Imperial College London

Professor Emile S Greenhalgh

Faculty of EngineeringDepartment of Aeronautics

Professor of Composite Materials
 
 
 
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Contact

 

+44 (0)20 7594 5070e.greenhalgh CV

 
 
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Location

 

334City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

181 results found

Yu B, Katafiasz TJ, Nguyen S, Allegri G, Finlayson J, Greenhalgh ES, Pinho ST, Pimenta Set al., 2021, Hygrothermal effects on the translaminar fracture toughness of a highly toughened aerospace CFRP: Experimental characterisation and model prediction, Composites Part A: Applied Science and Manufacturing, Vol: 150, Pages: 1-12, ISSN: 1359-835X

The translaminar fracture toughness and its dependence on the environmental condition are key considerations in designing aerospace-grade composites with a high damage tolerance to severe service conditions in terms of temperature and moisture. The present work characterises and models the hygrothermal effects on the translaminar fracture toughness of an interlaminar toughened aerospace carbon/epoxy composite under six environmental conditions: −55 °C, 23 °C, and 90 °C, for both ‘dry’ (i.e. moisture free) and ‘wet’ (fully moisture-saturated) specimens. Cross-ply compact-tension experiments show that the translaminar fracture toughness increases with the rise of temperature for both dry and wet conditions with the latter exhibiting a much greater increase. A model to predict the effect of moisture and temperature on the translaminar fracture toughness is here proposed and developed. This approach yields good agreement with experimental results, and it allows an improved understanding of the complex synergistic effects of interfacial properties on the overall translaminar toughening mechanisms.

Journal article

Qi G, Nguyen S, Anthony DB, Kucernak ARJ, Shaffer MSP, Greenhalgh ESet al., 2021, The influence of fabrication parameters on the electrochemical performance of multifunctional structural supercapacitors, Multifunctional Materials, Vol: 4, Pages: 034001-034001

Journal article

Lee C, Greenhalgh ES, Panesar A, 2021, Optimization of patch-wise laminated composite panels for enhanced dynamic characteristics, Composite Structures, Vol: 269, Pages: 1-17, ISSN: 0263-8223

Fiber-reinforced laminated composites are widely utilized in the transportation industries due to their superior specific stiffness and strength over conventional metals. The most widely used forms of fiber-reinforced composites are in a laminated plate panel. The inherent anisotropy of composites and the associated dynamic loading characteristics make the design process for such a structure very challenging. In particular, the composite panels used for ship structures must be lightweight and robust enough to withstand external dynamic loads such as wave loads. In this study, we present a two-level optimization strategy to improve the modal dynamic stiffness of laminated composite panels utilising lamination parameters and a patch-wise lay-up approach. Numerical results showed a significant increase in fundamental natural frequency and specific dynamic stiffness compared to the quasi-isotropic design.

Journal article

Greenhalgh ES, Canturri C, Katafiasz TJ, 2021, Fractographic study into the effect of drilling damage on bearing mechanisms and performance in carbon-fibre epoxy composites, Engineering Failure Analysis, Vol: 129, Pages: 1-29, ISSN: 1350-6307

With the widespread adoption of polymer composites in primary structures, understanding and prediction of the performance of composite to metal hybrid joints is now critical to engineering design of transport structures. This work investigated the damage processes associated with bearing failure of such composite joints, for both pristine holes and holes damaged during drilling. An aerospace grade composite was drilled under three different conditions, tested to failure under quasi-static double bearing loading, and then characterised using fractographic techniques. In the pristine condition, the initial damage process was 0° longitudinal splitting tangential to the lateral extents of the hole which then dictated the extent of the subsequent bearing damage development. Beneath the bearing face of the hole inclined lines of in-plane microbuckled fibres had developed whilst beyond the constraint of the washer there was considerable delamination and massive out-of-plane fibre microbuckling. As the degree of drilling damage increased, 0° longitudinal split development was inhibited, and the local pre-existing damage at the periphery of the hole had extended into the bearing damage zone, directly initiating out-of-plane fibre microbuckling. Consequently the bearing damage zone exhibited irregular distributions of fibre microbuckles, both across the thickness and depth beneath the bearing face of the hole. The observations in this work provide a means to validate predictive models and offer potential routes to improve bearing performance and the tolerance of laminates with drilling damage when under bearing loads.

