Fracture Behavior Research Articles

Enhancement fracture behavior of sustainable cementitious composites using synergy between fly ash (FA) and nanosilica (NS) in the assessment based on digital image processing procedure

The present study has investigated the strength properties and fracture toughness of concrete composites reinforced 5 % nanosilica (NS) by adding different contents of fly ash (FA), i.e.: 0 %, 15 % and 25 %. The evaluated fracture toughness, under three-point flexural loads, were critical stress intensity factor (KIcS) and critical crack tip opening displacement (CTODc). Digital image processing procedure was used in this studies. It was stated that both the 5 % addition of NS and the total share of the nanomodifier with FA grains in the composition of the concrete mix significantly improve the strength properties of concretes, as well as their fracture toughness under first model of cracking in linear and non-linear terms. Moreover, it was observed that in concrete containing only NS the fracture process was clearly delayed and relatively short, whereas crack patterns in this composite were almost perfectly straight with significant crack width. On the other hand, in concretes icorporating NS + FA crack patterns were strongly curved (frequently with branching) with few microcracks in the vicinity of the main cracks. Concretes including FA and NS can be used in the execution of specific types of reinforced concrete structures subjected to fatigue or dynamic loads, e.g. bridge structures or industrial buildings.

Fracture behavior of composite piezoelectric intelligent structures formed by pasting MFC based on serial multi-scale method

The composite piezoelectric intelligent structures formed by combining piezoelectric materials with composite materials can achieve state perception and deformation control of the structure. Based on the molecular dynamics method, the continuum finite element method and the cohesive force model, the serial multi-scale research on the bonded composite piezoelectric intelligent structure was carried out from the micro, meso and macro scales. Molecular models of adhesive, macro fiber composite (MFC) surface and composite surface were established. The effects of temperature and pressure on the surface interaction energy of adhesive/MFC and adhesive/composite materials were analyzed. The traction-separation (T-S) relationship of cohesive region was obtained by virtual stretching method. Combined with the microscopic observation of the mesoscopic adhesive layer, the representative volume element (RVE) model of the mesoscopic adhesive layer considering the bubble defect was established, and the cohesive relationship curve of the adhesive layer was obtained. A double cantilever beam (DCB) macro finite element model was established to simulate the crack propagation behavior of the adhesive layer, and compared with the experimental results.

Age and crack length effects on fracture parameters of dam gallery concrete: Experimental investigation and modeling

Cracks of varying lengths may occur in galleries throughout dam construction, operation, and management processes. This study investigates the influence of age and crack length on the fracture parameters of gallery concrete, which is crucial for understanding the mechanisms and risks associated with gallery cracking and for developing appropriate treatment measures. Wedge-splitting tests were performed on gallery concrete specimens with varying crack lengths and at different ages. It was found that the fracture parameters measured at different ages all decrease with the increase of crack length. Based on the test results, size-independent material constants such as fracture toughness and the effective length of the fracture process zone were derived and modeled using an exponential function to reflect their time-varying characteristics. A fracture model was proposed and validated, which can accurately predict the fracture behavior of gallery concrete across varying ages and crack lengths, and is applicable in practical dam gallery crack analysis for assessing crack stability and evaluating the effectiveness of treatment measures.

Ceramic-metal pipes with NiAl2O4 and TiAl2O5 spinel phases with different metallic phase content - Analysis of properties, and microstructure, taking into account LCA

The article describes the formation of samples into pipes with NiAl2O4 and TiAl2O5 spinel phases with different metallic phase content. The centrifugal slip casting method was used to form the composites. All suspensions used were shear thinning and were characterized by slight thixotropy. The analysis of the phase composition and chemical composition showed the presence of Al2O3, TiAl2O5 and NiAl2O4 in the produced samples. The produced materials were characterized by brittle fracture behaviour. The obtained life cycle assessment results clearly showed that as the content of the metallic phase increases, the environmental footprint of sinters in the A1 phase increases, which is a direct consequence of the increased use of raw materials.

