Fracture Surface Features Research Articles

Effect of Radiation Crosslinking and Surface Modification of Cellulose Fibers on Properties and Characterization of Biopolymer Composites.

Recently, polymers have become the fastest growing and most widely used material in a huge number of applications in almost all areas of industry. In addition to standard polymer composites with synthetic matrices, biopolymer composites based on PLA and PHB matrices filled with fibers of plant origin are now increasingly being used in selected advanced industrial applications. The article deals with the evaluation of the influence and effect of the type of surface modification of cellulose fibers using physical methods (low-temperature plasma and ozone application) and chemical methods (acetylation) on the final properties of biopolymer composites. In addition to the surface modification of natural fibers, an additional modification of biocomposite structural systems by radiation crosslinking using gamma radiation was also used. The components of the biopolymer composite were a matrix of PLA and PHBV and the filler was natural cellulose fibers in a constant percentage volume of 20%. Test specimens were made from compounds of prepared biopolymer structures, on which selected tests had been performed to evaluate the properties and mechanical characterization of biopolymer composites. Electron microscopy was used to evaluate the failure and characterization of fracture surfaces of biocomposites.

Fractography of Long Bones with High-Velocity Projectile Trauma

Previous studies of bone fractography have examined only cases of blunt trauma. Here we assess whether fracture surface features are also found on bones subjected to high-velocity projectile trauma. Civil War–era long bones were assessed for the presence of fracture surface features identified in previous studies. Of 60 bones examined, which included all major long bones, fracture surface features were identified on 57 (95%). Arrest ridges and cantilever curl were located most often and were observed on most specimens (85% and 72% of cases, respectively). Bone mirror was observed, though less frequently (2% of cases); no instances of bone hackle or wake features were found. There does not appear to be a relationship between the number of observed features and bone type or projectile type. These results demonstrate that fractography features are observed in fractures related to high-velocity projectile trauma, but additional research is needed to understand the relationship between projectile trauma and the location and orientation of these features.

On the Strain Rate Sensitivity of Fused Filament Fabrication (FFF) Processed PLA, ABS, PETG, PA6, and PP Thermoplastic Polymers

In this study, the strain rate sensitivity of five different thermoplastic polymers processed via Fused Filament Fabrication (FFF) Additive Manufacturing (AM) is reported. Namely, Polylactic Acid (PLA), Acrylonitrile-Butadiene-Styrene (ABS), Polyethylene Terephthalate Glycol (PETG), Polyamide 6 (PA6), and Polypropylene (PP) were thoroughly investigated under static tensile loading conditions at different strain rates. Strain rates have been selected representing the most common applications of polymeric materials manufactured by Three-Dimensional (3D) Printing. Each polymer was exposed to five different strain rates in order to elucidate the dependency and sensitivity of the tensile properties, i.e., stiffness, strength, and toughness on the applied strain rate. Scanning Electron Microscopy (SEM) was employed to investigate the 3D printed samples’ fractured surfaces, as a means to derive important information regarding the fracture process, the type of fracture (brittle or ductile), as well as correlate the fractured surface characteristics with the mechanical response under certain strain rate conditions. An Expectation–Maximization (EM) analysis was carried out. Finally, a comparison is presented calculating the strain rate sensitivity index “m” and toughness of all materials at the different applied strain rates.

Tensile and ductile fracture properties of as-printed 316L stainless steel thin walls obtained by directed energy deposition

Mechanical properties of as-printed 316L stainless steel thin-walled structures obtained by directed energy deposition are investigated. In-situ tensile and fracture tests are performed on small samples obtained from a additively manufactured square section tube and extracted with three different orientations with respect to the part build direction. Despite a strongly oriented microstructure resulting from the process, as-printed specimens exhibit a reduced anisotropy in comparison with thick or polished samples commonly reported in the literature. Moreover, it is shown using a simple model that the reduced dentified anisotropy can be explained by considering the material thickness variation pattern only, resulting from the layer stacking process. Fracture tests are analyzed using an adapted digital image correlation procedure that evaluates the specimen fracture toughness from experimentally computed J-integrals. Using time reversal, strain fields in regions close to the crack path are identified. Stress fields are then computed from the constitutive behavior identified in tensile tests. A regularization procedure is proposed to enforce the stress equilibrium. Finally, the J-integral is computed using various integration contours in order to validate its path-independance. On this basis, a nearly isotropic fracture toughness is identified. Additional scanning electron microscope observations show that fracture surface features are independent from specimen orientation. This apparent isotropy is explained by the isotropic distribution of lack-of-fusion defects driving crack initiation and propagation.

