Properties Of Fibrous Materials Research Articles

Parameters controlling the strength of stochastic fibrous materials

Many materials of everyday use are fibrous and their strength is important in most applications. In this work we study the dependence of the strength of random fiber networks on structural parameters such as the network density, cross-link density, fiber tortuosity, and the strength of the inter-fiber cross-links. Athermal networks of cellular and fibrous type are considered. We conclude that the network strength scales linearly with the cross-link number density and with the cross-link strength for a broad range of network parameters, and for both types of networks considered. Network strength is independent of fiber material properties and of fiber tortuosity. This information can be used to design fiber networks for specified strength and, generally, to understand the mechanical behavior of fibrous materials.

Effect of Temperature on Material Properties of Carbon Fiber Reinforced Polymer (CFRP) Tendons: Experiments and Model Assessment.

Material properties at elevated temperatures are important factors in the fire safety design and numerical analysis of concrete members strengthened with fiber reinforced polymer (FRP) composites. Most of the previous research mainly focused on tensile strength and elastic modulus in conventional steady state temperature tests. However, the transient state test method is more realistic for strengthening concrete structures. At the same time, the coefficient of thermal expansion of FRP composites is also one of the important factors affecting concrete members at elevated temperatures. This paper presents a detailed experimental investigation on the longitudinal thermal expansion deformation, and the mechanical properties of carbon FRP (CFRP) tendons with 8 mm diameter in the steady state and transient state. The results indicate that longitudinal deformation of CFRP tendons is negative at high temperature; in addition, the transient state test results of CFRP tendons are slightly higher than the steady state test results. The final part of this paper assesses the accuracy of different empirical models. Furthermore, a new equation calculating the properties of CFRP composites at elevated temperatures is presented with the numerical fitting technique, which is in good agreement with the experimental results.

Representative Volume Element Homogenization of a Composite Material by Using Bond-Based Peridynamics

This study presents representative volume element (RVE) homogenization by using bond-based peridynamics. First, a method to perform RVE homogenisation analysis with bond-based peridynamic theory is demonstrated. Homogenized material properties of a unit-sized fibre reinforced composite cell with varying fibre volume fraction are predicted using the present method. Peridynamic results are compared against a finite element based RVE approach and a good agreement is observed between the two approaches.

Tensile properties of CFRP manufactured by resin transfer molding considering stacking sequences at various strain rates

This paper is concerned with the improvement of a tensile test method and the material properties of carbon fiber reinforced polymer manufactured by resin transfer molding considering stacking sequences at various strain rates for auto-body. Auto-body structure experiences the strain rates up to several hundreds per second during car crash. In order to apply the carbon fiber reinforced polymer panel into auto-body structures, it is critical to acquire the material properties of carbon fiber reinforced polymer at various strain rates considering stacking sequences. The tensile test method is improved for acceptable test results. Test specimens are modified for high-speed tensile tests of carbon fiber reinforced polymer in order to achieve designated strain rates and eliminate the effect from unfavorable conditions of inhomogeneity of deformation. Various types of grip tab materials are employed for acceptable failure modes. Tensile tests have been carried out with non-crimp fabric made by 50K high strength carbon fiber (NCF) and woven fabric made by a 2/2 twill pattern of 3K high strength carbon fiber (TWILL) with different stacking sequences of 0° and 90° unidirectional cases as well as [0°/90°] and [45°/−45°] symmetric cases. Digital image correlation method and force equilibrium grid method are adopted for strain and stress measurement of a carbon fiber reinforced polymer specimen during a tensile test. The material properties acquired indicate that the carbon fiber has little rate dependency, while the epoxy matrix has remarkable rate hardening at strain rates from 0.001 s−1 to 100 s−1.

