Monolithic Glass Research Articles

Creation of a 3D Glassy State by Thermal Gradient Treatment in a Monolithic Metallic Glass

Creation of a 3D Glassy State by Thermal Gradient Treatment in a Monolithic Metallic Glass

Numerical simulation of anti-shatter films (ASF) for mechanical post-breakage analysis of retrofitted glass

Post-breakage strength and residual mechanical capacity improvements are important tasks for load-bearing structural components in general, and even more for glass elements, in order to protect people from injury in case of breakage. For this reason, among others, the design of glass components and structures is based on key concepts that are generally summarized in structural safety, robustness and redundancy. With regard to the last fundamental requirement, nowadays the use of laminated glass (LG) sections is spread for many applications and new projects, such as automotive or aircraft windshields, but especially curtain walls and many other load-bearing applications in buildings. This strategy derives from the intrinsic safety and security levels of LG sections after possible glass breakage. When LGs are not available (i.e., existing components), anti-shatter safety films (ASF) for the retrofit of monolithic glass elements are expected to provide very similar post-breakage structural performances against bending and impact actions, by reducing the possible spread of glass shards. Besides, the residual load-bearing capacity of glass components retrofitted by ASF is still challenging to quantify. In this paper, the Cohesive Zone Model (CZM) theory is considered to investigate, with the support of experiments and Finite Element (FE) numerical models, the performance of small-scale monolithic glass specimens retrofitted by ASF under bending loads. Different ageing procedures and imposed displacement-rates are considered to evaluate the influence of basic operational parameters, such as temperature and humidity, on the mechanical efficiency of common ASF layers. In doing so, the sensitivity of fundamental input parameters (i.e., maximum tensile strength of glass and fracture energy of the ASF adhesive) on the mechanical performance at pre- and post-breakage stages of retrofitted monolithic glass elements is explored.

Reuse and remanufacturing of insulated glass units

AbstractMany office and residential buildings in Europe need to be renovated in the near future to meet current energy efficiency requirements. This often comes down to updating the insulation performance of the building envelope including the windows. Most “old” windows consist of a frame and a double insulated glass unit (IGU) or even monolithic glass panes – typically without any low-e coating. These non-coated double glazings have a Ug-value of 2.7 W/m2K (single glazing even 5.2 W/m2K). Modern coated triple glazed IGUs provide Ug-values of up to 0.5 W/m2K.This paper deals with the question of how old insulating glass units can be re manufactured to match the state of the art in terms of the energy efficiency. For this purpose, dismounted IGUs from the 1980s are used. After analyzing the remaining functionality, the double IGUs are disassembled. The single glass pane is cleaned, and the old edge sealing is removed. The old glass pane is combined with a new coated low-e glass and a spacer system to form a new upgraded IGU with warm edge technology. This study demonstrates that remanufactured IGUs can achieve the performance of IGUs made from new glass.

Lightweight silicon and glass composites with submicron viscoelastic interlayers and unconventional combinations of stiffness and damping

The necessity of stiff structural materials with advanced damping characteristics has arisen naturally along with the technological evolution. However, despite ever-growing demand, the achievement of stiff materials with high damping factor remains challenging because of the antagonistic nature of the two properties. Here, this challenge is accomplished by exploiting the non-affine deformation of laminated composites paired with the dissipative nature of the viscoelastic phase. Guided by a finite element design analysis, composites with flat submillimeter stiff layers and submicron viscoelastic interlayers are fabricated. The viscoelastic component consists of a prudently chemically architectured comb-like polydimethylsiloxane (PDMS) elastomer that properly adheres to the stiff silicon or glass layers, strong enough to withstand repeated dynamic cycles. The composites are fabricated using an unconventional but simple stacking route based on the diffusion of a platinum catalyst precursor into a reactive solvent-free PDMS melt. The fabricated composites, Si/PDMS and glass/PDMS, exhibit an elastic modulus higher than common monolithic glass, they are as light as glass but have about four orders of magnitude higher loss factor. The composites markedly outperform numerous customary materials, they escape the Ashby limit for mechanical damping – stiffness trade-off, and their exceptional combinations of properties are maintained over a broad range of temperatures and frequencies.

