scholarly journals Frequency-Dependent Effective Material Parameters of Composites as a Function of Inclusion Shape

10.5772/48769 ◽  
2012 ◽  
Author(s):  
Konstantin N. ◽  
Marina Y. ◽  
Eugene P.
Keyword(s):  
Frequency Dependent ◽  
Material Parameters ◽  
Inclusion Shape

Characterization and Variational Modeling of Ionic Polymer Transducers

2006 ◽  
Vol 129 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Miles A. Buechler ◽  
Donald J. Leo
Keyword(s):  
Variational Approach ◽  
Electromechanical Coupling ◽  
Structural Model ◽  
A Priori ◽  
Effective Strain ◽  
Polymer Materials ◽  
Beam Model ◽  
Frequency Dependent ◽  
Ionic Polymer ◽  
Material Parameters

Ionomeric polymers are a promising class of intelligent material which exhibit electromechanical coupling similar to that of piezoelectric bimorphs. Ionomeric polymers are much more compliant than piezoelectric ceramics or polymers and have been shown to produce actuation strain on the order of 2% at operating voltages between 1V and 3V (Akle et al., 2004, Proceedings IMECE). Their high compliance is advantageous in low force sensing configurations because ionic polymers have a very little impact on the dynamics of the measured system. Here we present a variational approach to the dynamic modeling of structures which incorporate ionic polymer materials. To demonstrate the method a cantilever beam model is developed using this variational approach. The modeling approach requires a priori knowledge of three empirically determined material properties: elastic modulus, dielectric permittivity, and effective strain coefficient. Previous work by Newbury and Leo has demonstrated that these three parameters are strongly frequency dependent in the range between less than 1Hz to frequencies greater than 1kHz. Combining the frequency-dependent material parameters with the variational method produces a second-order matrix representation of the structure. The frequency dependence of the material parameters is incorporated using a complex-property approach similar to the techniques for modeling viscoelastic materials. A transducer is manufactured and the method of material characterization is applied to determine the mtaerial properties. Additional experiments are performed on this transducer and both the material and structural model are validated. Finally, the model is shown to predict sensing response very well in comparison to experimental results, which supports the use of an energy-based variational approach for modeling ionomeric polymer transducers.

ON THE MULTIAXIAL AMPLITUDE- AND FREQUENCY-DEPENDENT BEHAVIOR OF RUBBER: EXPERIMENTS AND CONSTITUTIVE MODELING

2014 ◽  
Vol 87 (3) ◽  
pp. 557-578 ◽  
Author(s):  
Alexis Delattre ◽  
Stéphane Lejeunes ◽  
Stéphane Méo ◽  
Florian Lacroix ◽  
Caroline Richard
Keyword(s):  
Experimental Data ◽  
Constitutive Modeling ◽  
Second Step ◽  
Internal Variables ◽  
Butadiene Rubber ◽  
Robust Method ◽  
Frequency Dependent ◽  
Material Parameters ◽  
Dependent Behavior ◽  
Definition Of

ABSTRACT A phenomenological hyperviscoelastic model is proposed. This model describes the multiaxial amplitude- and frequency-dependent behavior of the material. Moreover, thanks to the definition of new internal variables, the model is able to take into account the Payne effect. The experimental results of a characterization campaign performed on a butadiene rubber filled with carbon black particles are then presented. These tests were conducted under tension/compression and simple shear at several frequencies and amplitudes. Using these experimental data, a fast and robust method is presented to identify the material parameters. There are two steps in this method: the first step regards the hyperelastic behavior and the second step the viscous behavior. The identified model provides good correlations with the tests for describing the dynamical effects under both shear and tension loads.

Ultrasonic characterization of the complex Young’s modulus of polymer parts fabricated with microstereolithography

2018 ◽  
Vol 24 (7) ◽  
pp. 1193-1202 ◽  
Author(s):  
Clinton B. Morris ◽  
John M. Cormack ◽  
Mark F. Hamilton ◽  
Michael R. Haberman ◽  
Carolyn C. Seepersad
Keyword(s):  
Dynamic Response ◽  
Young’S Modulus ◽  
Material Properties ◽  
Dynamic Modulus ◽  
Young's Modulus ◽  
Ultrasonic Waves ◽  
Frequency Dependent ◽  
Content Type ◽  
Material Parameters ◽  
Complex Young’S Modulus

Purpose Microstereolithography is capable of producing millimeter-scale polymer parts having micron-scale features. Material properties of the cured polymers can vary depending on build parameters such as exposure. Current techniques for determining the material properties of these polymers are limited to static measurements via micro/nanoindentation, leaving the dynamic response undetermined. The purpose of this paper is to demonstrate a method to measure the dynamic response of additively manufactured parts to infer the dynamic modulus of the material in the ultrasonic range. Design/methodology/approach Frequency-dependent material parameters, such as the complex Young’s modulus, have been determined for other relaxing materials by measuring the wave speed and attenuation of an ultrasonic pulse traveling through the materials. This work uses laser Doppler velocimetry to measure propagating ultrasonic waves in a solid cylindrical waveguide produced using microstereolithography to determine the frequency-dependent material parameters of the polymer. Because the ultrasonic wavelength is comparable with the part size, a model that accounts for both geometric and viscoelastic dispersive effects is used to determine the material properties using experimental data. Findings The dynamic modulus in the ultrasonic range of 0.4-1.3 MHz was determined for a microstereolithography part. Results were corroborated by using the same experimental method for an acrylic part with known properties and by evaluating the natural frequency and storage modulus of the same microstereolithography part with a shaker table experiment. Originality/value The paper demonstrates a method for determining the dynamic modulus of additively manufactured parts, including relatively small parts fabricated with microstereolithography.

Preceding Stimulus Frequency-Dependent Potentiation of the Postrest Shortening of the Action Potential Duration in Rabbits.

2000 ◽  
Vol 41 (4) ◽  
pp. 481-492
Author(s):  
Naohiko Takahashi ◽  
Morio Ito ◽  
Shuji Ishida ◽  
Takao Fujino ◽  
Mikiko Nakagawa ◽  
...  
Keyword(s):  
Action Potential ◽  
Action Potential Duration ◽  
Stimulus Frequency ◽  
Frequency Dependent ◽  
Preceding Stimulus

Modeling of Rails Expressed using Pade Approximation Considering Frequency Dependent Effect

2017 ◽  
Vol 137 (2) ◽  
pp. 147-153
Author(s):  
Akinori Hori ◽  
Hiroki Tanaka ◽  
Yuichiro Hayakawa ◽  
Hiroshi Shida ◽  
Keiji Kawahara ◽  
...  
Keyword(s):  
Padé Approximation ◽  
Pade Approximation ◽  
Frequency Dependent ◽  
Dependent Effect
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