Glass Fracture Research Articles

FEM, DEM and FDEM applications on impact fracture of glass and laminated glass – a review

Structural glass components are prevalently used in engineering. Due to the brittle nature, glass or laminated glass may fracture during an impact action, and the subsequent flying fragments may spread over a wide range, resulting in human injuries and asset losses. In this article, the authors aimed at providing a comprehensive review concerning the numerical applications on the impact fracture of glass and laminated glass, giving emphasis to the literatures published in the last two decades. Relevant numerical applications employing the finite element method (including element deletion method, extended finite element method and some other continuum-based approaches), discrete element method and combined finite-discrete element method were reviewed in-depth, and features of the simulations were summarised. Discussions on the impact fracture characteristics from different computational approaches were performed. Insights into the accuracy, efficiency, ease of implementation and range of applicability were also provided. This review is meant for the rapid and beneficial understanding towards the impact fracture mechanism of glass and laminated glass.

Low‐temperature bubble formation in silica glass

AbstractPhase separation was observed in silica glass following low‐temperature heat treatment in high water vapor pressure through the formation of bubbles. Although the 6 day diffusion treatment in saturated water vapor pressure at 250°C does not normally cause phase separation, the reactive fracture surface and subsurface damage caused by polishing with cerium oxide (CeO2) allowed for an increase in water absorption during treatment and heterogeneous nucleation of the bubbles at damaged sites. The sub‐surface damage, characteristic of blunt contact damage, was only revealed when the polished sample was etched. The formation of bubbles and polishing damage were observed in two silica glasses—one containing chlorine impurities and the other containing OH impurities. Raman spectra collected after fracture or polishing and water diffusion treatment demonstrated an increase in the abundance of –OH species including silanol (SiOH) groups and an evolution in the glass structure in the bubble regions compared with the bubble‐free regions. These results indicate an increase in the reactivity between water and glass fracture surfaces relative to the bulk.

Performance of photovoltaic panels with different inclinations under uniform thermal loading

Integrating photovoltaic (PV) panels with different tilt angles in building envelopes or roofs is widely employed for environmental sustainability. However, little is known about the influence of different tilt angles on the thermal failure of the photovoltaic façades or roofs in fire conditions. A total of 15 four-edge shielded PV panels (300 × 300 × 4.7 mm3), with five different inclinations of 0°, 15°, 30°, 45° and 60°, were heated to fail using a uniform radiant panel. Measurements were taken to track glass thermal breakage, surface temperatures, incident heat flux and failure characteristics. The glass fracture and pyrolysis of the internal thermoplastic materials were observed under thermal radiation. The average breakage time of glass in PV panels showed an increasing trend with increasing inclination of the PV panels. Moreover, when the PV panels were tilted beyond 30°, the time to failure increased more significantly. The maximum temperature difference and heat flux that the PV panels can withstand were primarily measured within the range of 61–84 °C and 8–15 kW/m2, respectively. Finally, the test results were simulated by a finite element method (FEM) model, calculating the heat transfer and thermal stress of PV panels: the average errors concerning temperature distributions and failure times were smaller than 15 % compared with the experimental results.

Investigation on Polyether Sulfone Toughening Epoxy Vitrimer: Curing and Dynamic Properties.

Diglycidyl ether of bisphenol A crosslinking with glutaric anhydride is used to form the conventional "covalent adaptive network", polyether sulfone (PES) by coiling and aggregating on the adaptive network is used to significantly increase the uncured resin viscosity for improving the processability of epoxy resin, but inevitably affecting the curing reaction and dynamic transesterification reaction. This study investigates the crucial roles of PES in curing dynamics and stress relaxation behavior. The results indicate that although PES does not directly participate in the crosslinking reaction of polyester-based epoxy vitrimers. Moreover, the isothermal curing studies reveal that the addition of PES can greatly bring forward the reaction rate peak from conversion α = 0.6 to α = 0.2, meaning that the curing mechanism transfers from chemical control to diffusion control. Dynamic property analysis shows that the addition of PES significantly accelerates stress relaxation, especially at lower temperatures, leading to low viscous flow activation energy Eτ and relatively insensitive stress relaxation behavior to temperature. Introducing PES into vitrimer resin greatly improves crosslinking density (2.31×10⁴molm- 3), enhancing glass transition temperature (82.68°C), tensile strength (68.66MPa), and fracture toughness (6.25%). Additionally, the modified vitrimer resin exhibits satisfying shape memory performance and reprocessing capability.

