Strength Of Glass Research Articles

Constant-curvature bending response of thin glass: Analytical, numerical and experimental study of “clamp-bending” tests

New generation thin, lightweight and damage-resistant glass, having impressively impact resistance and ability to be bent up to small radii, appears to be the optimal material for extremely deformable structural elements. Its structural use and design require an accurate evaluation of its mechanical properties. However, standard methods to test the glass strength, as the Four-Point Bending and the Coaxial Double Ring test, cannot be used for thin glass, due to its high deformability. Here, an innovative test is proposed, consisting into deforming a thin element into a costant-curvature shape, by prescribing a rotation on two opposite edges of a rectangular plate, while allowing the adjustment of the distance between the supporting hinges. This produces a deformation into an arch of a circle and to a constant stress distribution, allowing to determine the thin glass strength with very simple formulas. An innovative experimental setup, recently proposed for twisting tests on thin glass, has been adapted for constant-curvature bending tests, based on the results of both analytical modelling and numerical analyses. This has been used to perform an experimental campaign, comprising 15 destructive tests on chemically tempered thin glass.

New insights into the interpretation of the results of four point bending tests on float glass

The four point bending test is one of the most commonly used and standardised tests to determine the mechanical properties of materials. For its use on float glass there are both the ASTM C158-02R17 and European EN 1288-3:2001 standards. However when testing float glass the results tend be a statistical muddle. This impacts the reliability of the design strength of float glass determined using four point bending tests. In an attempt to resolve this problem a series of four point bending tests were conducted which were designed to be more systematic than those previously reported in the literature and which use newly developed digital microscopy techniques for pre- and post-test analysis. By systematically testing, the test results can be divided into different groups based on air side, Sn side and source of failure, allowing the data to be divided into clear and separate statistical groups. Secondly the results can potentially be used to validate the lower bound glass strength theory proposed by Ballarini et al. (J Eng Mech 142(12):04016100, 2016). The glass specimens were industrially cut, ground, chamfered and flat polished on the long sides. Specimens were checked using advanced digital microscopy before and after testing. The results suggest that uni-modal Weibull behaviour only applies above a critical failure stress. Failures at stresses below this critical failure stress as a group have a separate and steeper Weibull slope. This supports Ballarini’s theory for a lower bound failure strength although there are important differences between the air side and Sn side of the specimens which this theory does not currently allow for. These differences seem to be inherent to the differences between the glass and the Sn sides. The results also show that the strength of cut, ground, chamfered and flat polished glass can be high but that inconsistency in process control and the irregular occurrence of surface failures are the main causes for the statistical spread. Digital microscopy can reliably measure the quality of the various surfaces and intersections of surfaces of a glass specimen but there is no absolute relation between the size of a detected defect and the probability that this defect actually leads to failure.

Metallic Glasses: Materials for Today and Tomorrow

Abstract Metallic glasses are noncrystalline solid metals that have high strength, excellent corrosion resistance, and impressive hardness compared to their crystalline counterparts. A modern understanding of how glasses are formed along with an appreciation for the high ultimate yield strength of metallic glasses are leading to a boon in applications for these unique materials.

Direct laser patterning of glass mask for micro display using GHz bursts

AbstractDevelopment of high‐precision RGB patterning process is needed to implement high‐resolution micro display (OLEDoS) for next‐generation VR/AR products. In general, specially designed and manufactured masks are required to realize above 3000‐ppi high‐resolution display in structured OLED material deposition. In this study, we developed direct laser patterning IR‐fs optical system operating in MHz and GHz burst modes and evaluated its capability for precise micro‐drilling of aluminoborosilicate glass materials. The fine hole‐shaped pattern is produced at a minimum of 5 μm pitch level for about 0.6 in. area without sacrificing the glass strength. It is expected to contribute to the high precise manufacture of ultra fine mask (UFM) using thin glass platform corresponding to micro displays in the future.

