Publications
21 results found
Chen Y, Quino G, Pellegrino A, 2024, A comprehensive investigation on the temperature and strain rate dependent mechanical response of three polymeric syntactic foams for thermoforming and energy absorption applications, Polymer Testing, Vol: 130, ISSN: 0142-9418
Polymeric syntactic foams (PSF) are a kind of composite material, which consists of a polymer matrix reinforced by hollow thin wall glass micro-spheres. Because of their low density, low moisture absorption, relatively high specific strength and stiffness, PSF are often employed in aerospace and submarine applications in which they are subjected to a wide range of temperature conditions. Due to the temperature sensitivity of the polymer matrix, the physical and mechanical behaviour of PSFs is highly sensitive to temperature variations. Besides, their dynamic response is significantly affected by the strain rate. This research investigates the temperature and strain rate dependence of the mechanical behaviour of polyurethane, epoxy and nylon syntactic foams under compressive and tensile loads. The selected materials have in common that their mechanical characteristics, thermal properties, and dimensional stability make them suitable for both impact engineering and thermoforming applications. The experimental results, acquired over a temperature range from −25 °C to 100 °C at low and high strain rates, reveal a clear interplay between temperature and strain rate effects on the mechanical behaviour of the materials under investigation. This synergy is observed to vary based on both the matrix material and the loading mode. Notably, the rate dependency of polyurethane and nylon syntactic foams is significantly influenced by the testing temperature during compression, while in tension the influence of the temperature on the rate dependency is moderate or negligible. In contrast, the rate dependency of the epoxy syntactic foam remains largely unaffected by the testing temperature. Deformation and failure mechanisms were analysed by examining the failure surface of the tested samples using SEM micrographs.
Gargiuli JF, Quino G, Board R, et al., 2023, Examining the quasi-static uniaxial compressive behaviour of commercial high-performance epoxy matrices, Polymers, Vol: 15, ISSN: 2073-4360
Four commercial high-performance aerospace aromatic epoxy matrices, CYCOM®890, CYCOM®977-2, PR520, and PRISM EP2400, were cured to a standardised 2 h, 180 °C cure cycle and evaluated in quasi-static uniaxial compression, as well as by dynamic scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermoplastic toughened CYCOM®977-2 formulation displayed an overall increase in true axial stress values across the entire stress-strain curve relative to the baseline CYCOM®890 sample. The particle-toughened PR520 sample exhibited an overall decrease in true axial stress values past the yield point of the material. The PRISM EP2400 resin, with combined toughening agents, led to true axial stress values across the entire plastic region of the stress-strain curve, which were in line with the stress values observed with the CYCOM®890 material. Interestingly, for all formulations, the dilation angles (associated with the volume change during plastic deformation), recorded at 0.3 plastic strain, were close to 0°, with the variations reflecting the polymer structure. Compression data collected for this series of commercial epoxy resins are in broad agreement with a selection of model epoxy resins based on di- and tetra-functional monomers, cured with polyamines or dicarboxylic anhydrides. However, the fully formulated resins demonstrate a significantly higher compressive modulus than the model resins, albeit at the expense of yield stress.
Xu Y, Quino G, Ramakrishnan KR, et al., 2023, Effects of build orientation and strain rate on the tensile-shear behaviour of polyamide-12 manufactured via laser powder bed fusion, MATERIALS & DESIGN, Vol: 232, ISSN: 0264-1275
Quino G, Gargiuli J, Pimenta S, et al., 2023, Experimental characterisation of the dilation angle of polymers, Polymer Testing, Vol: 125, Pages: 1-7, ISSN: 0142-9418
Despite the wide use of Drucker-Prager plasticity-based models on polymers, the experimental measurement of the dilation angle, a critical parameter to fully describe the plastic potential, has been rarely reported in existing literature. This paper shows, for the first time, the experimental characterisation of the dilation angle of polymers over a wide range of plastic strain. These measurements were obtained from uniaxial compression experiments conducted on poly(methyl methacrylate) (PMMA) and an untoughened epoxy resin. The calculation of the dilation angle relied on the measurements of the compressive force and the strain components obtained via Digital Image Correlation (DIC). Lower values of dilation angle were obtained for the epoxy resin, suggesting that resistance to volumetric change during plastic deformation could be associated to molecular structure and internal forces. The methodology and results presented in this study can be applied to different types of materials and employed for developing and validating constitutive models that incorporate plastic dilation.
