Viscoelastic Properties Of Nanocomposites Research Articles

Mechanical, microstructural, and dynamic mechanical properties of electrospun short nanofiber reinforced epoxy composites

AbstractElectrospun nanofibers are emerging reinforcing fillers with epoxy matrix owing to its high aspect ratio, surface area, and mechanical properties resulting in wider applications. Application of non‐woven configuration of nanofiber mats, collected from electrospinning has been traditionally confined to improve interlaminar responses of fiber reinforced composites. However, potential of short nanofiber in improving bulk matrix properties cannot be under estimated. This study adopts matrix modification approach by incorporating different concentration of nylon 6 short nanofiber in epoxy matrix to investigate its influence on tensile and viscoelastic properties of nanocomposite. Results showed a moderate improvement in modulus for nanocomposites despite to general drop in strength, however fracture energy and failure strain improved significantly at an optimum concentration of 0.1 wt% nanofiber. In addition, highest storage modulus as well as damping factor was recorded with decline in glass transition temperature for 0.1 wt% nanofiber content. Moreover, it was revealed that addition of nanofiber altered brittle fracture to neck‐featured ductile mode and effectively introduced energy absorbing interfaces making it well suit for diverse applications.

Viscoelastic and mechanical properties of CNT-reinforced polymer-based hybrid composite materials using hygrothermal creep

In the present work, a combination of experimental and numerical procedure is proposed to study the effects of different hygrothermal conditions on the creep strain, viscoelastic properties of nanocomposites, and mechanical properties of such nanocomposite-based carbon fiber–reinforced polymer (CFRP) hybrid composite materials. Ultrasonic probe sonicator is used to randomly disperse the multiwalled carbon nanotubes into an epoxy to minimize agglomerations. Dynamic mechanical analysis is employed to conduct the creep tests under different hygrothermal conditions of such nanocomposite samples. The Findley power law is used to obtain the long-term creep behavior of nanocomposite materials. Prony series is used to determine the viscoelastic properties of nanocomposite material in the frequency domain. Coefficient of moisture expansion (CME) is independent of moisture concentration; thus, CME of the nanocomposite is also determined. Strength of materials and Saravanos–Chamis micromechanics (SCM) have also been utilized to obtain the mechanical properties of such hybrid composite materials under different hygrothermal conditions. It has been found that the inclusion of multiwalled carbon nanotubes in the nanocomposite and hybrid composites improves storage modulus and loss factor (i.e., tan δ) compared to the conventional CFRP-based composite materials under hygrothermal conditions.

Fluorescent epoxy-graphene quantum dots nanocomposites: synthesis and study of properties

ABSTRACT This study aims to investigate the reinforcing effects of graphene quantum dots on various properties of epoxy resins. To do this, graphene quantum dots were synthesized, then, characterized by various spectroscopic methods. These nanoparticles including several weight percentages along with a curing agent were added to epoxy resin. Finally, fluorescent epoxy graphene quantum dots nanocomposites were prepared. FTIR, photoluminescence, UV-visible absorption, FESEM, TGA, tensile testing and DMTA analysis were used to characterize the resultant nanocomposites. Findings evinced that adding graphene quantum dots to the epoxy resin led to an improvement of thermal stability, mechanical features, and viscoelastic properties of nanocomposites.

Effect of Temperature on the Viscoelastic Properties of Carbon Nanotube Reinforced Polypropylene Composites

Finite element method (FEM) is used to analyze the mechanical properties of carbon nanotubes (CNTs) reinforced polypropylene (PP) composites. Firstly, polypropylene is assumed as a viscoelastic material, while carbon nanotubes are assumed as linear elastic materials to study the effect of temperature on the mechanical properties of neat PP and CNT/PP nanocomposites. Secondly, to compare the viscoelastic properties of neat PP and CNT/PP nanocomposites, the relaxation time at a specific temperature is used to investigate the relaxation of the nanocomposites for fixed tensile displacements. Thirdly, the effect of CNT volume fraction on the viscoelastic properties of nanocomposites is studied at different temperatures. Finally, to better understand the stress distribution along the CNT axial direction, a single carbon nanotube is isolated in the matrix to compare the stress distribution with nonisolated CNTs.

