Nanocomposite Laminates Research Articles

Improvements in mechanical properties of a carbon fiber epoxy composite using nanotube science and technology

Abstract Carbon fiber reinforced epoxy composite laminates, with strategically incorporated fluorine functionalized carbon nanotubes (f-CNTs) at 0.2, 0.3 and 0.5 weight percent (wt.%), are studied for improvements in tensile strength and stiffness and durability under both tension–tension ( R = +0.1) and tension–compression ( R = −0.1) cyclic loadings, and then compared to the neat (0.0 wt.% CNTs) composite laminate material. To develop the nanocomposite laminates, a spraying technology was used to deposit nanotubes on both sides of each four-harness satin weave carbon fiber fabric piece for the 12 ply laminate lay up. For these experimental studies the carbon fiber reinforced epoxy laminates were fabricated using a heated vacuum assisted resin transfer molding (H-VARTM®) method followed by a 2 soak curing cycle. The f-CNTs toughened the epoxy resin-fiber interfaces to mitigate the evolution of fiber/fabric-matrix interfacial cracking and delamination under both static and cyclic loadings. As a consequence, significant improvements in the mechanical properties of tensile strength, stiffness and resistance to failure due to cyclic loadings resulted for this carbon fiber reinforced epoxy composite laminate.

Electromagnetic interference shielding properties of carbon nanotube buckypapercomposites

Preformed carbon nanotube thin films (10–20 µm), or buckypapers (BPs), consist of dense and entangled nanotube networks, whichdemonstrate high electrical conductivity and provide potential lightweight electromagneticinterference (EMI) solutions for composite structures. Nanocomposite laminates consistingof various proportions of single-walled and multi-walled carbon nanotubes, having differentconductivity, and with different stacking structures, were studied. Single-layer BPcomposites showed shielding effectiveness (SE) of 20–60 dB, depending on the BPconductivity within a 2–18 GHz frequency range. The effects on EMI SE performance ofcomposite laminate structures made with BPs of different conductivity values and epoxyor polyethylene insulating layer stacking sequences were studied. The resultswere also compared against the predictions from a modified EMI SE model. Thepredicted trends of SE value and frequency dependence were consistent with theexperimental results, revealing that adjusting the number of BP layers and appropriatearrangement of the BP conducting layers and insulators can increase the EMI SE from45 dB to close to 100 dB owing to the utilization of the double-shielding effect.

Characterization of nanocomposite laminates fabricated from aqueous dispersion of nanoclay

AbstractPreparation of E‐glass/waterborne epoxy prepregs containing natural nanoclay and properties of their composites are presented. Prepregs were prepared by wetting randomly oriented, chopped glass fiber preforms with aqueous dispersion of EpiRez 3522‐W‐60 resin, dicyandiamide, 2‐methylimidazole and natural nanoclay (Cloisite® Na+). The nanoclay content of the aqueous dispersion was adjusted to yield final nanoclay contents of 0, 1, 2, and 4 wt%, whereas the glass fiber content is kept constant at 47 wt%. These prepregs were then used to fabricate disk‐shaped composite samples by APA2000 rheometer. Composite samples were tested for interlaminar shear strength, flexural stiffness, and glass transition temperature. The flexural stiffness was observed to increase by more than 26% over the range of nanoclay loading, despite a 13% decrease in interlaminar shear strength. Similarly, glass transition temperature increased from 89°C to above 94°C for the samples comprising 4 wt% nanoclay. X‐ray diffraction analyses indicated 48% increase in the gallery spacing suggesting strong intercalation of the nanoclay platelets by the epoxy matrix. Microstructural observations of the fracture surfaces and polished surfaces show significant differences in the matrix topology and fiber to matrix adhesion. The composites with higher nanoclay content depict uniform and submicron surface features implying homogenous dispersion of nanoclay. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

The effects of carbon nanotubes on mechanical and thermal properties of woven glass fibre reinforced polyamide-6 nanocomposites

