Shaker Vibration Test Of Epoxy Composites Reinforced With Pristine And Functionalized Carbon Nanotubes

The vibration and damping characteristics of epoxy composites reinforced with pristine and functionalized multi-walled carbon nanotubes (MWCNTs) were investigated experimentally with potential use as integral passive damping elements in structural composite applications. The MWCNTs were introduced into the acetone solvent and then mixed with epoxy resin through a sonication process and mechanical stirring. The solvent was evaporated by means of magnetic hot plate and the hardener was added to the mixture once it was cooled down to room temperature. The MWCMTs/epoxy mixture was then injected into a mold to form the nanocomposite specimen. Nanocomposite specimens were fabricated for six different MWCNT loadings (0.02, 0.041, 0.061, 0.123, 0.25 and 0.37 wt%). Microstructural analysis, tensile and bending tests were carried out to examine the effects of pristine multi-walled carbon nanotubes (p-MWCNTs) and functionalized multi-walled carbon nanotubes (f-MWCNTs). The frequency response functions (FRFs), coherence and phase diagrams of nanocomposites were measured using a shaker vibration technique. The periodic up-chirp signal was generated by a shaker to excite the cantilever nanocomposite specimen at the base. The damped natural frequencies and damping ratios were obtained for different loadings of MWCNTs. The experimental results indicated that the damped natural frequencies of p-MWCNTs/epoxy and f-MWCNTs/epoxy composites increased by adding MWCNTs up to 0.12 wt.% and, after that, decreased with higher MWCNT content. Another finding was that p-MWCNTs were beneficial to improve the damping ratio of nanocomposites. While the damping ratios of f-MWCNTs with loadings of 0.02-0.06 wt.% were higher than p-MWCNTs ones, they did not increase at higher CNTs contents for the first mode of vibration

Crowd-sourcing archaeological research: HeritageTogether digital public archaeology in practice

Archaeologists are increasingly working with crowd-sourced digital data. Using evidence from other disciplines about the nature of crowd-sourcing in academic research, we suggest that archaeological projects using donated data can usefully be differentiated between generative projects (which rely on data collected by citizen scientists), and analytical projects (which make use of volunteers to classify, or otherwise analyse data that are provided by the project). We conclude that projects which privilege hyper-local research (such as surveying specific sites) might experience tension if the audience they are appealing to are 'cyber local'. In turn, for more 'traditional' archaeological audiences (when the primary motivating interests may be the tangible, physical nature of portable material culture or the archaeological site itself), then intangible, digital simulacra may not provide an effective medium through which to undertake digital public archaeology

Significant fatigue life enhancement in multiscale doubly-modified fiber/epoxy nanocomposites with graphene nanoplatelets and reduced-graphene oxide

ABSTRACT: We report the fatigue behavior of a novel multiscale fiberglass/epoxy composite modified with reduced-graphene oxide (rGO) and graphene nanoplatelets (GNP). A novel and cost-effective fabrication method based on vacuum assisted resin transfer molding (VARTM) method was used for manufacturing the composite laminates. Morphological and mechanical analysis of composites showed a successful dispersion of nano-fillers and a remarkable improvement in fatigue life of the nanocomposites. The experimental results revealed that all rGO concentrations resulted in a significant increase in fatigue life of the nanocomposites. These enhancements can be explained by the creation of stronger links between the nanoparticles fiberglass and epoxy. The experimental results also showed that lower concentrations of GNPs lead to an increase in fatigue life of nanocomposites; however, a decrease in their fatigue life can be seen at higher loadings

Small works, big stories. Methodological approaches to photogrammetry through crowd sourcing experiences

A recent digital public archaeology project (HeritageTogether) sought to build a series of 3D ditigal models using photogrammetry from crowd-sourced images. The project saw over 13000 digital images being donated, and resulted in models of some 78 sites, providing resources for researchers, and condition surveys. The project demonstrated that digital public archaeology does not stop at the 'trowel's edge', and that collaborative post-excavation analysis and generation of research processes are as important as time in the field. We emphasise in this contribution that our methodologies, as much as our research outputs, can be fruitfully co-produced in public archaeology projects

Dynamics, vibration and control of rotating composite beams and blades: A critical review

Rotating composite beams and blades have a wide range of applications in various engineering structures such as wind turbines, industrial fans, and steam turbines. Therefore, proper understanding of such structures is of a great importance. As a result, the behavior of rotating composite beam structures has received a lot of attention. This paper presents a comprehensive review of scholarly articles about rotating composite beams as published in the past decades. The review addresses analytical, semi-analytical and numerical studies dealing with dynamical problems involving adaptive/smart/intelligent materials (e.g. piezoelectric materials, electrorheological fluids, shape memory alloys, etc.), damping and vibration control, advanced composite materials (e.g. functionally graded materials and nanocomposites), complicating effects and loadings (e.g. added mass, tapered beams, initial curve and twist, etc.), and experimental methods. Moreover, the influence of Vlasov or restrained warping, out-of-plane warping, transverse shear, arbitrary cross-sectional geometry, trapeze phenomena, swept tip, size-dependent effect, as well as other areas that have been considered in research, are reviewed in depth. The review concludes with a presentation of the remaining challenges and future research needs

