Mechanical Behavior Of Fibers Research Articles

Bulging of inflated membranes made of fiber reinforced materials with different natural configurations

In this article, we study the inflation and bulging of fiber reinforced hyperelastic membranes in which fibers are symmetrically arranged in two helically distributed families that are mechanically equivalent. The isotropic ground substance behavior is described by a neo-Hookean model and the mechanical behavior of fibers is described by the so-called standard reinforcing model. The two constituents, fiber and matrix, may possess different natural configurations to account for different characteristics. For example, in collagenous soft tissue synthesized collagen fibrils are integrated at a certain distribution of pre-stretches, or fibers may be crimped, and different natural configurations of the constituents can be used to model these mechanisms. In addition, fibers are taken to be dispersed with respect to a mean fiber direction within their respective fiber families. It is shown that the arrangement and the natural configuration of fibers have a strong effect on bulging of inflated cylindrical membranes. The modeling at hand can be used to understand the mechanical behaviour of arterial soft tissue and the formation of aneurysms.

Experimental investigation on mechanical behavior of fiber–metal laminates reinforced by hybrid carbon nanotubes and nanosilica under quasi-static pressure load

In this study, the effect of carbon nanotubes (CNT) and silica nanoparticles on quasi-static behavior of fiber–metal laminates (FML) has been experimentally scrutinized. FML consists of two layers of aluminum alloy plates and four composite layers including CNT/nanosilica-reinforced epoxy resin and glass fibers. The effect of weight percentage of carbon nanotube and nanosilica incorporated and their weight ratio in resin epoxy on the performance of FMLs against quasi-static compressive load has been considered. Furthermore, the design of experiments method and response surface methodology have been put into practice to develop an accurate mathematical relationship between the input parameters and the response variable. After designing and performing the experiments based on analysis of variance, a mathematical model corresponding to the real process is obtained. Moreover, the presented model has been validated by statistical methods. The results of this study indicate that the energy absorption capacity of these materials significantly increase through adding CNT to the FML, the highest failure force of 11.64 kN was obtained for FLMs comprising 0.6 wt.% of CNT and 3 wt.% of SiO2. An improvement of 27.88% and 45.86% in the absorbed energy and failure force was achieved, respectively, by adding 3 wt.% of SiO2 and 0.6 wt.% of CNT to FLM compared to pristine FLM.

A deteriorating model for the prediction of elastic modulus of the aging fiber reinforced polymer under complex environmental effects

The fiber reinforced polymer is popularly applied for structural reinforcement and, however, usually suffers from long-term environmental effects, for example exposed to the ultraviolet radiation, alternating changes of moist-heat, and submerged in water chronically. As a result, the material aging and structural performance degradation are inevitable, which could eventually lead to the deterioration of mechanical behavior of fiber reinforced polymer, hence the attenuation or failure of repaired structures. It is very expensive and time consuming to use the experimental method to find out the aging patterns of fiber reinforced polymer. For fiber reinforced polymer with different volume fraction, the upper and lower limit of elastic modulus can be deduced by the energy principle. Combining this theory with tests, a semi-empirical deteriorating method can be used to analyze the change of fiber reinforced polymer mechanics behavior. And a series of empirical coefficients, determined by natural aging tests, are introduced. The coefficients are applied in the revised formula for the prediction of mechanics behaviors of fiber reinforced polymer. The elastic modulus of deteriorating fiber reinforced polymer is influenced by the fiber, the resin matrix, and the volume fraction of the fiber. For different fiber volume fraction, the experimental test is not the unique way to assess the durability of fiber reinforced polymer, as long as the laws of fiber aging, the laws of resin aging, and the fiber volume fraction are already known. The proposed model shows good agreement with the test results, hence can be used to predict the elastic modulus of aging fiber reinforced polymer, which can be utilized as references for engineering design and research in the future.

Mechanical behavior of fibers and films based on PP/Quartz composites

In this work, films and fibers of Polypropylene based composites reinforced with quartz were investigated. The materials were processed in a twin screw extruder with filler contents of 1, 2.5, and 5 wt%. Morphology, thermal properties, and mechanical behavior of these materials were studied. A homogeneous filler dispersion and particle alignment in the extrusion direction was detected for the films. Thermograms displayed a marginal nucleating effect of quartz particles. Uniaxial tensile tests indicated a high ductility level and strain hardening for the composites processed as films (in the extrusion direction). Single fiber tests displayed improved tensile properties compared with the same materials produced as films. Quasi-static fracture tests showed a completely ductile behavior for the films in the extrusion direction. In addition, films fracture toughness was found to increase with filler content. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Experimental Research on Flexural Mechanical Behavior of Fiber Reinforced Concrete Flexural Members

Based on the cross-section bending of 5 carbon fiber concrete beams, the mechanism of deflection and strain of carbon fiber concrete beam were studied considering the variation of the length of carbon fiber and stirrup ratio. The experimental results show that the deflection of destruction increased with the increase of the length of the carbon fiber, and the effect of stirrup ratio on deflection and strain of beams is not obvious. The carbon fiber can effectively improve the brittle failure of concrete beam, and the stain of concrete accorded with that steel bar at the same height. According to the existing test model, the theoretical calculating formula of CFRC was proposed and applied for the cracking load calculation expression of CRFC beams, and theoretical calculated results agree well with experimental results.

