Faruk Taban, Shen-Yi Luo, Cahit A. Evrensel and Aniruddha Mitra*
Department of Mechanical Engineering
University of Nevada, Reno
Reno, NV 89557
*Western Nevada Community College
Carson City, NV 89703
INTRODUCTION
The stress-strain curves of the fabric flexible composites and the soft
tissues under various biaxial loads appear to be similar. They all
contain curved fibers in soft matrices. Because of the curved fibers,
inhomogeneous deformation occurs within the material. Most researchers
believe that the uniaxial data cannot be used to characterize multiaxial
behavior of the soft tissues in general. The constitutive equation
obtained using data regression method usually gives a good description of
the stress-strain behavior for the homogeneous material. It gives no
physical meaning of these input values obtained for the soft tissues.
Thus, these constitutive relations are highly dependent on the
experimental procedure and cannot be generalized.
This study investigates a generalized model to predict the biaxial
behavior of the soft tissues (such as cardiac muscle, skin, lung, blood
vessel, etc.) using modified fabric flexible composite theory. It treats
the soft tissue as an orthogonal composite element containing wavy fibers
in a soft matrix. Input parameters of the model are determined from
uniaxial tests analytically with physical meaning. Good agreement has
been found between the experimental measurements and the theoretical
predictions for the soft tissues.
METHOD
Cardiac and lung tissues have been chosen to test the prediction of the
model. We consider those tissues to be composed of wavy fibers in an
isotropic matrix, which represents all non-fibrous constituents. The
phenomenon and the details of the fabric model are given by Taban and Luo,
(1997) and Mitra and Luo (1994). Only the modifications to it and its
input data are discussed herein.