Elucidation of Microstructural Interactions Between Collagen and Non-Fibrillar Matrix in Soft Tissue Using a Coupled Fiber-Matrix Model

2012 ◽  
Author(s):  
Lijuan Zhang ◽  
Spencer P. Lake ◽  
Victor K. Lai ◽  
Victor H. Barocas ◽  
Mark S. Shephard
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Tensile Load ◽  
Matrix Composites ◽  
Collagen Network ◽  
Fiber Network ◽  
Matrix Modeling ◽  
Microscale Model ◽  
Fiber Matrix

The mechanical properties of soft connective tissues are governed by their collagen fiber network and surrounding non-fibrillar matrix (e.g., proteoglycans, cells, elastin, etc.). In order to understand how healthy tissues function, and how properties change in injury and disease, it is necessary to quantify the mechanical response of both the collagen network and the non-fibrillar matrix (NFM), as well as the nature of the interaction between these tissue constituents. Using collagen-agarose co-gels as a simple experimental tissue analog system, we have demonstrated how NFM contributes to the mechanical and organizational properties of soft tissues in indentation and tension [1–2]. Furthermore, we used a network-based microscale model to examine how specific NFM properties alter the response of fiber-matrix composites under load [3]. This model fit our experimental data well and provided insight into the role of NFM in tensile mechanics. Since it was constructed according to the conventional approach of superposition of the two constituents (collagen network and NFM), however, the model could not specifically examine local interactions between collagen fibers and the surrounding NFM, which could be critical in assessing tissue damage or cell-matrix interactions. Therefore, we developed and evaluated a fiber-matrix modeling scheme to characterize the microstructural interactions between tissue constituents, as well as to quantify the role of individual tissue components in the behavior of soft tissues under tensile load. For validation, the new model (‘coupled’) was compared to our previous model (‘parallel’) and to experimental co-gel data.

Change in Mechanical Response of Arterial Elastin due to Glycation

2012 ◽  
Author(s):  
Beth Stephen ◽  
Theresa A. Good ◽  
L. D. Timmie Topoleski
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Tensile Load ◽  
Material Response ◽  
Biochemical Processes ◽  
High Stiffness ◽  
Health And Disease ◽  
Low Stiffness ◽  
The Individual

Collagen and elastin are the primary load-bearing components of arteries. Elastin is a low strength, highly elastic, fibrous material and collagen is a stiffer material, generally present as wavy fibers when unstretched. Together, they account for the material response of arteries under tensile load. Arteries, and other soft tissues, exhibit a two-part material response to tensile load. There is an initial low stiffness response at low stretch followed by a high stiffness response at higher stretch. It has been proposed that the low stiffness response is dominated by the elastin in the material and the high stiffness response is dominated by collagen [1]. The elastin accounts for the initial low stiffness response of the material, until the wavy collagen fibers straighten and become engaged, at which point the material transitions to its higher stiffness response. It is important to understand the role of the individual collagen and elastin components and how they contribute to the overall mechanical response of the arteries. Further, it is important to understand how specific biochemical processes that occur with age and disease affect the mechanical response of the individual collagen and elastin components and consequently the overall mechanical response of the arteries. This knowledge will increase our understanding of arterial mechanical response and how this response changes arterial function in health and disease.

Evaluation of Mechanical Properties and Comprehensive Modeling of CMC with Stiff and Weak Matrices

2006 ◽  
Vol 45 ◽  
pp. 1435-1443 ◽  
Author(s):  
Dietmar Koch ◽  
Kamen Tushtev ◽  
Jürgen Horvath ◽  
Ralf Knoche ◽  
Georg Grathwohl
Keyword(s):  
Mechanical Properties ◽  
Mechanical Response ◽  
Ceramic Matrix Composites ◽  
High Strength ◽  
Shear Mode ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Strain Behavior ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

