The Experts below are selected from a list of 141 Experts worldwide ranked by ideXlab platform
Yan Yu - One of the best experts on this subject based on the ideXlab platform.
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Structural, chemical, and multi-scale mechanical characterization of waste windmill palm fiber (Trachycarpus fortunei)
Journal of Wood Science, 2020Co-Authors: Jing Li, Yan Yu, Xuexia Zhang, Hankun WangAbstract:This study investigated the structural, chemical, and multi-scale mechanical properties of windmill palm (Trachycarpus fortunei) leaf sheath fiber, which were frequently wasted. Significant variation was observed in fiber diameter and cross-sectional morphology among different layers in a single leaf sheath, whereas the chemical composition, relative crystallinity index, and the Microfibrillar Angle (MFA) of palm fibers were almost the same among different layers. Windmill palm fibers had low cellulose contents (34.70–35.5%), low relative crystallinity index (45.7–49.2%), and high MFA (38.8°–29.4°), resulting in low strength and modulus, but high failure strain under tensile load. The tensile fracture surface of windmill palm fibers was assessed through SEM studies and its ductile fracture was confirmed, which can potentially enhance the toughness of composites when used as reinforcement material. Nanoindentation was carried out among different leaf sheath layers, and the results showed the modulus and hardness values of windmill palm fibers are in the same range as other plant fibers. The experimental results may help guide selection of suitable reinforcing fibers for use in composites in different applications.
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The combined effects of initial Microfibrillar Angle and moisture contents on the tensile mechanical properties and Angle alteration of wood foils during tension
Holzforschung, 2017Co-Authors: Hankun Wang, Xuexia Zhang, Zixuan Yu, Yan YuAbstract:Abstract The combined effects of initial microfibril Angle (MFA) and moisture content (MC) on the longitudinal tensile properties of Masson pine (Pinus massoniana Lamb.) wood foils has been investigated. Synchrotron X-ray diffraction (XRDsyn) combined with a custom-built microtensile device was applied for in situ monitoring of the MFA alterations in the foils under different initial MFAs and MCs conditions. The results demonstrate that the tensile properties are highly negatively correlated to both MFA and MC. Furthermore, the tensile modulus is more sensitive to MC change than tensile strength. At a higher MFA, the sensitivity of the two mechanical indicators to MC alteration is enhanced.
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MECHANICAL PROPERTIES OF SILICA CELLS IN BAMBOO MEASURED USING IN-SITU IMAGING NANAINDENTATION
Wood and Fiber Science, 2016Co-Authors: Zixuan Yu, Xuexia Zhang, Zehui Jiang, Yan YuAbstract:In-situ imaging nanoindentation technique was applied to measure the cell wall mechanical properties of silica cells, as well as pure biogenic silica in Moso bamboo ( phyllostachys pubescens Mazel). For comparison, the mechanical properties of thick-walled epidermal cells close to these silica cells, as well as bamboo fibers were also measured. The silica cells were found to have a high cell wall hardness of about 1 GPa, nearly two times that of the values observed for the other two types of cells. Furthermore, we found that biogenic silica had a hardness of as high as 2.68 GPa. This explains why silica cells have such high hardness. Conversely, bamboo fibers showed the highest values for indentation modulus, nearly two times greater than that of the other two cell types. This implies silica cells and epidermal thick-walled cells have a large Microfibrillar Angle compared to bamboo fibers. The present results imply that silica cells with exceptional high hardness may be regarded as a model nanocomposite with cell wall polymers reinforced with SiO 2 nanoparticles. More research is needed on silica cells, as they might provide inspiration for the development of innovative SiO 2 /wood composite products with both high hardness and low production costs.
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Variation of mechanical properties of single bamboo fibers (Dendrocalamus latiflorus Munro) with respect to age and location in culms
Holzforschung, 2014Co-Authors: Hankun Wang, Xiaojing An, Wanju Li, Hao Wang, Yan YuAbstract:Abstract There is a growing need to characterize the mechanical properties of single bamboo fibers with their high potential in commercial applications. In this paper, an improved microtensile technique has been applied to measure the tensile strength of fibers isolated from Ma bamboo (Dendrocalamus latiflorus Munro) as an important commercial bamboo species in China. The property variation with respect to the age and locations within a culm was in focus. Ma bamboo fibers had superior stiffness and strength data compared with those of softwood fibers. Four-year-old Ma bamboo fibers are stiffer and stronger than 1-year-old fibers. Their in-trunk variation is rather small both in radial and longitudinal directions. This is due to the relatively constant Microfibrillar Angle in bamboo culms. Accordingly, the large variations in the bulk mechanical properties of bamboo are mainly attributable to fiber distribution density in the culm rather than the fiber itself.
