scholarly journals Modeling Fatigue Damage in Chemically Treated Soft Tissues

2000 ◽  
Author(s):  
William S. Slaughter ◽  
Michael S. Sacks
Keyword(s):  
Mechanical Properties ◽  
Fatigue Damage ◽  
Chemical Treatment ◽  
Damage Mechanics ◽  
Collagen Fiber ◽  
Soft Tissues ◽  
Cardiac Valve ◽  
Chemically Treated ◽  
Treatment Technologies ◽  
The Impact

Abstract Chemically treated, biologically derived tissues are used extensively in cardiac valve bioprostheses. Unfortunately, while extensive research has focused on chemical treatment technologies to reduce negative in-vivo effects such as mineralization and to enhance overall biocompatibility, little work has been done on understanding the effects of fatigue on tissue mechanical properties. In the current work, a structure-based damage mechanics model for the evolution of mechanical properties with cyclic loading of chemically treated soft tissues is presented. The model is used to clarify and relate the impact of different structural changes, such as collagen fiber debonding and collagen fiber weakening, to changes in macro-level tissue mechanical properties. The fatigue damage model will ultimately serve as a guide for the development of key experiments for fatigue damage assessment of novel chemical treatment technologies. This will aid in the rational development, as opposed to the current ad-hoc approach, of novel chemically modified collagenous biomaterials for more durable cardiac valve bioprostheses.

A Structural Constitutive Model for Chemically Treated Soft Tissues

1999 ◽  
Author(s):  
Michael S. Sacks
Keyword(s):  
Constitutive Model ◽  
Chemical Treatment ◽  
Soft Tissues ◽  
Current Approach ◽  
Orientation Data ◽  
Chemically Treated ◽  
Treatment Technologies ◽  
Small Angle Light Scattering ◽  
In Vivo Effects

Abstract Chemically treated biologically derived tissues are used extensively in bioprostheses. Unfortunately, while extensive research has focused on chemical treatment technologies to reduce negative in-vivo effects such as mineralization and to enhance overall biocompatiblity, little work has been done on understanding the effects of chemical treatment on tissue mechanical properties. In the current work, a structural constitutive model for chemically treated tissues is presented that seeks to separate out the effects of the chemically treated matrix from that of the collagen fibers. Experimental results from Sacks and Chuong (Sacks and Chuong 1998) using glutaraldehyde bovine pericardium (GLBP) are used to demonstrate the approach. A unique feature of the current approach is the integration of collagen fiber orientation data quantified by small angle light scattering (SALS).

Modeling Fatigue Damage in Chemically Treated Soft Tissues

2001 ◽  
Vol 198-199 ◽  
pp. 255-260 ◽  
Author(s):  
William S. Slaughter ◽  
Michael S. Sacks
Keyword(s):  
Fatigue Damage ◽  
Soft Tissues ◽  
Chemically Treated

scholarly journals Application of Ultrasound on Monitoring the Evolution of the Collagen Fiber Reinforced nHAC/CS CompositesIn Vivo

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Yan Chen ◽  
Yuting Yan ◽  
Xiaoming Li ◽  
He Li ◽  
Huiting Tan ◽  
...  
Keyword(s):  
Collagen Fiber ◽  
Soft Tissues ◽  
Degradation Process ◽  
Ultrasound Images ◽  
Fiber Reinforced ◽  
Bone Mesenchymal Stem Cells ◽  
Feasible Alternative ◽  
The Impact

To date, fiber reinforce scaffolds have been largely applied to repair hard and soft tissues. Meanwhile, monitoring the scaffolds for long periodsin vivois recognized as a crucial issue before its wide use. As a consequence, there is a growing need for noninvasive and convenient methods to analyze the implantation remolding processin situand in real time. In this paper, diagnostic medical ultrasound was used to monitor thein vivobone formation and degradation process of the novel mineralized collagen fiber reinforced composite which is synthesized by chitosan (CS), nanohydroxyapatite (nHA), and collagen fiber (Col). To observe the impact of cells on bone remodeling process, the scaffolds were planted into the back of the SD rats with and without rat bone mesenchymal stem cells (rBMSCs). Systematic data of scaffoldsin vivowas extracted from ultrasound images. Significant consistency between the data from the ultrasound and DXA could be observedP<0.05. This indicated that ultrasound may serve as a feasible alternative for noninvasive monitoring the evolution of scaffoldsin situduring cell growth.

