Shear Fracture Research Articles

Simultaneously improving interfacial adhesion and toughness of carbon fiber reinforced epoxy composites by grafting polyethyleneimine on the carbon fiber surface to construct a rigid‐flexible interface

AbstractChemical grafting is commonly employed to functionalize carbon fiber (CF) surface to enhance the interfacial properties of CF reinforced polymer composites (CFRP) by forming a robust interface. However, an overly rigid interface layer can result in relatively poor interface toughness. To balance interfacial strength and toughness, this paper proposes an effective method to simultaneously strengthen and toughen the interface of CF/epoxy composites by grafting branched polyethyleneimine (PEI) on CF surface using hexachlorophosphazene (HCCP) as active intermediate, which features a rigid ring structure and six active P‐Cl groups. The introduction of PEI provided a large number of amine and imine groups on CF surfaces, which were contributive to improving surface wettability and reactivity of CF, thus resulting in strong chemical bonding between CF and epoxy matrix. Additionally, the long and flexible molecular skeleton of PEI constructed a rigid‐flexible composite interface, which could effectively reduce stress concentration and absorb impact energy. After surface modification with PEI, the interfacial shear strength and fracture toughness of CF/epoxy composite were increased to 89.9 MPa and 200.3 J m−2, by 64.3% and 149.7%, respectively, in compared with desized CF reinforced epoxy composites.Highlights A rigid‐flexible interface was constructed between CF and epoxy resin. The interfacial strength and toughness of CFRP were synergistically improved. IFSS and interfacial toughness increased by 64.3% and 149.7%, respectively.

Discrete element-based multi-cluster hydraulic fracture extension study with temporary plugging and fracturing in horizontal wells

In this paper, a two dimensional-discrete element method complex fracture extension model was developed to simulate the fracture extension behavior in reservoirs during multi-cluster perforation fracturing of horizontal wells by particulate flow and considering temporary plugging conditions. The effect of particle inhomogeneity on the extension of multi-cluster fractures, the change of fracture extending characteristics before and after temporary plugging, and the effect of geological and construction parameters on the extension of multi-cluster fractures under the consideration of temporary plugging conditions are investigated in this model. The results show that: (1) the middle cluster is more difficult to extend than the outermost cluster due to interstitial stress interference; the increased nonuniformity of particles aggravates interstitial stress interference and favors shear fracture extension. (2) Fractures expand substantially when the fracturing fluid reaches 3/4 of the total fluid volume; after temporary plugging, it can promote the uniform extension of fractures and increase the total length of fractures, but the fractures formed in the middle are easy to be captured by the fractures at the two ends and expand along it, and it is not easy to form complex fractures; the timing of plugging is based on the percentage of perforation clusters with fractures already formed, with fracture extension being preferred. (3) The horizontal principal stress difference mainly affects the direction of fracture extension; the number of clusters mainly affects the uniformity of fracture extension; and the fluid flow mainly affects the length of fracture extension.

Optimal screw orientation for fixation of coronal shear fractures: a biomechanical comparison

Coronal shear fractures of the capitellum are rare injuries which can be challenging to treat. The aim of this study was to compare the biomechanical properties of different internal screw fixation techniques for Dubberley type IA fractures of the capitellum. In this biomechanical study, Dubberley type IA fractures of the capitellum were created in 30 human fresh-frozen humeri. The specimens were then divided into 3 groups: fixation was either performed with 3×3.0mm headless cannulated compression screws (HCCSs) in anteroposterior (AP) orientation (AP group), 3×3.0mm HCCSs in posteroanterior (PA) orientation (PA group) or with 2×3.0mm HCCSs in PA orientation and 1×3.0mm HCCS in lateral orientation (LAT) group. Displacement under cyclic loading and ultimate load-to-failure were evaluated in all specimens. There was no significant difference in fragment displacement after 2000 cycles between AP and PA groups (0.8±0.5mm vs. 0.8±0.6mm; P=.987) or PA and LAT groups (0.8±0.6mm vs. 0.8±0.3mm; P=.966). LAT group showed the highest load-to-failure (548±250N) without reaching statistically significant difference to AP group (388±173N; P=.101). There was also no significant difference between AP and PA groups (388±173N vs. 422±114N; P=.649). Variations in screw placement had no statistically significant influence on cyclic displacement or load-to-failure in Dubberley Type IA fractures. However, fracture fixation in 2 planes-both the coronal and the sagittal plane-by adding a screw in a lateral to medial direction may be beneficial to increase primary stability.

