Nanocomposite materials hold the power to revitalize and revolutionize the field of composite materials. Nanoscaled, even common materials can exhibit strikingly different material properties from the bulk counterparts. If these properties can be accessed at the bulk scale, not only can materials be better tailored to suit various applications, but the possibility of designing multi-functional materials expands exponentially. In this study, the Generalized Method of Cells (GMC) micromechanics model is used to model 3D nanoscale composite architecture, including an interfacial region between the included and matrix phases, and predict the effective viscoelastic properties of a gold nanorod, polymer matrix, nanocomposite. Scale is introduced by referencing the dimensions of the interface to those of the nanorods. Comparisons are made of micromechanical response based on volume fraction and number density, highlighting the scale effects resulting from the high surface area to volume ratio of nanoparticles. Effective composite viscoelastic properties were developed, for static creep, for varying interfacial elastic stiffnesses. These experiments suggest that an elastically stiff interface greatly increases the stiffness of the polymer in response to an ‘instantaneous’ step load, reduces the rapid creep response, and results in a rapid leveling off of the time-dependent strain curves. The response of the composite to increasing stiffness of the interface region eventually reaches a plateau or threshold value, where further increases in the stiffness of the interface produces negligible increases in stiffness, or further reduction in creep response.

No abstract

No abstract

No abstract

A comprehensive all-atom molecular-level computational investigation is carried out in order to identify and quantify: (i) the effect of prior longitudinal-compressive or axial-torsional loading on the longitudinaltensile behavior of p-phenylene terephthalamide (PPTA) fibrils/fibers; and (ii) the role various microstructural/topological defects play in affecting this behavior. Experimental and computational results available in the relevant open literature were utilized to construct various defects within the molecular-level model and to assign the concentration to these defects consistent with the values generally encountered under ''prototypical'' PPTA-polymer synthesis and fiber fabrication conditions. When quantifying the effect of the prior longitudinal-compressive/axial-torsional loading on the longitudinal-tensile behavior of PPTA fibrils, the stochastic nature of the size/potency of these defects was taken into account. The results obtained revealed that: (a) due to the stochastic nature of the defect type, concentration/number density and size/potency, the PPTA fibril/fiber longitudinal-tensile strength is a statistical quantity possessing a characteristic probability density function; (b) application of the prior axial compression or axial torsion to the PPTA imperfect single-crystalline fibrils degrades their longitudinal-tensile strength and only slightly modifies the associated probability density function; and (c) introduction of the fibril/fiber interfaces into the computational analyses showed that prior axial torsion can induce major changes in the material microstructure, causing significant reductions in the PPTA-fiber longitudinal-tensile strength and appreciable changes in the associated probability density function.