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Various Aspect Ratios (various + aspect_ratio)

Distribution by Scientific Domains
Polymers and Materials Science50%
Engineering50%

Selected Abstracts

Fabrication and Electromechanical Characterization of a Piezoelectric Structural Fiber for Multifunctional Composites

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
Yirong Lin
Abstract The use of piezoceramic materials for structural sensing and actuation is a fairly well developed practice that has found use in a wide variety of applications. However, just as advanced composites offer numerous benefits over traditional engineering materials for structural design, actuators that utilize the active properties of piezoelectric fibers can improve upon many of the limitations encountered when using monolithic piezoceramic devices. Several new piezoelectric fiber composites have been developed; however, almost all studies have implemented these devices such that they are surface-bonded patches used for sensing or actuation. This paper will introduce a novel active piezoelectric structural fiber that can be laid up in a composite material to perform sensing and actuation, in addition to providing load bearing functionality. The sensing and actuation aspects of this multifunctional material will allow composites to be designed with numerous embedded functions, including structural health monitoring, power generation, vibration sensing and control, damping, and shape control through anisotropic actuation. This effort has developed a set of manufacturing techniques to fabricate the multifunctional fiber using a SiC fiber core and a BaTiO3 piezoelectric shell. The electromechanical coupling of the fiber is characterized using an atomic force microscope for various aspect ratios and is compared to predictions made using finite element modeling in ABAQUS. The results show good agreement between the finite element analysis model and indicate that the fibers could have coupling values as high as 68% of the active constituent used. [source]

Stress analyses of laminates under cylindrical bending

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 1 2008
Tarun Kant
Abstract A semi-analytical approach for evaluation of stresses and displacements in composite and sandwich laminates under cylindrical bending subjected to transverse load has been developed in this paper. Two dimensional (2D) partial differential equations (PDEs) of such a laminate are obtained by imposing plane-strain conditions of elasticity. The fundamental dependent variables are so selected in this formulation that they satisfy the continuity of displacements and transverse interlaminar stresses at the laminate interface through the thickness. The set of governing PDEs are transformed into a set of coupled first-order ordinary differential equations (ODEs) in thickness direction by assuming suitable global orthogonal trigonometric functions for the fundamental variables satisfying the boundary conditions. These ODEs are numerically integrated by a specially formulated ODE integrator algorithm involving transformation of a two-point boundary value problem (BVP) into a set of initial value problems (IVPs). Numerical studies on both composite and sandwich laminates for various aspect ratios are performed and presented. Accuracy of the present approach is demonstrated by comparing the results with the available elasticity solution. It is seen that the present results are in excellent agreement with the elasticity solutions. Some new results for sandwich laminates and for uniform loading condition are presented for future reference. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Global flow instability in a lid-driven cavity

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2010
V. B. L. Boppana
Abstract The stability of flow in a lid-driven cavity is investigated using an accurate numerical technique based on a hybrid scheme with spectral collocation and high-order finite differences. A global stability analysis is carried out and critical parameters are identified for various aspect ratios. It is found that while there is reasonable agreement with the literature for the critical parameters leading to loss of stability for the square cavity, there are significant discrepancies for cavities of aspect ratios 1.5 and 2. Simulations of the linearized unsteady equations confirm the results from the global stability analysis for aspect ratios A = 1, 1.5 and A = 2. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Two Photon Polymerization of Polymer,Ceramic Hybrid Materials for Transdermal Drug Delivery

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2007
A. Ovsianikov
Three-dimensional microneedle devices were created by femtosecond laser two photon polymerization (2PP) of organically modified ceramic (Ormocer®) hybrid materials. Arrays of in-plane and out-of-plane hollow microneedles (microneedle length=800 ,m, microneedle base diameter=150,300 ,m) with various aspect ratios were fabricated. The fracture and penetration properties of the microneedle arrays were examined using compression load testing. In these studies, the microneedle arrays penetrated cadaveric porcine adipose tissue without fracture. Human epidermal keratinocyte viability on the Ormocer® surfaces polymerized using 2PP was similar to that on control surfaces. These results suggest that 2PP is able to create microneedle structures for transdermal drug delivery with a larger range of geometries than conventional microfabrication techniques. [source]