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.
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.
Boughanem S, Jesson DA, Mulheron MJ, Smith PA, Eddie C, Psomas S, Rimes M Engineered Cement Composite Materials: Characterization for Tunneling Applications,
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.
Fahimi A, Jesson DA, Mulheron MJ, Smith PA, Evans TS, Clay-Michael N, Farrow J (2014) Managing water infrastructure: Corrosion models for cast iron trunk mains, WIT Transactions on the Built Environment 139 pp. 401-409
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.
Jesson DA, Mohebbi H, Farrow J, Mulheron MJ, Smith PA (2013) On the condition assessment of cast iron trunk main: The effect of microstructure and in-service graphitisation on mechanical properties in flexure, Materials Science and Engineering A 576 pp. 192-201
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. © 2013 Elsevier B.V.
Mohebbi H, Jesson DA, Mulheron MJ, Smith PA (2009) Characterisation of the fatigue properties of cast irons used in the water industry and the effect on pipe strength and performance,
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.
Cox J-A, Jesson DA, Mulheron MJ, Druckman A, Smyth M, Trew H (2015) Municipal Solid Waste as a Resource Pt 1: A case study in specifying composition, Waste and Resource Management
Waste is a complex societal problem that brings together various stakeholders in order
to manage it. However, a lack of sufficient information on the quantities and types of
material in the waste stream can make sustainable waste management difficult. Since
waste in one sector can be valuable as a resource in another, there is a need to
understand the distribution of materials within the resource stream, especially those
that go to landfill. Current work is seeking to address this; whilst much material is
already recycled, this is not the only management option and there remain several
problematic materials/components to be removed from residual waste. This paper, the
first of two case studies, presents a more comprehensive waste composition
specification in order to better manage municipal waste. In developing this approach,
waste composition specifications currently in use have been reviewed and compared
with the solid municipal (household) waste collected at community recycling centres
and from the kerbside. Key primary and secondary descriptors for the better
management of resources arising from municipal waste have been determined, and
the impact of these changes on the information arising from composition analysis is
Organic-inorganic hybrid nanoparticles, derived from silica precursors with different organic functionalities (methyl, ethyl, vinyl, and phenyl) synthesized via a modified Stöber method have been investigated. These particles are intended as modifiers for polymers and polymer matrix composites. Therefore, the characteristics of a polyester matrix have also been determined, and the likely interactions with the particles have been proposed. Particles have been characterized using inverse gas chromatography (IGC), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy (FT-IR). The particles show two different sets of characteristics, with methyl, ethyl, and vinyl modified silicas snowing one type of behavior and the phenyl modified silica behaving rather differently. The methyl, ethyl, and vinyl groups exhibit the appearance of uniform coverage, as they are comparatively small and tightly packed, which will prevent interaction of matrix resin with retained silanol groups. The phenyl group, which is comparatively large, is not able to pack as closely, which results in a reduction of the presence and availability of silanol groups, compared to an unmodified fumed silica, but not complete inaccessibility as far as the matrix resin is concerned. © 2006 American Chemical Society.
Chard JM, Creech G, Jesson DA, Smith PA (2012) COUPLING AGENT FOR NATURAL FIBRE COMPOSITES UTILISING THERMOSETTING RESIN 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.
Cox J-A, Druckman A, Jesson DA, Mulheron M, Smyth M, Trew H (2015) MSW as a Resource Pt 2: A case study in sustainable management, Proceedings of the Institution of Civil Engineers: Waste and Resource Management
WX Weight of material to be managed by a particular option
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.
Boughanem S, Jesson DA, Mulheron MJ, Smith PA, Eddie C, Psomas S, Rimes M (2014) Tensile characterisation of thick sections of Engineered Cement Composite (ECC) materials, Journal of Materials Science 50 (2) pp. 882-897 Springer
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.
Chard JM, Creech G, Jesson DA, Smith PA (2011) Green Composites: Sustainability and Mechanical Performance,
Jesson DA, Mohebbi H, Belmonte HMS, Mulheron MJ, Smith PA (2007) Derivation of Uniaxial Stress-Strain curves for Cast iron from Samples tested in flexure,
Förster T, Scheffler C, Mäder E, Heinrich G, Jesson DA, Watts JF (2014) Dissolution behaviour of model basalt fibres studied by surfaceanalysis methods, Applied Surface Science 322 pp. 78-84 Elsevier
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 80æC 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.
