Publications
39 results found
Irven G, Carolan D, Fergusson A, et al., 2023, Digital image correlation of cross-ply laminates in tension to reveal microcracking, Composite Structures, Vol: 319, Pages: 1-12, ISSN: 0263-8223
The use of Digital Image Correlation (DIC) to reveal microstructural damage in cross-ply laminates was investigated. Matrix toughness plays a key role in governing microcracking at the tow level in near-surface plies. Experiments revealed that using a tough epoxy polymer as the matrix of the laminate resulted in increased laminate moduli in the principal directions. DIC provides insights into cross-ply laminate failure; the increase in modulus is attributed to microcrack formation in transverse plies. Early onset of matrix cracking around the tows is revealed by variations in the strain along the gauge length. The use of a tough epoxy polymer delays the load at which this cracking occurs. When an untoughened epoxy polymer is used as the matrix, microcracking can be observed at the beginning of the test, suggesting processing induced damage. The use of toughened polymers as the matrix of composite laminates is recommended to mitigate against this.
Irven G, Whitehouse A, Carolan D, et al., 2023, Toughening of face-sheet core bonds in sandwich structures, Engineering Fracture Mechanics, Vol: 290, Pages: 1-14, ISSN: 0013-7944
Methods of improving the toughness of the bond between a foam core and a carbon fibre face-sheet in a sandwich structure were investigated. The Single Cantilever Beam (SCB) on a travelling platform was identified as an appropriate mode-I dominant test-method. The introduction of machined grooves in the foam resulted in a 50% improvement in the measured toughness of the face-sheet-core bond. Toughening of the face-sheets via core–shell rubber particles resulted in a change in fracture locus away from the interface and into the foam. The use of aramid fibre-reinforced foam as the core of the sandwich was also found to improve the interface bond toughness by up to 50%. The fibre-reinforced foams promoted the emergence of R-curve behaviour as the crack propagated.
Irven G, Carolan D, Fergusson A, et al., 2023, Fracture performance of fibre-reinforced epoxy foam, Composites Part B: Engineering, Vol: 250, Pages: 1-12, ISSN: 1359-8368
Low density aramid and carbon fibre-reinforced epoxy foam has been synthesised with the aim of improving mechanical properties, principally fracture performance. The foam properties measured were fracture energy, compressive strength, and density. The influence of fibre type, loading, and length was investigated. In addition, composite face-sheet bond tests were performed to ascertain how effective toughness transferred from individual component to composite structure. In general, the addition of fibres improved the mechanical performance of reinforced samples compared to the control foam. Increases in compressive strength were moderate whilst fracture energy was increased by up to 107% from 124 J/m2 to 256 J/m2 by the addition of 0.75 mm aramid fibres. Increased fracture energy of the foam and the presence of fibres on the foam surface, caused an increase in face-sheet bond propagation fracture toughness of 50% from 277 J/m2 to 416 J/m2.
Irven G, Duncan A, Whitehouse A, et al., 2021, Impact response of composite sandwich structures with toughened matrices, Materials and Design, Vol: 203, ISSN: 0264-1275
The mechanisms of failure of a composite sandwich structure subjected to a projectile impact have been investigated. The results reveal the complex interplay between the various damage dissipation mechanisms. The effects of modifying the matrix of the skins with polysiloxane core–shell rubber (CSR) nanoparticles and silica nanoparticles were investigated. Single cantilever beam specimens were tested to evaluate skin-core debonding. The addition of CSR nanoparticles to the matrix beyond 3 wt% causes a change in failure mechanism from sub-interface foam failure to interfacial failure when 6 and 9 wt% CSR are added. The sandwich structures were impacted with an aluminium projectile at 130 m/s. High speed cameras were used to obtain 3D digital image correlation of the back-face. Sectioning and imaging of the panels revealed damage in the form of front skin perforation and delamination, crushing and fracture of the core and back-face skin-core debonding. The impacted specimens also exhibited a transition in failure mechanism relating to rear face skin-core debonding between 3 and 6 wt%. Panels containing low amounts of CSR resulted in increased core cracking, while beyond the transition point, widespread rear face skin-core debonding was observed. At 3 wt% CSR, optimum back face deflection is achieved, and lower front skin delamination is experienced.