Design and Stability of Laminated Glass Beams and Cantilevers with Continuous Lateral Silicone Restraint

The stability of monolithic glass beams is reasonably well defined; as an elastic material it behaves in a similar manner to other elastic materials such as steel, for which there are many equations of different forms which give similar results. Special care is required for continuous restraint to the tension flange. Equations presented in Australian Standard AS1288 Glass in Buildings – Selection and Installation have been used successfully for many years for monolithic fins when used with the strength model of AS1288 but require a more comprehensive approach when using laminated fins and/or strength models that allow higher levels of stress. A review of equations for cantilevers results in a wider range of approaches with significant variance between the outcomes of various published steel and glass standards. AS1288 has been used as the default standard for stability of glass fins, however for cantilevers it appears to have a misprint which has existed for decades. This paper presents strategies for determining the moment capacity of beams and cantilevers made of laminated glass with continuous flexible buckling restraints, such as structural silicone, which have initial imperfections and a known design strength capacity. Where multiple wave lengths form, the warping stiffness may contribute and formulations for rectangles are presented. The accuracy and validity of the approach is also assessed by means of comparisons with the outcomes of Finite Element numerical analyses.

Mechanical Properties of Glass Plate During Anticlastic Cold Bending

Anticlastic glass surfaces play a significant role in free-form glass facades. For realizing anticlastic surface, cold bending by loading at the corner of the plate is more adaptive and more economic than traditional hot bending method. Previous research on anticlastic cold bending mainly focuses on the description of instability phenomenon and qualitative analysis of parameters. However, the failure mechanisms of glass plates during cold bending and the influence of lamination remains unclear. In this paper, the anticlastic cold bending test was conducted to explore the influence of various factors, including aspect ratio, scale and composition of the plates. Subsequently, an effective finite element model was established and validated by test results, which is used for further explore the cold bending controlling condition for better engineering practice. The failure modes are considered as instability and strength failure. For laminated glass, maximum stresses can be derived from monolithic glass based on equivalent thickness method. The instability is induced by the compression area in the middle surface of glass plate which is significantly influenced by the composition of the laminates. Consequently, thin glass laminates exhibit enhanced stability because a reduced glass to PVB thickness ratio changes the compression area from bi-directional to uni-directional.

Cosolvent-free sol–gel synthesis of macroporous silica gels from tetramethoxysilane–tetraethoxysilane mixtures

Abstract Tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and their mixtures were used for the cosolvent-free synthesis of macroporous silica gels as precursors for monolithic silica glasses. The liquid-state 29Si nuclear magnetic resonance (NMR) spectroscopy of precursor solutions indicated that cross-transesterification between TMOS and TEOS was completed in a few hours at 20 °C in the presence of an acid catalyst, whereas it was negligible when the catalyst was absent. In the precursor solutions prepared from TMOS, phase separation occurred after gelation, resulting in translucent gels. In contrast, in the solutions prepared from TEOS or a mixture of TMOS and TEOS at a TMOS mole fraction of 0.8, the phase separation can be induced before gelation, and opaque xerogels were easily obtained without fracture. The average size of macroscopic particles and macroporous structures were uniform over opaque xerogels prepared from TEOS. In contrast, in opaque xerogels prepared from the TMOS-rich mixture of TMOS and TEOS, the average particle size and macroscopic porosity inside them were notably smaller than those of the subsurface, probably because of a large exotherm upon gelation and the resulting temperature gradient in the gelling solutions. Such spatial morphology distribution made the sintering of the opaque gels into clear silica glasses difficult. Opaque gels prepared from TEOS and translucent gels prepared from solutions containing TMOS were transformed to clear silica glasses in high yields of ~99% by sintering in a helium atmosphere at 1050–1350 °C. Graphical abstract

