Stephen Orgin

Professor Stephen Ogin


Professor of Composite Materials and Smart Systems
BSc (Hons) Physics, PhD, CPhys, MInstP
+44 (0)1483 689614
09 AB 03

My publications

Publications

Digital Image Correlation (DIC) can be used to obtain full-field strain information on specimens under load. Through analysis of the resultant strain-contours, defects such as delaminations in composite materials can be detected, based on their effect on the deformation behaviour. This work focusses on the use of the DIC technique and two variations of active thermography (lock-in thermography and pulse thermography) for determining the lengths of delaminations in ?milled-slot? specimens; for each technique, the measured delamination lengths have been compared with visually observed (i.e. photographed) delaminations grown under fatigue loading in transparent woven fabric GFRP specimens. In addition, the DIC results have been interpreted with the aid of a finite element model of the strain distribution in the milled-slot specimens.
It has been found that the DIC technique provides a reasonably good method for measuring the length of the fatigue-grown delaminations after an empirical fit is applied, with the aid of the FE analysis, to overcome complications caused by fibre-bridging. On the other hand, the results using both lock-in and pulse thermography showed reasonable correlations with the visually observed (i.e. photographed) delamination lengths without the need for an empirical fit, although some post-processing of the data was required. For both thermography techniques, there were difficulties in determining the delamination lengths close to the edge of the milled slot.
Young TJ, Crocker LE, Broughton WR, Ogin SL, Smith PA (2013) Observations on interphase characterisation in polymer composites by nano-scale indentation using AFM and FEA, Composites Part A: Applied Science and Manufacturing 50 pp. 39-43
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.
Rios CR, Ogin SL, Lekakou C, Leong KH (2007) Study of damage development in a weft knitted fabric reinforced composite. Part 2: Stress-strain and early cyclic behaviour of composite laminates with realistic fabric layups, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 38 (7) pp. 1794-1808 ELSEVIER SCI LTD
Sofocleous K, Drakonakis M, Ogin SL, Doumanidis C (2016) The influence of carbon nanotubes and shape memory alloy wires to controlled impact resistance of polymer composites, Journal of Composite Materials
Matrix as well as interlayer regions of laminated polymer composites have been reinforced with carbon nanotubes, additionally to shape memory alloy wires, in order to further enhance the overall material toughness and introduce the improved impact resistance mechanisms through micro- and nano-engineering. In this work, we examine carbon fiber reinforced polymer composites with constant carbon fiber volume fraction, further reinforced with carbon nanotube and shape memory alloy wires, under controlled impact. Single-type as well as multiple-type impact tests have been carried out, demonstrating that the energy absorption and damage development are similar in both impact tests for the same material. When the carbon nanotube and shape memory alloy wires reinforcements are compared separately, shape memory alloy-reinforced carbon fiber reinforced polymers present higher energy absorption than the carbon nanotube-reinforced carbon fiber reinforced polymers. When they are combined, although the carbon nanotube + shape memory alloy-reinforced carbon fiber reinforced polymers present similar energy absorption improvement to shape memory alloy-only carbon fiber reinforced polymers, the carbon nanotube addition increases toughness, resulting in damage initiation at higher depths of impact penetration.
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
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
Guest NT, Tilbrook DA, Ogin SL, Smith PA (2013) Characterization and modeling of diglycidyl ether of bisphenol-a epoxy cured with aliphatic liquid amines, Journal of Applied Polymer Science 130 (5) pp. 3130-3141
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.
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
Ogin SL, Sirichantra J, Jesson DA (2010) The use of a controlled multiple impact test to characterise through-thickness penetration of composite panels,
During the impact of thin composite panels, well-defined flaps can develop on the exit face as a consequence of through-thickness penetration of the panel. For certain materials (for example, CFRP panels based on plies of plain-woven fabric) the flaps develop as four triangles, with the apex of each triangle at the point of impact. As the impactor is driven through the panel, the flap (i.e. crack) lengths increase, until complete penetration of the panel by the impactor occurs. In the experiments described within this paper, CFRP panels fabricated from epoxy resin reinforced with plain-woven carbon fibre fabrics have been impacted using controlled multiple impact tests. During these tests, the impactor is driven at a controlled velocity to a particular depth of penetration through the composite panel, withdrawn, and then driven further through the panel subsequently. The experimental results show that the dependence of the flap compliance is proportional to the square of the flap length, which is in agreement with theoretical predictions. This compliance/crack-length also enables a toughness value for the composite panel to be derived that is directly relevant to through-thickness impact. The relationship of this toughness value to measurements of the mode I toughness of the composite panel using single edge notch specimens is also discussed.
Ogin SL, Potluri P (2016) Textile-reinforced composite materials, In: Horrocks AR, Anand SC (eds.), Handbook of Technical Textiles 2 1 pp. 1-26 Woodhead Publishing (Elsevier)
Fibre-reinforced polymer matrix composite materials for engineering structures are now commonplace. Their low densities, combined with high strength and high stiffness, provide many benefits in performance and durability; when combined with the expertise of the current generation of engineers and materials scientists prepared to accept the complexity of designing and fabricating structures using anisotropic materials, the range of applications (from human prosthetics to airplane fuselages) becomes less surprising. Whereas thirty years ago, the majority of high-performance composite materials were manufactured from individual layers of unidirectionally reinforced material, textile-reinforced polymer matrix composites are increasingly used today. This chapter begins with a brief introduction to continuous fibre-reinforced composite materials before describing the various major types of textile-reinforced polymer matrix composite materials based on the following fabric types: two-dimensional woven, braided, knitted, stitched, three-dimensional woven. In each case, an introduction to the mechanical and damage accumulation behaviour, as well as approaches to modelling the composite, are provided.
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.
JOHANNESSON B, OGIN SL (1995) INTERNAL-STRESSES IN PLANAR RANDOM FIBER ALUMINUM COMPOSITES .2. MEAN STRESS HARDENING AND RELAXATION, ACTA METALLURGICA ET MATERIALIA 43 (12) pp. 4349-4356 PERGAMON-ELSEVIER SCIENCE LTD
Fishpool DT, Rezai A, Baker D, Ogin SL, Smith PA (2013) Interlaminar toughness characterisation of 3D woven carbon fibre composites, PLASTICS RUBBER AND COMPOSITES 42 (3) pp. 108-114 MANEY PUBLISHING
Young TJ, Monclus M, Broughton WR, Ogin SL, Smith PA (2012) Observations on interphase characterisation in polymer composites by nanoscale indentation and use of AFM cantilever torsion to identify measurement artefacts, Plastics, Rubber and Composites 41 (6) pp. 240-246
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.
