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3D Bio-Plotted Composite Scaffold Made of Collagen Treated Hydroxyapatite-Tricalciumphosphate for Rabbit Tibia Bone Regeneration
Get PDFBiphasic calcium phosphate scaffolds with 20/80 HA/TCP ratio were fabricated using the 3D-Bioplotting system to heal critical size defects in rabbit tibia bone. Four different architectures were printed in a layer by layer fashion with lay down patterns viz. (a) 0°– 90°, (b) 0°– 45°– 90°– 135°, (c) 0°–108°– 216° and (d) 0°– 60°– 120°. After high-temperature sintering scaffolds were coated with collagen and were further characterized by (FTIR) Fourier Transform Infrared Spectroscopy, (SEM) Scanning Electron Microscopy, (XRD) X-Ray diffraction, Porosity analysis and Mechanical testing. Scaffold samples were tested for its ability to induce cytotoxicity in Balb/c 3T3 cells at in vitro condition using elution method. Skin sensitization potential of scaffolds was evaluated in male guinea pigs using guinea pig maximization test (GPMT). Further, scaffolds were implanted in eight rabbit tibia bones and biocompatibility and histological evaluations were carried out after 4 and 8 weeks implantation periods. In-vitro results include bonding, surface morphology, phases, porosity, mechanical strength and Cytotoxicity. In-vivo results include sensitization, capsule formation, inflammation, presence of polymorphonuclear cells, giant cells, plasma cells, X-Rays and degradation of the material. It was concluded that HA/TCP/Collagen scaffold with 0°– 45°– 90°– 135° architecture exhibits the most excellent properties in healing critical size bone defects in rabbits
Properties of Woven Natural Fiber-Reinforced Biocomposites
Get PDFWoven natural fiber-reinforced composites were fabricated using four different flax fabrics and two biobased epoxy resin matrices. The reinforced composites were prepared using resin infusion technique and fiber volume fractions of between 28–35% were achieved using this method. The fiber matrix interaction and the failure mechanism in the composite were observed using scanning electron microscopy. The flexural strength and modulus on the warp and weft directions were characterized and it was found that based on yarn count and yarn thickness change in the flexural strength was observed. Dynamic water absorption and thickness swelling were observed for a certain period of time and depended on pore volume and fiber volume fractions. Among the fabric architecture, on the weft direction satin weave with low fiber volume fraction has achieved the highest flexural strength and modulus of 220 MPa and 11.7 GPa respectively
Nanocellulose in Spun Continuous Fibers: A Review and Future Outlook
Get PDFContinuous fibers are commonly manufactured for a wide variety of uses such as filters, textiles, and composites. For example, most fibrous reinforcements (e.g., carbon fiber, glass fiber) for advanced composites are continuous fibers or yarns, fabrics, and preforms made from them. This allows broad flexibility in design and manufacturing approaches by controlling fiber orientation and architecture. However, there has been growing interest in preparing continuous fibers from biobased materials such as plants. Of particular recent interest are nanocelluloses, which are projected to be less expensive than many other nanomaterials and have the potential to be produced in large volumes. They also have an impressive strength-to-weight ratio and have so far shown few environmental, health, and safety concerns in their unmodified state. However, efficient and effective use of nanocellulose in continuous fibers is challenging and a variety of approaches have been explored in which nanocellulose dispersions are either spun directly or in combination with polymers. Methods such as wet spinning, dry spinning, melt spinning, and electrospinning have been investigated. To better understand the body of knowledge of this new and growing area, various approaches are reviewed and a perspective on what the future holds is provided
Simple Efficient Smart Finite Elements for the Analysis of Smart Composite Beams
Get PDFThis paper is concerned with the development of new simple 4-noded locking-alleviated smart finite elements for modeling the smart composite beams. The exact solutions for the static responses of the overall smart composite beams are also derived for authenticating the new smart finite elements. The overall smart composite beam is composed of a laminated substrate conventional composite beam, and a piezoelectric layer attached at the top surface of the substrate beam. The piezoelectric layer acts as the actuator layer of the smart beam. Alternate finite element models of the beams, based on an "equivalent single layer high order shear deformation theory", and a "layer-wise high order shear deformation theory", are also derived for the purpose of investigating the required number of elements across the thickness of the overall smart composite beams. Several cross-ply substrate beams are considered for presenting the results. The responses computed by the present new "smart finite element model" excellently match with those obtained by the exact solutions. The new smart finite elements developed here reveal that the development of finite element models of smart composite beams does not require the use of conventional first order or high order or layer-wise shear deformation theories of beams. Instead, the use of the presently developed locking-free 4-node elements based on conventional linear piezo-elasticity is sufficient
18-DOF Triangular Quasi-Conforming Element for Couple Stress Theory
