ANTICYTOSKELETAL DRUGS AND TIME CULTURE EFFECTS UPON THE MECHANICAL BEHAVIOR OF DERMAL EQUIVALENT TISSUE SUBMITTED TO UNCONFINED COMPRESSION LOADING

2008 ◽  
Vol 08 (03) ◽  
pp. 339-352 ◽  
Author(s):  
S. RAMTANI ◽  
D. GEIGER
Keyword(s):  
Mechanical Behavior ◽  
Internal State ◽  
Skin Grafting ◽  
Biological Tissues ◽  
Matrix Remodeling ◽  
Unconfined Compression ◽  
Compression Loading ◽  
Dermal Equivalent ◽  
Variable Approach ◽  
Time Culture

The dermal equivalent (DE), a dermis substitute consisting of human skin fibroblasts growing into a three-dimensional collagen matrix, is extensively used in many applications: wound-healing response, pharmacological studies, skin grafting, fibroblast proliferation and migration, extracellular matrix remodeling, and efficacy of cosmetic products. The widespread growth of numerical modeling in biomechanical research has placed a heightened emphasis on accurate material property data for soft biological tissues, in particular for equivalent dermis which has not been so thoroughly investigated. Under unconfined compression loading, the effects of the strain rate, time culture, and cytoskeleton-disrupting agents are experimentally investigated. In order to model the observed mechanical behavior of the DE under the above conditions, the internal state variable approach is adopted for finite deformation viscoelasticity and the optimized material parameters are identified with respect to the stated thermodynamic restriction (i.e. positive viscous dissipation).

Modeling the Large Deformation and Microstructure Evolution of Nonwoven Polymer Fiber Networks

2018 ◽  
Vol 86 (1) ◽  
Author(s):  
Mang Zhang ◽  
Yuli Chen ◽  
Fu-pen Chiang ◽  
Pelagia Irene Gouma ◽  
Lifeng Wang
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Mechanical Behavior ◽  
Large Deformation ◽  
Biological Tissues ◽  
High Porosity ◽  
Polymer Fiber ◽  
Fiber Networks ◽  
Fiber Aspect Ratio ◽  
Network Microstructure

The electrospinning process enables the fabrication of randomly distributed nonwoven polymer fiber networks with high surface area and high porosity, making them ideal candidates for multifunctional materials. The mechanics of nonwoven networks has been well established for elastic deformations. However, the mechanical properties of the polymer fibrous networks with large deformation are largely unexplored, while understanding their elastic and plastic mechanical properties at different fiber volume fractions, fiber aspect ratio, and constituent material properties is essential in the design of various polymer fibrous networks. In this paper, a representative volume element (RVE) based finite element model with long fibers is developed to emulate the randomly distributed nonwoven fibrous network microstructure, enabling us to systematically investigate the mechanics and large deformation behavior of random nonwoven networks. The results show that the network volume fraction, the fiber aspect ratio, and the fiber curliness have significant influences on the effective stiffness, effective yield strength, and the postyield behavior of the resulting fiber mats under both tension and shear loads. This study reveals the relation between the macroscopic mechanical behavior and the local randomly distributed network microstructure deformation mechanism of the nonwoven fiber network. The model presented here can also be applied to capture the mechanical behavior of other complex nonwoven network systems, like carbon nanotube networks, biological tissues, and artificial engineering networks.

On the Ability of Structural and Phenomenological Hyperelastic Models to Predict the Mechanical Behavior of Biological Tissues Submitted to Multiaxial Loadings

2012 ◽  
Author(s):  
Mathieu Nierenberger ◽  
Yves Rémond ◽  
Saïd Ahzi
Keyword(s):  
Experimental Data ◽  
Mechanical Behavior ◽  
Strain Energy ◽  
Soft Tissues ◽  
Least Squares Method ◽  
Biological Tissues ◽  
Physical Parameters ◽  
Cauchy Stress ◽  
Specific Loading ◽  
Hyperelastic Models

Medical surgery is currently rapidly improving and requires modeling faithfully the mechanical behavior of soft tissues. Various models exist in literature; some of them created for the study of biological materials, and others coming from the field of rubber mechanics. Indeed biological tissues show a mechanical behavior close to the one of rubbers. But while building a model, one has to keep in mind that its parameters should be loading independent and that the model should be able to predict the behavior under complex loading conditions. In addition, keeping physical parameters seems interesting since it allows a bottom up approach taking into account the microstructure of the material. In this study, the authors consider different existing hyperelastic models based on strain energy functions and identify their coefficients successively on single loading stress-stretch curves. The experimental data used, come from a paper by Zemanek dated 2009 and concerning uniaxial, equibiaxial and plane tension tests on porcine arterial walls taken in identical experimental conditions. To achieve identification, the strain energy function of each model is derived differently to provide an expression of the Cauchy stress associated to each loading case. Firstly the parameters of each model are identified on the uniaxial tension curve using a least squares method. Then, keeping the obtained parameters, predictions are made for the two other loading cases (equibiaxial and plane tension) using the associated expressions of stresses. A comparison of these predictions with experimental data is done and allows evaluating the predictive capabilities of each model for the different loading cases. A similar approach is used after swapping the loading types. Since the predictive capabilities of the models are really dependent on the loading chosen to determine their parameters, another type of identification procedure is set up. It consists in adding the residues over the three loading cases during identification. This alternative identification method allows a better agreement between each model and the various types of experiments. This study evaluated the ability of some classical hyperelastic models to be used for a predictive scope after being identified on a specific loading type. Besides it brought to light some existing models which can describe at best the mechanical behavior of biological tissues submitted to various loadings.

