The possibility of a third phase, often referred to as the interphase, in polymer composites is well known, and there have been many attempts to characterise the mechanical properties of this region at the nanoscale. Despite the increasing resolution of nano-indentation and atomic force microscopy techniques, it is not always possible to identify thin interphases when the dimensions are similar to those of the indenter-surface contact area. The use of indentation for mechanical characterisation continues to be explored for multi-phase systems, and there is a need for a method to evaluate quickly whether a given indentation is influenced by neighbouring material phases. The results presented in this paper demonstrate, both experimentally and through finite element analysis, a method of quickly identifying indentations that are restricted by the reinforcement. © 2013 Elsevier Ltd. All rights reserved.
Kastritseas C, Smith PA, Yeomans JA (2005) Thermal shock fracture in unidirectional fibre-reinforced ceramic-matrix composites, COMPOSITES SCIENCE AND TECHNOLOGY 65 (11-12) pp. 1880-1890 ELSEVIER SCI LTD
Hamerton I, McNamara LT, Howlin BJ, Smith PA, Cross P, Ward S (2014) Developing toughened aromatic polybenzoxazines using thermoplastic oligomers and telechelics, part 1: Preparation and characterization of the functionalized oligomers, Journal of Applied Polymer Science 131 (19)
The preparation and characterization of three families of thermoplastic oligomers (Mn0=02918-13263 g mol-1) based on polyarylsulfone (PSU) differing in both molecular weight and terminal functionality and one series of polyarylethersulfone (PES) of different molecular weights is reported. Infrared and nuclear magnetic resonance spectroscopy data support the formation of both the hydroxyl terminated oligomers and conversion (67-89% depending on molecular weight) to the telechelic PSU oligomer bearing reactive benzoxazine groups. Differential scanning calorimetry reveals that the onset of homopolymerization in the telechelic PSU oligomer occurs at around 100°C (peak maximum 125°C at 10 K/min) and rescans show values of the glass transition (for the homopolymers) ranging from 124 to 167°C depending on molecular weight. The influence on the oligomer backbone and terminal functionality is examined using thermal analysis. © 2014 Wiley Periodicals, Inc.
Boughanem S, Jesson DA, Smith PA, Mulheron MJ, Eddie C, Psomas S, Rimes M (2011) Engineered cement composites properties for civil engineering applications, ICCM International Conferences on Composite Materials
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 "strain-hardening" 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.
Kastritseas C, Smith PA, Yeomans JA (2005) The onset of thermal shock damage in unidirectional-fibre-reinforced ceramic matrix composites, HIGH TEMPERATURE CERAMIC MATRIX COMPOSITES 5 pp. 235-240 AMER CERAMIC SOC
Guild FJ, Balhi N, Vrellos N, Ogin SL, Smith PA (2007) Matrix cracking in CFRP laminates, ICCM International Conferences on Composite Materials
Matrix ply cracking is the most common damage to form when a laminate is loaded, and is of considerable significance for the integrity of a composite structure. The overall aim of the present work is to provide validated constitutive relations for crack accumulation in off-axis plies under mixed mode loading. The results presented in this paper include experimental investigations to describe the development of the cracking and the development of finite element-based models of cracked laminates. The effect of matrix cracking on the residual stiffness of various laminates is determined both experimentally and using finite element simulation. The ratio of modes in different angle ply laminates and the associated criteria for matrix crack initiation are explored.
The present paper is concerned with modelling damage and fracture in notched woven fabric composites. Previous experimental work has shown that damage at a notch in a variety of GFRP and CFRP composites based on woven fabric reinforcement comprises matrix damage and fibre tow fracture along the plane of maximum stress. It is these experimental observations that inform the failure modelling developed here, in which a cohesive zone approach is used within a 2- D finite element framework. The cohesive zone parameters are based on previously reported experimental measurements for the strength and toughness of the woven fabric materials under investigation. The approach is shown to provide predictions of notched strength that are in very good agreement (less than 11% discrepancy) with experimental results from the literature for a range of GFRP and CFRP woven fabric systems. © (2014) Trans Tech Publications, Switzerland.
Kaddour AS, Hinton MJ, Smith PA, Li S (2013) A comparison between the predictive capability of matrix cracking, damage and failure criteria for fibre reinforced composite laminates: Part A of the third world-wide failure exercise, Journal of Composite Materials 47 (20-21) pp. 2749-2779
This paper provides a set of concluding remarks on Part A of the third world-wide failure exercise where a comparison has been made between the capabilities of 12 different mathematical models for predicting the evolution of matrix cracking, damage and failure in continuous fibre-reinforced polymer composites when subjected to multi-axial loading. The originators (or their collaborators) of those theories have employed their methods to 13 carefully selected challenging problems (test cases) addressing the cracking and damage evolution arising from ply thickness, lay-up sequence, size effects and a variety of loading conditions (biaxial, bending, thermal loading and loading-unloading) of a number of unidirectional and multi-directional glass and carbon epoxy laminates. These covered eight different lay-ups consisting of 0 , [0 /90 /0 ], [0 /90 8/0 ], [0 /90 ]s, [±45 ]s, [±50 ]s, [30 /90 /-30 /90 ]s and a family of [0 m/45 m/90 m/-45 m]s, [45 /0 /90 /-45 ]s and [0 /45 /-45 /90 ]s quasi-isotropic laminates. Key features in each theory are identified including: types of damage models employed, whether linear or nonlinear analysis was carried out, reliance on software and numerical methods and identification of modes of damage. The results of stress-strain curves, crack density and damage curves have been superimposed and bar charts were constructed to show similarities and differences between the predictions of the various theories. © The Author(s) 2013.
Belmonte HMS, Manger CIC, Ogin SL, Smith PA, Lewin R (2001) Characterisation and modelling of the notched tensile fracture of woven quasi-isotropic GFRP laminates, COMPOSITES SCIENCE AND TECHNOLOGY 61 (4) pp. 585-597 ELSEVIER SCI LTD
Chard JM, Creech G, Jesson DA, Smith PA (2011) Green Composites: Sustainability and Mechanical Performance,
HITCHEN SA, OGIN SL, SMITH PA, SOUTIS C (1994) THE EFFECT OF FIBER LENGTH ON FRACTURE-TOUGHNESS AND NOTCHED STRENGTH OF SHORT CARBON-FIBER EPOXY COMPOSITES, COMPOSITES 25 (6) pp. 407-413 BUTTERWORTH-HEINEMANN LTD
This paper details a quality control test for polymeric composite interfaces independent of reinforcement type and geometry. Experimentation has shown the capability of AFM indentation in characterising interfacial mechanical property variation with focus on measurement quantification to produce elastic modulus maps at the micro- and nano-scale
SPEARING SM, BEAUMONT PWR, SMITH PA (1992) FATIGUE DAMAGE MECHANICS OF COMPOSITE-MATERIALS .4. PREDICTION OF POST-FATIGUE STIFFNESS, COMPOSITES SCIENCE AND TECHNOLOGY 44 (4) pp. 309-317 ELSEVIER SCI LTD
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.
Wood AR, Smith PA, Watts JF (2007) The interfacial properties of glass fibre/nano-modified polyester matrix composites, ICCM International Conferences on Composite Materials
The single fibre pull-out (SFPO) test has been used to investigate the interfacial interaction between a glass fibre and a polyester matrix system. However, mechanical data alone cannot explain fully the mechanisms of failure, and time-of-flight secondary-ion mass spectrometry (ToF-SIMS) has been utilised to gain insight into the interfacial chemistry of adhesion. The present work employs ToF-SIMS for the forensic examination of fibre surfaces following a SFPO test. Regions of interest have been selected for retrospective spectral analysis. Results are presented which lead to the description of a failure model based upon these complementary analytical techniques. ToF-SIMS has revealed a difference in the surface chemistry at the fibre tip compared to the bulk of the pulled out region, which correlates with stress transfer models in the literature showing higher stress states existing at the embedded fibre tip region. The application of the methodology to nano-modified polyester matrix composites is discussed.
The current paper is concerned with modelling damage and fracture in woven fabric composite double-lap bolted joints that fail by net-tension. A 3-D finite element model is used, which incorporates bolt clamp-up, to model a range of CFRP bolted joints, which were also tested experimentally. The effects of laminate lay-up, joint geometry, hole size and bolt clamp-up torque were considered. An Extended Finite Element (XFEM) approach is used to simulate damage growth, with traction-separation parameters that are based on previously reported, independent experimental measurements for the strength and toughness of the woven fabric materials under investigation. Good agreement between the predicted and measured bearing stress at failure was obtained. © 2013 Elsevier Ltd. All rights reserved.