The mechanical properties of ceramic matrix composites (CMC) depend on the individual properties of fibers and matrix, the fiber-matrix interface, the microstructure and the orientation of the fibers. The fiber-matrix interface of ceramics with stiff matrices (e.g. CVI-derived SiC/SiC) must be weak enough to allow crack deflection and debonding in order to achieve excellent strength and strain to failure (weak interface composites WIC). This micromechanical behavior has been intensively investigated during the last 20 years. With the development of CMC with weak matrices (weak matrix composites WMC) as e.g. oxide/oxide composites or polymer derived CMC the mechanical response can not be explained anymore by these models as other microstructural mechanisms occur. If the fibers are oriented in loading direction in a tensile test the WMC behave almost linear elastic up to failure and show a high strength. Under shear mode or if the fibers are oriented off axis a significant quasiplastic stress-strain behavior occurs with high strain to failure and low strength. This complex mechanical behavior of WMC will be explained using a finite element (FE) approach. The micromechanical as well as the FE models will be validated and attributed to the different manufacturing routes.

Multiscale Adaptive Finite Element Computations for Soft Tissue Biomechanics

2007 ◽  
Author(s):  
Triantafyllos Stylianopoulos ◽  
Xiaojuan Luo ◽  
Mark S. Shephard ◽  
Victor H. Barocas
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Length Scale ◽  
Adaptive Finite Element ◽  
Mechanical Function ◽  
Collagen Network ◽  
Acceptable Solution ◽  
Soft Tissue Biomechanics ◽  
Network Orientation ◽  
Collagenous Tissues

The mechanical function of soft collagenous tissues is inherently multiscale, with the tissue dimension being in the centimeter length scale and the underlying collagen network being in the micrometer length scale. The strong sensitivity of soft tissues to network orientation and fiber-fiber interactions necessitates the incorporation of both scales in a multiscale methodology [1,2] in order to predict their mechanical response. The computational demands of a multiscale methodology, however, are strenuous and the use of parallel processing and adaptivity are required for succeeding acceptable solution times.

Collagen-Agarose Co-Gels as a Model for Collagen-Matrix Interaction in Soft Tissue

2011 ◽  
Author(s):  
Spencer P. Lake ◽  
Sadie Doggett ◽  
Victor H. Barocas
Keyword(s):  
Collagen Fiber ◽  
Type I Collagen ◽  
Soft Tissues ◽  
Experimental System ◽  
Model System ◽  
Type I ◽  
Collagen Gels ◽  
Fiber Network ◽  
Fibrillar Material

Connective soft tissues have complex mechanical properties that are determined by their collagen fiber network and surrounding non-fibrillar material. The mechanical role of non-fibrillar material and the nature of its interaction with the collagen network remain poorly understood, in part because of the lack of a simple experimental model system to examine and quantify these properties. The development of a simple but representational experimental system will allow for greater insight into the interaction between fibers and the non-fibrillar matrix. Reconstituted Type I collagen gels are an attractive model tissue for exploring micro- and macroscale relationships between constituents (e.g., [1–2]), but standard collagen gels lack the non-fibrillar components (i.e., proteoglycan, minor collagens, etc.) present in native tissue. A recent study [3] added low quantities of agarose to collagen gels, which dramatically increased the shear storage modulus with minimal changes to the collagen fiber network. In this study, we suggest that collagen-agarose co-gels can serve as a model system to investigate the mechanical role of non-fibrillar ECM. Even though agarose is relatively compliant at low concentrations, and collagen fibers are very stiff in tension, we hypothesized that the presence of agarose in co-gels would have a pronounced effect on structural response and mechanical behavior in tensile loading. Therefore, the objective of this study was to examine the properties of collagen-agarose co-gels to understand better the nature of, and the relationships between, the collagen fiber network and non-fibrillar matrix of simplified tissue analogs.

scholarly journals A Coupled Fiber-Matrix Model Demonstrates Highly Inhomogeneous Microstructural Interactions in Soft Tissues Under Tensile Load

