I am a fellow of the Institute of Materials, Minerals and Mining, having been elected in 2015. I'm a member of the Institute of Physics, elected in 2005 and chartered as an engineer and scientist through the IoM3 from 2011.
My PhD title was "The Interaction of Nano-Composite Particles with a Polyester Resin and the Effect on Mechanical Properties."
- Modification of composite systems
- The role of the interface and the interphase in controlling mechanical properties
- Natural fibres and resin systems for composite materials
- Mechanical performance of engineering materials.
Current collaborations include:
- Thames Water Utilities Limited
The interface between the matrix and reinforcing phases can have a significant effect on the mechanical properties of the resulting composite material. The interface can be studied by a number of surface analysis techniques and the interaction modelled. Such studies, and such modelling, can help understanding of the mechanisms which composites undergo during their lifetime. The current review discusses the role of the interface and the methods by which it can be studied; two case studies are presented which illustrate these methods and the value that such knowledge of the interface has brought to larger investigations.
In order to assess the remaining life of cast iron assets in the water sector, an understanding of their fracture and fatigue characteristics is necessary. The present work is concerned with the toughness and Paris crack growth behaviour of cast iron materials with a range of micro-structures, taken from trunk mains currently in service. When considered with other data from the literature, the results from the present study enable the range of fatigue crack growth behaviour likely to be seen in service to be quantified. The role of microstructure in fracture and fatigue behaviour is discussed. Calculations of fatigue life based on integration of the Paris law are then carried out and compared with previously published data for samples from cast iron distribution mains. The results from these investigations support the development of asset management tools for use in the water industry. (C) 2010 Elsevier B.V. All rights reserved.
Full-scale tests have been carried out on lengths of unrestrained and restrained plain and jointed distribution pipe sections (similar to 4 '' or similar to 100 mm internal diameter) in order to investigate the strains and loads generated in cast iron water distribution mains as a result of temperature fluctuations. Tests on unrestrained sections enabled the coefficient of thermal expansion of the pipe material to be measured. In a fully restrained situation, which can occur in a pipe section in service when the joints are locked, tensile stresses arise from a decrease in temperature ( in accordance with the predictions of a simple one-dimensional model) and it is shown that these stresses are sufficiently high to fracture a corroded pipe. In situations where the tensile stress leads to joint slippage, leakage through the joint is observed. Water leakage was also observed through the wall of corroded pipes that retained sufficient structural stability to carry load without failure.
WX Weight of material to be managed by a particular option Abstract Waste is intricate to manage. With greater attention now being paid to the use of waste as a resource, there is an increasing need to develop sustainable and secure management options for the most complex material resource streams. In order to achieve this, it is necessary to look to those materials, which due to their complex structure have not traditionally been recycled, and so remain in the residual waste stream. This paper presents a methodology that has been developed to enable local authorities, or their equivalents, to assess the environmental and economic feasibility of collecting complex material streams separately, in order to improve their management of municipal solid waste. The methodology utilises available data from a number of sources, to determine the feasibility of options available. The methodology is applied to a case study in Surrey, England, in relation to the management of Absorbent Hygiene Products. Currently this waste is collected as part of the residual stream, and dealt with either through landfill or energy from waste. The result of applying the new methodology suggests that the optimum solution is the separate collection of Absorbent Hygiene Products and subsequent the sterilisation and recycling.
Organic-inorganic hybrid nano-particles have been synthesized via a modified Stöber method. Nano-particles have been prepared from silica precursors with different organic functionalities. Methyl, ethyl, vinyl and phenyl modified silicas have been synthesized with a view to using these particles as modifiers for polymers and polymer matrix composites. Nano-composites have been produced using polyester as a matrix. The effect of the nano-particles on the toughness of the polyester has been investigated and it is shown that the incorporation of nano-particles leads to an improvement in toughness. For the methyl, ethyl and vinyl ormosils (organically modified silicas) the improvement is minor. The phenyl ormosil gives a greater improvement. This is attributed to different toughening mechanisms.
