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

TF Capell, J Palaniappan, SL Ogin, AD Crocombe, GT Reed, AM Thorne, L Mohanty, SC Tjin (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, In: JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS9(6)pp. S40-S44
J Palaniappan, H Wang, SL Ogin, A Thorne, GT Reed, AD Crocombe, SC Tjin (2005)Structural health monitoring of bonded composite joints using embedded chirped fibre Bragg gratings, In: ADVANCED COMPOSITES LETTERS14(6)pp. 185-192 ADCOTEC LTD
TJ Young, LE Crocker, WR Broughton, SL Ogin, PA Smith (2013)Observations on interphase characterisation in polymer composites by nano-scale indentation using AFM and FEA, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING50pp. 39-43 ELSEVIER SCI LTD
AD Crocombe, J Palaniappan, SL Ogin, AM Thorne, GT Reed, SC Tjin, L Mohanty (2017)Disbond detection in composite-composite bonded joints using embedded chirped fibre bragg gratings
PR Spendley, SL Ogin, PA Smith, AB Clarke (2009)Design allowables for notched and unnotched CFRP in tension and compression under differing ambient conditions, In: PLASTICS RUBBER AND COMPOSITES38(2-4)pp. 80-86
SA HITCHEN, SL OGIN, PA SMITH, C SOUTIS (1994)THE EFFECT OF FIBER LENGTH ON FRACTURE-TOUGHNESS AND NOTCHED STRENGTH OF SHORT CARBON-FIBER EPOXY COMPOSITES, In: COMPOSITES25(6)pp. 407-413 BUTTERWORTH-HEINEMANN LTD
J Palaniappan, H Wang, SL Ogin, A Thorne, GT Reed, SC Tjin, LN McCartney (2006)Prediction of the reflected spectra from chirped fibre Bragg gratings embedded within cracked crossply laminates, In: MEASUREMENT SCIENCE AND TECHNOLOGY17(6)pp. 1609-1614
AD Crocombe, SL Ogin, GT Reed, AM Thorne, J Palaniappan, T Capell, H Wang, L Mohanty, SC Tjin (2017)An optical method, based on chirped fibre Bragg gratings, for the non-destructive evaluation of disbonding in bonded composite joints
HMS Belmonte, CIC Manger, SL Ogin, PA Smith, R Lewin (2001)Characterisation and modelling of the notched tensile fracture of woven quasi-isotropic GFRP laminates, In: COMPOSITES SCIENCE AND TECHNOLOGY61(4)pp. 585-597 ELSEVIER SCI LTD
NT Guest, DA Tilbrook, SL Ogin, PA Smith (2013)Characterization and modeling of diglycidyl ether of bisphenol-a epoxy cured with aliphatic liquid amines, In: Journal of Applied Polymer Science130(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.

TJ Young, M Monclus, WR Broughton, SL Ogin, PA Smith (2012)Observations on interphase characterisation in polymer composites by nanoscale indentation and use of AFM cantilever torsion to identify measurement artefacts, In: PLASTICS RUBBER AND COMPOSITES41(6)pp. 240-246 MANEY PUBLISHING

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.

TF Capell, J Palaniappan, SL Ogin, AM Thorne, GT Reed, AD Crocombe, SC Tjin, Y Wang, Y Guo (2009)Detection of defects in as manufactured GFRP-GFRP and CFRP-CFRP composite bonded joints using chirped fibre Bragg grating sensors, In: PLASTICS RUBBER AND COMPOSITES38(2-4)pp. 138-145
KR LANGLEY, A MARTIN, SL OGIN (1994)THE EFFECT OF FILLER VOLUME FRACTION ON THE FRACTURE-TOUGHNESS OF A MODEL FOOD COMPOSITE, In: COMPOSITES SCIENCE AND TECHNOLOGY50(2)pp. 259-264 ELSEVIER SCI LTD
SL OGIN, PA SMITH (1987)A MODEL FOR MATRIX CRACKING IN CROSSPLY LAMINATES, In: ESA JOURNAL-EUROPEAN SPACE AGENCY11(1)pp. 45-60 EUROPEAN SPACE AGENCY
J Palaniappan, SL Ogin, AM Thorne, GT Reed, AD Crocombe, TF Capell, SC Tjin, L Mohanty (2008)Disbond growth detection in composite-composite single-lap joints using chirped FBG sensors, In: COMPOSITES SCIENCE AND TECHNOLOGY68(12)pp. 2410-2417 ELSEVIER SCI LTD
L BONIFACE, SL OGIN (1989)APPLICATION OF THE PARIS EQUATION TO THE FATIGUE GROWTH OF TRANSVERSE PLY CRACKS, In: JOURNAL OF COMPOSITE MATERIALS23(7)pp. 735-754 TECHNOMIC PUBL CO INC
J Palaniappan, SL Ogin, TF Capell, AM Thorne, GT Reed, AD Crocombe, SC Tjin, L Mohanty (2007)Reflected spectra predictions for chirped fibre bragg gratings used for disbond detection in composite/composite joints, In: 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.

