Fracture Of Composites Research Articles

The impact of matrix viscosity on the mechanical behavior of fiber reinforced composites

AbstractThe influence of matrix viscosity on the mechanical behavior of fiber reinforced composites was investigated in this paper. The glass fiber fabric was selected as reinforcement and the mixed solution composed of resin, curing agent and different viscosity of diluent was selected as matrix. The composites was fabricated by vacuum‐assisted resin infusion (VARI). The influence of matrix viscosity on bending, impact and creep properties of composites were studied by varying the mass fraction of 1,4‐butanediol diglycidyl ether (BDDGE) diluent, the least square fitting was used to fit the experimental result. The mathematical model for characterizing the relationship between the matrix viscosity and the bending strength was established, and the mass fraction of BDDGE diluent based on the optimal bending property was obtained. The failure mechanisms were analyzed by analyzing fiber reinforced composites properties, reaction principles and fracture morphologies. Result shows that the epoxy groups within the viscosity undergo a ring‐opening reaction to integrate the cross‐linking network structure of the epoxy resin. However, an excessive amount of diluent will result in an increase of number of flexible chain segments, which initially enhancing the mechanical properties of the specimens before causing a subsequent decline. The mathematical model was substantiated by experiment, which reveals that the viscosity is 185.3 mPa·s for the optimal bending properties.Highlights The bending strength and modulus reached the maximum at a viscosity of 180 mPa·s The creep curves demonstrate progressive damage and minute deformation. The ring‐opening reaction occurs with two oxygen atoms in the diluent BDDGE. The matrix viscosity of BDDGE diluent is 185.3 mPa·s for the optimal bending properties.

Denture base poly(methyl methacrylate) reinforced with SrTiO3/Y2O3: Structural, morphological and mechanical analysis

AbstractThis study presented the use of SrTiO3/Y2O3 nanoparticles for the reinforcement of dental poly(methyl methacrylate) (PMMA) to enhance its mechanical properties important for everyday use of denture base materials. The average crystallite size of prepared nanoparticles was 19.9 nm. The influence of 0.5, 1.0, and 1.5 wt% SrTiO3/Y2O3 loading on absorbed impact energy, microhardness and tensile properties was investigated. Scanning electron microscopy of the composite fracture surface revealed multiple toughening mechanisms, with agglomerates directly included in the crack pinning, indicating improvement in mechanical performance. Dynamic mechanical analysis proved that agglomerates improved the elastic behavior of PMMA and confirmed the absence of a residual monomer. After the incorporation of SrTiO3/Y2O3, the mechanical properties of composites showed a high increase compared to neat PMMA. The optimal concentration of nanoparticles was 1 wt%, for which the microhardness, modulus of elasticity, and absorbed impact energy were higher by 218.4%, 65.8% and 135.6%, respectively. With such a high increase, this research showed that SrTiO3/Y2O3 represents an efficient filler which use does not have to be limited to dental materials.Highlights SrTiO3/Y2O3 hybrid nanoparticles were prepared. PMMA‐SrTiO3/Y2O3 composite showed increase in impact resistance up to 135.4%. Elastic behavior of PMMA was improved. With 1 wt% of SrTiO3/Y2O3, microhardness increased by 218.4%.

Osteoporotic fracture risks of thiazides and dihydropyridines in angiotensin modulator users.