OGIN SL, SMITH PA, BEAUMONT PWR (1985) A STRESS INTENSITY FACTOR APPROACH TO THE FATIGUE GROWTH OF TRANSVERSE PLY CRACKS, COMPOSITES SCIENCE AND TECHNOLOGY 24 (1) pp. 47-59 ELSEVIER SCI LTD
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
Ogin SL, Guo Y, Capell TF, Thorne AM, Reed GT, Tjin SC, Wang Y (2010) Monitoring of disbonding in bonded composite joints using cfbg sensors embedded within the adhesive bondline,
Chirped fibre Bragg grating (CFBG) sensors have been embedded within the adhesive bondline of single-lap bonded composite joints, fabricated using a transparent glass fibre reinforced plastic (GFRP) adherend bonded to a carbon fibre reinforced plastic (CFRP) adherend. During fatigue cycling, disbonds initiated adjacent to the cut ends of one, or both, of the adherends and the disbonds propagated with continued fatigue cycling. The results show that the CFBG sensor within the bondline can detect the initiation of the disbond and can also monitor the position of the disbond front as it propagates during fatigue cycling. As the disbond front propagated, there was reasonable agreement between the measurements of the position of the disbond front using the CFBG sensor spectra and photographic measurements of the location of the disbond front taken through the transparent GFRP adherend. This method of monitoring disbonding (with the sensor embedded in the adhesive bondline) could be used to monitor bonded composite structures when it is difficult to embed the sensors within the adherends themselves.
JOHANNESSON B, OGIN SL (1995) INTERNAL-STRESSES IN PLANAR RANDOM FIBER ALUMINUM COMPOSITES .2. TENSILE TESTS AND CYCLIC BAUSCHINGER EXPERIMENTS AT ROOM-TEMPERATURE AND 77 K, ACTA METALLURGICA ET MATERIALIA 43 (12) pp. 4337-4348 PERGAMON-ELSEVIER SCIENCE LTD
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,
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
Young TJ, Monclus M, Broughton WR, Ogin SL, Smith PA (2009) Characterisation of interfaces in micro- and nano-composites, ICCM 17th International Conferences on Composite Materials
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
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
Saaverda 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 octupi nanostructures, Carbon 50 (6) pp. 2141-2146 Elsevier
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.
Whiting MJ, Ogin SL (1997) Dislocation wall structures near a stress concentration in fatigued copper polycrystals, SCRIPTA MATERIALIA 36 (7) pp. 763-768 PERGAMON-ELSEVIER SCIENCE LTD
Palaniappan J, Ogin SL, Thorne AM, Reed GT, Crocombe AD, Capell TF, Tjin SC, Mohanty L (2008) Disbond growth detection in composite-composite single-lap joints using chirped FBG sensors, COMPOSITES SCIENCE AND TECHNOLOGY 68 (12) pp. 2410-2417 ELSEVIER SCI LTD
Wang H, Ogin SL, Thorne AM, Reed GT, Ussorio M (2007) The sensitivity of a polarimetric sensor embedded in unidirectional and cross-ply composite laminates, Smart Materials and Structures 16 (3) pp. 642-649
Matrix cracking in composite laminates is the first macroscopic damage mode to be readily detected. Polarimetric sensors embedded in composite laminates can detect the development of this damage and they have an advantage over other sensors in being able to sense damage over long gauge lengths (potentially, many metres). In this paper, the sensitivity of a polarimetric sensor manufactured from Hi-Bi PANDA fibre has been measured experimentally and a phase-strain model available in the literature has been used to determine the characteristic parameters of the sensor. The sensitivity of such sensors embedded in unidirectional composites is shown to be in good agreement with theoretical predictions, allowing for material non-uniformity. In the case of cross-ply laminates, which are transversely anisotropic, it is shown that sensor sensitivity is dependent on the relationship of the sensor axes to the composite axes, as well as on the degree of sensor twist. Maximum sensitivity is obtained for a combination of low twist angle and congruence between the sensor optical axes and the composite axes. Twist angles of greater than 90° give rise to sensitivities, which, although lower, are reasonably constant and approximately the same as the sensitivity of the sensor in a unidirectional composite. © IOP Publishing Ltd.
Ussorio M, Wang H, Ogin SL, Thorne AM, Reed GT, Tjin SC, Suresh R (2006) Modifications to FBG sensor spectra due to matrix cracking in a GFRP composite, CONSTRUCTION AND BUILDING MATERIALS 20 (1-2) pp. 111-118 ELSEVIER SCI LTD
Rios CR, Ogin SL, Lekakou C, Leong KH (2007) A study of damage development in a weft knitted fabric reinforced composite. Part 1: Experiments using model sandwich laminates, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 38 (7) pp. 1773-1793 ELSEVIER SCI LTD
LANGLEY KR, MARTIN A, OGIN SL (1994) THE EFFECT OF FILLER VOLUME FRACTION ON THE FRACTURE-TOUGHNESS OF A MODEL FOOD COMPOSITE, COMPOSITES SCIENCE AND TECHNOLOGY 50 (2) pp. 259-264 ELSEVIER SCI LTD
Rito RL, Ogin SL, Crocombe AD, Capell TF, Sanderson AR, Guo Y, Tjin SC, Lin B (2012) On the use of a CFBG sensor to monitor scarf repairs of composite panels, Emerging Technologies in Non-Destructive Testing V - Proceedings of the 5th Conference on Emerging Technologies in NDT pp. 187-192
Scarf repairs are often used for damaged composite structures in order to recover the mechanical properties of the original structure. During service, there is the possibility that damage will occur in the repaired region and hence it would be useful to be able to monitor such repairs. This work investigates the use of chirped fibre Bragg grating (CFBG) sensors to monitor the development of damage initiation and growth in the repaired region. The experimental part of the work uses a model system consisting of a scarf-repaired, transparent GFRP beam. During fatigue loading, damage in the form of cracks initiate at the interface between the scarf-repair and the parent material on the tensile face of the beam, and grows within this region. The modulus reduction as a consequence of crack growth has been monitored and finite-element analysis (FEA) has been used to predict this reduction, with reasonable agreement between experiment and modelling. Using the FEA analysis, predictions have been made of the strain changes in the vicinity of the growing damage and the effect that these would have on reflected spectra recorded by a chirped fibre Bragg grating sensor bonded across the scarf repair. The predictions suggest that as the damage develops within the scarf repair, the strain changes will modify the reflected spectra in such a way that the initiation of damage can be detected and the growth of fatigue cracks associated with the scarf repair can be monitored. The predictions are in good qualitative agreement with experimental results. © 2012 Taylor & Francis Group, London.