Jesson DA, Mohebbi H, Belmonte HMS, Mulheron MJ, Smith PA (2007) Comparison of Post-Service Cast Iron Pipes: Linking Properties With Microstructure,
Logan R, Mulheron MJ, Jesson DA, Smith PA, Evans TS, Clay-Michael N, Whiter JT (2014) Graphitic corrosion of cast iron trunk main: implications for asset management,
Failures of (large diameter) cast iron trunk water mains can be catastrophic in the damage they can cause and it is therefore imperative to understand how cast iron deteriorates in order to help predict those areas of a water supply network which are at greatest risk of failure. Cast irons undergo a localized form of corrosion known as graphitic corrosion. Although a well reported phenomena, the mechanisms of graphitic corrosion are not fully understood. Scanning electron microscopy, in conjunction with energy dispersive x-ray spectroscopy, was used to characterise the microstructure and chemistry of the graphitic corrosion that occurs on the external surface of the pipe during time in service. It was found that that the graphite flakes within the cast iron are deteriorating during the corrosion process. High levels of chlorides are often found at the corrosion interface, within graphitic pits in the pipe wall. The implications of these observations on the development of models used to predict the remaining service life of buried trunk main are discussed.
Jesson DA The Interaction of Nano-Composite Particles with a Polyester Resin and the Effect on Mechanical Properties,
The effect of various organically modified silica (ormosil) nano-particle additions on the
mechanical properties of a polyester resin has been investigated. For materials produced
on such a fine scale, surface properties are known to dominate the manner in which they
This thesis presents results from two complementary areas of study: surface analysis and
mechanical testing. The surface properties of the nano-particles and the interactions of
the nano-particles with a polyester and adsorbed water have been investigated. These
analyses have led to the development of a model which shows that the small organic
groups grafted to the silica surface (methyl, ethyl and vinyl) are able to pack
comparatively densely at the surface, effectively forming a continuous monolayer. This
layer is sufficiently thick to prevent interaction of retained silanol groups with the
polyester resin. When the silica is modified with phenyl functionality, however, the
larger size leads to a more dispersed organic coverage that cannot be considered as a
complete monolayer. Hence this layer reduces, but will not completely prevent interaction
of the matrix with retained silanols of the silica.
The particles have been dispersed in a polyester resin successfully. The dispersion
process is an important step in producing viable nano-composites. Mechanical testing of
such nano-composites has found a significant improvement in the toughness properties of
the phenyl ormosil modified polyester, compared with the unmodified resin, whilst the
other modified polyesters show smaller improvements. When considered with the surface
analysis investigation, it is argued that the improvement is a result of a reduction of the
strength of the interface (with reference to a commercial nano-silica) between the
particles and the matrix. The phenyl ormosil is more strongly bonded than the other
ormosils. Whilst these other ormosils are able to contribute to toughness through a crack
pinning mechanism, the phenyl ormosil absorbs energy through debonding and promotes
plastic deformation in the matrix, around and between particles, mechanisms which lead
to a greater toughness enhancement.
Fishpool DT, Guidon E, Maedza BH, Maso J, Ogin S, Thorne AM, Le Page BH, Jesson DA (2008) Fatigue failure of a composite sandwich beam containing a central notch,
Jesson DA, Watts JF (2012) The Interface and Interphase in Polymer Matrix Composites: Effect on Mechanical Properties and Methods for Identification, Polymer Reviews 52 (3-4) pp. 321-354 Taylor & Francis
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.
Chard J, Creech G, Jesson DA, Smith PA (2015) Viscose Rayon Fibres: A Potential Addition to the Technical Fibres Family?,
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.
Logan R, Mulheron MJ, Jesson D, Smith PA, Evans T, Clay-Michael N, Whiter J (2014) Observations on the graphitic corrosion of cast iron trunk main: Mechanisms and Implications,
Failures of large diameter cast iron trunk water mains can be catastrophic in the damage they can cause. It is therefore imperative to understand how cast iron deteriorates in order to help predict those areas of a water supply network which are at greatest risk of failure. Cast irons undergo a localized form of corrosion known as graphitic corrosion. The current work focusses on graphitic corrosion occurring on the external surface of a pipe a forming pits or larger patches of corrosion into the wall of the pipe. It was found that the graphite flakes within the cast iron are deteriorating during the corrosion process. High levels of chlorides are often found at the corrosion interface, within graphitic pits in the pipe wall. Electrochemical Impedance Spectroscopy shows that the corrosion mechanism of cast iron in soils changes when the salinity of the soil rises, which has significant implications for asset management and the mitigation of corrosion.
