Publications
236 results found
Valkova M, Anthony DB, Kucernak ARJ, et al., 2022, Predicting the mechanical behaviour of structural supercapacitor composites, Composites Part A: Applied Science and Manufacturing, Vol: 156, ISSN: 1359-835X
Multifunctional structural power composites may transform transport electrification, and other applications, but require performance and reliability improvements. Computational modelling has the potential to accelerate their development and deployment. This work addresses the lack of predictive models for the mechanical behaviour of structural supercapacitor composites exploiting carbon aerogel-modified carbon fabric electrodes. The elastic behaviour was investigated using finite element analysis of quasi-meso-scale periodic unit cell models, considering the effects of constituent properties, defects, stacking geometry, and boundary conditions. Nanoindentation was used to evaluate the Young’s modulus of carbon aerogel. Parametric modelling demonstrated a strong influence of the ply offset and matrix materials on the composite elastic properties. The initial numerical results overpredicted the actual performance measured from tensile and in-plane shear experiments in the literature. Optical, scanning electron and micro X-ray imaging revealed extensive pre-cracking and voidage in the physical laminates. Additional computational investigations showed that the pre-cracks were associated with a degradation of shear stiffness. The remaining performance gap was attributed to voidage. The present study highlights that challenges for mechanical performance and its prediction stem from the presence of processing defects and a lack of in-situ material data. Nevertheless, the models identify the potential of hierarchical laminates containing aerogels to generate sizable performance improvements, both in multifunctional and purely structural contexts.
Pernice MF, Qi G, Senokos E, et al., 2022, Mechanical, electrochemical and multifunctional performance of a CFRP/carbon aerogel structural supercapacitor and its corresponding monofunctional equivalents, Multifunctional Material, Vol: 5
Anthony DB, De Luca HG, Almousa H, et al., 2022, Carbon Nanotube-grafted Carbon Fiber Production: A Scaling Challenge, Fiber Society 2022 Spring Conference - Fibers for a Greener Society: From Fundamentals to Advanced Applications, Pages: 51-51
Katafiasz TJ, Greenhalgh ES, 2022, FRACTOGRAPHY OF POLYMER COMPOSITES: FUTURE ADVANCES, Pages: 9-16
Fractography is a useful research tool which enables engineers to bridge the gap between numerical modelling and experimental testing, support material design development, and aid in the failure investigation of in-service (and laboratory-based) failures. This paper presents the current issues and direction of research for the fractography of polymer composites and highlights the future challenges. These include: fretting failures between delaminated neighbouring plies, gleaning environmental effects (i.e. the influence of moisture and/or temperature on fracture morphology), and the sequencing of physically isolated failures. The latter is addressed by the proposed new methodology in which fractography and numerical modelling are synergistically coupled. This methodology is becoming increasingly important across a range of industries as the uptake of composites becomes wider.
Abdullah SIBS, Iannucci L, Greenhalgh ES, et al., 2022, The delamination behaviour of Vectran/Epoxy composites having a novel Non-Crimp Fabric architecture, COMPOSITES PART B-ENGINEERING, Vol: 228, ISSN: 1359-8368
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- Citations: 3
Fujita Y, Noda S, Takahashi J, et al., 2022, ANALYSING AND PREDICTING FAILURE OF INJECTION-MOULDED SHORT-FIBRE COMPOSITE COMPONENTS, Pages: 312-317
Injection-moulded short-fibre composites are lightweight materials suitable for highvolume applications; however, current simulation methods for these materials cannot yet predict failure accurately. This work proposes a methodology to predict failure of injection-moulded short-glass-fibre reinforced PA66 composite components, based on experimentally measured properties. The material's fracture toughness was characterized for different fibre orientations, and these values were used as the input for cohesive zone modelling in Finite Element analyses of the components, coupled with simulations of the injection-moulding process. The coupled process/structural simulations using cohesive zone modelling presented excellent agreement with the experimental data of the component tests, highlighting the importance of accounting for the finite fracture toughness of the material to accurately predict the ultimate failure of injection-moulded short-fibre reinforced PA66 composite components.
Yu B, Katafiasz TJ, Nguyen S, et 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.