To determine whether thiazides, combined with either angiotensin-converting enzyme inhibitor (ACEi) or angiotensin II receptor blocker (ARB), offer bone-protective benefits compared with dihydropyridine (DHP) drugs combined with ACEi or ARB. This retrospective cohort study was conducted on the US Collaborative Network from the TriNetX database on March 5th, 2024. It included hypertensive ACEi or ARB users under thiazide or DHP drug treatments spanning from January 1st, 2015, to December 31st, 2022, with exclusion criteria applied. The primary outcome is a composite typical osteoporotic fracture (TOPF). Kaplan Meier analyses were performed after 1:1 propensity-score matching (PSM) with a 5-year follow-up. Besides investigating fracture-related outcomes in thiazide-ACEi/ARB and DHP-ACEi/ARB users, this study explores whether the effects differ between ACEi and ARB users. Subgroup analyses were also performed, and the heterogeneity among the results was assessed using Cochran's Q-tests. Post-PSM results yield 54,240 patients per cohort in the primary analysis, aging 61.5 ± 12.2 versus 61.4 ± 13.7 (thiazide-ACEi/ARB versus DHP-ACEi/ARB) with predominantly white ethnicity. Thiazide-ACEi/ARB users exhibit lower TOPF risk than DHP-ACEi/ARB users (hazard ratio (HR) = 0.65, 95% confidence interval (CI) 0.61-0.70), and such benefits from thiazides are similar between ACEi and ARB users (ACEi: HR = 0.69; ARB: HR = 0.67, Cochran's Q-test p-value = 0.78). Additionally, the effects of thiazides reveal significant heterogeneity between patients with and without inflammatory polyarthropathy (ICD-10, M05-M14) and benzodiazepine usage (Cochran's Q-test p-value = 0.01, 0.04). Thiazides are associated with lower risks of typical osteoporotic fractures compared to DHP drugs in patients treated with ACEi or ARB, while such benefits may diminish in those with a diagnosis of inflammatory polyarthropathy and benzodiazepine usage.

Achieving Strength and Toughness in Dual-Phase Mg-8Li Alloys Through Phase Structure Control and Composite Fracture.

The rising industrial demand for ultra-lightweight materials with exceptional strength and toughness has intensified interest in dual-phase Mg-Li alloys due to their low density and high specific strength. While much of the research on Mg-Li alloys has concentrated on conventional strengthening methods, such as grain refinement and solid-solution strengthening, overcoming the challenge of plastic deformation compatibility between the α- and β-phases remains unresolved. This study focuses on Mg-8Li binary alloy, systematically investigating the impact of rolling deformation temperature and strain on the phase structures. A detailed analysis of fracture behavior reveals a novel brittle-tough composite fracture control strategy that enhances both strength and toughness simultaneously. This work advances the understanding of phase structure control and its role in strengthening and toughening mechanisms, offering critical insights for the development of next-generation dual-phase magnesium alloys.

Interpretable Multi-Label Classification for Tibiofibula Fracture 2D CT Images with Selective Attention and Data Augmentation.

Tibiofibula fractures occur across all age groups, and postoperative complications are frequent. An accurate and rapid classification methodology for these fractures could significantly assist physicians. Clinically, tibiofibula fractures occur at various locations, and the fracture types are not evenly distributed. This paper presents a deep learning model for the interpretable multi-label classification of tibiofibula fractures in two-dimensional (2D) CT scan images, addressing the challenges posed by a limited sample size and an uneven distribution of fracture types. We retrospectively collected 2494 2D CT images from 168 patients with tibia or fibula fractures. The types of fractures identified in the CT scan images were classified according to the AO/OTA fracture classification. A deep learning model was developed to classify composite fractures in 2D CT images, providing visual interpretation for each identified class. The visual interpretation was given with the saliency maps constructed by the Grad-CAM++ method. The deep learning model was trained using data augmentation techniques to address class imbalance and the limited dataset size. Our experiments demonstrated that the proposed model achieved a mean average precision (mAP) of 95.71%. The saliency map-based visual interpretation enables the verification of whether the model provides reliable decision-making for classification.

Deformation and fracture of lithosphere-inspired polymeric multi-layer composites

Inspired by the diversity of structures and patterns inherent in the earth's lithosphere, this study endeavors to enhance the interplay between stiffness and toughness through the introduction of a new class of polymeric multi-layer composite materials termed by the authors as "lithomers". Structured single-edge notched bending specimens were fabricated using a combination of additive manufacturing and casting, employing two different methacrylate-thiol resins. The outer layers exhibit a stiff and brittle characteristic, while the layer in between is compliant in nature. Three types of lithomers with wave-like structures and one with a rectilinear structure were investigated regarding their stiffness and toughness in a 3-point bending setup. The results were compared with those of a pure stiff matrix material. The findings revealed that fracture toughness increased regardless of the interlayer's shape compared to the pure matrix material. Correspondingly, this enhancement in fracture toughness correlated with a reduction in stiffness. The most balanced results in terms of stiffness and fracture toughness were achieved, with the lithomer having a wave-like structure in its initial stage. It exhibited a roughly 27 times improvement in fracture toughness with a moderate decrease in stiffness of approx. 1/5 compared to the pure matrix material.