Fatoyinbo HO, Kamchis D, Whattingham R, Ogin SL, Hughes MP (2005) A high-throughput 3-D composite dielectrophoretic separator, IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING 52 (7) pp. 1347-1349 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Sanderson AR, Ogin SL, Capell TF, Crocombe AD, Gower MRL, Barton E, Lee RJ, Hawker J (2012) Monitoring the disbonding of a CFRP plate-bonded reinforcement of a structural beam using a chirped FBG sensor, ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials
A surface-mounted CFBG sensor has been used to monitor disbond growth of a CFRP platebonded reinforcement of a structural box-section beam, bonded using a room-temperature cure structural adhesive. These tests are part of a programme to determine whether disbonding of such a plate could be monitored by ambient thermal fluctuations alone with the aid of thermal mismatch strains. Disbonds were introduced by physically cutting the structural adhesive and a range of different disbond lengths and temperatures have been investigated. When monitoring the disbond growth using the CFBG sensors, a distinct peaktrough perturbation in the reflected spectra was indicative of the location of the disbond front during the test. A prediction of the reflected spectrum was in good agreement with the experimentally-determined results, enabling the disbond lengths to be measured using the CFBG sensor technique to within about 3 mm.
Palaniappan J, Ogin SL, Capell TF, Thorne AM, Reed GT, Crocombe AD, Tjin SC, Mohanty L (2007) Reflected spectra predictions for chirped fibre bragg gratings used for disbond detection in composite/composite joints, ICCM International Conferences on Composite Materials
In this paper it is shown that a chirped fibre Bragg grating sensor embedded within a composite adherend can be used to monitor disbond initiation and propagation in an adhesively bonded single lap-joint. Characteristic changes in the reflected spectra from the sensor indicate both disbond initiation and the current position of the disbond front to within about 2 mm (a distance which depends on adherend material and sensor position in relation to the adhesive bondline). When the sensor extends the full overlap length, disbond initiation from either end of the overlap can be monitored. The results have been modelled using a combination of finite-element analysis and commercial software for predicting FBG spectra; the predicted spectra are in very good agreement with experiment. The CFBG sensor technique could provide the basis for monitoring a wide range of bonded joints and structures where one adherend is a composite material.
Capell TF, Ogin SL, Crocombe AD, Peres P, Barnoncel D (2011) Detection of disbonding in bonded joints with a spatially displaced CFBG sensor, ICCM International Conferences on Composite Materials
BONIFACE L, OGIN SL (1989) APPLICATION OF THE PARIS EQUATION TO THE FATIGUE GROWTH OF TRANSVERSE PLY CRACKS, JOURNAL OF COMPOSITE MATERIALS 23 (7) pp. 735-754 TECHNOMIC PUBL CO INC
Ogin SL, Brøndsted P, Zangenberg J (2016) Composite materials: constituents, architecture and generic damage, In: Talreja R, Varna J (eds.), Modeling damage, fatigue and failure of composite materials 1 pp. 3-23 Woodhead Publishing (Elsevier)
This chapter provides an introduction to the generic types of constituents, manufacturing defects and in-service defects to be found in composite materials based on continuous fibres. First, the basic composite constituents are outlined. Next, fibre/matrix debonding, matrix cracking damage, fibre fractures and delaminations are discussed for simple fibre architectures in order to introduce some basic ideas relating to damage accumulation. Subsequent chapters of the book deal with more complex fibre architectures and/or types of loading, and elaborate on the strategies used for modelling damage accumulation.
Palaniappan J, Wang H, Ogin SL, Thorne A, Reed GT, Tjin SC (2005) Use of conventional and chirped optical fibre Bragg gratings to detect matrix cracking damage in composite materials, Sensors & Their Applications XIII 15 pp. 55-60 IOP PUBLISHING LTD
Capell TF, Palaniappan J, Ogin SL, Crocombe AD, Reed GT, Thorne AM, Mohanty L, Tjin SC (2007) The use of an embedded chirped fibre Bragg grating sensor to monitor disbond initiation and growth in adhesively bonded composite/metal single lap joints, JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS 9 (6) pp. S40-S44 IOP PUBLISHING LTD
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
Palaniappan J, Wang H, Ogin SL, Thorne A, Reed GT, Crocombe AD, Tjin SC (2005) Structural health monitoring of bonded composite joints using embedded chirped fibre Bragg gratings, ADVANCED COMPOSITES LETTERS 14 (6) pp. 185-192 ADCOTEC LTD
Hughes MP, Ogin SL, Hoettges KF, Wattingham R (2005) Device for Dielectrophoretic Manipulation of Particles,
GUILD FJ, OGIN SL, SMITH PA (1991) FINITE-ELEMENT MODELING OF TRANSVERSE CRACKING IN COMPOSITE LAMINATES, FIRST INTERNATIONAL CONFERENCE ON DEFORMATION AND FRACTURE OF COMPOSITES pp. 36-41 PLASTICS & RUBBER INST
Brown NWA, Worrall CM, Ogin SL, Smith PA (2016) Investigation into the mechanical properties of thermoplastic composites containing holes machined by a thermally-assisted piercing (TAP) process., Advanced Manufacturing: Polymer and Composites Science Maney Publishing
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.