Bio-derived fibres and resins are of increasing interest as alternatives to petrochemicals in the production of so-called environmentally friendly composite materials. However, whilst the majority of systems consider complete replacement, another route is to look at the constituents that are required to give certain properties, including the content of diluents; a third is to identify ‘hot spots’ in manufacturing. This paper considers these three possibilities in the context of the production of a resin system, and presents results from a life cycle assessment. The aim of this study was to make qualitative assertions based on quantitative estimates. The current work provides a practical assessment of the contribution of the manufacturing process of a multi-part resin formulation to a range of environmental impacts. As a part of this, a multi-stage methodology, the first of its kind, which is more relevant for the batch processes used to manufacture many structural thermosetting polymer systems, was developed. This was applied to a range of resins, some of which include bio-mass derived precursors. For the boundary conditions used, the indications are that the impacts due to taking the constituents and processing them to produce the resin system are insignificant compared with those due to producing the feedstocks in the first place. Surprisingly, whether the feedstocks were from fossil resources or were bioderived was of little significance. As a consequence of the analysis, it has been demonstrated that whilst a manufacturer can make significant savings through careful management of plant and the supporting energy mix, significant improvements to the environmental impacts of resin systems can be made through the choice of particular monomers.
Engineered Cement Composites (ECC) materials have the potential to be used in civil engineering applications where a level of ductility is required to avoid brittle failures. However uncertainties remain regarding mechanical performance, physical properties, shrinkage and durability. In the present work, specimens containing cement powder and admixtures have been manufactured following two different processes and tested mechanically. Multiple matrix cracking has been observed in both tensile and flexural tests and this leads to “strainhardening” behaviour. The results have been correlated with sample density and porosity and it is suggested that higher levels of porosity do not necessarily lead to a loss of the strain hardening capacity. Shrinkage has been investigated and it is shown, consistent with the literature, that shrinkage can be reduced both by controlling the initial environment to which the material is exposed and by the use of additives. Durability was assessed by flexure testing of beams specimens aged for different times. Initial testing (up to one year) indicates that the specimen retain ductility, although the initial cracking threshold increases with time – which may have implications for longer aging times.
The present work has been conducted in order to investigate the quality of impregnation of unsaturated polyester resin across the bleached alfa pulpboard, and evaluate the potential for the obtained compound to serve a purpose as a useful composite material. The ultra-low-angle Microtomy (ULAM) method was used to study the quality of impregnation of alfa fibres by unsaturated polyester resin. The cross-section through the bleached alfa pulpboard/unsaturated polyester material, which emphasised the impregnation zone, was analysed using X-ray photoelectron spectroscopy (XPS). The profiles obtained by the XPS line scan analysis of the tapered surface show a well-defined impregnation region. The depth of this region has been characterised using two chemical constituent peaks, which showed an approximate depth of impregnation of about 20 to 40 μm, on the basis of C-OH/C-O-C, components which are exactly complementary to the β-shifted carbon signal, employed as an analogue for the unsaturated polyester. A comparative study was also carried out between the mechanical and tribological properties of the composite material and the pure unsaturated polyester resin, in order to complement the results obtained by surface analysis. The comparison shows better stiffness, tensile strength at break and wears resistance in the reinforced unsaturated polyester resin. The results of this research demonstrate a good quality of impregnation of unsaturated polyester resin across the short alfa fibres which present the matrix and reinforcement of the studied composite material.
Expanded polystyrene (EPS) is a commonly used polymer in the packaging industry and for the thermal insulation of buildings. It has poor mechanical properties which limit its application in some areas. A heat treatment was carried out on a sample of EPS, in order to improve its mechanical properties. The treatment consists of operations that combine the heating and cooling of the material. It is executed to improve the characteristics of the treated polymer and make it more favourable for use in new applications. In the case of EPS, this process changes the behaviour of the polymer in a beneficial manner and maximizes its density and hardness. Indeed, the treated version shows interesting mechanical, tribological and hygroscopic properties. This improvement was obtained mainly due to the morphological modification of the structure of EPS. Indeed, heat treatment leads to the creation of a polystyrene crust which covers every EPS bead. This crust protects the cell structure of each bead against stretching and supports most of the load applied to the treated version of EPS. Thus, the treated EPS can be used not only for packaging and thermal insulation but also for more structural applications.