This paper presents a preliminary investigation on the effects of incorporating carbon nanotubes (CNT) into polyamide-6 (PA6) on mechanical, thermal properties and fire performance of woven glass reinforced CNT/PA6 nanocomposite laminates. The samples were characterized by tensile and flexural tests, thermal gravimetric analysis (TGA), heat distortion temperature (HDT) measurements, thermal conductivity and cone calorimeter tests. Incorporation of up to 2 wt% CNT in CNT/PA6/GF laminates improved the flexural stress of the laminates up to 36%, the thermal conductivity by approximately 42% and the ignition time and peak HRR time was delayed by approximately 31% and 118%, respectively.

Tensile and Fatigue Testings of Hybrid Al/APC-2 Nanocomposite Laminates at Elevated Temperature

To deal with the stringent operational demands the aerospace structural materials of light weight Aluminum alloy 2024 sheets and plies of carbon fibers reinforced thermoplastic matrix PEEK were used to sustain at least 80% of their mechanical properties at elevated temperature. The addition of nanoparticles SiO2 can enhance the composite laminate strength and stiffness. Also, Al 2024 sheets were treated by an anodic method of electroplating to increase surface roughness to achieve perfectly bonding with matrix PEEK. Then, the modified diaphragm curing process was adopted to make the innovative hybrid Al/APC-2 hybrid nanocomposite laminates. Next, both static tensile and fatigue tests were conducted at elevated temperature to obtain the mechanical properties, lives and failure mechanisms to verify the improved features of hybrid specimens. From tensile tests the mechanical properties of Al/APC-2 [4Al/0/±45/90/2Al]s hybrid laminates at elevated temperature were obtained. Although there is a big drop at 150°C, the reduction in strength from RT to 125°C is generally not significant. The longitudinal stiffness is almost unchanged at elevated temperature. After cyclic tension-tension (T-T) tests, the positions of received S-N curves go downwards as temperature rising. No delaminations were found in both tests. If the applied stress normalized by the ultimate strength at corresponding temperature, the normalized S-N curves are closer with some curve positions reversed. Significant improvement of manufacturing and enhancement of mechanical properties in hybrid laminates were achieved finally.

Preparation of MWCNT/Carbon Fabric Reinforced Hybrid Nanocomposite and Examination of its Mechanical Properties

In our work we have prepared carbon fiber/epoxy composite and carbon fiber/carbon nanotube/epoxy hybrid nanocomposite laminates by hand laminating assisted by vacuumbag technology. During the production of the specimens we have encountered the viscosity increasing effect of nanotube filling, which we characterized by a viscosity test. The results of the test showed, that in the lowest shear rate range carbon nanotube filling can cause an increase of viscosity by three orders of magnitude, but also at higher shear rates the viscosity of the nanotube filled epoxy resin was ten times the viscosity of the unfilled resin. Mechanical properties of the composite and hybrid composite have been compared by tensile, bending and interlaminar shear tests. During the tensile tests AE signals have also been recorded. The fracture surfaces have been examined by SEM micrographs. The nanotube filling has decreased the tensile strength and the modulus of elasticity by 7-8 percent presumably indirectly, the bending properties didn’t change noticeably, but the interlaminar shear strength of the composite has increased by 15 percent thanks to nanotube filling of the matrix. The decrease of the delamination inclination of the hybrid composite has been affirmed both by the AE and SEM results.

