13 results found
Zhang X, Mohammed IK, Zheng M, et al., 2019, Temperature effects on the low velocity impact response of laminated glass with different types of interlayer materials, International Journal of Impact Engineering, Vol: 124, Pages: 9-22, ISSN: 0734-743X
This paper investigates the influence of the interlayer material on the low velocity impact performance of laminated glass. The effect of temperature (50°C, 23°C, 0°C and −30°C) has been explored to observe damage mechanisms and the associated impact resistant properties of the laminated glass. The four interlayer materials investigated were: SGP – ionoplast as employed in Sentry Glas® Plus, TPU – thermo-plastic polyurethane, PVB – polyvinyl butyral and a TPU/SGP/TPU hybrid interlayer. The impact resistance was measured in terms of load peak, absorbed energy, ultimate deformation and crack patterns. The low velocity impact results indicated that both the type of the interlayer materials and testing temperature have great influence on the impact resistant properties of the laminated glass. The laminated glass with SGP interlayer exhibited best impact resistant properties amongst the four structures at room temperature. However, as the temperature was varied, the TPU/SGP/TPU hybrid interlayer performed the best over the entire range of temperatures tested, which can better ensure the safety of the occupants in the vehicle. This is because the elastic and viscous properties of the interlayer materials greatly changes with the temperature caused by the different glass transition temperatures of the interlayer materials.
Butt S, Mohammed I, Raghavan V, et al., 2018, Quantifying the differences in structure and mechanical response of confectionery products resulting from the baking and extrusion processes, Journal of Food Engineering, Vol: 238, Pages: 112-121, ISSN: 0260-8774
Extrusion has potential advantages over baking in terms of throughput, asset cost and flexibility. However, it is challenging to achieve through extrusion the “light, crispy” texture of a more traditional baked confectionery. This study compares and contrasts for the first time confectionery products produced through these two processes, i.e. baking and extrusion. The microstructural differences are measured using imaging techniques, i.e. Scanning Electron Microscopy (SEM) and X-Ray Tomography (XRT) whereas mechanical characterisation is used to highlight differences in the resulting mechanical properties. Crucial information is presented which shows that the two technologies result in different mechanical properties and microstructures, even if the level of porosity in the two products is kept constant. In addition, confectionery products whether they are produced through baking or extrusion, have irregular geometries. The latter makes mechanical characterisation a real challenge. Therefore this study also presents rigorous methods for measuring true mechanical properties such that meaningful and valid comparisons may be made. The accuracy of the chosen methodologies is verified through experiments using flat and tubular extruded geometries as well as testing the products in various directions. It was concluded that the manufacturing method and, in the case of extrusion, the initial moisture content influences the microstructure and mechanics of confectionery products, both of which have an impact on consumer sensory perception.
Zhang B, Mohammed IK, Wang Y, et al., 2018, On the use of HCP and FCC RVE structures in the simulation of powder compaction, JOURNAL OF STRAIN ANALYSIS FOR ENGINEERING DESIGN, Vol: 53, Pages: 338-352, ISSN: 0309-3247
Kinloch AJ, Rizi K, Mohammed IK, et al., 2018, A systematic approach to the formulation of anti-onychomycotic nail patches, European Journal of Pharmaceutics and Biopharmaceutics, Vol: 127, Pages: 355-365, ISSN: 0939-6411
Nail patches have a potential role as drug carriers for the topical treatment of nail diseases such as onychomycosis, a common condition. Our aim was therefore to develop a systematic and novel approach to the formulation of a simple drug-in-adhesive ungual patch. Twelve pressure-sensitive adhesives (PSAs), four backing membranes, two release liners and three drugs were screened for pharmaceutical and mechanical properties. From this initial screening, two PSAs, two drugs, one backing membrane and one release liner were selected for further investigation. Patches were prepared by solvent-casting and characterised. The patches had good uniformity of thickness and of drug content, and showed minimal drug crystallisation during six months of storage. Meanwhile, the drug stability in the patch upon storage and patch adhesion to the nail was influenced by thenature of the drug, the PSA and the backing membrane. The reported methodology paves the way for a systematic formulation of ungual nail patches to add to the armamentarium of nail medicines. Further, from this work, the best patch formulation has been identified.