Effect of loading rate on cohesive parameters of the adhesive Araldite 2015

Abstract This study addresses the effect of loading rates on cohesive parameters and microstructural composition of the Araldite 2015 adhesive. Double Cantilever Beam (DCB) samples were tested under the loading rates of 1, 5, 10, 20, 100 and 200 mm × min-1. The Park-Paulinho-Roeser model (PPR model) was used to get cohesive parameters. In modelling of the softening behavior, inverse analyses were performed using the date obtained from the PPR softening curves. It was seen that the fracture energy and cohesive parameters are decreasing with increasing the loading rate. However, there seems to be a transition region where the fracture energy nearly remains constant. Microstructural analyses were implemented in order to study the effects of the loading rates on the characteristics of the fracture surfaces. It was concluded that the loading rates greatly influence the distribution of micro-voids in the epoxy matrix. Moreover, the presence of voids in epoxy matrix improved the plastic deformation around the crack tip and increased the fracture toughness.

Comportamiento macromecánico de uniones soldadas de superficie (AA5083) utilizando soldadura con gas inerte de tungsteno con recocido de homogeneización en una sola etapa

Las uniones soldadas de superficie se consideran una estrategia avanzada e innovadora para lograr una resistencia aceptable sin consumir excesiva energía en la preparación de las muestras. Se soldaron dos superficies planas de la aleación AA5083 desde cuatro lados y utilizando el mismo material de relleno. En el análisis de la soldadura de superficie, se logró una profundidad de fusión de hasta 2 - 2,2 mm en cada lado, aunque la parte central permaneció sin fusionar. Después de la unión, se realizó un recocido de homogeneización a 275 y 325 °C durante 3 h, lo que aumentó el rendimiento de la unión hasta un 57,6%. Las micrografías ópticas de las zonas fusionadas han permitido la visibilidad de combinación alternativa de Al6(Mn, Fe) y Mg2Si con el aumento de la temperatura de recocido de 275 a 325 °C. Las observaciones de la superficie de la fractura incluyen el límite de la interface de la zona completamente fusionada (CFZ) y la zona fusionada del material base (BMFZ), que en combinación definieron todo el mecanismo de la fractura.

Investigation of the Effect of Magnification, Accelerating Voltage, and Working Distance on the 3D Digital Reconstruction Techniques.

In this study, the effect of Scanning Electron Microscopy (SEM) parameters such as magnification (M), accelerating voltage (V), and working distance (WD) on the 3D digital reconstruction technique, as the first step of the quantitative characterization of fracture surfaces with SEM, was investigated. The 2D images were taken via a 4-Quadrant Backscattered Electron (4Q-BSE) detector. In this study, spherical particles of Ti-6Al-4V (15-45 μm) deposited on the silicon substrate were used. It was observed that the working distance has a significant influence on the 3D digital rebuilding method via SEM images. The results showed that the best range of the working distance for our system is 9 to 10 mm. It was shown that by increasing the magnification to 1000x, the 3D digital reconstruction results improved. However, there was no significant improvement by increasing the magnification beyond 1000x. In addition, results demonstrated that the lower the accelerating voltage, the higher the precision of the 3D reconstruction technique, as long as there are clean backscattered signals. The optimal condition was achieved when magnification, accelerating voltage, and working distance were chosen as 1000x, 3 kV, and 9 mm, respectively.

Effect of vacuum pressure on small crack propagation in Ti-6Al-4V

In this study, small crack propagation tests are conducted on artificially defected specimens of Ti-6Al-4V under air and vacuum pressures of 100 Pa, 10−2 Pa, 10−4 Pa, and 10−6 Pa. Fracture surfaces between these environments are compared, and the effect of vacuum pressure on the crack propagation process is investigated. The similarities between surface cracks in vacuum and internal cracks in the very high cycle regime are also discussed from the perspectives of crack propagation rate and fractographic characteristics. From the results, it was observed that there was a tendency for the crack initiation life to increase and the crack propagation rate to decrease with a decrease in the vacuum pressure, although no notable distinction was observed in air and under 100 Pa. The fractography exhibited an angular surface with sharp edges in air and under 100 Pa. However, a granular feature with rounded edges was observed below 10−2 Pa and became more pronounced as the vacuum pressure decreased. The window periods, which formed an oxidized surface coverage, were believed to account for the vacuum effect on crack propagation rate and fracture surface features. Both the crack propagation rate and fractographic features of surface cracks under 10−4–10−6 Pa resembled those of internal cracks; therefore, the presumably working vacuum environment around internal cracks was considered to be at a high vacuum level.