Keywords: graphitic corrosion, cast iron, water distribution, EIS, chlorides.
Chard JM, Basson L, Creech G, Jesson DA, Smith PA (2013) Shades of Green: Preliminary LCA of Biobased Polymer Resins For Composite Materials,
Sirichantra J, Ogin SL, Sofocleous K, Jesson DA, Marom G, Galpaz N (2009) Controlled impact tests on wovenfabric/ epoxy resin CFRP panels with and without additional carbon nanotube reinforcement, 17th International Conference on Composite Materials
Förster T, Mäder E, Jesson DA, Watts JF (2013) Surface Analyses of Basalt Fibres: Tailoring the Interphase of ?Green? Fibre Reinforced Composites,
Ogin SL, Vadlamani S, Kakaratsios Z, Jesson DA, Kaddour AS, Smith PA, Sirichantra J, Bogdanovich AE (2011) Damage development in a glass/epoxy non-crimp 3d orthogonal woven fabric composite,
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.
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?.
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.
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.
Every day, water networks across the developed world are relied on by billions of people to provide them with
a fresh supply of water. Many of these networks are comprised of pipes made from grey cast iron and may
have been in service for up to 150 years. Despite their age, some parts of these networks continue to operate
with little degradation, whereas in other areas they degrade rapidly: more recently laid pipes are being outlived by their forerunners. In such networks, it is the trunk mains (pipes between 12-60? [300 mm to 1500 mm] in diameter) that are of great concern, since they pose the greatest risk of failure and are already bursting more frequently.
Accurate NDE is required to enable the mains in poor health with the highest risk of failure to be identified
and replaced before they burst. A review of the published literature has shown that whilst there are many NDE
techniques to choose from, many are not practical for application to the mains. The review process also
highlighted the kinds of defects present in grey cast iron and an initial stress analysis using strength models
and material data published in the literature has suggested defect sizes approaching 5 mm must be able to be detected to prevent catastrophic pipe failure.
Ultrasonic inspection has been investigated and shown to work effectively on uncorroded cast iron. Speed of
sound values between 4100 ? 4600 m s-1 have been observed across several pipes. A speed of sound of 2950 ± 80 m s-1 has been measured for graphitic corrosion, however, inspection on corroded main has not been possible.
A complementary magnetic technique, with the potential to scan pipe rapidly in order to identify mains in need
of further investigation, as well as providing supplementary condition data, has been trialled and shown to detect corrosion layers up to 6 mm thick.
A methodology using a 3D scanner to accurately determine the ?ground truth? pipe condition has been developed. This methodology proved to be successful and provided corrosion measurements that were in-keeping with those obtained through standard pit depth measurements. Further, the data showed that traditional pit depth measurements do not always find the deepest external corrosion pits, particularly where the surrounding geometry is complicated.
This methodology was used in a live comparison exercise of two, commercially available techniques. This
comparison highlighted problems with the surface preparation required by some techniques, which can be
quite damaging, and with some proprietary post-processing algorithms ? the raw data can be more useful.
From this assessment process, it has been possible to specify very detailed schedule for the testing of new NDE
techniques in the future.
Sustainability requires urgent, radical innovation from the private sector. However, private sector-led sustainability which meaningfully advances social, environmental and economic goals remains a rare occurrence. Despite the potential role of balanced environmental strategies such as ecological modernisation, there remains a lack of understanding of how such theories can be translated to actions at the level of a single organisation.
This thesis explores the topics of ecological modernisation, employee engagement and sustainability-oriented innovation, grounded by a case study of Interface, a global manufacturing company. The work helps to build an understanding of the practicalities of organisation-level ecological modernisation, corporate sustainability and innovation in practice. It makes use of a case study research strategy combined with a grounded theory methodological approach. Three themes; ecological modernisation, employee engagement and sustainability-oriented innovation, are discussed and are applied to the analysis of the case material.
