School of Engineering

Materials group staff

Dr. Philip Harrison

Dr. Graham Green

Dr. Ronald Thomson

Dr. Safa A. Hashim

Materials group

The research work of the Materials Group focuses on the themes of rapid manufacture, adhesive bonding, process and materials modelling and experimental characterisation. Materials of particular interest within the group include: adhesives, advanced composites, technical textiles, smart and porous materials. Application areas include: bioengineering, aeronautics, marine, military and automotive. Our materials-modelling work combines continuum mechanics and cohesive zone modelling with multi-scale / multi-physics simulations and involves the development of novel constitutive models and numerical algorithms to couple predictions across the length scales. Many of our projects are interdisciplinary with cross-cutting themes such as chemical synthesis and structural properties or physics and manufacturing. Projects involve several national and international collaborations with leading researchers in other academic institutions and also with industry and the NHS. Some of our ongoing research projects are:


Virtual forming of engineering fabrics and textile composites

Mr Farag Ebdewe, Dr Philip Harrison

Advanced textile composites lie at the centre of the cost-performance spectrum of structural materials and are attracting growing interest from both the academia and industry. This research is driven by the anticipated need to design, process and model with these materials. In particular, constitutive models based on multi-scale analysis are being developed and implemented in finite element software (e.g. AbaqusTM) to create a virtual manufacturing environment for the composite forming process (see figure). The aim here is to predict the forming behaviour of these materials from information such as fibre volume fraction, textile weave style and matrix rheology. In addition, novel algorithms to incorporate off-the-roll fibre direction variability, as measured from several commercially available textiles, are being developed. Further challenges include: modelling multi-layer forming and characterization of inter-ply and tool/ply friction. Models are validated through an experimental program employing specialised equipment including novel shear-characterisation apparatus and a custom designed thermoforming station. A PhD student, Mr Farag Ebdewe, is currently working in this area in collaboration with partners at the Universities of Nottingham, Newcastle and Seoul National University.


Development a virtual design tool for magneto-rheological elastomers

Ms Gerlind Schubert, Dr Philip Harrison

Magneto-Rheological Elastomers (MREs) are smart materials that change their stiffness when subjected to magnetic fields. They offer great promise in the design of variable stiffness devices that can be used to control vibration dynamics (e.g. mounts for auto engines) and can be incorporated in vibration energy harvesting systems or active suspension (e.g. air suspension in vehicles). Understanding the relationship between manufacture conditions, microstructure and macro-scale behaviour of MREs is a challenge and a generalised constitutive model for MREs is lacking, making it currently impossible to simulate and optimise the design of MRE applications in a virtual environment. Given the importance of computer aided engineering in today’s design methodology, this is clearly a significant obstacle preventing widespread exploitation of MREs. Thus the goals of the project are to manufacture MREs and determine the influence of manufacture conditions, such as iron particle loading, matrix properties and magnetic field strength during cure, on the micro-structure and magnetic-sensitivity of the resulting MRE. Experiments will be used to evaluate multi-scale / multi-physics modelling of the material (using COMSOL – see figure). A  PhD student, Ms Gerlind Schubert, is currently working in this area, in close collaboration with partners at the University of Newcastle.


Multi-scale modelling of porous structures

Mr Qusai Hatem, Mr Jafar Alsayednoor, Dr Philip Harrison

Porous materials are an important class of materials that have found numerous applications in areas including: structures, filters, impact protection & energy absorption and catalysts, to name a few. This project aims to use multi-scale modelling strategies both to predict the macro-scale response of porous materials from a description of the porous skeletal microstructure and inversely, to determine the mechanical properties of the underlying skeletal microstructure from a description of the skeletal geometry and knowledge of the material’s macro-scale mechanical response (e.g. for cross linked-aerogels). Current modelling work is focusing on the development of numerical algorithms to produce isotropic, fully random Representative Volume Elements (RVEs) that can provide an accurate description of the porous microstructure for computational homogenization techniques. Experimental work is focusing on methods to characterize large scale deformation of transversely isotropic compressible materials and relate this back to the foams microstructure using x-ray CT imaging (see figure). Two PhD students are currently working in this area; Mr Jafar Alsaydenoor and Mr Qusai Hatem in collaboration with academic partners at the University of Newcastle, Missouri University of Science and Technology in the USA and industrial partners at NMC, Belgium.