Mulligan DR, Ogin SL, Smith PA, Wells GM, Worrall CM (2003) Fibre-bundling in a short-fibre composite: 1. Review of literature and development of a method for controlling the degree of bundling, COMPOSITES SCIENCE AND TECHNOLOGY 63 (5) PII S0266-3538(02)00259-2 pp. 715-725 ELSEVIER SCI LTD
REZAIFARD AH, BADER MG, SMITH PA (1994) INVESTIGATION OF THE TRANSVERSE PROPERTIES OF A UNIDIRECTIONAL CARBON-EPOXY LAMINATE .2. LAMINATE PROPERTIES, COMPOSITES SCIENCE AND TECHNOLOGY 52 (2) pp. 287-295 ELSEVIER SCI LTD
Chard JM, Creech G, Jesson DA, Smith PA (2012) COUPLING AGENT FOR NATURAL FIBRE COMPOSITES UTILISING THERMOSETTING RESIN SYSTEMS,
Gao F, Boniface L, Ogin SL, Smith PA, Greaves RP (1999) Damage accumulation in woven-fabric CFRP laminates under tensile loading: 2. Modelling the effect of damage on macro-mechanical properties, COMPOSITES SCIENCE AND TECHNOLOGY 59 (1) pp. 137-145 ELSEVIER SCI LTD
Watts JF, Vickers PE, Prickett AC, Smith PA (1999) Interphase chemistry of carbon fiber composites., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 218 pp. U632-U632 AMER CHEMICAL SOC
Le Page BH, Manger CIC, Guild FJ, Ogin SL, Smith PA (2002) Modelling effect of layer shift on properties of woven fabric composites, PLASTICS RUBBER AND COMPOSITES 31 (9) pp. 385-391 MANEY PUBLISHING
Kastritseas C, Smith PA, Yeomans JA (2010) Thermal shock fracture in cross-ply fibre-reinforced ceramic-matrix composites, PHILOSOPHICAL MAGAZINE 90 (31-32) PII 923938348 pp. 4209-4226 TAYLOR & FRANCIS LTD
Boniface L, Ogin SL, Smith PA (1991) Fracture mechanics approaches to transverse ply cracking in composite laminates, ASTM Special Technical Publication (1110) pp. 9-29
The growth of transverse ply cracks in composite laminates has been investigated both theoretically and experimentally. Some of the closed-form strain energy release rate based analyses of this problem in the literature have been compared and extensions to these approaches are presented. These models have been shown to be consistent with an alternative approach based on an approximate expression for the stress intensity factor at the tip of a growing transverse ply crack. An experimental study of transverse ply crack growth has been carried out using a simple model array of transverse ply cracks in a glass/epoxy laminate. By making the transverse ply sufficiently thick, the specimen compliance was found to change measurably as individual cracks grow. Hence, the strain energy release rate could be determined experimentally (via the compliance relationship) and compared with analytical predictions. Agreement was found to be satisfactory.
Wahab MMA, Ashcroft IA, Crocombe AD, Smith PA (2004) Finite element prediction of fatigue crack propagation lifetime in composite bonded joints, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 35 (2) pp. 213-222 ELSEVIER SCI LTD
PeakForceTM quantitative nanomechanical mapping (QNM TM) is a new atomic force microscopy technique for measuring Young's modulus of materials with high spatial resolution and surface sensitivity by probing at the nanoscale. In this work, modulus results from PeakForce" QNM" using three different probes are presented for a number of different polymers with a range of Young's moduli that were measured independently by instrumented (nano) indentation testing (IIT). The results from the diamond and silicon AFM probes were consistent and in reasonable agreement with IIT values for the majority of samples. It is concluded that the technique is complementary to IIT; calibration requirements and potential improvements to the technique are discussed. © 2011 IOP Publishing Ltd.
CROCOMBE AD, RICHARDSON G, SMITH PA (1995) A UNIFIED APPROACH FOR PREDICTING THE STRENGTH OF CRACKED AND NON-CRACKED ADHESIVE JOINTS, JOURNAL OF ADHESION 49 (3-4) pp. 211-244 GORDON BREACH SCI PUBL LTD
BADER MG, PICKERING KL, BUXTON A, REZAIFARD A, SMITH PA (1993) FAILURE MICROMECHANISMS IN CONTINUOUS CARBON-FIBER EPOXY-RESIN COMPOSITES, COMPOSITES SCIENCE AND TECHNOLOGY 48 (1-4) pp. 135-142 ELSEVIER SCI LTD
PRYCE AW, SMITH PA (1993) MATRIX CRACKING IN UNIDIRECTIONAL CERAMIC MATRIX COMPOSITES UNDER QUASI-STATIC AND CYCLIC LOADING, ACTA METALLURGICA ET MATERIALIA 41 (4) pp. 1269-1281 PERGAMON-ELSEVIER SCIENCE LTD
Fatigue tests have been carried out to investigate mixed mode fatigue crack growth behaviour in FM73 epoxy adhesive using double cantilever beam (DCB) specimens. The DCB configuration used consisted of equal thickness mild steel adherends bonded with FM73 adhesive. The joints were tested under pure mode I and a range of fatigue mixed-mode conditions using a relatively simple, variable-mode loading fixture developed in previous work . The fatigue testing was carried out in displacement control, with an initial load ratio (R) of 0.1. The fatigue load decreased as the fatigue crack grew and this load was recorded. Crack growth was monitored and measured using a video microscope. The results suggest that crack initiation in the test specimens is controlled by the mode I strain energy release rate, GI component. The fatigue crack growth rates were characterised using a Paris law approach, from which it appears that the total strain energy release rate range, G Total, is a more dominant factor in controlling crack growth than the mode I component of strain energy release rate range, GI. For a quantitative description of the mixed-mode fatigue crack growth, generalised forms of the Paris relation are developed. © 2012 Elsevier Ltd.
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.
Kaddour AS, Hinton MJ, Smith PA, Li S (2013) The background to the third world-wide failure exercise, Journal of Composite Materials 47 (20-21) pp. 2417-2426
The authors have recently completed two world-wide failure exercises, which dealt with benchmarking recognised failure criteria under two-dimensional and three-dimensional loadings, respectively. A new phase, called the 'third world-wide failure exercise' is currently underway to fill some of the major gaps identified in the previous activities. The third world-wide failure exercise is concerned with highlighting the degree of maturity of the current capabilities of 12 internationally recognised methods for modelling various aspects of damage in composite materials. Such problems include matrix cracks due to thermal and mechanical loads; delamination; ply constraint and stacking sequence effects; loading and unloading phenomena; failure due to stress gradients (in particular the hole size effect). The topics addressed within the third world-wide failure exercise represent an extremely important and crucial area for advanced modelling and virtual testing of composites. The third world-wide failure exercise runs in two stages (1) Part A which is devoted to providing full details and a comparison between the 12 theories together with their 'blind' predictions, made by their originators, for a challenging set of test problems and (2) Part B which is concerned with comparing the theoretical predictions with experimental results and assessing the accuracy and maturity of the methods. This paper provides details of the background to third world-wide failure exercise, the process of completing Part A and a summary of key conclusions. © The Author(s) 2013.
Boniface L, Smith PA, Bader MG, Rezaifard AH (1997) Transverse ply cracking in cross-ply CFRP laminates - Initiation or propagation controlled?, JOURNAL OF COMPOSITE MATERIALS 31 (11) pp. 1080-1112 TECHNOMIC PUBL CO INC
Kaddour AS, Hinton MJ, Smith PA, Li S (2013) Mechanical properties and details of composite laminates for the test cases used in the third world-wide failure exercise, Journal of Composite Materials 47 (20-21) pp. 2427-2442
This paper gives details of the input data and a full description of a set of 13 test cases provided to the participants of the third world-wide failure exercise for use in their theoretical models. World-wide failure exercise is aimed at benchmarking leading methods, capable of predicting initiation and progression matrix cracking and damage and failure in composites. The originators of leading theories were requested to use the exact input data provided here in their blind predictions of the test cases. The input data include all of the elastic constants, ultimate strains and strengths and the nonlinear stress-strain curves for the unidirectional laminae and their constituents. Various types of laminates, chosen for the analysis, are described together with the lay-up, layer thicknesses, stacking sequences and the loading conditions. Detailed instructions, issued to the contributors, are also presented at the end of this paper. © The Author(s) 2013.