scholarly journals Strain rate effect on the mechanical behavior of polyamide composites under compression loading

2019 ◽  
Vol 214 ◽  
pp. 114-122 ◽  
Author(s):  
Abdellah Massaq ◽  
Alexis Rusinek ◽  
Maciej Klosak ◽  
Slim Bahi ◽  
Angel Arias
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Compression Loading

Unconfined Compression of Articular Cartilage: Nonlinear Behavior and Comparison With a Fibril-Reinforced Biphasic Model

1999 ◽  
Vol 122 (2) ◽  
pp. 189-195 ◽  
Author(s):  
M. Fortin ◽  
J. Soulhat ◽  
A. Shirazi-Adl ◽  
E. B. Hunziker ◽  
M. D. Buschmann
Keyword(s):  
Articular Cartilage ◽  
Mechanical Behavior ◽  
Small Amplitude ◽  
Dynamic Stiffness ◽  
Scaling Law ◽  
Nonlinear Behavior ◽  
Hydraulic Permeability ◽  
Unconfined Compression ◽  
Biphasic Model ◽  
Strain Dependent

Mechanical behavior of articular cartilage was characterized in unconfined compression to delineate regimes of linear and nonlinear behavior, to investigate the ability of a fibril-reinforced biphasic model to describe measurements, and to test the prediction of biphasic and poroelastic models that tissue dimensions alter tissue stiffness through a specific scaling law for time and frequency. Disks of full-thickness adult articular cartilage from bovine humeral heads were subjected to successive applications of small-amplitude ramp compressions cumulating to a 10 percent compression offset where a series of sinusoidal and ramp compression and ramp release displacements were superposed. We found all equilibrium behavior (up to 10 percent axial compression offset) to be linear, while most nonequilibrium behavior was nonlinear, with the exception of small-amplitude ramp compressions applied from the same compression offset. Observed nonlinear behavior included compression-offset-dependent stiffening of the transient response to ramp compression, nonlinear maintenance of compressive stress during release from a prescribed offset, and a nonlinear reduction in dynamic stiffness with increasing amplitudes of sinusoidal compression. The fibril-reinforced biphasic model was able to describe stress relaxation response to ramp compression, including the high ratio of peak to equilibrium load. However, compression offset-dependent stiffening appeared to suggest strain-dependent parameters involving strain-dependent fibril network stiffness and strain-dependent hydraulic permeability. Finally, testing of disks of different diameters and rescaling of the frequency according to the rule prescribed by current biphasic and poroelastic models (rescaling with respect to the sample’s radius squared) reasonably confirmed the validity of that scaling rule. The overall results of this study support several aspects of current theoretical models of articular cartilage mechanical behavior, motivate further experimental characterization, and suggest the inclusion of specific nonlinear behaviors to models. [S0148-0731(00)00702-0]

scholarly journals Viscoelastic and poroelastic mechanical characterization of hydrated gels

2009 ◽  
Vol 24 (3) ◽  
pp. 973-979 ◽  
Author(s):  
Matteo Galli ◽  
Kerstyn S.C. Comley ◽  
Tamaryn A.V. Shean ◽  
Michelle L. Oyen
Keyword(s):  
Elastic Modulus ◽  
Mechanical Behavior ◽  
Mechanical Characterization ◽  
Element Model ◽  
Mechanical Analysis ◽  
Intrinsic Permeability ◽  
Unconfined Compression ◽  
Future Studies ◽  
Dependent Behavior

Measurement of the mechanical behavior of hydrated gels is challenging due to a relatively small elastic modulus and dominant time-dependence compared with traditional engineering materials. Here polyacrylamide gel materials are examined using different techniques (indentation, unconfined compression, dynamic mechanical analysis) at different length-scales and considering both viscoelastic and poroelastic mechanical frameworks. Elastic modulus values were similar for nanoindentation and microindentation, but both indentation techniques overestimated elastic modulus values compared to homogeneous loading techniques. Hydraulic and intrinsic permeability values from microindentation tests, deconvoluted using a poroelastic finite element model, were consistent with literature values for gels of the same composition. Although elastic modulus values were comparable for viscoelastic and poroelastic analyses, time-dependent behavior was length-scale dependent, supporting the use of a poroelastic, instead of a viscoelastic, framework for future studies of gel mechanical behavior under indentation.

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