scholarly journals A Recruitment Model of Tendon Viscoelasticity That Incorporates Fibril Creep and Explains Strain-Dependent Relaxation

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Tom Shearer ◽  
William J. Parnell ◽  
Barbara Lynch ◽  
Hazel R. C. Screen ◽  
I. David Abrahams
Keyword(s):  
Soft Tissues ◽  
Length Distribution ◽  
Viscoelastic Behavior ◽  
Mechanical Tests ◽  
The Matrix ◽  
Tail Tendon ◽  
Fibril Length ◽  
Changes Over Time ◽  
Constitutive Parameters ◽  
Strain Dependent

Abstract Soft tissues exhibit complex viscoelastic behavior, including strain-rate dependence, hysteresis, and strain-dependent relaxation. In this paper, a model for soft tissue viscoelasticity is developed that captures all of these features and is based upon collagen recruitment, whereby fibrils contribute to tissue stiffness only when taut. We build upon existing recruitment models by additionally accounting for fibril creep and by explicitly modeling the contribution of the matrix to the overall tissue viscoelasticity. The fibrils and matrix are modeled as linear viscoelastic and each fibril has an associated critical strain (corresponding to its length) at which it becomes taut. The model is used to fit relaxation tests on three rat tail tendon fascicles and predict their response to cyclic loading. It is shown that all of these mechanical tests can be reproduced accurately with a single set of constitutive parameters, the only difference between each fascicle being the distribution of their fibril crimp lengths. By accounting for fibril creep, we are able to predict how the fibril length distribution of a fascicle changes over time under a given deformation. Furthermore, the phenomenon of strain-dependent relaxation is explained as arising from the competition between the fibril and matrix relaxation functions.

The Influence of Ultrasonic Energy on Chemical Treatment of Surface Properties and the Properties of Composites Made of Luffa Cylindrical Fiber-Polyester Resin

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
E. Dilara Koçak
Keyword(s):  
Composite Structure ◽  
Polyester Resin ◽  
Unsaturated Polyester ◽  
Natural Fibers ◽  
Morphological Characteristics ◽  
Mechanical Tests ◽  
Cylindrical Fiber ◽  
The Matrix ◽  
Mechanical Performances ◽  
Properties Of Composites

Producing composites from natural fibers is known to be common. These fibers benefit from their mechanical performances, low density, and their biodegradability. However, it is necessary for the fibers to form adhesion in the matrix. Therefore, it is necessary to apply a chemical process to the surface of the fibers. In this study, four different processes in conventional and ultrasonic energies were applied on luffa cylindrical fibers. At the end of the application, a composite structure was formed on the fibers that were obtained by using unsaturated polyester resin. The changes in the characteristics of the composite structure were recorded by mechanical tests, Fourier transform infrared, X-ray diffractometer, and their morphological characteristics by means of scanning electron microscopy. Considering all the results, formic acid and acetic acid process results were found to adequately modify the fiber surfaces.

scholarly journals Research and Modeling of Viscoelastic Behavior of Elastomeric Nanocomposites

2021 ◽  
pp. 76-87
Author(s):  
V. D Kislitsyn ◽  
K. A Mokhireva ◽  
V. V Shadrin ◽  
A. L Svistkov
Keyword(s):  
Constitutive Relations ◽  
Viscoelastic Behavior ◽  
Polymer Materials ◽  
Material Structure ◽  
Softening Effect ◽  
Single Walled Nanotubes ◽  
Wide Range ◽  
Significant Difference ◽  
The Matrix ◽  
Entire History

The paper presents results of studying mechanical properties of polymer composites depending on types of filler particles (granular - carbon black, nanodiamonds; layered - graphene plates; fibrous - single-walled nanotubes). These nanofillers differ greatly from each other in their structure and geometry. A significant difference in behavior of nanocomposites was revealed even with little introduction of particles into the elastomer. The highest level of reinforcement of the matrix was obtained when single-wall nanotubes and detonation nanodiamonds were used as fillers. The viscoelastic properties and the Mullins softening effect [1-4] were investigated in experiments performed with material samples subjected to complex uniaxial cyclic deformation. In these experiments, the amplitude of deformations was changed step by step; and at each step a time delay was specified to complete rearrangement processes of the material structure. It was found that a pronounced softening effect after the first cycle of deformation and significant hysteresis losses occur in the material filled with single-walled nanotubes. These characteristics are insignificant for the rest of nanocomposites until elongation increases twofold. In accordance with the obtained results, a new version of the mathematical model to describe properties of the viscoelastic polymer materials was proposed. The constants of the constitutive relations were calculated for each material; the theoretical and experimental load curves were compared. As a result, the introduced model is able to describe the behavior of elastomeric nanocomposites with a high accuracy. Moreover, this model is relatively easy to use, suitable for a wide range of strain rates and stretch ratios and does not require the entire history of deformation as needed for integral models of viscoelasticity.