Evaluation of a novel test method for the determination of strain rate-dependent material properties of high-performance fibers

For reinforcement in fiber reinforced plastic and concrete applications, the knowledge of the high-velocity impact and crash behavior of typically used high-performance fibers, such as carbon fibers (CF), becomes an important aspect for designing and dimensioning new composite components. More important than the impact velocity is the resulting strain rate in the fiber, which defines the failure behavior. In current literature, there is still an open gap for fiber material testing for strain rates between 100 and 1000 1/s, which is difficult to close with the existing measurement setups, i.e. between servo-hydraulic tensile testing machines and Split-Hopkinson-tension-bars. A rotary drive principle is proposed where the challenge arises in coupling the force, in a reliable clamping of the specimens and in high-speed acquisition of the stress-strain curve. In the implementation process, speeds up to 40 m/s were currently achieved, which corresponds to a strain rate of 267 s-1 for a specimen length of 150 mm. The specimen and the moving elements were prepared with stochastic patterns and evaluated by means of digital image correlation (DIC). The force signal is recorded and correlated from a piezoelectric load cell. Additional information on the energy dissipated by the tensile test was acquired by analyzing the engine control records. The evaluation of high-speed images by DIC shows that there is a partially elastic impact and acceleration reaches its maxima before the specimen’s rupture. Thus, for a precise evaluation, the stress equilibrium has to be taken into account and the impact process has to be further optimized.

Modification of Polyurethane Solutions by Means of a Hard Depositor for Fibre Production by the Electrospinning Method

The article is devoted to fundamental and applied research in the field of the processing of polymer solutions. The purpose of this work was to identify the possibility of using modified solutions of polyurethanes for processing by electrospinning, and also to study the impact of the composition of the moulding solution on the structure and properties of fibrous materials. Nonwoven materials were obtained by electrospinning fibers from PUR solutions using NanospiderTM technology. The transfer of solutions into a metastable state, both in the case of film systems and fibres, leads to a change in the structure of the material: porosity and fiber diameter.

A new approach to reinforce the fiber of nanocomposite reinforced by CNTs to analyze free vibration of hybrid laminated cylindrical shell using beam modal function method

This research deals with a study of the free vibration of fiber metal laminate thin circular cylindrical shell reinforced by single walled carbon nanotubes with different boundary conditions. The representative volume element is consisting of four phases: fiber, carbon nanotubes (CNTs), polymer matrix and metal. Initially, the CNTs have been added to the matrix and then the fiber phase has been reinforced by them. Finally, the adhesive fiber prepreg has been combined with the thin metal layers. The generated cylindrical shell can be named CNT/fiber/polymer/metal laminate (CNTFPML) cylindrical shell. In this study, Love's first approximation shell theory has been used to obtain the strain-displacement relations and also, beam modal function model has been utilized to satisfy the governing equations of motion. The effects of mass fraction of CNTs, volume fraction of fiber and metal, axial and circumferential modal numbers, and different distributions of CNTs subjected to different boundary conditions on the vibration of the shell have been considered. In addition, the influences of different lay-ups and different material properties of fiber have been investigated.

A 3D computational model of electrospun networks and its application to inform a reduced modelling approach

In this contribution, a full 3D finite element model of electrospun networks is presented. The model explicitly accounts for the specific microstructure of these networks by generating representative volume elements through a particular fibre deposition method inspired by the process of network formation during electrospinning. The modelled fibre material and structural properties, such as different fibre shapes and distributions in diameter, can vary over a wide range, and mutual fibre contact is considered in addition to permanent cross-links. In addition to the homogenized mechanical response to macroscopic in-plane loads, the model provides access to structural information which can hardly be determined in experiments, such as fibre disposition and interconnectivity. In the present work, this asset is used to inform a recent 2.5D modelling approach (Zündel et al., 2017) and to validate inherent assumptions on network structure. The comparison between the responses of the two approaches reveals that for networks of high porosity, the reduced 2.5D model captures well the mechanical behaviour in plane stress load cases. At lower porosities though, the increasing out-of-plane orientation of fibre segments leads to effects that cannot be captured by planar approaches and necessitate a 3D approach.

Opto-Electron Eng, 2018, 45(9)] Hollow-core photonic bandgap fibers: properties and sensing technology

In this paper, the unique properties of the hollow-core photonic bandgap fiber (HC-PBF) are reviewed, and a variety of sensing and device applications of this type of fiber in recent years are introduced. Low-loss light transmission in air core is an important characteristic of the HC-PBF, which provides light-matter interaction channel with high energy density and long interaction distance. In addition, the air-propagation of the light in fiber also reduces the impacts of fiber material properties (such as infrared absorption, thermos-optical effect) on propagating light, hence offers an efficient platform for the sensing applications such as trace gas / liquid detection, optical fiber gyro sensing. The fine micro-structure in HC-PBF exhibits novel mechanical and thermal properties, which would be beneficial to the sensing applications such as sound wave and vibration detection. The HC-PBF’s porous structure can also be locally modified by using various post-processing techniques, such as local heat treatment, micromachining and selective filling, which would enable further function extension or performance enhancement. The flexibility of the fiber has been used to develop new optical fiber devices, such as grating, polarizer and polarization interferometer. At present, the development of HC-PBF sensing technology has greatly expanded the sensing ability and application range of optical fiber. It is an important direction for the development of all-optical devices and optical integration technology.