Enhancing mechanical strength of Sr-based oxyfluoride glasses in glass ionomer cement through phase separation

Glass-ionomer cements (GICs) are used in various applications in clinical restorative dentistry. In this study the effect of CaF2 content of the glasses on microstructure, thermal and mechanical behaviors of the synthesized glass ionomer cements was investigated. The results showed that by adding CaF2 at expense of SrF2 the first exothermic temperature (TE) of the glass was reduced from 735 to 704 °C and the compressive strength was increased from 42.0 ± 1.29 MPa to 60.3 ± 1.5 MPa as well. These substitutions led to extending of liquid-liquid phase separation in the glass. The enhancement of mechanical properties demonstrated through the process of annealing glass powder at temperatures below half of the glass transition temperature. This technique contributes to the improvement of mechanical properties by decreasing the residual stress and fostering the separation of amorphous phases. The formation of phase separation appears to be a significant factor in improving the mechanical properties of the oxyfluoride cements.

Modeling via peridynamics for crack propagation in laminated glass under fire

Despite laminated glass is widely used in building construction, its susceptibility to cracking and collapsing during an accidental fire can intensify fire propagation, leading to substantial casualties and economic losses. In this work, we developed a meshfree framework for modeling thermomechanical cracking of laminated glass via peridynamic (PD) theory. First, to overcome the incomplete input experimental data for implementing thermal boundary conditions, we proposed both the uniform and non-uniform temperature field strategies. Second, PD interface model and the stochastic distribution of defects were implemented within this framework. Third, the challenging problem of crack path selection in thermally loaded borosilicate/steel bi-material beams was studied to validate the feasibility of the proposed model. It is demonstrated that the proposed framework can capture the temperature history and crack features of laminated glass under fire, showing great consistency with experimental results. Our findings show that with the decrease of the glass strength or the increase of the defect content, more islands form in the central region of the glazing, implying higher risks of glass fall-out in fire conditions. This model constitutes a promising tool for predicting the fire performance of laminated glass and contributes to designing safer engineering structures.

A New Method for Evaluating the Influence of Coatings on the Strength and Fatigue Behavior of Flexible Glass

Flexible glass is an interesting substrate for a variety of displays, especially bendable or foldable ones, as it shows excellent surface properties and appealing haptics. With the necessary skill, flexible glass can be coated with thin films of different functionality, such as electrical or optical thin films, using plasma processes. In displays, thin film coatings such as transparent conductive electrodes and/or antireflective layer stacks are of major importance. Despite its attractive surface properties, however, flexible glass is still brittle, and its strength must be examined and monitored during any functionalization process, especially with regard to the fatigue behaviour. Currently, specific setups for cyclic fatigue testing of coated flexible glass are not available. Therefore, a new test method is presented herein for easy-to-handle rapid strength and fatigue testing using an endurance testing machine. This method overcomes two issues with the commonly used two-point bending test: the correct insertion of specimens is much easier, and both strength and fatigue testing using the same setup are now possible. Finite element method (FEM) simulation outcomes and first experimental simple fracture tests show that results comparable to those with a two-point bending test setup can be achieved with less effort. This makes it possible to analyze the fracture behaviour of flexible glass under cyclic loading and to evaluate the influence of thin film stress and other coating properties on its performance.Graphical

Assessment on flexural performance of monolithic glass considering spatial and depth characteristics of scratches

Glass products are widely used in building envelopes. Fracture can be triggered accidentally from the glass surface damage such as scratch. This study proposed an approach to assess the flexural performance of the aged monolithic glass panel, which has scratch with spatial and depth information detected via non-contact sensing. The coaxial double ring (CDR) test was conducted for experimentally evaluating the flexural strength on a total number of 160 scratched annealed (AN) and fully tempered (FT) glass specimens. Finite element (FE) analysis was performed to find the exact stress state by considering the geometric non-linear behaviour of glass panel under large deflection. Test and numerical results demonstrate that the scratch depth characterized by a confocal microscope and spatial location can both influence the failure load of FT glass, whereas AN glass is only sensitive to the latter. With combining linear elastic fracture mechanics (LEFM) theory, the relationship between the scratch depth and the residual strength of FT glass can be accurately determined. The spatial and depth characteristics of scratch can then be integrated for the failure load assessment of monolithic FT glass panel. The assessment framework can contribute to the accurate non-destructive assessment on aged architectural glass.