He S, Carolan D, Fergusson A, et al., 2020, Mechanical and fracture properties of epoxy syntactic foams modified with milled carbon fibre
© CCM 2020 - 18th European Conference on Composite Materials. All rights reserved. Syntactic foams are lightweight but brittle materials typically used as the core for sandwich composite panels. Foams comprising of ∼60 vol% hollow glass microspheres (GMS) in an epoxy matrix were modified by the addition of milled carbon fibre (MCF). Weight ratios of up to 30% MCF:GMS were used. The tensile modulus of the foams increased from 3.36 GPa up to 4.82 GPa with the addition of 30% weight ratio of MCF. The tensile failure strength of the syntactic foam decreased with low loadings of MCF, which is attributed to low load transfer capacity among the fibres due to poor fibre population. The tensile failure strength recovers when more MCF particles are added. The fracture energy of the syntactic foam showed an increase of 217%, from 182 J/m2 to 396 J/m2, due to the addition of 30% weight ratio of MCF. Toughening mechanisms were identified as crack deflection, debonding and subsequent plastic void growth, and fibre pull-out.
He S, Carolan D, Fergusson A, et al., 2020, Mechanical and fracture properties of epoxy syntactic foams modified with milled carbon fibre
Syntactic foams are lightweight but brittle materials typically used as the core for sandwich composite panels. Foams comprising of ∼60 vol% hollow glass microspheres (GMS) in an epoxy matrix were modified by the addition of milled carbon fibre (MCF). Weight ratios of up to 30% MCF:GMS were used. The tensile modulus of the foams increased from 3.36 GPa up to 4.82 GPa with the addition of 30% weight ratio of MCF. The tensile failure strength of the syntactic foam decreased with low loadings of MCF, which is attributed to low load transfer capacity among the fibres due to poor fibre population. The tensile failure strength recovers when more MCF particles are added. The fracture energy of the syntactic foam showed an increase of 217%, from 182 J/m2 to 396 J/m2, due to the addition of 30% weight ratio of MCF. Toughening mechanisms were identified as crack deflection, debonding and subsequent plastic void growth, and fibre pull-out.
He S, Carolan D, Fergusson A, et al., 2020, Mechanical and fracture properties of epoxy syntactic foams modified with milled carbon fibre
© CCM 2020 - 18th European Conference on Composite Materials. All rights reserved. Syntactic foams are lightweight but brittle materials typically used as the core for sandwich composite panels. Foams comprising of ∼60 vol% hollow glass microspheres (GMS) in an epoxy matrix were modified by the addition of milled carbon fibre (MCF). Weight ratios of up to 30% MCF:GMS were used. The tensile modulus of the foams increased from 3.36 GPa up to 4.82 GPa with the addition of 30% weight ratio of MCF. The tensile failure strength of the syntactic foam decreased with low loadings of MCF, which is attributed to low load transfer capacity among the fibres due to poor fibre population. The tensile failure strength recovers when more MCF particles are added. The fracture energy of the syntactic foam showed an increase of 217%, from 182 J/m2 to 396 J/m2, due to the addition of 30% weight ratio of MCF. Toughening mechanisms were identified as crack deflection, debonding and subsequent plastic void growth, and fibre pull-out.
Tsai SN, Carolan D, Sprenger S, et al., 2019, Fracture and fatigue behaviour of carbon fibre composites with nanoparticle-sized fibres, Composite Structures, Vol: 217, Pages: 143-149, ISSN: 0263-8223
Fibre composites with thermoset polymer matrices are widely used. However, thermosets are very brittle, which can limit the applications of fibre composites. In this work, silica nanoparticles (SNPs) were used to modify two fibre sizings to improve the toughness of carbon fibre composites. Mode I interlaminar fracture and fatigue crack growth tests were conducted on the composites made using the silica nanoparticle-sized fibres. There was no significant change in the fatigue crack growth rate with the addition of SNPs. However, the addition of SNPs to either sizing increased the composite toughness. The fracture energy was significantly increased from 166 J/m 2 to 220 J/m 2 (increased by 33%) with only 0.89 wt% on fibre weight of SNPs. This is significantly more efficient than adding SNPs into the matrix, which can require addition of up to 20 wt% of SNPs [1], to achieve the same improvement in toughness.