Ligament Sparing Elbow Hemiarthroplasty: A Novel Technique for the Management of Distal Humeral Fractures.

Intra-articular distal humerus fractures present various challenges with a wide array of treatment options. Open reduction internal fixation remains the treatment of choice. In older patient populations with poor bone quality and short-end segment fractures with articular comminution, open reduction internal fixation, however, may bring on unsurmountable technical challenges. Total elbow arthroplasty and elbow hemiarthroplasty (EHA) may offer superior functional outcomes in these cases. During EHA for fractures, the medial and lateral columns are reconstructed with the collateral ligaments to restore elbow stability. We hypothesize that in coronal sheer fracture patterns where the columns are intact, maintaining the native collateral ligaments and columns will provide both an anatomic and stable elbow joint. We introduce the ligament sparing EHA technique for unreconstructible coronal shear fractures. We describe this novel technique and compare our postoperative outcomes in 2 patients who underwent this surgery to those described in the literature. The postoperative Disabilities of the Arm, Shoulder, and Hand scores for the 2 patients were 13.8 and 10.3, respectively. The Mayo Elbow Performance Score for the 2 patients were 80 and 85, respectively. The operative arm presented a grip strength of 82% and 89% when compared with the contralateral arm, for the patients respectively. The range of motion varied between 78% and 100% of the contralateral arm for both patients. Although our results are promising and the ligament sparing EHA technique may be a more anatomic option in certain fracture patterns, further research with larger cohorts and multiple surgeons is needed to reinforce our results.

Clinical Outcomes and Management Strategies for Capitellum and Trochlea Fractures: A Systematic Review.

Capitellum and trochlea fractures, also referred to as coronal shear fractures of the distal humerus, are infrequent yet challenging intra-articular fractures of the elbow. There are a variety of surgical approaches and fixation methods with often variable outcomes. This systematic review investigates interventions, outcomes and complications of capitellum and trochlea fractures. A systematic review of studies published in MEDLINE, EMBASE, Web of Science and Cumulative Index to Nursing and Allied Health literature (CINAHL) was conducted to assess the clinical outcomes of capitellum and trochlea fractures managed surgically. Data on patient demographics, surgical approach, implant usage, postoperative outcomes and complications were compiled. Forty-one studies met the inclusion criteria with a total of 700 patients. Surgical interventions primarily utilized either the lateral (79%) or antero-lateral (15%) approaches with headless compression screws as the most common fixation method (68%). Clinical outcomes were measured using the Mayo Elbow Performance Index (MEPI) with a mean score of 89.9 (±2.6) and the DASH score with a mean of 16.9 (±7.3). Elbow range of motion showed a mean flexion of 126.3° (±19.4), extension of 5.71° (±11.8), pronation of 75.23° (±12.2), and supination of 76.6° (±9.8). The mean flexion-extension arc was 113.7° (±16.9), and the mean pronation-supination arc was 165.31° (±9.41). Complications occurred in 19.8% of cases, with re-interventions required in 8.3% of cases, mainly due to symptomatic implants and elbow stiffness requiring surgical release. Other complications included implant removal (10.4%), overall reported stiff elbows (6%), nerve palsies (2%), non-union (1.5%), and infection (1.2%). The treatment of capitellum and trochlea fractures yields satisfactory outcomes but has a considerable rate of complications and reoperations primarily due to symptomatic implants and elbow stiffness. There is noteworthy variability in the achieved range of motion, suggesting unpredictable outcomes. Deficits in functionality and range of motion are common after surgery, especially with more complex injury patterns.