Investigation of Empennage Location Effect to the Unmanned Aerial Vehicle (UAV) Structure Characteristic

Over the past few decades, unmanned aerial vehicles, commonly known as UAVs, have been widely used in a number of consumer and military applications, such as surveillance, tracking, monitoring, and aerial photography. Fixed-wing and rotary UAVs are the two primary categories in UAV. Interestingly, the hybridization of fixed-wing and rotary UAV gives better performance in terms of energy consumption and the needs of runaway. Designing new hybrid fixed wing-rotary UAV or hybrid vertical take-off and landing (VTOL) is challenging especially to identify the critical location in the UAV and material selection. Therefore, the objective of this research is to study the effect of empennage location and material selection on the structural strength of a hybrid VTOL UAV. The SolidWorks software was employed to design a 3D model of the UAV with different empennage locations, as well as perform a simulation of the structural strength of fibre glass, carbon fibre and kenaf for the hybrid VTOL UAV. The simulation analysis presents stress (Von Mises). The results show that the fibre glass (4.342 N/m2) at top empennage gives the best performance as compared to other parameters. In conclusion, this study is necessary to give a better picture of structural strength of composite materials and best design location in hybrid VTOL UAV for future research.

Low‐temperature bonding of glasses: The role of plasma‐engrafted surface amino groups

AbstractLow‐temperature (<∼200°C) bonding of glasses is a key technology for utilizing them for microfluidics, optical applications, and microelectromechanical systems. In the present study, bonding strength of SiO2 glasses was examined for those after several surface treatment methods. As a result, it was found that two‐step (H2O→ NH3) plasma treatment remarkably strengthened the bonding strength (>1 J/m2) at the annealing temperature of 150°C. The improvement was achieved even when only one side of the bonded surfaces was plasma‐treated. X‐ray photoelectron spectroscopy revealed that the two‐step plasma treatment generated Si–NH2 groups on the topmost surface. Upon the annealing (<200°C), the engrafted Si–NH2 was desorbed from the bonded interface, indicating that the Si–NH2 effectively reacted with Si–OH on the other side to form Si–O–Si covalent bonds. This study contributes to understanding of the role of surface functional groups for bonding reaction. Furthermore, the method proposed here would be promising as a production technology because it enables glass bonding at lower temperatures with a simple plasma system.

The strength of uncoated and coated ultra-thin flexible glass under cyclic load

<abstract> <p>Ultra-thin flexible glass with thicknesses of 100 µm or below is a substrate in the fields of optics, electronics, and semiconductors. Its brittleness is challenging in production processes like physical vapor deposition processes, especially in roll-to-roll production. In many cases, multiple geometric deformations take place and each step, like coating or cutting, influences the glass strength. By now, the relation between the strength of ultra-thin glass under quasi-static conditions and its strength under cyclic load has not been studied. Moreover, the effect of coatings has not been investigated. Both aspects are crucial to design reliable production processes. Therefore, the strength of ultra-thin glass under cyclic load was studied for uncoated and coated substrates. Two coating types were investigated: a single indium tin oxide film and a seven-layer antireflective layer stack. The coatings significantly influence the strength of the underlying glass in both test modes. The barrier properties, thin film stress, and the morphology/crystalline structure are identified as the major characteristics influencing the strength.</p> </abstract>

Analysis of the effects of vickers indentation-induced defects on the strength and probability of failure of float glass during biaxial flexure testing

This study examines the impact of indentations on the strength of float glass. Using the Vickers indentation method with loads of 1N and 10N, we created defects at varying distances from the point of contact. Biaxial flexure tests revealed that indentations with 1N at 18mm decreased the strength, while those with 10N and shorter distances from the point of contact increased the strength. Weibull distribution analyses showed a correlation between the load, distance, and the Weibull modulus, highlighting the influence of defect size on the probability of rupture.