KF Hoettges, Y Hubner, LM Broche, SL Ogin, GEN Kass, MP Hughes (2008)Dielectrophoresis-activated multiwell plate for label-free high-throughput drug assessment, In: ANALYTICAL CHEMISTRY80(6)pp. 2063-2068 AMER CHEMICAL SOC
WM Marsden, FJ Guild, SL Ogin, PA Smith (1999)Modelling stiffness-damage behaviour of (+/- 45/90)(s) and (90/+/- 45)(s) glass fibre reinforced polymer laminates, In: PLASTICS RUBBER AND COMPOSITES28(1)pp. 30-39 INST MATERIALS
CR Rios, SL Ogin, C Lekakou, KH Leong (2004)Study of the mechanisms of fracture and mechanical properties of an engineering knitted fabric reinforced composite, In: Annual Technical Conference - ANTEC, Conference Proceedings2pp. 1384-1389

In this work the tensile properties and failure mechanisms for a knitted fabric reinforced composite has been investigated. Two commercial composites manufactured with Milano 2×68 tex knitted fabric as a reinforcement and Derakane vinyl ester resin as matrix were analysed. The quasi-static behaviour of the materials has been analysed as a function of tested direction, including an investigation of the damage accumulation. Characterization of these materials under tensile loading has been carried out for monotonic and cyclic loading and the results have been compared with those found earlier for a single layer and the sandwich model material with epoxy resin as matrix1. Various failure mechanisms such as cracking at loop cross-over points, resin matrix cracking, fibre bundle debonding and tensile fracture of fibre bundles in failed specimens were observed.

J Tong, FJ Guild, SL Ogin, PA Smith (1997)Off-axis fatigue crack growth and the associated energy release rate in composite laminates, In: APPLIED COMPOSITE MATERIALS4(6)pp. 349-359 KLUWER ACADEMIC PUBL
LM Broche, Kai Hoettges, Stephen Ogin, George Kass, Michael Hughes (2011)Rapid, automated measurement of dielectrophoretic forces using DEP-activated microwells., In: Electrophoresis32(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

AXH Yong, Graham Sims, SJP Gnaniah, Stephen Ogin, Paul Smith (2017)Heating Rate Effects on Thermal Analysis Measurement of Tg in Composite Materials, In: Advanced Manufacturing: Polymer and Composites Science3(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.

EN Barton, SL Ogin, AM Thorne, GT Reed (2002)Optimisation of the coating of a fibre optical sensor embedded in a cross-ply GFRP laminate, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING33(1)pp. 27-34 ELSEVIER SCI LTD
PA Smith, SL Ogin (1999)On transverse matrix cracking in cross-ply laminates loaded in simple bending, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING30(8)pp. 1003-1008 ELSEVIER SCI LTD
Chirnjeev S. Nagi, Stephen L. Ogin, Iman Mohagheghian, Carol Crean, Andrew D. Foreman (2020)Spray deposition of graphene nano-platelets for modifying interleaves in carbon fibre reinforced polymer laminates, In: Materials & Design193108831 Elsevier

This study describes a novel and versatile method of incorporating graphene nano-platelets (GNP) into compos-ite laminates to investigate its effect on mode I and mode II interlaminar fracture toughness (ILFT). Non-woventhermoplastic veil interleaves have been modified by spray deposition with a GNP dispersion to give either a con-tinuous or strip-patterned distribution. The coated interleaves were used to modify the interlaminar region ofcarbonfibre reinforced polymer (CFRP) laminates. The fracture surfaces were characterised by scanning electronand optical microscopy.The continuous GNP distribution in mode I prevented the formation of carbonfibre bridging, resulting in similarinitiation and propagation values. In mode II, the increased thickness of the interlaminar region, coupled with theuneven fracture surface showed the highest increase in the mode II ILFT for the continuous GNP distribution. Thestrip-patterned GNP distribution showed reduced carbonfibre bridging compared to the baseline CFRP and ther-moplastic interleave laminates. This may be due to small scalefibre bridging between the deposited GNP-stripswhich also lead to peaks and troughs in the load-displacement response. In mode II, it is suggested that the de-posited GNP-strips were sufficiently tough to re-direct the propagating crack from the modified interlaminar re-gion to the adjacent ply.

