scholarly journals A Novel Method for Repeatable Failure Testing of Annulus Fibrosus

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Benjamin Werbner ◽  
Minhao Zhou ◽  
Grace O'Connell
Keyword(s):  
Mechanical Properties ◽  
Annulus Fibrosus ◽  
Mechanical Test ◽  
Local Strain ◽  
Intervertebral Disk ◽  
Failure Behavior ◽  
Fiber Reinforced ◽  
Failure Mechanics ◽  
Dog Bone ◽  
Failure Properties

Tears in the annulus fibrosus (AF) of the intervertebral disk can result in disk herniation and progressive degeneration. Understanding AF failure mechanics is important as research moves toward developing biological repair strategies for herniated disks. Unfortunately, failure mechanics of fiber-reinforced tissues, particularly tissues with fibers oriented off-axis from the applied load, is not well understood, partly due to the high variability in reported mechanical properties and a lack of standard techniques ensuring repeatable failure behavior. Therefore, the objective of this study was to investigate the effectiveness of midlength (ML) notch geometries in producing repeatable and consistent tissue failure within the gauge region of AF mechanical test specimens. Finite element models (FEMs) representing several notch geometries were created to predict the location of bulk tissue failure using a local strain-based criterion. FEM results were validated by experimentally testing a subset of the modeled specimen geometries. Mechanical testing data agreed with model predictions (∼90% agreement), validating the model's predictive power. Two of the modified dog-bone geometries (“half” and “quarter”) effectively ensured tissue failure at the ML for specimens oriented along the circumferential-radial and circumferential-axial directions. The variance of measured mechanical properties was significantly lower for notched samples that failed at the ML, suggesting that ML notch geometries result in more consistent and reliable data. In addition, the approach developed in this study provides a framework for evaluating failure properties of other fiber-reinforced tissues, such as tendons and meniscus.

A Comparison of Uniaxial and Biaxial Mechanical Properties of the Annulus Fibrosus: A Porcine Model

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Diane E. Gregory ◽  
Jack P. Callaghan
Keyword(s):  
Mechanical Properties ◽  
Annulus Fibrosus ◽  
Axial Direction ◽  
Stretch Ratio ◽  
Intervertebral Disk ◽  
Circumferential Direction ◽  
Biaxial Tests ◽  
Maximal Stress ◽  
Biaxial Mechanical Properties

The annulus fibrosus of the intervertebral disk experiences multidirectional tension in vivo, yet the majority of mechanical property testing has been uniaxial. Therefore, our understanding of how this complex multilayered tissue responds to loading may be deficient. This study aimed to determine the mechanical properties of porcine annular samples under uniaxial and biaxial tensile loading. Two-layer annulus samples were isolated from porcine disks from four locations: anterior superficial, anterior deep, posterior superficial, and posterior deep. These tissues were then subjected to three deformation conditions each to a maximal stretch ratio of 1.23: uniaxial, constrained uniaxial, and biaxial. Uniaxial deformation was applied in the circumferential direction, while biaxial deformation was applied simultaneously in the circumferential and compressive directions. Constrained uniaxial consisted of a stretch ratio of 1.23 in the circumferential direction while holding the tissue stationary in the axial direction. The maximal stress and stress-stretch ratio (S-S) moduli determined from the biaxial tests were significantly higher than those observed during both the uniaxial tests (maximal stress, 97.1% higher during biaxial; p=0.002; S-S moduli, 117.9% higher during biaxial; p=0.0004) and the constrained uniaxial tests (maximal stress, 46.8% higher during biaxial; S-S moduli, 82.9% higher during biaxial). These findings suggest that the annulus is subjected to higher stresses in vivo when under multidirectional tension.

scholarly journals The Impact of Draping Effects on the Stiffness and Failure Behavior of Unidirectional Non-Crimp Fabric Fiber Reinforced Composites

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2959
Author(s):  
Eckart Kunze ◽  
Siegfried Galkin ◽  
Robert Böhm ◽  
Maik Gude ◽  
Luise Kärger
Keyword(s):  
Mechanical Properties ◽  
Experimental Results ◽  
Analytical Models ◽  
Failure Behavior ◽  
Fiber Reinforced ◽  
Fiber Volume ◽  
Fiber Waviness ◽  
Reinforced Plastics ◽  
The Impact ◽  
Local Fiber

Unidirectional non-crimp fabrics (UD-NCF) are often used to exploit the lightweight potential of continuous fiber reinforced plastics (CoFRP). During the draping process, the UD-NCF fabric can undergo large deformations that alter the local fiber orientation, the local fiber volume content (FVC) and create local fiber waviness. Especially the FVC is affected and has a large impact on the mechanical properties. This impact, resulting from different deformation modes during draping, is in general not considered in composite design processes. To analyze the impact of different draping effects on the mechanical properties and the failure behavior of UD-NCF composites, experimental results of reference laminates are compared to the results of laminates with specifically induced draping effects, such as non-constant FVC and fiber waviness. Furthermore, an analytical model to predict the failure strengths of UD laminates with in-plane waviness is introduced. The resulting stiffness and strength values for different FVC or amplitude to wavelength configurations are presented and discussed. In addition, failure envelopes based on the PUCK failure criterion for each draping effect are derived, which show a clear specific impact on the mechanical properties. The findings suggest that each draping effect leads to a “new fabric” type. Additionally, analytical models are introduced and the experimental results are compared to the predictions. Results indicate that the models provide reliable predictions for each draping effect. Recommendations regarding necessary tests to consider each draping effect are presented. As a further prospect the resulting stiffness and strength values for each draping effect can be used for a more accurate prediction of the structural performance of CoFRP parts.