Evaluation of Stress Distributions in All Ceramic Conometric Single Crown Restorations: 3-Dimensional Finite Element Analysis

Objective: The aim of the study is to compare the effect of monolithic translucent zirconia ceramic (TZI) and monolithic lithium disilicate glass ceramic (LDS) restorative materials on stress distributions in implant components and surrounding bone tissues in implant-supported conometric single crown restorations with a conical connection system by using 3D finite element analysis.
 Methods: Restorations produced with two different all-ceramic materials using a conometric abutment and a conometric cap on the implant with a conical connection system were placed in the maxillary right second premolar region. 3D finite element analysis was used to examine the amount and distribution of stresses in implant components, in cortical and cancellous bone tissues surrounding the implant and in crowns under vertical and oblique loading. For the statistical analysis one-way ANOVA and independent samples t-test were used (p

A 3D tailored monolithic glass chip for stimulating and recording zebrafish neuronal activity with a commercial light sheet microscope

Microfluidic technology is unrivaled in its ability to apply soluble chemical stimuli with high spatiotemporal precision. Analogous, light–sheet microscopy is unmatched in its ability of low phototoxic but fast volumetric in vivo imaging with single cell resolution. Due to their optical translucency during the larval stages, zebrafish (Danio rerio) are an ideal model to combine both techniques; yet, thus far this required light–sheet microscopes, which were in most cases custom–built and adapted to the available softlithographic chip technology. Our aim was to use a commercial light–sheet microscope to illuminate a microfluidic chip from two opposite lateral directions and to record images with the detection objective placed orthogonally above the chip. Deep tissue penetration can be achieved by superimposing beams from opposite directions to form a single light sheet. But a microfluidic chip that allows a) targeted stimulus application in a closed microenvironment, b) interference–free incoupling of excitation light from two directions and c) outcoupling of fluorescence in the perpendicular direction through an optically perfect cover glass was not known until now. Here, we present a monolithic glass chip with the required plane-parallel sidewalls and cover slide closure at the top, constructed by advanced femtosecond laser ablation, thermal bonding and surface smoothing processes. In addition, the 3D shape of a fish fixator unit was tailored to match the body shape of a zebrafish larva to ensure stable positioning during whole–brain recording. With hydrodynamic focusing a targeted partial exposure of the larva’s head to chemical stimuli and fast position switching (in less than 10 s) was possible. With the capabilities of this unique monolithic glass chip and its up–scalable wafer–level fabrication process, the new NeuroExaminer is prone to become an excellent addition to neurobiology laboratories already equipped with high–quality commercial light sheet microscopes.

Post-Fracture Stiffness and Residual Capacity Assessment of Film-Retrofitted Monolithic Glass Elements by Frequency Change

The primary goal of safety films for glass in buildings is to retrofit existing monolithic elements and prevent, in the post-fracture stage, any fall-out of shards. Their added value is that—as far as the fragments are kept bonded—a cracked film-glass element can ensure a minimum residual mechanical and load-bearing capacity, which is strictly related to the shards interlocking and debond. To prevent critical issues, such a mechanical characterization is both important and uncertain, and requires specific methodologies. In this regard, a dynamic investigation is carried out on fractured film-bonded glass samples, to assess their post-fracture stiffness trends and its sensitivity to repeated vibrations. The adopted laboratory layout is chosen to assess the effects of random vibrations (220 repetitions) on a total of 12 cracked specimens in a cantilever setup (with 0.5–5 m/s2 the range of randomly imposed acceleration peaks). By monitoring the cracked vibration frequency, the film efficiency and corresponding residual bending stiffness of cracked glass samples are quantified as a function of damage severity, with a focus on fragments interlock. Quantitative experimental estimates are comparatively analyzed and validated with the support of finite element (FE) numerical models and analytical calculations. As shown—at least at the small-scale level—a progressive post-fracture stiffness reduction takes place under repeated random vibrations, and this implicitly affects the residual load-bearing capacity of glass members. Most importantly, for the tested configurations, it is shown that the cracked vibration frequency is minimally affected by crack geometry, and follows a rather linear decrease with the number of imposed random impacts (up to an average of ≈20 for each sample), thus confirming the retrofit potential and efficiency in providing some mechanical capacity through fragments interlock.

