Tensile fracture behavior of short carbon nanotube reinforced polymer composites: A coarse-grained model (original) (raw)
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Composites Part B: Engineering, 2016
Short fiber reinforced polymer composites have found extensive industrial and engineering applications owing to their unique combination of low cost, relatively easy processing and superior mechanical properties compared to their parent polymers. In this study, a coarse-grained (CG) model of cross linked carbon nanotube (CNT) reinforced polymer matrix composites is developed. A characteristic feature of the CG model is the ability to capture the covalent interactions between polymer chains, and nanotubes and polymer matrix. The dependence of the elastic properties of the composites on the mole fraction of cross links, and the weight fraction and distribution of nanotube reinforcements is discussed. The simulation results reveal that the functionalization of CNTs using methylene cross links is a key factor toward significantly increasing the elastic properties of randomly distributed short CNT reinforced poly (methyl methacrylate) (PMMA) matrix. The applicability of the CG model in predicting the elastic properties of CNT/polymer composites is also evaluated through a verification process with a micromechanical model for unidirectional short fibers.
2012
Carbon nanotube (CNT) is considered as a new generation of material possessing superior mechanical, thermal and electrical properties. The applications of CNT, especially in composite materials, i.e. carbon nanotube reinforced polymer have received great attention and interest in recent years. To characterize the influence of CNT on the stress intensity factor of nanocomposites, three fracture modes (opening, shearing and tearing) are considered. The stress intensity factor of nanocomposites is evaluated using a representative volume element (RVE) based on the continuum mechanics and finite element method (FEM). Inter-atomic interactions of CNT are simulated by beam elements in the finite element (FE) model. Non-linear springbased line elements are employed to simulate the van der Waals (vdW) bonds. In all fracture modes, the stress intensity factor was determined for pure matrix and matrix reinforced with single-walled carbon nanotube (SWCNT). Numerical results indicate that the lo...
Composite Structures, 2010
The main goal of this research is to study the tensile behavior of embedded short carbon nanotubes (CNTs) in a polymer matrix in presence of van der Waals (vdW) interaction as inter-phase region. A 3D finite element model of a unit cell consisting of capped carbon nanotubes, inter-phase and surrounding polymer is built. The unit cell is subjected to tensile load case to obtain longitudinal Young's modulus of the investigated cell. A parametric study is carried out to investigate the effect of CNT's length on reinforcement. It is observed that improvement in the Young's modulus of CNT-composite is negligible for lengths smaller than 100 nm and saturation takes place in larger lengths on the order of 10 lm. Furthermore, a comparison between results obtained for short carbon nanotubes and long carbon nanotube is presented. The efficient length of CNT in form of (10, 10) is obtained at the order of 10 lm. Finally, it was shown that direct use of micromechanics equations for short fibers will overestimate the stiffness. However, employing effective stiffness of equivalent fiber comprising of CNT and its inter-phase instead of high modulus of CNT will lead us to more appropriate results, which are in an acceptable agreement with conventional semi-empirical micromechanics equations.
Elastic Behavior of Carbon Nanotubes Reinforced Composites: Micromechanical Modeling
2017
A micromechanical model is applied to examine the tensile properties of composite materials filled with multi-wall CNT oriented in in-plane and out-of-plane direction and a quantitative micromechanical model for the mechanical behavior of CNT-composites has been developed. Digimat-MF is used to generate a realistic three-dimensional microstructure for the current carbon nanotube/ epoxy composite. The Digimat model simulates a system of aligned carbon nanotubes arranged in-plane and another one having out of plane arrangement of reinforcements. A second model shows a representative volume element for the current nano-composite, in which the carbon nanotubes were simulated as a randomly (fully) dispersed, where all particles have been separated from each other. The predicted mechanical properties are compared with experimental tensile properties of composite materials reinforced with multi-wall CNTs arranged in in-plane and out-of-plane direction. A good agreement between the micromec...