Digital Image Correlation (DIC) can be used to obtain full-field strain information of specimens under load. Through analysis of the resultant strain-contours, defects such as delaminations in composite materials can be detected based on their effect on the deformation behaviour. This paper focuses on the use of DIC to detect the presence of fully embedded artificial delaminations, introduced during the manufacturing process, inside a flat panel specimen under three-point bending. Two types of delamination insert have been considered: an insert containing two sealed pieces of PTFE, and an insert consisting of a single sheet of PTFE in combination with a stress-raiser. When tested in three-point bending, the position and approximate size of the delaminations were clearly visible due to the presence of a plateaux in the longitudinal surface strain profile. Finite element modelling predictions were in good agreement with the DIC measurements for both types of artificial delamination.
Digital Image Correlation (DIC) can be used to obtain full-field strain information on specimens under load. Through analysis of the resultant strain-contours, defects such as delaminations in composite materials can be detected, based on their effect on the deformation behaviour. This work focusses on the use of the DIC technique and two variations of active thermography (lock-in thermography and pulse thermography) for determining the lengths of delaminations in “milled-slot” specimens; for each technique, the measured delamination lengths have been compared with visually observed (i.e. photographed) delaminations grown under fatigue loading in transparent woven fabric GFRP specimens. In addition, the DIC results have been interpreted with the aid of a finite element model of the strain distribution in the milled-slot specimens. It has been found that the DIC technique provides a reasonably good method for measuring the length of the fatigue-grown delaminations after an empirical fit is applied, with the aid of the FE analysis, to overcome complications caused by fibre-bridging. On the other hand, the results using both lock-in and pulse thermography showed reasonable correlations with the visually observed (i.e. photographed) delamination lengths without the need for an empirical fit, although some post-processing of the data was required. For both thermography techniques, there were difficulties in determining the delamination lengths close to the edge of the milled slot.
Distribution networks are critical in providing continuous potable water supplies to households and businesses. Trunk mains are the major arteries of the distribution network and convey large volumes of water over long distances. Worldwide, much of this infrastructure is made of ageing cast iron and is deteriorating at different rates. Many of these mains are beginning to approach the end of their service lives (with some already exceeding their design life) and consequently out of large populations of pipes, some are failing, although some still have considerable residual life. Trunk main failures can have significant social, health and safety, environmental and economic impacts. It is therefore imperative to prevent the wide-scale failure of trunk mains through the implementation of proactive asset management strategies. Such approaches require accurate condition assessment data across the network in conjunction with deterioration modelling to predict how the assets' condition and performance changes over time. This work, being part of a wider collaborative project, has outlined a deterioration modelling framework on the basis of existing physical probabilistic failure models and research focussing on residual mechanical properties, corrosion and the NDT detection of flaws. The developed deterioration model can be used to characterise individual pipes (deterministic approach), as well as the cohort/network modelling of pipes (probabilistic approach). Deterioration is assumed to be predominantly based on corrosion. Previously this has been dealt with in a rather simplistic manner. The broader work has, on the one hand,shown that corrosion mechanisms are rather different than previously thought and, on the other, that their effect on a given pipe can be variable. A corrosion model capable of simulating the distribution of corrosion properties of the primary defects is to be incorporated within the proposed modelling framework and the development of important aspects of this model are discussed here. © 2014 WIT Press.
As part of an on going programme to characterise the residual properties and understand the failure mechanisms of in-service grey cast iron water pipes, the fatigue crack propagation behaviour of grey cast iron samples has been studied. Specimens were sourced from three ex-service pipes. For each pipe the microstructure and composition were characterised and the fracture toughness was determined. The fatigue behaviour was investigated in terms of the crack growth rate (da/dN) as a function of the applied stress intensity factor range. Clear differences in the fatigue behaviour of the samples from different pipes were observed. The result from these investigations, which indicate that microstructural differences play a role in mechanical behaviour, will support the development of asset management tools for use in the water industry.
This study was conducted to determine and analyse the influence of production process on the mechanical properties of bleached alfa pulpboard. Scanning electron microscopy showed that the industrial process currently used to produce the pulpboard causes small-scale and large-scale deformations in the alfa fibres. The same process results in a preferred orientation of the alfa fibres, leading to alignment in the rolling direction and hence there is some variation in the mechanical performance of the pulpboard in the different directions. Indeed, the mechanical properties show that the pulpboard loses its isotropic nature, mainly in the high-deformation regions. The pulpboard does not have the same mechanical characteristics in the longitudinal, 45°, and transverse directions. The samples taken in a longitudinal direction, which corresponds to the rolling direction, have better mechanical performance than in samples taken in the other two directions. Furthermore, the alkali (NaOH) treatment that is used to extract the alfa fibres from the alfa stems did not succeed in removing all of the non-cellulosic materials initially present in the alfa stems.