arora H, nila A, Vitharana K, et al., 2017, Microstructural consequences of blast lung injury characterised with digital volume correlation, Frontiers in Materials, Vol: 4, ISSN: 2296-8016
This study focuses on microstructural changes that occur within the mammalian lung when subject to blast and how these changes influence strain distributions within the tissue. Shock tube experiments were performed to generate the blast injured specimens (cadaveric Sprague-Dawley rats). Blast overpressures of 100 and 180 kPa were studied. Synchrotron tomography imaging was used to capture volumetric image data of lungs. Specimens were ventilated using a custom-built system to study multiple inflation pressures during each tomography scan. These data enabled the first digital volume correlation (DVC) measurements in lung tissue to be performed. Quantitative analysis was performed to describe the damaged architecture of the lung. No clear changes in the microstructure of the tissue morphology were observed due to controlled low- to moderate-level blast exposure. However, significant focal sites of injury were observed using DVC, which allowed the detection of bias and concentration in the patterns of strain level. Morphological analysis corroborated the findings, illustrating that the focal damage caused by a blast can give rise to diffuse influence across the tissue. It is important to characterize the non-instantly fatal doses of blast, given the transient nature of blast lung in the clinical setting. This research has highlighted the need for better understanding of focal injury and its zone of influence (alveolar interdependency and neighboring tissue burden as a result of focal injury). DVC techniques show great promise as a tool to advance this endeavor, providing a new perspective on lung mechanics after blast.
Chong HM, Mohammed IK, Linter B, et al., 2017, Mechanical and microstructural changes of cheese cracker dough during baking, LWT- Food Science and Technology, Vol: 86, Pages: 148-158, ISSN: 0023-6438
Baked food snacks constitute an important market as a popular consumer product. The mechanical properties of cheese cracker dough at different stages of baking have been investigated as they can relate to the product's texture. The change in mechanical properties during baking was measured whilst the corresponding changes in microstructure were recorded using cryo-SEM at several interrupted baking conditions. The initial modulus of the dough increased with baking time due to starch melting or gelatinisation, melting of fat globules and evaporation of water. Simultaneously gas cells were found to begin forming. The data derived from the uniaxial compression, tension and shear experiments showed that the dough exhibited a rate dependent behaviour at all stages of baking with a power law index of approximately 0.2. Rheometric tests under dynamic heating conditions were also performed and it was found that the modulus decreased significantly, from 150 kPa to 10 kPa, with the initial rise in temperature. This study provides useful data for understanding the evolution of microstructure and rheology during the baking process and its impact on the texture of the final product.
Vandenberghe E, Charalambides MN, Mohammed IK, et al., 2017, Determination of a critical stress and distance criterion for crack propagation in cutting models of cheese, Journal of Food Engineering, Vol: 208, Pages: 1-10, ISSN: 0260-8774
A critical stress at a critical distance crack propagation criterion is a good way to model the fracture in cheese. This physical criterion states that the crack-tip node debonds when the stress at a specified distance ahead of the crack tip on the assumed crack path reaches a critical value. Although this criterion is already used in other research domains, no consistent information exists on how the critical stress and distance should be determined.A repeatable method for the determination of this criterion which combines experimental and numerical single edge notched bending tests was acquired. This criterion was validated with wire cutting experiments of cheese. The experimental and numerical results showed the same trend with a clear wire indentation and steady state cutting phase. The determination of a critical stress and distance criterion as proposed in this research is a good approach to model fracture and cutting of cheese.
Wang Y, Mohammed IK, Balint DS, 2016, Methodology for modelling diffusion bonding in powder forging, 16th Metal Forming International Conference, Publisher: Trans Tech Publications Inc., Pages: 817-823, ISSN: 1013-9826
Interfacial bonding has a significant influence on the quality of processed components formed by powder forging. Consequently, modelling the bonding process is important for controlling the condition of the components and predicting optimum forging process parameters (e.g. forming load, temperature, load-holding time, etc.). A numerical model was developed in the present work to simulate diffusion bonding (DB) during the direct powder forging (DF) process. A set of analytical equations was derived and implemented in the finite element (FE) software Abaqus via a user-defined subroutine. The DB model was validated using a two-hemisphere compression simulation. The numerical results demonstrated that the DB model has the ability to: 1) determine the bonding status between powder particles during the forging process, and 2) predict the optimum value for key powder forging process parameters. The DB model was also implemented in a representative volume element (RVE) model which was developed in an earlier work to simulate the powder forging process by considering particle packing and thermo-mechanical effects.