Bond DA, Smith PA (2006) Modeling the transport of low-molecular-weight penetrants within polymer matrix composites, APPLIED MECHANICS REVIEWS 59 (1-6) pp. 249-268 ASME-AMER SOC MECHANICAL ENG
Thozhur SM, Crocombe AD, Smith PA, Cowley K, Mullier N (2006) Structural characteristics and mechanical behaviour of beard hair, JOURNAL OF MATERIALS SCIENCE 41 (4) pp. 1109-1121 SPRINGER
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.
RICHARDSON G, CROCOMBE AD, SMITH PA (1993) A COMPARISON OF 2-DIMENSIONAL AND 3-DIMENSIONAL FINITE-ELEMENT ANALYSES OF ADHESIVE JOINTS, INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES 13 (3) pp. 193-200 BUTTERWORTH-HEINEMANN LTD
Powell KL, Yeomans JA, Smith PA (1997) A study of the erosive wear behaviour of continuous fibre reinforced ceramic matrix composites, ACTA MATERIALIA 45 (1) pp. 321-330 PERGAMON-ELSEVIER SCIENCE LTD
Hamerton I, McNamara LT, Howlin BJ, Smith PA, Cross P, Ward S (2013) Examining the Initiation of the Polymerization Mechanism and Network Development in Aromatic Polybenzoxazines., Macromolecules 46 (13) pp. 5117-5132
Three bis-benzoxazine monomers based on the aniline derivatives of bisphenol A (BA-a), bisphenol F (BF-a), and 3,3'-thiodiphenol (BT-a) are examined using a variety of spectroscopic, chromatographic, and thermomechanical techniques. The effect on the polymerization of the monomers is compared using two common compounds, 3,3'-thiodiphenol (TDP) and 3,3'-thiodipropionic acid (TDA), at a variety of loadings. It is found that the diacid has a greater effect on reducing the onset of polymerization and increasing cross-link density and T g for a given benzoxazine. However, the addition of >5 wt % of the diacid had a detrimental effect on the cross-link density, T g, and thermal stability of the polymer. The kinetics of the polymerization of BA-a were found to be well described using an autocatalytic model for which values of n = 1.64 and m = 2.31 were obtained for the early and later stages of reaction (activation energy = 81 kJ/mol). Following recrystallization the same monomer yielded values n = 1.89, m = 0.89, and E a = 94 kJ/mol (confirming the influence of higher oligomers on reactivity). The choice of additive (in particular the magnitude of its pK a) appears to influence the nature of the network formation from a linear toward a more clusterlike growth mechanism.
SMITH PA, WOOD J (1990) POISSON RATIO AS A DAMAGE PARAMETER IN THE STATIC TENSILE LOADING OF SIMPLE CROSSPLY LAMINATES, COMPOSITES SCIENCE AND TECHNOLOGY 38 (1) pp. 85-93 ELSEVIER SCI LTD
LEAITY MA, SMITH PA, BADER MG (1992) THE BEHAVIOR OF CROSS-PLY HYBRID MATRIX COMPOSITE LAMINATES .2. MODELING, COMPOSITES 23 (6) pp. 397-405 BUTTERWORTH-HEINEMANN LTD
BONIFACE L, OGIN SL, SMITH PA (1991) STRAIN-ENERGY RELEASE RATES AND THE FATIGUE GROWTH OF MATRIX CRACKS IN MODEL ARRAYS IN COMPOSITE LAMINATES, PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 432 (1886) pp. 427-444 ROYAL SOC LONDON
Dorey RA, Yeomans JA, Smith PA, Pan J (2001) In situ optical dilatometric measurements of the initial stages of sintering of alumina, ACTA MATERIALIA 49 (3) pp. 519-527 PERGAMON-ELSEVIER SCIENCE LTD
Hamerton I, McNamara LT, Howlin BJ, Smith PA, Cross P, Ward S (2014) Kinetics and cure mechanism in aromatic polybenzoxazines modified using thermoplastic oligomers and telechelics, Macromolecules 47 (6) pp. 1935-1945
A series of blends is prepared comprising 2,2-bis(3,4-dihydro-3-phenyl-2H- 1,3-benzoxazine)propane (BA-a) with variously 5, 10, or 20 wt % of a selected oligomer represented by poly(arylsulfone) (PSU) or poly(arylethersulfone) (PES). The oligomers, comprising either chloro-, hydroxyl- or benzoxazinyl- (Bz) terminal functionality, are of low molecular weight (3000-12000 g mol -1). The introduction of the oligomers is shown to initiate the polymerization of a bisbenzoxazine monomer where the terminal functionality of the oligomer is coreactive (e.g., hydroxyl or benzoxazine) without having a detrimental effect on the polymerization kinetics (similar values for the activation energy and orders of reaction are obtained). The introduction of the nonreactive chloro-terminated oligomer appears to favor the formation of an interpenetrating network (IPN) with a higher energy of activation. The thermal stability of the blends is generally increased compared with the polybenzoxazine homopolymer, regardless of the molecular weight or thermoplastic loading. Aside from the aforementioned PSUCl-containing IPN, the nature of the resulting network is slightly modified by the addition of the thermoplastic with similar or slightly elevated cross-link densities recorded (compared with the polybenzoxazine homopolymer). The heterogeneity of the network increases with a broadening of the tan ´ response, suggesting an improvement in the toughness of the resulting blend. © 2014 American Chemical Society.
Tong J, Guild FJ, Ogin SL, Smith PA (1997) Off-axis fatigue crack growth and the associated energy release rate in composite laminates, APPLIED COMPOSITE MATERIALS 4 (6) pp. 349-359 KLUWER ACADEMIC PUBL
XU XX, CROCROMBE AD, SMITH PA (1994) FATIGUE BEHAVIOR OF JOINTS BONDED WITH EITHER FILLED, OR FILLED AND TOUGHENED, ADHESIVE, INTERNATIONAL JOURNAL OF FATIGUE 16 (7) pp. 469-477 BUTTERWORTH-HEINEMANN LTD
Crunkhorn BB, Whiter JT, Ham A, Mulheron M, Smith PA (2004) Assessing the ability of interactive pipe liners to withstand host-pipe failure, JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA 53 (5) pp. 299-312 I W A PUBLISHING
Surface treatments of silicon carbide have been investigated with the aim of improving the strength of the bond between the ceramic and an epoxy adhesive. Three surface conditions have been characterised; as-fired, air re-fired and KrF laser processed. A number of characterisation techniques have been used to determine the morphological and chemical changes that have occurred to the surface. Scanning electron microscopy of the re-fired and laser processed samples showed surfaces that appeared glassy, with the laser processed surface showing a different morphology. X-ray photoelectron spectroscopy indicated both treatments had oxidised the surface and the laser processed surface also had a greater concentration of hydroxyl groups. The wettability of both surfaces had improved and the laser processed surface was found to be highly hydrophilic. Mechanical testing of joints prepared with this technique showed them to have the highest strength in tension, with the locus of failure being cohesive. © 2013 The Authors.
Hamerton I, McNamara LT, Howlin BJ, Smith PA, Cross P, Ward S (2014) Examining the kinetics of the thermal polymerization of commercial aromatic bis-benzoxazines, Journal of Polymer Science, Part A: Polymer Chemistry 52 (14) pp. 2068-2081
Three commercial bis-benzoxazine monomers based on the aniline derivatives of bisphenol A (BA-a), bisphenol F (BF-a), and 3,3-thiodiphenol (BT-a) are examined using a variety of spectroscopic, chromatographic, and thermomechanical techniques. The kinetics of the polymerization of BA-a were found to be well described using an autocatalytic model for which values of n = 1.39 and m = 2.49 were obtained for the early and later stages of reaction respectively (activation energy = 81-88 kJ/mol.). Following recrystallization the same monomer yielded values of n = 1.80, m = 0.92, and Ea = 94-97 kJ/mol. BF-a and BT-a were also found to be well described using an autocatalytic model for which values of n = m = 2.11 (BF-a) and n = 2.10, m = 1.47 (BT-a) were obtained for the early and later stages of reaction (activation energy = 80-84 kJ/mol. for BF-a and 88-95 kJ/mol. for BT-a). The kinetic data are compared with parallel studies involving chemically initiated benzoxazine monomers. Molecular simulation is used to examine the rotational freedom of the central bridging units and this is related to the degree of conversion achieved. © 2014 Wiley Periodicals, Inc.
