The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Vincent Placet - One of the best experts on this subject based on the ideXlab platform.
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characterization of the thermo mechanical behaviour of hemp Fibres intended for the manufacturing of high performance composites
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Vincent PlacetAbstract:Abstract In this paper, the thermo-mechanical behaviour of hemp Fibres ( Cannabis sativa L . ) is investigated by means of a dynamic mechanical analyser. Experiments were performed at a frequency of 1 Hz, over the temperature range between 20 °C and 220 °C. When a periodic stress is applied to an Elementary Fibre, an increase in its rigidity and a decrease in its damping capacity are observed. These changes in its mechanical properties tend to stabilize after an identified number of cycles, thus providing evidence of an “adaptation” phenomenon. This specific mechanical behaviour certainly involves biochemical and/or structural modifications, such as microfibril reorientation, in the material’s organisation. In addition, the behaviour of hemp Fibres is affected by temperature, which acts not only as an activation factor, but also as a degradation factor with respect to the visco-elastic properties of the Fibres. The rigidity and endurance of the Fibres are highly affected by thermal treatment at temperatures above 150 °C, and up to 180 °C. Taking these results into account, polypropylene–hemp Fibre composites were manufactured using a specific processing cycle. By respecting the integrity of the Fibres during manufacturing, it is found that with such composites, comparatively high performance can be achieved with some specific mechanical properties. This is highly encouraging for applications requiring high mechanical performance.
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Characterization of the thermo-mechanical behaviour of Hemp Fibres intended for the manufacturing oh high performance composites
Composites Part A: Applied Science and Manufacturing, 2009Co-Authors: Vincent PlacetAbstract:In this paper, the thermo-mechanical behaviour of hemp Fibres (Cannabis sativa L.) is investigated using a Dynamic Mechanical Analyser. Experiments are performed at a frequency of 1 Hz in the temperature range of 20 to 220°C. When a periodic solicitation is applied to an Elementary Fibre, an increase of the Fibre rigidity and a reduction of the damping capacity are observed. These evolutions aim at stabilization after an identified number of cycles, traducing a phenomenon of “adaptation”. This specific mechanical behaviour certainly involves biochemical and/or structural modifications in the material organisation as microfibrils reorientation. In addition, the behaviour of hemp Fibres is affected by temperature. Temperature acts as an activation factor but also as a degradation factor of the viscoelastic properties of Fibres. The rigidity and the endurance of Fibres are highly affected by thermal treatment at temperature above 150°C to 180°C. Taking into account these results, polypropylene-hemp Fibres composites were manufactured using a specific processing cycle. By respecting the integrity of Fibres during manufacturing, it appears that the relatively high level of the specific mechanical properties of composites is really encouraging in sight of applications requiring high mechanical performances.
A.w. Van Vuure - One of the best experts on this subject based on the ideXlab platform.
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Mechanical behaviour of hemp Fibre composites in relation to their microstructure by micro strain mapping, computed tomography, and biochemical analysis
2020Co-Authors: C.a. Fuentes, Jordi Petit, Jörg Müssig, J. Witters, Y. Ruan, Luisa M Trindade, Peter Willekens, A.w. Van VuureAbstract:This manuscript describes the effects of alterations in biochemical composition on structural morphology and the mechanical behaviour of Elementary and technical Fibres of hemp used for composite applications. First, the strength and apparent Young's modulus distribution of technical Fibres of hemp of 96 hemp samples, corresponding to 32 different hemp accessions cultivated in 3 locations, were analysed using Weibull distribution. From these, 2 samples (one with high and one with low Fibre strength) were selected for further analysis. Next, full-field strain measurement at the micro-scale during tensile loading was used for evaluating both, the stress-strain behaviour at a global scale and the local mechanical behaviour heterogeneity at a micro-scale, along Elementary and technical Fibres of hemp. At the composite level, the local behaviour of each phase of the composite (Fibre and matrix) and of the Fibre/matrix interphase during a transversal 3 point bending test were characterized. Results show that the strength of technical Fibres of hemp is highly dependent on the shear strength between Elementary Fibres, which itself is related to the biochemical composition of the middle lamellae. A correlation between the strength of a technical Fibre and their Elementary Fibres was also observed. At the composite level, the relation of the composite mechanical behaviour (Young's modulus and strength) with the technical or Elementary Fibre mechanical behaviour is complex and might depend on the combination of multiple factors such as the matrix (thermoset or thermoplastic), or the technical Fibre sample employed (weak or strong) and the level of Fibre-matrix wetting (impregnation) and adhesion.