Experimental evaluation of scatter in fracture stress of silicate glass and its thickness dependence

Glass is widely used in various structural application, where a transparent, durable, and stiff material is needed. Although glass is primarily not a load-bearing member in applications, however, even in common usage of glass as windows panes it is exposed to loads, such as wind loads, thermal and other mechanical loads, and may also be exposed to vibratory, impact and blast loading. However, these materials are brittle in nature and cannot withstand thermal loads beyond a certain limit. Moreover, there is a substantial scatter in their fracture stress and the median values of fracture stress is dependent upon the thickness of the specimen used in the tests. In order to study the effect of specimen thickness on fracture stress and its scatter, several experiments have been conducted on different thickness of glass material. Three point bend test was conducted on various glass specimens of 4 mm and 8 mm thickness to ascertain the scatter in the fracture strength of the glass specimen. A lot of scatter in the fracture strength of the glass specimen was observed which is attributed to the presence of micro crack on the surface of the glass specimen. Scatter in fracture stress is higher for 8 mm thickness of glass as compared to 4 mm glass specimen. It was seen that the cumulative experiment probability of fracture strength of glass follows a Weibull model. It was seen that the fracture strength of the glass reduces from 46 MPa to 40 MPa with the increase in thickness from 4 mm to 8 mm respectively indicating the decrease in fracture toughness with increasing thickness.

Simulation‐based analysis of weld line strength of glass fiber‐reinforced polymer in injection molding

AbstractThe injection molding market is expected to grow with the increasing demand from various industries, such as automotive and furniture. However, weld lines in the injection molded part reduce the structural strength and affects its appearance. This study evaluates the effect of the weld line on the structure by shifting the position of the weld line outside the area where the load is applied by manipulating the opening time of the injection gates. We examined the effect of weld lines on the strength of a chair through coupled resin flow and structural analyses. The analysis revealed that the position of the weld lines is crucial for structural strength if the knockdown factor (KDF) is low. Additionally, controlling the opening time of the gate and shifting the position of the weld line improved the structure's appearance, number of weld line and avoid the lower meeting angle. However, depending on the material, the effect may be weak. For example, when the weld line location did not change much despite changing the gate timing, little change was observed in the number of weld lines. Hence, the improvement strategy of weld line should be considered for material types and strength.Highlights Injection molding growth driven by automotive, packaging, furniture demand. Weld lines impact structural strength and appearance. Shifting weld line position outside load area improves the structural appearance and strength. Effects of shifting weld line position depended on the material types. Weld line position is crucial for low knockdown factor and affects strength.

Tuning dynamic mechanical properties of Cu50Zr50 nanoglasses/ nanopolycrystalline Cu composites investigated by molecular dynamics simulation

Nanoglasses/nanopolycrystalline (NGNP) composites have emerged as a promising approach to balance the strength and plasticity of metallic glasses. Herein, the shock responses of five Cu50Zr50 NGNP composites are investigated via molecular dynamics simulations under a shock velocity of 0.5 to 2.0 km/s. The simulation results reveal that with an increasing fraction of nanocrystalline grains, the Hugoniot pressure, shear stress, and spall strength of the composites are enhanced, while their atomic strain decreases under shock loading. Additionally, due to the dominant structure type changes from an amorphous structure to a crystal structure, the deformation mechanism transforms from the growth of shear transformation zones to dislocation slip, phase transition, and amorphization as the impact velocity increases. In terms of the spallation, the spall strength of the composites rises initially and then declines due to the competing mechanisms of strain rate hardening and shock-induced softening.

Analysis of Topography, Flexural Strength, and Microstructure of a Lithium Disilicate Glass- Ceramic after Surface Finishing.

To investigate the influence of finishing, polishing, and glazing on the roughness, flexural strength, and microstructure of lithium disilicate glass-ceramics. LD CAD/CAM blocks were cut into 96 discs (1.2 × 12 mm). After crystallization, a layer of glaze was applied to the discs' surfaces. The specimens were randomly divided into eight groupsn = 12) for different surface treatments (glaze [G], diamond abrasion [D], find diamond abrasion [F], and polishing [P]): G(glaze, control), GD, GDG, GDP, GF GFG, GFP, and GDFP. Mean roughness (Ra), mean square height (Rq), and maximum roughness (Rz) were measured. The biaxial flexural strength test was performed in a universal testing machine at 0.5 mm/minute. Microstructural analysis was performed using x-ray diffraction patterns (XRD). Differences on the roughness obtained in distinct groups was analyzed with Kruskal-Wallis and Bonferroni tests (α = .05). The flexural strength tests were compared with one-way ANOVA. Glazed groups (G, GDG, and GFG) presented the lowest surface roughness, lower crystallinity, and higher flexural strength than the other groups. Although polishing and glaze presented similar surface roughness, polishing protocol decreased the flexural strength compared to the control group G. Clinically adjusted LD glass-ceramic restorations should be reglazed whenever possible to improve strength.

