Single Edge Notched Beam Research Articles

Investigating the influence of various three-point bending specimen configurations on rock fracture parameters testing: an experimental study

The fracture parameters of rocks, including fracture toughness and fracture energy, represent their resistance to crack propagation under external stress. These parameters play a critical role in engineering design, construction safety, geological mechanics research, and rock material assessment. This study determined the fracture parameters of granite under Mode I loading conditions using notched semicircular bend (NSCB) and single-edge notched beam (SENB) specimens. Although there was little difference between the initial and unstable fracture toughness values of the two specimen configurations, significant differences were observed in the fracture process and other fracture parameters. For example, the NSCB specimen exhibits a higher elastic modulus, and it witnessed rapid failure after reaching the peak load, whereas the SENB specimen displayed a more gradual failure process with a distinct post-peak stage. This may be one of the reasons for the higher fracture energy in the NSCB specimen than in the SENB specimen. Based on finite element analysis and the extraction of the tangential stress at the crack tip region, the application of the maximum tangential stress fracture criterion provided a robust explanation for the coherence observed in the unstable fracture toughness test results between the two specimen configurations.

Crack development and fracture performance of Recycled Powder Engineered Cementitious Composites (ECC): Experimental investigation

In this paper, recycled concrete powder (RCP) and recycled brick powder (RBP), with particle sizes ranging from 10 to 130 μm, are used to completely replace the fine aggregate quartz sand at a ratio of 1:1. On this basis, recycled glass powder (RGP), with a discussed particle sizes range of 38–300 μm, is used to partially substitute the cementitious materials. Polyethylene (PE) fibers are used as the reinforcement in the Engineered Cementitious Composites (ECC). Using the particle size range and substitution rate of RGP as variables, the crack development, crack mouth opening displacement (CMOD), fracture toughness and fracture energy of Recycled glass powder ECC (RGP-ECC) were discussed through a three-point bending experiment on a single-edge notch beam. A relatively comprehensive evaluation was made on the fracture performance and behavior of recycled ECC, and a suitable mix ratio of recycled powder ECC was given. The results show that the addition of various recycled powders will not affect the multi-slit cracking behavior of ECC, and the cracks can still spread densely, giving the specimen greater deformation capacity and CMOD. The total substitution of fine aggregate by RCP and RBP has a positive impact on the fracture toughness KICini, KICun and fracture energy (GF), but the addition of RGP has some minor negative effects. Among the particle size range and substitution rate of RGP, the influence of substitution rate is more obvious, and the fracture performance will show a downward trend after growth as the substitution rate increases. Choosing the appropriate RGP substitution rate and particle size range can maximize the recycling of construction waste while ensuring fracture performance.

Experimental study on crack propagation characteristics of unconventional reservoir rocks

This study investigates the fracture behaviour of three types of specimens (shale, sandstone, and coal), which are commonly found in unconventional reservoirs, based on mode Ⅰ single-edge notch beam (SENB) test. We employ the Digital Image Correlation technique to track the strain evolution and crack propagation paths of the three types of materials and compare their fracture characteristics. The experimental results show that both the surface roughness and crack initiation angle of the coal are larger comparing with that of sandstone and shale, which demonstrates the ductile property of coal and fracturing difficulty in coal seam. Moreover, the average velocity difference of crack propagation is obvious, which is 53.76 × 103, 453, and 0.33 mm/s in shale, sandstone, and coal, respectively. The elastoplastic J-R curves, which reflects the influence of the plastic zone, are presented to analyze the energy dissipation characteristics of three types of specimens during crack propagation. It is found that the J-integral of shale and sandstone does not increase with crack propagation, but the J-integral of coal shows obvious increasing trend with crack propagation due to the effect of plasticity. In addition, microscopic analysis is conducted using a petrographic microscope and scanning electron microscope (SEM) to explain the plastic zone differences at the notch tips of shale, sandstone, and coal. This study is a preliminary and significant step of hydraulic fracturing application in unconventional reservoirs for efficient recovery of the berried natural gas.