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Investigation of the tensile behavior of treated flax Fibre bio-composites at ambient humidity
Composites Science and Technology, 2018Co-Authors: Dieter Perremans, Ignaas Verpoest, Christine C. Dupont-gillain, A.w. Van VuureAbstract:Abstract The high specific strength and stiffness and excellent damping behavior promote the use of flax Fibre composites in the construction sector. However, the limited compatibility between raw flax Fibres and bio-epoxy resin often leads to composites with mechanical properties well below their theoretical capacities. Moreover, the incomplete understanding of the intrinsic non-linear mechanical behavior of flax Fibre composites forces the application of larger safety factors. In this study, three chemical treatments are applied to improve the interphase properties and gain further insight in the longitudinal tensile behavior of flax Fibre bio-epoxy composites. Both alkali and APS treatment result in a threefold improvement in the transverse flexural strength to ∼30MPa. Both treatments additionally shift the weakest link to the Elementary Fibre interphase strength. Analysis of the longitudinal tensile stress-strain curves of UD flax Fibre composites results in a tri-linear shape that is preserved after treatment.
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Effect of the middle lamella biochemical composition on the non-linear behaviour of technical Fibres of hemp under tensile loading using strain mapping
Composites Part A-applied Science and Manufacturing, 2017Co-Authors: C.a. Fuentes, Jordi Petit, C. Thouminot, Jörg Müssig, Luisa M Trindade, Peter Willekens, A.w. Van VuureAbstract:Abstract This manuscript describes the effects of alterations in biochemical composition on structural morphology and the mechanical behaviour of technical Fibres of hemp used for composite applications. First, the strength and apparent Young’s modulus distribution of technical Fibres of hemp of 96 hemp samples, corresponding to 32 different hemp accessions cultivated in 3 locations, were analysed using Weibull distribution. From these, 2 samples (one with high and one with low Fibre strength) were selected for further analysis. Next, full-field strain measurement at the micro-scale during tensile loading via digital image correlation analysis was used for evaluating both, the stress-strain behaviour at a global scale and the local mechanical behaviour heterogeneity at a micro-scale, along a technical Fibre of hemp. The analysis reveals 2 typical types of tensile stress-strain curves, and a complex and very irregular pattern of strain concentrations, which are associated to the technical Fibre strength. The non-linear behaviour of the stress-strain curve is explained by the development of shear strain at the Elementary Fibre (botanically defined as the individual cell) interphases. Micro tomography and biochemical analysis of the technical Fibre microstructure showed that alterations in cell wall composition, in particular substitution of pectin, leads to changes in the non-linear behaviour of technical Fibres of hemp under tensile loading.
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Development of Methodology to Assess the Failure Behaviour of Bamboo Single Fibre by Acoustic Emission Technique
Journal of The Institution of Engineers (India): Series D, 2017Co-Authors: Md. Saiful Alam, A.w. Van Vuure, Fahmida Gulshan, Qumrul Ahsan, Martine Wevers, Helge Pfeiffer, Lina Osorio, Ignaas VerpoestAbstract:Acoustic emission (AE) was used as a tool for detecting, evaluating and for better understanding of the damage mechanism and failure behavior in composites during mechanical loading. Methodology was developed for tensile test of natural Fibres (bamboo single Fibre). A series of experiments were performed and load drops (one or two) were observed in the load versus time graphs. From the observed AE parameters such as amplitude, energy, duration etc. significant information corresponding to the load drops were found. These AE signals from the load drop occurred from such failure as debonding between two Elementary Fibre or from join of Elementary Fibre at edge. The various sources of load at first load drop was not consistent for the different samples (for a particular sample the value is 8 N, stress: 517.51 MPa). Final breaking of Fibre corresponded to saturated level AE amplitude of preamplifier (99.9 dB) for all samples. Therefore, it was not possible to determine the exact AE energy value for final breaking. Same methodology was used for tensile test of three single Fibres, which gave clear indication of load drop before the final breaking of first and second Fibre.
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investigation of microstructure and tensile properties of porous natural coir Fibre for use in composite materials
Industrial Crops and Products, 2015Co-Authors: A.w. Van Vuure, C.a. Fuentes, Le Quan Ngoc Tran, Nguyen T Minh, Ignace VerpoestAbstract:Abstract Natural coir Fibres are studied for use as reinforcement in composite materials. In order to efficiently use the Fibres and understand the composite properties, the microstructure and the mechanical properties of coir Fibres are investigated in this study. X-ray microtomography in SEM (SEM-CT) and SEM image analysis are used to examine the Fibre internal structure including the organisation of Elementary Fibres, microfibril angles and Fibre porosity. Mechanical properties of coir Fibres are determined by performing Fibre tensile tests, in which an integrated optical strain mapping system is used to define Fibre strain for producing more reliable values of E -modulus and strain at failure. The results show that technical coir Fibres comprise plenty of Elementary Fibres and a lacuna at the centre. The Elementary Fibre is built up by two main cell walls which consist of bundles of microfibrils with a large misorientation with respect to the Elementary Fibre axis. Coir Fibres appear to have a high porosity of 22 to 30%. The high microfibrillar angle in the coir Fibres leads to the low stiffness in Fibre direction and to high elongation to failure thanks to reorientation of the microfibrils under tensile loading.