He S, Carolan D, Fergusson A, et al., 2019, Toughening epoxy syntactic foams with milled carbon fibres: mechanical properties and toughening mechanisms, Materials and Design, Vol: 169, Pages: 1-15, ISSN: 0264-1275
Syntactic foams comprising hollow glass microspheres (GMS) in an epoxy matrix are critical materials for lightweight structures, being extensively used in marine and aerospace as cores for composite sandwich panels. They are buoyant and crush resistant, but their use is limited by their brittleness. Milled carbon fibres (MCF) were used to increase toughness, by introducing energy absorption mechanisms, to foams comprising ∼60 vol% GMS. Weight ratios of up to 40% MCF:GMS were used. The tensile modulus of the foams increased from 3.36 GPa to 5.41 GPa with the addition of 40% weight ratio of MCF. The tensile strength of the syntactic foam decreased with low loadings of MCF, but then recovers when more MCF particles are added, and the mechanisms responsible are explained for the first time. The fracture energy of the syntactic foam increased by 183%, from 182 J/m2 to 516 J/m2, due to the addition of 40% weight ratio of MCF. Toughening mechanisms were identified as crack deflection, debonding and subsequent plastic void growth, and fibre pull-out. Thus, the simple and cheap addition of MCF greatly increases the toughness of the syntactic foams, enabling lighter or more damage-resistant structures to be produced.
He S, Carolan D, Fergusson A, et al., 2019, Toughening epoxy syntactic foams with milled carbon fibres: Mechanical properties and toughening mechanisms
Syntactic foams comprising hollow glass microspheres (GMS) in an epoxy matrix are critical for lightweight structures, being extensively used in marine and aerospace as cores for composite sandwich panels. They are buoyant and crush resistant, but their use is limited by their brittleness. Milled carbon fibres (MCF) were used to increase toughness, by introducing energy absorption mechanisms, to foams comprising ∼60 vol% GMS. Weight ratios of up to 40% MCF:GMS were used. The tensile modulus of the foams increased from 3.36 GPa to 5.41 GPa with the addition of 40% weight ratio of MCF. The tensile strength of the syntactic foam decreased then increase when more MCF particles are added, and the mechanisms responsible are explained for the first time. The fracture energy of the syntactic foam increased by 183%, from 182 J/m2 to 516 J/m2, due to the addition of 40% weight ratio of MCF. Toughening mechanisms were identified as crack deflection, debonding and subsequent plastic void growth, and fibre pull-out. Thus, the simple and cheap addition of MCF greatly increases the toughness of the syntactic foams, enabling lighter or more damage-resistant structures.
Cattaneo L, Carolan D, Incerti D, et al., 2019, Experimental study of the mechanical and flammability behaviour of silica and rubber nanocomposites
In the current work, an experimental study of the mechanical and flammability behaviour of silica and rubber nanocomposites was conducted. Single edge notched bend tests were performed to evaluate the fracture energy of the polymers. It was found that the addition of 24 wt.% of core shell rubber (CSR) increased the toughness from 0.19 ± 0.02 kJ/m2 to 5.44 ± 0.27 kJ/m2. Moreover, flammability testing using a cone heater showed that the time to ignition increases with silica content. This is thought to be primarily caused by an increase in thermal conductivity (or diffusivity) and the formation of a char mass barrier which hinders the flow of pyrolysis gases on the surface of the sample. Hybrid compounds containing both CSR and silica have also been tested and present relatively good mechanical performance as well as reduced flammability due to the presence of nano-silica, with a highest time to ignition of 111 ± 3 s. Poor toughness transfer to CFRP for the hybrid formulations was found, mainly due to the fracture process zone being constrained by inter-laminar spacing. Time to ignition in CFRPs increased compared to the bulk polymer and less damage on the degradation surface was recorded due to the presence of the carbon. The results demonstrate the possibility to manufacture composite materials that are resistant to fire, but still possess outstanding mechanical properties.