B Johannesson, SL Ogin, MK Surappa, P Tsakiropoulos, S Brynjolfsson, IO Thorbjornsson (2001)Effect of reinforcement geometry on matrix stresses in three aluminium metal matrix composite systems, In: SCRIPTA MATERIALIA45(8)pp. 993-1000 PERGAMON-ELSEVIER SCIENCE LTD
OZ Ajmal, AD Crocombe, MRL Gower, DA Jesson, SL Ogin (2016)DETECTION OF DELAMINATIONS IN 5-HARNESS SATIN GFRP EPOXY LAMINATES USING DIC

Digital Image Correlation (DIC) can be used to obtain full-field strain information of specimens under load. Through analysis of the resultant strain-contours, defects such as delaminations in composite materials can be detected based on their effect on the deformation behaviour. This paper focuses on the use of DIC to detect the presence of fully embedded artificial delaminations, introduced during the manufacturing process, inside a flat panel specimen under three-point bending. Two types of delamination insert have been considered: an insert containing two sealed pieces of PTFE, and an insert consisting of a single sheet of PTFE in combination with a stress-raiser. When tested in three-point bending, the position and approximate size of the delaminations were clearly visible due to the presence of a plateaux in the longitudinal surface strain profile. Finite element modelling predictions were in good agreement with the DIC measurements for both types of artificial delamination.

Osman Ajmal, Andrew Crocombe, MRL Gower, David Jesson, Stephen Ogin (2017)A comparison of the use of 3D DIC and thermography in determining the size and growth of delaminations in woven GFRP epoxy laminates, In: ICCM-21 Proceedings ICCM

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.

SL Ogin, S Topal, L Baiocchi, AD Crocombe, P Potluri, PJ Withers, M Quaresimin, PA Smith, MC Poole, AE Bogdanovich (2015)Late-stage fatigue damage in a 3D orthogonal non-crimp woven composite: an experimental and numerical study, In: Composites Part A: Applied Science and Manufacturing79pp. 155-163

Late-stage fatigue damage of an E-glass/epoxy 3D orthogonal non-crimp textile composite loaded in the warp direction has been investigated using a combination of mechanical testing, X-ray micro computed tomography (μCT), optical microscopy and finite element modelling. Stiffness reduction and energy dissipated per cycle were found to be complementary measurements of damage accumulation, occurring in three stages: a first stage characterised by rapid changes, a more quiescent second stage, followed by a third stage where the (decreasing) stiffness and (increasing) energy dissipation change irregularly and then rapidly, to failure. Microscopy of specimens cycled into the transition between the second and third stages showed macroscopic accumulations of fibre fractures in sections of warp tows which lying adjacent to the surface weft tows which are crowned-over by the Z-tows. At these locations, the warp tow fibres are subjected to stress concentrations both from transverse weft tow matrix cracks and resin pocket cracks.

Y Huebner, KF Hoettges, GEN Kass, SL Ogin, MP Hughes (2005)Parallel measurements of drug actions on Erythrocytes by dielectrophoresis, using a three-dimensional electrode design, In: IEE PROCEEDINGS-NANOBIOTECHNOLOGY152(4)pp. 150-154 INST ENGINEERING TECHNOLOGY-IET
G. Bragagnolo, A. D. Crocombe, S. L. Ogin, I. Mohagheghian, A. Sordon (2020)Skin-core debonding in sandwich panel structures with foam cores
PA Smith, SL Ogin (2000)Characterization and modelling of matrix cracking in a (0/90)(2s) GFRP laminate loaded in flexure, In: PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES456(2003)pp. 2755-2770 ROYAL SOC

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.

DR Mulligan, SL Ogin, PA Smith, GM Wells, CM Worrall (2003)Fibre-bundling in a short-fibre composite: 1. Review of literature and development of a method for controlling the degree of bundling, In: COMPOSITES SCIENCE AND TECHNOLOGY63(5)PII S0266-pp. 715-725 ELSEVIER SCI LTD
AD Crocombe, GT Reed, SL Ogin, AM Thorne, J Palaniappan, TF Capell, SC Tjin, L Mohanty (2017)The use of chirped fibre Bragg grating sensors to monitor disbond growth
Cerise Edwards, M Helliker, BD James, David Jesson, RL Livesey, Stephen Ogin, Matthew Oldfield (2018)The effect of damage on the impact resistance of composite materials, In: 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.