Autopolymerized poly(methyl methacrylate) reinforced with alumina nanoparticles

Background/Aim. Mechanical properties, most significantly flexural strength of cold polymerized acrylic dental materials, used for denture reparation are lower compared to the equivalent hot polymerized materials. This paradox can be rectified by the application of alumina nanoparticles, which was the aim of this work. Methods. The liquid component of the commercial autopolymerized denture reline resin was modified with 0.05%, 0.2% and 1.5% (wt) 13 nm hydrophobic Al2O3. These mixtures, along with the unmodified liquid, were mixed with the powder component to form test specimens. Flexural modulus and strength were tested, while the results were statistically evaluated by the oneway ANOVA analysis followed by Tukey?s test. Differential scanning calorimetry, scanning electron microscopy and energy dispersive X-ray analysis were performed to assess the heat and fracture surface features. Results. A statistically significant increase in flexural modulus was obtained only for 0.2% nanoparticle content, while flexural strength was significantly increased for specimens modified with 0.05% and 0.2% nanoparticles. Moreover, the rise of nanoparticle content to 1.5% contributed the formation of agglomerates, giving unsatisfactory mechanical properties. Also, the rise in glass transition temperature was noted for the most effective 0.05 and 0.2% Al2O3 contents. Conclusion. The 0.2% 13 nm Al2O3 loading is the most effective in improving the tested mechanical properties of cold polimerized poly(methyl methacrylate) reline resin.

Properties and Fracture Surface Features of Plaster Mold Reinforced with Short Polypropylene Fibers for Investment Casting

In this work, plaster molds for investment casting, reinforced with short polypropylene fibers, were prepared and their properties and fracture surface features were investigated. Fiber contents ranging from 0.10 to 0.50 wt% were introduced into a powder mixture of gypsum and mullite (ratio of 3:7) as reinforcements in order to prepare thin-walled plaster molds with high strength and permeability. The strength of green and fired plaster mold specimens was tested, the permeability was also tested, and their fracture surfaces were observed by scanning electron microscopy (SEM). The results show that the strength of the molds increases initially and then decreases with increasing fiber content. The green flexural strength of the specimens containing 0.20 wt% polypropylene fibers reached the maximum, c.a. 1.94 MPa, increased by 36.6%, and particularly, there was a slight increase in their fired strength, a maximum value of 0.45 MPa, in comparison with the fiber-free specimen. This low increase in the fired strength the reinforced specimen will produce a favorable effect on the collapsibility of shells in the casting cleaning process. In addition, the fired permeability of fiber-reinforced fired specimens exhibited significant enhancement, compared to that of the unreinforced ones. With increasing fiber content, the permeability of specimens increased from 8.6 to 11.5%. The improvement of green permeability was limited substantially. SEM observations indicate that the failure of the green specimens is a result of brittle fracture of the plaster substrate and/or fiber debonding from the matrix during loading. On the contrary, in fired specimens, the failure occurs by holes in the plaster substrate resulted from fiber ablation in the matrix during the firing process. The arrangement of polypropylene fibers can also affect the fracture behavior of molds. This proposed approach can reduce mold thickness without loss of strength and provide defined judgment basis for fracture features.

Numerical simulation to determine the fracture aperture in a typical basin of China

Fracture aperture is the main source of uncertainty in reservoir fracture modeling; this uncertainty is due to the difficulty of accurately quantifying underground fracture aperture and the limited understanding of the main factors controlling fracture aperture and the mechanical deformation process. The theoretical evaluation model of underground fracture aperture is a key aspect of fracture characterization and modeling of tight sandstone reservoirs. Based on the self-similarity theory of rock fractures and considering the 3D morphology of a fracture surface, a finite element geomechanical model of a fracture surface is established. A combination of physical experiments and numerical simulations is used to determine the fracture apertures in underground reservoir conditions. Furthermore, a theoretical model of fracture aperture is proposed under the constraints of the in situ stress, rock mechanics parameters, fracture occurrence, fracture scale, fracture filling characteristics and fracture surface characteristics. According to the vertical distribution model of in situ stress, the theoretical average fracture aperture in rock at different depths is determined. With increasing burial depth, the fracture aperture decreases. When the horizontal stress difference is greater than 10 MPa, the effect of the in situ stress difference on the average fracture aperture decreases. Among the three fracture filling patterns considered, the average effective aperture of fractures with uniform filling is the largest. When the fracture spacing is less than 2 m, the fracture aperture increases with increasing fracture spacing; when the fracture spacing is greater than 2 m, the fracture aperture is basically unaffected by the fracture spacing.

