Simple Shear Testing of Parallel-Fibered Planar Soft Tissues

2000 ◽  
Vol 123 (2) ◽  
pp. 170-175 ◽  
Author(s):  
John C. Gardiner ◽  
Jeffrey A. Weiss
Keyword(s):  
Aspect Ratio ◽  
Simple Shear ◽  
Soft Tissues ◽  
Central Area ◽  
Fiber Material ◽  
Transversely Isotropic ◽  
Uniform Strain ◽  
Fiber Direction ◽  
Material Response ◽  
Test Configuration

The simple shear test may provide unique information regarding the material response of parallel-fibered soft tissues because it allows the elimination of the dominant fiber material response from the overall stresses. However, inhomogeneities in the strain field due to clamping and free edge effects have not been documented. The finite element method was used to study finite simple shear of simulated ligament material parallel to the fiber direction. The effects of aspect ratio, clamping prestrain, and bulk modulus were assessed using a transversely isotropic, hyperelastic material model. For certain geometries, there was a central area of uniform strain. An aspect ratio of 1:2 for the fiber to cross-fiber directions provided the largest region of uniform strain. The deformation was nearly isochoric for all bulk moduli indicating this test may be useful for isolating solid viscoelasticity from interstitial flow effects. Results suggest this test can be used to characterize the matrix properties for the type of materials examined in this study, and that planar measurements will suffice to characterize the strain. The test configuration may be useful for the study of matrix, fiber-matrix, and fiber-fiber material response in other types of parallel-fibered transversely isotropic soft tissues.

scholarly journals Stiffness Estimates for Composites with Elliptic Cylindrical Voids

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1354
Author(s):  
Fabian Becker ◽  
Christian Hopmann
Keyword(s):  
Composite Material ◽  
Aspect Ratio ◽  
Isotropic Material ◽  
Matrix Material ◽  
Transversely Isotropic ◽  
Fiber Direction ◽  
Infinite Length ◽  
Transversely Isotropic Material ◽  
Fiber Volume ◽  
Moderate Volume

A two-step homogenization procedure is presented to investigate the stiffness of a unidirectional continuous fiber-reinforced composite material containing voids of different shapes and volume contents. Since the Mori–Tanaka scheme is limited to moderate volume contents of the inhomogeneity phase, fiber and matrix are homogenized with semi-empirical relations with use of the adjusted fiber volume content in a first step. In the second step, the Mori–Tanaka scheme is applied to obtain the homogenized stiffness tensor of a transversely isotropic material containing voids aligned with the fiber direction. The voids are modelled with infinite length, but an elliptic base characterized by the aspect ratio. The tensor components of the Eshelby tensor for this case are presented in closed form for a transversely isotropic material depending on the aspect ratio and matrix material properties. The scheme is solved directly for easy implementation and the use of fast calculations of the effective engineering constants of a composite material containing voids. Experimental results from literature for different void contents and shapes are compared to the predicted moduli with cylindrical voids. From the results it is further concluded that the aspect ratio of the void and the manufacturing process of the composite should be considered.

A NUMERICAL STUDY ON A TRANSVERSELY ISOTROPIC PERMEABILITY MODEL APPLIED TO SOFT TISSUES

2021 ◽  
Author(s):  
Thayller Weverton Barp ◽  
Bruno Klahr ◽  
Thiago André Carniel ◽  
Eduardo Fancello
Keyword(s):  
Soft Tissues ◽  
Numerical Study ◽  
Transversely Isotropic ◽  
Permeability Model

PREDICTING PROCESSING INDUCED RESIDUAL- STRESSES IN CARBON FIBER-THERMOPLASTIC MICRO-COMPOSITES

2021 ◽  
Author(s):  
NITHIN K. PARAMBIL ◽  
BRANNDON R. CHEN ◽  
JOSEPH M. DEITZEL ◽  
JOHN W. GILLESPIE, JR. ◽  
LOAN T. VO ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Residual Strain ◽  
Coefficient Of Thermal Expansion ◽  
Fiber Composite ◽  
Transversely Isotropic ◽  
Axial Direction ◽  
Single Fiber ◽  
Temperature Dependent ◽  
Test Configuration ◽  
Polypropylene Composites