Fracture toughness determination for epoxy-based polymer concrete mixtures: Applicability of different rectangular beam and circular disc specimens

The purpose of this study was to examine the potential impact of the testing procedure, the shape of the test sample, loading method and sample size on the KIc value of polymer concrete (PC) materials. The research involved experimental investigations using five different testing techniques and specimen types, namely the single edge notched beam (SENB), short bend beam (SBB), semi-circular bend (SCB), edge notch disc bend (ENDB), and center cracked Brazilian disc (CCBD). A typical PC mixture made of mineral silicious aggregate, ML506 epoxy resin, chopped E-glass, and foundry sand filler. Despite the difference in the shape and loading type of the tested samples, the KIc data obtained from all groups of specimens are in good agreement with together and with the SENB proposed by RILEM. Depending on the test type, the KIc value varied from 1.43 to 1.74 MPa.m0.5 and the discrepancy between the data was mainly attributed to the type of loading (compression or bending) and the crack type (center crack or edge crack). The T-stress affects the fracture toughness for different testing samples and configurations. The lowest fracture toughness corresponds to the CCBD specimen (the center cracked disc loaded diametrically). The other test samples with edge cracks and loaded by a three-point bend setup showed KIc = 1.7 - 1.74 MPa.m0.5. Moreover, the fracture toughness data for PC mixtures can be achieved by utilizing sub-sized samples like SBB (for smaller amounts of PC material) instead of larger beam samples (i.e., SENB).

Mechanism of physical hardening on the fracture characteristics of polymer-modified asphalt binder

This article aims to reveal the physical hardening mechanism of polymer-modified asphalt binder (PMA) and accurately assess its impact on the low-temperature fracture properties of asphalt binders. Base asphalt binder (BA), styrene–butadiene–styrene modified asphalt binder (SBSMA), and crumb rubber modified asphalt binder (CRMA) were used as the research objects. Molecular dynamics (MD) simulation and differential scanning calorimetry (DSC) test were used to investigate the physical hardening mechanism of PMA at the microscopic level. The fracture characteristics of PMA under physical hardening were analyzed based on the single-edge notched beam (SENB) test. The results show that under prolonged cold service conditions, the asphalt molecular mobility is weakened, the non-bond energy and the free volume are reduced, and the molecules undergo aggregation state transformation, leading to the physical hardening of asphalt materials. In the process of physical hardening of asphalt molecules in the micro-Brownian motion of the main active force from the aromatic and saturate fractions. Considering the effect of physical hardening, it is recommended that the method used to test the low temperature properties of asphalt binders should ensure a constant temperature for at least 24 h. The crack tolerance (Ct) is recommended as the evaluation index of low-temperature cracking resistance of PMA in cold regions. The Ct of BA, SBSMA, and CRMA are reduced by 52.88 %, 12.04 %, and 35.24 %, respectively, after 24 h of constant low temperature. This indicating that the polymer modifiers can improve the fluidity of asphalt molecules, inhibit molecular aggregation, and reduce the effect of physical hardening on asphalt binders. Thermo-oxidative aging can aggravate the physical hardening phenomenon of asphalt binder, and the higher the degree of thermo-oxidative aging, the more severe the physical hardening of asphalt binder. The related research results provide the theoretical basis and technical support for the accurate design and development of the low-temperature performance of asphalt binders for roads in cold regions.