A three-dimensional micromechanical model of brain white matter with histology-informed probabilistic distribution of axonal fibers

This paper presents a three-dimensional micromechanical model of brain white matter tissue as a transversely isotropic soft composite described by the generalized Ogden hyperelastic model. The embedded element technique, with corrected stiffness redundancy in large deformations, was used for the embedment of a histology-informed probabilistic distribution of the axonal fibers in the extracellular matrix. The model was linked to a multi-objective, multi-parametric optimization algorithm, using the response surface methodology, for characterization of material properties of the axonal fibers and extracellular matrix in an inverse finite element analysis. The optimum hyperelastic characteristics of the tissue constituents, obtained based on the axonal and transverse direction test results of the corona radiata tissue samples, indicated that the axonal fibers were almost thirteen times stiffer than the extracellular matrix under large deformations. Simulation of the same tissue under a different loading condition, as well as that of another white matter tissue, i.e., the corpus callosum, in the axonal and transverse directions, using the optimized hyperelastic characteristics revealed tissue responses very close to those of the experiments. The results of the model at the sub-tissue level indicated that the stress concentrations were considerably large around the small axons, which might contribute into the brain injury.

Electrospun one-dimensional nanostructures: a new horizon for gas sensing materials.

Electrospun one-dimensional (1D) nanostructures are rapidly emerging as key enabling components in gas sensing due to their unique electrical, optical, magnetic, thermal, mechanical and chemical properties. 1D nanostructures have found applications in numerous areas, including healthcare, energy storage, biotechnology, environmental monitoring, and defence/security. Their enhanced specific surface area, superior mechanical properties, nanoporosity and improved surface characteristics (in particular, uniformity and stability) have made them important active materials for gas sensing applications. Such highly sensitive and selective elements can be embedded in sensor nodes for internet-of-things applications or in mobile systems for continuous monitoring of air pollutants and greenhouse gases as well as for monitoring the well-being and health in everyday life. Herein, we review recent developments of gas sensors based on electrospun 1D nanostructures in different sensing platforms, including optical, conductometric and acoustic resonators. After explaining the principle of electrospinning, we classify sensors based on the type of materials used as an active sensing layer, including polymers, metal oxide semiconductors, graphene, and their composites or their functionalized forms. The material properties of these electrospun fibers and their sensing performance toward different analytes are explained in detail and correlated to the benefits and limitations for every approach.

Investigation on structural behavior of ring-stiffened composite offshore rubber hose under internal pressure

Ring-stiffened composite offshore rubber hose of single carcass is commonly used for offshore oil transfer. Common hose dimensions are length of 10.7 m and nominal diameter of 500 mm. The nominal burst pressure is 7.5 MPa, equal to five times rated working pressure of 1.5 MPa. The hose carcass is composite cylindrical tube made of rubber, reinforcing fiber cords and steel spiral stiffener that provides radial stiffness. In hose design, the burst pressure shall be determined to verify its pressure bearing capacity. In this paper, a nonlinear finite element hose model is created with commercial software ABAQUS and validated to predict its structural behavior under internal pressure. The large deformations, interactions between components and nonlinear material properties of hyperelastic rubber and fibers are considered. Stresses of stiffener, radial and axial deformation and load in reinforcement plies are obtained. A bulging phenomenon amid two stiffeners is found, which indicates the confine effect of stiffeners. Failure pressure is jointly determined by the strength limit of polymer cords and steel stiffener. The influence of different fibers and rubbers on hose pressure-deformation response are compared. The results demonstrate good accordance with requirement of specification. The finite element model can predict hose failure pressure and provide guidance for reliable hose design in practice.