Quino Quispe G, Ramakrishnan KR, 2023, The “tattoo” speckle pattern: fabrication and application, 20th International Conference on Experimental Mechanics, Pages: 905-906
Digital Image Correlation (DIC) is widely used in experimental mechanics for full field measurement of displacements and strains. The application of this technique, normally requires the preparation of specimens with a random speckle pattern, via spray painting, stamping,manual patterning, etc. The applicability of most techniques to create random patterns is still limited. For instance, traditional methods such as airbrush painting are not suitable when time available to produce the speckle pattern is limited. The development and application of a noveltechnique to address this problem is presented in this paper. The developed technique makes use of commercially available temporary tattoo paper, adhesives, and paint. The presented technique showed to be quick, repeatable, consistent, and stable even under impact loads andlarge deformations. Additionally, they offer the possibility to optimise and customise the speckle pattern.
Anthony D, Woodgate C, Shaw C, et al., 2023, Hierarchical solutions to compressive problems in fibre-reinforced composites, ECCM20 - The 20th European Conference on Composite Materials, Publisher: Composite Construction Laboratory (CCLab), Pages: 1512-1517
Currently, the useable compressive properties of a composite are restricted by set design limits well below the expected intrinsic performance of the materials contained within. The next generation of high-performance fibre-reinforced polymer composites will need to address the challenge of improving the absolute performance of composites in compression. This task requires a rethink of the whole system; not only to address practical limitations of current materials, but their combination, interface, and their architecture. The mechanisms involved do not simply act over the nano-, macro-, or meso-level independently, but are mutually related at the system level, complicating the approach.
Quino G, Gargiuli J, Pimenta S, et al., 2023, EXPERIMENTAL CHARACTERISATION OF THE DILATION ANGLE OF POLYMERS
Zhang B, Quino G, Robinson P, et al., 2023, SHEAR AND COMPRESSION-SHEAR CHARACTERISATION OF A POLYMER MATRIX FOR CARBON FIBRE COMPOSITES
The compression behaviour of unidirectional carbon fibre/epoxy composites has been widely investigated. The poor compression properties of the material relate to the material instability which leads to the formation of fibre kinkbands. At high fibre volume fractions, this instability results from the polymer matrix which is sheared due to the misalignment of the compressed fibres, culminating in yielding or fracture of the matrix or failure at the matrix-fibre interface. In this study, the shear response of an epoxy polymer matrix under pure shear and shear-compression deformation was investigated. Hollow, thin-walled Prime 27 epoxy specimens were manufactured by machining from cured epoxy cylinders. Experimental results showed that the specimens exhibited a uniform in-plane shear strain in the gauge section in both test modes. The average yield stress of the compression-shear specimens (51.0 MPa) was slightly lower than that of the pure-shear specimens (54.9 MPa), due to the applied compression stress. The shear moduli of the specimens for both test modes were consistent with only 3.8% difference. The applied compression stress delayed the specimen failure and achieved a higher fracture strain. The data collected in these tests will be used in finite element (FE) modelling to explore how the compression behaviour of unidirectional composites can be improved.
Quino G, Robinson P, Trask RS, 2022, Design of a bending experiment for mechanical characterisation of pultruded rods under compression, 20th European Conference on Composite Materials, Publisher: EPFL Lausanne, Composite Construction Laboratory
Carbon fibre pultruded rods are used in structural applications across a wide range of industries due to their lightweight, corrosion/fatigue resistance and outstanding properties in the axial direction. While there is available literature on the mechanical characterisation of pultruded rods under tension and bending, very little has been reported about their compression response. The characterisation of the mechanical performance of pultruded rods under uniaxial direct compression is challenging due to the high sensitivity to alignment, stress concentrations in the gripping zone, and the complexity of specimen manufacturing, especially when the rodscan be of small diameter (~1mm).Existing literature reports the use of the compression side of a beam under bending to test materials with high axial stiffness and strength such as carbon fibre laminates. In this work, we show the applicability of such idea on pultruded rods. We report on the design of a novel bendingexperiment to characterise the compression behaviour of pultruded rods, ensuring low strain gradient and consistent failure within the gauge section.