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.

On the Blocking and Shearing Interaction of Shear Bands in Pd, Zr, and Cu-Based Monolithic Metallic Glasses

On the Blocking and Shearing Interaction of Shear Bands in Pd, Zr, and Cu-Based Monolithic Metallic Glasses

Vacuum insulated glazing (VIG) units under wind load—part 1: global deformation and stresses on the outer glass surfaces

This paper presents the first part of a study on the effect of wind loads on Vacuum Insulated Glass (VIG) units. The study provides background information on VIG and relevant Standards, explains the numerical modelling process, and discusses the implications of the results in relation to European and North American codes and Standards. The focus of the study is on vertical windows and façade installations in low-rise buildings (< 25 m) commonly found in residential buildings. The mechanical behaviour of VIG was analysed using the Finite Element Method (FEM) with respect to various design parameters such as glass pane size, glass thickness, surface pressure magnitude, and edge boundary conditions. The study analysed global deformation as well as the stresses on the outer glass surfaces. The VIG features such as pillar geometry and contact dynamics, and material non-linear effects, were explicitly modelled. In addition, monolithic glass plates were also modelled, and the FEM results of the monolithic cases were in reasonable agreement with an analytical solution obtained from linear thin plate theory. These results highlight the limit of linear behaviour in monolithic plate bending. The centre-of-pane deflection of the VIG was in good agreement with the FEM and analytical solutions of the equivalent thickness monolithic pane, for sample sizes below 800 × 800 mm. However, for larger glass sizes, a deviation was found, and the VIG exhibited a higher plate stiffness than the equivalent thickness monolithic pane. The simulations also showed that the stresses in the glass panes are highly dependent on the edge of glass boundary condition. Finally, the results demonstrated that with appropriate design choices, the VIG can satisfy the Standards requirements for wind load and glass design in both Europe and North America.

Multi-performance blast pressure-duration curves for point-supported laminated and monolithic glass panes

Although point-supported glazing systems have been widely used in modern architecture, their blast performance is not fully documented yet. Most of the available code specifications and design guidelines are developed exclusively for frame-supported glass panes, i.e. panes with continuous edge supports, and it is expected that their point-supported counterparts are more vulnerable to blast loads. This study is devoted to evaluate blast performance of point-supported Laminated Glass (LG) and Thermally Tempered Glass (TTG) panes by using validated 3D Finite Element (FE) models. Considering different limit states (ranging from initial cracking to ultimate failure), multi-performance Pressure-Duration (P-D) curves, maximum pane deformations and maximum support reactions are developed for point-supported LG and TTG panes with varying dimensions, layups and thicknesses. Obtained results indicate that, compared with Polyvinyl Butyral (PVB) layer thickness, glass layer thickness has greater contribution to the blast resistance of LG panes. Moreover, in the case of small dimension point-supported panes, TTG panes unexpectedly outperformed LG panes, especially during blasts with higher positive durations. Finally, P-D curves of point-supported panes are compared with those of frame-supported panes. With a few exceptions, point-supported panes generally have significantly less blast resistance than their frame-supported counterparts. The difference is more pronounced in the case of larger dimension glass panes. This indicates that P-D curves of current codes and guidelines, which were developed based on frame-supported glass panes, cannot be directly applied to point-supported glass panes.