Journal article

Abdullah SIBS, Iannucci L, Greenhalgh ES, Ahmad Zet al., 2021, The impact performance of Vectran/Epoxy composite laminates with a novel non-crimp fabric architecture, COMPOSITE STRUCTURES, Vol: 265, ISSN: 0263-8223

Journal article

Abdullah SIBS, Iannucci L, Greenhalgh ES, Ahmad Zet al., 2021, A Plane-Stress Damage Model for Vectran Laminated Composite, APPLIED COMPOSITE MATERIALS, ISSN: 0929-189X

Journal article

Mohsin M, Iannucci L, Greenhalgh E, 2021, On the dynamic tensile behaviour of thermoplastic composite carbon/polyamide 6.6 using split Hopkinson pressure bar, Materials, Vol: 14, ISSN: 1996-1944

A dynamic tensile experiment was performed on a rectangular specimen of a non-crimp fabric (NCF) thermoplastic composite T700 carbon/polyamide 6.6 specimens using a split Hopkinson pressure (Kolsky) bar (SHPB). The experiment successfully provided useful information on the strain-rate sensitivity of the NCF carbon/thermoplastic material system. The average tensile strength at three varying strain rates: 700, 1400, and 2100/s was calculated and compared to the tensile strength measured from a standardized (quasi-static) procedure. The increase in tensile strength was found to be 3.5, 24.2, and 45.1% at 700, 1400, and 2100/s strain rate, respectively. The experimental findings were used as input parameters for the numerical model developed using a commercial finite element (FE) explicit solver LS-DYNA®. The dynamic FE model was validated against experimental gathering and used to predict the composite system’s behavior in various engineering applications under high strain-rate loading conditions. The SHPB tension test detailed in this study provided the enhanced understanding of the T700/polyamide 6.6 composite material’s behavior under different strain rates and allowed for the prediction of the material’s behavior under real-world, dynamic loading conditions, such as low-velocity and high-velocity impact.

Journal article

Nguyen S, Millereux A, Pouyat A, Greenhalgh E, Shaffer M, Kucernak A, Linde Pet al., 2021, Conceptual multifunctional design, feasibility and requirements for structural power in aircraft cabins, Journal of Aircraft: devoted to aeronautical science and technology, ISSN: 0021-8669

This paper presents a theoretical investigation into the potential use of structural power composites in regional aircraft passenger cabins and the corresponding challenges to widespread use, including fire-resistance, long-term cycling performance, and cost. This study focusses on adapting sandwich floor panels with structural power composite face sheets, designed to power the in-flight entertainment system. Using a simple mechanical model to define the structural requirements, based on state-of-the-art laminated structural power composites, a series of electrochemical energy storage performance targets were calculated: a specific energy > 144 Wh/kg, a specific power > 0.29 kW/kg, an in-plane elastic modulus > 28 GPa and in-plane tensile and compressive strengths > 219 MPa. Significantly, the use of a distributed energy storage system offered a significant range of other mass and cost savings, associated with a simplified power system, and the use of ground-generated electrical energy. For an Airbus A220-100, the analysis predicted potential mass and volume savings of approximately 260 kg and 510 land annual reductions in CO2and NOx emissions of approximately 280 tonnes and 1.2 tonnes respectively. This extended design analysis of a specific component highlights both the far-reaching implications of implementing structural power materials and the potential extensive systemic benefits.

