Fracture Failure Mode Research Articles

Mechanical properties and failure mechanisms of all-CFRP corrugated sandwich truncated cone

Cone-shaped sandwich structures are extensively employed in various fields due to their excellent bearing efficiency and designability. In this work, the design approach and integrated manufacturing method for the carbon fiber reinforced plastic (CFRP) corrugated sandwich truncated cone (CSTC) are proposed to improve the anti-debonding ability and ensure the reliability of the sandwich cone. First, the theoretical model for the stiffness of the CSTC is derived, in which the conservative prediction and the upper limit considering the fiber orientation of the cone are derived. The multiple failure modes of the CSTC under axial compression are theoretically established. Then, the failure mechanism map of the CSTC is established to forecast the possible failure modes. The typical failure modes of local buckling, face fracture, and core buckling are captured by experiments and finite element analysis (FEA). The theoretical model of the stiffness and failure modes is verified by the experiments and FEA. The effect of the semi-vertex angle and circumferential cell number on the failure modes is revealed. Furthermore, a more comprehensive failure mechanism map is generated by altering the geometric parameters of the CSTC. The failure modes of Euler buckling and global buckling are acquired by the comprehensive failure mechanism map and verified by FEA. Finally, the optimum design of the CSTC structure is performed. The results show that the failure mode of face fracture has the best bearing efficiency. This research provides a solid foundation for designing and applying lightweight CSTCs in constructions, such as the adapter of launch vehicles.

In situ characterization of thermomechanically loaded solution strengthened, nanocrystalline nickel alloys

Nanocrystalline (NC) Ni-40Cu and Ni-40Cu-0.6P (at.%) alloys were mechanically loaded in tension at ambient (23 °C) and elevated (150 °C) temperatures with the deformed nanostructure captured by in situ transmission electron microscopy coupled with digital image correlation for data mining high strain regions prior to catastrophic failure. The addition of the P provided grain boundary partitioning that stabilized the NC structure under both loading cases, which was not found to be the case for the binary alloy. While mechanical strength softening was observed in each of the alloys upon thermomechanical loading, the retention of strength was substantially higher in the ternary alloy than its binary counterpart. Digital image correlation was found to be a useful means for image mining to identify different regions where failure mechanisms were initiated. Intergranular failure was observed as the dominant failure mechanism in all specimens with the binary alloy revealing a coarser fracture profile as compared to a finer fracture profile in the ternary alloy. Atomistic simulations are used to understand P solute strengthening of the grain boundaries against this fracture failure mode.

Simulation of solutions to protect reinforced concrete structures under

The paper aim to assess the fracture failure mode of reinforced concrete components under contact blast loading using both on site experiment and numerical simulation. From there, we propose a solution to protect reinforced concrete components under explosive load contact. Based on the results, the selection of computational models, constitutive laws of the material in the simulation of the structure under the impact of blast loading in the ABAQUS program has been evaluated.

Ice breaking by low-velocity impact with a rigid sphere

Penetrator–ice plate impact subjected to dynamic loading constitutes many scientific applications for ice, such as controlling ice disasters by penetrating the ice cover and then entering underwater to explosive ice breaking on Earth, and life detection and resource development under water ice sheet on outer space planets. We present experimental results of brittle damage induced by a small spherical projectile impacting an ice plate with a thickness of 6–50 mm using a drop ball test device or a vertical gas gun. The corresponding impact velocities vary from 2 to 74 m/s. Crater parameters, residual velocity and energy absorption are investigated and assessed. The main fracture patterns and crater formation are captured by two high-speed cameras. A dynamic recrystallization phenomenon of polycrystalline ice is observed, and its formation mechanism is preliminarily analysed. The effects of the impact velocity, ice sample thickness, and restriction conditions on dynamic fracture processes and failure modes are systematically explored. These results improve our understanding of dynamic fracturing mechanism in ice engineering applications.

Fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: Cervical margin relocation and crown lengthening with complete and partial ferrule with three different post and core systems.

