Characteristics of superplasticity domain in the processing map for hot working of an Al alloy 2014---20vol.%Al2O3 metal matrix composite

The processing map for hot working of Al alloy 2014-20vol.%Al2O3 particulate-reinforced cast-plus-extruded composite material has been generated covering the temperature range 300-500 degrees C and the strain rate range 0.001-10 s(-1) based on the dynamic materials model. The efficiency eta of power dissipation given by 2m/(m + 1), where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of superplasticity has been identified, with a peak efficiency of 62% occurring at 500 degrees C and 0.001 s(-1). The characteristics of this domain have been studied with the help of microstructural evaluation and hot-ductility measurements. Microstructural instability is predicted at higher strain rates above (ls(-1)) and lower temperatures (less than 350 degrees C).

Mechanistic studies on the effect of ferrocene bonding agents in composite solid propellents

Five compounds, viz. 1,1'-ferrocenediyldiethylidene bis(thiocarbonohydrazide) (DAFT), 1,1-diacetylferrocene disemicarbazone (DAFS), 1,1-diacetylferrocenebenzoyl hydrazone (FDBAH), 1,1-diacetylferrocene-p-nitrobenzoyl hydrazone (FDNBAH), and p-toluenesulfonic acid 1,1'-ferrocenediyldiethylidene dihydrazide (TFDD) were found to be bonding agents as well as burning-rate modifiers for the ammonium perchlorate + hydroxy-terminated polybutadiene system. The tensile strength and percentage elongation significantly increased in the presence of these bonding agents (except FDBAH). The bonding agents generally did not adversely affect the slurry viscosity during processing. The bonding sites were located by infrared spectroscopy, supported by determination of the dissolution kinetics of the bonding agents and scanning electron microscopy. The bonding agents did not undergo any side-reactions with the curing agents.

Mechanistic studies on the effect of ferrocene bonding agents in composite solid propellents

Five compounds, viz. 1,1'-ferrocenediyldiethylidene bis(thiocarbonohydrazide) (DAFT), 1,1-diacetylferrocene disemicarbazone (DAFS), 1,1-diacetylferrocenebenzoyl hydrazone (FDBAH), 1,1-diacetylferrocene-p-nitrobenzoyl hydrazone (FDNBAH), and p-tolenesulfonic acid, 1,1'-ferrocenediyldiethylidene dihydrazide (TFDD) were found to be bonding agents as well as burning-rate modifiers for the ammonium perchlorate + hydroxy-terminated polybutadiene system. The tensile strength and percentage elongation significantly increased in the presence of these bonding agents (except FDBAH). The bonding agents generally did not adversely affect the slurry viscosity during processing. The bonding sites were located by infrared spectroscopy, supported by determination of the dissolution kinetics of the bonding agents and scanning electron microscopy. The bonding agents did not undergo any side-reactions with the curing agents.

Composite material and piezoelectric coefficient uncertainty effects on structural health monitoring using feedback control gains as damage indicators

This article addresses uncertainty effect on the health monitoring of a smart structure using control gain shifts as damage indicators. A finite element model of the smart composite plate with surface-bonded piezoelectric sensors and actuators is formulated using first-order shear deformation theory and a matrix crack model is integrated into the finite element model. A constant gain velocity/position feedback control algorithm is used to provide active damping to the structure. Numerical results show that the response of the structure is changed due to matrix cracks and this change can be compensated by actively tuning the feedback controller. This change in control gain can be used as a damage indicator for structural health monitoring. Monte Carlo simulation is conducted to study the effect of material uncertainty on the damage indicator by considering composite material properties and piezoelectric coefficients as independent random variables. It is found that the change in position feedback control gain is a robust damage indicator.

Ionic Polymer Metal Composite Flapping Actuator Mimicking Dragonflies

In this study, variational principle is used for dynamic modeling of an Ionic Polymer Metal Composite (IPMC) flapping wing. The IPMC is an Electro-active Polymer (EAP) which is emerging as a useful smart material for `artificial muscle' applications. Dynamic characteristics of IPMC flapping wings having the same size as the actual wings of three different dragonfly species Aeshna Multicolor, Anax Parthenope Julius and Sympetrum Frequens are analyzed using numerical simulations. An unsteady aerodynamic model is used to obtain the aerodynamic forces. A comparative study of the performances of three IPMC flapping wings is conducted. Among the three species, it is found that thrust force produced by the IPMC flapping wing of the same size as Anax Parthenope Julius wing is maximum. Lift force produced by the IPMC wing of the same size as Sympetrum Frequens wing is maximum and the wing is suitable for low speed flight. The numerical results in this paper show that dragonfly inspired IPMC flapping wings are a viable contender for insect scale flapping wing micro air vehicles.

Nonlinear static and dynamic damped response of a composite rectangular plate resting on a two-parameter elastic foundation

Nonlinear static and dynamic response analyses of a clamped. rectangular composite plate resting on a two-parameter elastic foundation have been studied using von Karman's relations. Incorporating the material damping, the governing coupled, nonlinear partial differential equations are obtained for the plate under step pressure pulse load excitation. These equations have been solved by a one-term solution and by applying Galerkin's technique to the deflection equation. This yields an ordinary nonlinear differential equation in time. The nonlinear static solution is obtained by neglecting the time-dependent variables. Thc nonlinear dynamic damped response is obtained by applying the ultraspherical polynomial approximation (UPA) technique. The influences of foundation modulus, shear modulus, orthotropy, etc. upon the nonlinear static and dynamic responses have been presented.