Thermal performance of composite panels under fire conditions using numerical studies : plasterboards, rockwool, glass fibre and cellulose insulations

In recent times, light gauge steel frame (LSF) wall systems are increasingly used in the building industry. They are usually made of cold-formed and thin-walled steel studs that are fire-protected by two layers of plasterboard on both sides. A composite LSF wall panel system was developed recently, where an insulation layer was used externally between the two plasterboards to improve the fire performance of LSF wall panels. In this research, finite element thermal models of the new composite panels were developed using a finite element program, SAFIR, to simulate their thermal performance under both standard and Eurocode design fire curves. Suitable apparent thermal properties of both the gypsum plasterboard and insulation materials were proposed and used in the numerical models. The developed models were then validated by comparing their results with available standard fire test results of composite panels. This paper presents the details of the finite element models of composite panels, the thermal analysis results in the form of time-temperature profiles under standard and Eurocode design fire curves and their comparisons with fire test results. Effects of using rockwool, glass fibre and cellulose fibre insulations with varying thickness and density were also investigated, and the results are presented in this paper. The results show that the use of composite panels in LSF wall systems will improve their fire rating, and that Eurocode design fires are likely to cause severe damage to LSF walls than standard fires.

Future of the Haze Agreement : is the glass half empty or half full?

"In 1997–98, the ASEAN (Association of Southeast Asian Nations) region suffered an unprecedented health and environmental catastrophe due to choking haze created by a massive forest !re in Indonesia. It is estimated that the total losses from the fire could be US$5–6 billion after taking into account the loss of trees and other natural resources as well as the long-term impact on human health. This unprecedented anthropogenic disaster not only created a severe health and environmental hazard but also raised a question mark about the credibility and effectiveness of the ASEAN regional grouping. Against this background, ASEAN took a number of regional initiatives to try and solve the problem and finally adopted a new treaty for regional cooperation to combat forest fire and haze in 2002. This paper assesses the future success of this agreement from the perspectives of the legal, institutional and geopolitical reality of the region. Since numerous studies have examined state responsibility for transboundary environmental harm under international law and its implications on the ASEAN haze problem, this article will not touch upon that general debate nor the remedies that are possibly available to victim states. Rather, it will focus on the ASEAN regional legal and institutional initiatives to combat the haze pollution and compare them with a similar European regional agreement. Regarding the following analysis, it is important to recognise the uncertainty arising from Indonesia’s status (presently a non-party to the Agreement). A primary indication of the future effectiveness of this agreement can be drawn from an analysis of the principles involved in this agreement, bearing in mind the inherent difficulty of enforcing norms in the international environmental legal system as a whole, and the geopolitical reality of the region."

Delivery of dimethyloxallyl glycine in mesoporous bioactive glass scaffolds to improve angiogenesis and osteogenesis of human bone marrow stromal cells

Development of hypoxia-mimicking bone tissue engineering scaffolds is of great importance in stimulating angiogenesis for bone regeneration. Dimethyloxallyl glycine (DMOG) is a cell-permeable, competitive inhibitor of hypoxia-inducible factor prolyl hydroxylase (HIF-PH), which can stabilize hypoxia-inducible factor 1α (HIF-1α) expression. The aim of this study was to develop hypoxia-mimicking scaffolds by delivering DMOG in mesoporous bioactive glass (MBG) scaffolds and to investigate whether the delivery of DMOG could induce a hypoxic microenvironment for human bone marrow stromal cells (hBMSC). MBG scaffolds with varied mesoporous structures (e.g. surface area and mesopore volume) were prepared by controlling the contents of mesopore-template agent. The composition, large-pore microstructure and mesoporous properties of MBG scaffolds were characterized. The effect of mesoporous properties on the loading and release of DMOG in MBG scaffolds was investigated. The effects of DMOG delivery on the cell morphology, cell viability, HIF-1α stabilization, vascular endothelial growth factor (VEGF) secretion and bone-related gene expression (alkaline phosphatase, ALP; osteocalcin, OCN; and osteopontin, OPN) of hBMSC in MBG scaffolds were systematically investigated. The results showed that the loading and release of DMOG in MBG scaffolds can be efficiently controlled by regulating their mesoporous properties via the addition of different contents of mesopore-template agent. DMOG delivery in MBG scaffolds had no cytotoxic effect on the viability of hBMSC. DMOG delivery significantly induced HIF-1α stabilization, VEGF secretion and bone-related gene expression of hBMSC in MBG scaffolds in which DMOG counteracted the effect of HIF-PH and stabilized HIF-1α expression under normoxic condition. Furthermore, it was found that MBG scaffolds with slow DMOG release significantly enhanced the expression of bone-related genes more than those with instant DMOG release. The results suggest that the controllable delivery of DMOG in MBG scaffolds can mimic a hypoxic microenvironment, which not only improves the angiogenic capacity of hBMSC, but also enhances their osteogenic differentiation.