The surface of 316 stainless steel has been modified using cold atmospheric plasma (CAP) to increase the surface free energy (by cleaning the and chemically activating the surface)IN preparation for subsequent processes such as painting, coating or adhesive bonding. The analyses carried out, on CAP treated 316 stainless steel surfaces, includes X-ray photoelectron spectroscopy (XPS), imaging XPS (iXPS), and surface free energy (SFE) analysis using contact angle measurements.The CAP treatment is shown to increase the SFE of as-received 316 stainless steel from ~39 mJ m-1 to >72 mJ m-1 after a short exposure to the plasma torch. This was found to correlate to a reduction in adventitious carbon, as determined by XPS analysis of the surface. The reduction from ~90 at% to ~30% and ~39 at%, after being plasma treated for 5 minutes and 15 seconds respectively, shows that the process is relatively quick at changing the surface. It is suggested that the mechanism that causes the increase in surface free energy is chain scission of the hydrocarbon contamination triggered by free electrons in the plasma plume followed by chemical functionalisation of the metal oxide surface and some of the remaining carbon contamination layer.
Armour which is manufactured and distributed for personnel, vehicle and structural protection, primarily for military or policing applications, undergoes stringent testing to ensure that it can meet the demands of a range of impact scenarios. However, the effects of repetitive low-level damage are not fully understood and, in order to maintain a given level of protection, armour is recalled and replaced periodically, which is costly, and may be unnecessary. This paper reports preliminary studies on the relationship between minor damage and the resulting impact resistance of a woven fabric reinforced composite laminate (E-glass with epoxy resin). Specimens were subjected to displacement-controlled fatigue tests to introduce dispersed damage before being subjected to quasi-static indentation testing. The results showed that during penetration of the specimens, the peak load was reduced by approximately 10% for the pre-fatigued specimens, compared to the non-fatigued specimens, and there was some indication the energy absorption also reduced. It is proposed that the development of fibre fractures during the pre-fatigue of the specimens is the origin of these changes.
Mechanical properties of individual wood fibres and the characterisation of the interaction between wood fibres and resins are of interest to the composite wood panel industry and others involved in the fabrication of engineered wood products. However, the size of such fibres typically a few millimetres in length, makes characterisation of their mechanical properties difficult. Gripping fibres is problematic, not to mention the measurement of meaningful load displacement data. Using a novel three point bend test technique, the Young’s moduli of single wood fibres were determined. Fibres were placed on a specially designed test rig and a scanning probe microscope was used to apply a load and to measure the deflection at the centre of each fibre. A model of the fibre was produced in order to facilitate data analysis. The technique proved to be feasible, resulting in an average Young’s modulus value of 24.4 GPa for Pinus Sylvestris softwood fibres. This compares well with other values in the literature, but there is scope for improvement in the methodology to lead to more accurate measurements.
Innovation is critical to business. Sustainability is a global challenge requiring innovation. Many organizations have publicly committed to innovate towards environmental, social and economic sustainability, but a behaviour gap remains. In order to promote the effectiveness of these endeavours, there is a pressing need to understand the conditions for successful innovation towards sustainability, backed by empirical evidence. This paper complements prior work by developing a definition of sustainability-oriented innovation (building upon definitions of eco-innovation), and by discussing observations of this activity in practice. The paper presents an account of sustainability-oriented innovation at Interface, a global manufacturing company with radical sustainability goals. It expounds the contexts in which these innovations arose, focusing in particular on Net-Works, a radical, socially-minded fishing-net recycling programme. It was found that several unique factors contributed to success: adopting an existing route to market, partnering with an NGO, and learning from mistakes in a “safe failure space”.
