A Comparative Study of the Mechanical Properties of Jute Fiber and Yarn Reinforced Concrete Composites

ABSTRACT

A relatively better performance of jute fiber and yarn reinforced concrete composites can open up a wide access to application of natural resources in concrete strengthening. In order to achieve this goal, an experimental investigation on the flexural, compressive and tensile strengths of Jute Fiber Reinforced Concrete Composites (JFRCC) and Jute Yarn Reinforced Concrete Composites (JYRCC) has been conducted. To draw a specific conclusion, the mix ratios of 1:1.5:3 and 1:2:4 (by volume) of concrete have been maintained with incorporation of jute fiber and yarn in concrete mortar having different cut lengths with distinct volumetric ratios. Finally, a comparison of the JFRCC and JYRCC strength increments with respect to the plain concrete has been investigated. A significant increment of compressive, flexural and tensile strength was observed only for a short cut length having a low volumetric ratio, where JYRCC increment value was always found progressive. A far more regular arrangement and adequate mixture of JYRCC was also visualized compare to JFRCC in concrete mortar. All the principal increment values were found only in case of JYRCC with a mix ratio of 1:1.5:3. So, it can be concluded that the presence of jute yarn and more cement content can strengthen the concrete to a great extent.     

High-flexibility piezoelectric ribbon fiber fabrication through multi-material thermal drawing

In this study, an amorphous poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymer with a high yield strain (approximately 18 %) is proposed as a cladding material for highly flexible and reliable piezoelectric ribbon fibers. Macro preforms are fabricated for thermal drawing (TD) processes, in which a poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) film is sandwiched between two electrically conductive composite sheets (carbon black (CB)/polypropylene (PP)). The piezoelectric device is cladded with the P(VDF-HFP) copolymer. The preform geometries and TD parameters are optimized to overcome the incompatibility of flow characteristics among P(VDF-HFP), P(VDF-TrFE), and CB/PP composite at the drawing temperature, yielding fibers of length more than 80 m through TD. After annealing and poling, the fiber produces approximately 5 V (peak-to-peak) under 2.5 % tensile strain and 0.5 V (peak-to-peak) under bending deformation, with a 5-mm radius of curvature. Furthermore, the piezoelectric fiber shows no severe degradation in the output voltage after 10000 cycles of bending deformation with 1-mm radius of curvature. The piezoelectric ribbon fiber developed herein has potential as a flexible tensile, pressure, or bending sensor fiber for wearable applications.

     

Flexural response of hybrid carbon fiber thin cement composites

It is evident that the carbon-fiber-reinforced cementitious composites are being used in the structural and construction works owing to the synergetic action from two components viz. fiber and mortar matrix. Incorporation of a very nominal percentage of carbon fibers into a mortar mixture produces a strong and durable composite that leads the product of smart material properties. Flexural behavior of cement-based matrices carrying carbon fibers reinforcement of different percentage and size is studied in this paper. Influence of fiber content and length of the fiber is quantified using load–deflection curves. Specimens containing fiber of 0.0, 0.5, 1.0 and 1.5% with 3 mm (0.12 in.), 6 mm (0.36 in.), and their combination are prepared and tested. It is demonstrated that combination of 3 mm (0.12 in.) and 6 mm (0.36 in.) fibers enhances the bearing capacity to crack- and ultimate-stresses as well as the Young’s modulus of the fiber reinforced cement composites. The paper emphasizes the desired performances after the initiation of cracks and discusses the pre- and post-cracking load–deflection characteristics of the composites.     

Cooperative strategies of wireless access technologies: A game-theoretic analysis

The wireless Internet has to overcome the problem of spectrum scarcity as the number of mobile equipments could increase even by an order of magnitude in the next decade; the cooperation of mobile devices is foreseeable as a feasible solution to the problems. There exists a large body of literature on opportunistic ad hoc networking including Pelusi et al. (2006) [25], Chen et al. (2006) [26], Hui et al. (2005) [27]; however, the impact of the location of the devices on their access method selection is not yet appropriately dealt with. In this paper, we address this issue based on game-theoretic analyses. The key contribution of our work is threefold. First, we model the access method selection of mobile devices by extending the classical forwarding game with position, mobility, and availability of the devices. Second, we apply the model in game-theoretic analyses to better understand the optimal cooperation strategies in the presence of heterogeneous wireless technologies. We further extend our framework to include uncertainty. Finally, we present the applicability of the model in a cognitive radio scenario where complex structures of parameters are included.     

Buckling analysis of a cable-stayed circular frame

Large parabolic dish concentrators have been widely employed in solar thermal applications. The supporting structure of a solar dish concentrator consists of a circular frame, a central post, and front and rear cables connecting the frame to the post. The tensions in the cables cause compressive stresses in the circular frame and the central post, and this support structure must be designed for stability. In this paper, the nonlinear buckling behavior of the supporting structure of a cable-stayed circular frame is studied in detail. A three-dimensional finite element model of the supporting structure is developed to predict the critical cable tensions that would cause buckling of the circular frame and to determine the associated buckling mode shapes of the supporting structural system. The results show that the buckling load of a cable-stayed circular frame depends not only upon the cross-section of the frame, but also upon the number of cables and the inclinations of the cables. In all cases, in-plane buckling modes are predominant. The concentrated torques resulting from unbalanced cable tensions tend to induce the out-of-plane buckling modes.     

Influence of nitrogen plasma post-treatment on diamond-like carbon films synthesized by RF plasma enhanced chemical vapor deposition

DLC films were synthesized by RF plasma enhanced chemical vapor deposition and the effects of nitrogen plasma post-treatment at different pressures on the structure and properties of DLC films were investigated. Higher roughness was obtained after plasma post-treatment at higher pressures (0.3 and 0.9 torr) and plasma post-treatment at a lower pressure (0.15 torr) resulted in lower roughness than that of original films. The hardness of DLC films decreased with the decrease of post-treatment pressure, which is consistent with the Raman results of I_D/I_G ratio and G peak position. Compared to the original DLC film, the residual stress after plasma post-treatment decreased slightly due to the relatively thin region involved in the plasma post-treatment.     

New statistical method for detection and quantification ofrespiratory sinus arrhythmia

A statistical method with the advantages of 1) enabling graphical representation of within-respiratory cycle heart rate variations, 2) detecting the presence of respiratory sinus arrhythmia (RSA) in a moving window, and 3) providing breath-by-breath RSA amplitude and phase obtained from the fitting of a sinusoid to the instantaneous relative heart rate is presented.