The following key findings emerge:
" Ecological modernisation, a theory typically applied and discussed at the macro-sociological level, is explored at the level of a single organisation, where it is used to contextualise the actions of Interface which contribute to wider, system-level sustainable disruptions. This is found to be a useful unit of analysis compared with typical explorations of EM, and reveals a number of interesting pathways by which EM organisations might impact upon the wider system in which they operate;
" Social dimensions of EM theory are discussed and explored. By considering Interface at the centre of a larger, interconnected network of actors, it is found that there are numerous dynamics at play, including the role of employees and their levels of engagement, the role of competitors and the wider industry, the role of customers and the role of suppliers;
" Temporal dimensions of EM are revealed and discussed, and several barriers are shown to emerge for Interface as it progresses further into a 20-year journey towards sustainability. Most strikingly, the low-hanging fruit is no longer available, and Interface finds itself in the ?tall canopy? in seeking further reductions in emissions and waste;
" Net-Works, a radical, innovative recycling project is presented and compared with other, less successful innovations from Interface. The contextual factors that gave rise to Net-Works are a combination of a radical goal, deliberate adoption of a social goal, and a safe failure space. Success is owed to developed capabilities, incorporation into an existing product, and partnering with an NGO and academia for accountability and credibility.
Adhesive bonding for structural applications has many advantages such as reducing the weight of vehicles and providing efficient stress transfer across joined materials. The largest asset of adhesive bonding is that they can join dissimilar materials. To achieve the highest joint strength possible when using metals, however, the metal surfaces have to be pre-treated. This can be done in a variety of ways, such as grit blasting or chemical etching. Chemically etching the surface produces the highest strength joints, but has many drawbacks. The first of which is that each metal used requires a different treatment chemistry. This reduces the materials available for selection as a result of increased pre-treatment complexity.
The current work focusses on stainless steel and titanium alloy. The lap shear bond strength for both metals increased significantly after a cold atmospheric plasma (CAP) treatment and was in line with the chemical etching processes. The durability of both metals demonstrated that the plasma treatment increases the performance. For stainless steel the durability is similar to the chemical etch process. For titanium the durability performance is increased, but does not reach the level of the chemical treatment process.
A combination of surface science techniques has revealed that there are three mechanisms which lead to an increased bond strength. These are: a reduction in hydrocarbon contamination, shown using X-ray photoelectron spectroscopy (XPS) and time of flight\,-\,secondary ion mass spectrometry (ToF-SIMS). The growth of the surface oxide layer, analysed using an XPS sputter depth profile, and functionalisation of the oxide layer, which has been probed using ToF-SIMS, both lead to an increase in lap shear bond strength.
The feasibility of the process rests on two factors. The first is achieving equivalent mechanical properties, the second factor is the energy, resources and time required for a given treatment. The first has been satisfied in this work, the second has been investigated using a life cycle analysis approach which found that plasma treatment had a higher impact on the environment when compared to oxalic acid etching. but this assumed that the acid is 100\% efficient, which is far from the case. When simulated in a `real world' scenario, there is nearly parity between the two treatments
Based on the data presented in this work, including analysis of the process life cycle, CAP has the potential as a first multi material pre-treatment for structural adhesive bonding.
Polymeric methyl diphenyl diisocyanate (pMDI) is a versatile isocyanate-based
adhesive commonly used in the manufacturing process of composite wood panels. Its
use has constantly been increasing over the past years driven by the great performance
that this resin offers in terms of moisture resistance, durability and strength. However,
the use of isocyanate-based adhesives carry some challenges related to the composite
wood production which need to be improved. In particular, the adhesion of these resins
to the stainless steel press platens during the production process. The strong adhesion
between the glue and the press platens results in production issues forcing the
production to stop. There are a number of methodologies to overcome the production
issues, however, all of them incur additional costs or have associated health and safety
issues. Therefore, this study aims to expand the understanding of the interfacial
chemistry and processes occurring at the press platen/pMDI-wood interface to help to
develop approaches to achieve release of isocyanate-based adhesives.