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.
Blissett MJ, Smith PA, Yeomans JA (1997) Thermal shock behaviour of unidirectional silicon carbide fibre reinforced calcium aluminosilicate, JOURNAL OF MATERIALS SCIENCE 32 (2) pp. 317-325 CHAPMAN HALL LTD
Shenoi R, Moy S, Hollaway L, Smith P (2004) Untitled, PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-STRUCTURES AND BUILDINGS 157 (1) pp. 1-2
THOMAS TELFORD SERVICES LTD
Gao F, Boniface L, Ogin SL, Smith PA, Greaves RP (1999) Damage accumulation in woven-fabric CFRP laminates under tensile loading: Part 1. Observations of damage accumulation, COMPOSITES SCIENCE AND TECHNOLOGY 59 (1) pp. 123-136 ELSEVIER SCI LTD
PRYCE AW, SMITH PA (1992) BEHAVIOR OF UNIDIRECTIONAL AND CROSSPLY CERAMIC MATRIX COMPOSITES UNDER QUASI-STATIC TENSILE LOADING, JOURNAL OF MATERIALS SCIENCE 27 (10) pp. 2695-2704 CHAPMAN HALL LTD
Ogi K, Smith PA (2002) Modeling creep and recovery behavior of a quasi-isotropic laminate with transverse cracking, ADVANCED COMPOSITE MATERIALS 11 (1) pp. 81-93 VSP BV
SOUTIS C, FLECK NA, SMITH PA (1991) COMPRESSION FATIGUE BEHAVIOR OF NOTCHED CARBON-FIBER EPOXY LAMINATES, INTERNATIONAL JOURNAL OF FATIGUE 13 (4) pp. 303-312 BUTTERWORTH-HEINEMANN LTD
Wahab MMA, Ashcroft IA, Crocombe AD, Smith PA (2003) Fatigue crack propagation in adhesively bonded joints, ADVANCES IN FRACTURE AND DAMAGE MECHANICS 251-2 pp. 229-233 TRANS TECH PUBLICATIONS LTD
Tong J, Guild FJ, Ogin SL, Smith PA (1997) On matrix crack growth in quasi-isotropic laminates - II. Finite element analysis, COMPOSITES SCIENCE AND TECHNOLOGY 57 (11) pp. 1537-1545 ELSEVIER SCI LTD
POWELL KL, YEOMANS JA, SMITH PA (1993) INDENTATION BEHAVIOR OF CONTINUOUS FIBER-REINFORCED CERAMIC-MATRIX COMPOSITES, BRITISH CERAMIC TRANSACTIONS 92 (1) pp. 23-27 INST MATERIALS
Belmonte HMS, Ogin SL, Smith PA, Lewin R (2004) A physically-based model for the notched strength of woven quasi-isotropic CFRP laminates, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 35 (7-8) pp. 763-778 ELSEVIER SCI LTD
The characterization by DMA and compressive stress-strain behavior of an epoxy resin cured with a number of liquid amines is studied in this work along with predictions of the associated properties using Group Interaction Modeling (GIM). A number of different methods are used to assign two of the input parameters for GIM, and the effect on the predictions is investigated. Excellent predictions are made for the glass transition temperature, along with good predictions for the beta transition temperature and modulus for the majority of resins tested. Predictions for the compressive yield stress and strain are less accurate, due to a number of factors, but still show reasonable correlation with the experimental data. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3130-3141, 2013 Copyright © 2013 Wiley Periodicals, Inc.
HITCHEN SA, OGIN SL, SMITH PA (1995) EFFECT OF FIBER LENGTH ON FATIGUE OF SHORT CARBON-FIBER EPOXY COMPOSITE, COMPOSITES 26 (4) pp. 303-308 BUTTERWORTH-HEINEMANN LTD
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.
Kaddour AS, Hinton MJ, Li S, Smith PA (2011) Damage prediction in polymeric composites: Up-date of Part(A) of the Third World-Wide Failure Exercise (WWFE-III), ICCM International Conferences on Composite Materials
A high profile international activity is currently underway to assess the maturity of well established methodologies for the prediction of damage (matrix cracking and delamination) and ultimate failure in composite laminates. The activity is known as the 3 World-Wide Failure Exercise (WWFE-III). The predictions are made 'blindly' by the originators of those well established methodologies, who accepted an invitation to take part in the exercise. The organisers of the WWFE-III have provided the participating groups (originators) with comprehensive material property data and a full description of 13 challenging Test problems to be solved and used in their analysis. In this paper, an up-date is given regarding the progress made by the participants for applying their models to solve the specified Test Cases. A wide variety of approaches have been implemented and some of the results are described briefly. Copyright ©?QinetiQ Ltd 2011.
Graham DP, Rezai A, Baker D, Smith PA, Watts JF (2011) A hybrid joining scheme for high strength multimaterial joints, ICCM International Conferences on Composite Materials
An advanced method for joining fibre reinforced polymers to metallic substrates has been investigated. The solution was shown to offer improvements in strength, toughness (as indicated by the area under the load-displacement curve) and damage tolerance (residual strength after impact) under a range of test conditions.
Bysh IN, Crocombe AD, Smith PA (1996) Determining the effective material properties of damaged particle-filled adhesives, JOURNAL OF ADHESION 58 (3-4) pp. 205-226 GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP
Surface treatments of alumina have been investigated with the aim of increasing the strength of the bond created between the alumina and a toughened epoxy adhesive. Four surface conditions have been assessed: as-fired; grit blasted; and krypton fluoride excimer laser treated under two sets of conditions. Compared with the as-fired surface, the grit blasted surface was rougher with poorer wettability, probably due to surface contamination. It was found that the laser treatments removed some of the sintering additives and caused rounding of the alumina grains, slightly increasing the surface roughness. Further, the laser treatment led to an increased surface energy and wettability, which has been linked tentatively to an observed increase in the hydroxyl groups on the surface. The adhesive bond strength was assessed by testing joints in tension and shear. It was found that the laser treated surfaces demonstrated slight improvements in bond strength, with a cohesive failure of the adhesive in tension for surfaces subjected to one of the two laser treatments, compared with failure at the interface for the as-fired, grit blasted and other laser treated samples in tension and for all samples in shear. Thus, it has been demonstrated that modifications to the surface of alumina can result in mechanical and chemical changes which affect roughness, wettability, bond strength and the locus of failure.
Boniface L, Ogin SL, Smith PA (1993) Change in thermal expansion coefficient as a damage parameter during thermal cycling of crossply laminates, ASTM Special Technical Publication (1156) pp. 139-160
An experimental and theoretical study of the effects of 90° ply cracking on the thermal expansion coefficients of crossply laminates has been carried out. It has been found experimentally that reductions in the coefficient of thermal expansion of up to 50% are caused by 90° ply cracks induced mechanically, although considerable care is needed in the experimentation. This behavior was modeled using a simple shear-lag analysis, and the resulting analytical expressions are compared with other approaches available in the literature. The growth of matrix cracks in a model GFRP system under severe thermal cycling (77 to 373 K) is investigated. The changes in expansion coefficient are affected by the growth of 0° ply cracks in addition to the 90° ply cracks. The crack growth rate/cyclic strain energy release rate range data are compared with those reported previously for mechanical fatigue cycling of similar material. The two data sets are consistent if plotted in terms of a fracture mechanics parameter which aims to account for the temperature dependence of material properties.
OGIN SL, SMITH PA (1987) A MODEL FOR MATRIX CRACKING IN CROSSPLY LAMINATES, ESA JOURNAL-EUROPEAN SPACE AGENCY 11 (1) pp. 45-60 EUROPEAN SPACE AGENCY
PRYCE AW, SMITH PA (1993) MODELING THE STRESS-STRAIN BEHAVIOR OF UNIDIRECTIONAL CERAMIC-MATRIX COMPOSITE LAMINATES, BRITISH CERAMIC TRANSACTIONS 92 (2) pp. 49-54 INST MATERIALS
Powell KL, Yeomans JA, Smith PA (1993) Localised damage in continuous fibre reinforced ceramic matrix composites, Ceramic Engineering and Science Proceedings 14 (9 -10 pt 2) pp. 890-895
As a precursor to a study of erosive near behaviour of ceramic matrix composites fracture by indentation and single particle impact has been studied in two glass-ceramic/silicon carbide fibre composite systems. The damage has been characterised and quantified using a combination of confocal scanning laser microscopy and scanning electron microscopy. Lateral cracks which form approximately parallel to the surface, have been found to be the predominant damage event. In the calcium alumino-silicate (CAS)/Nicalon system, lateral cracks tend, to form in regions of the matrix which have a high local fibre volume fraction, whilst in the barium magnesium alumino silicate (BMAS)/Tyranno system they tend to avoid fibre-rich regions. These results are consistent with an analysis of residual thermal stresses in the two systems. In CAS/Nicalon the coefficient of thermal expansion of the matrix is greater than that of the fibre. This puts the matrix into axial tension at room temperature with the stress increasing with local fibre volume fraction. In BMAS/Tyranno the reverse in the case. Thus in both systems, the observed damage is a consequence of the residual stress as well as the stress due to the contact event.