Characterisation and constitutive modelling of shape-memory polymers

Mr Haedong Park, Dr Philip Harrison

Shape Memory Polymers (SMPs) are remarkable materials capable of memorising a permanent shape, being subsequently programmed to adopt a second, temporary shape, then reverting back to their original, permanent configuration, usually after the application of a trigger mechanism such as heat. SMPs have possible applications in a variety of fields, for example, in bioengineering as self-deploying arterial stents and artificial muscles, in space as self-deploying structures and in automotive as self healing structural foams. A current barrier to the wider application of SMPs is the lack of computational design tools to support virtual optimisation of SMP-based components. The aim of this project is to characterise and model the thermo-mechanical behaviour of SMPs. Further, in order to enable magnetic induction heating and also to enhance mechanical properties, magnetite nano-particles will be incorporated into the neat SMP. A commercial multi-physics FEM code (COMSOL) will be used to understand the effect of manufacture conditions on the magnetite / SMP nano-composite (see figure) and computational homogenisation techniques will be used to predict the relationship between nano-structure and mechanical / physical properties. This work is conducted in close collaboration with partners at Seoul National University.


Nano/micro fabrication of 3D structures using a multi-layered approach

Mr Abdulbast Kriama, Dr Graham Green

This work seeks to simultaneously fabricate a sacrificial mould, having the inverse shape of a desired device structure, and the actual structure using electro-deposition techniques. The mould is constructed of many thin layers using a photo-resist material that is dissolvable and sensitive to UV light. At the same time the device is created in the emerging mould layers using Gold electro-deposition techniques. Choosing to fabricate the mould and the 3D structures in multiple thin layers allows for the use of UV light and permits the potential cost-effective realization of complex 3D curved surfaces. A 5-layer demo device has so far been produced (see Figure). The longer term aim is to develop the above process to allow the manufacture of complex nano/micro-moulds to allow manufacture by deep drawing and other forming processes.


Micro deep drawing process

Mr Ihsan Irthiea, Dr Graham Green

The micro deep drawing process is defined as the forming of sheet metal blank material with overall part dimensions smaller than 1 mm. Typically the blank material will be less than or equal to 50?m thick. One of the main factors influencing the formability of the blank material is the number of grains in the thickness direction. A key quality issue is the avoidance of wrinkling or tearing of the blank material during the deep-drawing process. It has been identified that the frictional and geometric contact details between the blank and the supporting materials is crucially important. Additionally a soft punch made from urethane rubber would be utilized in the process being developed in this project. The aim of the project is to develop a test prototype machine (see Figure) that will allow optimisation of the various process parameters and the realisation of a robust micro deep drawing manufacturing process.


 

Delamination of hybrid steel/CFRP adhesive joints

Dr. Safa A. Hashim

The project aims to study the design, fabrication and failure of long-overlap double lap shear (DLS) joints up to 400mm long and where the CFRP composite laminate is the outer adherend.  This involves mechanical testing of DLS joints (see photo) and various constituent materials to determine their properties for numerical modelling.  Double cantilever beam (DCB) and other specimens are tested to determine fracture energy and stiffness parameters for the development of traction-separation model for cohesive zone modelling (CZM) in ABAQUS to study damage mechanics within the adhesive and the epoxy resin within the carbon fibre composite laminates. The CZM approach is also compared with equivalent FEA models based the continuum mechanics approach. Parameters of joint geometry, type of adhesive and laminate stacking sequences are included in this study. This study is supported by the MARSTRUCT research network of excellence on marine structures.


 

Optimisation and modelling of bondable GFRP pultrusion

Dr. Safa A. Hashim

This investigates the failure and behaviour of adhesive bonded pultriusion joints for structural applications, typically for ships and similar constructions. The work involves the development of a “pseudo pultrusion” tool to produce 10x10mm laminates (see photo) using the manufacturers’ recommended moulding materials such as glass fibre, vinyl ester resin, filler and mould release agent.  The moulded laminates are then adhesive (epoxy) bonded into tensile and shear specimens and tested to destruction to study the intralaminar and interlaminer glass fibre reinforced polymer (GFRP) failure. Among the study parameters is the fabric architecture of the top composite layers. These are optimised in relation to adhesion strength of the joint. In addition, multi-scale FEA models are used at macro, meso and micro-scale levels to determine the failure stresses, especially the transverse intralaminer stresses at micro-scale between individual filament and resin matrix.  This study is supported by Exel Composites (UK) Ltd.