A computational model of residual stress is developed for AS4/polypropylene composites and implemented via user material subroutine (UMAT) in ABAQUS. The main factors included in the model are the cooling-rate dependent crystallinity, temperature-dependent elastic modulus, and temperature-dependent coefficient of thermal expansion (CTE) of the matrix, and the temperature-independent transversely isotropic properties of the carbon fiber. Numerical results are generated for the case of a single fiber embedded in a thin film of polypropylene sample to replicate the process history and test configuration. During single fiber composite processing, a precalculated weight (tensile preload) is applied at the fiber ends to eliminate buckling/waviness of the carbon fiber induced by matrix shrinkage in the axial direction of the fiber. Experiments and Finite element (FE) analysis have been conducted with different preloads (1g, 4g, and 8g) at 25°C. Micro-Raman spectroscopy is utilized to validate the residual strain with different preloads at the bulk. The measured strain values show a good correlation with the predicted residual strain for various preload conditions.

scholarly journals Applying ASTM Standards to Tensile Tests of Musculoskeletal Soft Tissue: Methods to Reduce Grip Failures and Promote Reproducibility

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Madison E. Wale ◽  
Derek Q. Nesbitt ◽  
Bradley S. Henderson ◽  
Clare K. Fitzpatrick ◽  
Jaremy J. Creechley ◽  
...  
Keyword(s):  
Tensile Testing ◽  
Soft Tissues ◽  
Tensile Tests ◽  
Standard Test ◽  
International Standards ◽  
Fiber Reinforced Composites ◽  
Fiber Direction ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Test Standards

Abstract Tensile testing is an essential experiment to assess the mechanical integrity of musculoskeletal soft tissues, yet standard test methods have not been developed to ensure the quality and reproducibility of these experiments. The ASTM International standards organization has created tensile test standards for common industry materials that specify geometric dimensions of test specimens (coupons) that promote valid failures within the gage section (midsubstance), away from the grips. This study examined whether ASTM test standards for plastics, elastomers, and fiber-reinforced composites are suitable for tensile testing of bovine meniscus along the circumferential fiber direction. We found that dumbbell (DB) shaped coupons based on ASTM standards for elastomers and plastics had an 80% and 60% rate of midsubstance failures, respectively. The rate of midsubstance failures dropped to 20% when using straight (ST) coupons based on ASTM standards for fiber-reinforced composites. The mechanical properties of dumbbell shaped coupons were also significantly greater than straight coupons. Finite element models of the test coupons revealed stress distributions that supported our experimental findings. In addition, we found that a commercial deli-slicer was able to slice meniscus to uniform layer thicknesses that were within ASTM dimensional tolerances. This study provides methods, recommendations, and insights that can advance the standardization of tensile testing in meniscus and other soft fibrous tissues.

Stable equilibrium configurations of an oblate capsule in simple shear flow

2016 ◽  
Vol 791 ◽  
pp. 738-757 ◽  
Author(s):  
C. Dupont ◽  
F. Delahaye ◽  
D. Barthès-Biesel ◽  
A.-V. Salsac
Keyword(s):  
Aspect Ratio ◽  
Shear Flow ◽  
Simple Shear ◽  
Capillary Number ◽  
Stable Equilibrium ◽  
Viscosity Ratio ◽  
Shear Plane ◽  
Initial Orientation ◽  
Simple Shear Flow ◽  
Mechanical Equilibrium

The objective of the paper is to determine the stable mechanical equilibrium states of an oblate capsule subjected to a simple shear flow, by positioning its revolution axis initially off the shear plane. We consider an oblate capsule with a strain-hardening membrane and investigate the influence of the initial orientation, capsule aspect ratio$a/b$, viscosity ratio${\it\lambda}$between the internal and external fluids and the capillary number$Ca$which compares the viscous to the elastic forces. A numerical model coupling the finite element and boundary integral methods is used to solve the three-dimensional fluid–structure interaction problem. For any initial orientation, the capsule converges towards the same mechanical equilibrium state, which is only a function of the capillary number and viscosity ratio. For$a/b=0.5$, only four regimes are stable when${\it\lambda}=1$: tumbling and swinging in the low and medium$Ca$range ($Ca\lesssim 1$), regimes for which the capsule revolution axis is contained within the shear plane; then wobbling during which the capsule experiences precession around the vorticity axis; and finally rolling along the vorticity axis at high capillary numbers. When${\it\lambda}$is increased, the tumbling-to-swinging transition occurs for higher$Ca$; the wobbling regime takes place at lower$Ca$values and within a narrower$Ca$range. For${\it\lambda}\gtrsim 3$, the swinging regime completely disappears, which indicates that the stable equilibrium states are mainly the tumbling and rolling regimes at higher viscosity ratios. We finally show that the$Ca$–${\it\lambda}$phase diagram is qualitatively similar for higher aspect ratio. Only the$Ca$-range over which wobbling is stable increases with$a/b$, restricting the stability ranges of in- and out-of-plane motions, although this phenomenon is mainly visible for viscosity ratios larger than 1.