Fabrication and in vitro characterisation of bioactive glass composite scaffolds for bone regeneration

Here we fabricate and characterise bioactive composite scaffolds for bone tissue engineering applications. 45S5 Bioglass® (45S5) or strontium-substituted bioactive glass (SrBG) were incorporated into polycaprolactone (PCL) and fabricated into 3D bioactive composite scaffolds utilising additive manufacturing technology. We show that composite scaffolds (PCL/45S5 and PCL/SrBG) can be reproducibly manufactured with a scaffold morphology highly resembling that of PCL scaffolds. Additionally, micro-CT analysis reveals BG particles were homogeneously distributed throughout the scaffolds. Mechanical data suggested that PCL/45S5 and PCL/SrBG composite scaffolds have higher compressive Young’s modulus compared to PCL scaffolds at similar porosity (~75%). After 1 day in accelerated degradation conditions using 5M NaOH, PCL/SrBG, PCL/45S5 and PCL lost 48.6 ±3.8%, 12.1 ±1% and 1.6 ±1% of its original mass, respectively. In vitro studies were conducted using MC3T3 cells under normal and osteogenic conditions. All scaffolds were shown to be non-cytotoxic, and supported cell attachment and proliferation. Our results also indicate that the inclusion of bioactive glass (BG) promotes precipitation of calcium phosphate on the scaffold surfaces which leads to earlier cell differentiation and matrix mineralisation when compared to PCL scaffolds. However, as indicated by ALP activity, no significant difference in osteoblast differentiation was found between PCL/45S5 and PCL/SrBG scaffolds. These results suggest that PCL/45S5 and PCL/SrBG composite scaffold shows potential as a next generation bone scaffold.

Melt-electrospun polycaprolactone-strontium substituted bioactive glass scaffolds for bone regeneration

Polycaprolactone (PCL) is a resorbable polymer used extensively in bone tissue engineering owing to good structural properties and processability. Strontium substituted bioactive glass (SrBG) has the ability to promote osteogenesis and may be incorporated into scaffolds intended for bone repair. Here we describe for the first time, the development of a PCL-SrBG composite scaffold incorporating 10% (weight) of SrBG particles into PCL bulk, produced by the technique of melt-electrospinning. We show that we are able to reproducibly manufacture composite scaffolds with an interconnected porous structure and, furthermore, these scaffolds were demonstrated to be non-cytotoxic in vitro. Ions present in the SrBG component were shown to dissolve into cell culture media and promoted precipitation of a calcium phosphate layer on the scaffold surface which in turn led to noticeably enhanced alkaline phosphatase activity in MC3T3-E1 cells compared to PLC-only scaffolds. These results suggest that melt-electrospun PCL-SrBG composite scaffolds show potential to become effective bone graft substitutes.

Computational analysis of laminated glass panels under blast loads: A comparison of two dimensional and three dimensional modelling approaches

This paper illustrates the use of finite element (FE) technique to investigate the behaviour of laminated glass (LG) panels under blast loads. Two and three dimensional (2D and 3D) modelling approaches available in LS-DYNA FE code to model LG panels are presented. Results from the FE analysis for mid-span deflection and principal stresses compared well with those from large deflection plate theory. The FE models are further validated using the results from a free field blast test on a LG panel. It is evident that both 2D and 3D LG models predict the experimental results with reasonable accuracy. The 3D LG models give slightly more accurate results but require considerably more computational time compared to the 2D LG models.

Failure analysis of laminated glass panels subjected to blast loads

This paper presents a rigorous and a reliable analytical procedure using finite element (FE) techniques to study the blast response of laminated glass (LG) panel and predict the failure of its components. The 1st principal stress (σ11) is used as the failure criterion for glass and the von mises stress (σv) is used for the interlayer and sealant joints. The results from the FE analysis for mid-span deflection, energy absorption and the stresses at critical locations of glass, interlayer and structural sealant are presented in the paper. These results compared well with those obtained from a free field blast test reported in the literature. The tensile strength (T) of the glass has a significant influence on the behaviour of the LG panel and should be treated carefully in the analysis. The glass panes absorb about 80% of the blast energy for the treated blast load and this should be minimised in the design.