Journal article

Katafiasz T, Greenhalgh ES, Allegri G, Pinho ST, Robinson Pet al., 2021, The influence of temperature and moisture on the mode I fracture toughness and associated fracture morphology of a highly toughened aerospace CFRP, Composites Part A: Applied Science and Manufacturing, Vol: 142, ISSN: 1359-835X

This paper addresses the characterisation of the mode I interlaminar fracture toughness of a carbon fibre/epoxy composite material, toughened with thermoplastic particles in the ply interlayers. The characterisation is undertaken at −55 °C, 19 °C, and 90 °C, on both dry and fully moisture saturated coupons. Fractographic observations of the delamination surfaces allows identification of the failure mechanisms. The mode I propagation fracture toughness tested at wet/90 °C exhibits a 176% increase compared to the dry/19 °C specimens, due to enhanced plastic deformation of the interlayers and more prominent fibre bridging. Moisture-saturated coupons tested at −55 °C suffered a 57% reduction of mode I fracture toughness compared to those under dry/19 °C conditions. This is due to the dis-bond and consequent plucking of the thermoplastic particles from the surrounding matrix. This observation points to the fact that wet/cold conditions may represent the worst-case scenario for the interlaminar fracture performance of composite systems toughened with thermoplastic interleaves.

Journal article

Lee C, Greenhalgh E, Shaffer M, Panesar Aet al., 2020, Optimized microstructures for multifunctional structural electrolytes, Multifunctional Materials, Vol: 2, ISSN: 2399-7532

Multifunctional structural materials offer compelling opportunities to realize highly efficient products. However, the need to fulfil disparate functions generates intrinsically conflicting physical property demands. One attractive strategy is to form a bi-continuous architecture of two disparate phases, each addressing a distinct physical property. For example, structural polymer electrolytes combine rigid and ion-conducting phases to deliver the required mechanical and electrochemical performance. Here, we present a general methodology, based on topology optimization, to identify optimal microstructures for particular design considerations. The numerical predictions have been successfully validated by experiments using 3D printed specimens. These architectures are directly relevant to multifunctional structural composites whilst the methodology can easily be extended to identify optimal microstructural designs for other multifunctional material embodiments.

Journal article

Razavi S, Iannucci L, Smith Greenhalgh E, 2020, A piezo smart‐braid harvester and damper for multifunctional fiber reinforced polymer composites, Energy Technology, Vol: 8, Pages: 1-12, ISSN: 2194-4288

The past decade has seen the rapid development of wearable electronics, wireless sensor networks (WSNs), and self‐powered implantable sensors. However, these devices usually require a continuous source of power supply to operate safely and accurately while having the least reliance on conventional battery systems—due to the recharging/maintenance burdens of batteries. Vibration‐based piezoelectric energy harvesting (PEH) from environment, man‐made machinery, and human body movements seems to be a promising solution. Herein, the first integration of a piezoelectric poly(vinylidene fluoride) (PVDF) yarn‐braid microgenerator into a fiber reinforced polymer composite (FRPC) structure is reported. It is demonstrated that the developed smart composite exhibits multifunctional performances, including simultaneous structural (with ≈10% increased Young's modulus), energy harvesting, and vibration damping (with a damping factor of 125%). The results show that an average output voltage of 3.6 V and a power density of 2.2 mW cm−3 can be achieved at strains below 0.15%, under cyclic loading tests between 1 and 10 Hz. Moreover, noticeable improvements are made in the crystallinity percentage and β‐phase content of as‐received PVDF yarns by, respectively, ≈34% and ≈37%, as a result of the applied coreless radial and axial corona poling techniques.

Journal article

De Luca H, Anthony D, Greenhalgh E, Bismarck A, Shaffer Met al., 2020, Piezoresistive structural composites reinforced by carbon nanotube-grafted quartz fibres, Composites Science and Technology, Vol: 198, Pages: 1-12, ISSN: 0266-3538