Nanoindentation characterization of polymer nanocomposites for elastic and viscoelastic properties: Experimental and mathematical approach

This work aims to determine the elastic and viscoelastic properties of microwave processed nanocomposites. Three different power rating has been used in microwave processing of polymer nanocomposite, i.e., 180 W, 360 W, and 540 W. Nanomechanical elastic properties of nanocomposites have been determined using the conventional nanoindentation method. Viscoelastic properties of nanocomposites have been determined by observing the increase in depth at maximum load (10 mN) during a small holding period (2 s). Polypropylene nanocomposites (PNT), high-density polyethylene nanocomposites (HNT), and low-density polyethylene nanocomposites (LNT) have shown an increase in modulus, hardness, and viscosity term with an increase in microwave power. The plasticity index has been obtained using the area under the loading and unloading curves. HNT and PNT samples have shown a plasticity index of 0.71 ± 0.02 and 0.62 ± 0.05, respectively. However, LNT samples have shown the same plasticity index 0.61 at all three-power ratings.

Viscoelastic Nanocomposites of Wormlike Micelles of Surfactant and Aluminosilicate Clay Nanoplates

Viscoelastic nanocomposites based on a matrix of semidilute aqueous solutions of entangled wormlike (polymer-like) micelles of a cationic surfactant and aluminosilicate nanoplates of montmorillonite clay, efficiently acting as crosslinks, were prepared and studied. The produced materials represent a new type of a self-assembling nanocomposite system. The results of changes in viscoelastic properties of nanocomposites when adding clay nanoplates are well described by a proposed interaction model which implies adsorption of wormlike micelles by end-caps to the surfactant layer formed on the nanoplates surface.

Effect of nanoparticles dispersion on viscoelastic properties of epoxy–zirconia polymer nanocomposites

In the present work zirconia-nanoparticles were dispersed in epoxy matrix to form epoxy-zirconia polymer nanocomposites using ultrasonication and viscoelastic properties of nanocomposites were investigated. For the same spherical zirconia-nanoparticles (45 nm) were dispersed in weight fraction of 2, 4, 6 and 8 % to reinforce the epoxy. DMA results show the significant enhancement in viscoelastic properties with the dispersion of zirconia nanoparticles in the epoxy matrix. The value of storage modulus and glass transition temperature increases from 179 MPa (pristine) to 225 MPa (6 wt.% ZrO2) and 61 °C (pristine) to 70 °C (6 wt.% ZrO2) respectively with the dispersion of zirconia nanoparticles in the epoxy.

Effect of nanoparticles dispersion on viscoelastic properties of epoxy-zirconia polymer nanocomposites

In the present work zirconia-nanoparticles were dispersed in epoxy matrix to form epoxy-zirconia polymer nanocomposites using ultrasonication and viscoelastic properties of nanocomposites were investigated. For the same spherical zirconia-nanoparticles (45 nm) were dispersed in weight fraction of 2, 4, 6 and 8 % to reinforce the epoxy. DMA results show the significant enhancement in viscoelastic properties with the dispersion of zirconia nanoparticles in the epoxy matrix. The value of storage modulus and glass transition temperature increases from 179 MPa (pristine) to 225 MPa (6 wt.% ZrO2) and 61 °C (pristine) to 70 °C (6 wt.% ZrO2) respectively with the dispersion of zirconia nanoparticles in the epoxy.

Effect of TiO2 nanoparticles on the viscoelastic and time-dependent behaviors of TiO2/epoxy particulate nanocomposite