J Tong, FJ Guild, SL Ogin, PA Smith (1997)On matrix crack growth in quasi-isotropic laminates - I. Experimental investigation, In: COMPOSITES SCIENCE AND TECHNOLOGY57(11)pp. 1527-1535 ELSEVIER SCI LTD
Gerald Watt, Andrew Crocombe, Stephen Ogin, Stephen Kyle-Henney (2017)The determination of thermal residual stresses in unidirectional and cross-ply titanium matrix composites using an etch removal method, In: 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.

S Topal, S Ogin, A Crocombe, P Potluri (2014)FINITE ELEMENT MODELLING OF 3D ORTHOGONAL NON-CRIMP WOVEN COMPOSITES, In: 11TH WORLD CONGRESS ON COMPUTATIONAL MECHANICS; 5TH EUROPEAN CONFERENCE ON COMPUTATIONAL MECHANICS; 6TH EUROPEAN CONFERENCE ON COMPUTATIONAL FLUID DYNAMICS, VOLS II - IVpp. 3504-3512
F Gao, L Boniface, SL Ogin, PA Smith, RP Greaves (1999)Damage accumulation in woven-fabric CFRP laminates under tensile loading: 2. Modelling the effect of damage on macro-mechanical properties, In: COMPOSITES SCIENCE AND TECHNOLOGY59(1)pp. 137-145 ELSEVIER SCI LTD
F Gao, L Boniface, SL Ogin, PA Smith, RP Greaves (1999)Damage accumulation in woven-fabric CFRP laminates under tensile loading: Part 1. Observations of damage accumulation, In: COMPOSITES SCIENCE AND TECHNOLOGY59(1)pp. 123-136 ELSEVIER SCI LTD
J Tong, FJ Guild, SL Ogin, PA Smith (1997)On matrix crack growth in quasi-isotropic laminates - II. Finite element analysis, In: COMPOSITES SCIENCE AND TECHNOLOGY57(11)pp. 1537-1545 ELSEVIER SCI LTD
SL Ogin, S Vadlamani, Z Kakaratsios, DA Jesson, AS Kaddour, PA Smith, J Sirichantra, AE Bogdanovich (2011)Damage development in a glass/epoxy non-crimp 3d orthogonal woven fabric composite, In: 18th International Conference on Composite Materials, ICCM18
SL Ogin, AR Sanderson, AD Crocombe, MRL Gower, RJ Lee, SC Tjin, B Lin (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.

H Wang, SL Ogin, AM Thorne, GT Reet (2006)Matrix crack detection by an embedded polarimetric sensor, In: JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY22(2)pp. 220-224 JOURNAL MATER SCI TECHNOL
H Wang, SL Ogin, AM Thorne, GT Reed, M Ussorio (2007)The sensitivity of a polarimetric sensor embedded in unidirectional and cross-ply composite laminates, In: SMART MATERIALS & STRUCTURES16(3)pp. 642-649 IOP PUBLISHING LTD

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.

Chris Dighton, Amir Rezai, Stephen Ogin, John Watts (2019)Atmospheric Plasma Treatment of CFRP Composites to Enhance Structural Bonding Investigated Using Surface Analytical Techniques, In: International Journal of Adhesion and Adhesives91pp. 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.

H Wang, SL Ogin, AM Thorne, GT Reed (2006)Interaction between optical fibre sensors and matrix cracks in cross-ply GFRP laminates. Part 2: Crack detection, In: COMPOSITES SCIENCE AND TECHNOLOGY66(13)pp. 2367-2378 ELSEVIER SCI LTD

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.

SL Ogin, TF Capell, AM Thorne, GT Reed, AD Crocombe, SC Tjin, B Lin (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.

G. Bragagnolo, A.D. Crocombe, S.L. Ogin, I. Mohagheghian, A. Sordon, G. Meeks (2018)Investigation of Skin-Core Debonding in Sandwich Panel Structures with PMI Foam Cores, In: 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.

DT Fishpool, A Rezai, D Baker, SL Ogin, PA Smith (2013)Interlaminar toughness characterisation of 3D woven carbon fibre composites, In: PLASTICS RUBBER AND COMPOSITES42(3)pp. 108-114 MANEY PUBLISHING
C.S. Nagi, S.L. Ogin, I. Mohagheghian, C. Crean, A.D. Foreman (2018)Interlaminar Toughening of Carbon Fibre Reinforced Polymers using Graphene / Thermoplastic Inserts, In: 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.