Selimov A, Jahan SA, Barker E, et al., 2018, Silane functionalization effects on dispersion of alumina nanoparticles in hybrid carbon fiber composites, APPLIED OPTICS, Vol: 57, Pages: 6671-6678, ISSN: 1559-128X
Taylor AC, Selimov A, Jahan SA, et al., 2018, Silane functionalization effects on dispersion of alumina nanoparticles in hybrid carbon fiber composites revealed through photo-luminescence spectroscopy, Applied Optics, Vol: 57, Pages: 6671-6678, ISSN: 1559-128X
Hybrid carbon fiber reinforced polymer composites are a new breed of materials currently being explored and characterized for next-generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties—fracture toughness, for example—and stress-sensing capabilities can be achieved. However, problems with manufacturing can arise resulting from the inherent variability of the manufacturing techniques along with the tendency for the nanoparticles to agglomerate. Photoluminescence spectroscopy is used to investigate the effects of adjustments to manufacturing processes and silane functionalization on particle dispersion and sample consistency between samples of the same type. This work finds that application of surface treatments on the nanoparticles improved their dispersion, with the reactive treatment providing for the most consistency among samples. Improvements to dispersion and increased consistency resulting from specific changes in manufacturing processes were shown numerically. Findings provide a manufacturing recommendation to achieve optimum dispersion and mechanical properties of the composite.
Jahan SA, Abdelgader M, Barkery E, et al., 2018, Effect of functionalization on mechanical properties of hybrid carbon fiber reinforced polymer (HCFRP) composite using piezopectroscopy
Hybrid carbon fiber reinforced polymer (HCFRP) composites filled with alumina nanoparticle reinforcements display improved material properties such as fracture toughness and resistance to crack propagation. However, good dispersion of nanoscale materials in the matrix is important to maximize the improvements in the properties. Uniaxial tensile tests with concurrent digital image correlation (DIC) and piezospectroscopy (PS) were used to quantify the mechanical property and load distribution between the carbon fiber/epoxy and reinforcing nanoparticles. Dispersion and sedimentation of the nanoparticles in the composite are found to have a direct effect on the mechanical behavior of the reinforced composite. Difference in load distribution is identified through the piezospectroscopic measurement of the alumina nanoparticles. The results provide significant quantitative information that help to improve the manufacturing process, to optimize the particle dispersion and, subsequently, the mechanical properties.
Tebbutt JA, Vahdati M, Carolan D, et al., 2017, Numerical investigation on an array of Helmholtz resonators for the reduction of micro-pressure waves in modern and future high-speed rail tunnel systems, Journal of Sound and Vibration, Vol: 400, Pages: 606-625, ISSN: 1095-8568
Previous research has proposed that an array of Helmholtz resonators may be an effective method for suppressing the propagation of pressure and sound waves, generated by a high-speed train entering and moving in a tunnel. The array can be used to counteract environmental noise from tunnel portals and also the emergence of a shock wave in the tunnel. The implementation of an array of Helmholtz resonators in current and future high-speed train-tunnel systems is studied. Wave propagation in the tunnel is modelled using a quasi-one-dimensional formulation, accounting for non-linear effects, wall friction and the diffusivity of sound. A multi-objective genetic algorithm is then used to optimise the design of the array, subject to the geometric constraints of a demonstrative tunnel system and the incident wavefront in order to attenuate the propagation of pressure waves. It is shown that an array of Helmholtz resonators can be an effective countermeasure for various tunnel lengths. In addition, the array can be designed to function effectively over a wide operating envelope, ensuring it will still function effectively as train speeds increase into the future.