Abstract In this work, the effects of nano titania are investigated on mechanical, creep, and viscoelastic behaviors of epoxy resin. For this purpose, 0.25, 0.5, and 1 vol.% of TiO2 nanoparticles were mixed with thermoset epoxy resin by mechanical and ultrasonic homogenizers and then the tensile, creep, and DMTA test samples were fabricated. The results of tensile tests show that the addition of TiO2 nanopowder slightly increased the strength and Young’s modulus of epoxy resin. However, the ultimate tensile strain or the rupture strain of nanocomposites is decreased. In addition, to understand the viscoelastic behavior of nanocomposites, the DMTA and tensile creep tests have been done. Tensile creep test has been done by DMTA and universal test machine. Both results confirmed that the creep resistance of nanocomposites has extensively improved by adding the titania nanoparticles. Variations of storage modulus, loss modulus, and tan (δ) by adding TiO2 nanopowder were examined in two modes of bending and tension. Storage and loss moduli of nanocomposite are considerably increased in all the states, but the storage modulus was more sensitive to TiO2 loading intensity. Thus, test results showed that introduction of TiO2 in the epoxy resin leads to the improvement of mechanical, creep resistance, and viscoelastic properties of nanocomposites. Due to the wide applications of epoxy resins in engineering devices, this method of reinforcement can be practical and useful to overcome some limitations of epoxy resins.

Melt Foamability of Poly(ethylene terephthalate)/Clay Nanocomposites Prepared by Extrusion Blending in the Presence of Pyromellitic Dianhydride

Exfoliated poly(ethylene terephthalate) (PET)/organoclay nanocomposites were prepared by extrusion blending method with different clay contents and molecular weights of raw PET. Pyromellitic dianhydride (PMDA) was extruded, together with PET and clay, to introduce long-chain branching to PET backbone and delaminate the clay layers. Although the molecular weights and viscoelastic properties of nanocomposites were much lower than those of foamable PMDA-modified PET, the melt foamability of nanocomposites was significantly improved by the well-dispersed clays due to the heterogeneous nucleation effect, enhanced nonisothermal crystallization rate, and so on. Foaming temperature windows with a width of 20–60 °C were explored for PET/clay nanocomposites with intrinsic viscosities of 0.67–0.94 dL/g, in which nanocomposites foams with cell diameters of 29–53 μm, cell densities of 6.5 × 107–6.9 × 108 cells/cm3, and expansion ratio of 10–50 could be controllably produced using supercritical CO2 as a blowing agent.

Modeling of dynamic mechanical properties of epoxy and epoxy-phenolic reinforced with multi-wall carbon nanotubes

The viscoelastic properties of nanocomposites based on epoxy and epoxy-phenolic blend matrix reinforced with multi-wall carbon nanotubes were studied. The content of carbon nanotube (0.2 and 0.5 wt.%) and its surface state (pristine vs. oxidized) varied. The characterization of the nanocomposites was done by means of infrared spectroscopy and chemical methods. From the viscoelastic properties of nanocomposites, characteristic properties such as storage modulus ( E0), tan δ and damping peak (tan δ) were obtained. The void content was also determined. Also, Weibull statistics are used to represent the failure of secondary bonds during the relaxation processes that lead to stiffness change over the full range of use temperatures. The incorporation of phenolic resin to an epoxy matrix leads to an increase of the relaxation modulus. The glass transition temperature of the epoxy-phenolic nanocomposites decrease when it is incorporated carbon nanotubes, independently of its state (pristine or oxidized).

Influence of Interfacial Layer Between Nanoparticles and Polymeric Matrix on Viscoelastic Properties of Hydrogel Nanocomposites

The viscoelastic properties of nanocomposites are influenced by both the nanoparticle distribution and the nanoparticle−polymer affinity. These two parameters are closely coupled, and evaluation of individual contributions to the mechanical properties is a critical requirement for efficient development of nanocomposites. To decouple these two effects, we utilized charge repulsion among nanoparticles so that we could essentially eliminate particle agglomeration. We then investigated how the nanoparticle−polymer affinity relates to the mechanical properties of the nanocomposite by comparing silica and polystyrene nanoparticles. The surface roughness of the particles and the molecular conformation of the interfacial layer between the polymer and the nanoparticles were characterized by synchrotron small-angle X-ray scattering and quartz crystal microbalance, respectively. On polystyrene particles, the surface roughness was larger, and the polymer adsorbed strongly. Consequently, the mobility of the adsorbed polymer was reduced compared to that on silica particles. This reduced mobility explains a smaller viscoelastic loss for the polystyrene-filled nanocomposite compared to the silica-filled nanocomposite.