Experimental and Numerical Peeling Investigation on Aged Multi-Layer Anti-Shatter Safety Films (ASFs) for Structural Glass Retrofit

Anti-shatter safety films (ASFs) are often used for structural glass applications. The goal is to improve the response of monolithic elements and prevent fragments from shattering. Thus, the main reason behind their use is the possibility to upgrade safety levels against the brittle failure of glass and minimize the number of possible injuries. However, the impact response of glass elements bonded with Polyethylene terephthalate (PET)-films and pressure sensitive adhesives (PSAs) still represents a research topic of open discussion. Major challenges derive from material characterization and asymmetrical variability under design loads and ageing. In particular, the measurement of interface mechanical characteristics for the adhesive layer in contact with glass is a primary parameter for the ASF choice optimization. For this reason, the present paper presents an experimental campaign aimed at calibrating some basic mechanical parameters that provide the characterization of constitutive models, such as tensile properties (yielding stress and Young modulus) for PET-film and adhesive properties for PSA (energy fracture and peel force). In doing so, both tensile tests for PET-films and peeling specimens are taken into account for a commercially available ASF, given that the peeling test protocol is one of most common methods for the definition of adhesion properties. Moreover, an extensive calibration of the Finite Element (FE) model is performed in order to conduct a parametric numerical analysis of ASF bonded glass solutions. Furthermore, a Kinloch approach typically used to determine the fracture energy of a given tape by considering a variable peel angle, is also adopted to compare the outcomes of calibration analyses and FE investigations on the tested specimens. Finally, a study of the effect of multiple aspects is also presented. The results of the experimental program and the following considerations confirm the rate dependence and ageing dependence in peel tests.

Dot blot immunochemical and infrared analyses of the adhesive layer applied to the painting Imago Pietatis by Domenico Morone

Purpose To investigate the nature of the materials used in the adhesive layer of the Imago Pietatis painting (end of the fifteenth century—beginning of the sixteenth century) by Domenico Morone as a prerequisite for its restoration. Methods Micro-FTIR spectra of the animal glue and a polished cross-section were acquired by a Jasco IRT3000 spectrometer, equipped with a 32× Cassegrain objective. A dot blot immunoassay was used to characterise a minor component of the adhesive layer. Results Micro-FTIR was used as an effective diagnostic tool to detect the major component of the adhesive layer and the binder of the paint. Despite the ageing, the complex matrix and the micro-size of the sample, using a dot blot immunoassay, it was possible to quantify 3.7 ± 2.0 ng of ovalbumin per microgram of sample (corresponding to 0.004 ± 0.002% of the weight). Conclusions The findings were in line with conservation practices described in the old treatises, confirming the correct interpretation of the adhesive layer compounds added to the painting and suggesting for the cleaning the use of an anionic water-soluble surfactant highly effective in the removing of proteinaceous materials.

Piezoelectric Unimorph and Bimorph Cantilever Configurations: Design Guidelines and Strain Assessment

Multi-stable configurations of piezoelectric harvesters are quite successful in achieving the two important goals, the broadband frequency response and large orbit oscillations exhibiting periodic, multi-periodic, and chaotic solutions. However, in the quest of achieving large amplitude broadband frequency response, assessment of induced strain levels considering the limits on the strain in piezoelectric material has received minimal attention. In this context, the investigation presents an analytical formulation for the assessment of induced strain and voltage(s) in piezoelectric unimorph and bimorph cantilevers. The formulation quantifies not only the induced voltage(s) in individual piezoelectric layers of a bimorph, but also the equivalent voltages in parallel and series connection modes, respectively. Also, while computing the induced voltage in the first piezoelectric layer, the contribution from the induced voltage of the second piezoelectric layer to the acting bending moment is captured in the formulation. The formulations are validated through the experiments and results from the literature. Further, we have applied two practically useful normalization schemes, the tp- and tt-normalizations to the analytical expressions. Using the two normalization schemes, influences of variation of substrate and adhesive layer thicknesses, elastic moduli of layers, and substrate-to-composite length fraction are visualized and discussed. Based on the results, summarized guidelines for design and selection of geometric and material parameters are presented, which are also applicable for other sensing and actuation applications. At last, practically suitable ranges and optimum values for the normalized design variables are proposed.

FEM Analysis as a Tool to Study the Behavior of Methacrylate Adhesive in a Full-Scale Steel-Steel Shear Joint

The use of adhesive to joint structural elements, despite many advantages of this technology, is not a method commonly used in engineering practice, especially in construction. This is mainly due to the poor recognition of the behavior, both in terms of testing and analysis, of joints made on a scale similar to the actual elements of building structures. Therefore, this paper presents the results of model tests and then numerical analyses of adhesively bonded joints made of high-strength steel elements in a full-scale (double-lap joint). In order to properly model the adhesive connection, material tests of the methacrylate adhesive were performed in the field of tensile, shear (in two versions: single lap joint test and thick adherent shear test) and bond properties. Comparison of the results of the model and numerical tests showed very good agreement in terms of the measurable values, which makes it possible to consider the results obtained in the adhesive layer as reliable (not directly measurable in model tests). In particular, the distribution of stresses inside the adhesive layer, the range of plastic zones and areas of loss of adhesion are presented and discussed. The results indicate the possibility of a reliable representation of the behavior of adhesively bonded joints of high-strength steel, thus providing a tool for the analysis of semirigid adhesive in large-size joints.