Fracture toughness of carbon nanotube-reinforced metal-and ceramic-matrix composites
2011
Hierarchical analysis of the fracture toughness enhancement of carbon nanotube-(CNT-) reinforced hard matrix composites is carried out on the basis of shear-lag theory and facture mechanics. It is found that stronger CNT/matrix interfaces cannot definitely lead to the better fracture toughness of these composites, and the optimal interfacial chemical bond density is that making the failure mode just in the transition from CNT pull-out to CNT break. For hard matrix composites, the fracture toughness of composites with weak interfaces can be improved effectively by increasing the CNT length. However, for soft matrix composite, the fracture toughness improvement due to the reinforcing CNTs quickly becomes saturated with an increase in CNT length. The proposed theoretical model is also applicable to short fiber-reinforced composites.
Mechanics of Advanced Materials and Structures, 2018
This research presents numerical and micromechanical investigations of the effects of carbon nanotube (CNT) weight fraction on nanocomposites fracture energy. For this reason, numerical models consisting of 0.1, 0.2, and 0.5% CNT weight fractions are developed based on TEM image taken from nanocomposite samples. Fracture energy of these nanocomposites is determined using finite element simulations and micromechanics models. To determine the crack growth path and fracture parameters, mixed mode loading was applied on the nanocomposites. Also, fracture energy is determined using FESEM images along with numerical analysis. Finally, the numerical results were compared with experimental measurements found in the literature.
An investigation of fracture toughness and dynamic mechanical analysis of polymer nano-composites
International Journal of Engineering, Science and Technology, 2018
The study deals with development of a new composite material with an objective to increase the mechanical and thermal properties. The proposed work involves the preparation of novel polymer based composite material reinforced with cenosphere and multi walled carbon nanotubes (MWCNTs) and to investigate fracture toughness and dynamic mechanical properties. MWCNTs have high tensile strength which contributes to increase in strength of composite as well as the load transfer capability. The 20 weight % of cenosphere and upto 0.5wt% of MWCNTs are used for the study. Dynamic mechanical analysis and fracture toughness tests of the composite were carried out. It was found that fracture toughness of the sample with 0.2 wt% MWCNT increased by 12% than the epoxy cenosphere composite. The results obtained by experimental test are compared with the simulation results. Thermal properties obtained by DMA have shown better thermal stability. The SEM analysis was carried out to study the interfacial bonding between the fiber-matrix and also to substantiate the fracture toughness result.
The role of the interphase on mechanical performance of glassy polymer/single-walled carbon nanotube composites has been investigated by finite element (FE) method. The matrix and the interphase are mod-eled using continuum elements and the nanotube is analyzed by Timoshenko beam elements. Stress distribution and mechanical property of the nanocomposites are quantified as a function of the interphase's modulus and thickness. For composites that include an interphase, the predicted moduli are comparable to the values calculated by the rule of mixtures, but are much lower than those of an interphase-free composite. For composites consisting of only the CNT and the matrix, the predicted modulus values are in good agreement with those computed by the rule of mixtures and with theoretical data reported in the literature, although the predicted values are considerably higher than those of real polymer/CNT composites. Using Griffin's fracture analysis for dissimilar materials, we have proved that fracture stress of the weak boundary layer in the CNT/polymer interphase is lower than that of the CNT/polymer interface or of the matrix. The weak boundary layer, which is always existing in a CNT/polymer's three dimensional interphase, is proposed as the main reason for the large discrepancy between Young's moduli predicted by the model observed in this study and reported in the literature and those measured experimentally from real-world polymer/SWCNT composites. Published by Elsevier B.V.
Small but strong: A review of the mechanical properties of carbon nanotube-polymer composites
Carbon, 2006
The superlative mechanical properties of carbon nanotubes make them the filler material of choice for composite reinforcement. In this paper we review the progress to date in the field of mechanical reinforcement of polymers using nanotubes. Initially, the basics of fibre reinforced composites are introduced and the prerequisites for successful reinforcement discussed. The effectiveness of different processing methods is compared and the state of the art demonstrated. In addition we discuss the levels of reinforcement that have actually been achieved. While the focus will be on enhancement of Young's modulus we will also discuss enhancement of strength and toughness. Finally we compare and tabulate these results. This leads to a discussion of the most promising processing methods for mechanical reinforcement and the outlook for the future.