Sommer DE, Thomson D, Falco O, et al., 2022, Damage modelling of carbon fibre composite crush tubes: Numerical simulation and experimental validation of drop weight impact, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING, Vol: 160, ISSN: 1359-835X
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- Citations: 11
Ramakrishnan KR, Quino G, Dulieu-Barton J, 2022, COMBINED DIC-INFRARED THERMOGRAPHY FOR HIGH STRAIN RATE TESTING OF COMPOSITES, Pages: 447-454
Infrared Thermography (IRT) is a full-field measurement technique for evaluating defects or damage in a material by localized variation in the surface temperature observed using a thermal camera. The occurrence of damage in composite structure is accompanied by heat dissipation and a subsequent temperature evolution on the specimen surface. The thermal images provide quantitative information about location and magnitude of hot spots and, in turn, of the damage mechanisms. Therefore, surface temperature analysis using an infrared camera can be applied to better understand the damage mechanisms and energy absorption in composites. In this paper, simultaneous high-speed white-light and infrared imaging were conducted to obtain quantitative description of thermomechanical response of the material and to study the formation and propagation of shear localizations from the temperature history.
Xu Y, Zhou J, Quino G, et al., 2022, EXPERIMENTAL ANALYSIS OF GLASS FIBRE REINFORCED NYLON-66 UNDER COMBINED LOADING AT LOW AND HIGH RATES OF STRAIN, Pages: 240-247
Reinforced polymer composites are increasingly used in various industrial applications because of their lightweight and superior stiffness-strength combination. In these engineering practices, composites are commonly subjected to multiaxial loads and behave at strain rates ranging from low to high. However, most existing studies that focus on the mechanical characterisation of composites are limited to single loading modes involving tensile, flexural, compressive, and fatigue. The multiaxial behaviour of 30% glass fibre reinforced nylon-66 (PA66-GF30) is investigated in this study through combined tension-torsion experiments. A thin-walled tube geometry of specimens and gripping fixtures are designed to enable appropriate failure of the material under tensile and torsional loading. The quasi-static experimental data depict the multiaxial failure of PA66-GF30 subjected to different stress states including pure shear, combined shear-tension, and plain strain tension. High-rate combined loading experiments are implemented using a novel split Hopkinson tension-torsion bar system to unravel the rate dependence.
Quino G, Pellegrino A, Petrinic N, 2021, Composites in extreme environments: Effects of high strain rate, humidity and temperature, ISSN: 1742-6588
Multifunctionality, lightweight and resistance to corrosion are some of the several advantages that fibre composites display with respect to other materials across a wide range of applications. In aerospace and marine industry, however, we can encounter challenges arising from certain working conditions that can significantly affect the mechanical response and integrity of composite structures. First, humidity or water exposure can induce reduction of the material strength and stiffness. Second, hot or cold temperatures that change the level of ductility in the composite. Finally, dynamics loads that may appear during service require strain rate sensitive properties to be considered. In this work, we show experimental capabilities and methodologies developed to account for all those three effects: rapidly applied loads (impact), humidity and temperatures from -55°C to 93°C. This understanding sets the basis for the development of advanced models to design better structures.
Ramakrishnan KR, Quino G, Hoffmann J, et al., 2021, High Strain Rate Characterization and Impact Analysis of Fiber Reinforced Composites, Pages: 95-99, ISSN: 2191-5644
Fiber reinforced polymer (FRP) composite materials have been used in aerospace applications such as engine blades, brackets, interiors, nacelles, propellers/rotors, and single aisle wings. It is well recognized that composites are sensitive to damage caused by impact during their service life. A complete constitutive model of composite material that can predict the mechanical performance and the development of damage leading to failure is still an on-going research endeavor. An essential step in the development of constitutive model is dynamic mechanical characterization including tensile, shear, and compressive loading using various testing techniques such as servo-hydraulic system, high rate servo-hydraulic machine, and Split Hopkinson Pressure Bar (SHPB) to properly satisfy critical design requirements. In this chapter, a comprehensive approach combining micromechanical modeling, dynamic mechanical characterization, and macroscale Finite Element modeling is presented to study the high-velocity impact response of carbon fiber reinforced composites manufactured from UD tapes.
