The Effect of Plain-Weaving on the Mechanical Properties of Warp and Weft P-Phenylene Terephthalamide (PPTA) Fibers/Yarns
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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Coarse-grained molecular staticsdynamics methods are first used to investigate degradation in the PPTA fiberyarn tensile strength, as a result of the prior compressive or tensile loading. PPTA fibersyarns experience this type of loading in the course of a plain-weaving process, the process which is used in the fabrication of ballistic fabric and flexible armor. The more common all-atom molecular simulations were not used to assess strength degradation for two reasons a the size of the associated computational domain rendering reasonable run-times would be too small and b modeling of the mechanical response of multi-fibril PPTA fibers could not be carried out again due to the limited size of the computational domain. However, all-atom simulations were used to a define the coarse-grained particles referred to as beads and b parameterize various components of the beadbead force-field functions. In the second portion of the work, a simplified finite-element analysis of the plain-weaving process is carried out in order to assess the extent of tensile-strength degradation in warp and weft yarns during the weaving process. In this analysis, a new material model is used for the PPTA fibersyarns. Specifically, PPTA is considered to be a linearly elastic, transversely isotropic material with degradable longitudinal- tensile strength and the longitudinal Young s modulus. Equations governing damage and strengthstiffness degradation in this material model are derived and parameterized using the coarse-grained simulation results. Lastly, the finite-element results are compared with their experimental counterparts, yielding a decent agreement.
- Numerical Mathematics