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Mechanical characterization of single bamboo fibers with nanoindentation and microtensile technique
Holzforschung, 2011Co-Authors: Yan Yu, Hankun Wang, Genlin Tian, Ge WangAbstract:More mechanical information on fibers is needed for better understanding of the complex mechanical behavior of bamboo as well as optimizing design of bamboo fiber based composites. In this paper, in situ imaging nanoindentation and an improved microtensile technique were jointly used to characterize the longitudinal mechanical behavior of fibers of Moso bamboo (Phyllostachys pubescens Mazei ex H. de Lebaie) aged between 0.5 and 4 years. These methods show that 0.5-year-old fibers have similar mechanical performances to their older counterparts. The average longitudinal tensile modulus and tensile strength of Moso bamboo fibers ranges from 32 to 34.6 GPa and 1.43 to 1.69 GPa, respectively, significantly higher than nearly all the published data for wood fibers. This finding could be attributed to the microstructural characteristics of the small Microfibrillar Angle and scarcity of pits in bamboo fibers. Furthermore, our results directly support the assumption that the widely used Oliver-Pharr analysis method in nanoindentation test significantly underestimates the longitudinal elastic modulus of anisotropic plant cell wall.
Hankun Wang - One of the best experts on this subject based on the ideXlab platform.
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Structural, chemical, and multi-scale mechanical characterization of waste windmill palm fiber (Trachycarpus fortunei)
Journal of Wood Science, 2020Co-Authors: Jing Li, Yan Yu, Xuexia Zhang, Hankun WangAbstract:This study investigated the structural, chemical, and multi-scale mechanical properties of windmill palm (Trachycarpus fortunei) leaf sheath fiber, which were frequently wasted. Significant variation was observed in fiber diameter and cross-sectional morphology among different layers in a single leaf sheath, whereas the chemical composition, relative crystallinity index, and the Microfibrillar Angle (MFA) of palm fibers were almost the same among different layers. Windmill palm fibers had low cellulose contents (34.70–35.5%), low relative crystallinity index (45.7–49.2%), and high MFA (38.8°–29.4°), resulting in low strength and modulus, but high failure strain under tensile load. The tensile fracture surface of windmill palm fibers was assessed through SEM studies and its ductile fracture was confirmed, which can potentially enhance the toughness of composites when used as reinforcement material. Nanoindentation was carried out among different leaf sheath layers, and the results showed the modulus and hardness values of windmill palm fibers are in the same range as other plant fibers. The experimental results may help guide selection of suitable reinforcing fibers for use in composites in different applications.
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The combined effects of initial Microfibrillar Angle and moisture contents on the tensile mechanical properties and Angle alteration of wood foils during tension
Holzforschung, 2017Co-Authors: Hankun Wang, Xuexia Zhang, Zixuan Yu, Yan YuAbstract:Abstract The combined effects of initial microfibril Angle (MFA) and moisture content (MC) on the longitudinal tensile properties of Masson pine (Pinus massoniana Lamb.) wood foils has been investigated. Synchrotron X-ray diffraction (XRDsyn) combined with a custom-built microtensile device was applied for in situ monitoring of the MFA alterations in the foils under different initial MFAs and MCs conditions. The results demonstrate that the tensile properties are highly negatively correlated to both MFA and MC. Furthermore, the tensile modulus is more sensitive to MC change than tensile strength. At a higher MFA, the sensitivity of the two mechanical indicators to MC alteration is enhanced.
