Properties Of Fibrous Materials Research Articles

Bending Natural Frequencies of Circular CFRP Shafts with a Metal Core or Casing

It has recently been shown that some carbon fiber-reinforced composite shafts with a metal core or casing are superior to all carbon fiber reinforced plastics (CFRP) or metal shafts from the viewpoint of the natural frequencies. However, it has not been reported whether or not the benefit of the metal/CFRP hybrid shafts exists in the general cases of various fiber angles, length-to-diameter ratios, material properties, and thicknesses of metal layers. In this study, the effects of a steel core or casing on the bending natural frequencies of CFRP shafts are analytically investigated. In order to calculate the frequencies, the equations of motion are obtained for metal/CFRP hybrid shafts. Several beam theories are evaluated, and differences between these theories in the prediction of the frequencies are also presented. It is found that, in certain cases, an optimum thickness of steel exists to maximize the frequencies of the steel/CFRP shafts. Parametric studies are also carried out over wide ranges of design factors, and design guidelines for the hybrid shafts are finally distilled.

Fluoropolymer Fibres: Physicochemical Nature and Structural Dependence of their Unique Properties, Fabrication, and Use. A Review

Fluorine-containing fibre-forming polymers, fibres, and fibre materials have unique properties due to the presence of fluorine atoms. Totally fluorinated polymer materials are distinguished by the highest resistance to all kinds of chemical reagents and physically active media, low wettability by polar liquids, and other specific functional properties. In examining the physicochemical nature of the unique properties of fluoropolymer fibres and fibre materials with respect to the theory of chemical structure and D. I. Mendeleev's Periodic Table of the Elements, we found that they are due to the features of the fluorine atoms, which have the highest electronegativity of all elements, high ionization energy, high energies of bonds with carbon atoms, and simultaneously shield the molecular chain from external effects. Fibre-forming fluoropolymers, fibres, and fibre materials made from them have high resistance to external effects, biostability and bioinertness, and highly effective protective and other functional characteristics. This relates to the totally fluorinated materials PTFE, HFP, and CP-TFE-HFP to the greatest degree. Fibres and fibre materials based on totally fluorinated polymers (PTFE, HFP, CP-TFE-HFP) are placed in a special group for use in articles utilized in extreme conditions in exposure to especially aggressive media and other external active effects where the use of other kinds of fibres and fibre materials is difficult or impossible because of their low stability and rapid destruction.

Relationship between the Structure and Physical Properties of Fibrous Materials Obtained by Aerodynamic Moulding from a Polymer Solution

Relationship between the Structure and Physical Properties of Fibrous Materials Obtained by Aerodynamic Moulding from a Polymer Solution

Modelling of mechanical properties of wood and wood-based materials

Modelling is a wide concept. This paper describes various meanings of modelling in relation to mechanical properties of wood and wood-based materials. Three examples of modelling by means of the finite element method, presented in recent years in PhD theses, are used as reference points. They relate to modelling of the micro-structure of wood and its mechanical properties, modelling of drying-induced distortion of boards and modelling of the micro-structure and properties of dry-shaped cellulose fibre materials. The paper concludes with remarks on some studies relating to fracture simulations,strength modelling and glued joints.

Mikhail Yulievich Bal'shin: Development of the Scientific Bases of Fiber Metallurgy

The main aspects of theory for preparing materials from original components in a dispersed state that comprise the scientific bases of fiber metallurgy developed by Bal'shin are considered. This relates to ideas about features of the contribution of the flexibility and stiffness of structural elements to volumetric deformation of porous bodies with a fibrous structure; features of the compaction of objects made from fibers with respect to stress governed by fiber resistance to bending (the contact equation of compaction), and development of the elastic aftereffect accompanying this process; fundamental principles of forming a set of physicomechanical properties of porous fiber materials based on ideas about the contact (critical) cross section of a porous body.