Wood AR, Smith PA, Watts JF (2007) The forensic study of single fibre pull-out specimens using ToF-SIMS, COMPOSITE INTERFACES 14 (4) pp. 387-402 VSP BV
BYSH IN, CROCOMBE AD, SMITH PA (1994) THE MODELING OF DAMAGE IN FILLED AND RUBBER-TOUGHENED EPOXY ADHESIVES, VIDE-SCIENCE TECHNIQUE ET APPLICATIONS (272) pp. 495-498 SOC FRANCAISE DU VID
Natural fibres, particularly those which form a waste material from other industries, are of interest to manufacturers as an easily sourced material, from which a composite material could be produced. The current work suggests that a cheap composite with commensurate mechanical properties could be produced based on oil palm fibre.
Reece R, Lekakou C, Smith PA (2014) Sulphur cross-linked graphene nano platelets as structural composite supercapacitor electrodes, 16th European Conference on Composite Materials, ECCM 2014
Graphene nano platelets cross-linked with elemental sulphur have been used as supercapacitor electrode material to provide successful energy storage in a structural device. Chemical crosslinking of the composite produces a mechanically stable material, with both high conductivity and surface area. Characterisation was conducted using scanning electron microscopy and energy dispersive X-ray spectroscopy. Different concentrations of graphene-sulphur are investigated, along with addition of conductive carbon black and multiwall carbon nanotubes. The effects of these variables on the performance of the sulphur cross-linked graphene as a supercapacitor electrode are presented through impedance spectrometry, cyclic voltammetry and galvanostatic charge-discharge. Analysis of the structural performance of the material is conducted by flexural three-point-bend testing.
Tong J, Guild FJ, Ogin SL, Smith PA (1997) On matrix crack growth in quasi-isotropic laminates - I. Experimental investigation, COMPOSITES SCIENCE AND TECHNOLOGY 57 (11) pp. 1527-1535 ELSEVIER SCI LTD
2,2-Bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane (BA-a) is blended with oligomers of polyarylsulfone (PSU) and polyarylethersulfone (PES) of different low/intermediate molecular weights (3000-12 000 g mol-1) and terminal functionality (chloro-, hydroxyl- or benzoxazinyl- (Bz)). Fracture toughness (KIC) is observed to increase from 0.8 MPa m0.5 for cured BA-a to 1 MPa m0.5 with the incorporation of 10 wt % PSU-Bz (12 000 g mol-1). Generally, greater improvements in KIC are observed for the PES oligomers compared with the PSU oligomers of equivalent molecular weight. The terminal functionality of the thermoplastic has a lesser effect on improving toughness than increasing the molecular weight or the nature of the polymer backbone. Surface analysis of the fractured surfaces show greater phase separation and crack pinning in the PES toughened system. Where crack pinning is less obvious, as in the case of hydroxyl-terminated PES (of 6000 g mol-1), this coincides with a drop in fracture toughness. © 2014 American Chemical Society.
Smith PA, Ogin SL (1999) On transverse matrix cracking in cross-ply laminates loaded in simple bending, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 30 (8) pp. 1003-1008 ELSEVIER SCI LTD
Advanced hybrid joints, which incorporate a specially designed array of macro-scale pins that provide mechanical interlocking reinforcement, have been developed in order to address the challenges associated with joining fibre reinforced composites to metals. In the present work, important joint characteristics including strength, mechanical fatigue, damage tolerance and durability have been studied and discussed. The results indicate that with advanced hybrid joints it is possible to achieve the benefits of the respective bonded and bolted systems but with virtually zero net weight gain, or conceivably a weight reduction as the increased performance of the hybrid scheme could facilitate smaller joints. The authors also present initial results from a comprehensive manufacturing and scalability trial, and demonstrate that low-cost, large-scale manufacture of hybrid joints is now feasible. © 2014 Elsevier Ltd. All rights reserved.
Marsden WM, Guild FJ, Ogin SL, Smith PA (1999) Modelling stiffness-damage behaviour of (+/- 45/90)(s) and (90/+/- 45)(s) glass fibre reinforced polymer laminates, PLASTICS RUBBER AND COMPOSITES 28 (1) pp. 30-39 INST MATERIALS
FAN Z, TSAKIROPOULOS P, SMITH PA, MIODOWNIK AP (1993) EXTENSION OF THE HALL-PETCH RELATION TO 2-DUCTILE-PHASE ALLOYS, PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES 67 (2) pp. 515-531 TAYLOR & FRANCIS LTD
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
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.
McCartney LN, Clegg WJ, Mortensen A, Smith PA (2010) A collection of papers on Materials Science to celebrate the 80th birthday of Professor Anthony Kelly, CBE, FRS, PHILOSOPHICAL MAGAZINE 90 (31-32) PII 927158183 pp. 4075-4080 TAYLOR & FRANCIS LTD
Xu XX, Crocombe AD, Smith PA (1996) Fatigue crack growth rates in adhesive joints tested at different frequencies, JOURNAL OF ADHESION 58 (3-4) pp. 191-204 GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP
Smith PA, Boniface L, Glass NFC (1998) A comparison of transverse cracking phenomena in (0/90)(s) and (90/0)(s) CFRP laminates, APPLIED COMPOSITE MATERIALS 5 (1) pp. 11-23 KLUWER ACADEMIC PUBL
Prickett AC, Smith PA, Watts JF (2001) ToF-SIMS studies of carbon-fibre composite fracture surfaces and the development of controlled Mode in situ fracture, SURFACE AND INTERFACE ANALYSIS 31 (1) pp. 11-17 JOHN WILEY & SONS LTD
A thermally-assisted piercing (TAP) process has been investigated as an alternative to current methods of machining holes in thermoplastic composites. The spike force/displacement responses during piercing were affected by both the processing temperature and the size of the heated area, as were the resultant microstructure and subsequent mechanical performance. Overall, the results suggest that for advanced manufacturing of thermoplastic composites, good tensile and compressive open-hole properties are produced in the TAP process when using small heated areas and higher temperatures.
GUILD FJ, OGIN SL, SMITH PA (1993) MODELING OF 90-DEGREES PLY CRACKING IN CROSSPLY LAMINATES, INCLUDING 3-DIMENSIONAL EFFECTS, JOURNAL OF COMPOSITE MATERIALS 27 (7) pp. 646-667 TECHNOMIC PUBL CO INC
Atkinson K, Whiter JT, Smith PA, Mulheron M (2002) Failure of small diameter cast iron pipes, Urban Water 4 (3) pp. 263-271
The in-service strength degradation, as a result of corrosion, of cast iron water distribution pipes has been investigated. The strengths of 1 m lengths of pipe extracted from the ground have been measured in either 3- or 4-point bending and the size of the controlling defect has been estimated by visual examination of the fracture surface. The application of Weibull statistics to the bend test data demonstrates that there is bimodal behaviour which suggests that there are two populations of flaws present. It is postulated that the larger flaw size population is associated with corrosion pits that form during the process of graphitisation, while the smaller flaw size population is associated with the inherent flaws within the (brittle) cast iron pipe material. A critical pit depth is identified at the transition between the two competing flaw populations, where there is a change in slope on the Weibull plot. It is shown also that the residual strength/pit depth data are described equally well by either of the two conventional analyses, i.e. loss of section and fracture mechanics. © 2002 Thames Water Utilities Ltd. Published by Elsevier Science Ltd. All rights reserved.