To assess the fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: cervical margin relocation (CMR) and crown lengthening (CL) with complete ferrule (CLF) and partial ferrule (CLPF) with three different post and core systems. In this in vitro study, 100 maxillary premolars were assigned to the following 10 groups according to their preparation approach and type of post and core system (n = 10): (I) control (intact teeth), (II) prefabricated fiber post (PFP) and composite core with CMR (PFP-CMR), (III) polyethylene fiber-reinforced composite (PEFRC) with CMR (PEFRC-CMR), (IV) casting post (CP) and core with CMR (CP-CMR), (V) PFP-CLPF, (VI) PEFRC-CLPF, (VII) CP-CLPF, (VIII) PFP-CLF, (IX) PEFRC-CLF, and (X) CP-CLF. After thermomechanical loading, the fracture resistance and failure mode were assessed. Data were analyzed statistically (α = 0.05). In all post and core systems, the CLPF approach had lower fracture resistance than CMR (p<0.05); CLF showed higher fracture resistance than CLPF only in the PFP system (p = 0.038). In PEFRC and CP systems, the difference between CLF and CLPF was not significant (p > 0.05). No significant difference was found in fracture resistance of different post and core systems with the same preparation approach (p > 0.05). CLPF showed the highest frequency of favorable, and CLF showed the highest frequency of unfavorable fractures. CLPF yielded lower fracture resistance than CMR. The difference in fracture resistance was not significant between CLF and CMR but the frequency of unfavorable fractures was higher in CLF than in other groups.

High-velocity impact damage and compression after impact behavior of carbon fiber composite laminates: Experimental study

In this paper, the impact resistance of carbon fiber/resin composite laminates with a thickness of 2.5 mm at different impact velocities, angles and positions was investigated experimentally. In the process of high-velocity impact, fiber shear failure and tension failure are the main failure modes. When the impact velocity is 300 m/s, the fiber tension failure and matrix compression failure under oblique impact are more than that under normal impact, and the energy absorption of laminates is also lager than that under normal impact. The ballistic limits, energy absorption and delamination area of the center and edge impact of laminate are similar. In addition, the CAI tests are conducted to study the influence of different positions on the residual compressive strength of laminates after high-velocity impact, and the fracture loads and failure modes of two impact positions are quite different. The failure modes of the center impact laminate are main buckling failure, and the failure modes of the edge impact laminate are compression failure near the bullet hole side of the fixture and buckling failure near the center of the laminate. The research results can provide a reference for the residual strength of laminates after impact at different locations in practical situations.

Comparison of the effects of femtosecond and nanosecond laser tailoring on the bonding performance of the heterojunction between PEEK/CFRP and Al–Li alloy

In this paper, an ultrafast femtosecond laser was used to tailor the surface of the PEEK/CFRP (carbon fiber reinforced plastics with polyether ether ketone as resin matrix), using a nanosecond laser as a contrast. By analyzing the effect of femtosecond and nanosecond laser tailoring on the surface morphology, surface chemical composition and wettability of PEEK/CFRP, the internal reasons for the improved of bonding performance of heterojunction between PEEK/CFRP and Al–Li alloy by laser pretreatment were explored. As a result, the shear strength increased considerably from 4.9 MPa to 16.1 MPa and 29.5 MPa after nanosecond laser and femtosecond laser pretreatment, respectively. Finally, the fracture surface and failure modes of heterojunction bonded joints were compared, and the different mechanisms of femtosecond and nanosecond laser tailoring PEEK/CFRP surface were explained. Femtosecond laser tailoring is a competitive process for improving the bonding properties of the heterojunction between PEEK/CFRP and Al–Li alloys because of its productivity, controllability and lack of pollution.

Fracture strength and bonding interface morphology of CAD/CAM-fabricated ceramic laminate veneers on bleached enamel treated with two different antioxidants.

This study aimed to investigate the effects of two antioxidants and their application time on the fracture strength of computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated ceramic laminate veneers to bleached enamel, as well as their effects on the bonding interface micromorphology. Eight groups were set: Group NC (without bleaching and antioxidant treatment); Group NA (bleaching without antioxidant treatment); Group SA30, SA60, SA120 and Group PAC30, PAC60, PAC120 (bleaching and treating with sodium ascorbate or proanthocyanidins for 30, 60, and 120 min, respectively). After cementation of veneers, fracture strength values and failure modes were analyzed. The bonding interface morphology was observed by confocal laser scanning microscopy. The fracture strength was impaired when cementation procedure was performed immediately after bleaching. This reduction in fracture strength was reestablished with antioxidant treatment, and an extended treatment time contributed to better improvement. The resin tags at the bonding interfaces of the bleached enamel were impaired. Antioxidant treatments were able to reverse this unfavorable trend.