Vibration of thermally post-buckled composite plates embedded with shape memory alloy fibers

The vibration behavior of the thermally buckled composite plate embedded with shape memory alloy (SMA) fibers is investigated. The nonlinear finite element equations based on the first-order shear deformation plate theory are formulated for the laminated composite plate embedded with SMA fibers. The von Karman strain–displacement relation is used to account for the large deflection. The incremental method considering the influence of the initial deflections and initial stresses is adopted for the temperature-dependent material properties of SMA fibers and composite matrix. In addition, the marching method is used for determining the thermal large deflections and predicting the critical temperatures. The numerical results show the vibration characteristic of the laminated composite plate embedded with SMA fibers in the pre-buckled and post-buckled regions.

Cement-bonded wood particleboard with a mixture of eucalypt and rubberwood

Abstract Six eucalypts species Eucalyptus camaldulensis Dehnh., E. citriodora Hook, E. cloeziana F. Muell, E. grandis Hill ex. Maiden, E. pilularis Sm., and E. urophylla S. T. Blake) and two clones of rubberwood ( Hevea brasiliensis (Willd ex Adr. de Juss) Muell. Arg.), planted in Brazil, were used to manufacture wood cement-bonded particleboard (CBWP). Boards measuring 450 × 450 × 13 mm were manufactured in a wood/cement/water ratio of 1:4:1, by weight; nominal density of 1.4 g/cm 3 and 4% of additive (CaCl 2 ·H 2 O) using a mixture of each eucalypts species (50%) and the two clones of rubberwood (25% of each). Three replications were fabricated for each treatment and the physical and mechanical properties of the boards evaluated according to ASTM D 1037-96a [Standard test methods for evaluating properties of wood-base fiber and particle panel materials. ASTM D 1037-96a, vol. 04.09. ASTM, 1998]. The results of modulus of elasticity ranged from 4090 to 4771 MPa. The results of modulus of rupture ranged from 5.8 to 6.4 MPa. Internal bond were similar to those found in the literature. Screw withdrawal values were up to 2020 N. The panels showed very good dimensional stability. The mixture of species and also the addition of calcium chloride have improved the physical and mechanical properties of the panels. Decay fungi tests were conducted according to the ASTM D 2017-81 [Standard test method for accelerated laboratory test of natural decay resistance of woods. ASTM D 2017-81, vol. 04.09. ASTM, 1994-e1. p. 324] for two representative wood-attacking fungi, a brown-rot fungus Gloeophyllum trabeum (Persoon ex Fries) Murrill and a white-rot fungus Trametes versicolor (Linnaeus ex Fries) Pilat. Twelve samples were tested and after 12 weeks of exposure the average weight loss was determined. The test indicated that CBWP was classified as “highly resistant” and the samples gained weight.

Computational Simulation of Fracture Behavior Due to Mechanical and Constituent Properties of CFCCs

Continuous fiber reinforced ceramic matrix composites (CFCCs) are recently a subject of a lot of research interest due to advantages which are high specific stiffness and strength, high toughness and nonbrittle failure as compared to monolithic ceramics. The basic purpose of the present study is to describe graphically the fracture behavior of CFCCs according to a dependence on constituent properties. In CFCCs, following matrix cracking, intact fibers bridge effects impose closure tractions behind the crack tip that reduce the driving force for further cracking. Thus matrix cracking stress and bridging stress are important. Then the change of fiber volume fraction is given for the matrix cracking stress by the numerical simulation. Numerical simulation are carried out by using a finite element analysis code ANSYS. The double mesh concept is applied to account for fiber and matrix material properties.

Progressive flexural failure analysis of laminated composites with knitted fabric reinforcement