Strong and bioactive tri-calcium phosphate scaffolds with tube-like macropores

Calcium phosphate ceramic scaffolds have been widely investigated for bone tissue engineering due to their excellent biocompatibility and biodegradation. Unfortunately, they have the shortcoming of low mechanical properties. In order to provide strong, bioactive, and biodegradable scaffolds, a new approach of infiltrating the macro-tube ABS (acrylontrile butadiene styrene) templates with a hydroxyapatite/bioactive glass mixed slurry was developed to fabricate porous Si-doped TCP (tri-calcium phosphate) scaffolds. The porous Si-doped TCP ceramics with a high porosity (~65%) and with interconnected macrotubes (~0.8mm in diameter) and micropores (5-100 m) had a high compressive strength (up to 14.68+0.2MPa), which was comparable to that of a trabecular bone and was much higher than those of pure TCP scaffolds. Additional cell attachment study and MTT cytotoxicity assay proved the bioactivity and biocompatibility of the new scaffolds. Thus a potential bioceramic material and a new approach to make the potential scaffolds were developed for bone tissue engineering.

Stimulation of osteogenic and angiogenic ability of cells on polymers by pulsed laser deposition of uniform akermanite-glass nanolayer

Polymer biomaterials have been widely used for bone replacement/regeneration because of their unique mechanical properties and workability. Their inherent low bioactivity makes them lack osseointegration with host bone tissue. For this reason, bioactive inorganic particles have been always incorporated into the matrix of polymers to improve their bioactivity. However, mixing inorganic particles with polymers always results in inhomogeneity of particle distribution in polymer matrix with limited bioactivity. This study sets out to apply the pulsed laser deposition (PLD) technique to prepare uniform akermanite (Ca2MgSi2O7, AKT) glass nanocoatings on the surface of two polymers (non-degradable polysulfone (PSU) and degradable polylactic acid (PDLLA)) in order to improve their surface osteogenic and angiogenic activity. The results show that a uniform nanolayer composed of amorphous AKT particles (∼30nm) of thickness 130nm forms on the surface of both PSU and PDLLA films with the PLD technique. The prepared AKT-PSU and AKT-PDLLA films significantly improved the surface roughness, hydrophilicity, hardness and apatite mineralization, compared with pure PSU and PDLLA, respectively. The prepared AKT nanocoatings distinctively enhance the alkaline phosphate (ALP) activity and bone-related gene expression (ALP, OCN, OPN and Col I) of bone-forming cells on both PSU and PDLLA films. Furthermore, AKT nanocoatings on two polymers improve the attachment, proliferation, VEGF secretion and expression of proangiogenic factors and their receptors of human umbilical vein endothelial cells (HUVEC). The results suggest that PLD-prepared bioceramic nanocoatings are very useful for enhancing the physicochemical, osteogenic and angiogenic properties of both degradable and non-degradable polymers for application in bone replacement/regeneration.

Handmade clay balls and recycled crush glass as alternative media in water filtration

For many years materials such as quarried sand, anthracite, and granular activated carbon have been the principal media-products traditionally used in water and wastewater filtration plants. Pebble Matrix Filtration (PMF) is a novel non-chemical, sustainable pre-treatment method of protecting Slow Sand Filters (SSF) from high turbidity during heavy monsoon periods. PMF uses sand and pebbles as the filter media and the sustainability of this new technology might depend on availability and supply of pebbles and sand, both finite resources. In many countries there are two principal methods of obtaining pebbles and sand, namely dredging from rivers and beaches, and due to the scarcity of these resources in some countries the cost of pebbles is often 4-5 times higher than that of sand. In search for an alternative medium to pebbles after some preliminary laboratory tests conducted in Colombo-Sri Lanka, Poznan-Poland and Cambridge-UK, a 100-year-old brick factory near Sudbury, Suffolk, has produced hand-made clay pebbles satisfying the PMF quality requirements. As an alternative to sand, crushed recycled glass from a UK supplier was used and the PMF system was operated together with hand-made clay balls in the laboratory for high turbidity removal effectively. The results of laboratory experiments with alternative media are presented in this paper. There are potential opportunities for recycled crushed glass and clay ball manufacturing processes in some countries where they can be used as filter media.

Google Glass as a technique of self and the revitalisation of the monad

As the boundaries between public and private, human and technology, digital and social, mediated and natural, online and offline become increasingly blurred in modern techno-social hybrid societies, sociology as a discipline needs to adapt and adopt new ways of accounting for these digital cultures. In this paper I use the social networking site Pinterest to demonstrate how people today are shaped by, and in turn shape, the digital tools they are assembled with. Digital sociology is emerging as a sociological subdiscipline that engages with the convergence of the digital and the social. However, there seems to be a focus on developing new methods for studying digital social life, yet a neglect of concrete explorations of its culture. I argue for the need for critical socio-cultural ‘thick description’ to account for the interrelations between humans and technologies in modern digitally mediated cultures.

