achieved for the Ti(C,N)–FeCrMo-based green cermets are 665 ± 6.7 MPa, 1396 ± 26 HV 30, and 9.23 ± 0.12 MPa m1/2 respectively. [ABSTRACT FROM AUTHOR]

In the present work, the effects of carbon-based nanofillers (0.5 wt%), i.e., graphene nanoplatelets (GNPs), carbon nanofibers (CNFs), and carbon nanotubes (CNTs), on the cryogenic temperature (77 K) mechanical properties of carbon fiber reinforced polymers (CFRPs) were investigated. The study utilized an ex situ conditioning method for cryogenic tests. The nanofillers were mixed with the epoxy matrix by a solvent-free fluidized bed mixing technique (FBM), while unidirectional carbon fibers were impregnated with the resulting nanocomposites to manufacture CFRP samples. Optical microscopy was employed to analyze the dispersion of the carbon-based fillers within the matrix, revealing a homogeneous distribution in nanocomposites containing GNPs and CNFs. Fracture toughness tests confirmed the homogeneity of the GNP-loaded systems, showing an improvement in the stress intensity factor (KC) by 13.2% and 14.7% compared to the unmodified matrix at RT (25 °C) and 77 K, respectively; moreover, flexural tests demonstrated a general increase in flexural strength with the presence of carbon-based nanofillers at both temperature levels (RT and 77 K). Additionally, interlaminar shear strength (ILSS) tests were performed and analyzed using the same ex situ conditioning method. [ABSTRACT FROM AUTHOR]

The high toughness of zirconia is paving the way for the development of new materials for application in TBC for gas turbine blades. The main aim of this work was the obtainment of tetragonal zirconia polycrystalline (TZP) with high density, from mixtures of high-purity powder of zirconia, yttria, and niobia with different compositions (14.5 to 21 mol%), through the processes of cold pressing by uniaxial pressing and by isostatic pressing, followed by air sintering processes at 1550 °C for 1 h. The samples were characterized for phase composition by X-ray diffraction, Rietveld analysis, and morphology by transmission electron microscopy and energy dispersive spectroscopy analyses. Mechanical and tribological resistance was evaluated by fracture toughness and nanoindentation tests as well as Weibull statistics. The incorporation of yttria and niobia resulted in relatively denser ceramics with stabilization of the tetragonal phase which was confirmed by detailed X-ray diffraction analysis. Modified ceramics for TBC with 17.5 mol% of yttria and niobia showed higher hardness and fracture toughness, 16.16 GPa and 173.38 GPa, respectively. Through nano hardness measurements, it was possible to verify the effect of the samples' ferroelasticity. Thus, the addition of niobia and yttria to zirconia represents an opportunity for the development of new materials with increasing mechanical and tribological resistance for TBC application. [ABSTRACT FROM AUTHOR]

The field strength effect on fracture toughness was tested for three alkaline earth (AE) aluminoborosilicate (ABS) glasses. This work explores the impact of modifier field strength (FS) on macro‐mechanical properties in line with previous works which examined the FS effect on structure, hardness, crack resistance, and elastoplastic properties of alkali and AE‐ABS glasses. Fracture toughness (KIcVNB) was found to increase as modifier FS increased; and the elastoplastic ratio (HV/E) correlated well with plasticity, hardness, and fracture toughness. The purpose of this work is to examine the mechanical response of AE‐ABS glasses at a larger length scale in order to determine whether the field strength effect is active as was observed at lower length scales in previous works. The observed increase and decrease of the KIcVNB and HV/E, respectively, with increasing modifier FS, suggest a strong correlation between increasing fracture toughness and crack resistance with increasing plasticity for the AE‐ABS glasses studied. [ABSTRACT FROM AUTHOR]