Case of focal dystrophic calcification in the peritarsal soft tissues of a horse

2019 ◽  
Vol 7 (3) ◽  
pp. e000808
Author(s):  
Michael Joseph De Cozar ◽  
Elizabeth Barr
Keyword(s):  
Connective Tissue ◽  
Soft Tissues ◽  
Flexor Tendon ◽  
Distal Tibia ◽  
Central Area ◽  
Dystrophic Calcification ◽  
En Bloc ◽  
Old Irish ◽  
And Cartilage ◽  
Firm Mass

A 12-year-old Irish sports horse gelding presented with a recently developed oval firm mass at the plantaromedial aspect of right tarsus, located between the gastrocnemius and deep digital flexor tendon. At presentation, the horse was mildly right hind lame, with no exacerbation with flexion. Radiography and ultrasonography revealed an ovoid mineralised mass within soft tissues plantaromedially to tarsus and distal tibia and not associated with tarsal sheath or calcaneal bursa. Due to mild intermittent lameness and concerns regarding possibility for further increase in size, the horse underwent en bloc removal of the calcified mass under general anaesthesia. Histopathology showed the mass contained fibrous reactive connective tissue, undergoing bone and cartilage metaplasia and degeneration, with a central area of calcified bone and surrounding region of mononuclear inflammation. These characteristics although reminiscent of calcinosis circumscripta were diagnosed as focal dystrophic calcification. The horse made a full recovery and returned to a normal exercise level.

Anisotropic Behavior of White Matter in Shear and Implications for Transversely Isotropic Models

2013 ◽  
Author(s):  
Ruth J. Okamoto ◽  
Yuan Feng ◽  
Guy M. Genin ◽  
Philip V. Bayly
Keyword(s):  
White Matter ◽  
Strain Tensor ◽  
Experimental Studies ◽  
Transversely Isotropic ◽  
Stretch Ratio ◽  
Fiber Axis ◽  
Fiber Direction ◽  
Material Models ◽  
Green Strain ◽  
The Brain

Experimental studies [1] have shown that white matter (WM) in the brain is mechanically anisotropic. Based on its fibrous structure, transversely isotropic (TI) material models have been suggested to capture WM behavior. TI hyperelastic material models involve strain energy density functions that depend on the I4 and I5 pseudo-invariants of the Cauchy-Green strain tensor to account for the effects of stiff fibers. The pseudo-invariant I4 is the square of the stretch ratio in the fiber direction; I5 contains contributions of shear strain in planes parallel to the fiber axis. Most, if not all, published models of WM depend on I4 but not on I5.

Lightning Injury of the Tympanic Membrane

1993 ◽  
Vol 102 (11) ◽  
pp. 867-869 ◽  
Author(s):  
Miriam I. Redleaf ◽  
Brian F. McCabe
Keyword(s):  
Tympanic Membrane ◽  
Blood Vessels ◽  
External Auditory Canal ◽  
Soft Tissues ◽  
Central Area ◽  
Mechanism Of Injury ◽  
Review Of The Literature ◽  
Lightning Strikes ◽  
Lightning Injury

A number of cases of otologic injuries by lightning strikes have been described in the otolaryngological literature. The mechanism of these injuries remains uncertain. We report 3 cases of lightning injury that presented to us. Analysis of these cases suggests that the mechanism of injury is direct conduction of electricity from the scalp to the soft tissues of the external auditory canal to the tympanic membrane. The conduits of the electrical surge are the subcutaneous blood vessels, smaller vessels being damaged more than larger vessels. Since the tympanic membrane central vessels are smaller than the canal vessels, the central area of the tympanic membrane would be most vulnerable, and this is seen clinically. A review of the literature supports this proposed mechanism of injury.

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