Composition optimization of PMMA base denture reinforced with different percentages of Nano Hydroxyapatite and alumina particles to obtain highest KIc and KIIc values using hybrid IWO/PSO algorithm

Composition of three-phase dental denture (Polymethyl methacrylate or PMMA + Nano Hydroxyapatite + Nano Alumina) was optimized using hybrid IWO/PSO algorithm to obtain the highest KIc and KIIc. First, initial fracture toughness tests were performed on nine groups of PMMA base dentures with different percentages of ingredients. Symmetric single edge notch beam and asymmetric three-point bend beam with inclined crack were used for KIc and KIIc testing, respectively. The initial design parameters were considered as: {75–100% PMMA, 0–10% Nano Hydroxyapatite and, 0–15% Nano Alumina}. As the initial guess values for starting the hybrid optimization algorithm, B-spline curves (as the cost function) were fitted to the experimental results of both modes I and II. Then the IWO/PSO algorithm was run to find the optimum composition and maximum fracture toughness value of each mode. The best KIc was found for the composition of {78.5% PMMA + 9% Nano Hydroxyapatide + 12.5% Nano Alumina}. Similarly, using the hybrid IWO/PSO algorithm the optimum composition of {83.4% PMMA + 8.7% Nano Hydroxyapatide + 7.9 % Nano Alumina} was obtained to gain the highest KIIc. The experimental fracture toughness values obtained from the proposed compositions via employing the hybrid algorithm were approximately 40% higher than the all tested nine groups of PMMA base dentures under both modes I and II. The fracture toughness ratio KIIc/KIc of the optimum mix-designs predicted by the hybrid algorithm was equal to 0.78 and showed good agreement with the experimental KIIc/KIc ratio. The fracture toughness for any desired mixed mode condition can also be predicted in-terms of the KIc and stress intensity factors and T-stress of the desired mode mixity.

Fracture Behavior of Concrete under Chlorine Salt Attack Exposed to Freeze-Thaw Cycles Environment.

Fracture behavior is one of the key properties to study concrete cracking under sodium chloride attack exposed to the freeze-thaw cycles environment, which is frequently neglected. In this paper, 24 single edge notch beam specimens and 24 cubes were poured. The corresponding freeze-thaw cycles test in sodium chloride solution, standard cube compressive strength of concrete test, and three-point-bending tests were carried out. The research revealed that the fracture toughness, fracture energy, relative dynamic modulus of elasticity, and standard cube compressive strength were decreased by increasing freeze-thaw cycles under sodium chloride attack, and the damage degree of concrete caused by sodium chloride solution was deeper than that of pure water. In particular, there existed good linear correlation between the fracture behavior and imposed freeze-thaw damage for various solution. Accordingly, a more reliable damage model using fracture control parameters as damage factors was proposed.

Effect of TaC and graphene nanoplatelets on the microstructure and mechanical properties of ZrB2

In this experiment, in order to investigate the effect of TaC addition on the microstructure, densification and mechanical properties of ZrB2 composites reinforced with graphene nanoplatelets (GNP), three composites were fabricated via spark plasma sintering (SPS) at 1900 °C. Relative density was determined by Archimedes method. The XRD and EDS analyses were used to explore the phase composition and elemental distribution. Also, Field emission scanning electron microscopy (FE-SEM) was employed to characterize the microstructure (grain size and porosity). Flexural strength, fracture toughness and hardness were determined by three-point bending test, single-edge notched beam (SENB) and macro and micro Vickers methods, respectively. The results showed that the presence of the GNP, alone and combined with TaC, increases the relative density sharply to 99.6 %. In addition, full densification occurred by the addition of 10 and 20 vol% TaC compared to the monolithic ZrB2 ceramic with 83 % relative density. Maximum flexural strength and fracture toughness of 580 MPa and 4.5 MPa.m0.5 were obtained, respectively, for ZrB2- GNP and ZrB2- GNP doped with 10 vol% TaC.

