Nanoindentation creep of nonlinear viscoelastic polypropylene

Peng, Guangjian; Ma, Yi; Feng, Yihui; Huan, Yong; Qin, Chunjie; Zhang, Taihua

doi:10.1016/j.polymertesting.2015.02.006

Cited by 17 publications

(12 citation statements)

References 20 publications

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“…To study cell wall creep behavior from the nanoindentation measurements, load displacement and time data were obtained during the holding step of the test 44 . This approach was consistent with the constant load method reported in many studies [45][46][47] . Figure 9 shows the maximum indent depths of the heat-treated wood samples.…”

Section: Resultssupporting

confidence: 90%

Comparison of the chemical and micromechanical properties of Larix spp. after eco-friendly heat treatments measured by in situ nanoindentation

Dong

Wang

2020

Sci Rep

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Heat treatment is a green, environmentally friendly and mild pyrolysis process that improves the dimensional stability and durability of wood. in this study, Larix spp. Samples were heated at 180 °C and 210 °C for 6 h with nitrogen, air or oil as heat-conducting media. The influence of high-temperature heat treatment on the microstructure, chemical components, and micromechanical properties was investigated. the mass loss rate increased with increasing temperature, and the degradation of wood components resulted in cracks in the cell walls. Samples treated with air showed more cracks in cell walls than were observed in the cells walls of wood treated with the other heat-conducting media. the hardness of the cell walls increased after all heat treatments. in addition, the results showed that heat treatment reduced creep behavior compared to that of untreated wood.Larix spp., an appealing source of wood products in China, are massively planted due to their excellent adaptability, rapid growth and long growth cycle. However, the poor dimensional stability and durability of these species severely limits their scope of applications 1 . Recently, several industrial-scale and environmentally friendly heat treatment processes were applied to solve these problems without the addition of chemical agents, including Retification ® , Thermowood ® , Plato Wood ® , OHT ® and so on 2 . The equilibrium moisture content (EMC) and hygroscopicity of wood decreased markedly after heat treatment, which could prevent several appearance defects, such as blue staining and white rot. Moreover, after appropriate heat treatment, wood durability can be enhanced significantly, which extends the life cycle of the wood products accordingly 3 .Heat treatment, a green process, alters the chemical composition of wood through pyrolysis of the hemicellulose and part of the amorphous cellulose, evaporation of extractives and condensation of byproducts 4,5 . This procedure caused a higher degree of cellulose crystallinity, lower hydrophilicity, improved color, and better dimensional stability and durability of wood 6,7 . The mechanical properties of heat-treated wood, including compression strength, modulus of elasticity, modulus of rupture, brittleness, impact bending and so on, have been extensively reported on 8 . Previous studies have shown that the elemental composition (C/O ratio or C content) is a useful marker for predicting the level or extent of heat treatment 9,10 . These markers can also be effectively used for the prediction of decay durability and mechanical properties of heat-treated wood. Furthermore, the mass loss rate is also a notable feature in heat treatment and is a parameter used for quality control 11,12 . It has been massively proven that chemical transformations of compounds and extractives in wood cell walls is caused by heat treatment 13,14 . These transformations are mainly dependent on the wood species, treatment duration, heat temperature and so on 15-17 .If wood heat treatment involves air on an industrial scale, a lowe...

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Section: Resultssupporting

confidence: 90%

Comparison of the chemical and micromechanical properties of Larix spp. after eco-friendly heat treatments measured by in situ nanoindentation

Dong

Wang

2020

Sci Rep

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“…v is the Poisson's ratio of the sample, which is assumed to be 0.38 (measured by tensile experiments). When the Berkovich indenter is selected to indent the specimen under constant load, the creep compliance, J(t), can be obtained from the following formula [34]…”

Section: Nanoindentation Testmentioning

confidence: 99%

Characterization of mechanical properties of epoxy/nanohybrid composites by nanoindentation