SL Ogin, L Boniface, MG Bader (1986)FATIGUE GROWTH OF TRANSVERSE PLY CRACKS IN (0/90//2)S GLASS FIBRE REINFORCED AND (0/90//3)S CARBON FIBRE REINFORCED PLASTIC LAMINATES., In: I Mech E Conference Publications (Institution of Mechanical Engineers)pp. 173-178

The growth of individual transverse ply cracks during tension-tension fatigue of (0/90//2)s GFRP and (0/90//3)s CFRP has been observed using transmitted light and penetrant enhanced X-radiography, respectively. The growth rate of cracks in both laminates is independent of crack length but depends on the spacing between the cracks. Very low growth rates occur for small crack spacings or if crack branching occurs. The results are interpreted using a stress intensity factor approach.

SL Ogin, P Brøndsted, J Zangenberg (2016)Composite materials: constituents, architecture and generic damage, In: 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.

Y Huebner, H Mulhall, KF Hoettges, GEN Kass, SL Ogin, MP Hughes (2007)Dielectrophoresis: A new in vitro approach to measure drug-induced cytotoxicity, In: TOXICOLOGY240(3)pp. 183-184

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.

SL Ogin, P Potluri (2016)Textile-reinforced composite materials, In: Handbook of Technical Textiles2(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.

TF Capell, SL Ogin, AD Crocombe, P Peres, D Barnoncel (2011)Detection of disbonding in bonded joints with a spatially displaced CFBG sensor, In: ICCM International Conferences on Composite Materials
BP Arjyal, C Galiotis, SL Ogin, RD Whattingham (1998)Residual strain and Young's modulus determination in cross-ply composites using an embedded aramid fibre strain sensor, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING29(11)pp. 1363-1369 ELSEVIER SCI LTD
F Bassam, L Boniface, K Jones, SL Ogin (1998)On the behaviour of the residual strain produced by matrix cracking in cross-ply laminates, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING29(11)pp. 1425-1432 ELSEVIER SCI LTD
K Sofocleous, SL Ogin, P Tsakiropoulos, V Draconakis, C Doumanidis (2014)Controlled impact testing of woven fabric composites with and without reinforcing shape-memory alloy wires, In: JOURNAL OF COMPOSITE MATERIALS48(30)pp. 3799-3813 SAGE PUBLICATIONS LTD

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

DT Fishpool, A Rezai, D Baker, SL Ogin, PA Smith (2011)Preferential energy absorbing interfacesfor ballistic and structural applications, In: 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.

MP Hughes, SL Ogin, KF Hoettges, R Wattingham (2017)Device for Dielectrophoretic Manipulation of Particles

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.

M Ussorio, H Wang, SL Ogin, AM Thorne, GT Reed, SC Tjin, R Suresh (2006)Modifications to FBG sensor spectra due to matrix cracking in a GFRP composite, In: CONSTRUCTION AND BUILDING MATERIALS20(1-2)pp. 111-118
FJ GUILD, SL OGIN, PA SMITH (1993)MODELING OF 90-DEGREES PLY CRACKING IN CROSSPLY LAMINATES, INCLUDING 3-DIMENSIONAL EFFECTS, In: JOURNAL OF COMPOSITE MATERIALS27(7)pp. 646-667 TECHNOMIC PUBL CO INC
SA HITCHEN, SL OGIN (1993)MATRIX CRACKING AND MODULUS REDUCTION DURING THE FATIGUE OF AN INJECTION-MOLDED GLASS NYLON COMPOSITE, In: COMPOSITES SCIENCE AND TECHNOLOGY47(3)pp. 239-244 ELSEVIER SCI LTD
BH Le Page, CIC Manger, FJ Guild, SL Ogin, PA Smith (2002)Modelling effect of layer shift on properties of woven fabric composites, In: PLASTICS RUBBER AND COMPOSITES31(9)pp. 385-391
LE Crocker, SL Ogin, PA Smith, PS Hill (1997)Intra-laminar fracture in angle-ply laminates, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING28(9-10)pp. 839-846 ELSEVIER SCI LTD
NWA Brown, CM Worrall, SL Ogin, PA Smith (2016)Investigation into the mechanical properties of thermoplastic composites containing holes machined by a thermally-assisted piercing (TAP) process., In: 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.