Mechanical performance of e-glass reinforced polyester resins (isophthalic and orthophthalic) laminate composites used in marine applications

This study examined the mechanical performance of two polyester resins (isophthalic and orthophthalic) used to create e-glass-based laminate composites for the marine industry. The current study performed a static analysis of laminate composites using compressive, impact and hardness tests. Single edge-notched beam (SENB) fracture tests under mode I (i.e. opening mode) were performed on e-glass reinforced orthophthalic polyester laminate composites (S1) and e-glass reinforced isophthalic polyester laminate composites (S2) at cryogenic temperature (−10°C), ambient temperature (25°C) and high temperature (100°C). The interaction between fibres and matrix material was studied using Fourier transform infrared (FTIR) spectroscopy. A scanning electron microscope (SEM) was used to examine the substructure of fractured surface. A water absorption test was also performed on the fabricated samples. FTIR study revealed NH stretching, CH bend, CN stretching, C-O-C and CH-stretching. e-Glass isophthalic polyester composites had higher compressive strength, impact strength, hardness, fracture toughness and fracture energy than orthophthalic polyester laminate composites. The decrease in temperature increased the fracture properties. In both types of laminate composites, as the temperature increased, the fracture toughness and fracture energy decreased. The diffusion and permeability coefficients of isophthalic composites were greater than those of orthophthalic-based composites. The crushed fibre, fibre pull-out, riverline, matrix-fibre delamination and debonding are all evident in the fractured surface SEM micrograph.

Experimental Study on the Fracture Toughness of Bamboo Scrimber.

In the past decade, bamboo scrimber has developed rapidly in the field of building materials due to its excellent mechanical properties, such as high toughness and high tensile strength. However, when the applied stress exceeds the ultimate strength limit of bamboo scrimber, cracks occur, which affects the performance of bamboo scrimber in structural applications. Due to the propensity of cracks to propagate, it reduces the load-bearing capacity of the bamboo scrimber material. Therefore, research on the fracture toughness of bamboo scrimber contributes to determining the material's load-bearing capacity and failure mechanisms, enabling its widespread application in engineering failure analysis. The fracture toughness of bamboo scrimber was studied via the single-edge notched beam (SENB) experiment and compact compression (CC) method. Nine groups of longitudinal and transverse samples were selected for experimental investigation. The fracture toughness of longitudinal bamboo scrimber under tensile and compressive loadings was 3.59 MPa·m1/2 and 2.39 MPa·m1/2, respectively. In addition, the fracture toughness of transverse bamboo scrimber under tensile and compressive conditions was 0.38 MPa·m1/2 and 1.79 MPa·m1/2, respectively. The results show that, for this material, there was a significant distinction between longitudinal and transverse. Subsequently, three-point bending tests and simulations were studied. The results show that the failure mode and the force-displacement curve of the numerical simulation were highly consistent compared with the experimental results. It could verify the correctness of the test parameters. Finally, the flexural strength of bamboo scrimber was calculated to be as high as 143.16 MPa. This paper provides data accumulation for the numerical simulation of bamboo scrimber, which can further promote the development of bamboo scrimber parameters in all aspects of the application.

Phase field model for mixed mode fracture in concrete

Concrete is a quasi-brittle material and generally fails in mixed mode I-II fracture. The fracture energy release in mode I and mode II during crack propagation is usually different. However, the tensile test fracture toughness has generally been considered in most of the numerical models to study fracture in concrete. In this paper, a phase field model is presented which considers the fracture energy of mode I and mode II for mixed mode I-II fracture simulation in concrete. In addition, it uses a fracture mode controlling parameter χ which, in a sense, controls the governing failure criterion. The post-peak material response is modeled using a cohesive zone approach. The effect of the length scale parameter, mesh size and χ is investigated. For validation, a single-edge notch beam with a notch at various eccentricities is considered. It is shown that the model is mesh independent for a sufficiently fine mesh in cracking region. Also, the effect of the length scale parameter on global response is insignificant. It is observed that χ≥1 gives satisfactory results both for mode I and mixed mode I-II fracture in single edge notch concrete beam. The numerical results for the load–displacement curve are compared with the experimental data both qualitatively and quantitatively. It is concluded that the proposed phase field model can simulate mode I and mixed mode I-II fracture in concrete with sufficient accuracy.