Wang H, Ogin SL, Thorne AM, Reet GT (2006) Matrix crack detection by an embedded polarimetric sensor, JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY 22 (2) pp. 220-224 JOURNAL MATER SCI TECHNOL
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
Katerelos DTG, Paipetis A, Loutas T, Sotiriadis G, Kostopoulos V, Ogin SL (2009) In situ damage monitoring of cross-ply laminates using acoustic emission, PLASTICS RUBBER AND COMPOSITES 38 (6) pp. 229-234 MANEY PUBLISHING
Johannesson B, Ogin SL, Surappa MK, Tsakiropoulos P, Brynjolfsson S, Thorbjornsson IO (2001) Effect of reinforcement geometry on matrix stresses in three aluminium metal matrix composite systems, SCRIPTA MATERIALIA 45 (8) pp. 993-1000 PERGAMON-ELSEVIER SCIENCE LTD
Huebner Y, Hoettges KF, Kass GEN, Ogin SL, Hughes MP (2005) Parallel measurements of drug actions on Erythrocytes by dielectrophoresis, using a three-dimensional electrode design, IEE PROCEEDINGS-NANOBIOTECHNOLOGY 152 (4) pp. 150-154 INST ENGINEERING TECHNOLOGY-IET
Broche L, Hoettges K, Ogin S, Kass G, Hughes M (2011) Rapid, automated measurement of dielectrophoretic forces using DEP-activated microwells., Electrophoresis 32 (17) pp. 2393-2399 Wiley
Dielectrophoresis (DEP) is a physical effect that generates a force on polarisable particles experiencing a non-homogeneous electric field; studying the effect as a function of frequency allows the determination of the electrical properties of that particle, i.e. the electrical permittivity and conductivity. In the past, DEP-based techniques applied to the measurement of one or several cells at a time have been subject to many sources of noise, which result in an ambiguous or inaccurate result. However, improvements are possible by generating more information from the experiments. In this paper, we present a rapid automated system that measures the DEP spectrum from a large population of cells with a low level of noise using the microwell electrodes, based on a method of analysis that provides additional information about the electrical properties of the cells and a new theoretical approach was developed to obtain accurate, bias-free results in
Huebner Y, Mulhall H, Hoettges KF, Kass GEN, Ogin SL, Hughes MP (2007) Dielectrophoresis: A new in vitro approach to measure drug-induced cytotoxicity, TOXICOLOGY 240 (3) pp. 183-184 ELSEVIER IRELAND LTD
Barton EN, Ogin SL, Thorne AM, Reed GT, Le Page BH (2001) Interaction between optical fibre sensors and matrix cracks in cross-ply GRP laminates - part 1: passive optical fibres, COMPOSITES SCIENCE AND TECHNOLOGY 61 (13) pp. 1863-1869 ELSEVIER SCI LTD
Palaniappan J, Wang H, Ogin SL, Thorne A, Reed GT, Tjin SC, McCartney LN (2006) Prediction of the reflected spectra from chirped fibre Bragg gratings embedded within cracked crossply laminates, MEASUREMENT SCIENCE AND TECHNOLOGY 17 (6) pp. 1609-1614 IOP PUBLISHING LTD
Sirichantra J, Ogin SL, Sofocleous K, Jesson DA, Marom G, Galpaz N (2009) Controlled impact tests on wovenfabric/ epoxy resin CFRP panels with and without additional carbon nanotube reinforcement, ICCM International Conferences on Composite Materials
Plain woven CFRP carbon/epoxy specimens, with and without additional carbon nanotube reinforcement, have been impacted in controlled-impact tests and sectioned subsequently for microstructural investigation. The results suggest that the panels with additional CNT reinforcement have a significantly greater ability to resist impact damage than specimens without CNT reinforcement.
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
Sofocleous K, Ogin SL, Tsakiropoulos P, Draconakis V, Doumanidis C (2014) Controlled impact testing of woven fabric composites with and without reinforcing shape-memory alloy wires, Journal of Composite Materials 48 (30) pp. 3799-3813
© The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.Shape-memory alloy composites are relatively new materials and their behaviour is not yet completely understood. The purpose of this work is to minimise the effect of impact damage on their structural performance. To do that, GFRP woven fabric reinforced epoxy composite panels, with and without additional superelastic shape-memory alloy wires, have been impacted at constant velocities using a servo-hydraulic testing machine, and a digital video camera has been used to monitor the impact event. Single, multiple and partial penetration impact tests have been carried out, and the energy absorption and damage development are similar in all cases for the same material. The benefit of using the superelastic shape-memory alloy wires was seen only at high displacements and when the volume fraction of the wires was high.
HITCHEN SA, OGIN SL (1993) DAMAGE ACCUMULATION DURING THE FATIGUE OF AN INJECTION MOLDED GLASS NYLON COMPOSITE, COMPOSITES SCIENCE AND TECHNOLOGY 47 (1) pp. 83-89 ELSEVIER SCI LTD
Hoettges KF, Hubner Y, Broche LM, Ogin SL, Kass GEN, Hughes MP (2008) Dielectrophoresis-activated multiwell plate for label-free high-throughput drug assessment, ANALYTICAL CHEMISTRY 80 (6) pp. 2063-2068 AMER CHEMICAL SOC
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 50 (6) pp. 2141-2146 Elsevier
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.
Crocombe AD, Capell T, Ogin SL, Reed GT, Thorne AM, Palaniappan J, Tjin SC, Mohanty L (2007) The use of thermal mismatch stresses to detect disbond initiation and propagation in metal/composite bonded joints using a CFBG fibre optic sensor,
Ogin SL, Sanderson AR, Capell TF, Tjin SC, Lin B (2010) Damage initiation and growth in laminates with ply drop-offs under quasi-static and fatigue loading,
The thickness of a laminated composite structure can be varied by reducing the number of plies through the thickness of the composite material (i.e. using ply drop-offs), where one or more plies are terminated prematurely at some position within the composite, or at the surface. One of the disadvantages of using ply drop-offs is the likelihood of stress concentrations at the terminations of the dropped plies, as these stress concentrations frequently lead to the premature development of damage.
In this work, composite coupons with a double ply drop-off have been fabricated using out-of-autoclave CFRP. Coupons cut from the panels have been subjected to quasi-static and fatigue loading and the development of damage has been monitored using microscopy, and in some coupons, by using a chirped fibre Bragg grating (CFBG) sensor. The first damage appeared as resin cracks within the resin pocket associated with the ply drop-off and this damage developed subsequently into delaminations. Under quasi-static loading, the delaminations grew stably within the ply drop-off region with increasing load; under fatigue loading, the delaminations grew with a constant growth rate. The paper will present observations on the initiation and growth of the damage.
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
Arjyal BP, Galiotis C, Ogin SL, Whattingham RD (1998) Residual strain and Young's modulus determination in cross-ply composites using an embedded aramid fibre strain sensor, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 29 (11) pp. 1363-1369 ELSEVIER SCI LTD
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
Guo Y, Ogin SL, Capelll TF, Thorne AM, Reed GT, Wang Y, Tjin SC (2009) Effect of disbond propagation on the reflected spectra of CFBG sensors embedded within the bondline of composite bonded joints, MULTI-FUNCTIONAL MATERIALS AND STRUCTURES II, PTS 1 AND 2 79-82 pp. 2067-2070 TRANS TECH PUBLICATIONS LTD
Fishpool DT, Rezai A, Baker D, Ogin SL, Smith PA (2011) Preferential energy absorbing interfacesfor ballistic and structural applications, ICCM International Conferences on Composite Materials
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.