SA HITCHEN, SL OGIN (1993)DAMAGE ACCUMULATION DURING THE FATIGUE OF AN INJECTION MOLDED GLASS NYLON COMPOSITE, In: COMPOSITES SCIENCE AND TECHNOLOGY47(1)pp. 83-89 ELSEVIER SCI LTD
N Vrellos, SL Ogin, PA Smith (2006)Matrix crack initiation and propagation in laminates with off-axis plies, In: Fracture of Nano and Engineering Materials and Structures - Proceedings of the 16th European Conference of Fracturepp. 1283-1284
K Sofocleous, M Drakonakis, Stephen Ogin, C Doumanidis (2016)The influence of carbon nanotubes and shape memory alloy wires to controlled impact resistance of polymer composites, In: 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.

HO Fatoyinbo, D Kamchis, R Whattingham, SL Ogin, MP Hughes (2005)A high-throughput 3-D composite dielectrophoretic separator, In: IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING52(7)pp. 1347-1349 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
CERISE AUTUMN EDWARDS, STEPHEN LOUIS OGIN, DAVID ALAN JESSON, MATTHEW OLDFIELD, Rebecca Livesey, (2021)Characterisation and ballistic performance of thin pre-damaged resin-starved aramid-fibre composite panels, In: Textile Research Journal

Military personnel use protective armour systems that are frequently exposed to low-level damage, such as non-ballistic impact, wear-and-tear from everyday use, and damage during storage of equipment. The extent to which such low-level pre-damage could affect the performance of an armour system is unknown. In this work, low-level pre-damage has been introduced into a Kevlar/phenolic resin-starved composite panel using tensile loading. The tensile stress-strain behaviour of this eight-layer material has been investigated and has been found to have two distinct regions; these have been understood in terms of the microstructure and damage within the composite panels investigated using micro-computed tomography and digital image correlation. Ballistic testing carried out on pristine (control) and pre-damaged panels did not indicate any difference in the V50 ballistic performance. However, an indication of a difference in response to ballistic impact was observed; the area of maximal local out-ofplane deformation for the pre-damaged panels was found to be twice that of the control panels, and the global out-of-plane deformation across the panel was also larger.

SL Ogin, AD Crocombe, TF Capell, AR Sanderson, RL Rito, Y Guo, SC Tjin, B Lin (2012)The use of chirped fibre Bragg grating sensors to monitor delaminations in composite materials and structures, In: Emerging Technologies in Non-Destructive Testing Vpp. 163-168
G. Bragagnolo, A. Crocombe, S. L. Ogin, I. Mohagheghian, A. Sordon, C. Santoni (2020)Flexural behaviour of foam cored sandwich structures with through-thickness reinforcement Sage Publications
L BONIFACE, SL OGIN, PA SMITH (1991)STRAIN-ENERGY RELEASE RATES AND THE FATIGUE GROWTH OF MATRIX CRACKS IN MODEL ARRAYS IN COMPOSITE LAMINATES, In: PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES432(1886)pp. 427-444 ROYAL SOC LONDON
RL Rito, SL Ogin, AD Crocombe, TF Capell, AR Sanderson, Y Guo, SC Tjin, B Lin (2012)On the use of a CFBG sensor to monitor scarf repairs of composite panels, In: Emerging Technologies in Non-Destructive Testing Vpp. 187-192
FJ GUILD, SL OGIN, PA SMITH (1991)FINITE-ELEMENT MODELING OF TRANSVERSE CRACKING IN COMPOSITE LAMINATES, In: FIRST INTERNATIONAL CONFERENCE ON DEFORMATION AND FRACTURE OF COMPOSITESpp. 36-41
L BONIFACE, SL OGIN, PA SMITH (1991)EFFECT OF TRANSVERSE CRACKS ON LOCAL STRAIN DISTRIBUTION IN CROSSPLY COMPOSITE LAMINATES, In: FIRST INTERNATIONAL CONFERENCE ON DEFORMATION AND FRACTURE OF COMPOSITESpp. 160-165
L Boniface, SL Ogin, PA Smith (1993)Change in thermal expansion coefficient as a damage parameter during thermal cycling of crossply laminates, In: 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.

B JOHANNESSON, SL OGIN (1995)INTERNAL-STRESSES IN PLANAR RANDOM FIBER ALUMINUM COMPOSITES .2. MEAN STRESS HARDENING AND RELAXATION, In: ACTA METALLURGICA ET MATERIALIA43(12)pp. 4349-4356 PERGAMON-ELSEVIER SCIENCE LTD
L Boniface, SL Ogin, PA Smith (1991)Fracture mechanics approaches to transverse ply cracking in composite laminates, In: 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.