Study on formation of exit edge defects in the milling process by using the combined theory of the energy conservation and orthogonal cutting mechanism

1 In the milling process, due to machining materials and process parameters, the material at the edge of the part may break due to shear forces instead of cutting properly, resulting in the irregular pit (defect) at the exit edge. This seriously affects the surface quality of the workpiece. It is vital to understand the forming mechanism of the exit edge defect (EED) before one tries to eliminate or reduce the size of the EED and furthermore to improve the machining accuracy. Therefore, focusing on the milling process at exit edge of a workpiece, this paper presents a novel theoretical model to study the forming principle of the EED and predict the corresponding size. First, the forming process of the EED is separated into two stages. The beginnings of them are symbolized by the initial- and the fracture-negative shear planes. Then, the initial-negative shear plane which is defined by the initial negative shear angle is found. Furthermore, the location of the fracture-negative shear plane is defined using the fracture negative shear angle to study the EED. For the next step, the concentration force of Flamant-Boussinesq problem combined with the yield strength of the material is introduced to obtain the initial negative shear angle. Additionally, using the energy conservation theory, the negative fracture shear angle is calculated. Based on these, the mechanism of the EED is illustrated. Besides, the size (including length and depth) of the EED is predicted based on the geometric relationship between the initial and the fracture negative shear angle. Finally, the correctness of the theoretical model is verified by simulation and experiments. This study provides a promising step to reducing/eliminating the hazards of edge defects.

Effect of ultrasonic amplitude and riveting speed on mechanical properties of Ti-45Nb riveted lap joints

Ultrasonic vibration-assisted machining has been introduced as a new process in riveting aircraft components. In this paper, the effects of different ultrasonic amplitudes and riveting speeds on the quality, shear properties, and cross-tension properties of riveted joints are investigated. The failure sample fracture was characterized using a scanning electron microscope and the cause of the fracture was discussed. The results show that the ultrasonic amplitude is negatively correlated with the height of the riveted joint and positively correlated with the diameter of the riveted joint. The maximum shear failure load was obtained at a riveting speed of 5 mm/s with an ultrasonic amplitude of 35.3 μm, and the maximum cross tensile failure load was obtained at an ultrasonic amplitude of 23.3 μm. All shear fractures occurred in the rivet shanks and all cross fractures occurred in the rivet manufactured head, and the failure modes of both shear and cross-tension fracture were mixed brittle and plastic fracture modes.

Posterolateral Shear Fracture of the Capitellum Associated with Elbow Dislocation in Adolescent: A Case Report

Posterolateral Shear Fracture of the Capitellum Associated with Elbow Dislocation in Adolescent: A Case Report

Effect of Welding Parameters on Lap Shear Force of Similar and Dissimilar Friction Stir Spot Welded Aluminium Alloys

Friction stir spot welding (FSSW) is a solid-state single-point welding technique that uses a rotating tool consisting of a shoulder and a pin for joining nonferrous metals and alloys. FSSW produces a keyhole at the welding point, which decreases the mechanical strength of the joints. This study investigates the influences of tool rotational speed (1000, 1250, and 1500 rpm) and dwell time (5, 10, and 15 s) on the shear fracture load of the FSSW joints. Two different grades of aluminium alloy plates, i.e., AA6061 and AA7075 were used to produce similar (7075-7075 and 6061-6061) and dissimilar (6061-7075) alloy joints. The plates with a thickness of 3 mm were folded above each other before a rotating tool pin was plunged through the thickness of the top plate to obtain an FSSW lap joint. It was found that tool rotational speed and dwell time induced a considerable impact on the microstructure, and shear strength. The results indicated that the grain size of microstructure in similar and dissimilar joints was affected by the rotational speed and dwell time. The grain size of the microstructure increased as rotational speed and dwell time increased. The results also showed that a tool rotational speed of 1250 rpm and dwell time of 10 s gave the highest shear fracture load for 7075-7075 similar and 6061-7075 dissimilar joints. However, for 6061-6061 similar joints, the highest mechanical strength was obtained at 1250 rpm and 10 s.