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Variation of mechanical properties of single bamboo fibers (Dendrocalamus latiflorus Munro) with respect to age and location in culms
Holzforschung, 2014Co-Authors: Hankun Wang, Xiaojing An, Wanju Li, Hao Wang, Yan YuAbstract:Abstract There is a growing need to characterize the mechanical properties of single bamboo fibers with their high potential in commercial applications. In this paper, an improved microtensile technique has been applied to measure the tensile strength of fibers isolated from Ma bamboo (Dendrocalamus latiflorus Munro) as an important commercial bamboo species in China. The property variation with respect to the age and locations within a culm was in focus. Ma bamboo fibers had superior stiffness and strength data compared with those of softwood fibers. Four-year-old Ma bamboo fibers are stiffer and stronger than 1-year-old fibers. Their in-trunk variation is rather small both in radial and longitudinal directions. This is due to the relatively constant Microfibrillar Angle in bamboo culms. Accordingly, the large variations in the bulk mechanical properties of bamboo are mainly attributable to fiber distribution density in the culm rather than the fiber itself.
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Mechanical characterization of single bamboo fibers with nanoindentation and microtensile technique
Holzforschung, 2011Co-Authors: Yan Yu, Hankun Wang, Genlin Tian, Ge WangAbstract:More mechanical information on fibers is needed for better understanding of the complex mechanical behavior of bamboo as well as optimizing design of bamboo fiber based composites. In this paper, in situ imaging nanoindentation and an improved microtensile technique were jointly used to characterize the longitudinal mechanical behavior of fibers of Moso bamboo (Phyllostachys pubescens Mazei ex H. de Lebaie) aged between 0.5 and 4 years. These methods show that 0.5-year-old fibers have similar mechanical performances to their older counterparts. The average longitudinal tensile modulus and tensile strength of Moso bamboo fibers ranges from 32 to 34.6 GPa and 1.43 to 1.69 GPa, respectively, significantly higher than nearly all the published data for wood fibers. This finding could be attributed to the microstructural characteristics of the small Microfibrillar Angle and scarcity of pits in bamboo fibers. Furthermore, our results directly support the assumption that the widely used Oliver-Pharr analysis method in nanoindentation test significantly underestimates the longitudinal elastic modulus of anisotropic plant cell wall.
K. M. Bhat - One of the best experts on this subject based on the ideXlab platform.
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Mechanical properties and wood structure characteristics of 35-year old home-garden teak from wet and dry localities of Kerala, India in comparison with plantation teak
Journal of the Indian Academy of Wood Science, 2012Co-Authors: P. K. Thulasidas, K. M. BhatAbstract:Mechanical properties of teak wood grown in home-garden forestry and the anatomical factors influencing timber strength were investigated in comparison with that of a typical forest plantation. No significant differences were observed in modulus of elasticity and modulus of rupture with respect to wet, dry and plantation sites and the values are moderate compared with the standard teak. Where as, dry site home-garden teak exhibited higher compressive strength (MCS) parallel to grain (60.6 N/mm^2) and differed significantly between wet and plantation sites (P ≤ 0.05). The higher MCS value was correlated with higher air-dry density (691 kg/m^3) recorded coupled with thick fibre wall and smaller fibre lumen as elucidated by anatomical study. The Microfibrillar Angle also showed non-significant difference between the three localities (P = 0.05) and the value 12.5° was quite small to affect the timber strength adversely in its utilisation potential. The results of the present study revealed that farmer’s choice to fell homestead teak at short-rotation of 35-years is in no way affect the wood quality attributes such as density and strength.
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Characterisation of juvenile wood in teak
Wood Science and Technology, 2001Co-Authors: K. M. Bhat, P. B. Priya, P. RugminiAbstract:Juvenile wood properties are studied in a ring-porous tropical hardwood – teak ( Tectona grandis L. F), to assess the utilisation potential of short rotation timber. Compared to mature wood, it is characterised by wide rings, short fibres, small diameter, low vessel percentage, high cell wall, wide Microfibrillar Angle and relatively low or almost similar mechanical properties. While the average modulus of elasticity and modulus of rupture in juvenile wood are 85% and 82% respectively of the mature wood value, the longitudinal compression strength is similar. With relatively small fibrillar Angle of 15° and the scope for genetic selection of individual trees, teak juvenile wood has potential for desired dimensional stability. The segmented regression models and visual interpretation of radial patterns of variation in anatomical properties reveal that juvenility in plantation grown teak extends up to 15, 20–25 years depending on the property, growth rate and individual tree and plantation site. The fitted regression models, to explain the age-related variations in juvenile wood properties range from simple, linear to exponential, reciprocal and quadratic equations. Fibre length, Microfibrillar Angle, vessel diameter/percentage and ring width appear to be the best anatomical indicators of age demarcation between juvenile and mature wood, although maturation age often varies among the properties. The projected figures for proportion of juvenile wood in plantation grown teak at breast height are 80–100% and 25% at ages 20 and 60 years respectively.
