Filament-Level Modeling of Aramid-Based High-Performance Structural Materials

Abstract

Molecular statics and molecular dynamics are employed to study the effects of various microstructural and topological defects (e.g., chain ends, axial chain misalignment, inorganic solvent impurities, and sheet stacking faults) on the strength, ductility, and stiffness of p-phenylene terephthalamide (PPTA) fibers/ filaments. These fibers can be considered as prototypes for advanced high strength/high-stiffness fibers like Kevlar Ò , Twaron Ò , New Star Ò , etc. While modeling these fibers, it was taken into account that they are essentially crystalline materials consisting of stacks of sheets, with each sheet containing an array of nearly parallel hydrogen-bonded molecules/chains. The inter-sheet bonding, on the other hand, was considered as mainly being of van der Waals or p-electron character. The effects of various deviations of the PPTA fiber structure from that of the perfectly crystalline structure (i.e., microstructural/topological defects) on the materialÕs mechanical properties are then considered. The results obtained show that while the presence of these defects decreases all the mechanical properties of PPTA fibers, specific properties display an increased level of sensitivity to the presence of certain defects. For example, longitudinal tensile properties are found to be most sensitive to the presence of chain ends, in-sheet transverse properties to the presence of chain misalignments, while cross-sheet transverse properties are found to be most affected by the presence of sheet stacking faults.

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

“…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.…”

“…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.…”

Molecular Dynamics Modeling of the Effect of Axial and Transverse Compression on the Residual Tensile Properties of Ballistic Fiber

“…The effect of AC and TC deformation modes on the fiber tensile failure strength has not been studied extensively. There are few atomistic simulations studies [20][21][22][23][24][25] that focused on the elastic and strength properties of Kevlar ® and PE crystal. Rutledge et al [20] have determined the elastic properties of Kevlar ® crystal through atomistic simulations.…”

“…Rutledge et al [20] have determined the elastic properties of Kevlar ® crystal through atomistic simulations. Grujicic et al [21,22] studied the properties of Kevlar ® filament using non-reactive force field COMPASS (Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies) [26]. In one study [21], they investigated the effects of microstructural and topological defects such as chain ends, inorganic-solvent impurities, chain misalignments, and sheet stacking faults on the strength, ductility, and stiffness of PPTA filament.…”

“…Grujicic et al [21,22] studied the properties of Kevlar ® filament using non-reactive force field COMPASS (Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies) [26]. In one study [21], they investigated the effects of microstructural and topological defects such as chain ends, inorganic-solvent impurities, chain misalignments, and sheet stacking faults on the strength, ductility, and stiffness of PPTA filament. In another study [22], they investigated the effect of prior AC and torsion on the axial tensile properties of Kevlar ® filament.…”