In vitro analysis of flowable and high viscosity bulk fill composite versus conventional composite in core build up of endodontically treated teeth

This study aimed to test the load to fracture of flowable and high viscosity bulk-fill composites compared to a convetional (packable) composite used to build up pulpless teeth. 45 endodontically treated premolars were restored with fiber posts then divided into three groups (N = 15) according to the core build-up material. SDR group: (Smart Dentine Replacement), (BF): Filtek One Bulk Fill and (CC) Filtek Z350 packable composite. After core build up the teeth received full coverage crowns. Load to fracture (Newton) was recorded for each specimen. One-way ANOVA and Tukey multiple comparisons test were used. The highest load at fracture was shown by (CC) group (1067 N), followed by (BF) group (879 N), and the SDR group (838 N). One way ANOVA and Tukey’s multiple comparisons test demonstrated no significant differences between CC, SDR, and BF groups (p > 0.05). The three materials showed comparable load to fracture. Further studies with simulation to occlusal forces and oral temperature are required.

Experimental Study on the Efficiency of Fracturing Integrated with Flooding by Slickwater in Tight Sandstone Reservoirs

Tight reservoirs, with their nanoscale pore structures and limited permeability, present significant challenges for oil recovery. Composite fracturing fluids that combine both fracturing and oil recovery capabilities show great potential to address these challenges. This study investigates the performance of a slickwater-based fracturing fluid, combined with a high-efficiency biological oil displacement agent (HE-BIO), which offers both production enhancement and environmental compatibility. Key experiments included tests on single-phase flow, core damage assessments, interfacial tension measurements, and oil recovery evaluations. The results showed that (1) the slickwater fracturing fluid effectively penetrates the rock matrix, enhancing oil recovery while minimizing environmental impact; (2) it causes substantially less damage to the reservoir compared to traditional guar gum fracturing fluid, especially in cores with little higher initial permeability; and that (3) oil recovery improves as HE-BIO concentration increases from 0.5% to 2.5%, with 2.0% as the optimal concentration for maximizing recovery rates. These findings provide a foundation for optimizing fracturing oil displacement fluids in tight sandstone reservoirs, highlighting the potential of the integrated fracturing fluid to enhance sustainable oil recovery.

Interphase mechanics vs chemical compatibility: Generating a deformable PA6-carbon fiber interphase

Good interfacial adhesion is typically correlated to obtaining the best tensile/flexural performance for carbon fibre-reinforced composites. The nature or even presence of the interphase, a localized region around the fibre-matrix junction, is often discussed but notoriously difficult to visualize and characterise. Here, a surface-initiated electro-polymerization approach to covalently graft either polyacrylamide or polygylcidyl methacrylate to the carbon fibres was used. This was followed by continuous melt compounding into the polyamide-6 matrix prior to injection moulding. Analysis via X-ray photoelectron spectroscopy (XPS) coupled with topological/visual study through scanning electron microscopy (SEM), showed distinct surface changes after modification and at the composite fracture surface. Additionally, mechanical (tensile, flexural, and tribological characteristics) and thermal (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)) investigations were performed. The results showed that the unmodified CF samples exhibit higher tensile and flexural modulus than the modified CF samples. However, the wear rate has been significantly decreased for modified CF samples. SEM of fractured composite surfaces showcased a clear interphase region surrounding the fibre, highlighting the importance of interphase/interphase mechanics in the design of optimal composite interfaces.

Extension of the crack equivalent method applied to mode II fracture of thermoplastic composites bonded joints using the ENF test

Thermoplastic based composites (TPC) have emerged as a new generation of eco-friendly materials with tougher matrices capable of overcoming the major weaknesses of the thermoset counterparts related with poor resistance to delamination and recycling difficulties. Although TPC materials present low surface energy, adhesive bonding is still effective when the requirements for fusion bonding procedures are not met. Recent advances in adhesive technology have unveiled two-part acrylic adhesive specifically designed for low energy surfaces, characteristic of TPC materials. In this work, unidirectional carbon-reinforced polyamide 6 (CF/PA6) bonded joint was characterized under pure mode II loading using end-notched flexure (ENF) test. The experimental fracture tests revealed unstable crack propagation and a data reduction scheme based on the equivalent crack concept was developed to obtain the strain energy release rate distribution along the crack front for the specimen’s length beyond the actuator central loading point. The proposed procedure was successfully validated using a finite element analysis including a cohesive zone modelling and applied to the experimental results. The obtained Resistance-curves showed that this adhesive is capable to provide a significant bonding resistance in pure mode II loading even in low energy surfaces characteristic of TPC materials.