Inverted Glasses As Ductile Lithium Ion Conductors for Solid State Batteries

Inorganic electrolytes for solid state batteries with Li metallic anodes must combine properties such as high ionic conductivity, chemical stability, and resistance to failure due to propagation of Li dendrites. Abundance of experimental evidence suggests that cracking of the solid electrolytes due to pressure exerted by lithium plating into the material defects is the primary source of failure [1]. This is due to inherent brittleness of the ceramic ionic conductors, i.e. their inability to reduce stress by means other than fracture. Unlike ceramics, plastic deformation in glass can be achieved via shear and (or) by densification. Both mechanisms can be operational in glasses with reduced content of glass formers relative to the content of glass modifiers – i.e. inverted glasses. Using the example of lithium phosphorous oxynitride, Lipon, we demonstrate how these two mechanisms are capable of accommodating applied stress while avoiding creation of new surfaces by cracking. We investigate the resistance to fracture in Lipon-like glasses and the underlying connection to their composition via instrumented nano-indentation, Raman spectroscopy, and numerical simulations. We observe enhancement of isochoric shear with increase of Li content, similarly to the reports of increased plasticity in sodium aluminoborate glases with high alkali content [2]. Nano-indentation demonstrates that Lipon is extremely resistant to fracture, compared to other inorganic solid electrolytes [3].[1] Porz, T. Swamy, B.W. Sheldon, D. Rettenwander, T. Fromling, H.L. Thaman, S. Berendts, R. Uecker, W.C. Carter, Y.-M. Chiang, Mechanism of lithium metal penetration through inorganic solid electrolytes. Adv. Energy Mater. 7, 1701003 (2017)[2] Sellappan, T. Rouxel, F. Celarie, E. Becker, P. Houizot, R. Conradt, Composition dependence of indentation deformation and indentation cracking in glass. Acta Mater. 61, 5949–5965 (2013)[3] Kalnaus, A. Westover, M. Kornbluth, E.J. Herbert, N.J. Dudney, Resistance to fracture in the glassy solid electrolyte Lipon. J. Mater. Research, 36, 787-795 (2021)

Atmospheric Pressure Plasma Treatment of Glass Surface and Its Influence on the Reliability of Adhesive Bonding

Glass load-bearing structural elements are currently used more often in civil engineering. However, due to the brittle fracture of glass, it is necessary to design these structures with sufficient reliability. Adhesive joints have a number of advantages over mechanical connectors of glass commonly used in construction. Adhesives can eliminate thermal bridges and provide a more uniform stress distribution along the connection without weakening the bonded material.A variety of chemical methods have been developed for cleaning and activating glass surfaces prior to adhesive bonding. Recently, these methods have been substituted by glass surface cleaning and activation using ambient (humid) air plasma. Such an approach is considered much faster, technically simpler, and more environmentally friendly than the traditional chemical methods. For example, it eliminates the need for the so-called primer interlayer, where the primer is usually considered a heavy chemical with significant environmental impact.The presented work is focused on the surface activation of glass by atmospheric pressure plasma to improve adhesion using specially selected transparent adhesives. We studied Diffuse Coplanar Surface Barrier Discharge (DCSBD) plasma treatment of different float-glass, heat-treated and tempered glass surfaces in ambient air. The DCSBD plasma effect was evaluated by surface free energy and peel-test adhesion measurements. The morphological changes on the glass surface were investigated by scanning electron and atomic force microscopy. The glass-to-glass adhesion at elevated temperatures was tested with respect to the artificial ageing of adhesive bonding due to the environment. Acknowledgement: This research was supported by project LM2023039, funded by the Ministry of Education, Youth and Sports of the Czech Republic and supported by project No. GA23-06016S, funded by the Czech Science Foundation (GAČR).