A physically based strength prediction model for glass

The strength of glass has been a subject of great interest for more than one hundred years. Due to the stochastic nature of glass, governed by microscopical surface flaws, glass plates exhibit large variations in fracture strength. The aim of this work is to propose a new strength prediction model for glass, named the Glass Strength Prediction Model (GSPM) that captures the nature of fracture initiation in glass, spanning from rate dependence to size effects. We aim for the presented model to be applicable in modern design processes and provide a procedure to facilitate input parameter calibration for glass plates from different suppliers. GSPM is a Monte-Carlo based model that combines the theories of linear elastic fracture mechanics (LEFM) and sub-critical crack growth (SCG) to generate virtual tests on a representative sample of glass plates. The stress evolution in the glass plates is obtained from finite element (FE) simulations. The model results in representative fracture strength distributions that span the probable fracture initiation instances with respect to time, location and stress level. We also demonstrate how the GSPM can be used to trigger fracture in constitutive models applied in FE simulations. This feature provides the option to investigate scenarios including multiple glass plates with interdependent fracture initiation behavior. The GSPM displays great promise in terms of usability and prediction capacity. It is able to capture the fracture initiation behavior of glass plates of varying geometries exposed to load cases spanning from, e.g., quasi-static four-point bending to blast pressure. The model has the potential to reduce the number of physical experiments and numerical FE simulations in modern development processes of glass structures.

Effect of Interfacial Chemical and Physical Bonding on The Interfacial Shear Strength of Glass Fiber/Polyamide Resin and Mechanical Properties of The Composites

Effect of Interfacial Chemical and Physical Bonding on The Interfacial Shear Strength of Glass Fiber/Polyamide Resin and Mechanical Properties of The Composites

Investigating the Lifetime Performance Index under Ishita Distribution Based on Progressive Type II Censored Data with Applications

In manufacturing sectors, product performance evaluation is crucial. The lifetime performance index, denoted as CL, is widely used in product evaluation, where L signifies the lower specification limit. This study aims to refine the estimation of CL by employing maximum-likelihood and Bayesian methodologies, where symmetric and asymmetric loss functions are utilized. The analysis is conducted on progressive type II censored data, a requirement often imposed by budgetary constraints or the need for expedited testing. The data are assumed to follow the Ishita distribution, whose conforming rate is also evaluated. Furthermore, a hypothesis testing framework is employed to validate whether component lifetimes meet predefined standards. The theoretical findings are corroborated using real data collected from glass strength in aircraft windows. The numerical analysis emphasizes the goodness of fit of the Ishita distribution to model the data, thereby demonstrating the applicability of the proposed distribution.

Multiphysics modeling of subcritical crack growth in glass

Subcritical crack growth starting from flaws on glass surfaces/edges causes slow degradation in glass strength. This phenomenon involves multiple physics and is very challenging to predict. In this work, we introduce a novel multiphysics model for subcritical crack growth in glass. This model considers water-assisted stress relaxation, stress-dependent chemical reaction between water and glass, diffusion of water to the crack tip, and reaction-driven slow crack growth. Stress relaxation is achieved by using a Prony series in the bond-based peridynamic viscoelastic model, and a new bond breakage criterion based on the concentration of reaction product is introduced. A displacement-loaded double beam with a pre-crack is used to obtain the crack velocity vs. stress intensity factor (v-K) curve. With proper simplifications and assumptions, v-K curves obtained from the model successfully reproduced their typical patterns in experiments. This model will help us better understand fundamental mechanisms and make predictions for subcritical crack growth in glass.