A modified single edge V-notched beam method for evaluating surface fracture toughness of thermal barrier coatings

The surface fracture toughness is an important mechanical parameter for studying the failure behavior of air plasma sprayed (APS) thermal barrier coatings (TBCs). As APS TBCs are typical multilayer porous ceramic materials, the direct applications of the traditional single edge notched beam (SENB) method that ignores those typical structural characters may cause errors. To measure the surface fracture toughness more accurately, the effects of multilayer and porous characters on the fracture toughness of APS TBCs should be considered. In this paper, a modified single edge V-notched beam (MSEVNB) method with typical structural characters is developed. According to the finite element analysis (FEA), the geometry factor of the multilayer structure is recalculated. Owing to the narrower V-notches, a more accurate critical fracture stress is obtained. Based on the Griffith energy balance, the reduction of the crack surface caused by micro-defects is corrected. The MSEVNB method can measure the surface fracture toughness more accurately than the SENB method.

Intermediate Temperature Fracture Resistance of Stone Matrix Asphalt Containing Untreated Recycled Concrete Aggregate

The sustainable alternative of blending natural limestone aggregates (NAs) with recycled concrete aggregate (RCA) was investigated in this research in order to encourage the utilization of recycled concrete in heavy traffic paving applications. The Marshall Mix design method was used to optimize mix designs containing 0%, 10%, 35% and 50% RCA. Single-edge notched beam (SENB) and semi-circular bending (SCB) tests were then applied and the fracture energy and fracture toughness determined. The tests were conducted at intermediate temperatures (5 °C, 15 °C, 25 °C) and varying notch depths (0.2H, 0.3H and 0.4H). Fracture energy and toughness did not consistently follow the behaviour of mixes with only NA; however, it was determined in this study that a RCA content between 10% and 35% would achieve peak loads, fracture energies and fracture toughness values comparative to a virgin mix.

Simulation of low-temperature brittle fracture of asphalt mixtures based on phase-field cohesive zone model

In this study, a phase-field cohesive zone model (CZM) was presented to simulate the low-temperature brittle fracture of asphalt mixture by finite element method (FEM). The phase-field CZM was applied directly to simulate low-temperature homogeneous fracture of asphalt mixtures. Furthermore, a combination method was proposed for the heterogeneous fracture analysis of asphalt mixtures at low temperature. In this method, the phase-field CZM and the conventional interface CZM are used to simulate the cohesive fracture within the fine aggregate matrix (FAM) and the adhesive fracture at the FAM-aggregate interface, respectively. Then, the applicability of the phase-field CZM to simulate mixed-mode fracture in asphalt mixtures was analyzed by the single-edge notch beam tests with different notch offsets. Furthermore, the cohesive fracture simulation of asphalt mixture based on phase-field CZM and interface CZM was compared. The results indicate that the numerical results based on the phase-field CZM in both homogeneous and heterogeneous fracture analysis are in good agreement with the experimental results. The softening curve of the interface CZM gradually converges to that of the phase-field CZM as the adhesive stiffness increases. Under the same traction-separation law, the crack path predicted by the combination method is similar to that of the pure CZM method. However, the combination method shows a more pronounced brittle behavior of the material. In addition, the combination method has higher computational efficiency and requires less computational memory. In summary, this study provides an effective method to simulate homogeneous and heterogeneous brittle fracture of asphalt mixture at low temperatures.