Hanhan I, Selimov A, Carolan D, et al., 2017, Quantifying alumina nanoparticle dispersion in hybrid carbon fiber composites using photoluminescent spectroscopy, Applied Spectroscopy, Vol: 71, Pages: 258-266, ISSN: 1943-3530
Composites modified with nanoparticles are of interest to many researchers due to the large surface-area-to-volume ratio of nano-scale fillers. One challenge with nanoscale materials that has received significant attention is the dispersion of nanoparticles in a matrix material. A random distribution of particles often ensures good material properties, especially as it relates to the thermal and mechanical performance of composites. Typical methods to quantify particle dispersion in a matrix material include optical, scanning electron, and transmission electron microscopy. These utilize images and a variety of analysis methods to describe particle dispersion. This work describes how photoluminescent spectroscopy can serve as an additional technique capable of quickly and comprehensively quantifying particle dispersion of photoluminescent particles in a hybrid composite. High resolution 2D photoluminescent maps were conducted on the front and back surfaces of a hybrid carbon fiber reinforced polymer containing varying contents of alumina nanoparticles. The photoluminescent maps were analyzed for the intensity of the alumina R1 fluorescence peak, and therefore yielded alumina particle dispersion based on changes in intensity from the embedded nanoparticles. A method for quantifying particle sedimentation is also proposed that compares the photoluminescent data of the front and back surfaces of each hybrid composite and assigns a single numerical value to the degree of sedimentation in each specimen. The methods described in this work have the potential to aid in the manufacturing processes of hybrid composites by providing on-site quality control options, capable of quickly and noninvasively providing feedback on nanoparticle dispersion and sedimentation.
Selimov A, Hoover R, Fouliard Q, et al., 2017, Characterization of hybrid carbon fiber composites using photoluminescence spectroscopy
Hybrid carbon fiber reinforced polymers (HCFRPs) are a new breed of material that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, it is possible to achieve improved mechanical behavior and enable structural sensing to create unique hybrid properties. The photoluminescent properties of the alumina inclusions allow for the application of local stress measurements through piezospectroscopy (PS) in addition to dispersion characterization. Measuring the shift in emission wavenumber at several points across the face of a sample allows for determination of the local stress through the application of the PS relationship. Measuring local intensity differences across the face of the sample, alternatively, allows for the determination of relative local particle concentration for dispersion characterization. Through investigation of an HCFRP sample loaded with 10 wt% of alumina nanoparticles, it was found that stress was greater in regions with high relative particle concentrations upon mechanical loading. Further investigation also found evidence of particle-matrix debonding, characterized by a lower particle stress response to increasing composite strain at higher loads. In order to address both of these issues silane coupling agents are utilized to adjust particle behavior. It is found that the use of these treatments results in improved particle dispersion and reduced sedimentation. A reactive and non-reactive surface treatment were compared and it was found that the reactive treatment was more effective at improving dispersion for the weight percentage investigated. The outcomes of this work demonstrate the potential of utilizing the photo- luminescent sensing capability of these reinforcing particulates to tailor the design of the hybrid carbon fiber composites.
Selimov A, Hoover R, Fouliard Q, et al., 2017, Characterization of hybrid carbon fiber composites using photoluminescence spectroscopy
© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Hybrid carbon fiber reinforced polymers (HCFRPs) are a new breed of material that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, it is possible to achieve improved mechanical behavior and enable structural sensing to create unique hybrid properties. The photoluminescent properties of the alumina inclusions allow for the application of local stress measurements through piezospectroscopy (PS) in addition to dispersion characterization. Measuring the shift in emission wavenumber at several points across the face of a sample allows for determination of the local stress through the application of the PS relationship. Measuring local intensity differences across the face of the sample, alternatively, allows for the determination of relative local particle concentration for dispersion characterization. Through investigation of an HCFRP sample loaded with 10 wt% of alumina nanoparticles, it was found that stress was greater in regions with high relative particle concentrations upon mechanical loading. Further investigation also found evidence of particle-matrix debonding, characterized by a lower particle stress response to increasing composite strain at higher loads. In order to address both of these issues silane coupling agents are utilized to adjust particle behavior. It is found that the use of these treatments results in improved particle dispersion and reduced sedimentation. A reactive and non-reactive surface treatment were compared and it was found that the reactive treatment was more effective at improving dispersion for the weight percentage investigated. The outcomes of this work demonstrate the potential of utilizing the photo- luminescent sensing capability of these reinforcing particulates to tailor the design of the hybrid carbon fiber c