Influence of Li3BO3 on the stability of Li1.5Al0.5Ge1.5(PO4)3 glass-ceramics with Li4Ti5O12 anode

All-solid-state Li+ batteries have a number of advantages over traditional batteries with a liquid electrolyte. One of the key problems related to their creation is the choice of compatible materials. In this work, the chemical and thermal stability of Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte versus Li4Ti5O12 anode was studied. Nanostructured Li4Ti5O12 powder with the mean particle size of about 500 nm was synthesized by sol-gel method. NASICON-type structured Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte obtained by the crystallization of the monolithic glass exhibits a high lithium-ion conductivity (5·10−4 S cm−1 at 25 °C) and a compact microstructure. The thermal behavior of their mechanical mixture and the resistance of the solid electrolyte|electrode half-cells were investigated. The influence of Li3BO3 addition on the interface between the solid electrolyte and composite anode is also discussed. According to DSC data, the interaction of Li1.5Al0.5Ge1.5(PO4)3 with Li4Ti5O12 begins at 545 °C, while Li3BO3 leads to a slight increase in their thermal stability up to 632 °C. It was established that Li2TiO3 and TiO2 impurities are formed after annealing the Li1.5Al0.5Ge1.5(PO4)3:Li4Ti5O12 mixture at 600 and 700 °C. However, Li3PO4 and AlPO4 phases begin to appear after annealing the studied mixture at 800 °C. In case of the Li3BO3-containing mixture, Li4B2O5, Li3PO4, LiTi2O4 and AlPO4 phases are formed only after annealing at 700 °C, while heating at 800 °C leads to the complete degradation of the Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte. The resistance of the cells with Li4Ti5O12 anode decreases when the annealing temperature rises from 500 to 800 °C. The introduction of Li3BO3 into the composite anode leads to an increase in the interface resistance under the same heat treatment conditions.

Review of the Main Mechanical Testing Methods for Interlayer Characterization in Laminated Glass

In the last decades, the use of structural glass has increased exponentially. The reliability of brittle structural glass elements is considerably improved if laminated glass elements are chosen because, in this case, a redistribution of internal forces is permitted once a limited breakage occurs. Thus, instead of monolithic glass, composite materials consisting of two or more glass plies bonded together using a polymeric film as an interlayer are used. In the event of glass failure, because of the chemical bond between the different materials, the adhesion to the interlayer prevents glass fragments from scattering. To design structural elements, the definition of the mechanical features of the interlayer is necessary. However, several standards and techniques can be applied, considering the characterization of either the interlayer itself or the laminated glass. The paper reviews the main existing methods and focuses on the standard suggested by the CEN/TS 19100:2021, analyzing in detail the effect of the different parameters involved. A numerical model is presented to account for the effect of the stress level, glass, and interlayer thickness. Although the standard leaves a certain degree of freedom in choosing those parameters, in some cases the results can differ.

Morphological characterization and reconstruction of fractured heat-treated glass

Fracture morphology has insightful information related to the residual effect of fractured structural glass, which is vital in assessing the post-fracture performance of glass members. This study experimentally characterized the fracture morphology of heat-treated glass and developed a novel method of morphology reconstruction, which aims to facilitate the numerical analysis of fractured structural glass. With the development of a computer-vision-based method for transparent objects, the morphology information from fragmentation tests was extracted and systematically investigated for monolithic heat-treated glass with various thicknesses, surface compressive stresses and fracture initiation locations, which are considered as the key influencing factors of heat-treated glass fracture. The geometrical features of fragments and their spatial distribution were quantitatively analysed, identifying their correlations with glass properties. The result indicates that the distribution of fragment centroids shows greater dispersion as the tempering level increases, and the fragments tend to be smaller and more rounded. The strain energy release at fracture was also assessed by fracture patterns, showing it presents high sensitivity to the glass thickness and surface compressive stress. Subsequently, a novel approach was proposed for the stochastic reconstruction of fracture morphology, combining feature points distribution and Voronoi tessellation concept. The control parameters are determined by data from the fragmentation tests and the influence of fracture load could be properly considered. The proposed method shows satisfactory outcomes and good agreement with the experimental records, which has further potential in developing refined numerical models by considering more realistic fracture morphology of glass members.

