Study on the Mechanical Properties of Carbon Nanotube Coated‒Fiber Multi-Scale (CCFM) Hybrid Composites

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The influence of carbon nanotube coated-carbon fibers on thermal residual stresses of Multi-Scale hybrid composites: Analytical approach

The effect of carbon nanotube (CNT) coated-carbon fibers on thermal residual stresses of multi-scale hybrid composites is assessed employing analytical approach. The model comprises carbon fiber, coating region and surrounding matrix, in which the coating region around core fiber encompasses CNTs and matrix. Considering three configurations of grown CNTs on the fiber surface including axially, radially and randomly oriented, the mechanical properties of various coating regions are acquired employing the Eshelby–Mori–Tanaka method in conjunction with an equivalent continuum approach. Utilizing the total energy minimization method, the closed-form solution of the thermal residual stresses of hybrid composite is obtained. The results disclose a noteworthy influence of CNT–coating on the reduction of interfacial stresses which precludes debonding at interface and attenuates the effect of thermal expansions mismatch between the carbon fiber and matrix. Furthermore, the results demonstrate that unlike radially oriented CNTs, the existence of axially and randomly oriented CNTs at the coating region has a remarkable diminishing effect on residual interfacial stresses. It is also shown that increasing the coating thickness leads to reduction of maximum interfacial stresses even at a constant CNT volume fraction. A close agreement exists between predicted outcomes by the proposed analytical approach and published data in the literature

A study on fracture behavior of semi-elliptical 3D crack in claypolymer nanocomposites considering interfacial debonding

In the current research, the influence of clay platelet on crack characteristics of fully exfoliated clay/polymer matrix is scrutinized. A multi-scale 3-D finite element model comprising of four phases as clay platelet, non-perfect bond interactions, interphase region and surrounding matrix is constructed to investigate semi-elliptical matrix crack properties, as a nano-notch, subjected to fracture mode I. Subsequently, the strain energy release rate is acquired in terms of J-integral parameter considering the location and dimension, geometrical variables and modeling strategy. The results imply on the pronounced effect of clay debonding on crack behavior which leads to local stiffness reduction. Furthermore, interphase characteristics such as thickness and elastic modulus, have significant influences on the critical energy release rate. The results are consistent with published literatures and the model can be invoked as a viable tool to investigate the fracture behaviors of clay/polymer nanocomposites