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CAMBIAL ACTIVITY AND JUV ENLIE WOOD FORMATION IN TEAK
1998Co-Authors: K. M. BhatAbstract:One effective silvicultural tool for improving the teak timber supply is shortening rotation period of plantations. Growth in such managed plantations would be so rapid that rotations anticipated are as short as 20-30 years in contrast to the existing practice of 60-70 years. As the trees at that age contain higher proportion of juvenile wood, knowledge of growth periodicity of relatively young trees and the pattern of juvenile wood production is crucial for timber management in teak plantations. The specific objectives of the present study are: (a) to determine the growth (cambial) periodicity and influencing factors in juvenile wood production including false ring formation in teak (b) to determine the age at which teak trees stop producing juvenile wood and begin to form mature wood and (c) to evaluate the differences in size and proportion of different secondary xylem (wood) elements, Microfibrillar Angle, specific gravity and bending strength (Modulus of rupture) between the juvenile and mature wood. Cambial periodicity was followed for two consecutive annual cycles (during 1994 and 1995), in the trees marked in each plantation of four age groups from three different locations (Nilambur , Walayar and Peechi as Locations I, IIIand III respectively) of diverse environmental conditions in Kerala. To determine the age of demarcation between juvenile and mature wood, timber samples were collected from 65-yearold plantations located in Nilambur, Konni and Arienkavu. Cambial activity was influenced by the age of the tree. Cambium was active for longer period of the annual cycle in juvenile wood formation than in mature wood production of the trees. Pre-monsoon showers during March-April, influenced the cambial activity and broke dormancy earlier. Irrespective of age and location, a peak period of wood production was recorded during June-July, when the cambium was 15-20 layered, correlating with the highest amount of rain fall of the year. Narrowing of cambial zone was observed from September onwards; and by the time the cambium had attained dormancy during November-December, the zone was found to be reduced to 610 layers of radially flattened cells. Wider growth rings were produced in juvenile trees of 7and 13-year age groups and so is the amount growth ring. This is attributed to the prolonged period of cambial activity of juvenile trees. Thus the late onset of dormancy influenced the quality of wood as evidenced by a higher proportion of latewood in the growth ring. Artificial drought induction and field transplantations interrupted the active growth causing false ring formation in the juvenile wood of 2and 3-year-old seedlings. Insect defoliation in 8-yearold trees did not induce false ring formation while decreasing growth rate of the trees without affecting specific gravity, size and proportion of vessels and cell wall percentage. The data obtained from both crossdating of plantations and controlled experiments, including induced drought, showed that rain fall during dry period, drought during active growing season, polybag/field transplantation of seedlings are the important causative factors of frequent false ring formation in teak. This new information will be of particular interest to dendrochronologists in tree ring analysis. The observations on shorter duration of cambial activity in drier locality and drought/irrigation effects on cambial activity and wood formation will throw light on management strategies needed for commercial teak plantations. The age of demarcation between juvenile and mature wood in teak trees was found around 20-25 years depending on growth rate. The fast growing trees had a tendency to prolong the period of juvenile wood formation. The current finding on maturation age of wood formation, as 20-25 years, will be useful for plantation managers in fixing rotation cycles for production of desired wood quality or manipulation of juvenile wood proportion of the timber to be harvested. The juvenile wood in teak is characterised by wide growth rings, wide Microfibrillar Angle, small diameter and low percentage of vessels and high percentage of cell wall with short fibres as compared to mature wood. Because mechanical properties such as bending strength of slow grown trees and compression strength (parallel to grain) did not differ consistently between juvenile and mature wood, the former is not necessarily always inferior in timber strength to mature wood.
Yiqi Yang - One of the best experts on this subject based on the ideXlab platform.