An energy based approach for reliability analysis of delamination growth under mode I, mode II and mixed mode I/II loading in composite laminates

Since there are many uncertainty sources in composite laminates such as fiber and matrix material properties, reliability analysis of laminates under specific loading modes has been of significant importance in many applications. This paper represents a method for reliability analysis of E-Glass/Epoxy composite laminates in the presence of the most common and catastrophic failure mode in macro-scale, i.e. delamination under mode I, mode II, and mixed mode I/II using an energy based approach for the first time. Limit state functions for the reliability analysis of delamination growth under mode I, mode II, and mixed mode I/II loading are formulated based on energy release rate along with the interlaminar fracture toughness in each of the mentioned modes. Having random variables and limit state functions determined based on energy, the reliability assessment is carried out using first order reliability method (FORM) and second order reliability method (SORM) and the obtained results are verified by Monte Carlo Simulation (MCS). Finally, the effects of different modes of delamination including mode I, mode II, and mixed mode I/II on the reliability of delamination growth in composite laminates are obtained. It is indicated that the reliability of E-Glass/Epoxy composite laminates in mode I delamination has its lowest value, while in mode II has the highest. Amongst the considered random variables in mode I, mode II, and mixed mode I/II, thickness of the laminate is the most effective one in the reliability of mentioned composite laminates under different delamination modes.

Heat transfer modelling of CFRP strengthened and insulated steel tubular columns

The lack of knowledge of the fire performance of CFRP strengthened and insulated steel tubular columns has hindered the CFRP usage in steel columns, which require certain structural fire ratings. In this research, a numerical modelling approach was used to investigate the heat transfer behaviour of CFRP strengthened and insulated steel columns, and thus to enhance the knowledge of their fire performance characteristics. For this purpose, an experimental investigation was also conducted to determine the thermal properties of carbon fibre, adhesive, CFRP and insulation materials at elevated temperatures. These thermal properties were idealized and used to develop heat transfer finite element models in ABAQUS/CAE to simulate the behaviour of CFRP strengthened and insulated steel columns exposed to fire. The developed models were validated by using experimental results and a parametric study was then conducted to investigate the influence of insulation thickness on the heat transfer behaviour. This paper presents the details of this research and the results. It provides the details of the validated heat transfer finite element models and the important thermal properties of CFRP and insulation materials. An approach to determine the fire resistance level of CFRP strengthened and insulated columns is also presented in this paper.

Material properties of sponge-gourd fiber–reinforced polylactic acid biocomposites: Effect of fiber weight ratio, chemical treatment, and treatment concentrations

Sponge-gourd fibers (SGFs) were subjected to chemical treatments such as alkalization, acetylation, and benzoylation by 5−15 wt% sodium hydroxide, acetic anhydride, and benzoyl chloride solutions, respectively, in order to improve fiber–matrix adhesion. SGF-reinforced polylactic acid (PLA) biocomposites were fabricated using melt compounding technique. Both untreated and chemically treated fiber-reinforced composites were subsequently characterized by using a field emission scanning electron microscope, a Fourier-transform infrared spectrometer, an X-ray diffractometer, a universal testing machine, and a thermogravimetric analyzer. Structural analyses show that the chemical treatment improves the crystallinity of SGF and exhibits chemical bond formation in the SGF-reinforced PLA composites. Surface morphology indicates that after the treatment of fibers and increase in the treated fiber content, the interfacial adhesion between PLA and fibers is improved. The effects of fiber loading of chemically treated SGF on physical and mechanical properties of the composites were analyzed. Compressive strength of the composites was increased by 10–35% with incorporation of treated fibers into the PLA matrix. The thermal stability of them is found to increase significantly. Soil burial test has confirmed that the composites are biodegradable. Benzoylation of SGF shows superior mechanical properties and enhances thermal stability among the composites.

