Fracture Toughness of Vapor Grown Carbon Nanofiber-Reinforced Polyethylene Composites (original) (raw)
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Polymer-Plastics Technology and Materials, 2020
This review critically examines the recent developments in the use of carbon-based nanofillers as additional reinforcement to enhance the interlaminar properties of FRP composites. The low interlaminar strength of FRP composites results in delamination failure. The various nanoreinforcement strategies and their effect on fracture toughness, interlaminar shear strength (ILSS) and interlaminar fatigue are discussed in detail to prevent this delamination failure. Important findings on various factors that influence the interlaminar properties of multi-scale composites are presented by discussing various intrinsic and extrinsic toughening processes. Moreover, an overview of simulation techniques is provided to predict the delamination onset and propagation.
Review of the mechanical properties of carbon nanofiber/polymer composites
Composites Part A: Applied Science and Manufacturing, 2011
In this paper, the mechanical properties of vapor grown carbon nanofiber (VGCNF)/polymer composites are reviewed. The paper starts with the structural and intrinsic mechanical properties of VGCNFs. Then the major factors (filler dispersion and distribution, filler aspect ratio, adhesion and interface between filler and polymer matrix) affecting the mechanical properties of VGCNF/polymer composites are presented. After that, VGCNF/polymer composite mechanical properties are discussed in terms of nanofibers dispersion and alignment, adhesion between the nanofiber and polymer matrix, and other factors. The influence of processing methods and processing conditions on the properties of VGCNF/polymer composite is also considered. At the end, the possible future challenges for VGCNF and VGCNF/polymer composites are highlighted.
Polymers, 2021
Functionalized polyacrylonitrile (PAN) nanofibers were used in the present investigation to enhance the fracture behavior of carbon epoxy composite in order to prevent delamination if any crack propagates in the resin rich area. The main intent of this investigation was to analyze the efficiency of PAN nanofiber as a reinforcing agent for the carbon fiber-based epoxy structural composite. The composites were fabricated with stacked unidirectional carbon fibers and the PAN powder was functionalized with glycidyl methacrylate (GMA) and then used as reinforcement. The fabricated composites’ fracture behavior was analyzed through a double cantilever beam test and the energy release rate of the composites was investigated. The neat PAN and functionalized PAN-reinforced samples had an 18% and a 50% increase in fracture energy, respectively, compared to the control composite. In addition, the samples reinforced with functionalized PAN nanofibers had 27% higher interlaminar strength compared to neat PAN-reinforced composite, implying more efficient stress transformation as well as stress distribution from the matrix phase (resin-rich area) to the reinforcement phase (carbon/phase) of the composites. The enhancement of fracture toughness provides an opportunity to alleviate the prevalent issues in laminated composites for structural operations and facilitate their adoption in industries for critical applications.
Low-velocity impact behavior of CNF-filled glass-reinforced polyester composites
http://www.sagepublications.com, 2013
Abstract A significant improvement in fiber-reinforced polymeric composite materials can be obtained by incorporating a very small amount of nanofillers in the matrix material. In this study, an ultrasonic liquid processor was used to infuse carbon nanofibers into the polyester matrix which was then mixed with a catalyst using a mechanical agitator. Both conventional and carbon nanofibers-filled glass fiber-reinforced polyester composites were fabricated using the vacuum-assisted resin transfer molding process. Low-velocity impact tests was performed at 10 J, 20 J, and 30 J energy levels on conventional as well as 0.1–0.3 wt% carbon nanofibers-filled glass fiber-reinforced polyester composites using Dynatup8210. The morphology of fractured specimens was examined using digital photographs and optical microscopy. There was an increase in the peak load for the nanophased glass fiber-reinforced polyester composites compared with the conventional one. The absorbed energy of nanophased glass fiber-reinforced polyester composites was less than that of conventional one at different energy levels. The extent of damage was more pronounced in the conventional glass fiber-reinforced polyester composites compared to nanophased ones. Failure mechanisms comprised of indentation, debonding, delamination, matrix cracking, and fiber fracture. The extent of damage was pronounced in conventional composite compared to nanophased ones. Keywords CNF, fiber-reinforced composites, VARTM, low-velocity impact
Journal of Applied Polymer Science, 2013
Scanning electron microscopy (SEM) was employed to investigate crack initiation and propagation process in notched and unnotched Izod impact fracture surfaces of the cellulose nanofiber (CNF) and microfibrillated cellulose (MFC)-filled polypropylene (PP) composites compared with microcrystalline cellulose (MCC)-filled composites. CNF is in the form of short fibers 50-300 nm in diameter and 6-8 in aspect ratio, MFC is in the form of long fibrils 50-500 nm in diameter and 8,000-80,000 in aspect ratio, and MCC is in the form of particles 50 lm in average diameter and 1-2 in aspect ratio. The reinforcement material size of CNF and MFC are smaller than that of MCC which means that the larger interfacial area between filler and matrix leading to larger energy dissipation at the interface during the impact fracture. The reinforcement-matrix debondings nearby MCC particles caused easy crack propagation which contributes smaller energy dissipation at the interface. A slip-stick behavior and stress whitened area during the fracture were observed. Morphological investigation helps to explain impact fracture behavior. According to essential work of fracture (EWF) analysis of Izod impact results, EWF method is applicable to analyze impact fracture behavior and the energy consumed in crack initiation and propagation during the fracture process can be calculated.