Fracture mechanical properties of sandstone with pre-fabricated cracks under freeze–thaw cycles

This paper evaluates the effect of freeze–thaw (F-T) cycles on the fracture mechanical properties of rocks with pre-fabricated cracks through experimental and numerical simulation. Three-point bending tests are conducted to determine the fracture characteristics of cyan sandstone with varying pre-fabricated crack heights. Subsequently, the failure characteristics of cyan sandstone with pre-fabricated cracks under F-T cycles are examined. A numerical model using parallel bond modeling (PBM) is established and validated against experimental results to further investigate the fracture behavior of sandstones with pre-fabricated cracks. Results demonstrate that both axial peak force and fracture toughness (KIC) linearly decrease with increasing freeze–thaw (F-T) cycles, and the axial peak force reduces with the rise in pre-fabricated crack height (Hc). The deformation damage process is categorized into four stages: compression-density, elastic deformation, pre-peak destabilization, and post-peak destabilization damage. Energy evolution is closely tied to microcrack initiation and propagation, with the majority of energy dissipating as microcrack surface energy. Both strain energy and dissipation energy decrease linearly with increased F-T cycles. These findings offer valuable insights for investigating the fracture mechanism of fractured rock mass in cold regions.

Effects of h-BN content and heat treatment temperature on the tribological behavior and toughness of laser-clad Mo2FeB2/WC/h-BN coatings

In this study, h-BN-modified Mo2FeB2/WC composite coatings were fabricated via laser cladding. The Mo2FeB2/WC/10 wt% h-BN composite coatings were heat-treated at 400, 600, and 800 °C. The microstructure, microhardness, tribological properties, residual stress, fracture toughness and fracture morphology of the coatings were investigated. The results showed that h-BN addition combined with heat treatment promoted the distribution of elements and finer microstructure. The Mo2FeB2/WC/10 wt% h-BN coating heat-treated at 600 °C showed the highest microhardness (1416.8 HV0.5) among the prepared coatings. The pristine and 600 °C heat-treated Mo2FeB2/WC/10 wt% h-BN coating showed excellent wear rates (1.97 and 1.84 × 10−5 mm3/Nm, respectively). The composite coatings modified with h-BN exhibited an abrasive wear mechanism after heat treatment. As the h-BN content and heat treatment temperature increased, there was a notable decrease in residual stress. Specifically, the coating subjected to heat treatment at 800 °C demonstrated the lowest residual tensile stress recorded at 168 MPa. Conversely, when heat-treated at 600 °C, the coating exhibited an optimal fracture toughness of 14.96 MPa⋅m1/2, with fracture behavior consistent with typical brittle fracture characteristics.

Numerical investigation on the mechanical and fracture behaviors of marble under cyclic loading and unloading true triaxial compression using discrete element method

Numerical investigation on the mechanical and fracture behaviors of marble under cyclic loading and unloading true triaxial compression using discrete element method

Study on the Effect of Filling on the Properties and Fracture Behavior of Gabbro with En-echelon Joints

Study on the Effect of Filling on the Properties and Fracture Behavior of Gabbro with En-echelon Joints

Study on the fracture behavior in clayey geomaterials under moisture diffusion by phase field modeling

Clayey geomaterials are prone to cracking under changing moisture conditions, which substantially compromises their engineering properties. When moisture intrusion and boundary constraints act in tandem on geomaterials, the relevance of multi-physics field processes to complex cracking phenomena remains underexplored. To provide deeper insight into the effect of moisture transport on the cracking behavior of clayey geomaterials, a theoretical model for moisture-induced fracture is proposed. The model combines moisture diffusion, volume deformation dependent on moisture conditions, and phase field fracture, and is solved using the finite element method with a user-defined element subroutine. The developed subroutine is applied to simulate soil desiccation experiments and mudstone water absorption tests. The results reveal that moisture gradients induce non-uniform expansion or shrinkage within the clayey geomaterials. The neighboring geomaterial particles mutually constrain these deformations, resulting in an internal stress field that serves as the primary cause of cracking. Stability and sensitivity analyses validate the reliability of the numerical framework. The proposed model can effectively simulate crack initiation, extension, and convergence during humidification or desiccation processes in both two and three dimensions. This study charts a feasible path for numerical simulation and mechanical mechanism exploration of cracking behaviors in clayey geomaterials during water migration.

Compressive Fracture Behavior of Zirconia/Resin Composites Prepared by Fused Deposition Modeling Combined with Vacuum Infiltration.

Although bioceramic materials exhibit good biocompatibilities and bone conductivities, their high brittleness and low toughness properties limit their applications. Zirconia (ZrO2)/resin composites with idealized structures and properties were prepared by fused deposition modeling (FDM) combined with a vacuum infiltration process. The porous structure was prepared using the FDM three-dimensional printing technology, with granular zirconia as the raw material, and the relationship between the pore shape, pore size, and deformation was discussed. The results showed that square pores were more suitable than honeycomb pores for printing small pore sizes, and the resolution was high. Scanning electron microscopy observations showed that the superposition of multiple printing paths promoted the emergence of hole defects. The effects of the resin and the pore shape on the compressive strengths of the composites were studied. It was found that the compressive strengths of the honeycomb pore ZrO2/resin composites and porous ceramics were superior to those of the square pore samples. The introduction of the resin had a significant effect on the compressive strengths of the composites. The compressive strength increased in the direction perpendicular to the pores, while it decreased in the direction parallel to the pores.