Optical properties of Ce: GdYAG phosphor in glass with high quality LAS glass system and its application in laser illumination

Nowdays, the demand for high-power laser lighting applications is on the rise, however, phosphor in glass (PiG) prepared using conventional glass systems often experience damage under intense laser irradiation. To tackle this issue, we introduce a novel LAS glass system for phosphor encapsulation to create PiG, and by utilizing a spray coating technique, we blend PiG with high thermal conductivity sapphire to obtain phosphor in glass film (PiF), effectively improving laser irradiation resilience and optical characteristics. In this study, a novel LAS glass system (SiO2–Li2CO3–MgO–Al2O3–CaO–P2O5–K2O–ZrO2–Na2O) was utilized to encapsulate Ce:GdYAG phosphors to prepare a series of PiG and PiF. The glass system exhibits multi-directional interlocking lithium disilicate crystals, significantly enhancing the glass's strength and fracture toughness. There is no apparent interface reaction between the glass system and the phosphors, indicating effective protection of the phosphor particles. The PiF sample demonstrates a minor decrease of 5.2 % in internal quantum efficiency compared to the original phosphor, while boasting a high thermal conductivity of 7.4 W m−1 K−1. Notably, the optimized PiF shows remarkable enhancements with a saturation threshold of 4.37 W mm−2, surpassing PiG (1.668 W mm−2), and achieving LFmax of 424.41 lm and LEmax of 147.16 lm W−1. It features a high color rendering index (CRI) of 68.7 and low color correlated temperature (CCT) of 3646 K, significantly improving laser irradiation resistance and optical quality, making it a promising warm yellow laser illumination converter for diverse lighting applications.

Nacreous Glass Composites with Superior Performance Engineered through Mechanical Vibration and Silanization

AbstractBioinspiration offers alternative solutions to overcome the inherent drawbacks of glass, such as low fracture toughness, strength, and impact resistance. Synthetic composites inspired by natural materials, such as nacre, have been recently introduced as an alternative to glasses. However, these have all suffered from trade‐offs between rigidity, optical clarity, fabrication scalability, and complexity. Here, two wave‐based fabrication techniques are presented to create a nacreous structure from glass flakes and polymethyl methacrylate. The glass's surface energy is controlled by adjusting the silane coverage on the glass surface, enabling high levels of structural compactness, mechanical properties, and optical clarity. The scalable glass composite, with a ≈60% glass volume fraction, possesses strength, fracture toughness, and impact resistance values, outperforming annealed glass by 4300%, 350%, and 400%, respectively. It also has a haze level of ≈18%, almost 60% less than that of the similar centrifuged‐based glass composite. This composite is proposed as a potential glass alternative in diverse applications.

Crack segmentation for high-speed imaging: detection of fractures in thermally toughened glass

Fracture morphology characterization in broken glass panes is crucial for designing laminated safety glass (LSG) in civil engineering. Verifying completely broken LSG systems requires destructive sampling, increasing costs and hindering development. Therefore, to determine the residual load-bearing capacity, the link between the pre-fracture characteristics and the fracture morphology must be known. However, when the crack propagation needs to be directly captured with high-speed imaging, conventional methods are no longer sufficient for detecting cracks. To enable such investigations, we propose a novel machine learning framework for crack segmentation in high-speed imaging that addresses the complexity of glass fracture and minimises the required labour costs. In this study, the crack propagation of a sample was recorded and analysed at 2,000,000 images per second. The results showcase accuracies surpassing 97% while requiring only two labeled images for training, thus streamlining practical implementation. Furthermore, we show the method's robustness to the extent that hyperparameter tuning becomes unnecessary. Instead, we offer guidelines for selecting the most crucial hyperparameters depending on the problem. Our method offers a promising approach for non-linear temporal interpolation of noisy images, with implications for various applications extending beyond glass fracture analysis.

