Mechanical Strength Of Fibers Research Articles

Wet-spinnability and crosslinked Fiber properties of alginate/hydroxyethyl cellulose with varied proportion for potential use in tendon tissue engineering

Researchers have examined different bio-inspired materials in tissue engineering and regenerative medicine to fabricate scaffolds to address tendon regeneration requirements. We developed fibers based on alginate (Alg) and hydroxyethyl cellulose (HEC) by wet-spinning technique to mimic the fibrous sheath of ECM. Various proportions (25:75, 50:50, 75:25) of 1 % Alg and 4 % HEC were blended to this aim. Two steps of crosslinking with different concentrations of CaCl2 (2.5 and 5 %) and glutaraldehyde (2.5 %) were used to improve physical and mechanical properties. The fibers were characterized by FTIR, SEM, swelling, degradation, and tensile tests. The in vitro proliferation, viability, and migration of tenocytes on the fibers were also evaluated. Moreover, the biocompatibility of implanted fibers was investigated in an animal model. The results showed ionic and covalent molecular interactions between the components. In addition, by properly maintaining surface morphology, fiber alignment, and swelling, lower concentrations of HEC in the blending provided good degradability and mechanical features. The mechanical strength of fibers was in the range of collagenous fibers. Increasing the crosslinking led to significantly different mechanical behaviors in terms of tensile strength and elongation at break. Because of good in vitro and in vivo biocompatibility, tenocyte proliferation, and migration, the biological macromolecular fibers could serve as desirable tendon substitutes. This study provides more practical insight into tendon tissue engineering in translational medicine.

Kinetics of water sorption in single Sterculia and Bauhinia fibers at ambient temperature

Fundamental study on material properties of lignocellulose fiber is important to understand the performance of composite materials. In this study, we explored several material properties of untreated, commercial and wood ash alkali retted fiber obtained from relatively less studied and traditionally important wild plant species Sterculia villosa (local name Murgilo or Mudilo) and Bauhinia vahlii fibers (local name Bharlo). Water sorption kinetics in all fiber types was measured at ambient temperature. Fickian model then was used to fit experimental sorption kinetic data and information on diffusion coefficients at early and late stages of sorption, average diffusion coefficient, sorption coefficient, and water permeability were obtained. The average diffusion coefficient (D) for untreated, wood ash alkali and commercial alkali treated Sterculia was found to be 10.6 × 10-13 m2/sec, 3.08 × 10-12 m2/sec, and 2.35 × 10-12 m2/sec; respectively. The corresponding values for Bauhinia fiber were found to be 6.8 × 10-13 m2/sec, 3.80 × 10-12 m2/sec, and 3.46 × 10-12 m2/sec; respectively. The equilibrium water sorption in the alkali treated fiber was significantly reduced due to removal of cementing materials and also increase of crystallinity. Significant decrease in mechanical strength of fiber in sorbed state was found. These findings will be useful to understand stability of fiber and potential end products such as paper sheets and reinforced composite materials exposed under different moisture conditions.

Alkalinization and graft copolymerization of pineapple leaf fiber cellulose and evaluation of physic‐chemical properties

Modification in physico‐chemical properties of pineapple leaf fiber (PALF) using NaOH treatment and graft copolymerization technique was investigated in the present study. The free radical graft copolymerization was carried out in presence of redox initiators of ferrous ammonium sulfate (FAS) and potassium persulfate (KPS), using monomers methyl methacrylate (MMA) and butyl acrylate (BA) in water medium. The structural analysis by Fourier transform infrared spectroscopy and scanning electron microscopy images confirmed the successful incorporation of acrylate monomers onto cellulose backbone. The optimum graft percentage (64.3%) was determined at molar concentration ratio of initiators (KPS:FAS) (1:0.5) and acrylate monomers (MMA:BA) (2:1). The poly(acrylates‐g‐PALF) exhibits good thermal stability than ungrafted and treated fiber. Presence of BA increases the grafting percentage up to 60.80% and exhibited inverse behavior on the mechanical properties as well as in crystallinity. It has been observed that specific stress of grafted fibers is lower to that of ungrafted fibers. In this study, the degradation of fibers under UV exposure and in soil environment was investigated and changes in surface morphology and mechanical strength of fibers were studied along with the comparison between fibers before and after degradation. POLYM. COMPOS., 40:1395–1403, 2019. © 2018 Society of Plastics Engineers

Clot properties and cardiovascular disease.