Effects of post-fracture repeated impacts and short-term temperature gradients on monolithic glass elements bonded by safety films

Weathering and operational conditions, as known, have significant impact on typical constituent materials which are used for many construction applications. Among others, structural glass solutions can suffer for these effects in terms of major modification of material properties of interlayers, bonds, connections, gaskets and polymeric components in general. In this paper, the attention is given to the effects of repeated low-amplitude impacts and short-term temperature gradients for the characterization of load-bearing capacity in monolithic glass elements retrofitted by safety films. Especially for existing glass systems which are made of monolithic glass with limited strength and resistance capacity against ordinary and accidental mechanical loads, safety films are commercially available for retrofit interventions. They are primarily expected to keep together glass fragments in case of breakage, and thus minimize possible injuries. Besides, after first fracture, the so obtained glass-film composite elements have uncertain residual mechanical capacity against ordinary loads, given that it mostly depends on thin films composed of Polyethylene terephthalate (PET)-layers and pressure sensitive adhesives (PSAs). To this aim, a set of experiments (for a total of 950 configurations) is carried out in laboratory conditions (30 °C) on small-scale samples of fractured annealed monolithic glass elements bonded by commercial safety films, under repeated low-amplitude impacts / vibrations (S1-TR series), or additionally subjected to preliminary short-term thermal gradients (S2-TC1 series cooled at +5 °C and S3-TC2 series at −20 °C). Localized impacts are quantified in acceleration peaks in the range of 2 ÷ 14 m/s2 and rotations at supports in the order of 15 ÷ 20°. The interpretation of dynamic experimental results is carried out in terms of post-fracture vibration frequency (based on classical operational modal analysis techniques) and used, with the support of simplified analytical models or Finite Element (FE) numerical simulations, to characterize the response of cracked glass-film samples. Most importantly, the vibration frequency decrease is used to quantify their residual load-bearing capacity under unfavourable conditions, and to quantify the post-critical benefit of thin bonding safety films under unfavourable conditions.

Application and Fundamental Researches on Metallic Glasses; Development of Engineering Products and Challenge to Improve Brittleness

Metallic glasses exhibit a high mechanical strength at room temperature and superior formability in a supercooled liquid region, which make them to become promising materials for engineering applications. However, two major drawbacks, one is difficulty in fabricating bulk samples and the other is their intrinsic brittle properties during fracture, highly limited their practical applications. With respect to the former, we focused on fabricating micrometer size products and a Fe-based metallic glassy micro gear was successfully developed through our newly proposed microparts fabrication process. For the latter, a concept of amorphous/glassy state gradient is introduced, intending to improve a brittleness by controlling the crack propagation path depending on a created gradient state. The temperature/thermal history gradient is thermally introduced within a single monolithic Zr-based metallic glass, and it was found that a brittleness presumably improved by thermally created amorphous/glassy state gradient.

The Effects of the Large-Scale Factor on the Integrity Parameters of Monolithic Fire-Resistant Glass

Glass is widely used for the manufacture of the facades and interior glazing of buildings. Glass structures are subject to high fire safety requirements. Two methods are employed in this work: experimental studies of small-sized and large-sized samples and simulations of heating glass structures. The results showed that large-sized samples of monolithic tempered glass, with dimensions of 4250 × 2000 × 8 mm and 2000 × 3000 × 8, that were inserted in a steel frame, if properly installed, provided fire resistance limits of E30/E45 and E60, respectively, for loss of integrity, which proves the influence of the dimensions of the glass panel on the fire resistance of the facade structure. The small-sized samples of monolithic tempered glass with dimensions of 1000 × 700 × 8 mm provided a fire resistance limit of E60 for loss of integrity. A large-sized sample of monolithic tempered glass measuring 4250 × 2000 × 8 mm and inserted into an aluminum frame provided a fire resistance limit of E60, proving the effect of the frame on the fire resistance of the structure. According to the results of several simulations, a conclusion was formed about the possibility of predicting the fire resistance limits of tempered glass based on its thickness and dimensions. During operations, these structures will be able to prevent the spread of fire and combustion products for the required time after the loss of integrity. The results of the study allow for the estimation of the influence of the scale factor on the falling of the glass from the frame in a fire (loss of integrity).