Sparrow search algorithm enhanced multi-output regression for predicting rock fracture shear displacements: A metaheuristic-hybridized model

This study presents a metaheuristic-hybridized model based on sparrow search algorithm (SSA) and multi-output least-squares support vector regression machines (SSA-MLS-SVR) to predict the continuous shear displacements of rock fractures, which is closely related to the geo-structure stability and safety. Based on the database including 258 continuous shear samples of rock fractures, two subdatasets recording continuous shear displacements in three (216 samples) and four steps (141 samples) are used to develop the proposed model respectively. In the model improvement phase, three kinds of nonlinear transformations are utilized to eliminate the low sensitivity of SSA-MLS-SVR model caused by value scale and data distribution. The experimental results show that the nonlinear transformations can significantly improve the prediction accuracy of SSA-MLS-SVR. Additionally, some characteristics of the continuous shear process of rock fractures are also discovered via extended experiments. First, the prediction accuracy of the first-step shear displacement can be greatly improved using the peak shear displacement as an input. And it is inferred that the beginning of the post-peak shear process (the first-step shear) may be closely related to the peak shear of rock fractures. Second, the post-peak shear process is a continuous random process, in which the displacement of each shear step is only highly correlated with the most recent shear displacements in the time dimension.

Effect of curing process on shear and interlaminar fracture toughness of vinylester urethane-glass fibre composites

The influence of the curing process on the interlaminar shear strength and mode II toughness of Vinylester-Urethane resin composites with high density glass fibre plain fabric is shown in this work. There is a shorter curing treatment that achieves similar mechanical properties compared to the treatment proposed by the resin manufacturer. This is of industrial interest as shortening time leads to savings in production costs.

Fracture behaviors of sustainable recycled aggregate concrete under compression-shear loading: Laboratory test, numerical simulation, and environmental safety analysis

A series of compression-shear tests were carried out to investigate the shear failure of sustainable recycled aggregate concrete, and shear failure surfaces were scanned by a 3D laser scanner. The effect of recycled coarse aggregate (RCA) replacement rates and normal stresses on the shear strength, failure mode, and fracture morphology were analyzed. Meanwhile, discrete element method was used to study shear behaviors at a mesoscale. Finally, the carbon emission was calculated to evaluate the effect of RCA on the environment. The result shows that the shear strength, cohesion c, and internal friction angle φ all decrease as the RCA replacement rate increases. The shear damage of RAC can be aggravated by increasing the RCA replacement rate. Fractal dimension and joint roughness coefficient of shear failure surface tend to increase with increasing RCA replacement rate and normal stress. In addition, more microcracks can be found in coarse aggregate with the increase in RCA replacement rate, and the increasing normal stress can cause more microcracks. Given the nonlinear development of stress-displacement, a modified nonlinear constitutive model is proposed. Finally, the total carbon emissions of recycled aggregate concrete are calculated considering production, transportation, and construction, the carbon emission of 100% sustainable recycled aggregate concrete is 10.2% less than that of 100% natural aggregate concrete.

Phase-field model for 2D cohesive-frictional shear fracture: An energetic formulation

This paper presents a phase-field model for cohesive-frictional shear fracture. The model is derived based on two energetic principles: the energy conservation law and a variational inequality of virtual work that serves as a stability condition. We show that all the governing equations for frictional fracture can be obtained from the above two principles, including the equilibrium condition, the phase-field evolution law and, most importantly, the yield function and flow rule for the plasticity-like frictional slip. The information of crack direction is naturally included in the flow rule. Theoretical and numerical results show that the proposed model is faithfully consistent with the Mohr–Coulomb theory of frictional failure in terms of the crack nucleation stress and direction. In addition, the presented phase-field model has an explicit frictional cohesive law.

Anisotropic size effect of 3D printed LC3-based engineered cementitious composites (LC3-ECC)