Prediction of the flexural strength of a laminated composite is important for engineering application yet difficult in nature. The purpose of this paper is to analyse the progressive failure process of laminated composites subjected to a bending load, with application to those reinforced by knitted fabrics. The analysis is based on the classical lamination theory and a bridging micromechanics model [Compos. Part A 32 (2) (2001) 143–172]. Only the mechanical properties of constituent fiber and matrix materials under the bending load condition and the laminate geometric parameters are required. All these data can be measured independently before composite fabrication. As the internal stresses in the fiber and matrix have been explicitly determined using the bridging model, a lamina in the laminate is considered to have failed whenever any of its constituents fails, according to a stress failure criterion. Then, a stiffness discount is applied to the failed lamina, and a predicted progressive failure process results. Unlike in an in-plane load situation where the ultimate tensile strength occurs when the laminate’s last ply fails, the ultimate bending strength of the laminate is attained generally before its last-ply failure. As one does not know a priori which ply failure corresponds to the ultimate failure, the use of only the stress failure criterion is no longer sufficient for the determination of the laminate ultimate strength. An additional critical deflection or curvature condition must be adopted either. The critical deflection or curvature is the laminate deflection or curvature corresponding to which the ultimate bending strength is measured. Experiments have been carried out to obtain the bending stiffness and strength of laminated beams reinforced with six layers of plain weft knitted fabrics under four-point bending. The laminate lay-ups used are: [0/0/0/0/0/0], [90/90/90/90/90/90], [0/90/90/90/90/0], [90/0/0/0/0/90], and [0/45/−45/−45/45/0], where 0 denotes that the fabric wale direction is along the beam axial direction. Using a matrix combustion and fabric peeling out method, it has been found that only some of the layers in the laminates failed after the bending test. For these laminates and based on the stress failure criterion, the predicted load–deflection curves till the fourth-ply failure agree reasonably with the experimental data. By incorporating with the critical deflection condition, the laminate ultimate bending strengths thus obtained correlate favourably with the measured results.

Properties Of Cation-Exchange Polypropylene Fibre Materials

The performance properties of cation-exchange fibre materials made from shaped PP fibres were assessed. The performance properties of CEFM based on shaped PP fibres satisfying the requirements of the standards allow recommending them for use in chemical plant wastewater treatment systems.

On a general constitutive description for the inelastic and failure behavior of fibrous laminates––Part II: Laminate theory and applications

These two parts of papers report systematically a constitutive description for the inelastic and strength behavior of laminated composites reinforced with various fiber preforms. The constitutive relationship is established micromechanically, through layer-by-layer analysis. Namely, only the properties of the constituent fiber and matrix materials of the composites are required as input data. In the previous part (Comput. Struct. (submitted)), the lamina theory was presented. Three fundamental quantities of the laminae, i.e. the internal stresses generated in the constituent fiber and matrix materials and the instantaneous compliance matrix, with different fiber preform (including woven, braided, and knitted fabric) reinforcements were explicitly obtained by virtue of the bridging micromechanics model. In the present paper, the laminate stress analysis is shown. The purpose of this analysis is to determine the load shared by each lamina in the laminate, so that the lamina theory can be applied. Incorporation of the constitutive equations into an FEM software package is illustrated. A number of application examples are given in the paper to demonstrate the efficiency of the constitutive theory established. The predictions thus made include: failure envelopes of multidirectional laminates subjected to biaxial in-plane loads, thermo-mechanical cycling stress–strain curves of a titanium metal matrix composite laminate, S–N curves of multilayer knitted fabric reinforced laminates under tensile fatigue, and bending load–deflection plots and ultimate bending strengths of laminated braided fabric reinforced beams subjected to lateral loads. All these predictions are based on the constituent properties which were measured or available independently, and are compared with experimental results. Reasonably good correlations have been found in all the cases. It is expected that the present constitutive relationship can benefit the critical design and strength analysis of a primarily loaded structure made of composite materials.

Fabrication and Properties of Fibre Materials Containing Biologically Active Protease—Polyethylenimine Complex

Cellulose and polyester fibre materials with a long-lasting biological action are obtained as a result of combined immobilization of a proteolytic enzyme, Tr, Pr, Ter, or Col, and a polymeric antimicrobial of the cationic type — polyethylenimine. A change in the pH profile of the action of the enzymes immobilized in the fibre materials together with polyethylenimine was found. The possibility of sterilizing the materials by irradiation is demonstrated.

Light-Scattering Fibre Materials

Methodology for assessing the structural characteristics of fibre materials using the specific surface area of the fibres instead of their diameter is proposed. Calculated and experimental evaluation of the optical properties of fibre materials was performed on the example of monolithic and fibre samples of a fluoroplastic.