Numerical modelling and analysis of the blast performance of laminated glass panels and the influence of material parameters

This paper presents a comprehensive numerical procedure to treat the blast response of laminated glass (LG) panels and studies the influence of important material parameters. Post-crack behaviour of the LG panel and the contribution of the interlayer towards blast resistance are treated. Modelling techniques are validated by comparing with existing experimental results. Findings indicate that the tensile strength of glass considerably influences the blast response of LG panels while the interlayer material properties have a major impact on the response under higher blast loads. Initially, glass panes absorb most of the blast energy, but after the glass breaks, interlayer deforms further and absorbs most of the blast energy. LG panels should be designed to fail by tearing of the interlayer rather than failure at the supports to achieve a desired level of protection. From this aspect, material properties of glass, interlayer and sealant joints play important roles, but unfortunately they are not accounted for in the current design standards. The new information generated in this paper will enhance the capabilities of engineers to better design LG panels under blast loads and use better materials to improve the blast response of LG panels.

Stoichiometry, crystallinity, and nano-scale surface morphology of the graded calcium phosphate-based bio-ceramic interlayer on Ti-Al-V

A plasma-assisted concurrent Rf sputtering technique for fabrication of biocompatible, functionally graded CaP-based interlayer on Ti-6Al-4V orthopedic alloy is reported. Each layer in the coating is designed to meet a specific functionality. The adherent to the metal layer features elevated content of Ti and supports excellent ceramic-metal interfacial stability. The middle layer features nanocrystalline structure and mimics natural bone apatites. The technique allows one to reproduce Ca/P ratios intrinsic to major natural calcium phosphates. Surface morphology of the outer, a few to few tens of nanometers thick, layer, has been tailored to fit the requirements for the bio-molecule/protein attachment factors. Various material and surface characterization techniques confirm that the optimal surface morphology of the outer layer is achieved for the process conditions yielding nanocrystalline structure of the middle layer. Preliminary cell culturing tests confirm the link between the tailored nano-scale surface morphology, parameters of the middle nanostructured layer, and overall biocompatibility of the coating.

A comparative study of Sr-incorporated mesoporous bioactive glass scaffolds for regeneration of osteopenic bone defects

SUMMARY: Recently, the use of the pharmacological agent strontium ranelate has come to prominence for the treatment of osteoporosis. While much investigation is focused on preventing disease progression, here we fabricate strontium-containing scaffolds and show that they enhance bone defect healing in the femurs of rats induced by ovariectomy. INTRODUCTION: Recently, the use of the pharmacological agent strontium ranelate has come to prominence for the treatment of osteoporosis due to its ability to prevent bone loss in osteoporotic patients. Although much emphasis has been placed on using pharmacological agents for the prevention of disease, much less attention has been placed on the construction of biomaterials following osteoporotic-related fracture. The aim of the present study was to incorporate bioactive strontium (Sr) trace element into mesoporous bioactive glass (MBG) scaffolds and to investigate their in vivo efficacy for bone defect healing in the femurs of rats induced by ovariectomy. METHODS: In total, 30 animals were divided into five groups as follows: (1) empty defect (control), (2) empty defects with estrogen replacement therapy, (3) defects filled with MBG scaffolds alone, (4) defects filled with MBG + estrogen replacement therapy, and (5) defects filled with strontium-incorporated mesopore-bioglass (Sr-MBG) scaffolds. RESULTS: The two groups demonstrating the highest levels of new bone formation were the defects treated with MBG + estrogen replacement therapy and the defects receiving Sr-MBG scaffolds as assessed by μ-CT and histological analysis. Furthermore, Sr scaffolds had a reduced number of tartrate-resistant acid phosphatase-positive cells when compared to other modalities. CONCLUSION: The results from the present study demonstrate that the local release of Sr from bone scaffolds may improve fracture repair. Future large animal models are necessary to investigate the future relationship of Sr incorporation into biomaterials.

Improvement of the mode II interface fracture toughness of glass fiber reinforced plastics/aluminum laminates through vapor grown carbon fiber interleaves

The effects of acid treatment, vapor grown carbon fiber (VGCF) interlayer and the angle, i.e., 0° and 90°, between the rolling stripes of an aluminum (Al) plate and the fiber direction of glass fiber reinforced plastics (GFRP) on the mode II interlaminar mechanical properties of GFRP/Al laminates were investigated. The experimental results of an end notched flexure test demonstrate that the acid treatment and the proper addition of VGCF can effectively improve the critical load and mode II fracture toughness of GFRP/Al laminates. The specimens with acid treatment and 10 g m−2 VGCF addition possess the highest mode II fracture toughness, i.e., 269% and 385% increases in the 0° and 90° specimens, respectively compared to those corresponding pristine ones. Due to the induced anisotropy by the rolling stripes on the aluminum plate, the 90° specimens possess 15.3%–73.6% higher mode II fracture toughness compared to the 0° specimens. The improvement mechanisms were explored by the observation of crack propagation path and fracture surface with optical, laser scanning and scanning electron microscopies. Moreover, finite element analyses were carried out based on the cohesive zone model to verify the experimental fracture toughness and to predict the interface shear strength between the aluminum plates and GFRP laminates.