Axial-Compressive Behavior, Including Kink-Band Formation and Propagation, of Single<i>p</i>-Phenylene Terephthalamide (PPTA) Fibers

Grujičić, M.; Ramaswami, S.; Snipes, J. S.; Yavari, R.; Yen, Chian-Fong; Cheeseman, B. A.

doi:10.1155/2013/329549

Cited by 20 publications

(15 citation statements)

References 28 publications

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“…Grujicic et al 56,[62][63][64][65] reported that defect's type, size and concentration are sensitive functions of the PPTA fiber fabrication (polymer synthesis, dope preparation and spinning process) -which are summarized in the present review in section 2.…”

Section: Structural Defectsmentioning

confidence: 95%

“…An outstanding analysis of PPTA fibers at multi scale levels is investigated by Grujicic et al 56,[62][63][64][65] . The computational investigations properly described the material models which are used to achieve the material (PPTA) behaviour at the length-scale levels from chemical structure (atoms) to composite structure (laminate) with brief description in eight levels.…”

Section: Ppta Computational Modellingmentioning

confidence: 99%

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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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Section: Structural Defectsmentioning

confidence: 95%

Section: Ppta Computational Modellingmentioning

confidence: 99%

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

et al. 2014

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“…For example, studies have been performed to predict the ideal molecular geometry and chain conformations [13,74], elastic moduli [38,72], and compressive failure due to chain buckling [37]. The more recent work of Grujicic et al [20,21,22,24,23,25] represents the most comprehensive set of studies to date. These studies focused on modeling various defect patterns and impurities, as well as tensile, torsion, and compressional loading, and the resulting elastic moduli and axial strength of PPTA crystals.…”

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confidence: 99%

Molecular Dynamics Modeling of PPTA Crystals in Aramid Fibers

Mercer

2016

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In this work, molecular dynamics modeling is used to study the mechanical properties of PPTA crystallites, which are the fundamental microstructural building blocks of polymer aramid bers such as Kevlar. Particular focus is given to constant strain rate axial loading simulations of PPTA crystallites, which is motivated by the rate-dependent mechanical properties observed in some experiments with aramid bers. In order to accommodate the covalent bond rupture that occurs in loading a crystallite to failure, the reactive bond order force eld ReaxFF is employed to conduct the simulations.Two major topics are addressed: The rst is the general behavior of PPTA crystallites under strain rate loading. Constant strain rate loading simulations of crystalline PPTA reveal that the crystal failure strain increases with increasing strain rate, while the modulus is not aected by the strain rate. Increasing temperature lowers both the modulus and the failure strain. The simulations also identify the CN bond connecting the aromatic rings as weakest primary bond along the backbone of the PPTA chain. The eect of chain-end defects on PPTA micromechanics is explored, and it is found that the presence of a chain-end defect transfers load to the adjacent chains in the hydrogen-bonded sheet in which the defect resides, but does not inuence the behavior of any other chains in the crystal. Chain-end defects are found to lower the strength of the crystal when clustered together, inducing bond failure via stress concentrations arising from the load transfer to bonds in adjacent chains near the defect site. The second topic addressed is the nature of primary and secondary bond failure in crystalline PPTA. Failure of both types of bonds is found to be stochastic in nature and driven by thermal uctuations of the bonds within the crystal. A model is proposed which uses reliability theory to model bonds under constant strain rate loading as components with time-dependent failure rate functions. The model is shown to work well for predicting the onset of primary backbone bond failure, as well as the onset of secondary bond failure via chain slippage for the case of isolated non-interacting chain-end defects.

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“…Examination of the results reported in Tables 2 -fibril axial-strength probability density function; and (b) the corresponding cumulative distribution function determined in the present work using molecular-type computational analyses. and σ 1 are found to be nearly equal to their fibril counterparts; (ii) the fiber transverse normal stiffness, E 22 =E 33 , is found to be nearly equal to the more compliant E 33 fibril modulus; and (iii) All three shear moduli G 12 , G 13 and G 23 are found to be nearly equal to the same value, the value which is controlled by the compliant PPTA inter-sheet sliding resistance (i.e. G 12 of the fibrils); and (e) To assess the yarn-level stiffness and strength properties from the known fiber properties, additional effects arising from the fiber-twist-induced inter-fiber friction had to be taken into account.…”

Section: Fibrils Fibers and Yarns Figures 1(e)-(g)mentioning

confidence: 93%

“…The resulting defects can also degrade mechanical properties of the PPTAbased materials, and their effect has to be accounted for in the analysis of the ballisticprotection resistance of the PPTA-based materials. To address this problem, a series of allatom and coarse-grained molecular-level computational analyses is carried out in the present work [11][12][13]. Specifically, the effect of the preludial handling-induced deformation modes such as fiber/yarn transverse compression due to inter-yarn contacts, fiber/yarn twist/axialcompression, and fiber/yarn bending (encountered primarily in warp yarns) and the associated formation of kink-bands has been investigated.…”

Section: Effect Of Fiber-/yarn-handling-induced Defects On Ppta-fibermentioning

confidence: 99%

Multi-length Scale Material Model Development for Armorgrade Composites

Grujičić¹

2014

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The present work was focused on establishing microstructure/property relationships in p-phenylene terephthalamide (PPTA) based materials and structures. A multi-length-scale computational approach has been developed in order to identify and quantify the contribution of various microstructural features and processes, at different lengthscales, to the macroscopic-level ballistic-penetration resistance of PPTA-based fabric or PPTA-fiber-reinforced polymer-matrix composites. Specifically, the role of various material-synthesis-/fiber-processing-induced defects, as well as defects induced during the weaving process, was investigated. The results obtained clearly revealed that The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggesstions for reducing this burden, ABSTRACT Multi-length Scale Material Model Development for Armor-grade Composites Report TitleThe present work was focused on establishing microstructure/property relationships in p-phenylene terephthalamide (PPTA) based materials and structures. A multi-length-scale computational approach has been developed in order to identify and quantify the contribution of various microstructural features and processes, at different length-scales, to the macroscopic-level ballistic-penetration resistance of PPTA-based fabric or PPTA-fiber-reinforced polymer-matrix composites. Specifically, the role of various material-synthesis-/fiber-processing-induced defects, as well as defects induced during the weaving process, was investigated. The results obtained clearly revealed that both the static mechanical material properties such as stiffness and strength, and the dynamic-impact properties such as V50, are affected by the type and the concentration of various defects. Lastly, it was demonstrated that in order to construct a high-fidelity continuum-level PPTA-based material constitutive model, the role of the material microstructure (including defects) at different length-scales must be taken into account. (a) Papers published in peer-reviewed journals (N/A for none)Enter List of papers submitted or published that acknowledge ARO support from the start of the project to the date of this printing. List the papers, including journal references, in the following categories:

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Axial-Compressive Behavior, Including Kink-Band Formation and Propagation, of Singlep-Phenylene Terephthalamide (PPTA) Fibers

Cited by 20 publications

References 28 publications

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

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

Molecular Dynamics Modeling of PPTA Crystals in Aramid Fibers

Multi-length Scale Material Model Development for Armorgrade Composites

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