Whilst superseded by other materials, there are many instances of engineering structures in use today that are formed of grey cast iron. These aging assets need to be assessed for their abilities to continue to function, and to predict performance in the event of engineering works being carried out on the asset, or nearby. Grey cast iron does not exhibit an obvious elastic regime when loaded in tension and is often classified in terms of minimum guaranteed tensile strength. Grey cast irons typically fail in brittle cleavage with a strain limit of
During the impact of thin composite panels, well-defined flaps can develop on the exit face as a consequence of through-thickness penetration of the panel. For certain materials (for example, CFRP panels based on plies of plain-woven fabric) the flaps develop as four triangles, with the apex of each triangle at the point of impact. As the impactor is driven through the panel, the flap (i.e. crack) lengths increase, until complete penetration of the panel by the impactor occurs. In the experiments described within this paper, CFRP panels fabricated from epoxy resin reinforced with plain-woven carbon fibre fabrics have been impacted using controlled multiple impact tests. During these tests, the impactor is driven at a controlled velocity to a particular depth of penetration through the composite panel, withdrawn, and then driven further through the panel subsequently. The experimental results show that the dependence of the flap compliance is proportional to the square of the flap length, which is in agreement with theoretical predictions. This compliance/crack-length also enables a toughness value for the composite panel to be derived that is directly relevant to through-thickness impact. The relationship of this toughness value to measurements of the mode I toughness of the composite panel using single edge notch specimens is also discussed.
Military personnel use protective armour systems that are frequently exposed to low-level damage, such as non-ballistic impact, wear-and-tear from everyday use, and damage during storage of equipment. The extent to which such low-level pre-damage could affect the performance of an armour system is unknown. In this work, low-level pre-damage has been introduced into a Kevlar/phenolic resin-starved composite panel using tensile loading. The tensile stress-strain behaviour of this eight-layer material has been investigated and has been found to have two distinct regions; these have been understood in terms of the microstructure and damage within the composite panels investigated using micro-computed tomography and digital image correlation. Ballistic testing carried out on pristine (control) and pre-damaged panels did not indicate any difference in the V50 ballistic performance. However, an indication of a difference in response to ballistic impact was observed; the area of maximal local out-ofplane deformation for the pre-damaged panels was found to be twice that of the control panels, and the global out-of-plane deformation across the panel was also larger.
The mechanical properties of cast iron used for trunk mains in the water industry have been studied. Specimens have been sourced from nine different pipes, which had been in service for up to 150 years before failure. The bulk microstructures of each cast iron have been analysed with regard to the graphite flake morphology and size. The stress strain behaviours in tension and compression have been derived from specimens loaded in flexure. Flexural strength data have been obtained for 30 specimens from each pipe (three batches of 10 from different locations along the length and around the circumference of the pipe) and these data have been analysed using Weibull methods. The depth of graphitisation visible on the fracture surface of each sample has been measured. It is shown that the strength of the cast iron samples decreases with increasing depth of graphitisation. When the layer of graphitised material is of reasonably uniform thickness, the strength reduction is modest, but where the section loss is more local, the strength reduction is more significant for some samples there is a reduction in strength of more than 50% when the depth of graphitisation exceeds 4 mm. Simple strength-of-materials and fracture mechanics approaches are shown to provide reasonable bounds for the data. (C) 2013 Elsevier B.V. All rights reserved.
Engineered Cement Composite (ECC) materials have the potential to be used in applications where a level of pseudo-ductility under tensile stress is required. Most previous work has focussed on comparatively thin specimens. For future civil engineering applications, however, it is imperative that the behaviour of thicker specimens is understood. In the present work, specimens containing cement powder, water, polymeric fibres and admixtures were manufactured following two different processes and tested in tension. Multiple matrix cracking was observed during tensile testing, leading to a pseudo-ductile behaviour. Complementary measurements of sample density and porosity suggest that a high porosity could be linked with an enhanced tensile strain-to-failure whereas high density is associated with a high maximum stress. The fibre dispersion, assessed by scanning electron microscopy, indicated that mechanical performance was enhanced with increasing proportion of fibres aligned along the tensile test axis, and this orientation can be linked to the manufacturing process.