In order to achieve the aim of this project, surface analysis techniques, in particular Xray
photoelectron spectroscopy (XPS) and time of flight secondary ion mass
spectrometry (ToF-SIMS), were used. In the first stage of this project, the surface characterisation of pine wood and its extractives, pMDI and the stainless steel used for
the manufacture of composite wood panels was carried out. Then, the study of the
pMDI/metal interface was performed obtaining important information related to the
bonding of pMDI to steel. The interface between the stainless steel/pMDI-wood
system was also investigated. The results of this study showed that the pine wood
extractives compounds have a significant impact in the adhesion of wood to stainless
steel. These findings allowed us to inform strategies which could lead to the release of
isocyanate-based adhesives from the steel during the composite wood panel
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.
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.
The range of applications for composite materials is growing, but understanding of the effect of defects is limited, as is the ability to detect them. Versatile non-destructive testing (NDT) techniques, that can be deployed rapidly and reliably, to detect and monitor damage in composite components are vital to the continued growth of this sector.
This research investigates the application of Digital Image Correlation (DIC) as an NDT technique for monitoring delamination defects in Fibre Reinforced Polymer (FRP) composites. The research has matched physical experiments with Finite Element (FE) modelling. Four types of glass-fibre reinforced epoxy matrix composite structural elements were designed and manufactured to assess this application of DIC. The first two types of structural elements were flat coupons containing fully embedded delaminations, artificially introduced using two different methods. It was found that by placing these specimens in three-point bending, near surface delaminations, one ply below the surface being monitored, would cause a plateau in the surface strains. This plateau in strains was used to measure the embedded defect sizes. The size of the delamination was consistently overestimated from the interpretation of the strain fields. This was improved with the assistance of FE modelling to identify the relationship between the feature and the delamination. Pulse thermography was found to be a better technique for measuring the size of these defects.
The third type of specimen was a flat coupon containing a milled-slot, which was fatigued to grow a delamination at the foot of the milled slot, and the delamination measured visually. For this specimen, the DIC results showed good correlation with the visually determined delamination lengths with an empirical fit applied to the strain results. Both lock-in thermography and pulse thermography were used to measure the delamination size of the same specimens and showed reasonable correlation with the visually determined delamination lengths.
Finally, tubular specimens containing embedded PTFE delamination-defects were fatigued at different ratios of tension and torsion. DIC of the specimens loaded at the fatigue load ratio at which the delaminations were grown could not be used to quantify the size of the delaminations.
The work has shown that DIC can be used to monitor delaminations in some structural elements, however the type of loading needs to be considered to ensure sufficient influence on the surface strains to enable strain features that can be used to measure the size of delamination
Large diameter trunk mains are the life line of the water supply system. They convey large volumes of water between treatment works and local distribution networks, sometimes over quite significant distances (tens to hundreds of kilometres). Compared to smaller diameter distribution mains, trunk mains tend to have low failure rates, but when they do fail, the consequences are potentially much more significant, with direct, indirect and societal costs.
Worldwide, a significant proportion of trunk mains are still made of aging cast iron material. Remarkably, these aging assets have in some cases outlived the pipes that replaced deteriorated parts of the network. Even so, many cast iron pipes are beginning to approach, or have already exceeded, their design life: consequently, out of a large population of pipes, some are failing whilst some still have considerable residual life.
Asset management, in this context focussing on the targeted replacement of degrading main, requires tools and models for the prediction of the future performance of the network. Several mechanistic deterioration models have been developed in recent years, which attempt to predict the condition of cast iron pipes, but few methodologies have specifically targeted water trunk mains. Nevertheless, the requirement has remained for a robust deterioration and failure model for cast iron trunk mains, worldwide.
This project, being part of a wider, collaborative project between Thames Water Utilities and the University of Surrey, has reviewed existing failure models for cast iron trunk mains and sought to modify these based on information arising from other areas of the project. This has included, new understanding of the corrosion of cast iron trunk main, the use of fracture mechanics to predict failure and non-destructive evaluation data gathering techniques has provided significant insight into improvements that can be made to failure models.
In particular, the present research has shown how traditional loss-of-section approach to the residual strength of corroded pipes can be used alongside a fracture mechanics approach, in order to provide boundaries to the failure ?envelope?. This novel methodology has been incorporated as part of an enhanced modelling framework, which has shown to improve the failure predictions across the network. The enhanced model also enables more detailed analysis of sections of the pipes that have been surveyed on site.
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.
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.
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.
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.
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.
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.