Carolan D, Ivankovic A, Kinloch AJ, et al., 2016, Toughened carbon fibre reinforced polymer composites with nanoparticle modified epoxy matrices, Journal of Materials Science, Vol: 52, Pages: 1767-1788, ISSN: 1573-4803
In the current work the microstructure and fracture performance of carbon-fibre reinforcedpolymer (CFRP) composites based upon matrices of an anhydride-cured epoxy-resin (formulatedwith a reactive diluent), and containing silica nanoparticles and/or polysiloxane core-shellrubber (CSR) nanoparticles, were investigated. Double cantilever beam tests were performed inorder to determine the interlaminar fracture energy of the CFRP composites, while the singleedge-notched bend (SENB) specimen was employed to evaluate the fracture energy of the bulkpolymers. The fracture energy of the bulk epoxy polymers increased from 173 J/m2 for theunmodified polymer to a maximum of 1,237 J/m2 with the addition of 16 wt% of CSRnanoparticles. The toughening mechanisms were identified as (a) localised plastic shear yieldingand (b) cavitation of the CSR particles followed by plastic void growth of the matrix. The steadystatepropagation value of the interlaminar fracture energy of the CFRP composites increasedwith increasing nanoparticle concentration, from 1,246 J/m2 for the unmodified epoxy matrix toa maximum of 1,851 J/m2 with 4 wt% of silica nanoparticles and 8 wt% of CSR nanoparticles.Crack growth in the CFRP composites was dominated by fibre-bridging toughening mechanisms.The efficiency of the transfer of toughness from the bulk polymers to the carbon fibre compositeswas considered. The measured fracture energy of both bulk and composite materials decreasedat a test temperature of -80°C, compared with room temperature, i.e. 20°C. Nevertheless, thetoughening effects of both the silica and CSR nanoparticles on the bulk epoxy polymers and theCFRP composites, compared with the unmodified epoxy polymers, were still evident even at thelower temperature. Indeed, the toughening effect of the silica nanoparticles was greater at -80°Cthan at room temperature.
Kinloch AJ, Carolan D, Ivankovic A, et al., 2016, Mechanical and fracture performance of carbon fibre reinforced composites with nanoparticle modified matrices, 21st European Conference on Fracture, ECF21, Publisher: Elsevier, Pages: 96-103, ISSN: 1877-7058
The microstructure and fracture performance of carbon-fibre reinforced polymer (CFRP) composites with an epoxy resin curedwith an anhydride hardener containing silica nanoparticles and/or polysiloxane core-shell rubber (CSR) particles was investigatedin the current work. Double cantilever beam tests were performed in order to evaluate the fracture energy of the CFRPcomposites, while the single edge notched bend (SENB) specimen was employed to evaluate the fracture energy of the bulkpolymers. Tests were conducted at room temperature and at -80°C. The transferability of the toughness from the bulk polymers tothe fibre-composite systems is discussed, with an emphasis on elucidating the toughening mechanisms
Lim YJ, Carolan D, Taylor AC, 2016, Simultaneously tough and conductive rubber–graphene–epoxy nanocomposites, Journal of Materials Science, Vol: 51, Pages: 8631-8644, ISSN: 0022-2461
This work investigates the effect of adding graphene nanoplatelets (GNP) and either a phase-separating carboxyl-terminated butadiene acrylonitrile rubber (CTBN) or a polysiloxane core–shell rubber (CSR) to an anhydride-cured epoxy polymer. The effect of adding a reactive diluent to the resin was also investigated. The relationship between the microstructure and the resultant electrical and mechanical properties was investigated. The fracture energy of the unmodified epoxy polymer increased from 125 to 668 J/m2 with the addition of 9 wt% CTBN and 12.5 % reactive diluent. The subsequent addition of GNP to the rubber systems decreased the fracture energy. The epoxy nanocomposites modified with only GNP exhibited only a modest increase in measured fracture energy. The major toughening mechanisms in the rubber-modified formulations were observed to be shear band yielding and cavitation of the rubber particles followed by plastic void growth of the epoxy matrix. The electrical conductivity of the hybrid systems was also investigated. It was observed that the conductivity of the nanocomposites improved when 0.5 wt% of GNP was added although this improvement was lost in a CTBN–GNP system while the conductivity was further improved in the CSR–GNP system over the GNP only system with low-CSR particle loadings. It is demonstrated that this behaviour can be directly attributed to the microstructure of the nanocomposite. The results demonstrate that separation of nanomodified phases at the microscale can be used to develop simultaneously tough and conductive composites.