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Fibers from Banana Pseudo-Stems
Innovative Biofibers from Renewable Resources, 2014Co-Authors: Narendra Reddy, Yiqi YangAbstract:One of the most ubiquitous fruits, banana is widely grown across the world. About 120–150 million tons of bananas are grown annually in the world, and it is the fourth most important food product in the world. However, the banana fruit only represents about 12 % of the weight of the plant and the stem; leaves and other parts are not generally edible. Therefore, efforts have been made to use banana leaves and stems for various nonfood applications including fiber production. Fibers are obtained from the pseudo-stem of the plant mostly by mechanical means. Full-fledged banana fiber production has been reported to be operational in several countries. Some of the products developed from banana fibers include textiles, paper, floor mats, and composites. In terms of properties, banana fibers have the typical composition of fibers obtained from lignocellulosic by-products and contain about 50 % cellulose, 17 % lignin, and 4 % ash [09Gui]. However, the composition of the banana fibers reported varies widely, and fibers with lignin content as high as 17 % have been reported [08Hab]. In addition to the stem, fibers have also been obtained from the leaf and rachis of the banana plant. Considerable variations in the tensile properties were observed for the fiber bundles obtained from the different parts and also depending on the method of extraction as seen in Table 7.1 [08Gan]. Tensile properties of the fibers obtained from the banana stems are similar to those of common lignocellulosic fibers such as jute, but the elongation is considerably lower than that of the coconut and palm (Borassus flabellifer) fibers. Low elongation of the banana fibers should mainly be due to the lower Microfibrillar Angle (11°) and relatively high % crystallinity [08Muk]. Banana fibers also appear to have a hollow center similar to that found in a few other natural cellulose fibers. Considerable variation in the tensile properties, especially elongation, was observed for fibers with various diameters (50–250 μm) as seen in Tables 7.1, 7.2, and 7.3 [10Ven]. In addition to the stems, fibers have also been obtained from the leaves of the banana plant. Typically, banana plants produce about 30 leaves as long as 2 m and 30–60 cm wide [07Bil]. Fibers obtained from banana leaves had about 26 % cellulose, 17 % hemicellulose, and 25 % lignin, but the fiber properties are not reported [07Bil]. A Switzerland-based company (Swicofil) advertises that it had developed fabrics from ring- and rotor-spun banana fibers. Ring-spun yarns in counts ranging from Ne 8/1 to 40/1 and rotor-spun yarns with counts (Ne) ranging from 8/1 to 30/1 were reported to be available in 100 % form and also as blends with cotton, modal, Tencel, and soy protein fibers. Banana fibers are reported to be available on the market for about US$0.43–0.81/kg compared to $0.15–0.60 for hemp and $0.15–$0.21/kg for flax.
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structure and properties of high quality natural cellulose fibers from cornstalks
Polymer, 2005Co-Authors: Narendra Reddy, Yiqi YangAbstract:We have developed a fiber extraction method that produces fibers from cornstalks with mechanical properties similar to that of the common textile fibers. The fiber extraction method developed results in partial delignification and produces fibers from cornstalks that are suitable for textile and other industrial applications. The structure of the fibers obtained was investigated using X-ray diffraction and scanning electron microscope. The structure and composition of the natural cellulose fibers obtained from cornstalks are different than that of the common bast fibers such as flax and kenaf. Tensile properties of the fibers were studied using an Instron tensile tester. This study found that cornstalk fibers have relatively lower percent crystallinity but similar Microfibrillar Angle as that of the common bast fibers. The structure and properties of cornstalk fibers indicate that the fibers are suitable for producing various textile products.
Patrick Navard - One of the best experts on this subject based on the ideXlab platform.
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Swelling and dissolution of cellulose, Part III: plant fibres in aqueous systems
Cellulose, 2008Co-Authors: Céline Cuissinat, Patrick NavardAbstract:Raw and refined flax, hemp, abaca, sisal, jute and ramie fibres are dipped into N -methylmorpholine N -oxide (NMMO)–water with various contents of water and into hydroxide sodium (NaOH)–water. The swelling and dissolution mechanisms of these plant fibres are similar to those observed for cotton and wood fibres. Disintegration into rod-like fragments, ballooning followed or not by dissolution and homogeneous swelling are all observed as for wood and cotton fibres, depending on the quality of the solvent. Balloons are not typical of wood and cotton and they seem to be present in all plant fibres. Another interesting result is that the helical feature seen on the balloon membrane is not related to the Microfibrillar Angle. Plant fibres are easier to dissolve than wood and cotton. This is not related to the molar mass of the cellulose chain. Raw plant fibres keeping most its non-cellulosic components do not show the formation of balloons.