Palaniappan J, Wang H, Ogin SL, Thorne AM, Reed GT, Crocombe AD, Rech Y, Tjin SC (2007) Changes in the reflected spectra of embedded chirped fibre Bragg gratings used to monitor disbonding in bonded composite joints, COMPOSITES SCIENCE AND TECHNOLOGY 67 (13) pp. 2847-2853 ELSEVIER SCI LTD
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
Sanderson AR, Ogin SL, Crocombe AD, Gower MRL, Lee RJ (2012) Use of a surface-mounted chirped fibre Bragg grating sensor to monitor delamination growth in a double-cantilever beam test, Composites Science and Technology 72 (10) pp. 1121-1126 Elsevier
A surface-mounted chirped fibre Bragg grating (CFBG) sensor has been used for the first time to monitor delamination growth within a composite material (a transparent, unidirectionally reinforced glass fibre/epoxy resin double-cantilever beam (DCB) specimen). The specimens were tested using a constant displacement rate, with the delamination length being measured using complementary techniques: (i) in situ photography, (ii) surface-mounted strain gauges, and (iii) the surface-mounted CFBG sensors. The unidirectionally reinforced DCB specimens showed characteristics typical of such material which complicate the curvature of the beams, i.e. the development of extensive fibre bridging and pronounced R-curve behaviour. To validate the interpretation of the CFBG reflected spectrum, the experimentally determined strains from the surface-mounted strain gauges have been used, together with in situ photographs of the position of the delamination front. Using the CFBG sensor technique, the delamination length was measured to within about 4 mm over the 60 mm sensor length.
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
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
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
BONIFACE L, OGIN SL, SMITH PA (1990) COMPLIANCE CRACK LENGTH MEASUREMENTS FOR INDIVIDUAL TRANSVERSE PLY CRACKS IN MODEL ARRAYS, DEVELOPMENTS IN THE SCIENCE AND TECHNOLOGY OF COMPOSITE MATERIALS pp. 913-918 ELSEVIER APPL SCI PUBL LTD
Capell TF, Ogin SL, Thorne AM, Reed GT, Crocombe AD, Tjin SC, Lin B (2010) Monitoring delaminations in ENF specimens using chirped fibre Bragg grating sensors,
A chirped fibre Bragg grating (CFBG) optical sensor has been used to detect delamination growth in an ENF specimen. CFBG sensors, with a sensor length of 60 mm, have been embedded within ENF specimens fabricated from out-of-autoclave CFRP. Delaminations have been propagated within the specimen from an insert embedded at the specimen midplane during manufacture. The sensor has been interrogated with the specimen subjected to four-point loading, and the perturbations detected within the reflected spectra of the sensor are in reasonable agreement with the physical position of the delaminations measured at the coupon edges. The prediction of the reflected spectrum for one delamination length, using a combination of 3-D finite-element analysis and commercial software for predicting FBG spectra, is in qualitative agreement with the experimental results. Better quantitative agreement is expected to require a more refined finite-element model of the ENF specimen.
Arjyal BP, Galiotis C, Ogin SL, Whattingham RD (1998) Monitoring local strains in cracked cross-ply composites using an embedded aramid fibre strain sensor, JOURNAL OF MATERIALS SCIENCE 33 (11) pp. 2745-2750 KLUWER ACADEMIC PUBL
Young TJ, Monclus MA, Burnett TL, Broughton WR, Ogin SL, Smith PA (2011) The use of the PeakForceTM quantitative nanomechanical mapping AFM-based method for high-resolution Young's modulus measurement of polymers, Measurement Science and Technology 22 (12) 125703 IOP Publishing
PeakForceTM quantitative nanomechanical mapping (QNMTM) 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.
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
Capell TF, Palaniappan J, Ogin SL, Thorne AM, Reed GT, Crocombe AD, Tjin SC, Wang Y, Guo Y (2009) Detection of defects in as manufactured GFRP-GFRP and CFRP-CFRP composite bonded joints using chirped fibre Bragg grating sensors, PLASTICS RUBBER AND COMPOSITES 38 (2-4) pp. 138-145 MANEY PUBLISHING
Ogin SL, Spendley PR, Smith PA, Clarke AB (2010) The relationship between the strength distribution of unnotched and notched composite laminates as a function of test condition,
Simple analytical models are applied in order to explore the relationship between notched and unnotched strength of CFRP laminates under a range of test conditions ? cold dry, room temperature, and hot/wet. The methodology adopted makes use of a stress-based approach for predicting damage growth, in conjunction with a fracture mechanics model for ultimate failure/fracture. Applying the resulting model to the experimental data enables the fracture toughness of the test material to be determined as a function of test condition. The model is also able to demonstrate that at any particular test condition, a given variability in unnotched strength data translates into a smaller variability in the associated notched strength data.
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
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
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
OGIN SL, SMITH PA, BEAUMONT PWR (1985) MATRIX CRACKING AND STIFFNESS REDUCTION DURING THE FATIGUE OF A (0/90)S GFRP LAMINATE, COMPOSITES SCIENCE AND TECHNOLOGY 22 (1) pp. 23-31 ELSEVIER SCI LTD
Wang H, Ogin SL, Thorne AM, Reed GT (2006) Interaction between optical fibre sensors and matrix cracks in cross-ply GFRP laminates. Part 2: Crack detection, Composites Science and Technology 66 (13) pp. 2367-2378
Polarimetric optical fibre sensors have been embedded within the 0° ply and close to the 0°/90° interface of transparent cross-ply GFRP coupons. The coupons have been subjected to an increasing quasi-static load so that transverse ply cracks initiate and propagate across the coupon. Crack accumulation has been monitored using the optical output signal from the polarimetric sensor, strain measurements from a long gauge-length extensometer, load recordings during the test and by video recording of crack development. These combined observations have enabled a direct correlation to be made between matrix crack growth past the sensor and a step-change in the sensor response. The use of band-pass FFT filtering has demonstrated that such cracks could be detected in real time. © 2005 Elsevier Ltd. All rights reserved.
