The Effect of Fiber Geometry and Interfacial Properties on the Elastic Properties of Cementitious Nanocomposite Material

Ala G Abu Taqa,Nasser Al-Nuaimi,Rashid K Abu Al-Rub,Ahmed Senouci,Khaldoon A Bani-Hani

doi:10.1155/2015/283579

Ala G Abu Taqa, Nasser Al-Nuaimi + Show 3 more

Open Access

https://doi.org/10.1155/2015/283579

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Abstract

This paper investigates the elastic (Young’s) modulus of carbon Nanotube- (CNT-) reinforced cement paste using 3D and axisymmetric models using Abaqus software. The behavior of the CNT and the cement matrix was assumed to be fully elastic while the cohesive surface framework was used to model the interface. To investigate the effect of fiber waviness on the value of the elastic modulus, 3D models were developed assuming different distributions of fibers. The results obtained using the 3D model were compared to those obtained using the simplified three-phase axisymmetric model which consists of one single CNT aligned in the center of composite unit cell, an interface, and cement matrix. A parametric study was then carried out using the axisymmetric model to study the role of the interface in the composite elastic modulus without accounting for the presence of the interfacial transition zone (ITZ or interphase). The results showed that the CNTs waviness significantly reduced their reinforcing capability in the cement paste. On the other hand, the results obtained using the axisymmetric model were found to be in good agreement with those obtained using the 3D model. Moreover, the results of the parametric study showed that the interface properties significantly affect the composite elastic modulus and alter its behavior.

Highlights

Since their discovery in 1990s [1], CNTs have shown an excellent potential to be used in composites because of their special physical properties resulting from the symmetry of their structure
CNTs occur as single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs)
The average diameter of an individual SWNT is on the order of 1 nm whereas the average diameter of an individual MWNT is on the order of 10 nm

Summary

Introduction

Since their discovery in 1990s [1], CNTs have shown an excellent potential to be used in composites because of their special physical properties resulting from the symmetry of their structure. On the other hand, modeling the stiffness and strength of the nanocomposite cement paste needs to consider the mechanical properties of the region surrounding the CNT which significantly influence the bulk composite properties including the elastic modulus. This region is characterized by two zones, namely, interfacial transition (ITZ or interphase) and interface. The second objective consists of conducting a parametric study to explore the effect of the interfacial properties (namely, initial stiffness, cohesive shear strength, and maximum allowable slip or cohesive energy) on the elastic response of the nanocomposite cement using the axisymmetric unit cell model for a single aligned CNT embedded in the cement matrix. This work can be extended to incorporate the plasticity and damage behavior of the cement paste

Modeling and Assumptions

Part B

Analytical Method

Parametric Study

Conclusions