Title: On the contribution of carbon nanotube deformation to piezoresistivity of carbon nanotube/polymer composites

A.I. Oliva-Avilés,
Centro de Investigación y de Estudios Avanzados, Unidad Mérida, Departamento de Física Aplicada, A.P. 73-Cordemex, 97310 Mérida, Yucatán, Mexico

F. Avilés,
Centro de Investigación Científica de Yucatán, Unidad de Materiales, Calle 43 No. 130 Col. Chuburná de Hidalgo, 97200 Mérida, Yucatán, Mexico

Gary Don Seidel,
Dept. of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, 228 Randolph Hall (0203) Blacksburg, VA 24061, USA

V. Sosa
Centro de Investigación y de Estudios Avanzados, Unidad Mérida, Departamento de Física Aplicada, A.P. 73-Cordemex, 97310 Mérida, Yucatán, Mexico

Composites Part B: Engineering -- 2013 -- Volume 47, pp. 200-206

Abstract
The change in electrical resistance due to mechanical deformation of carbon nanotube (CNT)/polymer composites can be rationalized in terms of two effects: (i) changes in the composite electrical resistivity due to changes in the CNT network configuration and (ii) deformation of the CNTs themselves. The contribution of CNT dimensional changes (ii) to the piezoresistivity of CNT/polymer composites is investigated here. An analytical model based exclusively on dimensional changes which describes the CNT change of electrical resistance in terms of its mechanical deformation is proposed. A micromechanics approach and finite element analysis are performed to correlate the macroscale composite strain to the individual CNT strain. The CNT change of electrical resistance is quantified for different matrix elastic moduli and CNT weight fractions. The CNT/polymer composite is also modeled as an effective continuum material in terms of both its electrical and mechanical responses so that the effect of dimensional changes on the global piezoresistivity can be investigated. Based on the modeling predictions and previous experimental results, it is estimated that the CNT change of resistance due to the macroscale composite strain is marginal (?5%) compared to the total composite change of resistance commonly measured in the laboratory, suggesting that the dominant effect in the piezoresistivity of CNT/polymer composites is the change in the CNT network configuration.

Key words: A. Polymer–matrix composites (PMCs); C. Finite Element Analysis (FEA); C. Micro-mechanics; Carbon nanotubes