Effect of Zn on Phase Evolution and Shear Resistance of Stainless Steel and Aluminum Alloy Interface by Laser Cladding

The connection between aluminum and iron alloys is of immense significance in the pursuit of lightweight industrial products. However, the Fe-Al interface’s inherent weakness restricts its widespread application. This study investigates the impact of Zn at the interface of Al-Fe laser cladding on the phase and mechanical properties of the interface. Specifically, we examine the influence of the applied Zn powder layer and alloying Zn layer on the morphology of the Fe-based cladding layer. The inclusion of Zn enhances the spreadability of the Fe-based cladding layer. Additionally, we elucidate the effect of Zn on the composition and phase of the Fe-Al laser cladding interface. Notably, the affinity between Zn and the η phase surpasses that of the θ phase, and an increased Zn content significantly thickens the η phase. Shear tests reveal that the failure mode of shear fracture encompasses both brittle and ductile fractures. Density functional theory (DFT) calculations indicate that Zn has a limited effect on the strength of the η phase but reduces the enthalpy of formation of the η phase. Our findings demonstrate that the alloyed Zn layer initially facilitates the formation of a continuous and uniform η layer, while an increased Zn content enhances and stabilizes the shear strength of the interface.

How can machine learning be used for accurate representations and predictions of fracture nucleation in zirconium alloys with hydride populations?

Zirconium alloys are critical material components of systems subjected to harsh environments such as high temperatures, irradiation, and corrosion. When exposed to water in high temperature environments, these alloys can thermo-mechanically degrade by forming hydrides that have a crystalline structure that is different from that of zirconium. Cracks can nucleate near these hydrides; hence, these hydrides are a direct link to fracture failure and overall large inelastic strain deformation modes. To fundamentally understand and predict these microstructural failure modes, we interrogated a finite-element database that was deterministically tailored and generated for large strain-dislocation-density crystalline plasticity and fracture modes. A database of 210 simulations was created to randomly sample from a group of microstructural fingerprints that encompass hydride volume fraction, hydride orientation, grain orientation, hydride length, and hydride spacing for a hydride that is physically representative of an aggregate of a hydride population. Machine learning approaches were then used to understand, identify, and characterize the dominant microstructural mechanisms and characteristics. We first used fat-tailed Cauchy distributions to determine the extreme events. A multilayer perceptron was used to learn the mechanistic characteristics of the material response to predefined strain levels and accurately determine the critical fracture stress response and the accumulated shear slips in critical regions. The predictions indicate that hydride volume fraction, a population-level parameter, had a significant effect on localized parameters, such as fracture stress distribution regions, and on the accumulated immobile dislocation densities both within the face centered cubic hydrides and the hexagonal cubic packed h.c.p. matrix.

Experimental study on fracture damage and seismic performance of loose through-tenon joints in ancient timber structures

A looseness is typical damage of mortise-tenon joints in ancient timber structures. Brittle fractures of loose joints are likely to occur, leading to joint failure during earthquakes. This study conducts pseudo-static tests on three groups of full-scaled through-tenon joints to examine the fracture damage and seismic behavior of the loose mortise-tenon joints and determines fracture damage modes of through-tenon joints with different looseness. It uses the acoustic emission method to measure the ring count on the tenon surface, along with each joint's critical load and critical energy release rate and then analyzes the fracture damage performance of different tenon joints. In addition, this research investigates the hysteretic and skeleton curve, stiffness degradation curve, and tenon pulling quantity of the joint under various fracture damage states. The results showed that the fracture failure mode of the through-tenon joint is a fracture in the variable cross-section and along the local tenon neck. During the loading process, the critical energy release rate initially increases and then decreases as the looseness grows. In addition, with the increase of crack mouth opening displacement (CMOD) and crack length, the bending moment of the joint firstly increases and then decreases. When the variable cross-section breaks and the tenon neck partially cracks, the joints' bending moment and stiffness reduce with increasing looseness. With the increase in local embedment compression in the lower side of the beam end and the mortise, the amount of tenon pull-out of loose joints decreases under positive and negative loading.