Barton EN, Ogin SL, Thorne AM, Reed GT (2002) Optimisation of the coating of a fibre optical sensor embedded in a cross-ply GFRP laminate, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 33 (1) pp. 27-34 ELSEVIER SCI 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
OGIN SL, SMITH PA (1985) FAST FRACTURE AND FATIGUE GROWTH OF TRANSVERSE PLY CRACKS IN COMPOSITE LAMINATES, SCRIPTA METALLURGICA 19 (6) pp. 779-784 PERGAMON-ELSEVIER SCIENCE LTD
BONIFACE L, OGIN SL, SMITH PA (1991) EFFECT OF TRANSVERSE CRACKS ON LOCAL STRAIN DISTRIBUTION IN CROSSPLY COMPOSITE LAMINATES, FIRST INTERNATIONAL CONFERENCE ON DEFORMATION AND FRACTURE OF COMPOSITES pp. 160-165 PLASTICS & RUBBER INST
Spendley PR, Ogin SL, Smith PA, Clarke AB (2009) Design allowables for notched and unnotched CFRP in tension and compression under differing ambient conditions, Plastics, Rubber and Composites 38 (2-4) pp. 80-86
This paper presents an experimental study which examines the tensile and compressive response of a quasi-isotropic carbon fibre reinforced polymer (CFRP) laminate subjected to ambient conditions and environmental extremes associated with aircraft design. Specimens with and without holes are considered within the context of structural features and associated design allowables. The data obtained, relating to the effect of sample replicates and specimen geometry on the variability in failure strength, support the concept of a reduced qualification test programme for CFRP. © Institute of Materials, Minerals and Mining 2009.
Ogin SL, Crocombe AD, Capell TF, Sanderson AR, Rito RL, Guo Y, Tjin SC, Lin B (2012) The use of chirped fibre Bragg grating sensors to monitor delaminations in composite materials and structures, Emerging Technologies in Non-Destructive Testing V - Proceedings of the 5th Conference on Emerging Technologies in NDT pp. 163-168
Chirped fibre Bragg grating (CFBG) sensors embedded within composite materials have been shown to be able to monitor delamination growth in adhesively bonded single-lap joints, whether the sensors are embedded within a composite adherend or within the adhesive bondline itself. The relative ease of interpretation of CFBG reflected spectra with regard to delamination growth is a consequence of the relationship between the spectral bandwidth of the reflected spectrum (typically 20 nm) and physical locations along the sensor length (typically 60 mm). When the sensor is embedded in, or bonded to, a composite material subjected to a tensile uniform strain, all the grating spacings are increased and the entire spectrum shifts to higher wavelengths-just as for a uniform FBG sensor. However, if the strain field is perturbed by damage in the composite (such as a matrix crack or a delamination), so that the smooth linear increase in the grating spacing is disrupted, then a perturbation appears in the reflected spectrum that can be used to determine the physical location of the damage. In this paper, results on monitoring delamination/disbond growth will be discussed with regard to sensor location, together with the possibility of using the sensors to monitor repaired composite structures. © 2012 Taylor & Francis Group, London.
Vrellos N, Ogin SL, Smith PA (2006) Matrix crack initiation and propagation in laminates with off-axis plies, Fracture of Nano and Engineering Materials and Structures - Proceedings of the 16th European Conference of Fracture pp. 1283-1284
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
Ogin SL, Sanderson AR, Crocombe AD, Gower MRL, Lee RJ, Tjin SC, Lin B (2011) Monitoring crack growth in a DCB test using a surface-bonded chirped FBG sensor,
Delamination growth within transparent, unidirectionally reinforced glass fibre/epoxy doublecantilever beam (DCB) specimens has been monitored using a surface-mounted chirped fibre Bragg grating (CFBG) sensor. The specimens were tested using a constant displacement rate, with the delamination length being measured using (i) surface-mounted CFBG sensors, (ii) in situ photography, and (iii) surface-mounted strain gauges. The DCB specimens showed characteristics typical of such material, with the development of extensive fibre bridging and pronounced R-curve behaviour. A distinct perturbation in the reflected spectra, when monitoring the delamination growth using the CFBG sensors, was indicative of the location of the delamination front during the test. The in situ photographs and the surface strain measurements provided by the strain gauges were used to predict the experimentally determined CFBG reflected spectra, with good agreement between prediction and experiment. These results enabled the delamination length to be measured using the CFBG sensor technique to within 4 mm over the 60 mm sensor length.
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.
HITCHEN SA, OGIN SL (1993) MATRIX CRACKING AND MODULUS REDUCTION DURING THE FATIGUE OF AN INJECTION-MOLDED GLASS NYLON COMPOSITE, COMPOSITES SCIENCE AND TECHNOLOGY 47 (3) pp. 239-244 ELSEVIER SCI LTD
Bassam F, Boniface L, Jones K, Ogin SL (1998) On the behaviour of the residual strain produced by matrix cracking in cross-ply laminates, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 29 (11) pp. 1425-1432 ELSEVIER SCI LTD
Sirichantra J, Ogin SL, Jesson DA (2012) The use of a controlled multiple quasi-static indentation test to characterise through-thickness penetration of composite panels, Composites Part B: Engineering 43 (2) pp. 655-662 Elsevier
During the quasi-static indentation of thin composite panels, well-defined flaps (sometimes called ??petals??)
can develop on the exit face as a consequence of through-thickness penetration of the panel; such
flaps can also be seen in impact tests. The flaps develop as four triangles, with the apex of each triangle at
the point of impact. In this work, thin panels of CFRP with a 0/90 configuration have been subjected to
quasi-static indentation tests and the development of the flaps has been monitored. The results show that
the dependence of the flap compliance is proportional to the square of the flap length, which is in agreement
with theoretical predictions. The determination of the compliance/crack-length relationship
enables a toughness value for fracture of the composite panel to be derived that is directly relevant to
through-thickness penetration of the panel.
Watt G, Crocombe A, Ogin S, Kyle-Henney S (2017) The determination of thermal residual stresses in unidirectional and cross-ply titanium matrix composites using an etch removal method, JOURNAL OF COMPOSITE MATERIALS SAGE PUBLICATIONS LTD
Recent work has shown that a simple rule-of-mixtures approach may be used to predict the stress strain behaviour of a cross-ply metal matrix composite (MMC) laminate. However, the low-strain behaviour was not predicted accurately, probably because thermal residual stresses are obviously not included in such an approach. To increase the understanding of the limitations of the rule-of-mixtures approach for predicting the stress-strain response, the residual strain-state of the fibre reinforcement has been determined using an etching technique (henceforth referred to as the ?total etch removal method?), and results have been compared both with finite element modelling and with thermal residual strain measurements derived from stress-strain curves. The results show that the residual strain distribution in a cross-ply composite may be more complex than previously thought, with the fibres in internal 00 plies having considerably higher thermal residual strains than fibres in external plies. The results confirm that the rule-of-mixtures approximation can be used, with some reservations with regard to the low strain behaviour.
