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

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Prediction of mechanical properties of carbon nanotube‒carbon fiber reinforced hybrid composites using multi-scale finite element modelling

The mechanical properties of unidirectional carbon nanotube (CNT)‒carbon fiber (CF) reinforced hybrid composites are scrutinized. Due to lack of comprehensive model, a 3D multi-scale model considering debonding damage is developed, covering from nano-to macro-scale. Considering three different configurations of grown CNT’s on the fiber surface, the interfacial behavior is investigated. The results reveal that: (I) an extraordinary influence of CNT’s on the fiber-matrix interfacial properties, particularly in the composites containing axially and randomly oriented CNT’s, (II) considering two hybrid systems, composites with CNT’s‒coated fibers demonstrate outstanding improvements in the interfacial behaviors than those with CNT’s in matrix, (III) the pronounced effect of non-bonded interphase region on the interfacial properties, while no influence on the Young’s moduli is observed, and (Ⅳ) the presence of CNT’s augments the transverse Young’s modulus, however, it exhibits negligible effect on the longitudinal direction. The outcomes are consistent with experimental data and can be utilized in designing of CNT‒CF multi-scale composites

A Critical Review on the Structural Health Monitoring Methods of the Composite Wind Turbine Blades

With increasing turbine size, monitoring of blades becomes increasingly im-portant, in order to prevent catastrophic damages and unnecessary mainte-nance, minimize the downtime and labor cost and improving the safety is-sues and reliability. The present work provides a review and classification of various structural health monitoring (SHM) methods as strain measurement utilizing optical fiber sensors and Fiber Bragg Gratings (FBG’s), active/ pas-sive acoustic emission method, vibration‒based method, thermal imaging method and ultrasonic methods, based on the recent investigations and prom-ising novel techniques. Since accuracy, comprehensiveness and cost-effectiveness are the fundamental parameters in selecting the SHM method, a systematically summarized investigation encompassing methods capabilities/ limitations and sensors types, is needed. Furthermore, the damages which are included in the present work are fiber breakage, matrix cracking, delamina-tion, fiber debonding, crack opening at leading/ trailing edge and ice accre-tion. Taking into account the types of the sensors relevant to different SHM methods, the advantages/ capabilities and disadvantages/ limitations of repre-sented methods are nominated and analyzed

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