Dynamic Mechanical Behavior of Fiber Reinforced Polymer Composites Embedded with ZnO Whiskers

Glass fiber reinforced polymer composites were prepared by dispersing zinc oxide (ZnO) whiskers in resin matrix. Static and dynamic tensile tests of the as-prepared composites were performed by means of a universal testing machine and the split hopkinson tensile bar (SHTB), respectively. Good tensile properties, which can be affected by the strain rates, of the composites are obtained. The fracture section morphology of the composites was investigated by scanning electron microscope (SEM). The different failure of the composites under static and dynamic tension is found. The tensile properties of the composites are dominated by pull-out and fracture of fiber bundles. The influence of ZnO whiskers on the performance of composites has been discussed. ZnO whiskers, which have unique three-dimensional structures and corresponding stress transfer, contribute to the tensile properties of the composites.

Study of Mechanical and Thermomechanical Properties of Jute/Epoxy Composite Laminate

This article presents the development and the characterization of composite material (laminate) containing natural jute fiber reinforcement. Thermal characterization of jute fiber reinforcement shows the influence of the temperature on the mechanical behavior of fiber. At 180°C the jute fabric loses 50% of its mechanical characteristics. The laminate obtained by a process known as infusion is polymerized at a temperature lower than that which affects the mechanical properties of dry fabric. The digital image correlation carried out on laminated jute/epoxy (warp and weft direction) under tensile test shows the presence of a considerable gradient of deformation. This gradient is explained by the variability related to the local voluminal change of jute fibers of one place to the other and the nature of the weaving of the jute fiber. The three-point bending tests show a significant dispersion of rupture stress. The thermomechanical tests carried out on samples in the two principal directions, show that the thermal coefficient of expansion in warp direction is 48% larger compared to the weft direction. The thermogravimetric test shows that this laminate absorbs up to 4% water mass after 8 h in a climatic chamber with 70% moisture content.

T0101-1-4 繊維強化複合材料の力学挙動に及ぼすBLEVEによる損傷の影響に関する研究(複合材料1)

T0101-1-4 繊維強化複合材料の力学挙動に及ぼすBLEVEによる損傷の影響に関する研究(複合材料1)

Fiber structures for the regenerative medicine

Abstract Regenerative medicine is a very promising field of research, which claims to heal damaged tissue instead of replacing it with artificial spare parts. Due to the mechanical behavior of fibers, similar to the fibrous structures most of our body tissues are made of, fibers are very biocompatible and suitable as carrier materials for cells and for the guided regeneration of tissues, mainly if the mechanical load is limited. Three examples demonstrate that for every tissue different properties of textiles and fibers are necessary. In liver regeneration the cell carrier must allow the attachment of the hepatocytes to one another for the formation of aggregates, otherwise the functionality of the cells is low. In cartilage regeneration the main challenge is the optimal degradation properties of the matrix for single cells allowing the unrestricted formation of a new matrix by the cells. In nerve regeneration structured fibers allow a faster outgrowth of new axons.

The size effects on the mechanical behaviour of fibres

The size of a fibre affects its mechanical properties and thus is of theoretical and practical importance for studies of the rupturing process during loading of a fibrous structure. This paper investigates the overall effects of length on the mechanical behaviour of single fibres. Four types of fibres, ranging from brittle to highly extensible, were tested for their tensile properties at several different gauge lengths. Different from most previous studies where the focus has been on the gauge length effects on a single property such as fibre strength or breaking strain, this paper look comprehensively into the effects of length on all three of the most commonly studied mechanical properties, namely strength, breaking strain and initial modulus. Particular emphasis is placed on initial modulus and on the interactions between all three parameters. Influences of strain rate and fibre type on the size effects are also investigated. The effect of potential fibre slippage on experimental error is examined. An image analysis method is used to measure the real fibre elongation in comparison to the same fibre elongation obtained directly from an Instron tester. Finally, a statistical analysis is carried out using the experimental data to test the fitness of the Weibull theory to polymeric fibres. This was done as the Weibull model has been extensively utilized in examining fibre strength and breaking strain, although it is supposed to be valid only for the so-called classic fibres to which more extensible polymeric fibres do not belong.