Hybrid phase-field modeling of mesoscopic failure in concrete combined with Fourier-Voronoi stochastic aggregate distribution modelling approach

Concrete crack propagation is significantly affected by its complex mesoscopic structure, tracking which is of great importance for revealing the fracture failure modes and crack propagation patterns of concrete. This study presents a stochastic aggregate distribution modeling approach combining the Fourier-Voronoi method and techniques with XCT images. it enables the generation of stochastic aggregate distribution models that mimic real concrete's morphological characteristics. Meanwhile, with the hybrid phase-field theory and finite element method, a multi-field coupling model is established to simulate the crack propagation. In contrast to the isotropic or anisotropic phase-field theory, with the hybrid phase-field theory the stiffness degradation of concrete material in all directions during crack propagation are taken into consideration. With the proposed methodology, the effects of volume fraction, shape, roughness and pre-notch depth on the fracture behavior and strength of concrete are investigated. Results show that both the tensile and shear strength of concrete grows with the increase of aggregate volume fraction. Benefited from the application of hybrid phase-field theory, two shear fracture failure modes of concrete with distinct shear strengths are revealed, influenced by aggregate interaction during the shear fracture process.

Fracture strength and failure mechanism of graphene-containing grain boundaries and pores

Grain boundaries and pores commonly manifest in graphene sheets during experimental preparation. Additionally, pores have been intentionally incorporated into graphene to fulfill specific functions for various applications. However, how does the simultaneous presence of pores and grain boundaries impact the mechanical properties of graphene? This paper establishes uniaxial tension models of single-layer graphene-containing pores and three types of experimentally observed. The effect of interaction between pores and grain boundaries on the fracture strength of graphene was studied respectively for three types of grain boundaries by employing molecular dynamics simulations and considering factors such as pore size, the distance between pores and grain boundaries, and loading angle. A competitive mechanism between the intrinsic strength of pristine graphene with grain boundaries (referred to as pristine GGBs), which varies with the loading angle and the fracture strength of graphene sheets with pores that changes with the size of the pores, governs the fracture strength and failure modes of GGBs with pores. When the former exceeds the latter, the fracture strength of GGBs with pores primarily depends on the size of the pores, and fractures occur at the edges of the pores. Conversely, when the former is lower, the fracture strength of GGBs with pores relies on the loading angle and the distance between pores and grain boundaries, leading to grain boundary rupture. If the two strengths are comparable, the failure modes are influenced by the distance between pores and grain boundaries as well as the loading angle. The findings further elucidate the impact of coexisting grain boundaries and pores on the fracture behavior of graphene, providing valuable guidance for the precise design of graphene-based devices in the future.

Fracture load and failure mode of semi-direct resin composite occlusal veneers: Influence of design and mechanical cycling

AimsTo evaluate the influence of the type of preparation and mechanical cycling on the fracture load and failure mode of semi-direct posterior resin composite restorations. MethodsIn total, 70 healthy third molars were used; 10 belonging to the control group (C - unprepared teeth) and 60 teeth prepared and restored with nanoparticle resin composite, divided into 3 groups (n = 20): O - exclusively occlusal preparation (Table Top); OV - occlusal preparation with buccal extension (Veneerlay); OVP - Occlusal preparation with chamfer on the proximal and buccal-lingual/palatal surfaces (Overlay). The preparations were performed with diamond burs with a thickness of 1 mm. The restorations were made with nanoparticulate resin composite (Filtek Z350 XT) and subsequently received additional polymerization (thermoprocessing). Cementation was performed with the use of universal adhesive system (Single Bond Universal) on dental substrate and dual resin cement (RelyX ARC). Half of the teeth in each group (n = 10) were submitted to mechanical cycling, simulating 6 months of clinical service (5 × 105 fatigue cycles), under dynamic loading of 130 N, at a frequency of 2Hz. Fracture load tests were performed in a universal testing machine with a 200 kgf load cell. Failure mode was classified using scores. Generalized linear models and Fisher Exact tests were applied to the data (significance level of 5%). ResultsThere were no significant differences between the types of preparation (p = 0.9435), or relative to cycling (p = 0.3764). The Fisher Exact Test showed a significant association between the groups and the type of failure (p = 0.0006), with preparations O (with cycling) and OVP (with and without cycling) exhibiting most failures with restoration fractures without involvement of the dental remnant. ConclusionsSemi-direct restorations showed resistance to fracture load similar to that of healthy teeth and were capable of withstanding functional masticatory loads. The type of preparation influenced the failure mode of teeth. The Table Top and Overlay types of preparations were those had fewer catastrophic failures, suggesting that since they are more conservative preparations, they made it possible for the tooth to receive a new restorative procedure in the future in cases of failures.