Zhang

Qian

et al. 2020

Nanotechnology Reviews

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AbstractThe carbon nanofibers and molybdenum disulfide (CNF-MoS2) nanohybrid material was fabricated and incorporated into epoxy resin to form the nanocomposite coating. Firstly, microstructure observation shows that each CNF was uniformly wrapped up with MoS2 nanosheets, and the nanohybrids were well dispersed in the coating. Then, nanoindentation experiments were carried out to explore the effect of the CNF-MoS2 nanohybrids on the mechanical properties of the epoxy resin coating. The results demonstrate that elastic modulus, hardness and creep deformation resistance of the CNF-MoS2 epoxy resin coating are greatly increased in comparison with both pure epoxy resin and MoS2 epoxy resin coatings. Finally, the underlying mechanism of high-performance tribological behavior of the nanocomposites is analyzed accordingly. It can be concluded that the wrapped structure with MoS2 sheets growing on the surface of CNF increases the contact area and reduces the friction coefficient of the composite coating, while the wear resistance of the nanocomposite coating is also greatly improved due to the superior high hardness of CNF.

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“…To describe the viscoelastic behavior of polymers and their nanocomposites and to obtain the corresponding time-dependent displacement or creep compliance function, the concept of hereditary integral operator and the elastic-viscoelastic correspondence principle [63][64][65][66] have been applied, and different approaches were developed to model the indentation into a linearly viscoelastic half space [20,35,39,[49][50][51][52][53]56,67].…”

Section: Creep Compliance Functionmentioning

confidence: 99%

“…A study by Kato et al [50] proposed a three-cycle indentation test to investigate whether the plastic deformation occurs or not after the first cycle. Peng et al [51][52][53] introduced the so-called revised step-hold method, which assumes that during the fast loading the elastic-plastic deformation is dominant and the viscoelastic deformation can be neglected, and only the viscoelastic deformation occurs during the holding stage. The revised load-depth curves obtained through a three-step procedure, i.e., a step-hold-unload indentation method, were used in the phenomenological model to calculate the shear creep compliance [51][52][53].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Viscoelastic Behavior of Polypropylene/Carbon Nanotube Nanocomposites by Instrumented Indentation

2020

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In this work, the viscoelastic behavior of polypropylene (PP)/multi-walled carbon nanotube (MWCNT) nanocomposites was investigated by indentation testing and phenomenological modeling. Firstly, indentation tests including two-cycle indentation were carried out on PP/MWCNT nanocomposite with three MWCNT loadings (1, 3 and 5 wt %). Next, the Maxwell–Voigt–Kelvin model coupled with two-cycle indentation tests was used to predict the shear creep compliance function and the equivalent indentation modulus. The indentation hardness and elastic modulus of the PP/MWCNT nanocomposites extracted based on the Oliver and Pharr method were compared with the equivalent indentation modulus predicted based on the Maxwell–Voigt–Kelvin mode. The experimental results indicated that the addition of nanotubes into the polypropylene has a positive effect on the micro-mechanical properties of PP/MWCNT nanocomposites. Indentation hardness and elastic modulus increased significantly with increasing MWCNT loading. The creep resistance at the micro-scale of the PP/MWCNT nanocomposites improved with the addition of MWCNTs, with creep displacement reduced by up to 20% by increasing the carbon nanotube loading from 1 to 5 wt %. The Maxwell–Voigt–Kelvin model with three and five Voigt–Kelvin units accurately predicted the shear creep function and its change with increasing MWCNT loading. However, the equivalent indentation modulus was found to be sensitive to the number of Voigt–Kelvin units: the more Voigt–Kelvin units, the better the model predicts the equivalent indentation modulus.

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Nanoindentation creep of nonlinear viscoelastic polypropylene

Cited by 17 publications

References 20 publications

Comparison of the chemical and micromechanical properties of Larix spp. after eco-friendly heat treatments measured by in situ nanoindentation

Comparison of the chemical and micromechanical properties of Larix spp. after eco-friendly heat treatments measured by in situ nanoindentation

Characterization of mechanical properties of epoxy/nanohybrid composites by nanoindentation

Analysis of Viscoelastic Behavior of Polypropylene/Carbon Nanotube Nanocomposites by Instrumented Indentation

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