Yong AX, Sims G, Gnaniah S, Ogin SL, Smith PA (2017) Heating Rate Effects on Thermal Analysis Measurement of Tg in Composite Materials, Advanced Manufacturing: Polymer and Composites Science 3 (2) pp. 43-51 Taylor & Francis
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.
Ogin Stephen, Rito RL, Crocombe Andrew (2017) Health monitoring of composite patch repairs using CFBG sensors: experimental study and numerical modelling, Composites Part A: Applied Science and Manufacturing 100 pp. 255-268
This paper presents an experimental and numerical study on the structural health monitoring of composite patch repairs using chirped fibre Bragg grating (CFBG) sensors. The repair consisted of bonding a pre-cured patch of the same, but thinner, material to a parent GFRP panel containing a machined hole, with the sensors embedded in the bond-line. The repaired coupons were subjected to four-point flexural loading in fatigue. Bond-line delamination cracks (disbonds) initiated at both ends of the patch repair and grew towards the centre of the repair. Predictions of the strain distributions enabled the reflected spectra obtained during damage growth to be predicted with good agreement between theory and experiment. For practical applications when using CFBG sensors to monitor patch repairs, the results suggest that two sensors should be included within the bond-line so that both vulnerable edges of the repair can be monitored using the low-wavelength end of a sensor.
Continuous reinforcement metal matrix composites (MMCs) have yet to become widely used within
the aerospace industry. Despite the high stiffness and strength of unidirectional MMCs, the
complexity and inherent cost of manufacture are major factors that have prevented the widespread
uptake of these advanced materials.

Furthermore, the relatively poor mechanical performance of unidirectional MMCs subjected to
transverse loads has largely precluded their use in structures which experience complex loading
(with the notable exception of bladed compressor discs in gas turbines). Recently, TISICS has been involved in projects with two major aerospace companies to investigate the use of titanium and aluminium matrix composites. In both projects it was necessary to examine the properties of less conventional cross-ply composites and the work undertaken by the author in conjunction with these projects forms the basis of this EngD thesis.

A range of MMC layups were tested in tension, compression and shear and detailed microscopy was
undertaken to investigate the failure processes. A simple rule-of-mixtures approach was found to
show good agreement with the unidirectional tensile test results. Subsequently, a more complex
approach taking ?weighted? averages for biaxial and multiaxial laminates at a ply level was developed
and this enabled full tensile response of the composites to be modelled, albeit with some limitations
in low strain response.

Part of the work which was conducted to increase the understanding of cross-ply composites
involved the determination of residual stresses. Although cross-ply MMCs were thought to have
greater axial residual stresses than unidirectional MMCs, the variation of residual stresses
throughout the eight ply laminates was found to change significantly (from 0.37% in the innermost
to 0.23% in the outermost plies) depending on the sub-laminate sequence. Finite element modelling
predictions were compared to the experimental residual stress determination techniques and it was
found that the FE modelling underestimated the strains in cross-ply composites.

Both aluminium and titanium pressure vessels were manufactured and tested; the mechanical data
from pressurisation was compared to simple analytical modelling and macroscale FEA.
Metallographic samples studied from the failed vessels showed deficiencies in manufacture and a
rudimentary form of acoustic emission showed that damage was incurred at relatively low strains,
but did not propagate to failure during the proof test cycles. This suggests that with adequate
provisions, the development of damage within a cross-ply layup does not need to rule out its use in a
non-critical tank application.

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.
A number of studies have been conducted on 3D non-crimp orthogonal woven composites, but their industrial application is still in its infancy. 3D woven composites show increased through-thickness strength, reducing delamination damage, which is often a key failure mechanism for composites under various loading conditions, especially fatigue. This work investigates the fatigue performance and damage development in a 3D non-crimp orthogonal woven composite consisting of three weft tow layers, two warp tow layers, and a through-thickness z-binder that interlaces along the warp-direction. While the properties of carbon fibres are generally superior to glass fibres, they are more expensive. Therefore, it is of interest to see if the fatigue performance of a glass fibre 3D orthogonal weave can be improved via selective hybridisation using a small amount of carbon fibres.
Initial work began on a commercial all-glass 3D orthogonal weave called 3D-78, which was produced by 3TEX. It was found that quasi-static tensile mechanical properties were the same for both warp and weft loading directions, but when loaded in tension-tension fatigue, the warp direction had longer fatigue lifetimes than the weft-direction. The crack density was lower in warp-direction specimens as a result of greater micro-delamination growth blunting stress concentrations around the tips of matrix cracks. The micro-delamination damage in warp-direction fatigue specimens showed a shield-like shape (not previously observed), i.e. wider along one side and narrowing to a point on the other side; where delamination was restricted (at the pointed end), fibre fractures occurred in the adjacent warp tow. The pointed portion of the micro-delamination corresponded to proximity to a z-binder crown. Other damage that was common to both loading directions (warp and weft) included: transverse cracks in transverse tow and resin-rich regions, z-binder debonding, and longitudinal tow splitting cracks. No obvious failure sites were noted for weft-direction fatigue loading.
The second material used, 3DMG, was manufactured by the University of Manchester. This material was produced with two different z-binder tensions. The initial z-binder tension (3DMG-T1) resulted in a higher tensile modulus and strength-to-failure, and lower strain-to-failure, for the warp-direction, while the tensile fatigue properties of both directions were similar. Increasing the z-binder tension (3DMG-T2) reduced the tensile modulus and increased the strain-to-failure of the warp-direction, with these properties now similar in both loading directions; the tensile strength for both loading directions remained similar. However, the fatigue performance of the warp-direction was observed to increase with increased z-binder tension, while the weft-direction remained the same. The damage that developed in both materials was similar to the damage in 3D-78, and remained practically the same regardless of z-binder tension, though the energy dissipated per cycle for warp-direction specimens was higher in 3DMG-T1, which corresponds well with the lower number of cycles to failure.