Screw Retained Implant Supported Zirconia Anterior Fixed Dental Prosthesis with Different Abutment Angulations: Evaluation of Fracture Resistance and Failure Modes

Screw Retained Implant Supported Zirconia Anterior Fixed Dental Prosthesis with Different Abutment Angulations: Evaluation of Fracture Resistance and Failure Modes

Investigation on structural failure of filament reinforced barrel containment

During the launching process of a composite railgun, some working conditions may lead to the structure failure of its filament reinforced barrel. For instance, the instantaneous electric power impact caused by the unexpected large pulse current and surge from the pulse-forming network, which inspires the electrodynamic response beyond the safety limit of the barrel. More importantly, the alternating load after a long-term working causes damage accumulation and failure in the composite structure. For the railgun, considering that the radial deformation of the barrel has special effect on the contact state of the rail and armature in bore, it is necessary to focus on whether the radial stiffness of the barrel is affected even if the strength of the barrel does not decrease significantly by hidden injuries in the fiber wraps. In this study, based on the common used method of progressive failure theory, the radial stiffness attenuation process of the barrel is analyzed. The fiber fracture and composite delamination failure modes are found to be the main factors for radial stiffness attenuation of railgun barrel containment as persistent deformation will generate after these damage propagation. In addition, the loss of prestress in the fiber containment is evaluated based on structural analysis for the barrel in service and in manufacturing time. The research has found that optimized preloading seems important for improving the strength performance of the barrel.

In Situ Tensile Observation of the Effect of Annealing on Fracture Behavior of Laser Additive Manufactured Titanium Alloy.

The use safety of laser additive manufactured (LAM) titanium alloys is closely related to each one's fracture failure mode. In this study, in situ tensile tests were carried out to study the deformation and fracture mechanisms of LAM Ti6Al4V titanium alloy before and after annealing treatment. The results showed that plastic deformation promoted slip bands to occur inside the α phase and shear bands to generate along the α/β interface. In the as-built sample, cracks initiated in the equiaxed grains and propagated along the columnar grain boundary, showing a mixed fracture mode. However, it transformed into a transgranular fracture after annealing treatment. The widmanstatten α phase acted as a barrier for slip movement and improved the crack resistance of grain boundaries.

Fracture strength of anterior cantilever resin-bonded fixed partial dentures fabricated from high translucency zirconia with different intaglio surface treatments.

To compare the fracture resistance and failure modes of anterior cantilever resin-bonded fixed partial dentures (RBFPDs) fabricated from high translucency zirconia with different intaglio surface treatments. Sound-extracted canines (N=50) were randomly divided into five groups (n=10) to be restored with high translucency zirconia RBFBDs of different intaglio surface treatments. The RBFPD was designed using exocad software and fabricated using a CAM milling machine. The RBFPDs were treated differently: abrasion with 50µm alumina particles (Group 1); abrasion with 30µm silica-coated alumina particles (Group 2); abrasion with silica-coated alumina particles (30µm) and silane application (Group 3); abrasion with silica-coated alumina particles (30µm) and 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) primer application (Group 4); abrasion with silica-coated alumina particles (30µm) and silane, and 10-MDP primer application. All RBFPDs were cemented using dual-cured resin cement. The RBFPDs underwent 6000 thermal cycles with distilled water at 5/55°C for 2min per cycle and then mechanical cyclic loading with 1200,000 cycles of 50N at a 1.7Hz frequency at an angle of 135° to the abutment's long axis. Then, RBFPDs were loaded to fracture using a universal testing machine at 1mm/min. Maximum fracture forces and failure modes were recorded. Fractured specimens and uncemented specimens were examined using a scanning electron microscope. Data was analyzed using ANOVA and Games-Howell post hoc tests at p<0.05. Mean fracture load results showed a statistically significant difference between the research groups (p<0.0001) and it ranged from 69.78 to 584N. Group 4 exhibited the highest fracture load mean (p<0.0001) which was significantly different from all other groups. Group 2 recorded a significantly higher fracture load mean than Group 3 (p=0.029). Three modes of failure were observed: prosthesis debonding, prosthesis fracture, and abutment fracture. Abrasion of zirconia surface with 30µm silica-coated alumina particles and application of 10-MDP primer yielded the highest mean fracture loads of monolithic high translucency zirconia RBFPD. The mode of fracture of the RBFPDs was influenced by the type of surface treatments.