Nano-engineered fibre/matrix interfaces can improve state-of-the-art fibre-reinforced composites. Grafting carbon nanotubes (CNTs) to high temperature quartz glass fibres produces “hairy” or “fuzzy” fibres, which combine reinforcements at micrometre and nanometre length scales. Fuzzy quartz fibres were produced continuously, reel-to-reel, on whole tows, in an open chemical vapour deposition reactor. The resulting uniform coverage of 200 nm long CNTs increased the interfacial shear strength with epoxy (90.3 ± 2.1 MPa) by 12% compared to the commercially-sized counterpart, as measured by single fibre pull-out tests. The improved interfacial properties were confirmed at the macroscale using unidirectional hierarchical bundle composites, which exhibited a delayed onset of fibre/matrix debonding. Although the quartz fibres are electrically insulating, the grafted CNT create a conductive path, predominantly parallel to the fibres. To explore the applicability for structural health monitoring, the resistivity was recorded in situ during mechanical testing, and correlated with simultaneous acoustic emission data. The baseline resistivity parallel to the fibres (ρ0 = 3.9 ± 0.4 × 10−1 Ω m) displayed a linear piezoresistive response (K = 3.64) until failure at ca. 2.1% strain, also referred to as "gauge factor”, a two-fold improvement over traditional resistance strain gauges (e.g. constantan). Hierarchical, fuzzy quartz fibres, therefore, simultaneously enhance both structural and sensing performance, offering multifunctional opportunities in large composite parts.

Journal article

Senokos E, Anthony D, Nguyen S, Kucernak A, Greenhalgh E, Shaffer Met al., 2020, Manganese dioxide decorated carbon aerogel/carbon fibre composite as a promising electrode for structural supercapacitors, 22nd International Conference on Composite Materials 2019 (ICCM22), Publisher: Engineers Australia, Pages: 1-8

Manganese dioxide electrochemically deposited onto carbon aerogel/carbon fibres (CAG/CF) shows a great potential as an electrode material in multifunctional structural supercapacitors. MnO₂ nanowires grown by a pulse potentiometric method provide a large enhancement in capacitive performance of the carbon electrodes and symmetric supercapacitor devices based on the hybrid material.

Conference paper

Nguyen S, Millereux A, Pouyat A, Greenhalgh E, Shaffer M, Kucernak A, Linde Pet al., 2020, Structural power performance requirements for future aircraft integration, 22nd International Conference on Composite Materials 2019 (ICCM22), Publisher: Engineers Australia, Pages: 1-12

This paper investigates the use of structural power composites in Airbus A220-100 aircraft cabins by integrating floor panels with face sheets made of structural power composites to power the in-flight entertainment system. This application requires a minimum specific energy of 305 Wh/kg and a minimum specific power of 0.610 kW/kg. The static and dynamic loads for which the floor panels must be certified require an in-plane Young’s modulus of 50 GPa, a compressive strength of 225 MPa and a tensile strength of 119 MPa. Structural power composite floor panels are predicted to yield mass savings of 324 kg, annual cost savings of £85,000 per aircraft and annual reductions in CO2 and NOx emissions of 343 tonnes and 1.4 tonnes respectively. However, addressing challenges such as fire-resistance, long term cycling performance and public perception of structural power composites are necessary to enable widespread use of such materials on-board airliners.

Conference paper

Johannisson W, Nguyen S, Lindbergh G, Zenkert D, Greenhalgh E, Shaffer M, Kucernak Aet al., 2020, A residual performance methodology to evaluate multifunctional systems, Multifunctional Materials, Vol: 3, ISSN: 2399-7532

The development of multifunctional materials and structures is receiving increasing interest for many applications and industries; it is a promising way to increase system-wide efficiency and improve the ability to meet environmental targets. However, quantifying the advantages of a multifunctional solution over monofunctional systems can be challenging. One approach is to calculate a reduction in mass, volume or other penalty function. Another approach is to use a multifunctional efficiency metric. However, either approach can lead to results that are unfamiliar or difficult to interpret and implement for an audience without a multifunctional materials or structures background.Instead, we introduce a comparative metric for multifunctional materials that correlates with familiar design parameters for monofunctional materials. This metric allows the potential benefits of the multifunctional system to be understood easily without needing a holistic viewpoint. The analysis is applied to two different examples of multifunctional systems; a structural battery and a structural supercapacitor, demonstrating the methodology and its potential for state-of-the-art structural power materials to offer a weight saving over conventional systems. This metric offers a new way to communicate research on structural power which could help identify and prioritise future research.