Variation in Mechanical Properties, Microstructures and Fracture Behavior of 304 Stainless Steel During Low-Cycle Fatigue

2010 ◽  
Author(s):  
Duyi Ye ◽  
Yuandong Xu ◽  
Lei Xiao ◽  
Haibo Cha
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Strain Hardening ◽  
Fatigue Damage ◽  
Fracture Behavior ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Damage Process ◽  
Static Mechanical

A series of experiments, including constant amplitude low-cycle fatigue tests, post-fatigue tension to failure tests, LOP (TEM) observations, and SEM examinations, were performed at room-temperature to investigate the variation of the static mechanical properties, microstructures and fracture behavior of 304 austenitic stainless steel during low-cycle fatigue. The changing characteristics of various static mechanical property parameters, including the strength parameters, stiffness parameter, ductility parameters and strain hardening exponent during fatigue damage process of the stainless steel were obtained experimentally and their micromechanisms were discussed by analyzing both the deformation microstructures and the fracture features of the cyclically pre-deformed specimens. It was shown that the austenite / martensite transformation resulting from the accumulation of cyclic plastic strain was mostly responsible for the variation in the strength, ductility and strain hardening ability of the stainless steel during fatigue damage process. The depletion of the inherent ductility in the material due to fatigue damage evolution led to the ductile-to-brittle transition (DBT) in the fracture modes. Based on the macro- / micro-experiments regarding the exhaustion of the ductility during fatigue damage, the ductility parameter was suggested as a damage indicating parameter for the present stainless steel in further studying the fatigue damage mechanics model as well as the residual fatigue life prediction method.

Characterizing the Influence of Scaffold Anisotropy on Engineered Heart Valve Leaflet Function

2009 ◽  
Author(s):  
David E. Schmidt ◽  
Michael S. Sacks
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Large Deformations ◽  
Pulmonary Valve ◽  
Mechanical Anisotropy ◽  
Prosthetic Valves ◽  
Anisotropic Mechanical Properties ◽  
Cell Sources ◽  
Biaxial Mechanical Properties ◽  
The Impact

Tissue engineered pulmonary valves (TEPV) represent a conceptually appealing alternative to current non-viable prosthetic valves and valved conduits for the repair of congenital or acquired lesions in pediatric patients. In addition to the identification of clinically feasible cell sources, engineered soft tissues such as the TEPV require scaffolds with anisotropic mechanical properties that undergo large deformations (not possible with current PGA/PLLA non-wovens) coupled with controllable biodegradative and cell-adhesive characteristics. Electrospun PEUU (ES-PEUU) scaffolds have been produced with tensile biaxial mechanical properties remarkably similar to the native pulmonary valve (Fig. 1-a), including the ability to undergo large physiologic strains and exhibit pronounced mechanical anisotropy. Moreover, a novel cell micro-integration technique has been developed that allows for successful cell integration directly into the scaffolds at the time of fabrication, eliminating cellular penetration problems. These encouraging results suggest that ES-PEUU scaffolds micro-integrated with the appropriate cells and can serve as successful TEPV scaffolds. In the present study, we conducted a finite element based analysis of TEPV leaflets (Fig. 1-b) under quasi-static transvalvular pressure to demonstrate the impact of ES-PEUU mechanical anisotropy on scaffold strain distributions.

Physical and Mechanical Properties of Chemically Treated Jute Fiber Reinforced MAgPP Green Composites

2016 ◽  
Vol 860 ◽  
pp. 134-139 ◽  
Author(s):  
Sweety Shahinur ◽  
Mahbub Hasan ◽  
Qumrul Ahsan
Keyword(s):  
Mechanical Properties ◽  
Fire Retardant ◽  
Physical And Mechanical Properties ◽  
Fiber Composites ◽  
Jute Fiber ◽  
Green Composites ◽  
Fiber Reinforced ◽  
Pull Out ◽  
Chemically Treated ◽  
The Impact