Effect of circumferential edge constraint on the acoustical properties of glass fiber materials

It has been noted that the absorption coefficient of a porous material sample placed in a standing wave tube is affected at low frequencies by the nature of the sample’s edge constraint. The edge constraint has the effect of inhibiting the motion of the solid phase of the material. The latter can be strongly coupled to the material’s fluid phase, and hence the incident sound field, by viscous means at low frequencies. Here the absorption effect noted earlier was demonstrated experimentally. The main focus of the work, however, was on a corresponding transmission loss effect. The material considered was aviation grade glass fiber in two densities. It was found that the edge constraint results in a shearing resonance of the sample at which frequency the transmission loss is a minimum: below that frequency the transmission loss increases with decreasing frequency to a finite low frequency limit proportional to the sample’s flow resistance. It was found that the constraint effect could be modeled by using a poroelastic finite element model. It was also found that the transmission loss of the edge-constrained samples approximated that of unconstrained samples at frequencies above approximately 100 Hz when measured in a 10-cm-diam tube.

Material properties of polymerized NDGA–collagen composite fibers: development of biologically based tendon constructs

Methods for stabilizing collagen-based materials with catechol containing monomers were developed in order to produce fibers with mechanical properties in tension comparable to those of normal tendon. Fibers produced from pepsin solubilized, bovine tendon type I collagen were polymerized with the di-catechol nordihydroguaiaretic acid (NDGA). Polymerization was based on the chemical oxidation of the constituent o-catechols to reactive o-quinone functionalities. NDGA caused a dose dependent increase in the tensile strength and stiffness of the type I collagen fibers. A second treatment with NDGA improved the tensile properties significantly. Comparison of the effects of NDGA with those of biologically relevant mono-catechols indicated that the bi-catechol functionality of NDGA was responsible for generation of the superior tensile properties. Elimination of unreacted intermediates from the treated fibers with ethanol increased the effectiveness of the cross-linking process while simultaneously sterilizing the material. Catalyzing oxidation by saturating the reaction buffer with oxygen increased the effectiveness of polymerization and the resulting tensile properties of the treated fibers. The ultimate tensile strength of the optimized NDGA-treated fibers averaged 90 MPa; the elastic modulus of these fibers averaged 580 MPa. Both values are comparable to native tendon. The material properties of the NDGA cross-linked fibers exceed the properties of collagen fibers treated with other cross-linking strategies such as glutaraldehyde and carbodiimide. These results indicate that NDGA cross-linking may provide a viable approach to stabilizing collagenous materials for use in repair of ruptured, lacerated or surgically transected tendons, as well as other biomaterial constructs for surgical repair of musculoskeletal injuries and disease.

Modeling of the progressive failure behavior of multilayer knitted fabric-reinforced composite laminates

This paper deals with the characterization and modeling of the failure behavior of laminates with application to multilayer plain weft-knitted-fabric-reinforced composites. Experiments have been performed to measure the uniaxial tensile strengths of eight knitted-fabric laminates with lay-ups of [0/0/0/0], [0/+30/−30/0], [0/45/−45/0], [0/+60/−60/0], [0/90/90/0], [+30/−30/−30/+30], [+60/−60/−60/+60], and [90/90/90/90], where 0 refers to the fabric wale direction and 90 to the course direction. A theoretical modeling procedure for the progressive failure process in the laminate is presented. The simulation, made at the lamina ply level, is based on the classical thin-laminate theory and a recently developed bridging micromechanics model. Only material properties of constituent fiber and matrix as well as fabric geometric parameters are necessary. The internal stress increments generated in the fiber and the matrix of each lamina are directly related to the overall applied load increment on the laminate. Whenever any constituent material attains its ultimate stress state, according to the maximum normal stress criterion, the corresponding lamina fails, and a stiffness discount is applied to the remaining laminate. An angle-ply laminate subjected to in-plane biaxial load combinations together with the eight knitted-fabric laminates under uniaxial tension has been analyzed. The predicted ultimate failure strengths or strength envelope of the laminates agree well with our or available experimental data. Furthermore, the influence of different fabric lay-up configurations on the first and the last-ply failure strengths of the knitted-fabric laminates has been investigated, and the failure envelopes of several knitted-fabric laminates subjected to bi-axial loads are also shown in the paper.