Journal article

Valkova M, Anthony DB, Kucernak ARJ, Shaffer MSP, Greenhalgh ESet al., 2020, Predicting the compaction of hybrid multilayer woven composite reinforcement stacks, Composites Part A: Applied Science and Manufacturing, Vol: 133, ISSN: 1359-835X

A meso-scale finite element modelling strategy was developed to investigate the effect of hybridisation on the compaction response of multilayer stacks combining glass and carbon dry woven fabrics. It is expected that the electrochemical-mechanical properties of emerging multifunctional hybrid composites are strongly dictated by the morphology of the compacted reinforcements, yet no investigations into their compressibility have been reported. Model predictions were evaluated against compressibility measurements for monolithic and hybrid fabric stacks. The ply offset had a major influence on the predicted internal morphologies and fibre content, contributing to experimental variability thereof. Optical microscopy and micro X-ray computed tomography imaging indicated greater likelihood of intermediate ply offsets in physical specimens, over limit case model idealisations. Compressibility was slightly reduced in the hybrid multilayer stacks studied in this work. The model outputs presented are being used to analyse the electrochemical-mechanical response of hybrid woven structural power composites.

Journal article

Razavi S, 2020, The development of a smart piezo-braid for composite applications

Thesis dissertation

Mohsin MAA, Iannucci L, Greenhalgh E, 2020, Numerical and experimental analysis of high-velocity impact behaviour of carbon fibre reinforced thermoplastic composites

The low, medium and high-velocity impact resistance of fibre reinforced thermoplastic and thermosetting composites have continually attracted interest in automotive, aerospace and military applications. This research aims to characterise the high-velocity impact (HVI) response of a carbon fibre reinforced thermoplastic (CFRTP) composite system which is comprised of non-crimp fabric (NCF) biaxial 0/90 T700 carbon pre-impregnated with polyphenylene sulphide (PPS) thermoplastic (TP) veils. The raw materials were provided by THERMOCOMP [1] and the composite panels were manufactured using a 40-tonne hydraulic laboratory press via thermoforming process. The HVI tests were performed with velocities ranging from 130 to 250m/s. The projectile used is a 16mm diameter spherical stainless steel with a mass of 16.5 ± 0.5g. The entry and exit velocities were measured to determine the V50 and the energy absorbed in cases where perforation occurs. The experimental procedure was then numerically simulated using a finite element (FE) solver LS-DYNA®. The numerical model is then validated and compared against the experimental gatherings with respect to the exit velocities and damage mechanism.

Conference paper

Canturri C, Greenhalgh ES, Asp LE, Pinho STet al., 2019, Fractographic study to characterise the interaction between intralaminar and interlaminar fracture from embedded defects under compression loading, Composites Part A: Applied Science and Manufacturing, Vol: 125, ISSN: 1359-835X

This paper describes the fractographic observations from the study of embedded defects subject to compression. The fractographic observations aim to characterise the interaction between intralaminar and interlaminar fracture and to understand their role in the delamination growth and the delamination migration. The influence of the stacking sequence orientation on the damage modes is studied in eight different configurations. A detailed fractographic study led to the identification of the different failure modes and failure sequence. It was also possible to establish the stacking sequences more prone to delamination migration and the failure modes more critical for damage tolerance.

Journal article

Nguyen S, Anthony DB, Qian H, Yue C, Singh A, Bismarck A, Shaffer MSP, Greenhalgh ESet al., 2019, Mechanical and physical performance of carbon aerogel reinforced carbon fibre hierarchical composites, Composites Science and Technology, Vol: 182, ISSN: 0266-3538

Carbon aerogel (CAG) is a potential hierarchical reinforcement to improve the matrix-dominated mechanical properties of continuous carbon fibre reinforced polymer (CFRP) composites in both multifunctional and purely structural applications. When using CAG to reinforce a polyethylene glycol diglycidyl ether (PEGDGE) matrix, the interlaminar shear strength, compressive modulus and strength increased approximately four-fold, whilst the out-of-plane electrical conductivity increased by 118%. These mechanical and electrical performance enhancements significantly improve the multifunctional efficiency of composite structural supercapacitors, which can offer weight savings in transport and other applications. However, CAG also has the potential to reinforce conventional continuous CF composites in purely structural contexts. Here, CAG reinforcement of structural epoxy resin composites marginally increased compressive (1.4%) and tensile (2.7%) moduli respectively, but considerably reduced compressive, tensile and interlaminar shear strengths. Fractographic analysis shows that the reduced performance can be attributed to poor interfacial adhesion; in the future, alternative processing routes may resolve these issues to achieve advances in both moduli and strengths over conventional structural CFRPs.