Natural fibres have a plethora of interesting properties that make them suitable for a wide range of applications. In addition to some particular property (e.g. mechanical or thermal capacity), the ability to manufacture a product of comparatively low or even negative carbon footprint is frequently an important consideration. In some cases this claim requires close scrutiny due to the level of wastage in the crop, where fibres are derived from food-stuffs or where there is a need to use aggressive chemical treatments. Compared to the large body of work which has sought to use natural fibres either in a relatively raw state, or with simple processing to achieve yarns akin to wool and other materials for traditional textiles, this paper presents work on a fibre more analogous to technical fibres. Specifically, initial results from the manufacture of fibre reinforced polymer matrix composites using commercially available resin systems are discussed. The fibre is a commercially available viscose rayon of similar imensions to E-glass and in a continuous form. Whilst there are significant inputs in terms of the mechanical work and chemical treatments that are applied to biomass in order to produce the fibre, the fibre has the potential to produce composite laminates with higher fibre volume fractions and can be adopted easily into current fibre processes that utilise continuous synthetic fibres. Whilst the stiffness of the fibre is comparatively low (compared with carbon or glass) the strain to failure is much higher, which requires the use of a resin system with a similar strain to failure. Two such resin systems are considered (with and without the use of a coupling agent). Data are presented for the mechanical properties of the resultant composite materials. Whilst the properties are comparatively modest compared to glass and carbon based systems, they are potentially useful. Further, it is noted that the composite has the ability to recover, to some extent, from plastic yielding.
A strength of Digital Image Correlation (DIC) is the potential manoeuvrability of the system. It is noted, however, that by increasing the range of locations in which analysis is carried out, the number of uncontrollable variables grow. For example, when testing outside there may be changes to ambient lighting or there may be external vibrations occurring and these effects may alter measurement accuracy. The overall objective of this research is to quantify errors associated with the use of DIC in different (non-ideal) locations and, associated with this, to find methods of limiting the effect of the potential error sources. The reference test sample is a thin-walled shell into which defects can be introduced at specified locations, thus disturbing the local strain field. A portable test rig, which makes use of an internal vacuum, to cause a pressure differential on the component, has been designed and deployed to explore the potential of using DIC as a method of non-destructive evaluation. Preliminary results have been conducted in a laboratory setting to ensure that the strain data correlate with finite element analysis. Following from initial experimentation, successive investigations into the effects of possible external error sources have been conducted. These include: ground vibrations, increased airflow and changes in ambient lighting. Each experiment is repeated five times to allow for random error of the testing process. DIC has been shown to be a powerful tool in identifying the strain perturbation associated with the presence of defects. Initial results indicate that environment conditions have the potential to lead to perturbation of results, but that these may be identified and minimised and/or corrected if care is taken.
A strength of Digital Image Correlation (DIC) is the potential manoeuvrability of the system, so long as the material can be loaded in some way for analysis . This produces an interesting problem regarding how to deform a component in the field rather than in the controlled lab environment. Parallel to this limitation, there is an issue of a dependency on user capabilities with both the setup of the test and coupon preparation. This investigation analysed the possibility of using a pre-speckled bag to encase and load multiple components of complex geometries, via the evacuation of internal air. Each coupon within the bag was either originally white in colour, or spray painted with a matt white acrylic paint. The reason for this was to increase contrast between the component and the black speckles upon the bag. Results suggested that using the speckled bag, the algorithm was confident of strain mapping accurately for subsets larger than 31 pixels and could plot strain profiles for geometrically complex objects.
Grey cast iron water pipe networks have been installed around the world, often 100–180 years ago. Cohorts (which can be defined by age, size, casting technology and geographical location, to specify but a few groups) degrade at different rates due to environmental and in-service issues, which can lead to a significant loss in mechanical performance. Hence, the management of these assets can be extremely problematic in terms of identifying priorities. The current paper considers the causes of such degradation, the consequences for defining accurate and up-to-date condition assessment protocols and hence the type and urgency of rehabilitation strategies. It follows that understanding the integrity/life expectancy of water networks requires non-destructive evaluation (NDE) of large-diameter cast iron trunk mains, with particular reference to the kinds of defects that are likely to be present and the issues that make assessment difficult. From this, recommendations are outlined for asset managers required to specify NDE protocols, based on an understanding of the nature of the material and conditions in the field.