The results presented in this paper explore the extent to which indentation in the interfacial region of polymer composites can be used to identify, unambiguously, an interphase of distinct elastic properties. Supporting evidence is presented in the form of atomic force microscopy indentation in the interfacial region of two polymer composites, a glass fibre reinforced vinylester and a glass flake reinforced polypropylene, where a transition region of measurement artefact is revealed as opposed to a physically distinct interphase. The conclusions from these tests are augmented by further work on a glass fibre reinforced phenolic using a new in situ method of identifying measurement artefacts. © Institute of Materials, Minerals and Mining 2012.
Blissett MJ, Smith PA, Yeomans JA (1998) Flexural mechanical properties of thermally treated unidirectional and cross-ply Nicalon-reinforced calcium aluminosilicate composites, JOURNAL OF MATERIALS SCIENCE 33 (16) pp. 4181-4190 KLUWER ACADEMIC PUBL
Carter DT, Stansfield N, Mantle RJ, France CM, Smith PA (2008) An investigation of epoxidised linseed oil as an alternative to PVC in flooring applications, INDUSTRIAL CROPS AND PRODUCTS 28 (3) pp. 309-319 ELSEVIER SCIENCE BV
This paper is concerned with modelling damage and fracture in woven fabric CFRP single-lap bolted joints that fail by net-tension. The approach is based on the assumption that damage (matrix cracking, delamination and fibre tow fracture) initiates and propagates from the hole in a self-similar fashion. A traction-separation law (based on physically meaningful material parameters) is implemented within an Extended Finite Element Method (XFEM) framework and used to predict the joint strength. Reasonable agreement between model and experiment was obtained for test configurations covering different weave types and lay-ups, a range of joint geometries (two hole diameters and a range of normalised joint widths) and finger-tight and fully torqued clamp-up conditions. The greatest discrepancies were for situations where the tensile fracture mechanisms were more complex, and hence not captured fully in the model or when bearing failure occurred. © 2014 Elsevier Ltd. All rights reserved.
Ogi K, Smith PA (2002) Characterisation of transverse cracking in a quasi-isotropic GFRP laminate under flexural loading, APPLIED COMPOSITE MATERIALS 9 (2) pp. 63-79 KLUWER ACADEMIC PUBL
The ballistic performance of "smart-sized" S2-glass fibre reinforced epoxy was evaluated in comparison with matrix compatible, matrix semi-compatible and matrix incompatible sized materials. The smart size is a formulation designed to give rate-dependent behaviour. The smart-sized material was shown to exhibit rate dependent changes in interlaminar shear strength and mode I interlaminar fracture toughness testing; the ballistic performance of the material was improved only slightly over compatible sized materials. This is attributed to reduced fibre tensile strength in the smart-sized fibres, which was a competing effect, limiting energy absorption during ballistic impact. Overcoming the fibre strength degradations, which appears to be caused by frictional handling effects, is likely to result in significant improvement in ballistic limit. A hybrid laminate consisting of interleaved plies of the compatible and incompatible sizings described above showed synergistic improvements to ballistic performance above what might be expected through rule of mixtures when incompatible sized plies were located towards the rear of the laminate.
Crunkhorn BB, Whiter JT, Mulheron M, Smith PA (2005) Behaviour of an interactive pipe liner under conditions that may occur following ring fracture of host main, PLASTICS RUBBER AND COMPOSITES 34 (7) pp. 305-310 MANEY PUBLISHING
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,
Wood AR, Watts JF, Smith PA, Mäder E, Gao S-L, Jones FR, Liu Z (2009) Interfacial properties of glass fibre/nanoparticulate reinforced polyester resin, ICCM International Conferences on Composite Materials
The SFPO test and the SFFT have been utilised to determine the interfacial properties of a glass fibre and two resin materials; i) polyester resin (PR) ii) ormosil nanomodified polyester resin (NR). Both methods led to similar trends in the test data. Failure mechanisms were studied using a range of techniques.
Belmonte HMS, Mulheron M, Smith PA (2007) Weibull analysis, extrapolations and implications for condition assessment of cast iron water mains, FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES 30 (10) pp. 964-990 BLACKWELL PUBLISHING
Williams T, Yeomans J, Smith P, Heaton A, Hampson C (2015) Effect of interfacial area on densification and microstructural evolution in silicon carbide-boron carbide particulate composites, JOURNAL OF MATERIALS SCIENCE 51 (1) pp. 353-361 SPRINGER
Saavedra MS, Sims GD, McCartney LN, Stolojan V, Anguita JV, Tan YY, Ogin SL, Smith PA, Silva SRP (2012) Catalysing the production of multiple arm carbon octopi nanostructures, Carbon
Octopus-like carbon nanofibres with leg diameters as small as 9 nm are reported, with a high yield over large areas, using a unique photo-thermal chemical vapour deposition system. The branched nature of these nanostructures leads to geometries ideal for increasing the surface area of contacts for many electronic and electrochemical devices. The manufacture of these structures involves a combination of a polyacrylonitrile/polysiloxane film covering the surface of cupronickel catalysts, supported on silicon. Acetylene is used as the carbon feedstock. High-resolution electron microscopy revealed a relationship between the geometry of the nanoparticles and the catalytic growth process, which can be tuned to maximise geometries (and therefore the surface area) and was obtained with a catalyst size of 125 nm. The technique proposed for growing these carbon octopi nanostructures is ideal to facilitate a new in situ transfer film process to place high-density carbon structures on secondary surfaces to produce high capacitance all-carbon contacts.
Smith PA, Ogin SL (2000) Characterization and modelling of matrix cracking in a (0/90)(2s) GFRP laminate loaded in flexure, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 456 (2003) pp. 2755-2770 ROYAL SOC
Thozhur SM, Crocombe AD, Smith PA, Cowley K, Mullier M (2007) Cutting characteristics of beard hair, JOURNAL OF MATERIALS SCIENCE 42 (20) pp. 8725-8737 SPRINGER
CROCOMBE AD, RICHARDSON G, SMITH PA (1993) MEASURING HYDRO-STATIC DEPENDENT CONSTITUTIVE BEHAVIOR OF ADHESIVES USING A BEND SPECIMEN, JOURNAL OF ADHESION 42 (3) pp. 209-223 GORDON BREACH SCI PUBL LTD
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.
Crocker LE, Ogin SL, Smith PA, Hill PS (1997) Intra-laminar fracture in angle-ply laminates, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 28 (9-10) pp. 839-846 ELSEVIER SCI LTD
Baiocchi L, Capell TF, McDonald SA, Ogin SL, Potluri P, Quaresimin M, Smith PA, Withers PJ, Bogdanovich A (2014) Late-stage fatigue damage in a glass/epoxy non-crimp 3D orthogonal woven fabric composite, 16th European Conference on Composite Materials, ECCM 2014
Damage development in the later stages of the fatigue life of a glass/epoxy non-crimp 3D orthogonal woven fabric composite has been examined using a combination of mechanical testing and damage observations. Changes in both the stiffness reduction rate and the energy dissipation per cycle suggest that there are three stages in the fatigue lifetime. Observations of damage using X-ray micro computed tomography (CT) and optical microscopy within specimens cycled to the beginning of the third stage show extensive matrix cracking extending between surface weft tows, with associated resin pocket cracking. It is suggested that the observation of extensive fibre fractures within sections of warp tows closest to z-crowns is a consequence of stress concentrations due to these cracks.
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.
Le Page BH, Guild FJ, Ogin SL, Smith PA (2004) Finite element simulation of woven fabric composites, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 35 (7-8) pp. 861-872 ELSEVIER SCI LTD
Dorey RA, Yeomans JA, Smith PA (2002) Effect of pore clustering on the mechanical properties of ceramics, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 22 (4) pp. 403-409 ELSEVIER SCI LTD
Chard JM, Basson L, Creech G, Jesson DA, Smith PA (2013) Shades of Green: Preliminary LCA of Biobased Polymer Resins For Composite Materials,
Saleh GM, Wawrzynski J, Caputo S, Peto T, Al turk LI, Wang S, Hu Y, Da Cruz L, Smith P, Tang HL (2016) An automated detection system for microaneurysms that is effective across different racial groups, Journal of Ophthalmology
Hindawi Publishing Corporation
Patients without diabetic retinopathy (DR) represent a large proportion of the
caseload seen by the DR screening service so reliable recognition of the
absence of DR in digital fundus images (DFIs) is a prime focus of automated DR
screening research. We investigate the use of a novel automated DR detection
algorithm to assess retinal DFIs for absence of DR.
A retrospective, masked, controlled image-based study was undertaken. 17,850
DFIs of patients from six different countries were assessed for DR by the
automated system and by human graders. The system?s performance was
compared across DFIs from the different countries/ racial groups.