Mitigations of machine-damaged free-edge effects on fiber-reinforced composites

2020 ◽  
pp. 002199832096798
Author(s):  
Kevin A Brauning ◽  
Arifa Kunza ◽  
Ibrahim M Alarifi ◽  
Ramazan Asmatulu
Keyword(s):  
Mechanical Properties ◽  
Edge Effects ◽  
Mechanical Test ◽  
Free Edge ◽  
Primary Objective ◽  
Manufacturing Industries ◽  
Fiber Reinforced Composites ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Vacuum Oven

The carbon fiber-reinforced composites were prepared in a vacuum oven using pre-preg composites, and the edge surfaces of the composite coupons were treated using high performing adhesives to eliminate the free-edge effects. The primary objective of the study was to usefully address the free-edge effects of composites used in aircraft and other manufacturing industries. The mechanical test results conducted on the untreated and edge-treated test coupons showed that the edge treatment and fiber orientations significantly affected the tensile strength and quality of the composites. It is determined that applying adhesives on the edges of the coupons could improve the mechanical properties of the composites, about 11%. Successful testing and evaluation of materials can lead to the precise analysis of a structure, and predictable behavior of the end design. This study may open up new possibilities to enhance the overall mechanical properties of fiber-reinforced composites for various manufacturing industries.

Dielectric and Mechanical Properties of Unidirectional SiC Fiber-Reinforced Aluminum Phosphates Composite

2007 ◽  
Vol 336-338 ◽  
pp. 1266-1269
Author(s):  
Xin Peng Wang ◽  
Shi Tian
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Dielectric Constant ◽  
Dissipation Factor ◽  
Failure Behavior ◽  
Fiber Reinforced ◽  
Sic Fiber ◽  
Aluminum Phosphates ◽  
Dielectric Dissipation Factor ◽  
Dielectric And Mechanical Properties

In this paper, the unidirectional SiC fiber-reinforced aluminum phosphates composites, in which the SiC fibers were heat-treated at different temperature, time and in different method, were prepared. The dielectric and mechanical properties of the composites were studied. The influences of heat treatment of SiC fiber on the properties of the SiC fiber-reinforced aluminum phosphates composite were investigated in detail. The flexural strength, relative dielectric constant and dielectric dissipation factor of the composite were measured. And the microstructure of the composite was characterized by SEM (scanning electronic microscope). The results show that heat treatment of SiC fiber has a great influence on mechanical and dielectric properties of the composite. The heat treatment decreases the dielectric constant and dielectric dissipation factor of the composite enormously. But at the same time, the heat treatment of the SiC fiber makes an unfavorably strongly bonded SiC fiber/aluminum phosphates matrix interface, which decreases the strength of the composite extraordinarily. And the composite displays a completely brittle failure behavior without fiber debonding and pulling out, which is detected by SEM.

Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

1989 ◽  
Vol 47 ◽  
pp. 556-557
Author(s):  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Frictional Stress ◽  
Fiber Reinforced ◽  
Pull Out ◽  
Carbon Coated ◽  
Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

Effect of combined drink cans and steel fibers on the impact resistance and mechanical properties of concrete

2020 ◽  
Vol 14 (2) ◽  
pp. 6734-6742
Author(s):  
A. Syamsir ◽  
S. M. Mubin ◽  
N. M. Nor ◽  
V. Anggraini ◽  
S. Nagappan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Impact Resistance ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Fiber Reinforced ◽  
Indirect Tensile ◽  
The Impact

This study investigated the combine effect of 0.2 % drink cans and steel fibers with volume fractions of 0%, 0.5%, 1%, 1.5%, 2%, 2.5% and 3% to the mechanical properties and impact resistance of concrete. Hooked-end steel fiber with 30 mm and 0.75 mm length and diameter, respectively was selected for this study.  The drinks cans fiber were twisted manually in order to increase friction between fiber and concrete. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the strength performance of concrete, especially the compressive strength, flexural strength and indirect tensile strength. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the compressive strength, flexural strength and indirect tensile strength by 2.3, 7, and 2 times as compare to batch 1, respectively. Moreover, the impact resistance of fiber reinforced concrete has increase by 7 times as compared to non-fiber concretes. Moreover, the impact resistance of fiber reinforced concrete consistently gave better results as compared to non-fiber concretes. The fiber reinforced concrete turned more ductile as the dosage of fibers was increased and ductility started to decrease slightly after optimum fiber dosage was reached. It was found that concrete with combination of 2% steel and 0.2% drink cans fibers showed the highest compressive, split tensile, flexural as well as impact strength.    

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