Investigation on fracture behavior of sandstone with multiple grain sizes at different strain rates based on acoustic emission spatial localization

Investigation on fracture behavior of sandstone with multiple grain sizes at different strain rates based on acoustic emission spatial localization

High strength diffusion bonding of Ti2AlNb to GH4169 with (TiZrHfNb)95Al5 high entropy interlayer

A high entropy interlayer (TiZrHfNb)95Al5 was designed for vacuum diffusion bonding of Ti2AlNb to GH4169. The influence of bonding temperature on the interfacial microstructure morphology, mechanical properties and fracture behaviour of the resultant joints was investigated. The evolution of microstructure and fracture mechanism were revealed. The typical interface microstructure of Ti2AlNb/B2/Solid solution/(Ti, Zr, Hf)2(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb)2+Solid solution/(Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe)ss/(Cr, Ni, Fe)ss/Cr-rich(Cr, Ni, Fe)ss/Ni-rich(Cr, Ni, Fe)ss/GH4169 was formed. As the bonding temperature increased, the thickness of interfacial reaction layer gradually increased, and the shear strength gradually increased until 980 °C, then decreased sharply. The highest shear strength reached 376 MPa at 980 °C for 90 min. The highest microhardness region of 11.79 GPa existed on the GH4169 side, which was mainly composed of (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe)ss phases. Meanwhile, the elastic modulus dramatically changed interface formed near this region. The fracture surface morphology indicated typical brittle fracture characteristics such as cleavage steps, transgranular fracture and intergranular fracture. According to the fracture analyses, major cracks initiated in the (Ti, Zr, Hf)(Ni, Nb) phase+(Ti, Zr, Hf)2(Ni, Nb) phase and gradually extended to the (Cr, Ni, Fe)ss phase. Thus, the major crack emerged region was located at the elastic modulus dramatically changed interface.

Crack-insensitive fracture of elastomer-based soft network materials under monotonic and cyclic loads

In various applications of stretchable electronics and soft robots, soft materials are subjected to long-term load-bearing conditions, requiring them to possess good extreme mechanical properties such as highly stretchable, strong, fracture-resistant and anti-fatigue. Conventional soft materials with a single polymer network typically exhibit relatively low fracture resistance, while commonly employed toughening method involves introducing mechanical dissipation into original polymer networks often require complicated chemical synthesis and result in significant hysteresis under cyclic loads. Designing soft solid materials into soft network materials with periodic lattice structure paving another effective route to improve the fracture-resistant performance of soft materials, which has not been reported in the literature. This work provides a combined experimental and computational study on the mechanical properties and fracture behaviors of elastomer-based soft network materials with/without a precut crack under monotonic and cyclic loads, aiming to present a structural design strategy for fracture-resistant soft materials. The elastomer-based soft network materials are proven to be crack-insensitive, low-hysteresis and anti-fatigue. The nonlinear finite element analysis (FEA) is employed to reveal the underlying mechanism of crack-insensitivity in elastomer-based soft network materials. Both the mechanical properties and deformed configurations of soft network materials with/without a precut crack are accurately predicted by the FEA method. The effect of microstructure geometry and network topology on the mechanical properties of soft network materials is systematically studied. Under various amplitudes of cyclic applied strain, the elastomer-based soft network materials can survive even after individual microstructures ruptured, and the fatigue fracture process slows down as the applied strain amplitude decreases. In contrast to the behavior observed in monotonic loads where fracture initiates at the microstructure located ahead of the crack tip, fatigue fracture initiation in soft network materials with a precut crack exhibits a random distribution.