Atomic force microscopy monitoring of subcritical slow crack growth in soda lime silicate glass

Prediction of brittle fracture in silicate glasses requires a fundamental understanding of slow crack growth rates, far below the critical stress intensity (KIC) of the material. Here, atomic force microscopy (AFM) was used to characterize slow crack propagation in soda lime silicate glasses. Using large-sample AFM systems with specialized tips and scanners, fractures less than 20 nm wide were measured as a function of relative humidity (RH). The results were found to be sensitive to the type of AFM tip used and to the dryness of the surface. Continuous scanning and image capture over several days allowed the determination of the crack tip velocity. The dependance of crack tip velocity on RH was measured by enclosing the sample and AFM head in a humidity-controlled chamber. The crack tip velocity was measured as low 4.0×10-12 m/s at 15 % RH and as high as 3.7×10-10 m/s at 40 % RH. Overall crack growth was smooth during the AFM scan. Additionally, recession of the crack tip was noted as the sample dried, indicating crack tip closure may be occurring. Further studies on alternative compositions will provide details on subcritical fracture processes in a range of different environmental conditions.

Mechanism of chip segmentation transition from shear slip to shear fracture of Zirconium-based bulk metallic glass in mechanical machining

An in-depth understanding of material cutting deformation forms the foundation for manufacturing Zirconium-based bulk metallic glass (Zr-based BMG) parts. This study explores the transition in chip segmentation mode from shear slip to shear fracture in Zr-based BMG during mechanical machining. The investigation covers chip micromorphology, cyclic cutting force, machined surface quality, and the themo-mechanical properties under various chip segmentation modes linked to cutting conditions. A size-dependent transition in chip segmentation has been observed in the cutting of Zr-based BMG. At a specific cutting speed, a smaller uncut chip thickness favors chip formation via shear slip, resulting in a smooth primary shear zone (PSZ). Conversely, a larger uncut chip thickness leads to chip shear fracture, with the PSZ displaying fishbone-like and dimple patterns. The integration of the modified cutting kinematic model with the free volume-dependent shear transformation zone (STZ) model suggests that the transition from shear slip to fracture is due to an increase in uncut chip thickness, which causes a greater STZ volume in the PSZ. When the STZ volume surpasses a threshold, the intrinsic structural recovery of material from shearing cannot fully compensate for the free volume softening, leading to excessive free volume that ultimately triggers shear fracture. During the chip shear fracture process, the evolution from fishbone-like patterns to dimples in the PSZ is attributed to faster crack propagation at greater uncut chip thickness or higher cutting speeds. In practical applications, it is advisable to avoid chip shear fracture during machining to maintain high-quality machined surface quality.

Microcantilever investigation of slow crack growth and crack healing in aluminium oxide

Slow crack growth (SCG) plays an important role in the fracture of ceramics and glasses. A full understanding of the long term reliability of ceramic components therefore requires knowledge not only of fracture toughness (Kc) but also characteristics of SCG such as the threshold stress intensity factor (K0) of individual microstructural features. Previous investigations have been limited by the small scale of the microstructure and low crack growth rates involved. Here, the stress intensity factors for crack propagation Kp in sapphire were measured continuously under stable crack growth using chevron-notched microcantilevers, in air and in vacuum. Kp in vacuum was considered close to the fracture toughness Kc, with a value of 2.8 ± 0.1 MPa m1/2 for the a-plane of sapphire. Kp in air at 54 % relative humidity was reduced substantially by moisture-assisted SCG to around 1.7 MPa m1/2 and, with crack velocities of ∼20 nm/s, was considered to be close to K0. Cyclic loading in vacuum enabled quantitative measurements to be made during repeated crack growth and healing for the first time. Cracks healed up along their full length when unloaded but exhibited severe degradation of toughness on reloading. The toughness fell from 2.8 MPa m1/2 on the a-plane of pristine sapphire to 1.6 MPa m1/2 after one healing cycle and to successively lower values after further cycles. This technique offers a powerful method of investigating SCG and crack healing at the microstructural scale in different environments, with greater accuracy and on shorter timescales than can be achieved in macroscopic tests.

