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Abstract
Effects of bi-axial stretching induced reorientation of graphene platelets (GPLs) on the Young’s modulus of GPL/polymer composites is studied by Mori-Tanaka micromechanics model. The dispersion state of the GPLs in polymer matrix is captured by an orientation distribution function (ODF), in which two Euler angles are used to identify the orientation of the GPLs. Compared to uni-axial stretching, the increase of the stretching strain in the second direction enhances the re-alignment of GPL fillers in this direction while it deteriorates the re-alignment of the fillers in the other two directions. Comprehensive parametric study on the effects of the out-of-plane Young’s modulus, stretching strain, strain ratio, Poisson’s ratio and weight fraction and GPL dimension on the effective Young’s moduli of the composites in the three directions are conducted. It is found that the out-of-plane Young’s modulus has limited effects on the overall Young’s modulus of the composites. The second stretching enhances the Young’s modulus in this direction while it decreases the Young’s modulus in the other two directions. The results demonstrate the increase of Poisson’s ratio is favorable in increasing the Young’s modulus of the composites. GPLs with larger diameter-to-thickness ratio have better reinforcing effect on the Young’s modulus of GPL/polymer nanocomposites.
Highlights
Adding graphene and its derivatives to polymers as reinforcements to produce high performance composites and structures has stimulated a surge of scientific interest from various engineering fields [1,2,3,4,5,6]. Such interests stem from graphene and its derivatives’ excellent mechanical and physical properties and improved reinforcing effects compared to other carbon-based fillers, such as carbon fibers (CFs) and carbon nanotubes (CNTs)
This paper investigates the effects of bi-axial stretching induced re-orientation of graphene platelets (GPLs) on the
The Young’s modulus decreases of 19 and increases significantly in X1 and X3 directions, respectively, when the diameter-to-thickness16ratio is relatively small, i.e., dGPL /tGPL < 500. This indicates that GPLs with larger diameter-to-thickness larger diameter-to-thickness ratio have better reinforcing effects on the Young’s modulus of the ratio have better reinforcing effects on the Young’s modulus of the nanocomposites in the principle nanocomposites in the principle stretching direction
Summary
Adding graphene and its derivatives to polymers as reinforcements to produce high performance composites and structures has stimulated a surge of scientific interest from various engineering fields [1,2,3,4,5,6]. Equation (18) indicates that the ODF after stretching depends on the Poisson’s ratio of the composites, which relies on both the concentration and orientation of the GPL reinforcements. Taking the Poisson’s ratio as 0.5 in present for composites with certain polymers as matrix, i.e., rubber, it is well-accepted to adopt 0.5 as the work isPoisson’s for case ratio study to eliminate the effects of volume expansion, which results in reduction in filler’s due to their very limited compressibility.
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