Investigation of the fracture behavior of cemented waste rock-tailing backfill by digital image correlation technique and discrete element modeling

Cemented waste rock-tailing backfill (CWTB), as an artificial false roof in the downward-filling mining method, with its fracture mechanical properties, directly affects the safety of workers. However, few studies have been conducted on CWTB. Therefore, in this study, three-point bending tests and digital image correlation were used to systematically investigate the effects of waste rock aggregate content (10, 20, 30, 40, and 50 %) on the bending mechanical properties (bending strength, post-peak toughness, and fracture toughness) and deformation characteristics (crack extension length and crack opening length) of CWTB. In addition, based on the partition modelling method, a mesoscopic DEM model of CWTB was proposed to reveal the crack extension mechanism and contact force evolution trends of CWTB beams. The results showed that increasing the waste rock aggregate content decreased the flexural strength and increased the post-peak toughness of CWTB. The waste rock aggregate content affected the contact force distribution characteristics and contact force variation was the mesoscopic reason for the evolution of the mechanical properties of CWTB. This study provided important experimental data and simulation basis for the engineering application of CWTB.

Failure analysis of bolted steel plate connections with three-dimensional flexibilities

Steel plates are widely used in construction to connect different structural elements using welding or bolts. The fracture in these plates may lead to catastrophic consequences such as structural collapse. The paper investigates steel plates' deformation capacity and fracture behavior in bolted connections in three-dimensional (3D) flexibility. The peridynamic method is utilized to model the excessive deformation and fracture of steel plates in bolted connections when they are influenced by shear, moment, and torsion. The mesh-free nature of peridynamics enables modeling the extreme deformation and fracture in ductile materials such as steel. We validate the 3D peridynamic model by comparing its fracture and deformation results with experimental measurements and observations in several loading and boundary conditions. The paper highlights the following novelties: (1) a new and highly efficient 3D peridynamic model is proposed to model fractures in steel plates when exposed to combined actions of shear, moment, and torsion simultaneously; (2) the proposed 3D peridynamic model overcomes the difficulties faced by the mesh-based methods in modeling excessive deformation in ductile materials such as steel; (3) the study also reveals a shift in the fracture behavior of steel plates from ductile to brittle when exposed to high values of moment and torsion. This shift in fracture behavior has not been thoroughly addressed, impacting the integrity of steel structures and the warning stage for yielding. Overall, utilizing the 3D peridynamic model as a modeling and simulation tool can help engineers and researchers examine the behavior of steel plates under various loading conditions, thus allowing for optimization of the design of steel plates used widely in steel construction.

Impact of infill density on morphology and mechanical properties of 3D printed ABS/CF-ABS composites using design of experiments

Metal Extrusion (MEX) is a leading 3D printing technology for polymers, enabling intricate designs and personalized products in various applications. The current study evaluate how infill density affects the tensile, flexural, compressive, Izod impact and fracture behaviour of Acrylonitrile Butadiene Styrene (ABS) and Carbon Fiber Reinforced-Acrylonitrile Butadiene Styrene (CF-ABS) specimens manufactured using the MEX method. Different infill densities of 20, 40, 60 and 80 % are used in the production of honeycomb infill pattern samples for investigating the mechanical as well as fracture behaviour of MEX ABS/CF-ABS components. The experimental runs of fabricated composites were tested using a digital Izod impact tester and servo-controlled hydraulic universal testing machine, following ASTM standard procedures. The experimental findings show that CF-ABS specimens with an 80 % infill density and honeycomb fill pattern showed significant improvements in tensile strength, modulus, yield strength and elongation. The flexural strength (64.74 %), flexural modulus (209.15 %), compressive strength (125.21 %), compressive modulus (108.34 %) and impact strength (38.91 %) of these specimens are comparable to those of 3D printed ABS specimens and other infill densities. The research shows that precise management of processing variables can greatly improve the mechanical properties of 3D-printed ABS samples, providing valuable insights for a range of applications.

Study on the influence of thermo-pressure coupling environment on the fracture properties of shale in deep reservoirs

Deep reservoir in-situ environments enhance rock plasticity. Most current experiments that combine temperature and pressure are difficult to observe the crack tip directly, impeding the understanding of deep rock fracture properties. This paper used a digital image correlation method and the principle of fracture mechanics to establish an innovative visual experimental rock fracture system with in-situ environment. Crack tip initiation and propagation were captured dynamically in real-time temperature and pressure coupling conditions, and the influence on shale fracture properties was analyzed, providing a feasible method for examining the fracture behavior of deep reservoir rocks. The results showed that the fracture characteristics of deep shale should be reflected and characterized by jointly considering temperature and confining pressure. Shale plasticity produced crack tip passivation in combined in-situ temperature and pressure conditions, and reduced the local stress concentration effect. The post-peak softening relationship showed a nonlinear “convex” trend, indicating nonlinear fracture characteristics with increased toughness. The exponential coefficient representing the degree of nonlinearity rose as the buried depth increased. The exponential coefficient related to the buried depth was introduced to modify the constitutive model, which was used to effectively characterize the nonlinear fracture behavior of deep reservoirs and provide a basis for deep reservoir fracturing reform research.