Change in failure mode of carbon nanofibers in nanocomposites as a function of loading rate
Journal of Materials Science, 2016
Vapor-grown carbon nanofiber (CNF)/epoxy composites are characterized under compression at 5 9 10-3-2800 s-1 strain rates. A difference in the fiber failure mechanism is identified based on the strain rate. CNFs show signs of deformation along their entire length under quasi-static compression. In contrast, the high-strain rate failure results in rupture of outer turbostratic carbon layers, leading to stress transfer to the inner graphite layers. The graphitic layers elongate and rupture, forming a conical tip at the fracture cross section of the CNFs. The strength of nanocomposites at high strain rate is measured to be up to 180 % higher depending on the composite composition and strain rate. CNFs substantially increase the localized plastic deformation of the matrix under quasistatic compression and result in nanoscale deformation features on the failure surface. The observed higher strength and modulus of nanocomposites at high strain rates are attributed to the difference in the matrix and fiber failure mechanisms at different strain rates.
2009
In this study, the cure kinetics of Cycom 977-20, an aerospace grade toughened epoxy resin, and its suspensions containing various amounts (1, 3 and 5 wt.%) of vapor grown carbon nanofibers (VGCNFs) with and without chemical treatment were monitored via dynamic and isothermal dynamic scanning calorimetry (DSC) measurements. For this purpose, VGCNFs were first oxidized in nitric acid and then functionalized with 3-glycidoxypropyltrimethoxy silane (GPTMS) coupling agent. Fourier transform infrared (FTIR) spectroscopy was subsequently used to verify the chemical functional groups grafted onto the surfaces of VGCNFs. Sonication technique was conducted to facilitate proper dispersion of asreceived, acid treated and silanized VGCNFs within epoxy resin. Dynamic DSC measurements showed that silanized VGCNF modified resin suspensions exhibited higher heat of cure compared to those with as-received VGCNFs. Experimentally obtained isothermal DSC data was then correlated with Kamal phenomenological model. Based on the model predictions, it was found that silanized VGCNFs maximized the cure reaction rates at the very initial stage of the reaction. Accordingly, an optimized curing cycle was applied to harden resin suspensions. Fracture testing was then carried out on the cured samples in order to relate the curing behavior of VGCNF modified resin suspensions to mechanical response of their resulting nanocomposites. With addition of 1 wt.% of silanized VGCNFs, the fracture toughness value of neat epoxy was found to be improved by 12%. SEM was further employed to examine the fracture surfaces of the samples.
Journal of Applied Polymer Science, 2012
The effects of vapor-grown carbon nanofiber (VGCNF) weight fraction, high-shear mixing time, and ultrasonication time on the Izod impact strengths of VGCNF/vinyl ester (VE) nanocomposites were studied using a central composite design. A response surface model (RSM) for predicting impact strengths was developed using regression analysis. RSM predictions suggested that an 18% increase in impact strength was possible for nanocomposites containing only 0.170 parts per hundred parts resin (phr) of VGCNFs ($0.1 v%) that were high-shear mixed for 100 min when compared to that of neat VE. In general, the predicted impact strengths increased for high-shear mixing times above 55 min and VGCNF weight fractions below 0.400 phr. The predicted strengths decreased as the VGCNF weight fraction was further increased. Scanning electron micrographs of the nanocomposite fracture surfaces showed that increased impact strength could be directly correlated to better nanofiber dispersion in the matrix.
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 effect of PVDF nanofibers on mode-I fracture toughness of composite materials
Composites Part B-engineering, 2015
In this study, the fracture behavior of carbon/epoxy laminates interleaved by polyvinylidene fluoride (PVDF) nanofibers is investigated. For this aim, a mode-I fracture test is conducted on virgin and modified laminates. Unlike the results of other studies, it is shown that PVDF nanofibers can increase mode-I fracture toughness (G I) noticeably in a specific situation. The results show that G I is enhanced about 43% and 36% in initiation and propagation stages of the fracture, respectively, using PVDF nanofibers. The morphology of the fractured surface is also presented for investigating the mechanism of toughening.