Polymeric thermal actuation using laminates based on polymer–clay nanocomposites

AbstractPolymer and polymer–clay nanocomposite laminates were prepared as transparent thermal actuators with possible uses in automatic aeration and ventilation or as thermal switches. Low levels of smectite clay addition reduced the thermal expansion coefficient of poly(methyl methacrylate) (PMMA) but retained optical clarity and reduced water absorption. X‐ray diffraction and transmission electron microscopy were used to confirm the formation of PMMA–clay nanocomposites, and dynamic mechanical analysis was used to measure the coefficients of thermal expansion. The experimental values of the radius of curvature of the laminates from cantilever bending tests were in good agreement with the theoretical predictions for composite bars with only 4 wt % (nominally 1.3 vol %) mineral reinforcement. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Fatigue Response of Hybrid Magnesium/Carbon-Fiber/Peek Nanocomposite Laminates at Elevated Temperature

High performance Mg based hybrid five-layered composite laminates were fabricated by means of sandwiching the AZ31 Mg foils with the Carbon/PEEK prepregs, in which the nanoparticles SiO2 were uniformly spreaded at the interfaces, through hot press. The basic mechanical properties of the cross-ply hybrid laminates were obtained by tensile tests, and they were found in good agreement with the prediction by the rule of mixture. Then, the response due to constant stress amplitude tension-tension (T-T) cyclic loading at elevated temperature up to 10 6 cycles was investigated.

Mechanical and thermal behavior of non-crimp glass fiber reinforced layered clay/epoxy nanocomposites

Mechanical and thermal properties of non-crimp glass fiber reinforced clay/epoxy nanocomposites were investigated. Clay/epoxy nanocomposite systems were prepared to use as the matrix material for composite laminates. X-ray diffraction results obtained from natural and modified clays indicated that intergallery spacing of the layered clay increases with surface treatment. Tensile tests indicated that clay loading has minor effect on the tensile properties. Flexural properties of laminates were improved by clay addition due to the improved interface between glass fibers and epoxy. Differential scanning calorimetry (DSC) results showed that the modified clay particles affected the glass transition temperatures ( T g) of the nanocomposites. Incorporation of surface treated clay particles increased the dynamic mechanical properties of nanocomposite laminates. It was found that the flame resistance of composites was improved significantly by clay addition into the epoxy matrix.

Fatigue Response of Hybid Magnesium/Carbon-Fiber/PEEK Nanocomposite Laminates at Elevated Temperature (II)

Fatigue Response of Hybid Magnesium/Carbon-Fiber/PEEK Nanocomposite Laminates at Elevated Temperature (II)

Effect of nanoclay addition on vibration properties of glass fibre reinforced vinyl ester composites

This paper presents the experimental study of free vibration and damping characteristics of hybrid nanocomposite laminates by reinforcing short fibre chopped strand mat and organically modified montmorillonite clay (0, 1, 3 and 5 wt.%) in the vinyl ester matrix by hand lay-up technique. Theoretical study is also carried out to study the vibration and damping characteristics of hybrid nanocomposites. Dynamic result shows that the second phase nanoscale dispersion in the matrix and E-glass fibre significantly enhances the internal damping of hybrid composites.

カップスタック型カーボンナノチューブ分散樹脂を用いたCFRP積層板の熱弾性特性及び微視的損傷挙動評価

This study investigated the thermo-elastic properties and microscopic ply cracking behaviors in carbon fiber reinforced nanotube-dispersed epoxy laminates. The nanocomposite laminates used in this study consisted of traditional carbon fibers and epoxy resin filled with cup-stacked carbon nanotubes (CSCNTs). Thermo-mechanical properties of unidirectional nanocomposite laminates were evaluated, and quasi-static and fatigue tension tests of cross-ply laminates were carried out in order to observe the damage accumulation behaviors of matrix cracks. Clear retardation of matrix crack onset and accumulation was found in composite laminates with CSCNT compared to those without CSCNT. Fracture toughness associated with matrix cracking was evaluated based on the analytical model using the experimental results. It was concluded that the dispersion of CSCNT resulted in fracture toughness improvement and residual thermal strain decrease, and specifically, the former was the main contribution to the retardation of matrix crack formation.