Kinloch AJ, mohammed IK, Charalambides MN, 2016, Modelling the Peeling Behavior of Soft Adhesives, 21st European Conference on Fracture, ECF21, 20-24 June 2016, Catania, Italy, Publisher: Elsevier, Pages: 326-333
Peel tests were performed on pharmaceutical drug patches which consisted of a polyester backing membrane supporting an acrylic pressure-sensitive adhesive (PSA) (without and with an anti-fungal drug present) adhered to a polyethylene substrate. Interfacial separation of the PSA from the polyethylene substrate was observed in most cases. Finite element (FE) peeling simulations were conducted which characterized the backing-membrane as an elasto-plastic power-law material, the PSA as a viscoelastic material and the interfacial properties with a cohesive zone model (CZM). The mechanical response of the backing membrane and the PSA were measured from tensile experiments while the rate-dependent cohesive zone parameters, i.e. the fracture energy and maximum stress, were measured directly from poker-chip probe tack tests. The numerical results from the CZM/FE simulations and the experimental values of the peel forces as a function of the peel angle, peel speed and PSA thickness were found to be in good agreement. Two different anti-fungal drugs were added to the PSA and the influence of the drug was investigated using contact angle measurements, tensile tests, dynamic mechanical analysis and peel tests.
Mohammed IK, Charalambides MN, Kinloch AJ, 2016, Modeling the effect of rate and geometry on peeling and tack of pressure-sensitive adhesives, Journal of Non-Newtonian Fluid Mechanics, Vol: 233, Pages: 85-94, ISSN: 0377-0257
A model is developed for predicting separation along interfaces of pressure sensitive adhesives. Many authors have used the cohesive zone approach to solve such problems but the parameter calibration of such models remains uncertain. This study reports a novel method for determining such parameters. In addition, it provides crucial evidence for the suitability of the cohesive zone model approach in modelling interface fractures.Peel tests were performed at various rates using specimens which consisted of a polyester backing membrane supporting an acrylic pressure-sensitive adhesive (PSA) adhered to a polyethylene substrate. Interfacial separation of the PSA from the polyethylene substrate was observed. Finite element (FE) peeling simulations were conducted which modeled the backing-membrane as an elasto-plastic power-law material, the adhesive as a viscoelastic material and the interfacial properties with a cohesive zone model (CZM). The material properties of the backing membrane and the pressure-sensitive adhesive were measured from tensile and stress relaxation experiments. The rate-dependent CZM parameters were measured directly from poker-chip probe-tack tests which were performed at pull-off speeds which corresponded to the rates employed for the peel tests. The effect of the PSA thickness and test rate on both tack and peel was investigated experimentally, as well as modeled numerically. Good agreement was found between the experimentally measured and numerically predicted peel forces for different peel angles, speeds and PSA thicknesses. In addition, it was proven that the rate dependence observed in the peel and probe-tack data was dominated by the rate dependence of the interface properties, i.e. the time dependence of the two CZM parameters of maximum stress and fracture energy, rather than the time-dependent bulk viscoelasticity of the PSA peel arm.
Kinloch AJ, Mohammed IK, Charalambides MN, 2014, Modelling the interfacial peeling of pressure-sensitive adhesives, Journal of Non-Newtonian Fluid Mechanics, Vol: 222, Pages: 141-150, ISSN: 1873-2631
Peel tests were performed using specimens which consisted of a polyester backing membrane supporting an acrylic pressure-sensitive adhesive adhered to a polyethylene substrate. Interfacial separation of the PSA from the polyethylene substrate was observed. Finite element (FE) peeling simulations were conducted which modelled the backing-membrane as an elasto-plastic power-law material, the adhesive as a viscoelastic material and the interfacial properties with a cohesive zone model (CZM). The material properties of the backing membrane and the pressure-sensitive adhesive were measured from tensile and stress relaxation experiments. The cohesive zone parameters were calculated analytically from the peel test data, as well as being measured directly from independent poker-chip probe tack tests. The numerical results from the CZM/FE simulations and the experimental values of the peel forces as a function of the peel angle were found to be in good agreement.
Mohammed IK, Charalambides MN, Williams JG, et al., 2014, Modelling the microstructural evolution and fracture of a brittle confectionery wafer in compression, INNOVATIVE FOOD SCIENCE & EMERGING TECHNOLOGIES, Vol: 24, Pages: 48-60, ISSN: 1466-8564
Mohammed IK, Charalambides MN, Williams JG, et al., 2013, Modelling the deformation of a confectionery wafer as a non-uniform sandwich structure, JOURNAL OF MATERIALS SCIENCE, Vol: 48, Pages: 2462-2478, ISSN: 0022-2461
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