REUSING MANUFACTURING WASTES AS CRACK RETARDANT

Global production uses millions of metric tons of metals. The waste of these metals can be recycled to increase the economic benefit and lessen the negative impact on the environment. In this work, a manufacturing waste is used as a reinforcement material for epoxy to improve the fracture toughness and the stress intensity factor, where the machining chip is used with different weight fractions 5, 10, 15 and 20 wt. % and each percentage is added with three chip lengths 0.6, 0.8 and 1.18 mm. Three-point bending test of notched sample is used to test crack behaviour in addition to using Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), Differential Scanning Calorimeter (DSC) and Scanning Electron Microscope (SEM) to show the effect of chip on structure, bonding, glass transition temperature (Tg), dispersion and fracture surface of the epoxy. Results show that adding the machining wastes in the form of chips can enhance crack behaviour, and it is greatly dependent on the amount and size of chip. On the contrary, these chips change the glass transition temperature and change the fracture surface from brittle to ductile, thereby reducing the velocity of crack growth.

Criticality in the fracture of silica glass: Insights from molecular mechanics.

The universality of avalanches characterizing the inelastic response of disordered materials has the potential to bridge the gap from micro to macroscale. In this study, we explore the statistics and the scaling behavior of avalanches occurring during the fracture process in silica glass using molecular mechanics. We introduce a robust method for capturing and quantifying these avalanches, allowing us to perform rigorous statistical analyses, revealing universal power laws associated with critical phenomena. The influence of an initial crack is explored, observing deviations from mean-field predictions while maintaining the property of criticality. However, the avalanche exponents in the unnotched samples are predicted correctly by the mean-field depinning model. Furthermore, we investigate the strain-dependent probability density function, its cutoff function, and the interrelation between the critical exponents. Finally, we unveil distinct scaling behavior for small and large avalanches of the crack growth, shedding light on the underlying fracture mechanisms in silica glass.

Point-fixed connections in structural glass with injection mortar infill. experimental investigation and numerical simulations

This paper focuses on the experimental and numerical study of the performance of point-fixed connections in structural glass panels. For that purpose, an experimental program of in-plane uniaxial compressive tests was conducted on small-scale specimens. The specimens were manufactured using monolithic and laminated heat-strengthened glass (HSG). The point-fixed connections were realized using two infill products: (a) fischer FIS V Plus and (b) Hilti Hit HY270. A Digital Image Correlation (DIC) based measurement system in combination with strain gauges is used for tracking kinematics and deformations of the investigated specimens. It was found that the performance of the two infill products is comparable. The tests demonstrate that the failure mode of the monolithic panels is governed by infill failure, whereas the failure of the laminated panels is controlled by glass fracture. The numerical study was performed to assess the stress distribution around the hole in laminated glass. A 3D Finite Element (FE) model built in Abaqus is validated based on DIC and strain gauge measurements. A sensitivity analysis was performed on the eccentricity in the laminated glass panels and the friction coefficient between infill and glass/steel. It was observed that the eccentricity in the laminated panels has a significant influence on the stress amplification in the panels. Also, it was found that the value of the friction coefficient can significantly change the distribution of the principal stresses around the hole.

Aromatic amino acids as latent, bio‐based curing agents and toughening agents for epoxy resins

AbstractIn the realm of bio‐based curing agents, recent investigations have focused on amino acids owing to their distinctive attributes. Nevertheless, the suitability of thermosets cured with aromatic amino acids as latent matrix materials for fiber‐reinforced composites remains to be empirically established. Consequently, this study is oriented toward assessing the mechanical properties of diglycidyl ether of bisphenol A when cured with either L‐tryptophan or L‐tyrosine, in the presence of a latent, urea‐based accelerator. The investigated properties include glass transition temperatures, tensile, flexural, compression, and fracture toughness properties. The predominant variations in the mechanical characteristics of these thermosets are confined to their Young's moduli and fracture toughness properties. This divergence is attributed to the greater presence of crystals in the L‐tyrosine‐cured thermoset, resulting in enhanced reinforcement and toughening effects compared to the L‐tryptophan‐cured thermoset.