Contribution of disc degeneration to osteophyte formation in the cervical spine: a biomechanical investigation.

Cervical spine disorders such as spondylotic radiculopathy and myelopathy are often related to osteophyte formation. Bone remodeling experimental-analytical studies have correlated biomechanical responses such as stress and strain energy density to the formation of bony outgrowth. Using these responses of the spinal components, the present study was conducted to investigate the basis for the occurrence of disc-related pathological conditions. An anatomically accurate and validated intact finite element model of the C4-C5-C6 cervical spine was used to simulate progressive disc degeneration at the C5-C6 level. Slight degeneration included an alteration of material properties of the nucleus pulposus representing the dehydration process. Moderate degeneration included an alteration of fiber content and material properties of the anulus fibrosus representing the disintegrated nature of the anulus in addition to dehydrated nucleus. Severe degeneration included decrease in the intervertebral disc height with dehydrated nucleus and disintegrated anulus. The intact and three degenerated models were exercised under compression, and the overall force-displacement response, local segmental stiffness, anulus fiber strain, disc bulge, anulus stress, load shared by the disc and facet joints, pressure in the disc, facet and uncovertebral joints, and strain energy density and stress in the vertebral cortex were determined. The overall stiffness (C4-C6) increased with the severity of degeneration. The segmental stiffness at the degenerated level (C5-C6) increased with the severity of degeneration. Intervertebral disc bulge and anulus stress and strain decreased at the degenerated level. The strain energy density and stress in vertebral cortex increased adjacent to the degenerated disc. Specifically, the anterior region of the cortex responded with a higher increase in these responses. The increased strain energy density and stress in the vertebral cortex over time may induce the remodeling process according to Wolff's law, leading to the formation of osteophytes.

Effect of processing on electrical resistivity of textile fibers

Most test methods used to evaluate the electrostatic properties of textile materials are based, in one way or another, on the measurement of electrical resistance. Many and various methods have been devised to measure electrical resistance of textile assemblies and a diversity of parameters are used to define it. Generally speaking, it is very difficult to match results of different methods. In this paper we use, for measuring electrical resistivity of textile assemblies, a multiple-step method, which takes compressional properties of the assembly into consideration and defines a new parameter to describe electrical resistivity of textile assemblies. The new definition used for the resistivity of the textile assembly is similar to the volume resistivity of a rigid homogeneous material, being so an inherent characteristic reflecting electrical properties of fiber material, independent of sample form (fabric, yarn, fiber), dimensions of measuring cell and amount of the sample. This method made possible, for the first time, a measurement of the evolution of electrical resistivity of cotton and wool fibers during the spinning process. The results enabled the evolution of electrostatic properties of fibers to be determined as the they passed from one processing machine to the other. Thus, the intensity of processing and need for treatment with antistatic lubricants could be assessed.

Relationship of Structure and Physical Properties of Fibre Materials

The degree of the effect of structural parameters on the physical and operational properties of fibre materials was estimated. The determining effect of the thickness of the material on the air permeability and sound-absorbing coefficient, thickness, and porosity on the heat resistance, and fibre diameter on the change in the filtering and sorption properties of porous walls was established.

リブ付き短繊維混合補強土のせん断強度特性

Short fiber-reinforced earth construction methods in which non-continuous geosynthetic filaments are mixed uniformly with soil aggregates are being developed recently for the purposes of improving the mechanical properties of shear strength and strain-dependent toughness of the reinforced soils. In addition this method has some beneficial functions in wide-range environmental applications such as the re-use of poor surplus soils produced in the construction sites and stabilizing the steep slopes providing the vegetation base. At present insufficient knowledge is available regarding to effects of material, shape, size, flexibility, surface fiction and other fundamental properties of short fiber on the mechanical behavior. A newly developed short fibers with several side branches (so called ribbed-type fiber) is employed in order to not only improve their reinforcement effects but also to be able to exclude the fibers without great effort in case of reuse of the soils. In this study effects of the mixing rate of the fibers on the reinforcing mechanism are investigated using an unconfined compression test and a large box shear test (box size: 320×400×240mm).