Mullite Whisker Reinforced Zirconia Toughened Alumina for High Temperature Applications

2014 ◽  
Author(s):  
Taylor Robertson ◽  
Xiao Huang ◽  
Richard Kearsey
Keyword(s):  
High Temperature ◽  
Cost Effective ◽  
Mechanical Tests ◽  
Processing Route ◽  
Molten Salt Method ◽  
The Matrix ◽  
Mullite Whiskers ◽  
Monolithic Ceramics ◽  
Zirconia Toughened Alumina ◽  
Temperature Applications

Particulate enhanced oxide ceramics are an attractive class of materials for high temperature applications because they possess many of the high temperature capabilities of monolithic ceramics but also have enhanced mechanical properties due to their multi-phase structure. High temperature structural ceramics have the potential to operate above at higher temperatures than current super alloys; however, processing costs and lack of reliability has prevented their commercialization. In this work a particulate reinforced ceramic composed entirely of oxides is proposed as a more oxidation resistant and cost effective structural ceramic which will have potentially improved resistance to environmental degradation. Zirconia Toughened Alumina (ZTA), as the matrix, has enhanced toughness, strength, and creep resistance over single phase alumina or zirconia. ZTA can further be strengthened by the incorporation of SiC type whiskers; however, these whiskers are prone to deterioration at temperatures above 1000°C through oxidation. In this work Mullite, in whisker form, is proposed as the reinforcement to ZTA due to its stability in oxidizing atmospheres at high temperatures. Mullite whiskers are grown through the molten salt method and incorporated into the ZTA matrix using a colloidal processing route in this study. The composition of the ZTA matrix is 15wt% Yttria stabilized Zirconia (YSZ), 85 wt% α-Alumina. The Mullite whiskers make up 20 vol% of the composite, yielding a final composition of 71.6 wt% Alumina, 12.7 wt% YSZ, and 15.6 wt% Mullite. The green compacts are fired in a two stage sintering process incorporating atmospheric pressure sintering to 92% density (seal the pore channels) and then hot isostatic pressure pressing (HIP) to increase the density. Samples have been tested for room temperature flexural strength using a three point bend test and fracture toughness through Gong’s Vickers indentation method. The results of microstructure study and mechanical tests are reported in this paper.

scholarly journals A damage model for collagen fibres with an application to collagenous soft tissues

2020 ◽  
Vol 476 (2236) ◽  
pp. 20190821
Author(s):  
Gerhard A. Holzapfel ◽  
Ray W. Ogden
Keyword(s):  
Soft Tissues ◽  
Damage Model ◽  
Three Dimensional ◽  
Collagen Fibres ◽  
Physiological Loading ◽  
Cross Links ◽  
Complex Boundary ◽  
Tail Tendon ◽  
Similar Basis ◽  
Rat Tail

We propose a mechanical model to account for progressive damage in collagen fibres within fibrous soft tissues. The model has a similar basis to the pseudoelastic model that describes the Mullins effect in rubber but it also accounts for the effect of cross-links between collagen fibres. We show that the model is able to capture experimental data obtained from rat tail tendon fibres, and the combined effect of damage and collagen cross-links is illustrated for a simple shear test. The proposed three-dimensional framework allows a straightforward implementation in finite-element codes, which are needed to analyse more complex boundary-value problems for soft tissues under supra-physiological loading or tissues weakened by disease.

scholarly journals Dynamic Characterization of the Biomechanical Behaviour of Bovine Ovarian Cortical Tissue and Its Short-Term Effect on Ovarian Tissue and Follicles

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3759
Author(s):  
Giulia Pascoletti ◽  
Maddalena Di Nardo ◽  
Gionata Fragomeni ◽  
Vincenza Barbato ◽  
Teresa Capriglione ◽  
...  
Keyword(s):  
Mechanical Test ◽  
Cell Damage ◽  
Ovarian Tissue ◽  
Viscoelastic Behavior ◽  
Mechanical Tests ◽  
Cortical Tissue ◽  
Short Term ◽  
Tissue Properties

The ovary is a dynamic mechanoresponsive organ. In vitro, tissue biomechanics was reported to affect follicle activation mainly through the Hippo pathway. Only recently, ovary responsiveness to mechanical signals was exploited for reproductive purposes. Unfortunately, poor characterization of ovarian cortex biomechanics and of the mechanical challenge hampers reproducible and effective treatments, and prevention of tissue damages. In this study the biomechanical response of ovarian cortical tissue from abattoir bovines was characterized for the first time. Ovarian cortical tissue fragments were subjected to uniaxial dynamic testing at frequencies up to 30 Hz, and at increasing average stresses. Tissue structure prior to and after testing was characterized by histology, with established fixation and staining protocols, to assess follicle quality and stage. Tissue properties largely varied with the donor. Bovine ovarian cortical tissue consistently exhibited a nonlinear viscoelastic behavior, with dominant elastic characteristics, in the low range of other reproductive tissues, and significant creep. Strain rate was independent of the applied stress. Histological analysis prior to and after mechanical tests showed that the short-term dynamic mechanical test used for the study did not cause significant tissue tear, nor follicle expulsion or cell damage.