Kinloch AJ, Carolan D, Ivankovic A, et al., 2016, Toughening of epoxy-based hybrid nanocomposites., Polymer, Vol: 97, Pages: 179-190, ISSN: 0032-3861
The microstructure and fracture performance of an epoxy resin cured with an anhydride hardener containing silica nanoparticles and/or polysiloxane core-shell rubber (CSR) nanoparticles were investigated in the current work. The effect of adding a reactive diluent, i.e. hexanediol diglycidylether, to the epoxy resin was also investigated. The fracture energy of the neat (i.e. unmodified) epoxy polymer increased slightly from 125 J/m2 to 172 J/m2 due to the addition of 25 wt% of the reactive diluent to the epoxy. The fracture energy of the unmodified epoxy polymer increased to 889 J/m2 when 20 wt% of the CSR nanoparticles were added to the epoxy without any reactive diluent being present. However, the results show that the increase in fracture energy due to the addition of the CSR nanoparticles particles was much more marked in the case when 25 wt% of the reactive diluent was present, e.g. an increase to 1237 J/m2 with the addition of 16 wt% of CSR nanoparticles. Furthermore, while the subsequent addition of silica nanoparticles, to give hybrid epoxy polymer nanocomposites, i.e. which contained both silica and CSR nanoparticles, produced only modest increases in the fracture energy in the case of the epoxy with the reactive diluent additive present, some synergistic effects on the toughening were noted. No significant improvements in toughness were found for the hybrid epoxy polymer nanocomposites without reactive diluent. The measured toughness of the hybrid materials can be related to the degree of dispersion of both nanoparticle phases in the epoxy polymer matrix. The toughening mechanisms were identified and the experimentally measured values of toughness were in good agreement with modelling studies.
Hanhan I, Selimov A, Carolan D, et al., 2016, Characterizing mechanical properties of hybrid alumina carbon fiber composites with piezospectroscopy
Carbon fiber composites have become popular in aerospace structures and applications due to their light weight, high strength, and high performance. Recently, scientists have begun investigating hybrid composites that include fibers and particulate fillers, since they allow for advanced tailoring of mechanical properties, such as improved fatigue life. This project investigated a hybrid carbon fiber reinforced polymer (HCFRP) that includes carbon fiber and additional alumina nanoparticle fillers, which act as embedded nano stresssensors. Utilizing the piezospectroscopic effect, the photo-luminescent (PL) spectral signal of the embedded nanoparticles has been monitored as it changes with stress, enabling noncontact stress detection of the material. The HCRFPs stress-sensitive properties have been investigated in-situ using a laser source and a tensile mechanical testing system. Hybrid composites with varying mass contents of alumina nanoparticles have been studied in order to determine the e↵ect of particle content on the overall stress sensing properties of the material. Additionally, high resolution photo-luminescent maps were collected from the surfaces of each specimen in order to determine the particulate dispersion of specimens with varying alumina content. The dispersion maps also served as a method of quantifying particulate sedimentation, and can aid in the improvement of the manufacturing process. The results showed that the emitted photo-luminescent spectrum can indeed be captured from the embedded alumina nanoparticles, and exhibits a systematic trend in photo-luminescent peak shift with respect to stress, up to a certain critical stress. Therefore, the non-contact stress sensing results shown in this work have strong implications for the development of multi-functional hybrid composites to support structural health monitoring and nondestructive evaluation (NDE) of aerospace structures.
