Hydrothermal aging mechanisms of aramid fibers via synchrotron small‐angle X‐ray scattering and dynamic thermal mechanical analysis

Li, Changsheng; Zhan, Mao-Sheng; Huang, Xiaoguang; Zhou, Hong; Li, Yan

doi:10.1002/app.38419

Cited by 17 publications

(14 citation statements)

References 30 publications

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“…Besides, numerous experimental studies or recent works on molecular‐level computations done by Grujicic et al have reported on the complexity of the hierarchical microstructure of the Kevlar fiber. The manufacturing process implies local gradient of shear rates and also complex kinetics of both cooling and solvent evaporation that modify the structure at the fiber diameter scale.…”

Section: Introductionmentioning

confidence: 99%

Multiaxial mechanical behavior of aramid fibers and identification of skin/core structure from single fiber transverse compression testing

Wollbrett-Blitz

Joannès

Bruant

et al. 2015

J. Polym. Sci. Part B: Polym. Phys.

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International audienceThe transverse and longitudinal mechanical properties of aramid fibers like Kevlar™ 29 (K29) fibers are strongly linked to their highly oriented structure. Mechanical characterization at the single fiber scale is challenging especially when the diameter is as small as 15 µm. Longitudinal tensile tests on single K29 fibers and single fiber transverse compression test (SFTCT) have been developed. Our approach consists of coupling morphological observations and mechanical experiments with SFTCT analysis by comparing analytical solutions and finite element modeling. New insights on the analysis of the transverse direction response are highlighted. Systematic loading/unloading compression tests enable to experimentally determine a transverse elastic limit. Taking account of the strong anisotropy of the fiber, the transverse mechanical response sheds light on a skin/core architecture. More importantly, results suggest that the skin of the fiber, typically representing a shell of one micrometer in thickness, has a transverse apparent modulus of 0.2 GPa. That is around more than fifteen times lower than the transverse modulus of 3.0 GPa in the core. By comparison, the measured longitudinal modulus is about 84 GPa. The stress distribution in the fiber is explored and the critical areas for damage initiation are discussed

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Section: Introductionmentioning

confidence: 99%

Multiaxial mechanical behavior of aramid fibers and identification of skin/core structure from single fiber transverse compression testing

Wollbrett-Blitz

Joannès

Bruant

et al. 2015

J. Polym. Sci. Part B: Polym. Phys.

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“…Voids affect the mechanical properties of the fibers, namely, they tend to decrease the tensile strength 58,59,131 . The PPTA fabrics capacity to absorb water and ability to take up dyestuff are very low compared to other fabrics 130 .…”

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confidence: 99%

Microstructural developments of poly (p-phenylene terephthalamide) fibers during heat treatment process: a review

et al. 2014

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Poly (p-phenylene terephthalamide) fibers prepared by wet or dry-jet wet spinning processes have a notable response to very brief heat treatment (seconds) under tension. The modulus of the as-spun fiber can be greatly affected by the heat treatment conditions (temperature, tension and duration). The crystallite orientation and the fiber modulus will increase by this short-term heating under tension. Poly (p-phenylene terephthalamide) fibers have a very high molecular orientation (orientation angle 12-20°). Kevlar  and Twaron  fibers are poly (p-phenylene terephthalamide) fibers. This review reports for PPTA fibers the heat treatment techniques, devices and its process conditions. It reports in details the structural relationships between the fiber properties which are influenced by the heat treatment process. In particular, focused deeply on the effect of the crystal structure and the morphology of the fibers on the mechanical properties of PPTA fibers.

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“…As a result, hydrothermal aging has become one of the most important mechanisms threatening the structural integrity of GFRP composites . Numerous experimental studies and daily experience have demonstrated that long‐term exposure to elevated temperatures and high moistures inevitably leads to localized stresses . Nonuniform stress distributions greatly affect the initiation and propagation of microcracks and thus degrade the performance of GFRP composites .…”

Section: Introductionmentioning

confidence: 99%

Improved hydrothermal aging performance of glass fiber‐reinforced polymer composites via silica nanoparticle coating

Zhang

2019

J of Applied Polymer Sci

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The long-term exposure to a hot and humid environment severely damages the bonding integrity of fiber-reinforced polymer composites and thus significantly degrades their mechanical performances. In this work, we aim to develop an improvement procedure for effectively enhancing the bonding strength in glass fiber-reinforced polymers (GFRPs). Glass fibers were coated with a thin layer of silica nanoparticles of different concentrations by the use of the evaporative deposition method. Micromorphological comparisons in terms of scanning electron microscope imaging demonstrate significant improvements on the surface roughness of glass fibers. With the coated glass fibers, GFRP composite laminates were designed, molded through the vacuum-assisted resin infusion technique, and experimentally tested for quantitatively studying their hydrothermal aging performance. The water absorption tests conducted for three exposure temperatures suggest that both the water diffusion rate and the equilibrium water content can be effectively reduced due to the introduction of the silica coating. With increased exposure temperatures, however, the desired reductions become much less significant. A so-called water-channel diffusion mechanism along fiber/resin interfaces was proposed to explain the coupling effects of silica coating and exposure temperature. Reductions of water diffusion rate and equilibrium water content were expected to slow down the hydrothermal aging performance of GFRPs. For this purpose, both uniaxial tensile test and three-point bending test were subsequently performed on GFRP specimens that have been subjected to different coating concentrations, exposure temperatures, and exposure durations. When compared with untreated GFRP specimens, both experiments demonstrate that the residual strength and stiffness can be effectively promoted through coating a thin layer of silica nanoparticles on glass fiber surfaces.

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Hydrothermal aging mechanisms of aramid fibers via synchrotron small‐angle X‐ray scattering and dynamic thermal mechanical analysis

Cited by 17 publications

References 30 publications

Multiaxial mechanical behavior of aramid fibers and identification of skin/core structure from single fiber transverse compression testing

Multiaxial mechanical behavior of aramid fibers and identification of skin/core structure from single fiber transverse compression testing

Microstructural developments of poly (p-phenylene terephthalamide) fibers during heat treatment process: a review

Improved hydrothermal aging performance of glass fiber‐reinforced polymer composites via silica nanoparticle coating

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