Characteristic of composite bioplastics from tapioca starch and sugarcane bagasse fiber: Effect of time duration of ultrasonication (Bath-Type)

Composite bioplastic is an alternative solution to solve the plastic waste problem in our environment. This is due to the composite bioplastic is one material that is environmentally friendly and easily degraded in nature. This study aims to make composite bioplastic from environmentally friendly materials, namely tapioca starch and sugarcane bagasse fiber (SBF). The addition of SBF into the tapioca matrix serves as a structural reinforcement of composites bioplastics. SBF was added by 1 wt% (from dry weight of starch basis) and kept constant for each variation of the sample. The fabrication of composite bioplastic using the solution casting method. The variation time duration of ultrasonication on composite bioplastic (tapioca starch and 1 wt% bagasse fiber) includes 0, 5, 10 and 15 min. Tensile testing, observation of fiber morphology, fracture surface characteristics, moisture absorption rate were carried out conducted by tensile test, scanning electron microscope (SEM), and moisture absorption test, respectively. The results show that the addition of ultrasonication increases the tensile strength of composite bioplastic samples. The highest tensile strength value was achieved by a sample with 15 min ultrasonication for 2.5 MPa. This result was supported by fracture morphology which shows a compact structure. In addition, the moisture absorption rate also decreases with increasing ultrasonication. Preparation and giving ultrasonication on composite bioplastic samples was highly recommended for improving the properties of the sample.

Bending behavior and fracture surface characters for FeSiB amorphous ribbons in different free volume state

The FeSiB amorphous ribbons with monolithic amorphous structure in different free volume state were prepared by annealing the as-cast ribbons at different temperature. The results show that a fairly large amount of free volume for S25 sample, the medium amount of free volume for S250 sample, and the free volume were almost annealed out in S380 sample, and the free volume has great influence on bending behavior and the resultant fracture surface. With the decrease of free volume, the amount of shear bands on the bent crease, bending strain decrease from 1 to 0, critical shear displacement on fracture surface decrease form 3.32 mm decline to ~ 203 nm. Meanwhile, the size of micro-scale vein pattern decreases, the size of nano-scale periodic corrugations increases. The bending strain, shear band density and fracture surface characteristics were discussed via free volume content and shear transform zone size.

Investigating the Meso‐Mechanical Anisotropy and Fracture Surface Roughness of Continental Shale

AbstractContinental shale is abundant with unconventional oil and gas and has considerable prospect for exploitation. However, due to deposited environment differences, continental shale presents unique characteristics in terms of structure and mineralogy compared to marine shale. The mechanical property is elemental parameter for reservoir production, but relevant studies of continental shale are rarely reported. In this study, several groups of mesoscale (0.1–10 mm) uniaxial compression tests were conducted on continental shale with various bedding angles, sourced from the Yanchang Formation in the southern Ordos Basin, China. A new integrated real‐time loading‐observation‐acquisition system, specifically, a miniature tensile instrument‐light microscope (MTI‐LM) system, was utilized, which allowed us to visualize the failure process and simultaneously record the stress‐strain curves, providing snapshots for investigation of fracture initiation, propagation, and fracture surface features. The results demonstrate that as the bedding angle relative to the maximum compression direction increases, the uniaxial compressive strength (σc) and the percentage of bedding‐parallel fractures (Fp) fluctuate reversely, namely, higher σc corresponds to lower Fp. Additionally, a good consistency is revealed among the variations of σc, failure time and fracture surface roughness with bedding angles, suggesting stronger shale having rougher fracture surfaces and longer failure time at a certain loading rate. The meso‐mechanical anisotropy of shales is supposed to have an origin in heterogeneous component and microtexture, as indicated by different bridges connecting the opposite facies of fractures. The findings help reveal the mechanism underlying mechanical anisotropy and facilitate fracability evaluation of shallow shale gas reservoir.