Rotating nanocomposite thin-walled beams undergoing large deformation

A computational model was developed to study the nonlinear steady state static response and free vibration of thin-walled carbon nanotubes/fiber/polymer laminated multiscale composite beams and blades. A set of nonlinear intrinsic equations describing the response of rotating cantilever composite beams undergoing large deformations was established. The main assumptions were small local strains and local rotations, large deflections and global rotations. Halpin–Tsai equations and fiber micromechanics were used to predict the bulk material properties of the multiscale nanocomposite. The carbon nanotubes (CNTs) were assumed to be uniformly distributed and randomly oriented through the epoxy resin matrix. Discretized by the Galerkin approximation, eigenvalues and vectors and nonlinear steady state static response of the nanocomposite beams and blades were calculated. The volume fraction of fibers, weight percentage of single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) and their aspect ratio were investigated through a detailed parametric study for their effects on the nonlinear response of nanotubes-reinforced moving beams. It was found that natural frequencies are significantly influenced by a small percentage of CNTs. It was also found that the SWCNTs reinforcement produces more pronounced effect in comparison with MWCNTs on the nonlinear steady state static response and natural frequencies of the composite beams

Fabrication and experimental evaluation of vibration and damping in multiscale graphene/fiberglass/epoxy composites

In this paper, the vibration and damping properties of multiscale laminated fiberglass/epoxy composites modified with a wide range of carbon nanofillers, including multiwalled carbon nanotubes, graphene oxide, reduced-graphene oxide and graphene nanoplatelets were examined for use in structural vibration applications. Simultaneous reinforcement of matrix and fibers was carried out via a novel method that combines a nanoparticle spraying process with nanoparticle/epoxy mixture to incorporate nanoparticles for the enhancement of vibration and damping properties of multiscale laminated fiberglass/epoxy composites. The vibration and damping properties as well as morphological, mechanical properties of the glass fiber-reinforced multiscale composites were investigated. Using a forced vibration technique, the frequency-response functions, natural frequencies and damping ratios of the nanocomposites were measured. The experimental results revealed that the damped natural frequencies of the nanocomposites increased with an increase in nanoparticle concentration. However, at higher contents of nanoparticles, the damped natural frequencies decreased and the damping ratio increased

Effect of functionalization of carbon nanotubes on vibration and damping characteristics of epoxy nanocomposites

The vibration and damping characteristics of epoxy composites reinforced by pristine and functionalized multi-walled carbon nanotubes (MWCNTs) were investigated experimentally for potential use as integral passive damping elements in structural composite applications. The MWCNTs were introduced into the acetone solvent and then mixed with epoxy resin through a sonication process and mechanical stirring. The solvent was evaporated from the mixture by means of magnetic hot plate and the hardener was added once it was cooled down to room temperature. The MWCMTs/epoxy mixture was then injected into a mold to form the nanocomposite specimens. Nanocomposite specimens were fabricated for six different MWCNT loadings (0.02, 0.041, 0.061, 0.123, 0.25 and 0.37 wt%). Microstructural analysis, tensile and bending tests were carried out to examine the effect of pristine multi-walled carbon nanotubes (p-MWCNTs) and functionalized multi-walled carbon nanotubes (f-MWCNTs). The frequency response functions (FRFs), coherence and phase diagrams of nanocomposites were measured using a forced vibration technique. A periodic up-chirp signal was generated by a shaker to excite the cantilever nanocomposite specimen at the base. The damped natural frequencies and damping ratios were obtained for different loadings of MWCNTs. The experimental results indicated that the damped natural frequencies of p-MWCNTs/epoxy and f-MWCNTs/epoxy composites increased by adding MWCNTs up to 0.12 wt.%, and decreased at higher MWCNTs content. Addition of p-MWCNTs were improved the damping ratio of nanocomposites. While the damping ratios from f-MWCNTs at loadings of 0.02–0.06 wt.% were higher than those from p-MWCNTs, they did not increase at higher CNTs contents for the first mode of vibration

Significant Fatigue Life Enhancement in Multiscale Doubly-Modified Fiber/Epoxy Nanocomposites with Graphene Nanoplatelets and Reduced-Graphene Oxide

We report the fatigue behavior of a novel multiscale fiberglass/epoxy composite modified with reduced-graphene oxide (rGO) and graphene nanoplatelets (GNP). A novel and cost-effective fabrication method based on vacuum assisted resin transfer molding (VARTM) method was used for manufacturing the composite laminates. Morphological and mechanical analysis of composites showed a successful dispersion of nano-fillers and a remarkable improvement in fatigue life of the nanocomposites. The experimental results revealed that all rGO concentrations resulted in a significant increase in fatigue life of the nanocomposites. These enhancements can be explained by the creation of stronger links between the nanoparticles fiberglass and epoxy. The experimental results also showed that lower concentrations of GNPs lead to an increase in fatigue life of nanocomposites; however, a decrease in their fatigue life can be seen at higher loadings