Continuous Feed Grinding Milling Process of Soda-Lime Glass Using Smoothed-Particle Hydrodynamics

A smoothed-particle hydrodynamics (SPH) modeling technique was applied in conjunction with the Johnson–Holmquist (JH-2) ceramic material constitutive model to replicate the fracture of soda-lime glass in a milling manufacturing process. Four-point bending tests were conducted to validate the soda-lime glass bulk material properties prior to its implementation in ABAQUS CAE™ Explicit (Version 2017). The JH-2 material constitutive model replicated the fracture load and time to fracture for the four-point bending load cases as per ASTM C158. This study showed how SPH in combination with a validated JH-2 material model in a milling process simulation was able to replicate the output size distribution at 5000 and 6500 revolutions per minute (RPM). For operations at 3000 RPM or lower, it was shown that it is necessary to include additional effects in the model, such as fluid–structure interactions, to improve the correlation with the experimental data. The SPH model was validated through an experimental campaign using high-speed cameras and a particle Camsizer. The experimental results clearly indicate a direct relation between the mill’s RPM and the output particle size distribution.

Influence of embedded steel mesh inserts on post-breakage capacity of laminated glass

Glass, as a building material, has been known for a long time. The first glass uses were limited to filling window frames. However, in recent years, the popularity of glass in construction has increased significantly. All this is due to the growing trend to bring as much natural sunlight into the buildings as possible. The increasingly popular treatment of glass as a construction material requires using laminated glass, in which a film permanently joins together two or more glass panes. This unique behaviour is because the film between the glass sheets holds the glass fragments in place when they are fractured. In this way, avoiding the risk of injury to people in the vicinity is possible. As part of the ongoing project, “Innovative solution for point-fixed laminated glass with improved capacity after glass fracture” financed by the National Center for Research and Development (NCBR) within the LIDER XI Program, an idea of laminating a steel woven mesh to glass laminates is being investigated. The steel mesh insert is designed to increase the load-bearing capacity of the sample in the post-breakage phase, thus increasing the safety of building occupants. The article deals with the post-breakage capacity of laminated glass elements subjected to three types of loading: in-plane, out-of-plane and combined actions.

Comprehensive investigation into the thermal rheological behavior and relaxation characteristic of single/composite polymers in laminated glass

Polymeric interlayers are of significance for the structural capability of thin-walled laminated glass members both before and after glass fracture. Polymers present evident temperature and time dependence, which should be carefully assessed in the design process. To improve mechanical properties dependent on the temperature and time, novel interlayers including modified ethylene-vinyl acetate (PVE®) and composite PVE/PC (SGE®), have been developed along with the sound resistance of the interfacial adhesion to aging. In this work, dynamic mechanical thermal analysis tests were carried out to investigate the thermal rheological behavior and relaxation characteristic of polyvinyl butyral (PVB), ionomer (SentryGlas®, SG), PVE, PC and SGE. The results show that PVE and SGE follow the complex thermal rheological behavior as a result of the existence of two different types of relaxation transitions, whilst PVB, SG, and PC are thermorheologically simple materials. The arctangent function was introduced to describe the temperature dependence of PVB and SG. The relaxation modulus of polymers was subsequently derived based on the approximation equation and inverse Fourier transform. The results of the inverse Fourier transform indicate that vertical shift might need to be considered for PVE and SGE. The application of the approximation equation was assessed and its limitation was discussed. Finally, the relaxation characteristics of five polymers were described using the generalized Maxwell model based on the weighted least squares method.

Silicate glass fracture surface energy calculated from crystal structure and bond-energy data

We present a novel method to predict the fracture surface energy, γ, of isochemically crystallizing silicate glasses using readily available crystallographic structure data of their crystalline counterpart and tabled diatomic chemical bond energies, D0. The method assumes that γ equals the fracture surface energy of the most likely cleavage plane of the crystal. Calculated values were in excellent agreement with those calculated from glass density, network connectivity and D0 data in earlier work. This finding demonstrates a remarkable equivalence between crystal cleavage planes and glass fracture surfaces.