Influence of Al2O3 - nano filler on the Vachellia Nilotica blended hybrid epoxy composites: a comprehensive analysis of mechanical, viscoelastic, and dielectric behavior

This work presents the influence of Alumina (Al2O3) Nano powder on the mechanical, dynamic, and dielectric properties of the hybrid epoxy resin composite material containing Vachellia nilotica (VN). The hand lay up method was used to make the composite specimens at different volume fractions of the alumina nano particle filler (3, 6, 9, 12, and 15 v/v%). The Vachellia nilotica content was kept at 12 v/v% in all the samples remaining being epoxy resin. The experimental results indicate that the composite with 9 v/v% Al2O3 showed better mechanical and dielectric properties when compared to other volume percentages. The epoxy composite with the highest glass transition temperature and storage modulus was also the one containing 9 v/v% nano filler. Furthermore, the dielectric test demonstrated that the addition of the nano filler strengthened the dielectric strength of the composite. The structural morphology of the composite's tensile fracture was investigated using scanning electron microscopy (SEM) to investigate the interaction between the epoxy matrix and the fillers in the hybrid composites.

Assessing the fracture toughness in Tungsten-based nanocomposites: A micro-mechanical approach

Nanocrystalline tungsten-copper composites can favorably combine the outstanding material properties of both elements. This work investigates tungsten-copper composites fabricated from elemental powders with 80 wt.% tungsten and either copper or α-brass containing 20 wt.% zinc, respectively. Moreover, high-pressure torsion is used to compact the powders, strengthen the resulting composite by grain refinement, and tailor the grain-size in the nanocrystalline regime by varying the deformation temperature between RT, 400°C and 550°C, resulting in grain-sizes of 9 nm 14 nm and 28nm, respectively. Hardness measurements revealed a transition from normal to inverse Hall-Petch behavior for grain-sizes below 11 nm. To examine the fracture properties, micro-cantilever bending beams with a cross-section of 10x10µm2 were fabricated. Evaluation of these experiments indicated a fracture toughness of 3 MPam. The slight decrease of fracture toughness between a grain-size of 9 nm to 14 nm indicates a reduction of the grain boundary cohesion strength. The grain-size increase to 28nm reversed the trend in fracture toughness and raised it to 3.4MPam, which points to activating additional deformation mechanisms, such as dislocation-accumulation and twinning. Additionally, alloying with zinc raised the composites strength and retained the composites fracture toughness, benefiting the damage tolerance.

Detecting and evaluating surface defects in additive manufacturing composite materials via image processing technique

Purpose This study aims to offer an image-based robust edge detection system that can estimate, identify, locate and label surface flaws during manufacturing for real-time surface issue diagnostics. Of great concern, this methodology extrapolates surface defect information from scanning electron microscopy (SEM) images of composite fracture surfaces. This study predicts changes in topological intensity of composite fracture surfaces and display them as real-time surface intensity values for the first time. Design/methodology/approach This work, however, introduces a novel robust edge detection method – based image processing – as it is shown to be effective in locating defects, as measured by SEM images of composite fracture surfaces created using additive manufacturing (AM). SEM images, obtained in this study, are related to previous study considering the fracture surfaces of reinforced thermoset composites created via the AM method. These SEM images are of two types: fracture surface of AM of carbon fiber reinforced thermoset composites and fracture surface of AM of syntactic foam reinforced thermoset composites. Initially, MATLAB environment is used for analyzing the SEM images; the technique used, as well as the validity are explained more in the methodology section. Findings The robust surface defect inspection approach used herein is found to be capable of predicting, identifying, localizing and labeling surface defects during production, allowing for real-time surface issue diagnosis. Further, this work makes it possible to use image processing and analysis of these surfaces to anticipate fluctuations in the topological intensity of the fracture surfaces of composites and represent them as values of surface intensity in real time. Originality/value Rising worldwide company rivalry requires a fast, accurate component failure diagnostic method. To create an efficient feature set, a surface defect inspection system must identify product flaws in real time. Thus, this study proposed an image-based robust edge detection system – based on MATLAB environment – that is capable of estimating, identifying, locating and labeling surface faults during production. This paves the way for an extensive set of high-quality tools for dealing with a wide range of problems associated with digital image processing in composites. As a result, the ability to define methodologies and rapidly prototype prospective solutions typically minimizes the cost and time required to implement a successful system during the design phase of an image processing system.