Studies on Stress Corrosion Cracking of Vit 105 Bulk Metallic Glass

The project “Stress Corrosion Cracking of Zr-based Bulk Metallic Glasses” (SCC of Zr-BMG) within PP1594 mainly dealt with mechanical-corrosive interactions and failure of this class of metastable materials. It focussed on one of the most application-relevant Zr-BMG, Vit(reloy) 105 with composition Zr52.5Cu17.9Ni14.6Al10Ti5 (at.-%). Even though this BMG is known as extraordinary glass former, the metallurgical processing is still a critical issue. In contrast to conventional processing, i.e. melting of master alloys from pure elements, a different route using binary pre-alloys for the master alloys production was applied and led to superior mechanical properties upon mechanical testing under tensile and 3-point-bending (3PB) conditions in air. As a reference and for a detailed understanding of failure, fracture and cracking of Zr-base BMG in air, notched specimen 3PB experiments with in-situ microscopic observation were done and the still controversial interpretation of the mechanical behaviour of BMG in the framework of fracture mechanics was addressed. The specimen from the in-situ 3PB-tests served for TEM investigations on the structural nature of shear bands in BMG on the atomistic scale. Altogether, complete crack paths could be observed and analysed and based on this, details of the shear-band driven crack growth are described. While in first SCC studies using a newly developed setup full cross section (3PB) bars were investigated, in recent in situ experiments notched specimen were tested in 0.01 M NaCl yielding strong evidence for a catastrophic failure due to hydrogen embrittlement (HE). The known susceptibility to pitting corrosion in halide containing environments is only the initial stage for failure under SCC conditions. Once pitting is initiated, the local electrode potential is severely reduced. Further, the hydrolysis reaction of oxidised Zr4+ to zirconyl ions ZrO2+ during local BMG dissolution produces H+ and thus, a local acidic environment that enables proton reduction and hydrogen absorption in the stressed BMG region. The peculiar failure and fracture surface characteristics as well as the proven local reduction of the pH value in the vicinity of the notch during in-situ experiments clearly account for the proposed HE-SCC failure mechanism.

A Fractographic Analysis of Additively Manufactured Ti6Al4V by Electron Beam Melting: Effects of Powder Reuse

Metal additive manufacturing (AM) is being rapidly adopted in the aerospace and biomedical industries. Powder bed fusion AM processes are leading this trend. To maximize process economy, excess “unmelted” powder retrieved from the build chamber is used in subsequent build cycles. The metal properties and component reliability could undergo degradation with powder reuse. This study investigates the effects of powder reuse on fracture surface characteristics of Ti6Al4V specimens fabricated by electron beam melting AM over 30 sequential build cycles. Optical microscopy and scanning electron microscopy were used to evaluate the changes in fracture surface features of tensile failures with powder reuse. Macroscopically, slant fractures were most common in early builds, which transitioned to orthogonal fracture surfaces with poorly defined shear lips with increasing reuse. Regardless of the build number, the fracture origins were consistently from the as-built surfaces. Microscopically, ductile features such as micro-void coalescence were evident throughout the 30 build cycles. However, increasing flute content with reuse suggests that rising oxygen levels causes solution strengthening and limits the participation of active slip systems. These results highlight the importance of surface roughness and powder oxidation to metal performance in AM, and the evolution of fractographic features with powder reuse.

Fatigue behaviour of an additively manufactured ductile gas turbine superalloy

Additive manufacturing (AM) offers new possibilities in gas turbine technology by allowing for more complex geometries. However, the fatigue performance, including crack initiation and crack propagation of AM gas turbine material, is not fully known. In addition, AM materials shows anisotropic properties due to the columnar grain growth in the building direction during the AM process, which needs to be accounted for. Also, an AM component often solidifies with a cellular dendritic structure during the manufacturing process. In the present study, the bulk material of an AM adopted nickel-based superalloy based on Hastelloy X was subjected to low-cycle fatigue (LCF) loading at room temperature. The LCF tests were conducted in strain control on additively manufactured smooth bars,with two different build orientations (with an angle of 0° and 90° relative to the building platform). The LCF results showed that the major part of the fatigue life is spent in the crack initiation phase, namely 78% to 99% of the total fatigue life. Based on the experiments, a model to predict the crack initiation life was developed that takes the anisotropic material behaviour into account. The last part of the fatigue life, the crack propagation phase, was studied on a microstructural level, where initial fractography of the ruptured LCF specimens revealed that the dendritic structure was visible on the fracture surface. It was noted that the dendritic structure could easily be mistaken for regular striations although they represent a different fracture mechanism. The fracture surfaces were therefore cross sectioned and possible correlations between fracture surface characteristics and underlying microstructure were studied using electron backscatter diffraction and electron channelling contrast imaging. The outcome showed that the dendritic structure had some effect on the LCF crack propagation behaviour by interdendritic tearing, which was discussed.