Junqian Zhang - One of the best experts on this subject based on the ideXlab platform.
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the effect of Elementary Fibre variability on bamboo Fibre strength
Materials & Design, 2015Co-Authors: Fang Wang, Jiaxing Shao, Leon M Keer, Lu Li, Junqian ZhangAbstract:Abstract Tensile strength of brittle Fibres exhibits statistical distribution and size dependence. In this work, the average strength of bamboo Fibre is found to decrease from 568 to 483 MPa as mean diameter increases from 196.6 to 584.3 μm. The morphologies of bamboo Fibres with increasing diameters were investigated through Scanning Electron Microscopy (SEM) to demonstrate variations in the quantity of Elementary Fibres. The influence of Elementary Fibre distributions on the Fibre strength was also studied. A modified Weibull model based on number of Elementary Fibres is proposed to perform scaling predictions for the fracture strength of the Fibres at different between-Fibre diameters. It was shown that the predicted results are in reasonable agreement with experimental data, highlighting the adequacies of the new analytical model for describing the diameter dependence of tensile strength.
Bertil Daneholt - One of the best experts on this subject based on the ideXlab platform.
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The adsorption staining technique applied to isolated premessenger ribonucleoprotein particles: a comparison with conventional techniques using electron microscope tomography.
Journal of Microscopy, 1993Co-Authors: Anna Lönnroth, Ulf Skoglund, K. T. Tokuyasu, Bertil DaneholtAbstract:Summary A specific type of premessenger RNP particle, Balbiani ring granules from the dipteran Chironomus tentans, was biochemically isolated and visualized in three dimensions with electron microscope tomography. The particles were prepared for electron microscopy in three different ways: positively stained, negatively stained and adsorption-stained (embedded in polyvinyl alcohol, PVA, and concomitantly stained). The results were compared with those obtained for RNP particles studied in situ in ultrathin sections of plastic-embedded cells. The positively stained particles were compacted and heavily deformed with little or no internal structure. The negatively stained and the adsorption-stained particles were well preserved; the outer contours and the central cavities of the particles were outlined. The internal structure, i.e. the folded 7-nm Elementary Fibre, could not be recognized in the negatively stained particles. In the adsorption-stained particles, however, the Fibre was discernable, although not quite as distinctly demarcated as in the plastic-embedded samples. We conclude that embedding in PVA with concomitant staining with uranyl acetate is a rapid method to obtain both good preservation and staining of isolated RNP particles. The PVA-embedded particles were also found to be sufficiently resistant to irradiation to permit a comprehensive tilt-series to be taken for electron microscope tomography. ribonucleoprotein particles.
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The adsorption staining technique applied to isolated premessenger ribonucleoprotein particles: a comparison with conventional techniques using electron microscope tomography.
Journal of microscopy, 1993Co-Authors: Anna Lönnroth, Ulf Skoglund, K. T. Tokuyasu, Bertil DaneholtAbstract:A specific type of premessenger RNP particle, Balbiani ring granules from the dipteran Chironomus tentans, was biochemically isolated and visualized in three dimensions with electron microscope tomography. The particles were prepared for electron microscopy in three different ways: positively stained, negatively stained and adsorption-stained (embedded in polyvinyl alcohol, PVA, and concomitantly stained). The results were compared with those obtained for RNP particles studied in situ in ultrathin sections of plastic-embedded cells. The positively stained particles were compacted and heavily deformed with little or no internal structure. The negatively stained and the adsorption-stained particles were well preserved; the outer contours and the central cavities of the particles were outlined. The internal structure, i.e. the folded 7-nm Elementary Fibre, could not be recognized in the negatively stained particles. In the adsorption-stained particles, however, the Fibre was discernable, although not quite as distinctly demarcated as in the plastic-embedded samples. We conclude that embedding in PVA with concomitant staining with uranyl acetate is a rapid method to obtain both good preservation and staining of isolated RNP particles. The PVA-embedded particles were also found to be sufficiently resistant to irradiation to permit a comprehensive tilt-series to be taken for electron microscope tomography.