2,2-Bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane (BA-a) is blended with a commercial core shell rubber (CSR), Genioperl P52, based on a siloxane core and an acrylic shell, at a range of loadings (1–32 wt.%). Scanning electron microscopy and energy-dispersive X-ray analysis reveals an even distribution with good cohesion between the resin and CSR particles. Measurements carried out by dynamic mechanical analysis and thermogravimetric analysis show modest improvements in glass transition temperature (6 °C) and significant enhancement of thermal stability (20%) when CSR (32 wt.%) was incorporated. Such improvements are linearly related to CSR content. Moderate reductions in modulus (30%) were observed with the highest (32 wt.%) loadings of CSR and were also linearly proportional to CSR content. Thermal analysis demonstrated a small inhibitory effect, with activation energy raised by 4% with the blend containing 32 wt.% CSR and 3% in the blend containing 8 wt.% CSR. It was found that mechanical stirring of the CSR particles into the molten BA-a monomer was the most practical solution for dispersion and effectively broke down CSR agglomerates in the bulk and produced void free samples upon curing, although some minor defects were apparent with higher loadings of core shell rubber. Four batches of dog bone specimens (containing 0, 8, 16 and 32 wt.% CSR) were manufactured and underwent tensile testing. An average increase in extension was observed from 0.82 mm for the pristine poly(BA-a), to 1.14 mm (32 wt.% CSR) was achieved. The introduction of CSR has a deleterious impact on tensile strength (24.67 MPa, pristine poly(BA-a) compared with 20.48 MPa containing 32 wt.% CSR; Young's modulus of 5.4 GPa for pristine poly(BA-a) compared with 3.1 GPa containing 32 wt.% CSR). Following tensile tests, scanning electron microscopy reveals rubber cavitation as the principal toughening mechanism.
New concepts of surface modifications aimed at the enhancement of alkali resistance of basalt fibresrequire research work on chemical composition of interacting surface layers as well as knowledge aboutfundamental processes of basaltic glass dissolution. Therefore, two model basalt fibres manufactured outof subalkaline and alkaline rock material were leached in NaOH solution at a temperature of 80◦C for upto 11 days. The formation of a corrosion shell was observed in both cases and was analyzed by SEM/EDX.The model fibres out of subalkaline rocks show dissolution kinetic, which is two-staged, whereas themore alkaline fibre reflects a linear one. The complex composition of basalt fibre is detected by EDX andXPS. The surface of basalt fibres is rich in Si and Al. XPS high resolution spectra provide information onoxidation state of iron.
Timber is a composite material ordered over many length scales. The basic building blocks of timber are wood fibres, hollow tube like elements which are responsible for both water transport and load bearing within trees, (Ansell, 2015). The fibres can be separated from bulk timber in a process known as defibrilation, a key industrial process for the production of Medium Density Fibreboard (MDF). MDF is a composite material formed of fibres and adhesive, which is used widely in the construction industry among innumerable others.
Wood fibers are of the order of a few millimeters in length and a hundred micrometers in width, which makes it difficult to mechanically characterize them using standard methods, such as tensile testing. This work, builds on the development of a novel method to evaluate the stiffness of wood fibers, which uses the cantilever of an atomic force microscope (AFM) to carry out three-point bending. This is done by placing the fibers across a two millimeter trench, whereupon the AFM engages to the center and both applies loads and records the resulting displacements. Testing using this method has been confined to a single species of wood, pinus sylvestris (Scots pine), but there is a significant spread in the modulus of the fibres tested. This is not entirely surprising as a sample of wood consists of several different types of fibre, including, for example, heartwood and sapwood, early wood and latewood. These different fibres vary slightly in size and wall thickness. Here, Weibull statistics is used to investigate the correlation between samples in a dataset, and describe the magnitude of the correlation, in order to distinguish between fibre types and to provide greater clarity of the modulus associated with different types of fibre.
The current work examines using the natural features of wood to form a ‘speckle pattern’ for Digital Image Correlation (DIC) techniques, rather than using a spray applied paint. The work further investigates the impact of applying a spray painted speckle pattern and the impact on both the timber under investigation and the corresponding results.
Timber is one of the oldest building materials used by mankind, and its environmental and sustainable credentials are certainly more persuasive than those of concrete or brick. One only has to survey the historic building stock in the UK to see that, with good design, timber framed structures can last for many hundreds of years. However, when degradation sets in, the majority of the existing historic UK timber framed buildings receive repairs that are either resin assisted, screwed, or bolted. This is frequently required at beam ends, where the timber has traditionally been interfacing with a moisture absorbent and retaining material, such as brick, which focuses and exacerbates degradation processes.