Quino G, Chen Y, Ramakrishnan KR, et al., 2021, Speckle patterns for DIC in challenging scenarios: rapid application and impact endurance, Measurement Science and Technology, Vol: 32, Pages: 1-10, ISSN: 0957-0233
Digital image correlation (DIC) is a widely used technique in experimental mechanics for full field measurement of displacements and strains. The subset matching based DIC requires surfaces containing a random pattern. Even though there are several techniques to create random speckle patterns, their applicability is still limited. For instance, traditional methods such as airbrush painting are not suitable in the following challenging scenarios: (i) when time available to produce the speckle pattern is limited and (ii) when dynamic loading conditions trigger peeling of the pattern. The development and application of some novel techniques to address these situations is presented in this paper. The developed techniques make use of commercially available materials such as temporary tattoo paper, adhesives and stamp kits. The presented techniques are shown to be quick, repeatable, consistent and stable even under impact loads and large deformations. Additionally, they offer the possibility to optimise and customise the speckle pattern. The speckling techniques presented in the paper are also versatile and can be quickly applied in a variety of materials.
Tagarielli V, quino G, Petrinic N, 2020, Effects of water absorption on the mechanical properties of GFRPs, Composites Science and Technology, Vol: 199, Pages: 1-11, ISSN: 0266-3538
This study reports on the effects of water absorption on the anisotropic mechanical response ofan epoxy resin reinforced with E-glass fibres. Composite specimens were conditioned byimmersion in pure water at 50ºC for different time durations, up to full saturation. Water saturation resulted in reduction of stiffness and strength, in the range of strain rate0.001−700s− 1. Experiments on re-dried specimens after water saturation showed only a small recoverability of the original mechanical properties. Water absorption increased the sensitivity of the mechanical response of the GFRPs to the applied strain rate. Finite element simulations of the response of a unit cell of the unidirectional composite were performed to understand the role of the hygroscopic stresses induced by water absorption, and it was found that this is negligible due to the active mechanisms of viscoelastic relaxation.
Thomson D, Quino G, Cui H, et al., 2020, Strain-rate and off-axis loading effects on the fibre compression strength of CFRP laminates: Experiments and constitutive modelling, Composites Science and Technology, Vol: 195, ISSN: 0266-3538
A series of dynamic longitudinal compression tests have been performed on cross-ply IM7/8552 specimens cut at different off-axis angles to produce different combinations of compression and shear stresses. Together with results from previous quasi-static tests of the same kind, quasi-static and dynamic fibre kinking failure envelopes have been obtained using classical laminate theory. This new experimental data has been compared against predictions from the leading fibre kinking theories, made rate-dependent by using rate-dependent in-plane shear properties, and show that, while they can accurately predict the effects of strain rate on the uniaxial compression strength, they are unable to capture the effects of shear, neither at quasi-static nor dynamic rates. Instead, a simpler more phenomenological approach is proposed to predict the rate-dependent fibre kinking strength of FRP laminates under multi-axial loads until the micromechanics can be more accurately described.
De Cola F, Quino G, Dragnevski K, et al., 2019, An extended in-situ method to improve the understanding of fracture mechanics of granular materials using sound measurements, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, Vol: 76, Pages: 1-12, ISSN: 0997-7538
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- Citations: 6
Quino G, De Cola F, Tagarielli V, et al., 2019, Exploring the application of sound measurements to assess the structural integrity of fibre bundles, 25th International Conference on Fracture and Structural Integrity, Publisher: ELSEVIER SCIENCE BV, Pages: 507-515, ISSN: 2452-3216
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- Citations: 1
Quino G, Pellegrino A, Tagarielli VL, et al., 2018, Measurements of the effects of pure and salt water absorption on the rate-dependent response of an epoxy matrix, Composites Part B: Engineering, Vol: 146, Pages: 213-221, ISSN: 1359-8368
The study reports the measured effects of water absorption on an epoxy resin. Epoxy samples were exposed to wet conditioning environments including pure water, NaCl-water solution, and pure water at boiling temperature, measuring absorption as a function of time. Vickers hardness and indentation creep tests were performed and the mechanical response of the material to uniaxial stress was also measured in both compression and tension, at imposed strain rates in the range 0.001–2500 s−1. It was found that the absorption of both pure and salt water caused decrease of stiffness, yield stress and hardness, but only mildly affected the sensitivity of the response to the imposed strain rate and the tensile ductility. Mechanical testing after re-drying of the samples revealed the permanent effects of water absorption.
Quino G, El Yagoubi J, Lubineau G, 2014, Characterizing the toughness of an epoxy resin after wet aging using compact tension specimens with non-uniform moisture content, POLYMER DEGRADATION AND STABILITY, Vol: 109, Pages: 319-326, ISSN: 0141-3910
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- Citations: 21
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