One of the critical factors affecting the development of 3D concrete printing (3DCP) is the challenging issue of in-situ reinforcement. Engineered Cementitious Composites (ECC) are printable self-reinforced materials, and their application in 3DCP technology can facilitate de-steelisation. However, traditional ECC materials pose certain concerns for sustainable environmental development. The integration of Limestone Calcined Clay Cement (LC3) suitable for 3DCP into ECC (LC3-ECC) presents an ideal solution to the aforementioned challenges. Moreover, conducting comprehensive research into its size effects is an essential step from experimentation to engineering application. A thorough exploration of the size effects of 3D printed LC3-ECC in compression, shear, and flexural fracture aspects is conducted to derive size effect laws. The relationship between the anisotropic mechanical properties and size effects has been established. The mold-cast LC3-ECC precisely follows the Bažant size effect law (SEL). The fiber orientation effect enhances bridging efficiency, leading to the fact that the mechanical properties of certain printed LC3-ECC are hardly affected by the size effect. The mechanical performance of some printed LC3-ECC depends on interlayer strength, making its primary reason for size effect not in the Fracture Process Zone (FPZ) energy release, hence closer to the Multifractal Scaling Law (MFSL). LC3-ECC exhibits weak anisotropy in mechanical properties, showing satisfactory stability. However, under flexural fracture behavior, the anisotropic size effect is higher, necessitating careful consideration in structural design.

Interlayer Shear Sliding Behaviors during the Fracture Process of Thick Sandstone Roof and Its Mechanism Leading to Coal Mine Tremors

To explore the causes of mine tremors in coal mines with sandstone roofs, a three-point bending loading experiment was designed for composite sandstone layers, and the fracture and interlayer shear slip characteristics of the composite sandstone layers were studied using optical measurement and acoustic emission techniques. The results show that the bending of the rock layers led to interlayer sliding deformation, while the fracturing greatly promoted interlayer sliding. The maximum interlayer slip accelerations during bending deformation and fracturing were 0.6 mm/s2 and 3.8 mm/s2, respectively. During the fracturing of the rock layers, the proportion of acoustic emission shear fracture events increased with the continuous occurrence of long-lasting and high-amplitude acoustic emission events. The mechanism of mine tremors in thick sandstone roofs is as follows: the increase in the area of the goaf causes rock bending deformation and fracturing, accompanied by interlayer shear slip, fracturing of the sandstone layer, and friction dislocation at the cementation surface of the adjacent sandstone layers, which jointly cause vibration of the roof.

Digital elevation model‐based lineament analysis of the Zindapir anticline, Sulaiman fold‐and‐thrust belt, Pakistan

The N‐S oriented Zindapir anticline is an eastward verging mega‐structure (~130 km along and ~40 km across the strike) in the eastern Sulaiman fold‐and‐thrust belt on the western margin of the Indian Plate in Pakistan. In this study, we carried out a lineament analysis of the anticline based on shuttle radar topographic mission (SRTM) images and digital elevation model (DEM) data to demonstrate the application of this technique for modelling of the fractured reservoirs. We used shaded relief images, variations in the vertical exaggeration, sun and azimuth angles to enhance the DEM data and structures in the area. Stereographic projections indicated that the anticline is an upright, asymmetrical, gentle, doubly plunging and east‐vergent fold. The synthesized lineament map of the fractures indicates a total of 402 fractures across the Zindapir anticline. A total of 204 and 198 fractures were observed in the eastern and western limbs, respectively. Statistical analysis portrayed that the lineaments of the majority of fractures followed northwest‐southeast (NW‐SE) and west‐northwest—east‐southeast (WNW‐ESE) trends. These are oblique or transverse to the fold axis and could be interpreted as shear and tensional fractures related to drag and compression along the western boundary of the Indian Plate. Our study provides an example of lineament analysis for structural characterization and modelling of fractured reservoirs in a collision‐mountain setting.

Long-term properties evolution and life prediction of glass fiber reinforced thermoplastic bending bars exposed in concrete alkaline environment