Research on Wellbore Integrity Evaluation Model of CO2 Enhanced Composite Fracturing

CO2 injection composite fracturing is an effective method for shale oil and gas well development. The downhole casing is prone to uniform corrosion, pitting, perforation, and even corrosion fracture in the CO2 environment. Therefore, it is particularly important to reveal the physical characteristics of CO2 under actual geological conditions and the impact of CO2 corrosion on the performance of casing. A mathematical model for the temperature and pressure field of CO2 in the wellbore under fracturing conditions is established in this paper, and the temperature and pressure distribution along the depth of the well is calculated. By optimizing the CO2 state equation and using the S-W equation, Lee model, and RK model to calculate the CO2 density, viscosity and compression factor, respectively, the phase distribution pattern of CO2 along the actual wellbore is obtained. Through CO2 corrosion tests on the casing, the influence of temperature and CO2 concentration on the corrosion rate of the casing is clarified. The peak corrosion rate of Q125 steel corresponds to 80 °C, and the corrosion rate increases with the increase in CO2 concentration. Finally, a prediction model for the uniform corrosion rate of casing under different temperatures and CO2 concentration conditions is obtained, which can provide technical support for the design of CO2-enhanced fracturing technology.

Macro-micro fracture mechanism and acoustic emission characteristics of brittle rock induced by loading rate effect

The deterioration and deformation of brittle rock generally appear in railway tunnels with the operation of large buried deep tunnel. To investigate the macro-micro fracture and acoustic emission evolution characteristics of brittle rock, this paper conducted the uniaxial compression, scanning electron microscope (SEM), and acoustic emission (AE) signal monitoring under different loading rates. The results showed that the loading rate has an obvious enhancement effect on mechanical parameters. The increased loading rate extends the elastic deformation and improves the bearing strength, elastic modulus and deformation modulus. The fracture patterns include shear fracture, composite fracture, and tension fracture. The oblique shear fracture is transformed into composite fracture and tension fracture with the loading rate increasing. The microscopic fracture shows that increasing loading rate inhibits the evolution of oblique shear fractures and promotes the expansion of tensile fractures. The roughness level of tensile fractures is significantly lower than that of oblique shear fracture and composite fracture. The AE parameters and deformation behavior are characterized by simultaneous evolution. The AE amplitude changes from low-level and low-density distribution to high-level and high-density distribution as the loading rate increases. The AE activity intensity of tensile fracture is significantly greater than that of oblique shear fracture and composite fracture. The warning timeliness of cumulative AE events and cumulative AE energy is generally earlier than the AE b-value under the same loading rate, and the early warning timeliness of cumulative AE events is similar to that of cumulative AE energy.

Deformation, fracture, and fatigue crack growth behavior in TiB-reinforced near-α Ti matrix composites fabricated using powder metallurgy technique

Titanium matrix composites with TA15 alloy as the matrix and TiB (ranging from 0 to 4 vol%) as reinforcement were produced via powder metallurgy-based hot press sintering, employing AlB2 precursor. The addition of TiB to TA15 led to a substantial reduction in the colony and prior β grain sizes, and an increase in the lath thickness in the composites. Plastic deformation due to planar slip, which traverses across the α/β-ligament phase boundaries within each colony, may cause TiB particles located on colony boundaries to break, potentially more so than those within the colony. The composite containing 1 vol% TiB exhibited simultaneous improvements in strength, ductility, and strain hardening rate, attributed to colony refinement and possibly a sizable amount of intra-boundary TiB. Further increase in the TiB content led to significant drops in ductility, which was further exacerbated by the precipitation of α2-Ti3Al phase. A substantial decrease in the mode I fracture toughness, attributed to reduced colony size and diminished crack deflection, was noted in the composite with 1 vol% TiB. The colony size refinement also contributed to a reduction in the threshold stress intensity factor range, ΔK0, for the fatigue crack growth, owing to the decreased tortuosity of the fatigue crack front. This study elucidates the intricate relationship between TiB location, microstructure, and mechanical properties, providing insights for the design of TiB-reinforced titanium alloys with both α and β phases.