Design and analysis of solid ankle foot orthosis by employing mechanical characterization and a low-cost scanning approach for additive manufacturing

PurposeThis study aims to investigate the fabrication of solid ankle foot orthoses (SAFOs) using fused deposition modeling (FDM) printing technology. It emphasizes cost-effective 3D scanning with the Kinect sensor and conducts a comparative analysis of SAFO durability with varying thicknesses and materials, including polylactic acid (PLA) and carbon fiber-reinforced (PLA-C), to address research gaps from prior studies.Design/methodology/approachIn this study, the methodology comprises key components: data capture using a cost-effective Microsoft Kinect® Xbox 360 scanner to obtain precise leg dimensions for SAFOs. SAFOs are designed using CAD tools with varying thicknesses (3, 4, and 5 mm) while maintaining consistent geometry, allowing controlled thickness impact investigation. Fabrication uses PLA and PLA-C materials via FDM 3D printing, providing insights into material suitability. Mechanical analysis uses dual finite element analysis to assess force–displacement curves and fracture behavior, which were validated through experimental testing.FindingsThe results indicate that the precision of the scanned leg dimensions, compared to actual anthropometric data, exhibits a deviation of less than 5%, confirming the accuracy of the cost-effective scanning approach. Additionally, the research identifies optimal thicknesses for SAFOs, recommending a 4 and 5 mm thickness for PLA-C-based SAFOs and an only 5 mm thickness for PLA-based SAFOs. This optimization enhances the overall performance and effectiveness of these orthotic solutions.Originality/valueThis study’s innovation lies in its holistic approach, combining low-cost 3D scanning, 3D printing and computational simulations to optimize SAFO materials and thickness. These findings advance the creation of cost-effective and efficient orthotic solutions.

Damage identification and fracture behavior of 2.5D SiCf/SiC composites under coupled stress states

Continuous fiber-reinforced silicon carbide composites have received significant attention due to their high-temperature mechanical stability. However, their widespread implementation has been hindered by intricate fracture mechanisms and limited toughness. This study presents a real-time approach for identifying damage type in 2.5D SiCf/SiC composites and highlights the significant impact of minor eccentric loading angle on the fracture behavior and mechanical properties using acoustic emission (AE). Even a slight degree of eccentric loading angle can significantly alter the fracture behaviors, leading to a significant increase in fracture toughness. The fracture damage evolution law of 2.5D SiCf/SiC under varying eccentric loading angles was investigated with the help of the AE damage identification, fracture morphology and finite element analysis. These findings provide valuable insights for multi-axis stress analysis of 2.5D high-performance composites.

Experimental exploration of fracture behavior (pure mode III) in eco-friendly steel fiber-reinforced self-compacting concrete with waste tempered glass as coarse aggregates

To aid in the creation of sustainable structures, scientists have utilized waste materials found in the environment to serve as alternatives for traditional resources in the construction sector. They have undertaken extensive investigations pertaining to this matter. In this particular study, tempered glass as waste glass coarse aggregate (WGCA) was substituted for natural coarse aggregate (NCA) at varying proportions of 15%, 30%, and 45% in the formulation of eco-friendly self-compacting concrete (SCC), combined with hooked-end steel fibers (SFs) at various volumes. The study assessed concrete’s flowability, permeability, compressive strength, and fracture parameters at 28 and 56 days. A total of 240 edge-notched disc bending samples (ENDB) and 60 cubic samples (150 × 150 mm) were tested to assess fracture resilience and compressive strength, respectively. The results showed that increasing SF and WGCA content reduced slump flow diameter and blockage ratio, particularly at higher levels. The solidified characteristics of all specimens incorporating SF and WGCA displayed heightened attributes when contrasted with the reference sample. Among the entire array of specimens, WG15SF0.5 and WG30SF0.5 exhibited the most superior performance, demonstrating an average percentage elevation of 20.29 and 27.63 in both compressive strength and fracture toughness assessments across the different curing periods. SF had the most significant impact on post-cracking behavior by enhancing load-bearing capacity through a bridging fiber mechanism. Through a comparison of the influence of SFs and WGCA on the fracture toughness of pure mode III, it was observed that the inclusion of SF in samples with a 30% replacement of WGCA resulted in an average increase of approximately 15.48% and 11.1% in this mode at the ages of 28 and 56 days, respectively, compared to the control sample.