Prediction of the Fiber-Matrix Interface Failure due to Longitudinal Tensile Loading Using Finite Element Methods

1994 ◽  
Vol 365 ◽  
Author(s):  
Hassan Mahfuz ◽  
A.K.M. Ahsan Mian ◽  
Uday K. Vaidya ◽  
Timothy Brown ◽  
Shaik Jeelani
Keyword(s):  
Local Stress ◽  
Tensile Loading ◽  
Mechanical Tests ◽  
Matrix Interface ◽  
Interface Failure ◽  
Strain Behavior ◽  
The Matrix ◽  
Fiber Matrix Interface ◽  
Fiber Matrix ◽  
Composite Response

ABSTRACTA 3D-unit cell for 0/90 laminated composites has been developed to predict the composite behavior under longitudinal tensile loading condition. 3D contact element has been used to model the fiber matrix interface. Two interface conditions, namely, infinitely strong and weakly bonded, are considered in the analysis. Both large displacement and plastic strain behavior for the matrix are considered to account for the geometric and material non-linearities. Investigations were carried out at three temperatures to compare the composite response obtained from mechanical tests at those temperatures. Stress-strain behavior and the local stress distributions at the fiber as well as at the matrix are presented, and their effects on the failure of the interface are discussed in the paper. The material under investigation was SiCf/Si3N4.

A retrofit for asbestos-based brake pad employing palm kernel fiber as the base filler material

2018 ◽  
Vol 233 (9) ◽  
pp. 1906-1913 ◽  
Author(s):  
CH Achebe ◽  
JL Chukwuneke ◽  
FA Anene ◽  
CM Ewulonu
Keyword(s):  
Specific Gravity ◽  
Palm Kernel ◽  
Friction Material ◽  
Mechanical Tests ◽  
Filler Material ◽  
Oil Absorption ◽  
Brake Pad ◽  
Brake Pads ◽  
The Matrix ◽  
Automotive Brake

The development of automobile brake pad using locally sourced palm kernel fiber was carried out. Asbestos, a carcinogenic material, has been used for decades as a friction material. This development has thus prompted a couple of research efforts geared towards its replacement for brake pad manufacture. Palm kernel fiber was used as an alternative filler material in conjunction with various quantities of epoxy resin as the matrix. Three sets of compositions were made, and the resulting specimens subjected to physical and mechanical tests using standard materials, procedures, and equipment. The essence is to determine their suitability and hence possible performance in service. The result showed that sample C with 40% palm kernel fiber content having hardness, compressive strength, abrasion resistance, specific gravity, water absorption, and oil absorption of 178 MPa, 96.2 MPa, 1.67 mg/m, 1.8 g/cm3, 1.86%, and 0.89%, respectively, had an optimum performance rating. It was equally ascertained that increase in the filler content had the effect of increase in hardness, wear resistance, and specific gravity of the composite brake pad, while water and oil absorption got decreased when compared with results obtained by other researchers using conventional brake pads made of other friction materials including asbestos. This is an indicator that palm kernel fiber is a possible and effective retrofit for asbestos as a filler material in automotive brake pad manufacture.

Implementation of Finite Deformation Triphasic Modeling in the Finite Element Code FEBio

2012 ◽  
Author(s):  
Gerard A. Ateshian ◽  
Steve Maas ◽  
Jeffrey A. Weiss
Keyword(s):  
Soft Tissues ◽  
Mixture Theory ◽  
Solid Matrix ◽  
Osmotic Swelling ◽  
Solute Content ◽  
Counter Ions ◽  
The Matrix ◽  
Triphasic Theory ◽  
Ion Species ◽  
And Diffusion

Many biological soft tissues exhibit a charged solid matrix, most often due to the presence of proteoglycans enmeshed within the matrix. The predominant solute content of the interstitial fluid of these tissues consists of the monovalent counter-ions Na+ and Cl−. The electrical interactions between the mobile ion species and fixed charge density of the solid matrix produces an array of mechano-electrochemical effects, including Donnan osmotic swelling, and streaming and diffusion potentials and currents. These phenomena have been successfully modeled by the triphasic theory of Lai et al. [1], which is based on the framework of mixture theory [2]. Other similar frameworks have also been proposed [3, 4]. The equations of triphasic theory are nonlinear, even in the range of infinitesimal strains. Therefore, numerical schemes are generally needed to solve all but the simplest problems using this framework.

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