C.a. Fuentes - One of the best experts on this subject based on the ideXlab platform.
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Mechanical behaviour of hemp Fibre composites in relation to their microstructure by micro strain mapping, computed tomography, and biochemical analysis
2020Co-Authors: C.a. Fuentes, Jordi Petit, Jörg Müssig, J. Witters, Y. Ruan, Luisa M Trindade, Peter Willekens, A.w. Van VuureAbstract:This manuscript describes the effects of alterations in biochemical composition on structural morphology and the mechanical behaviour of Elementary and technical Fibres of hemp used for composite applications. First, the strength and apparent Young's modulus distribution of technical Fibres of hemp of 96 hemp samples, corresponding to 32 different hemp accessions cultivated in 3 locations, were analysed using Weibull distribution. From these, 2 samples (one with high and one with low Fibre strength) were selected for further analysis. Next, full-field strain measurement at the micro-scale during tensile loading was used for evaluating both, the stress-strain behaviour at a global scale and the local mechanical behaviour heterogeneity at a micro-scale, along Elementary and technical Fibres of hemp. At the composite level, the local behaviour of each phase of the composite (Fibre and matrix) and of the Fibre/matrix interphase during a transversal 3 point bending test were characterized. Results show that the strength of technical Fibres of hemp is highly dependent on the shear strength between Elementary Fibres, which itself is related to the biochemical composition of the middle lamellae. A correlation between the strength of a technical Fibre and their Elementary Fibres was also observed. At the composite level, the relation of the composite mechanical behaviour (Young's modulus and strength) with the technical or Elementary Fibre mechanical behaviour is complex and might depend on the combination of multiple factors such as the matrix (thermoset or thermoplastic), or the technical Fibre sample employed (weak or strong) and the level of Fibre-matrix wetting (impregnation) and adhesion.
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Effect of the middle lamella biochemical composition on the non-linear behaviour of technical Fibres of hemp under tensile loading using strain mapping
Composites Part A-applied Science and Manufacturing, 2017Co-Authors: C.a. Fuentes, Jordi Petit, C. Thouminot, Jörg Müssig, Luisa M Trindade, Peter Willekens, A.w. Van VuureAbstract:Abstract This manuscript describes the effects of alterations in biochemical composition on structural morphology and the mechanical behaviour of technical Fibres of hemp used for composite applications. First, the strength and apparent Young’s modulus distribution of technical Fibres of hemp of 96 hemp samples, corresponding to 32 different hemp accessions cultivated in 3 locations, were analysed using Weibull distribution. From these, 2 samples (one with high and one with low Fibre strength) were selected for further analysis. Next, full-field strain measurement at the micro-scale during tensile loading via digital image correlation analysis was used for evaluating both, the stress-strain behaviour at a global scale and the local mechanical behaviour heterogeneity at a micro-scale, along a technical Fibre of hemp. The analysis reveals 2 typical types of tensile stress-strain curves, and a complex and very irregular pattern of strain concentrations, which are associated to the technical Fibre strength. The non-linear behaviour of the stress-strain curve is explained by the development of shear strain at the Elementary Fibre (botanically defined as the individual cell) interphases. Micro tomography and biochemical analysis of the technical Fibre microstructure showed that alterations in cell wall composition, in particular substitution of pectin, leads to changes in the non-linear behaviour of technical Fibres of hemp under tensile loading.
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investigation of microstructure and tensile properties of porous natural coir Fibre for use in composite materials
Industrial Crops and Products, 2015Co-Authors: A.w. Van Vuure, C.a. Fuentes, Le Quan Ngoc Tran, Nguyen T Minh, Ignace VerpoestAbstract:Abstract Natural coir Fibres are studied for use as reinforcement in composite materials. In order to efficiently use the Fibres and understand the composite properties, the microstructure and the mechanical properties of coir Fibres are investigated in this study. X-ray microtomography in SEM (SEM-CT) and SEM image analysis are used to examine the Fibre internal structure including the organisation of Elementary Fibres, microfibril angles and Fibre porosity. Mechanical properties of coir Fibres are determined by performing Fibre tensile tests, in which an integrated optical strain mapping system is used to define Fibre strain for producing more reliable values of E -modulus and strain at failure. The results show that technical coir Fibres comprise plenty of Elementary Fibres and a lacuna at the centre. The Elementary Fibre is built up by two main cell walls which consist of bundles of microfibrils with a large misorientation with respect to the Elementary Fibre axis. Coir Fibres appear to have a high porosity of 22 to 30%. The high microfibrillar angle in the coir Fibres leads to the low stiffness in Fibre direction and to high elongation to failure thanks to reorientation of the microfibrils under tensile loading.