The sensitivities for detection of DR by the automated system were: Kenya
92.8%, Botswana 90.1%, Norway 93.5%, Mongolia 91.3%, China 91.9%, and UK
90.1%. The specificities were: Kenya 82.7%, Botswana 83.2%, Norway 81.3%,
Mongolia 82.5%, China 83.0% and UK 79%. There was little variability in the
calculated sensitivities and specificities across the six different countries
involved in the study.
These data suggest the possible scalability of an automated DR detection
platform that enables rapid identification of patients without DR across a wide
range of races.
POWELL KL, SMITH PA, YEOMANS JA (1993) ASPECTS OF RESIDUAL THERMAL-STRESSES IN CONTINUOUS-FIBER-REINFORCED CERAMIC-MATRIX COMPOSITES, COMPOSITES SCIENCE AND TECHNOLOGY 47 (4) pp. 359-367 ELSEVIER SCI LTD
Ahmad H, Crocombe AD, Smith PA (2011) Failure modelling of woven GFRP bolted joints under quasi-static loading, ICCM International Conferences on Composite Materials
A 2-D finite element model has been developed to simulate crack growth (net-tension and shear-out failures) in composite bolted joints. Results from the model have been compared with a similar approach from the literature and experimental data for a woven fabric system. Agreement is reasonable in each case.
Topal S, Baiocchi L, Crocombe AD, Ogin SL, Potluri P, Withers PJ, Quaresimin M, Smith PA, Poole MC, Bogdanovich AE (2015) Late-stage fatigue damage in a 3D orthogonal non-crimp woven composite: An experimental and numerical study, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 79 pp. 155-163
ELSEVIER SCI LTD
POWELL KL, YEOMANS JA, SMITH PA (1993) CHARACTERIZATION OF SUBSURFACE DAMAGE IN CERAMIC-MATRIX COMPOSITES BY CONFOCAL SCANNING LASER MICROSCOPY, JOURNAL OF MICROSCOPY-OXFORD 169 pp. 189-195 BLACKWELL SCIENCE LTD
LEAITY MA, SMITH PA, BADER MG, CURTIS PT (1992) THE BEHAVIOR OF CROSS-PLY HYBRID MATRIX COMPOSITE LAMINATES .1. EXPERIMENTAL RESULTS, COMPOSITES 23 (6) pp. 387-395 BUTTERWORTH-HEINEMANN LTD
Riches AM, Yeomans JA, Smith PA (1999) Water-lubricated and dry sliding wear of yttria stabilised zirconia and silicon carbide couples Part I: Wear rates, WEAR 236 (1-2) pp. 285-294 ELSEVIER SCIENCE SA
PRYCE AW, SMITH PA (1994) MATRIX CRACKING IN CROSSPLY CERAMIC-MATRIX COMPOSITES UNDER QUASI-STATIC AND CYCLIC LOADING, ACTA METALLURGICA ET MATERIALIA 42 (3) pp. 861-870 PERGAMON-ELSEVIER SCIENCE LTD
XU XX, CROCOMBE AD, SMITH PA (1994) FREQUENCY EFFECT ON FATIGUE-CRACK GROWTH-RATE IN JOINTS BONDED WITH EITHER FILLED OR FILLED AND TOUGHENED ADHESIVE, VIDE-SCIENCE TECHNIQUE ET APPLICATIONS (272) pp. 232-236 SOC FRANCAISE DU VID
Kaddour AS, Hinton MJ, Smith PA, Li S (2013) Preface, Journal of Composite Materials 47 (20-21)
XU XX, CROCOMBE AD, SMITH PA (1995) MIXED-MODE FATIGUE AND FRACTURE-BEHAVIOR OF JOINTS BONDED WITH EITHER FILLED OR FILLED AND TOUGHENED ADHESIVE, INTERNATIONAL JOURNAL OF FATIGUE 17 (4) pp. 279-286 BUTTERWORTH-HEINEMANN LTD
Balhi N, Vrellos N, Drinkwater BW, Guild FJ, Ogin SL, Smith PA (2006) Intra-laminar cracking in CFRP laminates: observations and modelling, JOURNAL OF MATERIALS SCIENCE 41 (20) pp. 6599-6609 SPRINGER
Ahmad H, Smith PA, Crocombe AD (2012) 3-D modelling of GFRP woven fabric double-lap bolted joint, 8th Asian-Australasian Conference on Composite Materials 2012, ACCM 2012 - Composites: Enabling Tomorrow's Industry Today 2 pp. 1050-1056
In previous work we have used a two-dimensional finite element model to predict the strength of GFRP woven fabric double-lap joint bolted joints that fail in the net-tension mode. The failure criterion was based on a fracture mechanics approach, incorporated within a XFEM framework, developed and validated previously for open-hole failure. Results were compared with experimental data obtained from clamped joints. While agreement between model and experiment showed promise, there are features of the problem, in particular the effect of bolt clamp-up and the associated load transfer as a result of friction, which cannot necessarily be captured with the limits of a two-dimensional model. The present work has therefore developed a three-dimensional model and applied it to the same data set. The effect of clamp-up torque is incorporated by modelling the bolt and washers and introducing a bolt tension, which enables the influence on frictional load transfer and the in-plane stress distributions to be incorporated within the model. The predictions for joint strength were in good agreement with experimental data up to the values of w/d for which the failure mechanism was observed experimentally to change to the bearing failure mode. Copyright © (2012) Asian-Australasian Association for Composite Materials (AACM).
Wahab MMA, Ashcroft IA, Crocombe AD, Smith PA (2002) Numerical prediction of fatigue crack propagation lifetime in adhesively bonded structures, INTERNATIONAL JOURNAL OF FATIGUE 24 (6) PII S0142-1123(01)00173-6 pp. 705-709 ELSEVIER SCI LTD
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.
REZAIFARD AH, BADER MG, SMITH PA (1994) INVESTIGATION OF THE TRANSVERSE PROPERTIES OF A UNIDIRECTIONAL CARBON-EPOXY LAMINATE .1. MATRIX PROPERTIES, COMPOSITES SCIENCE AND TECHNOLOGY 52 (2) pp. 275-285 ELSEVIER SCI LTD
Quasi-static tests have been carried out to characterise mixed-mode fracture using a Double Cantilever Beam (DCB) specimen. The DCB consists of equal thickness mild steel adherends bonded with FM-73M epoxy adhesive and is tested under pure mode I, pure mode II and a range of mode-mixity conditions, using a relatively simple loading fixture. The test method is analysed using closed-form and finite element methods, which agree well provided that the adhesive deformation is considered. The strain energy release rate components at fracture are presented in a conventional GI (mode I)-GII (mode II) failure plot using closed-form Linear Elastic Fracture Mechanics (LEFM) methods reported previously in the literature. The results showed that the strain energy release rate is enhanced in the situation of the mode II (in-plane shearing) dominated mixed mode condition as compared to the mode I (opening mode) dominated mixed mode. © 2010 Elsevier Ltd.
SOUTIS C, FLECK NA, SMITH PA (1991) FAILURE PREDICTION TECHNIQUE FOR COMPRESSION LOADED CARBON FIBER-EPOXY LAMINATE WITH OPEN HOLES, JOURNAL OF COMPOSITE MATERIALS 25 (11) pp. 1476-1498 TECHNOMIC PUBL CO INC
Kaddour AS, Hinton MJ, Li S, Smith PA (2014) The world-wide failure exercises: How can composites design and manufacture communities build their strength, 16th European Conference on Composite Materials, ECCM 2014
© QinetiQ Ltd 2014.In a manner reminiscent to establishing the 'periodic table', researchers and keen material scientists/engineers have been engaged in intensive activities trying to identify their own characteristic model or discover a unique aspect/failure mode in a composites material. No tangible progress could have possibly been achieved without the relentless efforts made by some 40 dedicated developers of advanced methods for failure criteria for composites. They have been at the core of an international initiative, referred to as the World-Wide Failure Exercise (WWFE). It is aimed at establishing the maturity of existing method and the remaining challenges of building the best method to accurately predict the strength of composites materials. The paper deals generally with the three exercise (WWFE, WWFE-II and WFE-III) which have been conducted over the last 20 years. The focus is on some of the lessons emanating from the latest exercise (WWFE-III).