Preparation of Ideally Ordered Anodic Porous Alumina by Prepatterning Process Using a Flexible Mold

Ideally ordered anodic porous alumina with controlled interpore distances was formed by fabricating a resist mask using a flexible mold and subsequent anodization. Prior to forming the resist pattern on the surface of an Al substrate, Al was pre-anodized at 10 V to prepare the fine porous structure, which acts as a resist adhesive layer. After the formation of the resist mask using a flexible mold, an arranged array of cavities with Al exposed at the bottom was formed by the selective dissolution of the oxide layer at resist openings. The subsequent anodization of the sample with the cavity array generated ideally ordered anodic porous alumina because alumina holes were formed at the bottom of cavities during anodization. This process allows the preparation of ideally ordered anodic porous alumina even on a curved Al surface owing to the flexibility of the mold. In addition, this process can also be applied to the preparation of an ideally ordered anodic porous alumina with a large sample area because the Al substrate can be patterned without high pressure. The obtained sample can be used for various applications requiring an ideally ordered hole array structure.

Preparation and Characterization of Acrylic Pressure-Sensitive Adhesives Crosslinked with UV Radiation-Influence of Monomer Composition on Adhesive Properties

In this study, syntheses of acrylate copolymers were performed based on the monomers butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), and acrylic acid (AA) and the second-type unsaturated photoinitiator 4-acryloyloxybenzophenone (ABP). The structure of the obtained copolymers was confirmed via FT-IR spectroscopic analysis, and the viscosity and the content of non-volatile substances were determined. The adhesive films were then coated and cross-linked using ultraviolet radiation in the UV-C range at various doses (5–50 mJ/cm2). Due to the dependence of the self-adhesive properties of the adhesive layer on the basis weight, various basis weights of the layer in the range of 30–120 g/m2 were tested. Finally, the self-adhesive properties were assessed: tack, peel adhesion, shear strength (cohesion) at 20 °C and 70 °C, as well as the SAFT test and shrinkage. The aim of the study was to determine the effect of the type of monomer used, the dose of ultraviolet radiation, and the basis weight on the self-adhesive and usable properties of the obtained self-adhesive tapes.

Effect of nylon fabric reinforcement on the mechanical performance of adhesive joints made between glass and GFRP

The use of reinforcements in adhesive joints makes the stress distribution more uniform, improving their mechanical performance and adhesion. The present paper aims to verify the effectiveness and efficiency of the insertion of nylon 6 fabric in the adhesive layer, to study their applicability and functionality in building components. The increase in stiffness achieved by applying nylon 6 fabric in the adhesive layer between glass and GFRP pultruded profiles and steel laminates applied to GFRP beams is investigated. Three different epoxy adhesives and one epoxy resin are used and compared. Three different types of tests are carried out in order to study the different properties of the reinforcement system: tensile tests on GFRP/GFRP single-lap adhesive joints, with and without nylon fabric reinforcement; tensile tests on double-lap adhesive joints between float glass and pultruded GFRP profiles reinforced with nylon fabric according to four configurations (in the middle plane of the adhesive layer, on the glass surfaces, on the GFRP surfaces, on both GFRP and glass configurations) to verify the influence of its position; three-point bending tests on long GFRP tubular profiles reinforced with steel plates and nylon fabric in different configurations, to study resistance to bending loads. The results from the experimental campaign show the effectiveness of the reinforcement system using nylon fabric 6. In general, both a reduction in ultimate strength and an increase in joint stiffness compared to unreinforced configurations are observed.

Demonstration of using HF-etchant mixed into CO2 to lift-off thin-film GaAs layers by supercritical fluid technology

The epitaxial lift-off (ELO) process based on selectively etching a thin sacrificial AlAs layer from GaAs substrate was performed using high-concentrated aqueous hydrofluoric (HF) etchant. However, because of using the wet etching method, the traditional ELO process has many drawbacks and limitations. Supercritical fluids (SCFs) naturally have the characteristics of low viscosity, high diffusivity, and zero surface tension. Therefore, the development of a gas-phase-like dry etching method based on mixing HF into CO2 and operating the mixture of HF/CO2 in SCFs condition as etchant is hereby proposed to overcome those bottlenecks existing in traditional wet ELO processes. However, there are no available experimental results for etching AlAs layers by HF in SCFs yet. Therefore, a HF-compatible corrosion-resistant high-pressure system was designed and built up to perform the idea. The capabilities of etching sample in supercritical CO2 (scCO2) had been systemically investigated under various pressures (2000–3000 psi) and temperatures (40–60[Formula: see text]C). Besides, the etching performances separately conducted by using aqueous-HF and anhydrous HF/Pyridine as the source etchant and mixing with scCO2 at a fixed temperature, pressure and etching time were also examined and compared under different equivalent HF concentrations. An evaluation of using acetone as the co-solvent mixed with HF/scCO2 mixture for enhancing the etch rate in different volume ratio of HF/co-solvent was further investigated and discussed. With this system, we demonstrate releasing a size of [Formula: see text] (width × length) and 3 [Formula: see text]m-thick free-standing GaAs sheet from a 150 nm AlAs sacrificial layer by the etching sample in HF/scCO2 mixture. The released GaAs sheet was also successfully transferred to a flexible PET substrate by using a PDMS stamp and an adhesive layer of NOA61.