Mechanical behavior of a fiber reinf orced ceramic composite under off-axis loading

The mechanical behavior and damage mechanisms of a unidirectional fiber reinforced ceramic composite (Corning's Nicalon/CAS III) was investigated under off-axis tensile loading. Specimens with six orientations (0, 15, 30, 45, 60 and 90°) of fibers with respect to loading direction were tested. Acoustic emission and replication techniques were used to monitor the initiation and progression of damage. The 0 and 15° specimens had initiation of matrix cracking during the linear portion of the stress-strain curve. The 30, 45, 60 and 90° specimens had no matrix cracking or nonlinearity in their stress-strain curves before the final failure. The test results showed that the maximum stress and Tsai-Hill failure criteria can be used to predict the failure strength of fiber reinforced ceramic composites under off-axis loading. Also, the present transformation relations for the off-axis Young's modulus and Poisson's ratio are applicable to the fiber reinforced ceramic matrix composite.

Normative Representation of Stress and Strain Applied to Fiber Reinforced Composites

A novel method of contracted notation to represent stress and strain in the form of normative representation has been employed in this article to describe the global mechanical behavior of fiber reinforced composite materials. A unified set of transforma tion equations governing orientational changes in stress and strain as well as that in stiffness and compliance was derived. A coordinate independent stress-strain law, the normal Hooke's law, was presented and several related concepts including the elastic eigenmodulus, elastic mode and modal stress were introduced. Considered also was the decomposition of the elastic strain-energy density mto irreducible, independent energy- orthogonal components which are related with distinct types of energy. Based on the nor mative representation approach and the various unique properties of the normal Hooke's law, a theory of material strength for anisotropic materials was established which encom passes the classical von Mises yield criterion for isotropic materials as its particular case.

Micromechanical Studies of Crack Growth in Steel Fiber Reinforced Mortar

A micromechanical finite element model is developed to simulate the response of a typical region of a fiber reinforced material load from the onset of load to failure. With this model, mechanical behavior of fiber reinforced cementitious materials can be studied, as the magnitide and distribution of the stresses in the matrix material, fibers, and fiber-matrix interface are calculated. With this knowledge, an understanding can be gained of why the composite behaves as it does and this behavior can be improved. There was agreement between the results of testing and micromechanical finite element modeling of the side-cracked tension specimens, Thus the model can be useful in evaluating existing composites or in the developement of new composites.

Macrostructure and mechanical behavior of fibers of poly-p-phenylene benzobisthiazole

Morphology and tensile behavior of wet-spun fibers of poly-p-phenylene benzobisthiazole have been investigated. The as-spun fibers contain a large number of voids, which result in void-localized tensile failure. The stress–strain behavior is elastic–plastic with strain hardening. This behavior is shown to be the result of residual stresses which arise during the wet-spinning process.

The testing of fibres and their molecular structure

In a general survey of fibre physics advancement in the understanding of the mechanical behaviour of fibres is discussed in the light of recent improvements in techniques for determining the molecular structure of fibres. The introduction of some general aspects of molecular structure is followed by detailed descriptions of new methods of measuring molecular orientation in fibres. The results of dynamic methods of measuring glass-rubber transition temperatures are described and related to the molecular orientation and mechanical behaviour of fibres at various temperatures. Elementary molecular models are introduced to explain certain aspects of the mechanical behaviour of fibres.

Mechanical behavior of fibers

This paper is concerned with the phenomenology of visco-elasticity approached by means of differential equations. Three results are given which are new and not generally known to workers in the field.1. The geometrical meaning of 1st order differential equations is given in the context of mechanical behavior of fibers.This frees the researcher of an obligation to interpret his equations in terms of springs and dash pots. 2. Operational methods are given for determining if any 1st order differential equation (linear or not) can provide an adequate description for a particular fiber. 3. For cases where a differential equation is satisfactory an operational method is given for contructing it directly in the laboratory rather than attempting to fit experimental trajectories to solutions of assumed differential equations.

Mechanical Behavior of Fibers

Mechanical Behavior of Fibers

Mechanical Behavior of Fibers

Mechanical Behavior of Fibers

A New Concept of the Mechanical Behavior of Fibers

The first portion, Part I, of this paper presents a review of the various theories of mechanical behavior of fibers. It is shown that the linear three-element model gives a fairly good qualitative description of relaxation, creep, and stress-strain phenomena. With this linear model extended to give a dis tribution of relaxation times, the time scales of the relaxation and creep functions are expanded to ranges which approach those observed experimentally. However, the more compli cated linear model is cumbersome, particularly when used to explain stress-strain data, and it does not yield the proper values of the elastic and viscous constants when the rate of strain is changed by a large factor. The three-element model with Hookean springs and Eyring dashpot is discussed, and it is shown that it accomplishes the extension of the time scale for relaxation and creep, and also yields relationships involving changes in the rate of elongation of stress-strain experiments which agree quite well with data on acetate rayon. The use fulness of graphical methods of analysis of stress-strain curves is pointed out. For other fibers, the agreement with experi ment is not so good. Efforts to generalize the Eyring model by considering the "energy barriers" to be asymmetric, em ployment of non-Hookean springs, and increasing the number of elements in the model have given better agreement of theory with experiment but leave much to be desired in the explana tion of the behavior of wool fibers.