Molecular Insights into the Topological Transition, Fracture, and Self-Healing Behavior of Vitrimer Composites with Exchangeable Interfaces

Molecular Insights into the Topological Transition, Fracture, and Self-Healing Behavior of Vitrimer Composites with Exchangeable Interfaces

Acoustic Emission Energy Release Rate Model for Classification of Damage Development in Large Fiber Reinforced Plastic Composite Structures

Acoustic emission identification of fracture mechanisms in composite materials is of great importance for the practical assessment of the serviceability of aerospace structures, such as unmanned aerial vehicles, rocket motors, and others. Many scientific research studies conducted in recent decades have demonstrated the unique capabilities of the Acoustic Emission (AE) method to detect and identify different failure mechanisms, including fiber breakage, matrix cracking, and delaminations in fracture tests of composite specimens. However, testing large composite structures, in many cases, can be accompanied by multiple time-overlapped fracture events activated simultaneously, resulting in considerable difficulties in the classification and assessment of combined prolonged AE signals. In this work, we propose the Energy Release Rate (ERR) model for the classification of AE activity related to fiber-reinforced plastic (FRP) composite fracture. The model identifies accurately both micro-scopic and macro-scopic fracture mechanisms in large aerospace structures having complex composition of materials. The model is practically applied using several machine learning methods and provides a simple means to identify and discriminate typical fracture mechanisms and their combinations. Specifically, we describe ERR model, the choice of most informative AE parameters, the choice of suitable machine learning classification methods, their training and testing on FRP specimens, and validating the model in practical tests of large full-size FRP composite structures.

Research and Experiment on Efficient Fracturing Technology of Tight Gas in Qaidam Basin

Abstract The lithology of the Huangguamao block reservoir in the Qaidam Basin is complex and dense. The difference between gas and water is not obvious. The gas reservoir has the characteristics of low porosity, low permeability, low saturation, and coexistence of gas and water. The problem of water output after fracturing and short stable production period has put forward higher requirements for improving production and efficiency in tight gas horizontal wells. Based on successful cases of tight gas reservoir fracturing both domestically and internationally, as well as the experience of unconventional reservoir volume transformation in the Qaidam Basin, this study conducts a historical analysis of reservoir characteristics and measures transformation in the Huangguamao block, evaluates the difficulties of measures transformation, optimizes the formation of two process ideas: high viscosity liquid controlled sand lifting fracturing and reverse composite fracture network fracturing, and prepares fracturing programme for MP2 and MP3 wells. After on-site fracturing, two processes were evaluated and analyzed, and the results showed that the reverse composite fracturing process, which takes into account both crack length and complexity, can effectively increase the transformation volume, provide more sufficient formation energy, increase production, and have stronger adaptability.

Fabrication and comparison of interlaminar fracture toughness behaviour of glass epoxy composites with recycled milled Kevlar-carbon hybrid fillers

Current research uses a novel recycled milled carbon (rmCF), recycled milled Kevlar (rmKF), and innovative Hybrid fillers (rmHF) of both to increase glass/epoxy composite laminate delamination resistance. This study examines how crack propagation and fibre orientation affect laminated composite delamination fracture toughness. Recycled milled Fillers in the interlayer increase stiffness, delamination resistance, and fracture toughness by increasing the energy needed to crack the interlaminar domain. Here, Mode I, Mode II, and Mixed Mode (I/II) with GIGII = 25 %, 50 % and 75 % were studied for four different Interface fibre orientations. It appears [06/902/06] increased delamination toughness. Adding the novel recycled milled fillers improved delamination resistance. Among the three fillers, rmCF increased fracture toughness by 271 % and rmHF and rmKF composites had 220 % and 182 % higher fracture toughness. The synergy compensated for Kevlar's lower fracture toughness in the hybrid (rmHF). SEM analysis of fractured surfaces revealed crack deflection, individual debonding, and filler/matrix interlocking, all of which increase fracture toughness on different levels.