Mohsin M, Iannucci L, Greenhalgh E, 2021, Experimental and numerical analysis of low-velocity impact of carbon fibre based non-crimp fabric reinforced thermoplastic composites, Polymers, Vol: 13, Pages: 1-22, ISSN: 2073-4360
There has been a lot of interest in understanding the low-velocity impact (LVI) response of thermoplastic composites. However, little research has focussed on studying the impact behaviour of non-crimp fabric (NCF)-based fibre reinforced thermoplastic composites. The purpose of this study was to evaluate the LVI responses of two types of non-crimp fabric (NCF) carbon fibre reinforced thermoplastic laminated composites that have been considered attractive in the automotive and aerospace industry: (i) T700/polyamide 6.6 (PA6.6) and (ii) T700/polyphenylene sulphide (PPS). Each carbon/thermoplastic type was impacted at three different energy levels (40, 100 and 160 J), which were determined to achieve three degrees of penetrability, i.e., no penetration, partial penetration and full penetration, respectively. Two distinct non-destructive evaluation (NDE) techniques ((i) ultrasonic C-scanning and (ii) X-ray tomography) were used to assess the extent of damage after impact. The laminated composite plates were subjected to an out-of-plane, localised impact using an INSTRON® drop-weight tower with a hemispherical impactor measuring 16 mm in diameter. The time histories of force, deflection and velocity are reported and discussed. A nonlinear finite element model of the LVI phenomenon was developed using a finite element (FE) solver LS-DYNA® and validated against the experimental observations. The extent of damage observed and level of impact energy absorption calculated on both the experiment and FE analysis are compared and discussed.
Karadotcheva E, Nguyen SN, Greenhalgh ES, et al., 2021, Structural power performance targets for future electric aircraft, Energies, Vol: 14, ISSN: 1996-1073
The development of commercial aviation is being driven by the need to improve efficiency and thereby lower emissions. All-electric aircraft present a route to eliminating direct fuel burning emissions, but their development is stifled by the limitations of current battery energy and power densities. Multifunctional structural power composites, which combine load-bearing and energy-storing functions, offer an alternative to higher-energy-density batteries and will potentially enable lighter and safer electric aircraft. This study investigated the feasibility of integrating structural power composites into future electric aircraft and assessed the impact on emissions. Using the Airbus A320 as a platform, three different electric aircraft configurations were designed conceptually, incorporating structural power composites, slender wings and distributed propulsion. The specific energy and power required for the structural power composites were estimated by determining the aircraft mission performance requirements and weight. Compared to a conventional A320, a parallel hybrid-electric A320 with structural power composites >200 Wh/kg could potentially increase fuel efficiency by 15% for a 1500 km mission. For an all-electric A320, structural power composites >400 Wh/kg could halve the specific energy or mass of batteries needed to power a 1000 km flight.
Qi G, Nguyen S, Anthony DB, et al., 2021, The influence of fabrication parameters on the electrochemical performance of multifunctional structural supercapacitors, Multifunctional Materials, Vol: 4, ISSN: 2399-7532
Multifunctional structural supercapacitors based on carbon fibre electrodes (CF) and structural electrolytes (SEs) can realise multifunctionality by simultaneously bearing load and providing electrochemical energy storage. Structural supercapacitor constituents (i.e. electrodes and electrolytes) have undergone significant development to enhance their electrochemical and mechanical properties. However, the fabrication of fully functional devices presents a number of practical challenges to achieve optimal multifunctional properties, particularly those associated with assembly and lamination. This work investigated the effect of separator selection and processing parameters on the electrochemical performance of structural supercapacitors, as well as evaluating the repeatability of the SE filming process. Two layers of glass fibre fabrics were the most effective separator for preventing short-circuiting of the structural supercapacitors. The weight fraction of the SE matrix had a significant effect on the capacitance, energy and power of the structural supercapacitors. By addressing such fabrication challenges, high performance structural supercapacitors can be manufactured with greater reproducibility and at larger scales such that they are suitable for integration in industrial applications.
Abdullah SIBS, Iannucci L, Greenhalgh ES, et al., 2021, A Plane-Stress Damage Model for Vectran Laminated Composite, APPLIED COMPOSITE MATERIALS, Vol: 28, Pages: 1255-1276, ISSN: 0929-189X
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- Citations: 3
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.
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.
Abdullah SIBS, Iannucci L, Greenhalgh ES, et al., 2021, The impact performance of Vectran/Epoxy composite laminates with a novel non-crimp fabric architecture, COMPOSITE STRUCTURES, Vol: 265, ISSN: 0263-8223
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- Citations: 5
Nguyen S, Millereux A, Pouyat A, et al., 2021, Conceptual multifunctional design, feasibility and requirements for structural power in aircraft cabins, Journal of Aircraft: devoted to aeronautical science and technology, Vol: 58, Pages: 677-687, 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.
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.
Katafiasz T, Greenhalgh ES, Allegri G, et 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.
Lee C, Greenhalgh E, Shaffer M, et 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.
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.
De Luca H, Anthony D, Greenhalgh E, et 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.
Senokos E, Anthony D, Nguyen S, et 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.
Nguyen S, Millereux A, Pouyat A, et 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.
Johannisson W, Nguyen S, Lindbergh G, et 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.
Valkova M, Anthony DB, Kucernak ARJ, et 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.
Razavi S, 2020, The development of a smart piezo-braid for composite applications
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.
Canturri C, Greenhalgh ES, Asp LE, et 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.
Nguyen S, Anthony DB, Qian H, et 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.
Anthony D, Nguyen S, Senokos E, et 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.
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.
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