Effect of work of adhesion on deep bed filtration process

PurposeThe purpose of this work was to study the influence of particles and fiber material properties on the deposition efficiency. Collection of aerosol particles in the particular steps of their production, and purification of the air at the workplace and the atmospheric environment requires the efficient method of separation of particulate matter from the carrier gas. There are many papers published in the past years in which the deposition of particles on fibrous collectors is considered. Most of them assume that collisions between particles and collector surfaces are 100% effective.Design/methodology/approachFor the purpose of this work, the lattice Boltzmann model was used to describe fluid dynamics, whereas the solid particles motion was modeled by the Brownian dynamics. The interactions between particles and surfaces were modeled using an energy-balanced oscillatory model.FindingsThe results show significant impact of material properties on filter performance.Practical implicationsObtained results may provide useful information for the proper design of a filtration process and the production of filters with long service life.Originality/valueIn addition, the results presented in this work show that some assumptions of the classical filtration theory lead to an overestimation of deposition efficiency.

Material Properties of Synthetic Fiber–Reinforced Concrete under Freeze-Thaw Conditions

AbstractFor decades, synthetic fibers have been utilized to improve the performance of concrete structures by enhancing the flexural strength, modulus of elasticity, and other mechanical properties...

An in silico framework to analyze the anisotropic shear wave mechanics in cardiac shear wave elastography

Shear wave elastography (SWE) is a potential tool to non-invasively assess cardiac muscle stiffness. This study focused on the effect of the orthotropic material properties and mechanical loading on the performance of cardiac SWE, as it is known that these factors contribute to complex 3D anisotropic shear wave propagation. To investigate the specific impact of these complexities, we constructed a finite element model with an orthotropic material law subjected to different uniaxial stretches to simulate SWE in the stressed cardiac wall. Group and phase speed were analyzed in function of tissue thickness and virtual probe rotation angle. Tissue stretching increased the group and phase speed of the simulated shear wave, especially in the direction of the muscle fiber. As the model provided access to the true fiber orientation and material properties, we assessed the accuracy of two fiber orientation extraction methods based on SWE. We found a higher accuracy (but lower robustness) when extracting fiber orientations based on the location of maximal shear wave speed instead of the angle of the major axis of the ellipsoidal group speed surface. Both methods had a comparable performance for the center region of the cardiac wall, and performed less well towards the edges. Lastly, we also assessed the (theoretical) impact of pathology on shear wave physics and characterization in the model. It was found that SWE was able to detect changes in fiber orientation and material characteristics, potentially associated with cardiac pathologies such as myocardial fibrosis. Furthermore, the model showed clearly altered shear wave patterns for the fibrotic myocardium compared to the healthy myocardium, which forms an initial but promising outcome of this modeling study.

Aspects of the Transit of a Narrow Beam of Infrared Radiation Through a Fibrous Material

The article is devoted to the use of optical methods in the study of the properties of fibrous materials. Based on the results of an analytic investigation of the transit of a narrow beam of infrared radiation through a fibrous material we are able to determine the optimal location from the point of view of the maximum sensitivity of the source and detector of the radiation of an optoelectronic transducer where an optical sensor is used in the control system. The relationships and practical calculations obtained make it possible to quantitatively estimate the values of the propagation of radiant energy, and this may serve as a basis for structural and energy calculations of the parameters of an infrared optoelectronic transducer.

The effect of delignification on the properties of cellulosic fiber material

Abstract The behavior of pressed poplar chemi-thermomechanical pulping (CTMP) without additive the focus of our study. Four CTMPs with decreasing lignin contents were prepared by the sodium chlorite/acetic acid method and the holocellulose, α-cellulose, pentosan and Klason lignin contents of the delignified CTMPs were determined. The surface composition, aggregation structure and microstructure of the delignified fibers were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM), and the mechanical properties of the fiber material were investigated by means of tensile and bending tests. As shown by XPS, the lignin content of the Pr-CTMP surface layer firstly increased and then decreased as the lignin content of CTMP decreased. With the delignification time increased from 0 to 240 min, the crystallinity index (C r I) of CTMP increased from 60.1% to 65.7%. The C r I of all CTMPs at different delignification degrees showed significant elevated values after hot-pressing. The fiber cell wall became thinner and the cells were flattened and thus elevated the contact area among fibers and, as a consequence, the density of material gradually increased at higher delignification degrees. The tensile strength increased by ca. 10%, when the lignin content decreased from 24.9% to 13.1%, and by ca. 53%, when the lignin content decreased from 13.1% to nearly zero. The bending strength increased with increasing delignification. When the removal rate of lignin increased from 47% to 54%, the bending strength increased from 101 to 122 MPa.