Date: 15 Apr 2011

The Role of Interface and Reinforcement in the Finite Deformation Response of Polyurethane-Montmorillonite Nanocomposites

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Abstract

Nanoscale control over the structures is critical in designing nanocomposites with advanced properties. Structural parameters such as interface and volume fraction of reinforcement have tremendous effects on the mechanical properties of the nanocomposites, yet have proven difficult to control uniformly and consistently. Here we investigate the effect of reinforcement and interface on the finite deformation response of polyurethane (PU-) montmorillonite (MTM) nanocomposites at low and high strain rates. The multilayered PU-MTM nanocomposites, with alternate layers of PU and MTM, were manufactured using an exponential layer-by-layer (e-LBL) manufacturing technique. The systematic variation in MTM nanoparticle was obtained by either replacing several layers of MTM by polyacrylic acid (PAA) or by varying the thickness of PU layer. The interface was altered by replacing MTM layers by PAA. The deposition of PAA resulted in the formation of a complex polymer layer due to its diffusion through PU layer. The nanocomposites demonstrated an increasing yield strength and stiffness with increased strain rate and MTM volume fraction. The weaker interface interaction between the polymer and MTM nanoparticles resulted in a decreased yield strength and stiffness. The design parameters that will result in structures with optimum mechanical properties will be demonstrated.