Failure analysis of the edge-notched beam test on fluid-exposed Berea Sandstone

Injection of fluids during wastewater disposal and geologic carbon sequestration causes induced stress and changes in rock’s elastic and failure properties, such as elastic moduli and fracture toughness. An accurate understanding of such changes in the response requires modeling and analysis of fluid-induced changes in rock’s stress and deformation states for which core-scale mechanical loading tests are often employed. Using experiments and simulations of Single Edge Notched Beam (SENB) test on water-exposed and supercritical (sc) CO_2-exposed Berea sandstones, we quantify the effect of pore fluid on tensile crack propagation, spatial distributions of shear and tensile stresses, and fracture toughness and J-integral properties. We use Digital Image Correlation (DIC) to monitor the changes in local stress and deformation fields during crack initiation and propagation. A representative numerical simulation model of dynamic crack propagation under SENB loading is built using the extended finite element method. Results are analyzed using the stress path analysis to identify shear and tensile stress concentration regions, which provide precursory information for failure events during the test. Stress profiles along and across the growing crack are analyzed and compared with Irwin’s classical solutions to understand the impact of SENB loading. Evolution in stress intensity factor and crack length shows subcritical crack growth prior to Griffith-like failure at the structure scale.

A phase-field cohesive zone model for fracture simulation of asphalt mixture

The traditional cohesive zone model (CZM) based on interfacial damage mechanics has been widely used in quasi-brittle fracture simulation of asphalt mixture at low temperature. However, the traditional CZM is mesh dependent in the cohesive fracture simulation. This study aims to introduce a phase field method (PFM) to simulate brittle failure of asphalt mixture. The model was implemented in a framework of finite element method (FEM). The uniaxial tensile test was used to simulate the sensitivity of parameters that may affect the results. Furthermore, typical laboratory tests for evaluating the crack resistance of asphalt mixtures, such as the single-edge notched beam (SEB) test and the semi-circular bending (SCB) test, were simulated to validate the suitability of the PFM. Moreover, the numerical results and computational efficiency of the PFM-based cohesive fracture simulation within FAM was also discussed and compared with those based on CZM. The results indicate that the numerical results of the typical failure tests based on PFM are in good agreement with the experimental results at both macro and micro scales. In addition, the numerical results of cohesive fracture simulation within FAM based on PFM and CZM are slightly different. The brittle behavior of the asphalt mixture predicted based on PFM was more pronounced compared to the results predicted by CZM. Moreover, the cohesive fracture simulation based on PFM requires less computational memory and time. In general, this paper successfully introduced a PFM to study the quasi-brittle failure of asphalt mixture.

Effect of ribose incubation on physical, chemical, and mechanical properties of human cortical bone

Raman spectroscopy (RS) is sensitive to the accumulation of advanced glycation end-products (AGEs), and it measures matrix-sensitive properties that correlate with the fracture toughness of human cortical bone. However, it is unclear whether sugar-mediated accumulation of AGEs affects the fracture toughness of human cortical bone in a manner that is consistent with the negative correlations between amide I sub-peak ratios and fracture toughness. Upon machining 64 single-edge notched beam (SENB) specimens from cadaveric femurs (8 male and 7 female donors between 46 years and 61 years of age), pairs of SENB specimens were incubated in 15 mL of phosphate buffered saline with or without 0.1 M ribose for 4 weeks at 37 °C. After acquiring 10 Raman spectra per bone specimen (n = 32 per incubation group), paired SENB specimens were loaded in three-point bending at a quasi-static or a high loading rate approximating 10−4 s−1 or 10−2 s−1, respectively (n = 16 per incubation group per loading rate). While 2 amide I sub-peak ratios, I1670/I1640 and I1670/I1610, decreased by 3–5% with a 100% increase in AGE content, as confirmed by fluorescence measurements, the ribose incubation to accumulate AGEs in bone did not affect linear elastic (KIc) nor non-linear elastic (KJc) measurements of bone's ability to resist crack growth. Moreover, AGE accumulation did not affect the change in these properties when the loading rate changed. Increasing the loading rate increased KIc but decreased KJc. Ribose incubation did not affect mineral-related RS properties such as mineral-to-matrix ratios, Type B carbonate substitutions, and crystallinity. It did however increase the thermal stability of demineralized bone (differential scanning calorimetry), without affecting the network connectivity of the organic matrix (i.e., maximum slope during a hydrothermal isometric tension test of demineralized bone). In conclusion, RS is sensitive to AGE accumulation via the amide I band (plus the hydroxyproline-to-proline ratio), but the increase in AGE content due to ribose incubation was not sufficient to affect the fracture toughness of human cortical bone.