Fibrinogen is cleaved by thrombin to fibrin, which provides the blood clot with its essential structural backbone. As an acute phase protein, the plasma levels of fibrinogen are increased in response to inflammatory conditions. In addition to fibrinogen levels, fibrin clot structure is altered by a number of factors. These include thrombin levels, treatment with common cardiovascular medications, such as aspirin, anticoagulants, statins and fibrates, as well as metabolic disease states such as diabetes mellitus and hyperhomocysteinaemia. In vitro studies of fibrin clot structure can provide information regarding fibre density, clot porosity, the mechanical strength of fibres and fibrinolysis. A change in fibrin clot structure, to a denser clot with smaller pores which is more resistant to lysis, is strongly associated with cardiovascular disease. This pathological change is present in patients with arterial as well as venous diseases, and is also found in a moderate form in relatives of patients with cardiovascular disease. Pharmacological therapies, aimed at both the treatment and prophylaxis of cardiovascular disease, appear to result in positive changes to the fibrin clot structure. As such, therapies aimed at 'normalising' fibrin clot structure may be of benefit in the prevention and treatment of cardiovascular disease.

FUNCTIONALIZED MWCNTS REINFORCED POLYETEHYLENE FIBER COMPOSITE: MECHANICAL STRENGTH CHARACTERIZATION

This article studies about the mechanical strength of different functionalized Carbon nanotubes (CNTs) reinforced Polyethylene (PE) fiber composite fabricated by melt spinning. There are four types of CNTs used, which are called as produced, carboxylated, octadecylated, polymer wrapped CNTs . Influence of mechanical drawing (melt spinning) on the mechanical strength of fibers is measured by direct comparison with mechanical strength of bulk type functionalized CNTs polymer composites, which fabricated using hot press. Dispersion and interfacial bonding strength/adhesion of CNTs with PE matrix are investigated through fracture surfaces image analysis. Functionalized CNTs composites show a significant improvement of mechanical strength of pure polymer than non functionalized CNTs polymer composite. Whereas polymer wrapped CNTs polymer composite give the highest mechanical strength in this study. Mechanical strength of bulk composites are significantly increased after mechanical drawing process indicates that melts spinning may influence on the crystallization of polymer. Fracture surface analysis revealed that additional functionalized CNTs enhanced dispersion and interfacial bonding with polymer matrix.

New method for strength improvement of silica optical fibers

The reliability and the expected lifetime of optical fibers used in telecommunication technologies are closely related to the chemical environment action on the silica network. To ensure the long-term mechanical strength of the optical fibers, a polymer coating was applied onto the fiber surface during fiber fabrication. This external coating is vital to ensure a long optical fiber lifetime. Its protective action includes several functions, such as to protect glass fiber from any external damage, to limit chemical attack, in particular that of water, and finally to ensure fatigue protection and bending insensitivity, especially during handling and in-service installation. Since the mechanical strength of the fiber is controlled by its surface characteristics, we propose a new method for increasing fiber strength. The silica optical fibers used were 125 μm in diameter, with a 62.5 μm thick epoxy-acrylate coating. Fibers were rolled up around two similar cylinders. Using a screw, these cylinders moved away from one another and thus subjected the fibers to stretching. Submitted to this mechanical loading, the distended fibers were plunged into hot water at 65 or 85 °C and aged for several days. Then, the fibers were removed from the water and various weights were suspended on the fiber ends. Thus, the fibers were subjected to a tensile loading in static fatigue for several days. Just before fiber rupture, the fibers were unloaded and subjected to dynamic tensile tests at different velocities. Result analysis proved that the aging in hot water increased the fiber strength. The Weibull's diagram study shows a bimodal dispersion of defects on the fiber surface and the important role of polymer coating.

Generalized stress intensity factors in the interaction between two fibers in matrix

To evaluate the mechanical strength of fiber reinforced composites it is necessary to consider singular stresses at the end of fibers because they cause crack initiation, propagation, and final failure. The singular stress is expressed by generalized stress intensity factors defined at the corner of fibers. As a 2D model an interaction between rectangular inclusions under longitudinal tension is treated in this paper. The body force method is used to formulate the problem as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where the unknown functions are the densities of body forces distributed in infinite plates having the same elastic constants as those of the matrix and inclusions. In order to analyze the problem accurately, the unknown functions are expressed as piecewize smooth functions using two types of fundamental densities and power series, where the fundamental densities are chosen to represent the symmetric stress singularity of 1/r1−λ1 and the skew-symmetric stress singularity of 1/r1−λ2. Then, generalized stress intensity factors at the end of inclusions are systematically calculated for various locations, spacings and elastic modulus of two rectangular inclusions in a plate subjected to longitudinal tension.

Adhesion Between Glass-Fiber and Matrix of Glass-Fiber Reinforced Rigid Polyurethane foam Under Tension

Abstract The theory of the mechanical strength of fiber reinforced composite materials has been elucidated by Cox [1], Kelley [2], Tyson [3], and Hayashi [4] and investigated by many experiments.

42—THE RÔLE OF SURFACTANTS IN REDUCING ACID DAMAGE TO WOOL IN CARBONIZING

Acid damage to wool fibres in carbonizing appears to be largely localized. The addition of certain surfactants at suitable concentrations reduces the degree of localized damage and should increase the mechanical strength of fibres. The concentration of surfactants at which localized damage is least does not necessarily coincide with the concentration required to produce the minimum uptake of moisture or acid or both by wool.