Journal article

Anthony D, Nguyen S, Senokos E, Bismarck A, Kucernak A, Greenhalgh E, Shaffer Met al., 2019, Hierarchical carbon aerogel modified carbon fiber composites for structural power applications, 22nd International Conference on Composite Materials 2019 (ICCM22), Publisher: Engineers Australia, Pages: 1-7

The desire to reduce overall weight in devices is a key driver for perpetual material development; the ability to combine composites with energy storage functions/capabilities which simultaneously provide structural integrity has the potential to supersede monofunctional components. To achieve this ambition, the multifunctional structure must perform both mechanical and energy storage functions sufficiently, but often there is a trade off in performance which is a significant challenge to overcome. Carbon aerogels have been shown to contribute positively to (electro-chemical double layer) capacitive performance due to an increased surface area in multifunctional carbon fiber based composite electrodes, but have also been shown to reduce mechanical properties; the addition of nanoscale reinforcers, such as carbon nanotubes, graphene or alike, with their superlative electrical and mechanical properties are proposed to address these concerns and create a truly hierarchical structure suitable for structural power applications.

Conference paper

Lee C, Panesar A, Greenhalgh E, 2019, Design of optimised multi-scale structures for multifunctional composites, International conference on composite materials (ICCM-22), Publisher: Engineers Australia, Pages: 1-8

The multi-scale structures are commonly found in nature, such as plants and bones. Such multi-scale structurescan be divided into macro-scale, micro-scale and further sub-scale structures. In this study, we aim to designoptimised two-scale structures for multifunctional composites, specifically by enhancing the structural stiffnessand the ionic conductivity simultaneously. To tackle this problem, a novel strategy for achieving optimised multiscale structures is presented. A database of optimised micro-scale structures and simple placement criterion forthe micro-scale structure were applied. We demonstrate the efficiency of our strategy by designing, optimisingand evaluating two-scale structures composed of macro-and micro-scales. The advantage of our strategy foroptimised multi-scale structures is presented and discussed by comparing the structural stiffness and the ionicconductivity of several two-scale structures composed of different microstructures such as the solid-void, uniformand varied microstructures.

Conference paper

Lee C, Greenhalgh E, Panesar A, 2019, Optimised laminated composite ship-structures against wave impact for enhanced dynamic stiffness, Inter-noise 2019, Publisher: International Institute of Noise Control Engineering (I-INCE), ISSN: 0105-175X

Fibre-reinforced laminated composites are increasingly being utilised in marine and offshore structures due to their superior stiffness and strength to weight ratios, such as resistance to corrosion and enhanced toughness over conventional materials like steel and aluminium. A potential application of composites is in the design of wave-breakers on ship structures. These structures absorb the impact energies from a wave slam to ensure vessel serviceability and safety. The inherent anisotropy of composites and the associated dynamic loading characteristics, make the design process for such a structure very challenging. There are limited studies looking at the design optimisation of composite structures under wave impact loads. In particular, dynamic optimisation based on modal vibration characteristics has not been sufficiently studied. In this study, we have optimised a composite wave-breaker to improve the specific dynamic stiffness based on modal vibration characteristics. To tackle this problem, a multi-level optimisation procedure has been adopted; firstly, the minimum thickness of the composite plate has been determined to avoid delamination; subsequently, the stacking sequence has been identified using lamination parameters along with local thickness variation. Importantly, the optimal arrangement of damping materials (sandwiched between plies) has also been investigated to further enhance the dynamic energy dissipation performance.

