scholarly journals Comparison of two different modeling approaches to describe the non-linear viscoelastic behavior of filled rubber material

PAMM ◽  
2016 ◽  
Vol 16 (1) ◽  
pp. 389-390
Author(s):  
Tobias Scheffer ◽  
Stefan Diebels
2005 ◽  
Vol 78 (1) ◽  
pp. 54-75 ◽  
Author(s):  
Jean L. Leblanc

Abstract Fourier transform (FT) rheometry was used to investigate the non-linear viscoelastic behavior of a series of carbon black filled rubber compounds with various filler levels. Using a purposely modified commercial dynamic rheometer, i.e. the Rubber Process Analyzer RPA 2000® (Alpha Technologies), special strain sweep tests protocols were designed and performed in order to capture the actual strain and torque signals up to 500% deformation at constant frequency and temperature. FT yielded the main component and harmonics of strain and torque signals. Results show that the quality of the applied strain signal somewhat deteriorates with increasing stiffness of filled compounds, but remains excellent in the high strain region, where the non-linear viscoelastic response of the materials is investigated. Above a filler volume fraction of around 12–13%, tested materials no longer exhibit a linear viscoelastic response, at least in the strain window investigated, and the FT rheometry results are more complex than what was observed with pure gum samples. This means that most practical rubber compounds are intrinsically non-linear. By essence, FT rheometry is a valid technique for both the linear and the non-linear domains and, as shown, provides original information about complex polymer systems such as filled rubber compounds.


Author(s):  
Pouria Khanbolouki ◽  
Mehran Tehrani

Coiled structures made from polymer and Carbon Nanotube (CNT) yarns are used as artificial muscles, stretchable conductors, and energy harvesters. The purpose of this work is to present our latest understanding of the mechanical behavior of these CNT-based structures. CNT yarns are fabricated by inserting twists in sheets spun from CNT forests. Over twisting the CNT yarns results in coiled CNT yarns, similar to a spring where the spring radius is comparable to the diameter of the CNT yarn. In this study, we explain the development and validation of a viscoelastic model, to capture damping and hysteresis in CNT yarns under quasi-static and dynamic loads. Confirmation of linear viscoelastic behavior of CNT yarns can lead us to the development of a model for coiled CNT yarns. Coiled CNT yarns, on the other hand, show a complex non-linear viscoelastic behavior. Possible mechanisms responsible for this non-linear behavior are discussed.


1999 ◽  
Vol 38 (1) ◽  
pp. 14-25 ◽  
Author(s):  
F. Yziquel ◽  
P. J. Carreau ◽  
P. A. Tanguy

Author(s):  
Jinjin Ma ◽  
Ellen M. Arruda

Patellar tendon (PT) autografts and allografts are the most common methods currently used to replace a torn anterior cruciate ligament (ACL). The PT is not only much stiffer than the ACL it replaces it also exhibits qualitatively and quantitatively different non-linear viscoelastic behavior from those of the ACL. These mis-matched biomechanics may be contributing to the high incidence of early onset osteoarthritis suffered by patients who have had ACL surgeries. Thus there is a need for an ACL graft that can reproduce normal ligament biomechanics and knee function. This talk examines the inhomogeneous, non-linear viscoelastic response of native ACL and of a tissue engineered ACL graft designed to rapidly grow and remodel in vivo to restore the proper biomechanical properties of native ligament. The results using this graft as an ACL replacement are compared against those using a PT autograft for the ACL replacement. Uniaxial loading reveals that after nine months as an ACL replacement, the tissue-engineered graft develops a strain contour pattern closely resembling that of native ACL whereas the PT graft fails to similarly remodel in vivo.


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