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Characterization of Quasi-static Mechanical Properties of Polymer Nanocomposites Using a New Combinatorial Approach

Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA

Arun K. Kota

Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA

Hugh A. Bruck

Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA, bruck{at}umd.edu

Recently, it has become very important to rapidly characterize the processing-structure-property relationships in polymer nanocomposites using minimal quantities of expensive nanoscale fillers. To address this issue, we present a new combinatorial approach developed for characterizing the variation in mechanical properties as a function of filler composition in polymer nanocomposites. The fundamental basis for the combinatorial approach is the generation of compositional gradients through transient operation of a twin-screw extruder (TSE). The compositional variation in the specimens could be rapidly predicted a priori using a convolution process model and was verified a posteriori using pycnometry measurements and thermogravimetric analysis. To characterize the quasi-static mechanical properties along the compositional gradient, sub-scale specimens that are proportional in size to ASTM type I specimens but with a gage section that is a factor of 10 smaller, were tested using a microtensile tester. The properties of the sub-scale specimens processed in the combinatorial approach correlated well with those of sub-scale specimens of similar composition processed in steady-state, thereby indicating that the properties were unaffected by the transient operation of the TSE. Furthermore, the quasi-static mechanical properties of the steady-state ASTM type I standard specimens were compared with those of the sub-scale specimens to determine the effect of specimen size. The results were nearly identical, except the increased size of the ASTM type I standard specimens resulted in substantial reductions in ductility that are most likely due to an increase in the number of processing-related defects.

Key Words: combinatorial materials science • quasi-static mechanical properties • polymer nanocomposites • twin-screw extrusion • sub-scale ASTM type I specimens • microtensile testing.

This version was published on October 1, 2009

Journal of Composite Materials, Vol. 43, No. 22, 2587-2598 (2009)
DOI: 10.1177/0021998309345311


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