Hanhan I, Selimov A, Carolan D, et al., 2016, Characterizing mechanical properties of hybrid alumina carbon fiber composites with piezospectroscopy
© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Carbon fiber composites have become popular in aerospace structures and applications due to their light weight, high strength, and high performance. Recently, scientists have begun investigating hybrid composites that include fibers and particulate fillers, since they allow for advanced tailoring of mechanical properties, such as improved fatigue life. This project investigated a hybrid carbon fiber reinforced polymer (HCFRP) that includes carbon fiber and additional alumina nanoparticle fillers, which act as embedded nano stresssensors. Utilizing the piezospectroscopic effect, the photo-luminescent (PL) spectral signal of the embedded nanoparticles has been monitored as it changes with stress, enabling noncontact stress detection of the material. The HCRFPs stress-sensitive properties have been investigated in-situ using a laser source and a tensile mechanical testing system. Hybrid composites with varying mass contents of alumina nanoparticles have been studied in order to determine the e↵ect of particle content on the overall stress sensing properties of the material. Additionally, high resolution photo-luminescent maps were collected from the surfaces of each specimen in order to determine the particulate dispersion of specimens with varying alumina content. The dispersion maps also served as a method of quantifying particulate sedimentation, and can aid in the improvement of the manufacturing process. The results showed that the emitted photo-luminescent spectrum can indeed be captured from the embedded alumina nanoparticles, and exhibits a systematic trend in photo-luminescent peak shift with respect to stress, up to a certain critical stress. Therefore, the non-contact stress sensing results shown in this work have strong implications for the development of multi-functional hybrid composites to support structural health monitoring and nondestructive evaluatio
Alveen P, McNamara D, Carolan D, et al., 2015, The influence of microstructure on the fracture properties of polycrystalline cubic boron nitride, COMPUTATIONAL MATERIALS SCIENCE, Vol: 109, Pages: 115-123, ISSN: 0927-0256
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- Citations: 13
McNamara D, Alveen P, Damm S, et al., 2015, A Raman spectroscopy investigation into the influence of thermal treatments on the residual stress of polycrystalline diamond, INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS, Vol: 52, Pages: 114-122, ISSN: 0263-4368
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- Citations: 24
Taylor AC, Carolan D, Chong HM, et al., 2014, Co-continuous polymer systems: A numerical investigation, Computational Materials Science, Vol: 98, Pages: 24-33, ISSN: 0927-0256
A finite volume based implementation of the binary Cahn–Hilliard equation was implemented using an open source library, OpenFOAM. This was used to investigate the development of droplet and co-continuous binary polymer microstructures. It was shown that the initial concentrations of each phase define the final form of the resultant microstructure, either droplet, transition or co-continuous. Furthermore, the mechanical deformation response of the representative microstructures were investigated under both uniaxial and triaxial loading conditions. The elastic response of these microstructures were then compared to a classic representative microstructure based on a face centred cubic arrangement of spheres with similar volume fractions of each phase. It was found that the numerically predicted composite Young’s modulus closely followed the upper Hashin–Shtrikman bound for both co-continuous and classical structures, while significant deviations from analytical composite theory were noted for the calculated values of Poisson’s ratio. The yield behaviour of the composite microstructures was also found to vary between the co-continuous microstructures and the representative microstructure, with a more gradual onset of plastic deformation noted for the co-continuous structures. The modelling approach presented allows for the future investigation of binary composite systems with tuneable material properties.
Alveen P, McNamara D, Carolan D, et al., 2014, Analysis of two-phase ceramic composites using micromechanical models, COMPUTATIONAL MATERIALS SCIENCE, Vol: 92, Pages: 318-324, ISSN: 0927-0256
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- Citations: 10
McNamara D, Alveen P, Carolan D, et al., 2014, Micromechanical study of strength and toughness of advanced ceramics, 20th European Conference on Fracture (ECF), Publisher: ELSEVIER SCIENCE BV, Pages: 1810-1815, ISSN: 2211-8128
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- Citations: 8
Alveen P, McNamara D, Carolan D, et al., 2014, Micromechanical Modelling of Advanced Ceramics with Statistically Representative Synthetic Microstructures, 7th International Conference on Materials Structure and Micromechanics of Fracture (MSMF 7), Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 137-140, ISSN: 1013-9826
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