Get PDFThe basic idea of quasi-conforming method is that the strain-dis- placement equations are weakened as well as the equilibrium equations. In this paper, an 18-DOF triangular element for couple stress theory is proposed within the framework of quasi-conforming technique. The formulation starts from truncated Taylor expansion of strains and appropriate interpolation functions are chosen to calculate strain integration. This element satisfies C0 continuity with second order accuracy and weak C1 continuity simultaneously. Numerical examples demonstrate that the proposed model can pass the C
Gyro-Chirality Effect of Bianisotropic Substrate on the Resonant Frequency and Half-power Bandwidth of Rectangular Microstrip Patch Antenna
Get PDFIn this paper, the gyrotropic bi-anisotropy of the chiral medium in substrate constitutive parameters (xc and hc) of a rectangular microstrip patch antenna is introduced in order to observe its effects on the complex resonant frequency and half-power bandwidth. The analysis is based on the full-wave spectral domain approach using the Moment Method, with sinusoidal type basis functions. The numerical calculations related to the dominant mode have been carried out, and it has been observed that the resonant frequency and the bandwidth are directly linked to the medium chirality. The new results can be considered as a generalisation form of the previously published work
Cooling of electronic components using nanofluids
Get PDFA finite volume code used for detailed analysis of forced-convection flow in a horizontal channel containing eight heat sources simulating electronic components. The study deals the effect of variations of Reynolds number, the volume fraction and the good choice of type of nanoparticles added to the base fluid. The study shows that the rate of heat transfer increases with increasing Reynolds number and the volume fraction of nanofluids but not infinitely. The analysis of the dynamic and thermal field shows that the heat transfer is improved, with the increase in the Reynolds number and the volume fraction. The study also shows that the choice of nanoparticles added to the base fluid is crucial, otherwise the best cooling electronic components is observed when using copper nanoparticles followed by those of alumina trioxide
Comparison Between the Influence of Mechanical and Electromagnetic Stirring on Aluminum Ingot Purity During Ohno Continuous Casting
Get PDFThis paper outlines the findings in the comparison of the influence of mechanical and electromagnetic stirring on ingot long term purity and uniformity during Ohno Continuous Casting. The magnitude of the average optimum velocity flow field and stirring parameters required to effectively purify aluminum ingots using mechanical stirring of the melt was determined and analyzed. Basing on the determined optimum mechanical flow field, electromagnetic parameters producing almost the same flow field near the interface were obtained through careful adjustments of parameters. Optimum parameters of the mechanical and electromagnetic stirring were obtained by numerically solving the solidification model coupled with either the multi-reference frame model (for mechanical stirring) or the magnetohydrodynamic model (for electromagnetic stirring) in CFD Fluent 6.3.26 software. For mechanical stirring, an optimum stirring intensity of 2mm/min was determined whilst for electromagnetic stirring, the optimum magnetic field with an amplitude of 20mT and a frequency of 2.7Hz was determined and these produced same magnitude optimum flow fields resulting in high purity aluminum ingots. Comparison of the two methods showed that electromagnetic stirring is good in covering all the regions near the solid-liquid interface and is more effective in bulk melt mixing; thus produces more uniform and purer ingots for longer casting times
Shear Strength Evaluation of Concrete Beams Reinforced with BFRP Bars and Steel fibers without Stirrups
Get PDFThis paper presents experimental and analytical investigations on concrete beams reinforced with basalt fiber reinforced polymer (BFRP) and steel fibers without stirrups. Independent behaviour of BFRP reinforced beams and steel fiber reinforced beams were evaluated and the effect of combining BFRP bars and steel fiber was investigated in detail. It is found that combining steel fibers with BFRP could change the shear failure of BFRP reinforced beam to flexural failure. Further, the existing analytical models were reviewed and compared to predict the shear strength of both FRP reinforced and steel fiber reinforced beams. Based on the review, the appropriate model was chosen and modified to predict the shear strength of BFRP reinforced beam along with steel fibers
Three-Dimensional Static Analysis of Nanoplates and Graphene Sheets by Using Eringen's Nonlocal Elasticity Theory and the Perturbation Method
Get PDFA three-dimensional (3D) asymptotic theory is reformulated for the static analysis of simply-supported, isotropic and orthotropic single-layered nanoplates and graphene sheets (GSs), in which Eringen's nonlocal elasticity theory is used to capture the small length scale effect on the static behaviors of these. The perturbation method is used to expand the 3D nonlocal elasticity problems as a series of two-dimensional (2D) nonlocal plate problems, the governing equations of which for various order problems retain the same differential operators as those of the nonlocal classical plate theory (CST), although with different nonhomogeneous terms. Expanding the primary field variables of each order as the double Fourier series functions in the in-plane directions, we can obtain the Navier solutions of the leading-order problem, and the higher-order modifications can then be determined in a hierarchic and consistent manner. Some benchmark solutions for the static analysis of isotropic and orthotropic nanoplates and GSs subjected to sinusoidally and uniformly distributed loads are given to demonstrate the performance of the 3D nonlocal asymptotic theory