The fitness of ageing cast iron pipe is a problem for both clean water and wastewater networks. Whilst considerable effort has been put into understanding the condition of cast iron mains that carry potable water, wastewater systems have received less attention. Compared with clean water mains, wastewater trunk sewers typically have thinner walls, are often of lesser casting quality, and typically are exposed to a harsher and more complex internal and external environment. It has been established that corrosion is a leading cause of deterioration in cast iron mains. Research has shown that when predicting residual load capacity in clean water main, a loss-of-section approach is not applicable when dealing with corrosion pitting, which is more discrete and notch-like. This research examines the use of both loss-of-section and fracture mechanics models to provide a failure envelope for a ring from a pipe under combined vertical loading and internal pressure. Internal corrosion, defect size, and morphology of this corrosion have a significant effect on the residual strength of the pipe. The failure envelope predicted is rather different to that previously reported for clean water mains, which is not unexpected given the differences in component geometry and operational conditions.
Cements, which are intrinsically brittle materials, can exhibit a degree of pseudo-ductility when reinforced with a sufficient volume fraction of a fibrous phase. This class of materials, called Engineered Cement Composites (ECC) has the potential to be used in future tunneling applications where a level of pseudo-ductility is required to avoid brittle failures. However uncertainties remain regarding mechanical performance. Previous work has focused on comparatively thin specimens; however for future civil engineering applications, it is imperative that the behavior in tension of thicker specimens is understood. In the present work, specimens containing cement powder and admixtures have been manufactured following two different processes and tested in tension. Multiple matrix cracking has been observed during tensile testing, leading to a “strain-hardening” behavior, confirming the possible suitability of ECC material when used as thick sections (greater than 50 mm) in tunneling applications.
Worldwide, a significant proportion of the large diameter (trunk) mains within water networks are still made of aging cast iron material. With corrosion seeming to be the most significant cause of deterioration in cast iron trunk mains, the traditional structural view of the residual strength of the pipe has been based on the strength of the remaining wall thickness, i.e. a loss-of-section approach. In some situations this may lead to an over-estimate of the residual strength and better predictions can be made using an approach based on fracture mechanics. The present research has shown how loss-of-section models of residual strength can be used alongside fracture mechanics models in a twin approach to provide boundaries to the failure envelope for a “ring element” subjected to combined bending and direct (tensile or compressive) forces. When the application of such a failure envelope to a ring from a pipe under combined vertical loading and internal pressure is considered, it was found that in addition to its size, the angular position of a corrosion defect can have a significant effect on the residual strength of the pipe.
The aim of this study is to investigate the processability of silica-thermoset polymer matrix nanocomposites in terms of dispersion of silica nanoparticles and their effect on curing. Two thermosetting resins were considered, an epoxy and a polyester resin, with 5 % silica, although 1% silica was also used in preliminary studies in the polyester system. Various combinations of mechanical mixing and sonication were investigated for the dispersion of silica nanoparticles under different processing conditions and times in solvent-free and solvent-containing systems. It was found that the best dispersion route involved a solvent-aided dispersion technique. Consequently, different procedures for the solvent removal were investigated. Optical microscopy and SEM were used to characterize the resulting nanocomposites. DSC and rheological DMTA tests demonstrated that the silica nanoparticles shorten the gel time and promote curing in these thermosetting systems.
During the quasi-static indentation of thin composite panels, well-defined flaps (sometimes called ‘‘petals’’) can develop on the exit face as a consequence of through-thickness penetration of the panel; such flaps can also be seen in impact tests. The flaps develop as four triangles, with the apex of each triangle at the point of impact. In this work, thin panels of CFRP with a 0/90 configuration have been subjected to quasi-static indentation tests and the development of the flaps has been monitored. The results show that the dependence of the flap compliance is proportional to the square of the flap length, which is in agreement with theoretical predictions. The determination of the compliance/crack-length relationship enables a toughness value for fracture of the composite panel to be derived that is directly relevant to through-thickness penetration of the panel.
Waste is a complex societal problem: municipal solid waste (MSW) should be considered a resource, but the methods for capturing, treating, and utilising this resource are varied and often dependent on geopolitical factors. Previous research has, on the one hand explored the need for a more comprehensive waste composition specification in order to better manage municipal waste, and on the other focused on a problematic waste stream and the options available for dealing with it. The current work considers the use of multi-criteria decision making in order to assess the relative merits of different treatment options. A complex and problematic waste stream, wood, has been selected as a case study. For the purpose of the study, the work considers the options available to Surrey County Council in the UK. At the present time, for the conditions selected, energy from waste was considered to be the best option available for the treatment of wood with no discernible value for upcycling or reuse, but not contaminated with hazardous chemicals. When considering a different location with different circumstances, a different solution might be found.