The laser treatment of ceramics can lead to increased concentrations of hydroxyl ions on the surface, resulting in improved adhesive bond strength in quasi-static tests. Whether the improvement can be translated to armor applications is investigated here. The ballistic testing of composite-backed, surface treated and non-treated ?control? alumina and silicon carbide panels was undertaken. The failure locus of the ceramic to adhesive/composite joint and the qualitative degree of damage were assessed. Laser surface treated samples performed better than control samples, with silicon carbide moving from single shot to multi-shot capability, thus giving significant advantages for the deployment of these materials.
The only widely-accepted method of gauging the ballistic performance of a material is to carry out ballistic testing; due to the large volume of material required for a statistically robust test, this process is very expensive. Therefore a new test, or suite of tests, that employ widely-available and economically viable characterisation methods to screen candidate armour materials is highly desirable; in order to design such a test, more information on the armour/projectile interaction is required.
This work presents the design process and results of using an adapted specimen configuration to increase the amount of information obtained from a ballistic test. By using a block of ballistic gel attached to the ceramic, the fragmentation generated during the ballistic event was captured and analysed. In parallel, quasi-static tests were carried out using ring-on-ring biaxial disc testing to investigate relationships between quasi-static and ballistic fragment fracture surfaces. Three contemporary ceramic armour materials were used to design the test and to act as a baseline; Sintox FA alumina, Hexoloy SA silicon carbide and 3M boron carbide.
Attempts to analyse the post-test ballistic sample non-destructively using X-ray computed tomography (XCT) were unsuccessful due to the difference in the density of the materials and the compaction of fragments. However, the results of qualitative and quantitative fracture surface analysis using scanning electron microscopy showed similarities between the fracture surfaces of ballistic fragments at the edges of the tile and biaxial fragments; this suggests a relationship between quasi-static and ballistic fragments created away from the centre of impact, although additional research will be required to determine the reason for this.
Ballistic event-induced porosity was observed and quantified on the fracture surfaces of silicon carbide samples, which decreased as distance from centre of impact increased; upon further analysis this porosity was linked to the loss of a boron-rich second phase. Investigating why these inclusions are lost and the extent of the effect of this on ballistic behaviour may have important implications for the use of multi-phase ceramic materials as armour.
Three measurement techniques used to measure the glass transition temperature (Tg) have been subjected to a critical comparison; dynamic mechanical analysis (DMA), thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). A new procedure, whereby different specimens are tested over a range of heating rates, has been used in order to eliminate the effects of thermal lag and determine a Tg independent of heating rate (Tg(0)). It has been shown that for measurements of Tg(0) for composites, the DMA thermal lag ?corrected? method gave the most reliable data. The work has provided additional guidance on these techniques that could usefully be incorporated in future standards, to improve precision, comparisons and consistency of Tg measurement.
The purpose of the study is to accelerate the development of ceramic materials for armour applications, by substantially increasing the information obtained from a high-energy projectile impact event. This has been achieved by modifying an existing test configuration to incorporate a block of ballistic gel, attached to the strike face of a ceramic armour system, to capture fragments generated during the ballistic event such that their final positions are maintained. Three different materials, representative of the major classes of ceramics for armour applications, alumina, silicon carbide and boron carbide, have been tested using this system. Ring-on-ring biaxial disc testing has also been carried out on the same materials. Qualitative analysis of the fracture surfaces using scanning electron microscopy and surface roughness quantification, via stereoimaging, has shown that the fracture surfaces of biaxial fragments and ballistic fragments recovered from the edges of the tile are indistinguishable. Although the alumina and boron carbide fragments generated from areas closer to the point of impact were also similar, the silicon carbide fragments showed an increase in porosity with respect to the fragments from further away and from biaxial testing. This porosity was found to result from the loss of a boron-rich second phase, which was widespread elsewhere in the material, although the relevance of this to ballistic performance needs further investigation. The technique developed in this work will help facilitate such studies.
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.
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.
Measurement of the degree of cure of composite materials is vital to both research and manufacture of these materials. The glass transition temperature (Tg) is a measurable material property that can be used as an indicator of the degree of cure. The three most common thermal analysis techniques used to measure Tg are DMA, TMA and DSC (i.e. dynamic mechanical analysis, thermomechanical analysis and differential scanning calorimetry). There is a current need to improve the experimental methods and analysis of data when using these techniques, where issues such as thermal lag can negatively impact data precision. In this work, a method using multiple tests at different heating rates has been applied to these three techniques to eliminate the effect of thermal lag as well as assess other variables that can influence test data; specimen moisture condition, specimen thickness and fibre type. It was shown that while thermal lag can be accounted for, there are remaining slight differences between DMA, TMA and DSC Tg data, which can be expected due to the different response modes involved (e.g. mechanical, thermal expansion, calorimetric). For DMA testing, a simple relationship has been proposed, relating heating rate and specimen thickness, which can account for the effect of thermal lag when comparing data obtained for specimens of different thicknesses or for the same thickness at different heating rates; the relationship is supported by relevant experimental evidence.
It was shown for materials with different degrees of cure that the relationship between Tg and degree of cure followed the same trend regardless of differences in Tg measured by the three techniques. Preliminary experiments indicated that FTIR showed promise for measurement of the degree of cure of composite materials, in addition to measurements by DSC.
Shaving is an everyday act for many people and Gillette is at the forefront of this market. The complex process of designing a razor involves understanding the interaction between the cartridge and the face which are complicated systems in their own right. Wet shaving is a complex tribological process for which the mechanisms and parameters are not well understood. The time and high cost associated with designing razors are a major driving force for developing a technical model of shaving. Friction has been identified as an important parameter influencing consumer relevant attributes such glide and comfort. This thesis focused on breaking the problem down into two key areas, skin friction and hair cutting friction. By combining in-vivo and in-vitro testing capabilities, the key parameters affecting skin friction were determined and quantified. Due to the limited knowledge of the relative contribution of adhesion and deformation friction to total friction in the biotribology field, this thesis has confirmed past results and expanded on previous knowledge regarding the relative proportion of adhesion and deformation in three lubrication cases, namely, dry, water and oil contacts. Empirical models of skin friction for these three cases were developed to estimate the relative proportion of adhesion and deformation friction. The primary parameters affecting relative proportion of adhesion and deformation included the contact lubrication, probe material, sliding speed, and probe geometry. Further, the results indicated for the oil contact case, for high normal loads and sliding speeds, deformation friction contributed as much as 50% of the total friction. Hair cutting friction was also investigated focusing on two parameters, hair density and hair cutting profile. These two parameters significantly affected hair cutting friction, where increasing hair density and the area under the curve (hair cutting profile) increased hair cutting friction significantly. Two case studies were considered that combined data from skin friction and hair cutting to estimate the relative proportion of adhesion, deformation and hair cutting friction to shaving friction. The results showed, for contacts with water as a lubricant, hair cutting and adhesion friction contribute on average the same proportion (40-40%) and depends on the type of hair cutting profile considered. For contacts with oil as a lubricant, relative contribution of hair cutting friction significantly increases and can be as high as 80% of the shaving friction depending on the hair cutting profile considered.
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.
Ceramic armour must offer protection against armour piercing threats at low weight and affordable cost. As a possible means of improving armour, a range of SiC-B4C composites have been produced and characterised. The degree of contact between the two phases has been quantified and shown to have a strong effect on the densification and microstructure in these materials. This understanding has enabled independent variation of microstructural parameters which are normally interrelated. These were; porosity, SiC:B4C mass ratio, B4C distribution in a SiC matrix and SiC grain size distribution. To assess effects of each of these parameters on ballistic performance V50 testing was carried out, using 7.62 mm armour piercing rounds. The amount of porosity is shown to have a slight effect on V50 and a marked effect on scatter in V50. The pore size distribution is also shown to be important; across a range of pairs of materials with similar total pore volumes but differing pore size distributions, larger pores consistently give lower V50. SiC:B4C mass ratio does not seem to greatly affect V50, potentially allowing application specific cost/weight balances at constant protection level. B4C distribution has a strong effect. In general, for B4C features with diameters ranging from 1 mm to 100 mm, the coarser features performed better. Using coarse B4C particles in a SiC matrix, a V50 of approximately 980 ± 20 m s-1 at a density of 3.00 g cm-3 was achieved reproducibly. This material is preferred due to a combination of relatively lower cost, reduced density and repeatability. Knoop indentation has been used to derive possible merit indices which could potentially be used to rank ballistic materials. These includes analysis of failure probability of indents and the indentation size effect. A preliminary study indicates ballistic impacts may affect SiC polytype composition.