A Review of Experimental Research on the Mode I Fracture Behavior of Bamboo

Bamboo is an eco-friendly material with light weight, high strength, short growth cycle and high sustainability, which is widely used in building structures. Engineered bamboo has further promoted the development of modern bamboo structures due to its unrestricted size and shape. However, as a fiber-reinforced material, fracture damage, especially Mode I fracture damage, becomes the most likely damage mode of its structure, so Mode I fracture characteristics are an important subject in the research of mechanical properties of bamboo. This paper summarizes the current status of experimental research on the Mode I fracture properties of bamboo based on the three-point bending (TPB) method, the single-edge notched beam (SENB) method, the compact tension (CT) method and the double cantilever beam (DCB) method, compares the fracture toughness of different species of bamboo, analyzes the toughening mechanisms and fracture damage modes, discusses the applicability of different theoretical calculation methods, and makes suggestions for future research priorities, aiming to provide a reference for future research and engineering applications in related fields.

APPLICABILITY ASSESSMENT OF THE VICKERS INDENTATION FOR DETERMINING THE FRACTURE TOUGHNESS OF YTTRIA-STABILIZED ZIRCONIA

Crack growth resistance of ZrO2-(3-8) mol% Y2O3 ceramics was investigated. Young's modulus by the ultrasonic flaw detection method were determined. Vickers hardness and parameters of cracks after Vickers indentation were obtained. Based on the Young's modulus values, Vickers hardness, and parameters of cracks, the fracture toughness of the investigated ceramics was calculated using 9 different equations of the Vickers indentation method. A comparative analysis of the calculated fracture toughness values with those obtained by the single-edge notch beam method was carried out. It was found that choosing the optimal equation for calculating fracture toughness by the Vickers indentation method is quite difficult and requires comparison with the results of standardized tests. It was shown that to determine crack resistance characteristics of the yttria-stabilized zirconia ceramics, the use of only the Vickers indentation method without comparison with other methods of fracture mechanics is incorrect.

Fracture toughness and brittleness of novel CAD/CAM resin composite block.

To evaluate the fracture toughness and brittleness of a newly developed CAD/CAM resin composite block and compare it with five other resin composite blocks and one polymer-infiltrated ceramic block. Fracture toughness was determined through single-edge notched beam (SENB) method according to ASTM D5045-14. Parallelepiped specimens (thickness × width × length = 1.8×3.6×∼18mm) with a V notch (length=∼1.8mm) (n=10) were made from block materials using a low-speed water-cooled diamond precision saw and razor blade. Brittleness index (BI) was calculated from Vickers hardness and fracture toughness. Data were analyzed using one-way ANOVA and post-hoc Tukey tests (p≤0.05). The experimental block showed significantly higher fracture toughness than all commercial block materials (p<0.001) and has a brittleness index similar to most commercial blocks (p>0.05) which have significantly lower brittleness index than Vita Enamic (p<0.001). A moderate or strong correlation was observed between fracture toughness and flexural strength (Pearson's correlation coefficient R=0.66) or diametral tensile strength (R=0.86) or filler loading (R=0.66), and between brittleness and Vickers hardness (R=0.87). The new composite block exhibited significantly higher fracture toughness and lower brittleness among the commercial CAD/CAM composite block materials tested, indicating a lower tendency to fracture and marginal chipping, and better machinability. The new composite block with higher fracture toughness and lower brittleness is suitable to use in the fabrication of CAD/CAM indirect restorations with potential long-term clinical success.