Idris K. Mohammed

Modelling the deformation of a confectionery wafer as a non-uniform sandwich structure

The aim of this research was to model the mechanical behaviour of wafers found in various confectionery products in order to optimise the manufacturing stage. Compression and bending tests showed that the mechanical behaviour of the wafer was characteristic of a brittle foam. The internal microstructure of the wafer sheet was examined with an optical microscope which showed that the wafer possessed a sandwich structure with a porous core between two denser skins. An analytical model was developed to calculate the individual moduli of the wafer core and skin sections. These modulus values were used in a finite element (FE) model which consisted of a simple repetitive geometry. The FE model simulated the linear deformation of the wafer under compression and bending. The predictions from the analytical and numerical models were compared. They were found to agree in compression but deviated under bending due to the large mismatch of the core and skin moduli.

A Comparison of the Mechanical and Sensory Properties of Baked and Extruded Confectionery Products

Traditional baking is the most common way of producing confectionery wafers, however over the past few decades, the extrusion process has become an increasingly important food manufacturing method and is commonly used in the manufacturing of breakfast cereals and filled snack products. This study aims to characterise products made via each of these manufacturing processes in order to understand the important parameters involved in the resulting texture of confectionery products such as wafers. Both of the named processes result in brittle, cellular foams comprising of cell walls and cell pores which may contain some of the confectionery filling. The mechanical response of the cell wall material and the geometry of the products influence the consumer perception and preference. X-Ray micro tomography (XRT) was used to generate geometry of the microstructure which was then fed to Finite Element (FE) for numerical analysis on both products. The FE models were used to determine properties such as solid modulus...

Microstructural Consequences of Blast Lung Injury Characterized with Digital Volume Correlation

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 kPa 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. This 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 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 characterise 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 inter-dependency and neighbouring tissue burden as a result of focal injury). Digital volume correlation techniques show great promise as a tool to advance this endeavour, providing a new perspective on lung mechanics post-blast.

On the use of HCP and FCC RVE structures in the simulation of powder compaction

Use of hexagonal close packed and face centered cubic structures to simulate powder compaction reveals that plastic deformation is effective in reducing porosity until a relative density of 0.96, beyond which a drastic rise in pressure is required. The compaction process can be divided into three phases demarcated by relative densities of 0.8 and 0.92, characterized, respectively, by local yielding around the initial contact point, coalescence of locally yielded zones and full plastic flow to reduce pores. The macroscopic yield behaviour of the powder assembly in the present work agrees reasonably with analytical and numerical models such as the Storåkers-Fleck-McMeeking model and multi-particle finite element model. It is found that for rate-dependent powder materials, the compaction process is noticeably rate dependent from a relative density of 0.85. Although a regular packing of powders is unrealistic, the understanding gained from a regular packing model provides insight into the role that plastic deformation plays during powder compaction.

Quantifying the differences in structure and mechanical response of confectionery products resulting from the baking and extrusion processes

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.

A systematic approach to the formulation of anti-onychomycotic nail patches

Graphical abstract Figure. No caption available. &NA; 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 the nature 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.

Methodology for Modelling Diffusion Bonding in Powder Forging

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.