Comparative evaluation of fracture resistance and failure modes in endodontically treated molars restored with zirconia endocrown and onlays

Developments in dental materials, CAD/CAM technologies and adhesive dentistry have improved the application of conservative restorations such as endocrowns and onlays. Among ceramics, zirconia has properties such as high strength, transformation toughening, chemical and structural durability, and biocompatibility, which enable zirconia to be used in the posterior area. This study is a comparative evaluation of fracture resistance and failure modes in endodontically treated molars restored with zirconia endocrown and onlays. This study was performed on 20 human mandibular first molars with similar dimensions. After root canal treatment, the samples were divided into two groups: endocrowns and onlays (n=10). Restorations were made using a CAD-CAM milling machine with zirconia CAD blocks and, after cementation, subjected to 10,000 thermocycling and 500,000 fatigue cycle procedures, respectively. Each specimen was placed on a Universal Testing Machine and subjected to axial compressive force applied at a crosshead speed of 0.5 mm/min. The mean loads of failure of each group were statistically compared using the Student t-test. Chi-square tests were used to compare frequencies of failure modes among groups. Fracture resistance showed a statistically significant difference between endocrown (5374.6810±670.03445 N) and onlay (3312.5000±804.01428 N) (p<0.001). No statistically significant difference was detected in the distribution of failure types among the groups (p>0.05). The fracture resistance of endocrown is substantially higher than that of onlay, and failure type does not differ in both restorations. Zirconia is a reliable material to use in conservative restorations.

Stronger than Ever: Multifilament Fiberglass Posts Boost Maxillary Premolar Fracture Resistance.

This paper investigates the influence of cavity configuration and post-endodontic restoration on the fracture resistance, failure mode and stress distribution of premolars by using a method of fracture failure test and finite elements analysis (FEA) coupled to Weibull analysis (WA). One hundred premolars were divided into one control group (Gcontr) (n = 10) and three experimental groups, according to the post-endodontic restoration (n = 30), G1, restored using composite, G2, restored using single fiber post and G3, restored using multifilament fiberglass posts (m-FGP) without post-space preparation. Each experimental group was divided into three subgroups according to the type of coronal cavity configuration (n = 10): G1O, G2O, and G3O with occlusal (O) cavity configuration; G1MO, G2MO, and G3MO with mesio-occlusal (MO); and G1MOD, G2MOD, and G3MOD with mesio-occluso-distal (MOD). After thermomechanical aging, all the specimens were tested under compression load, and failure mode was determined. FEA and WA supplemented destructive tests. Data were statistically analyzed. Irrespective of residual tooth substance, G1 and G2 exhibited lower fracture resistance than Gcontr (p < 0.05), whereas G3 showed no difference compared to Gcontr (p > 0.05). Regarding the type of restoration, no difference was highlighted between G1O and G2O, G1MO and G2MO, or G1MOD and G2MOD (p > 0.05), whereas G3O, G3MO, and G3MOD exhibit higher fracture resistance (p < 0.05) than G1O and G2O, G1MO and G2MO, and G1MOD and G2MOD, respectively. Regarding cavity configuration: in G1 and G2, G1O and G2O exhibited higher fracture resistance than G1MOD and G2MOD, respectively (p < 0.05). In G3, there was no difference among G3O, G3MO and G3MOD (p > 0.05). No difference was found among the different groups and subgroups regarding the failure mode. After aging, premolars restored with multifilament fiberglass posts demonstrated fracture resistance values comparable to those of an intact tooth, irrespective of the different type of cavity configuration.