Mechanical properties of carbon-modified silicon oxide barrier films deposited by plasma enhanced chemical vapor deposition on polymer substrates

Cohesive and adhesive properties of silicon oxide barrier coatings deposited from an oxygen/hexamethyldisiloxane gas mixture by plasma enhanced chemical vapor deposition, with controlled incorporation of carbon on 12 μm thick polyethylene terephtalate films were investigated. The reactor was equipped with a 2.45 GHz slot antenna plasma source and a 13.56 MHz-biased substrate holder. The two plasma sources were operated separately or in a dual mode. It was found that no or negligible internal stresses were introduced in the silicon oxide coatings as long as the increase of energy experienced by the film was compensated by the densification of the oxide. For a range of process parameters and carbon content on the changes of the crack onset strain, adhesion, and cohesion were found to be similar. Generally a high crack onset strain or good adhesion and cohesion were measured for films with an increased carbon content, although this was obtained at the expense of the gas barrier performance. Promising approaches towards high-barrier thin films with good mechanical integrity are proposed, based on coatings with a gradient in the carbon content and in the mechanical properties, on nano-composite laminates, and on organo-silane treatments.

Matrix cracking behaviors in carbon fiber/epoxy laminates filled with cup-stacked carbon nanotubes (CSCNTs)

This study investigated the damage accumulation behaviors in carbon fiber reinforced nanocomposite laminates under tensile loading. The nanocomposite laminates used in this study were manufactured from prepregs consisting of traditional carbon fibers and epoxy resin filled with cup-stacked carbon nanotubes (CSCNTs). Thermo-mechanical properties of unidirectional carbon fiber reinforced nanocomposite laminates were evaluated, and cross-ply laminates were subjected to tension tests in order to observe the damage accumulation behaviors of matrix cracks. A clear retardation of matrix crack onset and accumulation was found in composite laminates with CSCNT compared to those without CSCNT. Fracture toughness associated with matrix cracking was evaluated based on the analytical model using the experimental results. It was suggested that the dispersion of CSCNT resulted in fracture toughness improvement and residual thermal strain decrease, which is considered to cause the retardation of matrix crack formation.

Manufacturing and mechanical response of nanocomposite laminates

A newly developed methodology is proposed first to manufacture AS-4/PEEK APC-2 nano-composite laminates. The improvement of mechanical properties of nano-laminates is verified by a series of testings systematically. The achievement of empirical results is highlighted as follows. From tensile tests it is found that the optimal content of nanoparticles (SiO 2) is 1% by total wt. The ultimate strength increases about 12.48% and elastic modulus 19.93% in quasi-isotropic nano-laminates. Whilst, the improvement of cross-ply nano-composite laminates is less than that of quasi-isotropic laminates. At elevated temperatures the ultimate strength decreases slightly below 75 °C and the elastic modulus reduces slightly below 125 °C, however, both properties degrade highly at 150 °C (≈ T g) for two layups generally. Finally, after the constant stress amplitude tension–tension (T–T) cyclic testing, it is found that both the stress-cycles (S–N) curves are very close below 10 4 cycles for cross-ply laminates w/wo nanoparticles, and the S–N curve of nano-laminates slightly bent down after 10 5 cycles. Whilst in quasi-isotropic laminates, the S–N curve of nano-laminates is always slightly below that of APC-2 laminates through the life.

How cracks in SiO x-coated polyester films affect gas permeation

In this paper theoretical models have been established that can account for the gas transmission through nanocomposite laminates, consisting of an oxide layer of finite permeability containing defects, on a polymer sheet of finite thickness. The defect shapes can either be in the form of long cracks or rectangular holes. The models offer a choice of exact numerical calculations or fast and intuitive analytical approximations. The experimental measurements of oxygen permeation through four different SiO x /poly(ethylene terephthalate) samples that were strained to produce distributions of cracks showed good agreement when compared with predicted results from the approximate analytic model. As a consequence of this observation, a key practical conclusion is that, because of the logarithmic dependence of transmission on the width of a crack, for a given strain it is better to have a small number of large cracks rather than a large number of small cracks.