Please cite this article as: Memon S, Farukh F, Eames PC, Silberschmidt VV, A new low-temperature hermetic composite edge seal for the fabrication of triple vacuum glazing, Vaccum (2015Vaccum ( ), doi: 10.1016Vaccum ( / j.vacuum.2015 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 AbstractHigh performance low-cost vacuum glazing is a key development in the move to more energy-efficient buildings. This study reports the results of experimental and theoretical investigations into the development of a new low-temperature (less than 200˚C) composite edge seal. A prototype triple vacuum glazing of dimensions 300mmx300mm was fabricated with a measured vacuum pressure of 4.8x10 -2 Pa achieved. A three-dimensional finite-element model for this prototype triple vacuum glazing with the composite edge seal was also developed. Centre-of-pane and total thermal transmittance values for this small prototype of the triple vacuum glazing were predicted to be 0.33 Wm -2 K -1 and 1.05 Wm -2 K -1 , respectively. It was predicted using the developed model that the thermal performance could be improved by reducing the width of the composite edge seal and by the use of soft low-emissivity coatings on the glass surfaces. Detailed three-dimensional isothermal contour plots of the modelled triple vacuum glazing are presented.

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Abstract:Thermal bonding is the fastest and cheapest technique for manufacturing nonwovens. Understanding mechanical behaviour of these materials, especially related to damage, can aid in design of products containing nonwoven parts. A finite-element model incorporating mechanical properties related to damage such as maximum stress and strain at failure of fabric's fibres would be a powerful design and optimization tool. In this study, polypropylene-based thermally bonded nonwovens manufactured at optimal processing conditions were used as a model system. A damage behaviour of the nonwoven fabric is governed by its single-fibre properties, which are obtained by conducting tensile tests over a wide range of strain rates. The fibres for the tests were extracted from the nonwoven fabric in a way that a single bond point was attached at both ends of each fibre. Additionally, similar tests were performed on unprocessed fibres, which form the nonwoven. Those experiments not only provided insight into damage mechanisms of fibres in thermally bonded nonwovens but also demonstrated a significant drop in magnitudes of failure stress and respective strain in fibres due to the bonding process. A novel technique was introduced in this study to develop damage criteria based on the deformation and fracture behaviour of a single fibre in a thermally bonded nonwoven fabric. The damage behaviour of a fibrous network within the thermally bonded fabric was simulated with a finite-element model consisting of a number of fibres attached to two neighbouring bond points. Additionally, various arrangements of fibres' orientation and material properties were implemented in the model to analyse the respective effects.

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Due to random orientation of fibres and presence of voids in their microstructure, lowdensity thermally bonded polymer-based nonwovens demonstrate complex processes of deformation and damage initiation and evolution. This paper aims to introduce a micro-scale discontinuous finite element model to simulate an onset of damage in low-density nonwovens. In the model, structural randomness of a nonwoven fabric was introduced in terms of orientation distribution function (ODF) obtained by an algorithm based on the Hough Transform. Fibres were represented in the model with truss elements with orientations defined according to the computed ODF. Another structural element of nonwovens -bond points-were modelled with shell elements having isotropic mechanical properties. The numerical scheme employed direct modelling of fibres at micro level, naturally introducing the presence of voids into the model and thus making it suitable for simulations of low-density nonwovens. The obtained results of FE simulations were compared with our data of tensile tests performed in principal directions until the onset of damage in the specimens.