SL OGIN, PA SMITH, PWR BEAUMONT (1985)A STRESS INTENSITY FACTOR APPROACH TO THE FATIGUE GROWTH OF TRANSVERSE PLY CRACKS, In: COMPOSITES SCIENCE AND TECHNOLOGY24(1)pp. 47-59 ELSEVIER SCI LTD
TJ Young, MA Monclus, TL Burnett, WR Broughton, SL Ogin, PA Smith (2011)The use of the PeakForceTM quantitative nanomechanical mapping AFM-based method for high-resolution Young's modulus measurement of polymers, In: Measurement Science and Technology22(12)125703pp. ?-? 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.

AR Sanderson, SL Ogin, AD Crocombe, MRL Gower, RJ Lee (2012)Use of a surface-mounted chirped fibre Bragg grating sensor to monitor delamination growth in a double-cantilever beam test, In: Composites Science and Technology72(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.

CR Rios, SL Ogin, C Lekakou, KH Leong (2003)Study of progressive damage in a knitted fabric reinforced composite, In: Annual Technical Conference - ANTEC, Conference Proceedings2pp. 2188-2192

Model sandwich laminates were manufactured by orienting the knitted cloth at a range of angles to the loading direction using a single Milano weft knitted layer sandwiched between outer plies of unidirectional glass reinforced epoxy resin in order to be able to observe progressive damage accumulation along the sample. By this way, the relationship between fibre architecture and damage accumulation under tensile loading, as well as the sequence of damage accumulation has been investigated. Damage has been found to initiate at the loop cross-over points of the knitted fabric structure for all orientations, although the further development of the damage depends on the orientation of the fabric to the applied load. The resultant transparent laminates provide a novel method of monitoring the damage development in a knitted-fabric composite as a function of increasing strain by allowing direct observation of the sequence of damage.

SL OGIN, PA SMITH, PWR BEAUMONT (1985)MATRIX CRACKING AND STIFFNESS REDUCTION DURING THE FATIGUE OF A (0/90)S GFRP LAMINATE, In: COMPOSITES SCIENCE AND TECHNOLOGY22(1)pp. 23-31 ELSEVIER SCI LTD
G. Bragagnolo, A. D. Crocombe, S. L. Ogin, I. Mohagheghian, A. Sordon, G. Meeks, C. Santoni (2019)Investigation of skin-core debonding in sandwich structures with foam cores, In: Materials & Design Elsevier

Debonding between the skins and the core in a sandwich structure is a critical failure mode in automotive applications; once debonding occurs, the load carrying capacity of a sandwich structure drastically decreases. In the present paper, the effect of using three core materials, with different cell characteristics, on the interfacial strength between the foam cores and a CFRP skin is investigated through mechanical testing and numerical modelling. A key finding is that foams with a coarse cellular structure favour a high resin uptake at the interface during the manufacturing process, which results in a stronger interfacial bonding between the foam and the CFRP. During Mode I loading, the thick resin layer at the interface postpones crack initiation and kinking in the core, whilst under Mode II, this resin layer delays the collapse in compression of foam cells under the crack tip. Thus, the importance of including this thick resin layer in the FE modelling was demonstrated. Finally, as the CZM was shown to be unable to predict the unstable crack propagation within the core, an alternative approach was suggested which has the significant benefit of not requiring experimental testing of the interface between the skin and the core.