Conference paper

Nguyen S, Corey M, Chan W, Greenhalgh ES, Graham JMRet al., 2019, Experimental determination of the aerodynamic coefficients of spinning bodies, The Aeronautical Journal, Vol: 123, Pages: 678-705, ISSN: 0001-9240

To accurately predict the probabilities of impact damage to aircraft from runway debris, it is important to understand and quantify the aerodynamic forces that contribute to runway debris lofting. These lift and drag forces were therefore measured in experiments with various bodies spun over a range of angular velocities and Reynolds numbers. For a smooth sphere, the Magnus effect was observed for ratios of spin speed to flow speed between 0.3 and 0.4, but a negative Magnus force was observed at high Reynolds numbers as a transitional boundary layer region was approached. Similar relationships between lift and spin rate were found for both cube- and cylinder-shaped test objects, particularly with a ratio of spin speed to flow speed above 0.3, which suggested comparable separation patterns between rapidly spinning cubes and cylinders. A tumbling smooth ellipsoid had aerodynamic characteristics similar to that of a smooth sphere at a high spin rate. Surface roughness in the form of attached sandpaper increased the average lift on the cylinder by 24%, and approximately doubled the lift acting on the ellipsoid in both rolling and tumbling configurations.

Journal article

Zainol Abidin MS, Herceg T, Greenhalgh ES, Shaffer M, Bismarck Aet al., 2019, Enhanced fracture toughness of hierarchical carbon nanotube reinforced carbon fibre epoxy composites with engineered matrix microstructure, Composites Science and Technology, Vol: 170, Pages: 85-92, ISSN: 0266-3538

Fibre reinforced hierarchical composites further reinforced with up to 25 wt.% of carbon nanotubes (CNTs) were manufactured using a wet powder impregnation route. Microstructural heterogeneity in the matrix of these laminates was engineered during wet powder impregnation to produce CNTs rich regions with spatial separation. The Mode I fracture toughness of these heterogeneous hierarchical composites increased by 41% and 26% compared to that of baseline carbon fibre epoxy composites and hierarchical composites with homogeneously distributed CNTs throughout the matrix with similar CNT content, respectively. Increased crack path tortuosity was observed to contribute to this increase in fracture toughness. The interlaminar shear strength was unaffected by the matrix microstructural heterogeneity.

Journal article

Mohsin M, Iannucci L, Greenhalgh E, 2019, Fibre-volume-fraction measurement of carbon fibre reinforced thermoplastic composites using thermogravimetric analysis, Heliyon, Vol: 5, ISSN: 2405-8440

The fibre-volume-fraction (FVF) measurement of fibre-reinforced polymers (FRPs) is crucial in understanding and characterising their mechanical performance. To date, there has not been a standardised, labour-efficient method in determining the FVF of a non-crimp fabric (NCF) carbon reinforced thermoplastic composites (CFRTPs). An alternative method such as thermogravimetric analysis (TGA) has merely been commonly used for carbon-fibre reinforced thermosets (CFRTSs) and glass-fibre reinforced thermosets (GFRTSs). Therefore, this paper reports a range of macro TGA measurements of the constituent materials of two NCF CFRTPs; (i) T700 carbon/polyamide6.6 (PA6.6) and (ii) T700 carbon/polyphenylene sulphide (PPS). The TGA measurements were performed using two different purge gases (air and nitrogen) and the mass degradation with respect to time, temperature and atmospheres were recorded and discussed. Additionally, fractographic analysis on the fibres was carried out to scrutinise and further discuss the findings following the TGA. It was concluded that TGA provided a suitable and reliable alternative method to measure the FVF of CFRTPs.

Journal article

Katafiasz TJ, Iannucci L, Greenhalgh E, 2019, Development of a novel compact tension specimen to mitigate premature compression and buckling failure modes within fibre hybrid epoxy composites, Composite Structures, Vol: 207, Pages: 93-107, ISSN: 1879-1085

A Notched Curved Compact Tension (NCCT) and Extended Notched Curved Compact Tension (ENCCT) specimen geometry are presented for the measurement of translaminar critical strain energy release rates in composite laminates with low compressive to tensile strengths. Premature compressive and buckling failure occurred when a conventional Compact Tension (CT) specimen geometry (similar to ASTM E399 [1]) was utilised for monolithic Non-Crimp Fabric (NCF) S2-Glass / MTM57 epoxy and an interlayer fibre hybrid T700 carbon spread tow / NCF S2-glass epoxy composite. The NCCT and ENCCT specimen design methodology and manufacturing routes are presented where premature compressive failure was mitigated through a curvature at the rear of the profile and the introduction of a through-thickness groove that had been pre-cured along the crack growth region. The latter ensured that buckling was eliminated, whilst stable crack growth was achieved. The development involved FE model material validation and optimisation for the novel specimen design. Experimental tests presented both interlayer and intralayer fibre hybrid composites with good repeatability and low scatter within the results.