Natural fibers are biodegradable, non toxic, recyclable, energy efficient and eco-friendly, which reduce the issue of waste disposal as seen in the case of synthetic fibers. Jute is the cheapest lignocellulosic long vegetable bast fiber and abundantly available in South Asia, especially in Bangladesh. It offers a number of benefits as reinforcement in synthetic polymers. In the present study, jute fiber was chemically treated in order to make it fire, rot and water retardant. Jute fiber reinforced green composites were manufactured using preheated chopped jute fiber and maleic anhydrate grafted polypropylene in the hot press machine at a temperature of 180°C and a pressure of 40 kN. Both raw and chemically treated jute fibers at three levels of fiber loading (20, 25 and 30 wt%) were utilized during composite manufacturing. Micro-structural analysis and mechanical testing of the manufactured green composites were subsequently carried out. Chemically treated jute fiber composites showed an improvement in mechanical properties as compared to the maleic anhydrate grafted polypropylene. The impact property was not significantly affected by chemical treatment. At room temperature water uptake increased with fiber weight fraction, while water retardant jute fiber composites absorbed more water as compared to the other composites. The rot retardant treated jute fiber composites had the best set of mechanical properties among all manufactured composites. SEM observation of the fracture surface clearly showed that control and rot retardant jute fiber reinforced green composites had more fiber pull out as compared to fire retardant and water retardant jute fiber reinforced green composites. This indicates better adhesion between the matrix and fiber in case of the fire retardant and water retardant green composites. Chemically treated jute fiber reinforced green composites could be popular as a substitute of plastic in house hold sectors as a moderate load bearing component.

scholarly journals Assessment of Composites using Waste Sugarcane Bagasse Fibre and Wood Dust Powder

2020 ◽  
Vol 9 (5) ◽  
pp. 2126-2131 ◽  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Benzoic Acid ◽  
Sugarcane Bagasse ◽  
Chemical Treatment ◽  
Weight Ratio ◽  
Epoxy Composites ◽  
Wood Dust ◽  
Chemically Treated ◽  
Bagasse Fibre

The present work aims to investigate relating to natural fibre-based epoxy composites. This study is dealt with the fabrication and chemical treatment evaluation of waste sugarcane bagasse fibre and wood dust powder composite. Sugarcane bagasse fibre and wood dust powder found to be good bonding owing to its properties like light-weight, high specific strength, bio-degradability and so on. The sugarcane shells are collected from local juice job and then it is chemically treated along with removal of sugar, and then dried in open atmosphere in the presence of sunlight. It is then pulverized to particle sizes of 1.0 mm, 1.5 mm, 2.0 mm and with a weight ratio of 75:25, the epoxy resins are mixed through which the fibres with 6 mm thick mould composites are made with different flat-shape. As per ASTM standards, specimens are made for conducting the experiments such as density determination, moisture absorption and mechanical tests. The sugarcane bagasse/epoxy composites (SB/EC) with wood dust powder were chemically treated with benzoic acid and sodium hydroxide for obtaining the mechanical properties. The results show that chemically treated composites have more flexural and tensile strength as compared with untreated sugar-free SB/EC. Alkali (NaoH) treatment obtains the highest flexural and tensile strength as compared with benzoic acid treatment. Both flexural and tensile strength of synthetically(chemical) treated composites, in any case, discovered lower than those of untreated sugarcane bagasse filled composite when unwashed sugarcane bagasse which contained sugar. Thus without additional chemical treatment, sugarcane bagasse perhaps used as a reinforcing agent since sugar contributes to the mechanical properties of the composites.

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.    

U.S. Regulatory Approaches: A Critical Appraisal

1992 ◽  
Vol 25 (3) ◽  
pp. 13-21
Author(s):  
R. L. Williamson
Keyword(s):  
Decision Making ◽  
Command And Control ◽  
Regulatory System ◽  
Federal Agencies ◽  
Toxic Substances ◽  
Use Of Technology ◽  
Treatment Technologies ◽  
New Treatment ◽  
And Control ◽  
The Impact

The American approach to environmental regulation is characterized by fragmentation of responsibilities, primary reliance on command and control regulations, extraordinary complexity, a preference for identifiable standards, and heavy resort to litigation. This system has provided important benefits, including significant reduction of environmental contamination, substantial use of science in decision-making, broad participatory rights, and the stimulation of new treatment technologies. However, these gains have been achieved at excessive cost. Too much reliance is placed on command and control methods and especially on technology-based standards. There is too much resort to litigation, and inadequate input from science. Participatory rights are being undermined, and there is a poor allocation of decision-making among the federal agencies and the states. Over-regulation sometimes leads to under-regulation, and insufficient attention is given to the impact on small entities. The responsibility for these difficulties rests with everyone, including the federal agencies, the Congress, the general public and the courts. Changes in the regulatory system are needed. We should abandon the use of technology-based standards to control toxic substances under the Clean Water Act in favor of strong health- and environmentally based standards, coupled with taxes on toxic substances in wastewater.

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