EN Barton, SL Ogin, AM Thorne, GT Reed, BH Le Page (2001)Interaction between optical fibre sensors and matrix cracks in cross-ply GRP laminates - part 1: passive optical fibres, In: COMPOSITES SCIENCE AND TECHNOLOGY61(13)pp. 1863-1869 ELSEVIER SCI LTD
SA HITCHEN, SL OGIN, PA SMITH (1995)EFFECT OF FIBER LENGTH ON FATIGUE OF SHORT CARBON-FIBER EPOXY COMPOSITE, In: COMPOSITES26(4)pp. 303-308 BUTTERWORTH-HEINEMANN LTD
J Palaniappan, H Wang, SL Ogin, A Thorne, GT Reed, SC Tjin (2005)Use of conventional and chirped optical fibre Bragg gratings to detect matrix cracking damage in composite materials, In: Sensors & Their Applications XIII15pp. 55-60
N Balhi, N Vrellos, BW Drinkwater, FJ Guild, SL Ogin, PA Smith (2006)Intra-laminar cracking in CFRP laminates: observations and modelling, In: JOURNAL OF MATERIALS SCIENCE41(20)pp. 6599-6609 SPRINGER
SL OGIN, PA SMITH (1985)FAST FRACTURE AND FATIGUE GROWTH OF TRANSVERSE PLY CRACKS IN COMPOSITE LAMINATES, In: SCRIPTA METALLURGICA19(6)pp. 779-784 PERGAMON-ELSEVIER SCIENCE LTD
BH Le Page, FJ Guild, SL Ogin, PA Smith (2004)Finite element simulation of woven fabric composites, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING35(7-8)pp. 861-872
DTG Katerelos, A Paipetis, T Loutas, G Sotiriadis, V Kostopoulos, SL Ogin (2009)In situ damage monitoring of cross-ply laminates using acoustic emission, In: PLASTICS RUBBER AND COMPOSITES38(6)pp. 229-234 MANEY PUBLISHING
J Sirichantra, SL Ogin, DA Jesson (2012)The use of a controlled multiple quasi-static indentation test to characterise through-thickness penetration of composite panels, In: Composites Part B: Engineering43(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.

HMS Belmonte, SL Ogin, PA Smith, R Lewin (2004)A physically-based model for the notched strength of woven quasi-isotropic CFRP laminates, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING35(7-8)pp. 763-778
MJ Whiting, SL Ogin (1997)Dislocation wall structures near a stress concentration in fatigued copper polycrystals, In: SCRIPTA MATERIALIA36(7)pp. 763-768 PERGAMON-ELSEVIER SCIENCE LTD
CR Rios, SL Ogin, C Lekakou, KH Leong (2007)A study of damage development in a weft knitted fabric reinforced composite. Part 1: Experiments using model sandwich laminates, In: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING38(7)pp. 1773-1793 ELSEVIER SCI LTD
L BONIFACE, SL OGIN, PA SMITH (1990)COMPLIANCE CRACK LENGTH MEASUREMENTS FOR INDIVIDUAL TRANSVERSE PLY CRACKS IN MODEL ARRAYS, In: DEVELOPMENTS IN THE SCIENCE AND TECHNOLOGY OF COMPOSITE MATERIALSpp. 913-918
Stephen Ogin, RL Rito, Andrew Crocombe (2017)Health monitoring of composite patch repairs using CFBG sensors: experimental study and numerical modelling, In: Composites Part A: Applied Science and Manufacturing100pp. 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.

This thesis focuses on the subject of damage in composite materials and structures, in particular delaminations arising from an impact event and subsequent Mode I and Mode II loading and fatigue delamination growth. Interlaminar fracture toughness values have been calculated from an experimental study for DCB and ENF specimens. Specimens with artificial inserts at two different interfaces were used along with specimens with delaminations introduced from an impact event. The standard analysis method for both Mode I and Mode II has been adapted to account for the delamination away from the mid plane. For Mode I loading, the load to initiate delamination growth from experimental results is in good agreement with the predicted results from the adapted Mode I equation. For Mode II loading, crack migration did not appear obvious from the experimental study, and an adapted equation accounting for delaminations away from the mid plane has been successfully used. A fatigue study on a structural element loaded both in-plane and out of plane has highlighted the complex nature of damage growth in composite structures. The study has highlighted the issues of delamination investigation using the ultrasonic NDT technique, whereby non-critical delamination growth is sometimes masked by the more dominant delamination and as such the complex growth of delaminations within a structure is difficult to quantify using this technique.

BP Arjyal, C Galiotis, SL Ogin, RD Whattingham (1998)Monitoring local strains in cracked cross-ply composites using an embedded aramid fibre strain sensor, In: JOURNAL OF MATERIALS SCIENCE33(11)pp. 2745-2750 KLUWER ACADEMIC PUBL
J Sirichantra, SL Ogin, K Sofocleous, DA Jesson, G Marom, N Galpaz (2009)Controlled impact tests on wovenfabric/ epoxy resin CFRP panels with and without additional carbon nanotube reinforcement, In: 17th International Conference on Composite Materials
TJ Young, M Monclus, WR Broughton, SL Ogin, PA Smith (2009)Characterisation of interfaces in micro- and nano-composites, In: 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

FJ Guild, N Balhi, N Vrellos, SL Ogin, PA Smith (2007)Matrix cracking in CFRP laminates, In: 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.