The final material tested was a University of Manchester hybrid 3D non-crimp orthogonal woven composite, termed 3DMHyb; here the glass fibre z-binder was replaced with carbon fibre; the z-binder tension used here was the same as 3DMG-T2. Generally, the quasi-static properties of this hybrid material were similar in both loading directions, with the exception of the tensile modulus which was approximately 10% higher, indicating that the carbon fibre z-binder may influence low strain properties. Additionally, the properties of 3DMHyb remained similar to 3DMG-T2. For fatigue performance, However, the fatigue lifetime to failure appeared to increase by a factor of just over 2 at lower peak stress/initial peak strains for the hybrid warp-direction specimens. Again, the energy dissipation per cycle was lower for specimens that had larger number of cy
Edwards Cerise, Helliker M, James BD, Jesson David, Livesey RL, Ogin Stephen, Oldfield Matthew (2018) The effect of damage on the impact resistance of composite materials, ECCM18 conference proceedings
Armour which is manufactured and distributed for personnel, vehicle and structural protection, primarily for military or policing applications, undergoes stringent testing to ensure that it can meet the demands of a range of impact scenarios. However, the effects of repetitive low-level damage are not fully understood and, in order to maintain a given level of protection, armour is recalled and replaced periodically, which is costly, and may be unnecessary. This paper reports preliminary studies on the relationship between minor damage and the resulting impact resistance of a woven fabric reinforced composite laminate (E-glass with epoxy resin). Specimens were subjected to displacement-controlled fatigue tests to introduce dispersed damage before being subjected to quasi-static indentation testing. The results showed that during penetration of the specimens, the peak load was reduced by approximately 10% for the pre-fatigued specimens, compared to the non-fatigued specimens, and there was some indication the energy absorption also reduced. It is proposed that the development of fibre fractures during the pre-fatigue of the specimens is the origin of these changes.
Nagi C.S., Ogin S.L., Mohagheghian I., Crean C., Foreman A.D. (2018) Interlaminar Toughening of Carbon Fibre Reinforced Polymers using Graphene / Thermoplastic Inserts, Proceedings of ECCM 18 - 18th European Conference on Composite Materials European Society for Composite Materials
This paper outlines preliminary work developing graphene modified thermoplastic inserts to be used for the toughening of CFRP. The paper outlines laminate
manufacture, mechanical testing and fracture analysis of graphene modified CFRP.
Bragagnolo G., Crocombe A.D., Ogin S.L., Mohagheghian I., Sordon A., Meeks G. (2018) Investigation of Skin-Core Debonding in Sandwich Panel Structures with PMI Foam Cores, Proceedings of ECCM 18 - 18th European Conference on Composite Materials European Society for Composite Materials
The choice of the materials used for the core and skin of a sandwich structure plays an extremely important role in the skin-core interfacial behaviour. In
this paper, three PMI foams are used as core material and the effect of foam type in the skin-core interfacial response is examined.
The range of applications for composite materials is growing, but understanding of the effect of defects is limited, as is the ability to detect them. Versatile non-destructive testing (NDT) techniques, that can be deployed rapidly and reliably, to detect and monitor damage in composite components are vital to the continued growth of this sector.
This research investigates the application of Digital Image Correlation (DIC) as an NDT technique for monitoring delamination defects in Fibre Reinforced Polymer (FRP) composites. The research has matched physical experiments with Finite Element (FE) modelling. Four types of glass-fibre reinforced epoxy matrix composite structural elements were designed and manufactured to assess this application of DIC. The first two types of structural elements were flat coupons containing fully embedded delaminations, artificially introduced using two different methods. It was found that by placing these specimens in three-point bending, near surface delaminations, one ply below the surface being monitored, would cause a plateau in the surface strains. This plateau in strains was used to measure the embedded defect sizes. The size of the delamination was consistently overestimated from the interpretation of the strain fields. This was improved with the assistance of FE modelling to identify the relationship between the feature and the delamination. Pulse thermography was found to be a better technique for measuring the size of these defects.
The third type of specimen was a flat coupon containing a milled-slot, which was fatigued to grow a delamination at the foot of the milled slot, and the delamination measured visually. For this specimen, the DIC results showed good correlation with the visually determined delamination lengths with an empirical fit applied to the strain results. Both lock-in thermography and pulse thermography were used to measure the delamination size of the same specimens and showed reasonable correlation with the visually determined delamination lengths.
Finally, tubular specimens containing embedded PTFE delamination-defects were fatigued at different ratios of tension and torsion. DIC of the specimens loaded at the fatigue load ratio at which the delaminations were grown could not be used to quantify the size of the delaminations.
The work has shown that DIC can be used to monitor delaminations in some structural elements, however the type of loading needs to be considered to ensure sufficient influence on the surface strains to enable strain features that can be used to measure the size of delamination
Dighton Chris, Rezai Amir, Ogin Stephen, Watts John (2019) Atmospheric Plasma Tretment of CFRP Composites to Enhance Structural Bonding Investigated Using Surface Analytical Techniques, International Journal of Adhesion and Adhesives 91 pp. 142-149 Elsevier
This paper considers the effects of an atmospheric plasma treatment (APT) on the surface properties of an amine cured carbon fibre/epoxy resin composite, and how those effects manifest over time. In particular, the ability of the APT to remove a thin layer of silicone-containing, proprietary, release agent (Chemlease® 41 EZ), typically used in the production of composite components, has been investigated. It was concluded that the reduction in water contact angle (WCA) after APT for both the solvent wiped and contaminated surfaces was as a result of an increase in oxygen containing species at the surface, as determined through X-ray photoelectron spectroscopy (XPS). Further, it was found that the APT slightly reduced the failure strength of lap shear specimens for solvent wiped surfaces, whereas an increase in failure strength was observed for silicone contaminated samples. WCA and XPS results suggest that the contaminant layer was not removed, but instead transformed to a more stable inorganic form.
Dighton Chris, Rezai Amir, Ogin Stephen L., Watts John F. (2019) Atmospheric plasma treatment of CFRP composites to enhance structural bonding investigated using surface analytical techniques, International Journal of Adhesion and Adhesives 91 pp. 142-149 Elsevier
This paper considers the effects of an atmospheric plasma treatment (APT) on the surface properties of an amine cured carbon fibre/epoxy resin composite, and how those effects manifest over time. In particular, the ability of the APT to remove a thin layer of silicone-containing, proprietary, release agent (Chemlease® 41 EZ), typically used in the production of composite components, has been investigated. It was concluded that the reduction in water contact angle (WCA) after APT for both the solvent wiped and contaminated surfaces was as a result of an increase in oxygen containing species at the surface, as determined through X-ray photoelectron spectroscopy (XPS). Further, it was found that the APT slightly reduced the failure strength of lap shear specimens for solvent wiped surfaces, whereas an increase in failure strength was observed for silicone contaminated samples. WCA and XPS results suggest that the contaminant layer was not removed, but instead transformed to a more stable inorganic form.