Low-Velocity Impact Dynamic Behavior of Laminated Composite Nonprismatic Folded Plate Structures

In this paper, the higher-order shear deformation theory is used to study the response of graphite/epoxy laminated composite nonprismatic folded plates subjected to impact loads. A finite-element model of the theory is also developed. The modified Hertzian contact law incorporated within the Newton–Raphson method is used to calculate the contact force between the impactor and the laminated plate. For time integration, the Newmark direct integration was adopted. Numerical results are presented to demonstrate the effects of span-to-thickness ratio, fiber angle, stacking sequence, and crank angle on the response of laminated plate subjected to impact. It is demonstrated that the results obtained from the present investigation compare well with those reported in the open literature.     

Characterization of particleboards of African mahogany sawdust made with tannic powders of Bridelia and African locust bean pods

European Journal of Wood and Wood Products - The purpose of this study was to valorize African mahogany wood, especially its residues (sawdust) from carpentry, in the manufacturing of...     

Rapid processing & characterization of micro-scale functionally graded porous materials

Spark plasma sintering (SPS) is a process that has stimulated worldwide interest for the rapid consolidation of powder-based materials through the combined effects of electric current and pressure. Recently the localization of SPS has been realized through current activated tip-based sintering (CATS) where electric current is selectively applied to small targeted regions of a green compact/powder bed via a precision controlled electrically conductive small tip. The unique tip-specimen geometry allows for locally controlled temperature and current distributions that can result in microstructural modifications on the micro-scale. The present paper presents for the first time the rapid processing and characterization of micro-scale functionally graded materials in relation to porosity content and size. The effects of initial green density and particle size on the developed micro-scale functionally graded material are discussed.     

Comparative study of tuning of microfabrication parameters for improving electrochemical performance of platinum and glassy carbon microelectrodes in neural prosthetics

Neural prosthetics, which are increasingly being considered for the dual functionalities of recording and stimulation, are implanted in a corrosive biochemical environment that requires them to possess superior electrical and electrochemical stability and performance. These probes are required to withstand these operating conditions through billions of cycles of pulses of electrical stimulations and also maintain electrochemical sensitivity for potential applications in voltammetry. In this research, microelectrodes made of two material systems; namely, platinum and glassy carbon, supported on a flexible substrate are fabricated and investigated for correlation between process parameters and the electrochemical efficacy of the neural interfaces, particularly charge storage capacity and corrosion rate. Using scanning electron and atomic force microscopies, the correlation between process parameters, surface morphology and topography in both platinum and glassy carbon were investigated. The results demonstrate that changes in surface topography and the rate of corrosion are correlated to variations in the process parameters. Furthermore, the results indicate a relationship between surface roughness and corrosion rate, in which the increase or decrease of the former corresponds to a similar change in the latter.

     

Effects of current intensity and cumulative exposure time on the localized current-activated sintering of titanium nickelides

This article discusses the processing and properties of titanium nickelides locally sintered via Current-Activated Tip-based Sintering (CATS), a new localized sintering process. One of the advantages of CATS is the ability to apply orders of magnitude higher current densities than conventionally possible, which can promote rapid sintering and phase transformation rates. Mechanically alloyed equi-atomic Ni–Ti powder was for the first time tip sintered at varying current intensities and cumulative current exposure time. The effect of current-control processing conditions on the evolution of the locally sintered Ni–Ti microstructure and properties are discussed. The size of the locally sintered process zone was found to increase with cumulative current exposure time. The degree of sintering, phase transformations, and properties were found to depend on the current intensity, cumulative current exposure time and distance away from the tip/compact interface. Fully/near fully dense material was achieved rapidly at locations exposed to the highest current densities.