Glass fiber reinforced polypropylene (GFRPP) bending bars have many advantages, such as high toughness, high durability, repeated molding and recycling, which can be used in concrete structures to replace steel stirrup for solving the problems of corrosion and service life. However, the changes in the properties of GFRPP bending bars during long-term use in alkaline concrete environments require further investigation. In the present study, GFRPP bending bars were immersed in alkaline solution at 20 °C, 40 °C, and 60 °C for as long as 180 d. The water absorption, hydrolysis, mechanical properties, and microscopic properties of the bending bars were evaluated to understand the long-term performance and mechanism of degradation. The bending bars had a higher saturated water absorption percentage and time along with a lower diffusion rate than the straight bars due to the presence of pores and micro-cracks formed during the bending process. The dissolution of the glass fibers in alkaline solution led to the partial mass loss of the GFRPP bars. Compared to the control, the tensile strength retention of the bending bars was 20.6%–56.0 %. The tensile failure mode changed from fiber bursting before immersion to shear fracture after immersion due to the decreased interfacial bonding strength and increased glass fiber brittleness. The primary degradation mechanisms were the etching of glass fibers, interface debonding, and increased void volume (∼23.7 %). The bending bars were more seriously eroded than the straight bars due to the twisting of the fibers and imperfect interfaces. The predicted degradation times of the GFRPP bending bars ranged from 1.7 years (Haikou) to 3.9 years (Harbin), corresponding to a stable tensile strength retention of 22.13 %. The results provide a basis for evaluating the durability and service life of GFRPP bending bars and promote the application of GFRPP composite stirrups in concrete structures.

Evolution of Deformation Failure and Energy of Siltite and Significant Shear Fracture Structure Under Cyclic Loading

Evolution of Deformation Failure and Energy of Siltite and Significant Shear Fracture Structure Under Cyclic Loading

Outcome of Complex Coronal Shear Fractures of the Distal Humerus (Dubberley Type 3) Managed by the Transolecranon Approach.

Complex distal humerus coronal shear fractures are rare injuries. These fractures involve small articular fragments and are challenging to fix. Aprospective case series of 10 patients was done at a level 1 trauma centre between February 2017 and July 2021. Dubberley type 3 fractures were included in the study. All patients underwent ORIF using posterior approach with olecranon osteotomy by a single surgeon.Patients were followed up for a minimum of 12months postoperatively. The primary outcome measures were radiographic union and functional status of the limb (DASH score and MEPI score). All patients achieved radiographic union of fracture as well as the osteotomy. The mean DASH score as measured on the final follow-up was 12.6 ± 10.2 and the mean MEPI score was 90 ± 8.2. None of the cases needed reoperation. Consistently good functional outcomes can be obtained in complex coronal shear fractures by posterior approach with olecranon osteotomy. Dubberley type 3b patients should undergo additional plate fixation.

Study on Shear Failure Process and Zonal Disintegration Mechanism of Roadway under High Ground Stress: A Numerical Simulation via a Strain-Softening Plastic Model and the Discrete Element Method

Fracture expansion in rock masses can be observed by monitoring the break of contacts between the bounding particles via the discrete element method. The latter’s realization in this study via the PFC2D program tracked the evolution process of the zonal disintegration in an exemplary roadway-surrounding rock affected by mining. Besides, the damage evolution pattern in a high-stress soft rock roadway was simulated by the FLAC2D program using a strain-softening plastic model, revealing the effects of rock mass strength, stress state, and anchor support on the zonal disintegration of the roadway. Numerical simulation results show that in a roadway with high-level stress, the obvious fractures spread from the roadway surface to the depth of the surrounding rock along a series of geometric planes and cut the surrounding rock into rock mass blocks. Under high crustal stress, conjugate shear fractures occur near the roadway surfaces and form a closed-loop fractured zone after intersecting the conjugate fracture faces. The closed fractured zone becomes a free face, from which conjugate shear fractures develop, forming new closed fractured zones in the deep surrounding rock. By repeatedly generating the closed fracture zones, a fracture network appears in the roadway-surrounding rock. The development of zonal disintegration of roadway-surrounding rock mainly depends on the rock mass strength and its stress state. Zonal disintegration only occurs when the crustal stress of the roadway-surrounding rock exceeds its strength. When the horizontal stress is low and the vertical stress exceeds the rock mass strength, zonal disintegration only occurs on two sides of the roadway. When the vertical stress is low and the horizontal stress exceeds the rock’s mass strength, it only appears on the roof and floor. When the values of cohesion, internal friction angle, and tensile strength are reduced in the same proportion, cohesion has the greatest impact on the expansion of the zonal disintegration zone, followed by the internal friction angle, while the tensile strength effect is the least. In anchor-supported roadways undergoing zonal disintegration processes, the intact zone blocks slide relatively along the fracture surface during the process of loosening and deformation of the surrounding rock, making the anchor rods susceptible to tensile, shear, and bending actions.