Experimental investigation on the anisotropic fractal characteristics of the rock fracture surface and its application on the fluid flow description

Based on the anisotropic fractal characteristics of natural fracture surfaces, a fractal fluid flow model was developed. Three-dimensional printed fracture models were built using the morphological information of an actual tensile and shear fracture surface of a rock. The impacts of the fractal dimension on the fluid flow characteristics were investigated. The results demonstrated that the concentration distribution of the undulating height of tensile fracture was larger than that of shear fracture. The fractal dimension of fracture lines with different directional sections ranges from 1.01 to 1.03, which results in the fluid flow anisotropy of fracture surfaces. As predicted by the theoretical model, the fluid flows along the tensile fracture surface and the shear fracture surface in different directions are 0.7–1.2 times and 0.9–1.1 times the average flow rates, respectively. With increasing pressure head, the Reynolds number linearly increased, and the Euler number first rapidly decreased and then slowly decreased.

Temperature-dependent plasticity and fracture mechanism under shear loading in metallic glass

The fracture surface morphology under shear loading is important for understanding the plasticity and the deformation mechanism of metallic glasses (MGs). However, it is difficult to carry out the shear fracture test for most MGs by conventional test methods due to their limited glass forming ability. In this work, through a unique anti-symmetrical four-point bend method, the shear fracture test is carried out under a quasi-static loading at a wide temperature range from 220 K (0.31Tg, Tg: glass transition temperature) to 620 K (0.88Tg) for a Zr-based MG. Basing on the examination on the fracture surface morphologies, we found three different fracture mechanisms with temperature: at lower temperatures (220 ~ 260 K, 0.31 ~ 0.37 Tg), both flower-like and shear-driven vein patterns appear on the fracture surface, which displays a mix of shear- and dilatation- dominated fracture; at intermediate temperatures (300 ~ 570 K, 0.42 ~ 0.80 Tg), the shear-driven vein patterns dominate on the fracture surface, indicating the shear-dominated fracture; at higher temperatures (600 ~ 620 K, >0.80 Tg), a mass of melt droplets indicate the transition from inhomogeneous to homogeneous deformation. From the Weibull statistical analysis on the main fracture features at intermediate temperatures, we found that the size of shear-driven vein patterns increases and the data distribution is sparser with the temperature increasing. The temperature dependence of fracture surface morphology as well as the relationship between the fracture surface feature and the microstructural evolution in MG were also interpreted from the shear transformation zone theory.

Shaping Ability, Cyclic Fatigue Resistance and Fractographic Analysis of Hybrid and Reciprocating Nickel Titanium Endodontic Instruments

The aim of this study was to investigate the shaping ability and cyclic fatigue resistance of Genius (GN) and WaveOne (WO) nickel-titanium (NiTi) instruments. Forty mesial root canals of mandibular molars were randomly divided into two groups, according to the instrument system used for root canal preparation (n = 20): GN and WO. Root canals were prepared to the full working length using the crown-down technique, with up to 40.04 instruments for GN group and 40.08 instruments for WO group. Specimens were scanned with a µCT before and after instrumentation. The changes in 3D parameters and degree of canal transportation were evaluated in the apical, middle and coronal thirds of root canals. Size 25, taper 0.04 (GN) and 0.08 (WO) instruments (n = 20) were used in simulated root canals until fracturing, and the number of cycles to failure (NCF) was recorded. The fractured files were investigated under a scanning electron microscope to characterize fractured surfaces. Data were analyzed using ANOVA post hoc Tuckey’s tests with the significance level set at 5%. The GN system was able to prepare the higher percentage of the canal surface with less canal transportation in all root canal thirds and displayed the higher resistance to cyclic fatigue in comparison to WO instruments (p < 0.05). However, the length of the fractured segments was not significantly different among the groups; meanwhile, SEM investigations revealed the typical topographic characteristics of fractured surfaces. Hybrid GN instruments demonstrated superior shaping ability and resistance to cyclic fatigue. However, both NiTi instrument systems prepared the root canals with no significant shaping errors, considerable changes in 3D parameters and no significant differences in the topographic appearances of the instrument surfaces after fractures.