Journal article

Lee C, Greenhalgh ES, Panesar A, 2019, Optimised laminated composite ship-structures against wave impact for enhanced dynamic stiffness

Fibre-reinforced laminated composites are increasingly being utilised in marine and offshore structures due to their superior stiffness and strength to weight ratios, such as resistance to corrosion and enhanced toughness over conventional materials like steel and aluminium. A potential application of composites is in the design of wave-breakers on ship structures. These structures absorb the impact energies from a wave slam to ensure vessel serviceability and safety. The inherent anisotropy of composites and the associated dynamic loading characteristics, make the design process for such a structure very challenging. There are limited studies looking at the design optimisation of composite structures under wave impact loads. In particular, dynamic optimisation based on modal vibration characteristics has not been sufficiently studied. In this study, we have optimised a composite wave-breaker to improve the specific dynamic stiffness based on modal vibration characteristics. To tackle this problem, a multi-level optimisation procedure has been adopted; firstly, the minimum thickness of the composite plate has been determined to avoid delamination; subsequently, the stacking sequence has been identified using lamination parameters along with local thickness variation. Importantly, the optimal arrangement of damping materials (sandwiched between plies) has also been investigated to further enhance the dynamic energy dissipation performance.

Conference paper

Lee C, Greenhalgh ES, Panesar A, 2019, Optimised laminated composite ship-structures against wave impact for enhanced dynamic stiffness

© INTER-NOISE 2019 MADRID - 48th International Congress and Exhibition on Noise Control Engineering. All Rights Reserved. Fibre-reinforced laminated composites are increasingly being utilised in marine and offshore structures due to their superior stiffness and strength to weight ratios, such as resistance to corrosion and enhanced toughness over conventional materials like steel and aluminium. A potential application of composites is in the design of wave-breakers on ship structures. These structures absorb the impact energies from a wave slam to ensure vessel serviceability and safety. The inherent anisotropy of composites and the associated dynamic loading characteristics, make the design process for such a structure very challenging. There are limited studies looking at the design optimisation of composite structures under wave impact loads. In particular, dynamic optimisation based on modal vibration characteristics has not been sufficiently studied. In this study, we have optimised a composite wave-breaker to improve the specific dynamic stiffness based on modal vibration characteristics. To tackle this problem, a multi-level optimisation procedure has been adopted; firstly, the minimum thickness of the composite plate has been determined to avoid delamination; subsequently, the stacking sequence has been identified using lamination parameters along with local thickness variation. Importantly, the optimal arrangement of damping materials (sandwiched between plies) has also been investigated to further enhance the dynamic energy dissipation performance.

Conference paper

Syed Abdullah SIB, Iannucci L, Greenhalgh E, 2018, On the translaminar fracture toughness of vectran/epoxy composite material, Composite Structures, Vol: 202, Pages: 566-577, ISSN: 1879-1085

The mode I fracture toughness associated with fibre tensile failure was investigated for a Vectran/MTM57 composite system. A modified compact tension specimen was designed and manufactured to mitigate compressive and buckling failure due to the low compressive properties which are an inherent characteristic of Vectran fibres. On average, the mode I translaminar fracture toughness for Vectran/MTM57 was found to be approximately 130–145 kJ/m2 for initiation and 250–260 kJ/m2 for propagation. In contrast with other composite systems such as carbon and glass fibre, the fracture toughness of Vectran/MTM57 was found to be relatively higher, with up to 48.26% and 95.27% for initiation and propagation, respectively for some carbon fibre composite system; 9.93% and 68.6% for initiation and propagation, respectively for S2-Glass/epoxy system.

Journal article

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