This work describes the effect of the speed of drum-type rotating collector in an electrospinning process on the orientation of electrospun poly(butylene terephthalate) fiber mats, and its effect on the tensile properties. The degree of orientation increased with the increase in the drum speed (surface velocity) up to a critical level, and thereafter, wavy fibers were observed. The average diameter reduced and its distribution became narrower with increase in the velocity. The mechanical properties in a parallel direction improved about three times with increase in the surface velocity. The anisotropic mechanical behavior could be predicted with a simple classical equation.

This paper presents a description and a set of experimental results on Ionic Polymer‐Metal Composites (IPMC's) as dynamic sensors, transducers, and actuators. Strips of IPMC can exhibit large dynamic deformation if placed in a time‐varying electric field of the order of 10's of volts/mm. Conversely, dynamic deformation and flexing of such ionic polymers produces dynamic electric fields that closely follow the form of the electric signal. The underlying principle of such a mechanoelectric effect in IPMC's can be explained by the linear irreversible thermodynamics in which ion and solvent transport are the fluxes and electric field and solvent pressure gradient are the forces. Important parameters include the material conductance and the solvent permeability. The dynamic sensing, transduction, and actuation responses of a strip of IPMC under an impact‐type loading is also discussed. When a cantilever strip of IPMC is flipped, a damped oscillatory electric response is produced across a pair of electrodes placed at the cantilever of the strip, which is highly repeatable with a broad frequency range above 104 Hz. Such direct mechanoelectric responses of IMPC's are related to the endo‐ionic mobility due to stresses imposed. Imposition of a finite solvent flux without allowing a current flux causes the material to create a certain conjugate electric field that can be dynamically monitored and measured. IPMC's are shown to be highly capacitive at low frequencies while they are highly resistive under high frequency excitations. IN a sending mode, IPMC strips can also sense chemical environments and humidity. These types of sensors/transducers/actuators conceivably can replace piezoresistive and piezoelectric sensors with just one sensor for broad ranges of frequencies.

This study investigated the feasibility of using active structural acoustic control with monolithic piezoceramic actuators to reduce the low frequency noise transmission through rocket fairings during launch. Closed-loop simulation results are presented using a fully coupled structural acoustic model of a lightly damped composite fairing structure with integrated piezoceramic actuators. Constraints were placed on controller mass and maximum allowable actuator voltage in order to provide a baseline of reasonable expected performance. Realistic disturbance levels were used in the simulations, and two disturbance cases were considered with significantly different spectral characteristics. Simulations were conducted to compare the effects of actuator thickness, covered surface area, and maximum actuator voltage on controller performance and energy requirements. Linear Quadratic Regulator control laws were computed assuming full-state feedback using three design approaches. The results provide significant insight into the noise transmission problem and to the physical dynamics of the control approach. The best-case reduction in the spatially averaged interior acoustic response was determined to be approximately 2.5 dB over the 0-300 Hz bandwidth.

A new fabrication system for Ionic Polymer Metallic Composites (IPMC) entitled Micro Deposition Method(MDM) is introduced. The tolerances in prototyping IPMC's using available fabrication techniques does not meet the tight limits for fabricating the polymer transducer. The MDM overcomes this limitation by using a microfluidic dispersion head that can deposit 3 to 10 picoliters of the electrode layer dissolved in a solvent at a high throughput. The MDM in its existing configuration can be used to fabricate micron scale polymer transducers with features 2 microns and above with high accuracy and repeatability. A commercially available piezoelectric deposition head from an inkjet printer is modified and used to disperse the electrode material of controlled thickness as a concept demonstration. The physical properties of the dispersed fluid are adjusted to meet the requirements of the deposition head to fabricate the prototype. The dispersion fluid used had a viscosity of 3.47 ±0.06 cP, a surface tension of 23.6 ±.1 mNm -1 , and a conducting power volume load set at 10%.

A three-dimensional structural constitutive equation is proposed to describe the mechanical properties of poly(butylene terephthalate) nanofibers mats. The model is formulated under the assumption that the mechanical response of the fibrous mat is determined by the individual fibers. The inelasticity, which has been observed when subjecting the fibrous mat to tensile tests, is assumed to be due to the gradual breakage of linear elastic fibers. The constitutive relation also takes the material anisotropy associated with the fibers' architecture into account. Uniaxial experimental data were used to assess the proposed model. The results demonstrate that the model is well suited to reproduce the typical tensile behavior of the fibrous mat. In agreement with the empirical observations, the model predicts that almost all the fibers fail when the poly(butylene terephthalate) fibrous mat sample breaks. Nevertheless, multiaxial stress-strain data and quantification of the fibers' orientation are required to completely validate the constitutive law.