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Lijuan Zhang ◽  
Spencer P. Lake ◽  
Victor K. Lai ◽  
Catalin R. Picu ◽  
Victor H. Barocas ◽  
...  
Keyword(s):  
Stress Field ◽  
Matrix Model ◽  
Collagen Fiber ◽  
Soft Tissues ◽  
Computational Cost ◽  
Parallel Model ◽  
Fiber Network ◽  
Detailed Model ◽  
The Matrix ◽  
Fiber Matrix

A soft tissue's macroscopic behavior is largely determined by its microstructural components (often a collagen fiber network surrounded by a nonfibrillar matrix (NFM)). In the present study, a coupled fiber-matrix model was developed to fully quantify the internal stress field within such a tissue and to explore interactions between the collagen fiber network and nonfibrillar matrix (NFM). Voronoi tessellations (representing collagen networks) were embedded in a continuous three-dimensional NFM. Fibers were represented as one-dimensional nonlinear springs and the NFM, meshed via tetrahedra, was modeled as a compressible neo-Hookean solid. Multidimensional finite element modeling was employed in order to couple the two tissue components and uniaxial tension was applied to the composite representative volume element (RVE). In terms of the overall RVE response (average stress, fiber orientation, and Poisson's ratio), the coupled fiber-matrix model yielded results consistent with those obtained using a previously developed parallel model based upon superposition. The detailed stress field in the composite RVE demonstrated the high degree of inhomogeneity in NFM mechanics, which cannot be addressed by a parallel model. Distributions of maximum/minimum principal stresses in the NFM showed a transition from fiber-dominated to matrix-dominated behavior as the matrix shear modulus increased. The matrix-dominated behavior also included a shift in the fiber kinematics toward the affine limit. We conclude that if only gross averaged parameters are of interest, parallel-type models are suitable. If, however, one is concerned with phenomena, such as individual cell-fiber interactions or tissue failure that could be altered by local variations in the stress field, then the detailed model is necessary in spite of its higher computational cost.

The Influence of Heat Treatment upon Fiber Pull-Out in a Ceramic Composite

1988 ◽  
Vol 120 ◽  
Author(s):  
M. D. Thouless ◽  
O. Sbaizero ◽  
E. Bischoff ◽  
E. Y. Luh
Keyword(s):  
Ceramic Composite ◽  
Ceramic Matrix Composites ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Shear Lag ◽  
Weibull Statistics ◽  
Pull Out ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

AbstractThe toughness of ceramic-matrix composites is strongly influenced by fiber pull-out. The extent of the pull-out depends upon the properties of the fiber and the fiber/matrix interface. Samples of a SiC/LAS composite were subjected to different heat treatments in order to systematically vary these properties. The predicted distribution of the fiber pull-out lengths was calculated by combining a shear lag analysis with Weibull statistics for the fiber strengths. Comparison of the analysis with experiments and microstructural observations contribute to an understanding of the role of the fiber/matrix interface upon the mechanical properties.

Comparison of 2-D Fiber Network Orientation Measurement Methods

2007 ◽  
Author(s):  
Edward A. Sander ◽  
Victor H. Barocas
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Orientation Measurement ◽  
Fiber Network ◽  
Satisfactory Description ◽  
Fibrin Gels ◽  
Multi Scale ◽  
Extracellular Matrix Components ◽  
Underlying Network

The mechanical properties of most soft tissues are dependent on the underlying network of collagen fibers, proteoglycans, and other extracellular matrix components [1]. Similarly, the properties of in vitro tissue analogs, often created from collagen or fibrin gels, are also dependent on the organization of the biopolymers within [2]. In both materials, the overall mechanical response is inherently multi-scale and dynamic. To understand the interplay between scales a satisfactory description of the microstructure must be obtained that is both tractable for modeling purposes and faithful to the essential physics of the tissue.

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